<?xml version="1.0" encoding="US-ASCII"?>
<!-- RR Donnelley Xcelerate Taxonomy Definition Linkbase, based on XBRL 2.1  http://www.rrdonnelley.com/ -->
<!-- Version: 6.21.0 -->
<!-- Round: 5 -->
<!-- Creation date: 2014-03-14T18:46:08Z -->
<!-- Copyright (c) 2005-2013 R.R. Donnelley &amp; Sons Company All Rights Reserved. -->
<linkbase xmlns="http://www.xbrl.org/2003/linkbase"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xmlns:xlink="http://www.w3.org/1999/xlink"
  xmlns:xbrldt="http://xbrl.org/2005/xbrldt"
  xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#DocumentandEntityInformation" roleURI="http://vicorpower.com/taxonomy/role/DocumentandEntityInformation"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#Role_StatementOfFinancialPositionClassified" roleURI="http://vicorpower.com/taxonomy/role/StatementOfFinancialPositionClassified"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#Role_StatementOfFinancialPositionClassifiedParen" roleURI="http://vicorpower.com/taxonomy/role/StatementOfFinancialPositionClassifiedParenthetical"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#Role_StatementOfIncome" roleURI="http://vicorpower.com/taxonomy/role/StatementOfIncome"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#Role_StatementOfOtherComprehensiveIncome" roleURI="http://vicorpower.com/taxonomy/role/StatementOfOtherComprehensiveIncome"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#Role_StatementOfOtherComprehensiveIncomeParen" roleURI="http://vicorpower.com/taxonomy/role/StatementOfOtherComprehensiveIncomeParenthetical"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#Role_StatementOfCashFlowsIndirect" roleURI="http://vicorpower.com/taxonomy/role/StatementOfCashFlowsIndirect"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#Role_StatementOfShareholdersEquityAndOtherComprehensiveIncome" roleURI="http://vicorpower.com/taxonomy/role/StatementOfShareholdersEquityAndOtherComprehensiveIncome"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#DisclosureSignificantAccountingPoliciesAdditionalInformation" roleURI="http://vicorpower.com/taxonomy/role/DisclosureSignificantAccountingPoliciesAdditionalInformation"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#DisclosureSignificantAccountingPoliciesComputationOfBasicAndDilutedIncomeLossPerShare" roleURI="http://vicorpower.com/taxonomy/role/DisclosureSignificantAccountingPoliciesComputationOfBasicAndDilutedIncomeLossPerShare"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#DisclosureSignificantAccountingPoliciesComputationOfBasicAndDilutedIncomeLossPerShareParenthetical" roleURI="http://vicorpower.com/taxonomy/role/DisclosureSignificantAccountingPoliciesComputationOfBasicAndDilutedIncomeLossPerShareParenthetical"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#DisclosureStockBasedCompensationAndEmployeeBenefitPlansAdditionalInformation" roleURI="http://vicorpower.com/taxonomy/role/DisclosureStockBasedCompensationAndEmployeeBenefitPlansAdditionalInformation"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#DisclosureStockBasedCompensationAndEmployeeBenefitPlansStockBasedCompensationExpense" roleURI="http://vicorpower.com/taxonomy/role/DisclosureStockBasedCompensationAndEmployeeBenefitPlansStockBasedCompensationExpense"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#DisclosureStockBasedCompensationAndEmployeeBenefitPlansWeightedAverageAssumptionsForFairValueForStockOptions" roleURI="http://vicorpower.com/taxonomy/role/DisclosureStockBasedCompensationAndEmployeeBenefitPlansWeightedAverageAssumptionsForFairValueForStockOptions"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#DisclosureStockBasedCompensationAndEmployeeBenefitPlansSummaryOfTheActivityUnderTheVicorStockOptionPlans" roleURI="http://vicorpower.com/taxonomy/role/DisclosureStockBasedCompensationAndEmployeeBenefitPlansSummaryOfTheActivityUnderTheVicorStockOptionPlans"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#DisclosureStockBasedCompensationAndEmployeeBenefitPlansSummaryOfTheActivityUnderThePicorStockOptionPlans" roleURI="http://vicorpower.com/taxonomy/role/DisclosureStockBasedCompensationAndEmployeeBenefitPlansSummaryOfTheActivityUnderThePicorStockOptionPlans"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#DisclosureStockBasedCompensationAndEmployeeBenefitPlansSummaryOfTheActivityUnderTheVIChipStockOptionPlans" roleURI="http://vicorpower.com/taxonomy/role/DisclosureStockBasedCompensationAndEmployeeBenefitPlansSummaryOfTheActivityUnderTheVIChipStockOptionPlans"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#DisclosureStockBasedCompensationAndEmployeeBenefitPlansSummaryOfTheActivityUnderTheVIChipStockOptionPlansParenthetical" roleURI="http://vicorpower.com/taxonomy/role/DisclosureStockBasedCompensationAndEmployeeBenefitPlansSummaryOfTheActivityUnderTheVIChipStockOptionPlansParenthetical"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#DisclosureShortTermAndLongTermInvestmentsAdditionalInformation" roleURI="http://vicorpower.com/taxonomy/role/DisclosureShortTermAndLongTermInvestmentsAdditionalInformation"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#DisclosureShortTermAndLongTermInvestmentsSummaryOfAvailableforSaleSecurities" roleURI="http://vicorpower.com/taxonomy/role/DisclosureShortTermAndLongTermInvestmentsSummaryOfAvailableforSaleSecurities"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#DisclosureShortTermAndLongTermInvestmentsAmortizedCostAndEstimatedFairValueOfAvailableforSaleSecurities" roleURI="http://vicorpower.com/taxonomy/role/DisclosureShortTermAndLongTermInvestmentsAmortizedCostAndEstimatedFairValueOfAvailableforSaleSecurities"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#DisclosureShortTermAndLongTermInvestmentsRollForwardOfCreditLossRecognizedInEarningsOnAvailableforSaleAuctionRateSecurities" roleURI="http://vicorpower.com/taxonomy/role/DisclosureShortTermAndLongTermInvestmentsRollForwardOfCreditLossRecognizedInEarningsOnAvailableforSaleAuctionRateSecurities"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#DisclosureFairValueMeasurementsAssetsMeasuredAtFairValueOnRecurringBasis" roleURI="http://vicorpower.com/taxonomy/role/DisclosureFairValueMeasurementsAssetsMeasuredAtFairValueOnRecurringBasis"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#DisclosureFairValueMeasurementsAdditionalInformation" roleURI="http://vicorpower.com/taxonomy/role/DisclosureFairValueMeasurementsAdditionalInformation"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#DisclosureFairValueMeasurementsQuantitativeInformationAboutLevel3FairValueMeasurements" roleURI="http://vicorpower.com/taxonomy/role/DisclosureFairValueMeasurementsQuantitativeInformationAboutLevel3FairValueMeasurements"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#DisclosureFairValueMeasurementsChangeInEstimatedFairValuesForAssetsValuedOnRecurringBasisUtilizingLevel3Inputs" roleURI="http://vicorpower.com/taxonomy/role/DisclosureFairValueMeasurementsChangeInEstimatedFairValuesForAssetsValuedOnRecurringBasisUtilizingLevel3Inputs"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#DisclosureInventoriesSummaryOfInventories" roleURI="http://vicorpower.com/taxonomy/role/DisclosureInventoriesSummaryOfInventories"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#DisclosurePropertyPlantAndEquipmentAdditionalInformation" roleURI="http://vicorpower.com/taxonomy/role/DisclosurePropertyPlantAndEquipmentAdditionalInformation"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#DisclosurePropertyPlantAndEquipmentPropertyPlantAndEquipment" roleURI="http://vicorpower.com/taxonomy/role/DisclosurePropertyPlantAndEquipmentPropertyPlantAndEquipment"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#DisclosureOtherInvestmentsAdditionalInformation" roleURI="http://vicorpower.com/taxonomy/role/DisclosureOtherInvestmentsAdditionalInformation"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#DisclosureGoodwillAndOtherIntangibleAssetsAdditionalInformation" roleURI="http://vicorpower.com/taxonomy/role/DisclosureGoodwillAndOtherIntangibleAssetsAdditionalInformation"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#DisclosureGoodwillAndOtherIntangibleAssetsScheduleOfPatentCostAndOtherAsset" roleURI="http://vicorpower.com/taxonomy/role/DisclosureGoodwillAndOtherIntangibleAssetsScheduleOfPatentCostAndOtherAsset"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#DisclosureSeveranceChargesAdditionalInformation" roleURI="http://vicorpower.com/taxonomy/role/DisclosureSeveranceChargesAdditionalInformation"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#DisclosureSeveranceChargesASummaryOfActivityRelatedToSeveranceCharges" roleURI="http://vicorpower.com/taxonomy/role/DisclosureSeveranceChargesASummaryOfActivityRelatedToSeveranceCharges"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#DisclosureProductWarrantiesProductWarrantyActivity" roleURI="http://vicorpower.com/taxonomy/role/DisclosureProductWarrantiesProductWarrantyActivity"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#DisclosureStockholdersEquityAdditionalInformation" roleURI="http://vicorpower.com/taxonomy/role/DisclosureStockholdersEquityAdditionalInformation"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#DisclosureOtherIncomeNetComponentsOfOtherIncome" roleURI="http://vicorpower.com/taxonomy/role/DisclosureOtherIncomeNetComponentsOfOtherIncome"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#DisclosureIncomeTaxesScheduleOfReconciliationOfFederalStatutoryRateToEffectiveIncomeTaxRate" roleURI="http://vicorpower.com/taxonomy/role/DisclosureIncomeTaxesScheduleOfReconciliationOfFederalStatutoryRateToEffectiveIncomeTaxRate"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#DisclosureIncomeTaxesAdditionalInformation" roleURI="http://vicorpower.com/taxonomy/role/DisclosureIncomeTaxesAdditionalInformation"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#DisclosureIncomeTaxesScheduleOfDomesticAndForeignComponentsOfIncomeLossBeforeIncomeTaxes" roleURI="http://vicorpower.com/taxonomy/role/DisclosureIncomeTaxesScheduleOfDomesticAndForeignComponentsOfIncomeLossBeforeIncomeTaxes"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#DisclosureIncomeTaxesScheduleOfComponentsOfProvisionBenefitForIncomeTaxes" roleURI="http://vicorpower.com/taxonomy/role/DisclosureIncomeTaxesScheduleOfComponentsOfProvisionBenefitForIncomeTaxes"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#DisclosureIncomeTaxesScheduleOfSignificantComponentsOfDeferredTaxAssetsAndLiabilities" roleURI="http://vicorpower.com/taxonomy/role/DisclosureIncomeTaxesScheduleOfSignificantComponentsOfDeferredTaxAssetsAndLiabilities"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#DisclosureIncomeTaxesScheduleOfReconciliationOfBeginningAndEndingAmountOfUnrecognizedTaxBenefits" roleURI="http://vicorpower.com/taxonomy/role/DisclosureIncomeTaxesScheduleOfReconciliationOfBeginningAndEndingAmountOfUnrecognizedTaxBenefits"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#DisclosureCommitmentsAndContingenciesSummaryOfFutureMinimumRentalCommitmentsUnderNonCancelableOperatingLeases" roleURI="http://vicorpower.com/taxonomy/role/DisclosureCommitmentsAndContingenciesSummaryOfFutureMinimumRentalCommitmentsUnderNonCancelableOperatingLeases"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#DisclosureCommitmentsAndContingenciesAdditionalInformation" roleURI="http://vicorpower.com/taxonomy/role/DisclosureCommitmentsAndContingenciesAdditionalInformation"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#DisclosureSegmentInformationAdditionalInformation" roleURI="http://vicorpower.com/taxonomy/role/DisclosureSegmentInformationAdditionalInformation"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#DisclosureSegmentInformationSignificantSegmentFinancialData" roleURI="http://vicorpower.com/taxonomy/role/DisclosureSegmentInformationSignificantSegmentFinancialData"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#DisclosureQuarterlyResultsOfOperationsUnauditedSummaryOfUnauditedQuarterlyFinancialData" roleURI="http://vicorpower.com/taxonomy/role/DisclosureQuarterlyResultsOfOperationsUnauditedSummaryOfUnauditedQuarterlyFinancialData"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#DisclosureQuarterlyResultsOfOperationsUnauditedAdditionalInformation" roleURI="http://vicorpower.com/taxonomy/role/DisclosureQuarterlyResultsOfOperationsUnauditedAdditionalInformation"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#DisclosureScheduleIIValuationAndQualifyingAccounts" roleURI="http://vicorpower.com/taxonomy/role/DisclosureScheduleIIValuationAndQualifyingAccounts"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#Role_NotesToFinancialStatementsOrganizationConsolidationAndPresentationOfFinancialStatementsDisclosureTextBlock" roleURI="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsOrganizationConsolidationAndPresentationOfFinancialStatementsDisclosureTextBlock"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#Role_NotesToFinancialStatementsSignificantAccountingPoliciesTextBlock" roleURI="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsSignificantAccountingPoliciesTextBlock"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#Role_NotesToFinancialStatementsSignificantAccountingPoliciesTextBlockPolicies" roleURI="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsSignificantAccountingPoliciesTextBlockPolicies"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#Role_NotesToFinancialStatementsSignificantAccountingPoliciesTextBlockTables" roleURI="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsSignificantAccountingPoliciesTextBlockTables"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#Role_NotesToFinancialStatementsDisclosureOfCompensationRelatedCostsShareBasedPaymentsTextBlock" roleURI="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfCompensationRelatedCostsShareBasedPaymentsTextBlock"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#Role_NotesToFinancialStatementsDisclosureOfCompensationRelatedCostsShareBasedPaymentsTextBlockTables" roleURI="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfCompensationRelatedCostsShareBasedPaymentsTextBlockTables"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#Role_NotesToFinancialStatementsInvestmentsInDebtAndMarketableEquitySecuritiesAndCertainTradingAssetsDisclosureTextBlock" roleURI="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsInvestmentsInDebtAndMarketableEquitySecuritiesAndCertainTradingAssetsDisclosureTextBlock"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#Role_NotesToFinancialStatementsInvestmentsInDebtAndMarketableEquitySecuritiesAndCertainTradingAssetsDisclosureTextBlockTables" roleURI="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsInvestmentsInDebtAndMarketableEquitySecuritiesAndCertainTradingAssetsDisclosureTextBlockTables"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#Role_NotesToFinancialStatementsFairValueDisclosuresTextBlock" roleURI="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsFairValueDisclosuresTextBlock"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#Role_NotesToFinancialStatementsFairValueDisclosuresTextBlockTables" roleURI="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsFairValueDisclosuresTextBlockTables"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#Role_NotesToFinancialStatementsInventoryDisclosureTextBlock" roleURI="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsInventoryDisclosureTextBlock"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#Role_NotesToFinancialStatementsInventoryDisclosureTextBlockTables" roleURI="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsInventoryDisclosureTextBlockTables"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#Role_NotesToFinancialStatementsPropertyPlantAndEquipmentDisclosureTextBlock" roleURI="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsPropertyPlantAndEquipmentDisclosureTextBlock"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#Role_NotesToFinancialStatementsPropertyPlantAndEquipmentDisclosureTextBlockTables" roleURI="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsPropertyPlantAndEquipmentDisclosureTextBlockTables"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#Role_NotesToFinancialStatementsOtherInvestmentsTextBlock" roleURI="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsOtherInvestmentsTextBlock"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#Role_NotesToFinancialStatementsGoodwillAndIntangibleAssetsDisclosureTextBlock" roleURI="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsGoodwillAndIntangibleAssetsDisclosureTextBlock"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#Role_NotesToFinancialStatementsGoodwillAndIntangibleAssetsDisclosureTextBlockTables" roleURI="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsGoodwillAndIntangibleAssetsDisclosureTextBlockTables"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#Role_NotesToFinancialStatementsRestructuringAndRelatedActivitiesDisclosureTextBlock" roleURI="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsRestructuringAndRelatedActivitiesDisclosureTextBlock"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#Role_NotesToFinancialStatementsRestructuringAndRelatedActivitiesDisclosureTextBlockTables" roleURI="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsRestructuringAndRelatedActivitiesDisclosureTextBlockTables"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#Role_NotesToFinancialStatementsProductWarrantyDisclosureTextBlock" roleURI="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsProductWarrantyDisclosureTextBlock"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#Role_NotesToFinancialStatementsProductWarrantyDisclosureTextBlockTables" roleURI="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsProductWarrantyDisclosureTextBlockTables"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#Role_NotesToFinancialStatementsStockholdersEquityNoteDisclosureTextBlock" roleURI="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsStockholdersEquityNoteDisclosureTextBlock"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#Role_NotesToFinancialStatementsOtherIncomeAndOtherExpenseDisclosureTextBlock" roleURI="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsOtherIncomeAndOtherExpenseDisclosureTextBlock"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#Role_NotesToFinancialStatementsOtherIncomeAndOtherExpenseDisclosureTextBlockTables" roleURI="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsOtherIncomeAndOtherExpenseDisclosureTextBlockTables"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#Role_NotesToFinancialStatementsIncomeTaxDisclosureTextBlock" roleURI="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsIncomeTaxDisclosureTextBlock"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#Role_NotesToFinancialStatementsIncomeTaxDisclosureTextBlockTables" roleURI="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsIncomeTaxDisclosureTextBlockTables"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#Role_NotesToFinancialStatementsCommitmentsAndContingenciesDisclosureTextBlock" roleURI="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsCommitmentsAndContingenciesDisclosureTextBlock"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#Role_NotesToFinancialStatementsCommitmentsAndContingenciesDisclosureTextBlockTables" roleURI="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsCommitmentsAndContingenciesDisclosureTextBlockTables"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#Role_NotesToFinancialStatementsSegmentReportingDisclosureTextBlock" roleURI="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsSegmentReportingDisclosureTextBlock"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#Role_NotesToFinancialStatementsSegmentReportingDisclosureTextBlockTables" roleURI="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsSegmentReportingDisclosureTextBlockTables"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#Role_NotesToFinancialStatementsQuarterlyFinancialInformationTextBlock" roleURI="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsQuarterlyFinancialInformationTextBlock"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#Role_NotesToFinancialStatementsQuarterlyFinancialInformationTextBlockTables" roleURI="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsQuarterlyFinancialInformationTextBlockTables"/>
  <roleRef xlink:type="simple" xlink:href="vicr-20131231.xsd#Role_NotesToFinancialStatementsScheduleOfValuationAndQualifyingAccountsDisclosureTextBlock" roleURI="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsScheduleOfValuationAndQualifyingAccountsDisclosureTextBlock"/>
  <arcroleRef xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all" arcroleURI="http://xbrl.org/int/dim/arcrole/all"/>
  <arcroleRef xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default" arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default"/>
  <arcroleRef xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain" arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain"/>
  <arcroleRef xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member" arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member"/>
  <arcroleRef xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension" arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension"/>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/DocumentandEntityInformation">
    <loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2013/dei-2013-01-31.xsd#dei_AmendmentFlag" xlink:label="dei_AmendmentFlag"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:label="us-gaap_ClassOfStockDomain"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_CommonClassBMember" xlink:label="us-gaap_CommonClassBMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2013/dei-2013-01-31.xsd#dei_CurrentFiscalYearEndDate" xlink:label="dei_CurrentFiscalYearEndDate"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2013/dei-2013-01-31.xsd#dei_DocumentFiscalPeriodFocus" xlink:label="dei_DocumentFiscalPeriodFocus"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2013/dei-2013-01-31.xsd#dei_DocumentFiscalYearFocus" xlink:label="dei_DocumentFiscalYearFocus"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2013/dei-2013-01-31.xsd#dei_DocumentInformationLineItems" xlink:label="dei_DocumentInformationLineItems"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2013/dei-2013-01-31.xsd#dei_DocumentPeriodEndDate" xlink:label="dei_DocumentPeriodEndDate"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2013/dei-2013-01-31.xsd#dei_DocumentType" xlink:label="dei_DocumentType"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2013/dei-2013-01-31.xsd#dei_EntitiesTable" xlink:label="dei_EntitiesTable"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2013/dei-2013-01-31.xsd#dei_EntityCentralIndexKey" xlink:label="dei_EntityCentralIndexKey"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2013/dei-2013-01-31.xsd#dei_EntityCommonStockSharesOutstanding" xlink:label="dei_EntityCommonStockSharesOutstanding"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2013/dei-2013-01-31.xsd#dei_EntityCurrentReportingStatus" xlink:label="dei_EntityCurrentReportingStatus"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2013/dei-2013-01-31.xsd#dei_EntityFilerCategory" xlink:label="dei_EntityFilerCategory"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2013/dei-2013-01-31.xsd#dei_EntityPublicFloat" xlink:label="dei_EntityPublicFloat"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2013/dei-2013-01-31.xsd#dei_EntityRegistrantName" xlink:label="dei_EntityRegistrantName"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2013/dei-2013-01-31.xsd#dei_EntityVoluntaryFilers" xlink:label="dei_EntityVoluntaryFilers"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2013/dei-2013-01-31.xsd#dei_EntityWellKnownSeasonedIssuer" xlink:label="dei_EntityWellKnownSeasonedIssuer"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StatementClassOfStockAxis" xlink:label="us-gaap_StatementClassOfStockAxis"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ClassOfStockDomain" xlink:to="us-gaap_CommonClassBMember" order="1.1500" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_EntitiesTable" order="100.0000" xbrldt:closed="true" xbrldt:contextElement="segment" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_DocumentType" order="1.0100" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_AmendmentFlag" order="1.0200" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_DocumentPeriodEndDate" order="1.0300" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_DocumentFiscalYearFocus" order="1.0400" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_DocumentFiscalPeriodFocus" order="1.0500" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_EntityRegistrantName" order="1.0600" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_EntityCentralIndexKey" order="1.0700" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_CurrentFiscalYearEndDate" order="1.0800" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_EntityWellKnownSeasonedIssuer" order="1.0900" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_EntityCurrentReportingStatus" order="1.1000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_EntityVoluntaryFilers" order="1.1100" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_EntityFilerCategory" order="1.1200" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_EntityCommonStockSharesOutstanding" order="1.1300" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_EntityPublicFloat" order="1.1400" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="dei_EntitiesTable" xlink:to="us-gaap_StatementClassOfStockAxis" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_StatementClassOfStockAxis" xlink:to="us-gaap_ClassOfStockDomain" order="1.0000" priority="2" use="optional"/>
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/StatementOfFinancialPositionClassified">
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AccountsPayableCurrent" xlink:label="us-gaap_AccountsPayableCurrent"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AccountsReceivableNetCurrent" xlink:label="us-gaap_AccountsReceivableNetCurrent"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AccruedIncomeTaxesCurrent" xlink:label="us-gaap_AccruedIncomeTaxesCurrent"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AccruedIncomeTaxesNoncurrent" xlink:label="us-gaap_AccruedIncomeTaxesNoncurrent"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AccruedLiabilitiesCurrent" xlink:label="us-gaap_AccruedLiabilitiesCurrent"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax" xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AdditionalPaidInCapitalCommonStock" xlink:label="us-gaap_AdditionalPaidInCapitalCommonStock"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_Assets" xlink:label="us-gaap_Assets"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AssetsAbstract" xlink:label="us-gaap_AssetsAbstract"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AssetsCurrent" xlink:label="us-gaap_AssetsCurrent"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AssetsCurrentAbstract" xlink:label="us-gaap_AssetsCurrentAbstract"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:label="us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:label="us-gaap_ClassOfStockDomain"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_CommitmentsAndContingencies" xlink:label="us-gaap_CommitmentsAndContingencies"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_CommonClassBMember" xlink:label="us-gaap_CommonClassBMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_CommonStockValue" xlink:label="us-gaap_CommonStockValue"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_DeferredIncomeTaxesAndOtherLiabilitiesNoncurrent" xlink:label="us-gaap_DeferredIncomeTaxesAndOtherLiabilitiesNoncurrent"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_DeferredRevenueCurrent" xlink:label="us-gaap_DeferredRevenueCurrent"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_DeferredRevenueNoncurrent" xlink:label="us-gaap_DeferredRevenueNoncurrent"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_DeferredTaxAssetsNetCurrent" xlink:label="us-gaap_DeferredTaxAssetsNetCurrent"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_DeferredTaxAssetsNetNoncurrent" xlink:label="us-gaap_DeferredTaxAssetsNetNoncurrent"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_EmployeeRelatedLiabilitiesCurrent" xlink:label="us-gaap_EmployeeRelatedLiabilitiesCurrent"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_InventoryNet" xlink:label="us-gaap_InventoryNet"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_Liabilities" xlink:label="us-gaap_Liabilities"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_LiabilitiesAndStockholdersEquity" xlink:label="us-gaap_LiabilitiesAndStockholdersEquity"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_LiabilitiesAndStockholdersEquityAbstract" xlink:label="us-gaap_LiabilitiesAndStockholdersEquityAbstract"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_LiabilitiesCurrent" xlink:label="us-gaap_LiabilitiesCurrent"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_LiabilitiesCurrentAbstract" xlink:label="us-gaap_LiabilitiesCurrentAbstract"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_MarketableSecuritiesNoncurrent" xlink:label="us-gaap_MarketableSecuritiesNoncurrent"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_MinorityInterest" xlink:label="us-gaap_MinorityInterest"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_OtherAssetsCurrent" xlink:label="us-gaap_OtherAssetsCurrent"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_OtherAssetsNoncurrent" xlink:label="us-gaap_OtherAssetsNoncurrent"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_PreferredStockValue" xlink:label="us-gaap_PreferredStockValue"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_PropertyPlantAndEquipmentNet" xlink:label="us-gaap_PropertyPlantAndEquipmentNet"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_RestructuringReserveCurrent" xlink:label="us-gaap_RestructuringReserveCurrent"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_RetainedEarningsAccumulatedDeficit" xlink:label="us-gaap_RetainedEarningsAccumulatedDeficit"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShortTermInvestments" xlink:label="us-gaap_ShortTermInvestments"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StatementClassOfStockAxis" xlink:label="us-gaap_StatementClassOfStockAxis"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StatementLineItems" xlink:label="us-gaap_StatementLineItems"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StatementTable" xlink:label="us-gaap_StatementTable"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StockholdersEquity" xlink:label="us-gaap_StockholdersEquity"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StockholdersEquityAbstract" xlink:label="us-gaap_StockholdersEquityAbstract"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest" xlink:label="us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract" xlink:label="us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_TreasuryStockValue" xlink:label="us-gaap_TreasuryStockValue"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AssetsAbstract" xlink:to="us-gaap_AssetsCurrentAbstract" order="1.3600" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AssetsAbstract" xlink:to="us-gaap_MarketableSecuritiesNoncurrent" order="1.3700" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AssetsAbstract" xlink:to="us-gaap_PropertyPlantAndEquipmentNet" order="1.3800" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AssetsAbstract" xlink:to="us-gaap_DeferredTaxAssetsNetNoncurrent" order="1.3900" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AssetsAbstract" xlink:to="us-gaap_OtherAssetsNoncurrent" order="1.4000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AssetsAbstract" xlink:to="us-gaap_Assets" order="1.4100" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AssetsCurrentAbstract" xlink:to="us-gaap_CashAndCashEquivalentsAtCarryingValue" order="1.2000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AssetsCurrentAbstract" xlink:to="us-gaap_ShortTermInvestments" order="1.2100" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AssetsCurrentAbstract" xlink:to="us-gaap_AccountsReceivableNetCurrent" order="1.2200" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AssetsCurrentAbstract" xlink:to="us-gaap_InventoryNet" order="1.2300" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AssetsCurrentAbstract" xlink:to="us-gaap_DeferredTaxAssetsNetCurrent" order="1.2400" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AssetsCurrentAbstract" xlink:to="us-gaap_OtherAssetsCurrent" order="1.2500" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AssetsCurrentAbstract" xlink:to="us-gaap_AssetsCurrent" order="1.2600" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ClassOfStockDomain" xlink:to="us-gaap_CommonClassBMember" order="1.3500" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_LiabilitiesAndStockholdersEquityAbstract" xlink:to="us-gaap_LiabilitiesCurrentAbstract" order="1.2700" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_LiabilitiesAndStockholdersEquityAbstract" xlink:to="us-gaap_DeferredRevenueNoncurrent" order="1.2800" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_LiabilitiesAndStockholdersEquityAbstract" xlink:to="us-gaap_AccruedIncomeTaxesNoncurrent" order="1.2900" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_LiabilitiesAndStockholdersEquityAbstract" xlink:to="us-gaap_DeferredIncomeTaxesAndOtherLiabilitiesNoncurrent" order="1.3000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_LiabilitiesAndStockholdersEquityAbstract" xlink:to="us-gaap_Liabilities" order="1.3100" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_LiabilitiesAndStockholdersEquityAbstract" xlink:to="us-gaap_CommitmentsAndContingencies" order="1.3200" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_LiabilitiesAndStockholdersEquityAbstract" xlink:to="us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract" order="1.3300" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_LiabilitiesAndStockholdersEquityAbstract" xlink:to="us-gaap_LiabilitiesAndStockholdersEquity" order="1.3400" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_LiabilitiesCurrentAbstract" xlink:to="us-gaap_AccountsPayableCurrent" order="1.0400" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_LiabilitiesCurrentAbstract" xlink:to="us-gaap_EmployeeRelatedLiabilitiesCurrent" order="1.0500" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_LiabilitiesCurrentAbstract" xlink:to="us-gaap_AccruedLiabilitiesCurrent" order="1.0600" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_LiabilitiesCurrentAbstract" xlink:to="us-gaap_RestructuringReserveCurrent" order="1.0700" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_LiabilitiesCurrentAbstract" xlink:to="us-gaap_AccruedIncomeTaxesCurrent" order="1.0800" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_LiabilitiesCurrentAbstract" xlink:to="us-gaap_DeferredRevenueCurrent" order="1.0900" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_LiabilitiesCurrentAbstract" xlink:to="us-gaap_LiabilitiesCurrent" order="1.1000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_StatementClassOfStockAxis" xlink:to="us-gaap_ClassOfStockDomain" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StatementTable" order="100.0000" xbrldt:closed="true" xbrldt:contextElement="segment" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_AssetsAbstract" order="1.1100" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_LiabilitiesAndStockholdersEquityAbstract" order="1.1200" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_StatementClassOfStockAxis" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StockholdersEquityAbstract" xlink:to="us-gaap_PreferredStockValue" order="1.1300" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StockholdersEquityAbstract" xlink:to="us-gaap_CommonStockValue" order="1.1400" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StockholdersEquityAbstract" xlink:to="us-gaap_AdditionalPaidInCapitalCommonStock" order="1.1500" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StockholdersEquityAbstract" xlink:to="us-gaap_RetainedEarningsAccumulatedDeficit" order="1.1600" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StockholdersEquityAbstract" xlink:to="us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax" order="1.1700" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StockholdersEquityAbstract" xlink:to="us-gaap_TreasuryStockValue" order="1.1800" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StockholdersEquityAbstract" xlink:to="us-gaap_StockholdersEquity" order="1.1900" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract" xlink:to="us-gaap_StockholdersEquityAbstract" order="1.0100" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract" xlink:to="us-gaap_MinorityInterest" order="1.0200" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract" xlink:to="us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest" order="1.0300" priority="2" use="optional"/>
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/StatementOfFinancialPositionClassifiedParenthetical">
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent" xlink:label="us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:label="us-gaap_ClassOfStockDomain"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:label="us-gaap_ClassOfStockDomain_2"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_CommonClassBMember" xlink:label="us-gaap_CommonClassBMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_CommonStockParOrStatedValuePerShare" xlink:label="us-gaap_CommonStockParOrStatedValuePerShare"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_CommonStockSharesAuthorized" xlink:label="us-gaap_CommonStockSharesAuthorized"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_CommonStockSharesIssued" xlink:label="us-gaap_CommonStockSharesIssued"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_CommonStockSharesOutstanding" xlink:label="us-gaap_CommonStockSharesOutstanding"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_CommonStockVotesPerShare" xlink:label="vicr_CommonStockVotesPerShare"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_PreferredStockParOrStatedValuePerShare" xlink:label="us-gaap_PreferredStockParOrStatedValuePerShare"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_PreferredStockSharesAuthorized" xlink:label="us-gaap_PreferredStockSharesAuthorized"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_PreferredStockSharesIssued" xlink:label="us-gaap_PreferredStockSharesIssued"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StatementClassOfStockAxis" xlink:label="us-gaap_StatementClassOfStockAxis"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StatementLineItems" xlink:label="us-gaap_StatementLineItems"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StatementTable" xlink:label="us-gaap_StatementTable"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_TreasuryStockShares" xlink:label="us-gaap_TreasuryStockShares"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ClassOfStockDomain" xlink:to="us-gaap_CommonClassBMember" order="1.1100" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_StatementClassOfStockAxis" xlink:to="us-gaap_ClassOfStockDomain" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_StatementClassOfStockAxis" xlink:to="us-gaap_ClassOfStockDomain_2" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StatementTable" order="100.0000" xbrldt:closed="true" xbrldt:contextElement="segment" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent" order="1.0100" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_PreferredStockParOrStatedValuePerShare" order="1.0200" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_PreferredStockSharesAuthorized" order="1.0300" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_PreferredStockSharesIssued" order="1.0400" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="vicr_CommonStockVotesPerShare" order="1.0500" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_CommonStockParOrStatedValuePerShare" order="1.0600" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_CommonStockSharesAuthorized" order="1.0700" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_CommonStockSharesIssued" order="1.0800" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_CommonStockSharesOutstanding" order="1.0900" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_TreasuryStockShares" order="1.1000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_StatementClassOfStockAxis" order="1.0000" priority="2" use="optional"/>
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/StatementOfIncome">
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/StatementOfOtherComprehensiveIncome">
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/StatementOfOtherComprehensiveIncomeParenthetical">
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/StatementOfCashFlowsIndirect">
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/StatementOfShareholdersEquityAndOtherComprehensiveIncome">
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember" xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AdditionalPaidInCapitalMember" xlink:label="us-gaap_AdditionalPaidInCapitalMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalIncomeTaxDeficiencyFromShareBasedCompensation" xlink:label="us-gaap_AdjustmentsToAdditionalPaidInCapitalIncomeTaxDeficiencyFromShareBasedCompensation"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue" xlink:label="us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationStockOptionsRequisiteServicePeriodRecognition" xlink:label="us-gaap_AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationStockOptionsRequisiteServicePeriodRecognition"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalTaxEffectFromShareBasedCompensation" xlink:label="us-gaap_AdjustmentsToAdditionalPaidInCapitalTaxEffectFromShareBasedCompensation"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:label="us-gaap_ClassOfStockDomain"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_CommonClassBMember" xlink:label="us-gaap_CommonClassBMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_CommonStockMember" xlink:label="us-gaap_CommonStockMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest" xlink:label="us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterestAbstract" xlink:label="us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterestAbstract"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_DividendsCommonStockCash" xlink:label="us-gaap_DividendsCommonStockCash"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="us-gaap_EquityComponentDomain"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="us-gaap_EquityComponentDomain_2"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_LiabilityStockOptionAwardsReclassifiedToEquity" xlink:label="vicr_LiabilityStockOptionAwardsReclassifiedToEquity"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders" xlink:label="us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_NoncontrollingInterestMember" xlink:label="us-gaap_NoncontrollingInterestMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax" xlink:label="us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ParentMember" xlink:label="us-gaap_ParentMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ProfitLoss" xlink:label="us-gaap_ProfitLoss"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_RetainedEarningsMember" xlink:label="us-gaap_RetainedEarningsMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StatementClassOfStockAxis" xlink:label="us-gaap_StatementClassOfStockAxis"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="us-gaap_StatementEquityComponentsAxis"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StatementLineItems" xlink:label="us-gaap_StatementLineItems"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StatementTable" xlink:label="us-gaap_StatementTable"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest" xlink:label="us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueNewIssues" xlink:label="us-gaap_StockIssuedDuringPeriodValueNewIssues"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_TreasuryStockMember" xlink:label="us-gaap_TreasuryStockMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_TreasuryStockValueAcquiredCostMethod" xlink:label="us-gaap_TreasuryStockValueAcquiredCostMethod"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ClassOfStockDomain" xlink:to="us-gaap_CommonClassBMember" order="1.1900" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ClassOfStockDomain" xlink:to="us-gaap_CommonStockMember" order="1.2000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterestAbstract" xlink:to="us-gaap_ProfitLoss" order="1.2100" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterestAbstract" xlink:to="us-gaap_OtherComprehensiveIncomeLossNetOfTax" order="1.2200" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterestAbstract" xlink:to="us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest" order="1.2300" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquityComponentDomain" xlink:to="us-gaap_AdditionalPaidInCapitalMember" order="1.1300" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquityComponentDomain" xlink:to="us-gaap_RetainedEarningsMember" order="1.1400" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquityComponentDomain" xlink:to="us-gaap_AccumulatedOtherComprehensiveIncomeMember" order="1.1500" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquityComponentDomain" xlink:to="us-gaap_TreasuryStockMember" order="1.1600" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquityComponentDomain" xlink:to="us-gaap_ParentMember" order="1.1700" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquityComponentDomain" xlink:to="us-gaap_NoncontrollingInterestMember" order="1.1800" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_StatementClassOfStockAxis" xlink:to="us-gaap_ClassOfStockDomain" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_StatementEquityComponentsAxis" xlink:to="us-gaap_EquityComponentDomain" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_StatementEquityComponentsAxis" xlink:to="us-gaap_EquityComponentDomain_2" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StatementTable" order="100.0000" xbrldt:closed="true" xbrldt:contextElement="segment" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest" order="1.0100" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StockIssuedDuringPeriodValueNewIssues" order="1.0200" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_DividendsCommonStockCash" order="1.0300" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders" order="1.0400" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_AdjustmentsToAdditionalPaidInCapitalTaxEffectFromShareBasedCompensation" order="1.0500" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_AdjustmentsToAdditionalPaidInCapitalIncomeTaxDeficiencyFromShareBasedCompensation" order="1.0600" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue" order="1.0700" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="vicr_LiabilityStockOptionAwardsReclassifiedToEquity" order="1.0800" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationStockOptionsRequisiteServicePeriodRecognition" order="1.0900" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_TreasuryStockValueAcquiredCostMethod" order="1.1000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterestAbstract" order="1.1100" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_StatementClassOfStockAxis" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_StatementEquityComponentsAxis" order="2.0000" priority="2" use="optional"/>
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/DisclosureSignificantAccountingPoliciesAdditionalInformation">
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AdvertisingExpense" xlink:label="us-gaap_AdvertisingExpense"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AuctionRateSecuritiesNoncurrent" xlink:label="us-gaap_AuctionRateSecuritiesNoncurrent"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_CashAndCashEquivalentsMaturityPeriods" xlink:label="vicr_CashAndCashEquivalentsMaturityPeriods"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/country/2013/country-2013-01-31.xsd#country_CN" xlink:label="country_CN"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ConcentrationRiskBenchmarkDomain" xlink:label="us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ConcentrationRiskBenchmarkDomain" xlink:label="us-gaap_ConcentrationRiskBenchmarkDomain_2"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis" xlink:label="us-gaap_ConcentrationRiskByBenchmarkAxis"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ConcentrationRiskByTypeAxis" xlink:label="us-gaap_ConcentrationRiskByTypeAxis"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ConcentrationRiskPercentage1" xlink:label="us-gaap_ConcentrationRiskPercentage1"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ConcentrationRiskTypeDomain" xlink:label="us-gaap_ConcentrationRiskTypeDomain"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ConcentrationRiskTypeDomain" xlink:label="us-gaap_ConcentrationRiskTypeDomain_2"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_CustomerOneMember" xlink:label="vicr_CustomerOneMember"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_CustomerTwoMember" xlink:label="vicr_CustomerTwoMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_DeferredRevenue" xlink:label="us-gaap_DeferredRevenue"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_DeferredRevenueRecognitionPeriod" xlink:label="vicr_DeferredRevenueRecognitionPeriod"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_EntityWideAccountReceivableMajorCustomerPercentage" xlink:label="vicr_EntityWideAccountReceivableMajorCustomerPercentage"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_EntityWideRevenueMajorCustomerLineItems" xlink:label="us-gaap_EntityWideRevenueMajorCustomerLineItems"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetUsefulLife" xlink:label="us-gaap_FiniteLivedIntangibleAssetUsefulLife"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ForeignCurrencyTransactionGainLossUnrealized" xlink:label="us-gaap_ForeignCurrencyTransactionGainLossUnrealized"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_GeographicConcentrationRiskMember" xlink:label="us-gaap_GeographicConcentrationRiskMember"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_GrossDeferredCostOfRevenue" xlink:label="vicr_GrossDeferredCostOfRevenue"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/country/2013/country-2013-01-31.xsd#country_HK" xlink:label="country_HK"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_LikelihoodPercentageOfTaxBenefitUponSettlement" xlink:label="vicr_LikelihoodPercentageOfTaxBenefitUponSettlement"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_MajorCustomersAxis" xlink:label="us-gaap_MajorCustomersAxis"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_MaximumMember" xlink:label="us-gaap_MaximumMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_MinimumMember" xlink:label="us-gaap_MinimumMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_NameOfMajorCustomerDomain" xlink:label="us-gaap_NameOfMajorCustomerDomain"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_NameOfMajorCustomerDomain" xlink:label="us-gaap_NameOfMajorCustomerDomain_2"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_NumberOfCustomers" xlink:label="vicr_NumberOfCustomers"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_NumberOfCustomersAccountedForTradeAccountReceivable" xlink:label="vicr_NumberOfCustomersAccountedForTradeAccountReceivable"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_NumberOfDistributors" xlink:label="vicr_NumberOfDistributors"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_ProductWarrantyPeriods" xlink:label="vicr_ProductWarrantyPeriods"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_RangeAxis" xlink:label="us-gaap_RangeAxis"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_RangeMember" xlink:label="us-gaap_RangeMember"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_RevenueRecognitionAsPercentageOfNetRevenue" xlink:label="vicr_RevenueRecognitionAsPercentageOfNetRevenue"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_SalesRevenueNetMember" xlink:label="us-gaap_SalesRevenueNetMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ScheduleOfEntityWideRevenueByMajorCustomersByReportingSegmentsTable" xlink:label="us-gaap_ScheduleOfEntityWideRevenueByMajorCustomersByReportingSegmentsTable"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_SegmentGeographicalDomain" xlink:label="us-gaap_SegmentGeographicalDomain"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_SegmentGeographicalDomain" xlink:label="us-gaap_SegmentGeographicalDomain_2"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_ShareBasedCompensationExpenseForNonPerformanceBasedStockOptionsRecognitionPeriod" xlink:label="vicr_ShareBasedCompensationExpenseForNonPerformanceBasedStockOptionsRecognitionPeriod"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StatementGeographicalAxis" xlink:label="us-gaap_StatementGeographicalAxis"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/country/2013/country-2013-01-31.xsd#country_TW" xlink:label="country_TW"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ConcentrationRiskBenchmarkDomain" xlink:to="us-gaap_SalesRevenueNetMember" order="1.2000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_ConcentrationRiskByBenchmarkAxis" xlink:to="us-gaap_ConcentrationRiskBenchmarkDomain" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_ConcentrationRiskByBenchmarkAxis" xlink:to="us-gaap_ConcentrationRiskBenchmarkDomain_2" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_ConcentrationRiskByTypeAxis" xlink:to="us-gaap_ConcentrationRiskTypeDomain" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_ConcentrationRiskByTypeAxis" xlink:to="us-gaap_ConcentrationRiskTypeDomain_2" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ConcentrationRiskTypeDomain" xlink:to="us-gaap_GeographicConcentrationRiskMember" order="1.2100" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_EntityWideRevenueMajorCustomerLineItems" xlink:to="us-gaap_ScheduleOfEntityWideRevenueByMajorCustomersByReportingSegmentsTable" order="100.0000" xbrldt:closed="true" xbrldt:contextElement="segment" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EntityWideRevenueMajorCustomerLineItems" xlink:to="vicr_NumberOfDistributors" order="1.0100" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EntityWideRevenueMajorCustomerLineItems" xlink:to="us-gaap_DeferredRevenue" order="1.0200" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EntityWideRevenueMajorCustomerLineItems" xlink:to="vicr_GrossDeferredCostOfRevenue" order="1.0300" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EntityWideRevenueMajorCustomerLineItems" xlink:to="vicr_DeferredRevenueRecognitionPeriod" order="1.0400" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EntityWideRevenueMajorCustomerLineItems" xlink:to="vicr_RevenueRecognitionAsPercentageOfNetRevenue" order="1.0500" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EntityWideRevenueMajorCustomerLineItems" xlink:to="us-gaap_ForeignCurrencyTransactionGainLossUnrealized" order="1.0600" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EntityWideRevenueMajorCustomerLineItems" xlink:to="vicr_CashAndCashEquivalentsMaturityPeriods" order="1.0700" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EntityWideRevenueMajorCustomerLineItems" xlink:to="us-gaap_AuctionRateSecuritiesNoncurrent" order="1.0800" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EntityWideRevenueMajorCustomerLineItems" xlink:to="vicr_NumberOfCustomersAccountedForTradeAccountReceivable" order="1.0900" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EntityWideRevenueMajorCustomerLineItems" xlink:to="vicr_EntityWideAccountReceivableMajorCustomerPercentage" order="1.1000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EntityWideRevenueMajorCustomerLineItems" xlink:to="us-gaap_ConcentrationRiskPercentage1" order="1.1100" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EntityWideRevenueMajorCustomerLineItems" xlink:to="vicr_NumberOfCustomers" order="1.1200" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EntityWideRevenueMajorCustomerLineItems" xlink:to="us-gaap_FiniteLivedIntangibleAssetUsefulLife" order="1.1300" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EntityWideRevenueMajorCustomerLineItems" xlink:to="us-gaap_AdvertisingExpense" order="1.1400" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EntityWideRevenueMajorCustomerLineItems" xlink:to="vicr_ProductWarrantyPeriods" order="1.1500" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EntityWideRevenueMajorCustomerLineItems" xlink:to="vicr_LikelihoodPercentageOfTaxBenefitUponSettlement" order="1.1600" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EntityWideRevenueMajorCustomerLineItems" xlink:to="vicr_ShareBasedCompensationExpenseForNonPerformanceBasedStockOptionsRecognitionPeriod" order="1.1700" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_MajorCustomersAxis" xlink:to="us-gaap_NameOfMajorCustomerDomain" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_MajorCustomersAxis" xlink:to="us-gaap_NameOfMajorCustomerDomain_2" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_NameOfMajorCustomerDomain" xlink:to="vicr_CustomerOneMember" order="1.1900" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_NameOfMajorCustomerDomain" xlink:to="vicr_CustomerTwoMember" order="1.2400" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_RangeAxis" xlink:to="us-gaap_RangeMember" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RangeMember" xlink:to="us-gaap_MaximumMember" order="1.1800" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RangeMember" xlink:to="us-gaap_MinimumMember" order="1.2300" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_ScheduleOfEntityWideRevenueByMajorCustomersByReportingSegmentsTable" xlink:to="us-gaap_RangeAxis" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_ScheduleOfEntityWideRevenueByMajorCustomersByReportingSegmentsTable" xlink:to="us-gaap_MajorCustomersAxis" order="2.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_ScheduleOfEntityWideRevenueByMajorCustomersByReportingSegmentsTable" xlink:to="us-gaap_StatementGeographicalAxis" order="3.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_ScheduleOfEntityWideRevenueByMajorCustomersByReportingSegmentsTable" xlink:to="us-gaap_ConcentrationRiskByBenchmarkAxis" order="4.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_ScheduleOfEntityWideRevenueByMajorCustomersByReportingSegmentsTable" xlink:to="us-gaap_ConcentrationRiskByTypeAxis" order="5.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_SegmentGeographicalDomain" xlink:to="country_HK" order="1.2200" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_SegmentGeographicalDomain" xlink:to="country_CN" order="1.2500" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_SegmentGeographicalDomain" xlink:to="country_TW" order="1.2600" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_StatementGeographicalAxis" xlink:to="us-gaap_SegmentGeographicalDomain" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_StatementGeographicalAxis" xlink:to="us-gaap_SegmentGeographicalDomain_2" order="1.0000" priority="2" use="optional"/>
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/DisclosureSignificantAccountingPoliciesComputationOfBasicAndDilutedIncomeLossPerShare">
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/DisclosureSignificantAccountingPoliciesComputationOfBasicAndDilutedIncomeLossPerShareParenthetical">
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/DisclosureStockBasedCompensationAndEmployeeBenefitPlansAdditionalInformation">
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationStockOptionsRequisiteServicePeriodRecognition" xlink:label="us-gaap_AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationStockOptionsRequisiteServicePeriodRecognition"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_AgeOfEmployeesOrDirectors" xlink:label="vicr_AgeOfEmployeesOrDirectors"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AllocatedShareBasedCompensationExpense" xlink:label="us-gaap_AllocatedShareBasedCompensationExpense"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AwardTypeAxis" xlink:label="us-gaap_AwardTypeAxis"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_ChipOptionsActuallyVest" xlink:label="vicr_ChipOptionsActuallyVest"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_ChipOptionsActuallyVestForfeiture" xlink:label="vicr_ChipOptionsActuallyVestForfeiture"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_CommonStockCapitalSharesReservedForFutureIssuance" xlink:label="us-gaap_CommonStockCapitalSharesReservedForFutureIssuance"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_DefinedContributionPlanEmployerDiscretionaryContributionAmount" xlink:label="us-gaap_DefinedContributionPlanEmployerDiscretionaryContributionAmount"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_DefinedContributionPlanEmployersMatchingContributionAnnualVestingPercentage" xlink:label="us-gaap_DefinedContributionPlanEmployersMatchingContributionAnnualVestingPercentage"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_DefinedContributionPlanMaximumAnnualContributionsPerEmployeePercent" xlink:label="us-gaap_DefinedContributionPlanMaximumAnnualContributionsPerEmployeePercent"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_DescriptionOfDefinedContributionPensionAndOtherPostretirementPlans" xlink:label="us-gaap_DescriptionOfDefinedContributionPensionAndOtherPostretirementPlans"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_EmployeesAndDirectorsMember" xlink:label="vicr_EmployeesAndDirectorsMember"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_EmployeeServiceShareBasedCompensationAwardsCompensationCostsSubjectToImmediateRecognitionDueToAgeOfRecipient" xlink:label="vicr_EmployeeServiceShareBasedCompensationAwardsCompensationCostsSubjectToImmediateRecognitionDueToAgeOfRecipient"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_EmployeeServiceShareBasedCompensationNonvestedAwardsExpectedCompensationCostRecognizedStockOptionsYearFive" xlink:label="vicr_EmployeeServiceShareBasedCompensationNonvestedAwardsExpectedCompensationCostRecognizedStockOptionsYearFive"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_EmployeeServiceShareBasedCompensationNonvestedAwardsExpectedCompensationCostRecognizedStockOptionsYearFour" xlink:label="vicr_EmployeeServiceShareBasedCompensationNonvestedAwardsExpectedCompensationCostRecognizedStockOptionsYearFour"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_EmployeeServiceShareBasedCompensationNonvestedAwardsExpectedCompensationCostRecognizedStockOptionsYearOne" xlink:label="vicr_EmployeeServiceShareBasedCompensationNonvestedAwardsExpectedCompensationCostRecognizedStockOptionsYearOne"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_EmployeeServiceShareBasedCompensationNonvestedAwardsExpectedCompensationCostRecognizedStockOptionsYearThree" xlink:label="vicr_EmployeeServiceShareBasedCompensationNonvestedAwardsExpectedCompensationCostRecognizedStockOptionsYearThree"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_EmployeeServiceShareBasedCompensationNonVestedAwardsExpectedCompensationCostRecognizedStockOptionsYearTwo" xlink:label="vicr_EmployeeServiceShareBasedCompensationNonVestedAwardsExpectedCompensationCostRecognizedStockOptionsYearTwo"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_IncomeStatementLocationAxis" xlink:label="us-gaap_IncomeStatementLocationAxis"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="us-gaap_IncomeStatementLocationDomain"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="us-gaap_IncomeStatementLocationDomain_2"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_MaturityPeriodOfTreasuryBond" xlink:label="vicr_MaturityPeriodOfTreasuryBond"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_MaximumMember" xlink:label="us-gaap_MaximumMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_MinimumMember" xlink:label="us-gaap_MinimumMember"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_NumberOfEligibleParticipantsAcceptedOptionExchangeOffer" xlink:label="vicr_NumberOfEligibleParticipantsAcceptedOptionExchangeOffer"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_NumberOfSharesExchangedUnderShareExchangeAgreement" xlink:label="vicr_NumberOfSharesExchangedUnderShareExchangeAgreement"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_NumberOfSharesExchangedUnderShareExchangeAgreementPercentage" xlink:label="vicr_NumberOfSharesExchangedUnderShareExchangeAgreementPercentage"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_PerformanceBasedOptionsMember" xlink:label="vicr_PerformanceBasedOptionsMember"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_PicorMember" xlink:label="vicr_PicorMember"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_PicorOptionsActuallyVest" xlink:label="vicr_PicorOptionsActuallyVest"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_PicorOptionsActuallyVestForfeiture" xlink:label="vicr_PicorOptionsActuallyVestForfeiture"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_PicorPlanMember" xlink:label="vicr_PicorPlanMember"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_PicorStockOptionsMember" xlink:label="vicr_PicorStockOptionsMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_PlanNameAxis" xlink:label="us-gaap_PlanNameAxis"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_PlanNameDomain" xlink:label="us-gaap_PlanNameDomain"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_PlanNameDomain" xlink:label="us-gaap_PlanNameDomain_2"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ProceedsFromStockOptionsExercised" xlink:label="us-gaap_ProceedsFromStockOptionsExercised"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_RangeAxis" xlink:label="us-gaap_RangeAxis"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_RangeMember" xlink:label="us-gaap_RangeMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ResearchAndDevelopmentExpenseMember" xlink:label="us-gaap_ResearchAndDevelopmentExpenseMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:label="us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_SellingGeneralAndAdministrativeExpensesMember" xlink:label="us-gaap_SellingGeneralAndAdministrativeExpensesMember"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPercentage" xlink:label="vicr_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPercentage"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_ShareBasedCompensationArrangementByShareBasedPaymentAwardForfeitureRate" xlink:label="vicr_ShareBasedCompensationArrangementByShareBasedPaymentAwardForfeitureRate"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisePrice" xlink:label="vicr_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisePrice"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodExercisePrice" xlink:label="vicr_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodExercisePrice"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedInPeriodFairValue1" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedInPeriodFairValue1"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardPlanModificationIncrementalCompensationCost" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardPlanModificationIncrementalCompensationCost"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_ShareBasedCompensationArrangementByShareBasedPaymentAwardTermOfAward" xlink:label="vicr_ShareBasedCompensationArrangementByShareBasedPaymentAwardTermOfAward"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_StockBonusPlanMember" xlink:label="vicr_StockBonusPlanMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StockRepurchaseProgramAuthorizedAmount" xlink:label="us-gaap_StockRepurchaseProgramAuthorizedAmount"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StockRepurchaseProgramNumberOfSharesAuthorizedToBeRepurchased" xlink:label="us-gaap_StockRepurchaseProgramNumberOfSharesAuthorizedToBeRepurchased"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_StockRepurchaseProgramReductionInAuthorizedRepurchaseAmount" xlink:label="vicr_StockRepurchaseProgramReductionInAuthorizedRepurchaseAmount"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_TimeBasedOptionMember" xlink:label="vicr_TimeBasedOptionMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_TitleOfIndividualAxis" xlink:label="us-gaap_TitleOfIndividualAxis"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_TitleOfIndividualWithRelationshipToEntityDomain" xlink:label="us-gaap_TitleOfIndividualWithRelationshipToEntityDomain"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_TrancheFiveMember" xlink:label="vicr_TrancheFiveMember"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_TrancheFourMember" xlink:label="vicr_TrancheFourMember"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_TranchesOneMember" xlink:label="vicr_TranchesOneMember"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_TranchesThreeMember" xlink:label="vicr_TranchesThreeMember"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_TranchesTwoMember" xlink:label="vicr_TranchesTwoMember"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_TwoThousandOnePicorPlanMember" xlink:label="vicr_TwoThousandOnePicorPlanMember"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_TwoThousandPlanMember" xlink:label="vicr_TwoThousandPlanMember"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_TwoThousandSevenViChipPlanMember" xlink:label="vicr_TwoThousandSevenViChipPlanMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_VestingAxis" xlink:label="us-gaap_VestingAxis"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_VestingDomain" xlink:label="us-gaap_VestingDomain"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_VestingDomain" xlink:label="us-gaap_VestingDomain_2"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_ViChipMember" xlink:label="vicr_ViChipMember"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_ViChipPlanOptionsMember" xlink:label="vicr_ViChipPlanOptionsMember"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_ViChipStockOptionsMember" xlink:label="vicr_ViChipStockOptionsMember"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_VicorNineteenNinetyEightPlanMember" xlink:label="vicr_VicorNineteenNinetyEightPlanMember"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_VicorOptionsActuallyVest" xlink:label="vicr_VicorOptionsActuallyVest"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_VicorPlanMember" xlink:label="vicr_VicorPlanMember"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_VicorStockOptionsMember" xlink:label="vicr_VicorStockOptionsMember"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_VicorTwoThousandPlanMember" xlink:label="vicr_VicorTwoThousandPlanMember"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_AwardTypeAxis" xlink:to="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_IncomeStatementLocationAxis" xlink:to="us-gaap_IncomeStatementLocationDomain" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_IncomeStatementLocationAxis" xlink:to="us-gaap_IncomeStatementLocationDomain_2" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_IncomeStatementLocationDomain" xlink:to="us-gaap_SellingGeneralAndAdministrativeExpensesMember" order="1.5300" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_IncomeStatementLocationDomain" xlink:to="us-gaap_ResearchAndDevelopmentExpenseMember" order="1.5800" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_PlanNameAxis" xlink:to="us-gaap_PlanNameDomain" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_PlanNameAxis" xlink:to="us-gaap_PlanNameDomain_2" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_PlanNameDomain" xlink:to="vicr_VicorTwoThousandPlanMember" order="1.4800" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_PlanNameDomain" xlink:to="vicr_VicorPlanMember" order="1.5400" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_PlanNameDomain" xlink:to="vicr_VicorNineteenNinetyEightPlanMember" order="1.5900" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_PlanNameDomain" xlink:to="vicr_TwoThousandOnePicorPlanMember" order="1.6100" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_PlanNameDomain" xlink:to="vicr_TwoThousandSevenViChipPlanMember" order="1.6300" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_PlanNameDomain" xlink:to="vicr_PicorPlanMember" order="1.6500" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_PlanNameDomain" xlink:to="vicr_PicorMember" order="1.6600" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_PlanNameDomain" xlink:to="vicr_ViChipMember" order="1.6700" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_PlanNameDomain" xlink:to="vicr_PicorStockOptionsMember" order="1.6800" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_PlanNameDomain" xlink:to="vicr_VicorStockOptionsMember" order="1.6900" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_PlanNameDomain" xlink:to="vicr_ViChipStockOptionsMember" order="1.7000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_PlanNameDomain" xlink:to="vicr_ViChipPlanOptionsMember" order="1.7100" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_PlanNameDomain" xlink:to="vicr_TwoThousandPlanMember" order="1.7200" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_PlanNameDomain" xlink:to="vicr_StockBonusPlanMember" order="1.7300" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_RangeAxis" xlink:to="us-gaap_RangeMember" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RangeMember" xlink:to="us-gaap_MinimumMember" order="1.4900" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RangeMember" xlink:to="us-gaap_MaximumMember" order="1.5500" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:to="us-gaap_PlanNameAxis" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:to="us-gaap_IncomeStatementLocationAxis" order="2.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:to="us-gaap_RangeAxis" order="3.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:to="us-gaap_VestingAxis" order="4.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:to="us-gaap_AwardTypeAxis" order="5.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:to="us-gaap_TitleOfIndividualAxis" order="6.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" order="100.0000" xbrldt:closed="true" xbrldt:contextElement="segment" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="us-gaap_CommonStockCapitalSharesReservedForFutureIssuance" order="1.0100" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent" order="1.0200" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="vicr_ShareBasedCompensationArrangementByShareBasedPaymentAwardTermOfAward" order="1.0300" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant" order="1.0400" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1" order="1.0500" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="vicr_NumberOfEligibleParticipantsAcceptedOptionExchangeOffer" order="1.0600" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="vicr_NumberOfSharesExchangedUnderShareExchangeAgreement" order="1.0700" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="vicr_NumberOfSharesExchangedUnderShareExchangeAgreementPercentage" order="1.0800" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod" order="1.0900" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="vicr_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisePrice" order="1.1000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice" order="1.1100" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardPlanModificationIncrementalCompensationCost" order="1.1200" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions" order="1.1300" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="us-gaap_AllocatedShareBasedCompensationExpense" order="1.1400" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="vicr_AgeOfEmployeesOrDirectors" order="1.1500" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="vicr_EmployeeServiceShareBasedCompensationAwardsCompensationCostsSubjectToImmediateRecognitionDueToAgeOfRecipient" order="1.1600" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="vicr_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodExercisePrice" order="1.1700" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross" order="1.1800" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber" order="1.1900" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="us-gaap_StockRepurchaseProgramNumberOfSharesAuthorizedToBeRepurchased" order="1.2000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="us-gaap_StockRepurchaseProgramAuthorizedAmount" order="1.2100" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="us-gaap_AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationStockOptionsRequisiteServicePeriodRecognition" order="1.2200" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="vicr_StockRepurchaseProgramReductionInAuthorizedRepurchaseAmount" order="1.2300" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="vicr_MaturityPeriodOfTreasuryBond" order="1.2400" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="vicr_VicorOptionsActuallyVest" order="1.2500" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="vicr_ShareBasedCompensationArrangementByShareBasedPaymentAwardForfeitureRate" order="1.2600" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="vicr_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPercentage" order="1.2700" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="vicr_PicorOptionsActuallyVestForfeiture" order="1.2800" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="vicr_PicorOptionsActuallyVest" order="1.2900" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="vicr_ChipOptionsActuallyVest" order="1.3000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="vicr_ChipOptionsActuallyVestForfeiture" order="1.3100" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber" order="1.3200" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice" order="1.3300" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue" order="1.3400" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="us-gaap_ProceedsFromStockOptionsExercised" order="1.3500" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedInPeriodFairValue1" order="1.3600" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1" order="1.3700" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="vicr_EmployeeServiceShareBasedCompensationNonvestedAwardsExpectedCompensationCostRecognizedStockOptionsYearOne" order="1.3800" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="vicr_EmployeeServiceShareBasedCompensationNonVestedAwardsExpectedCompensationCostRecognizedStockOptionsYearTwo" order="1.3900" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="vicr_EmployeeServiceShareBasedCompensationNonvestedAwardsExpectedCompensationCostRecognizedStockOptionsYearThree" order="1.4000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="vicr_EmployeeServiceShareBasedCompensationNonvestedAwardsExpectedCompensationCostRecognizedStockOptionsYearFour" order="1.4100" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="vicr_EmployeeServiceShareBasedCompensationNonvestedAwardsExpectedCompensationCostRecognizedStockOptionsYearFive" order="1.4200" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue" order="1.4300" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="us-gaap_DefinedContributionPlanMaximumAnnualContributionsPerEmployeePercent" order="1.4400" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="us-gaap_DescriptionOfDefinedContributionPensionAndOtherPostretirementPlans" order="1.4500" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="us-gaap_DefinedContributionPlanEmployersMatchingContributionAnnualVestingPercentage" order="1.4600" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="us-gaap_DefinedContributionPlanEmployerDiscretionaryContributionAmount" order="1.4700" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="vicr_PerformanceBasedOptionsMember" order="1.5000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="vicr_TimeBasedOptionMember" order="1.5600" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_TitleOfIndividualAxis" xlink:to="us-gaap_TitleOfIndividualWithRelationshipToEntityDomain" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_TitleOfIndividualWithRelationshipToEntityDomain" xlink:to="vicr_EmployeesAndDirectorsMember" order="1.5200" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_VestingAxis" xlink:to="us-gaap_VestingDomain" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_VestingAxis" xlink:to="us-gaap_VestingDomain_2" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_VestingDomain" xlink:to="vicr_TranchesOneMember" order="1.5100" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_VestingDomain" xlink:to="vicr_TranchesTwoMember" order="1.5700" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_VestingDomain" xlink:to="vicr_TranchesThreeMember" order="1.6000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_VestingDomain" xlink:to="vicr_TrancheFourMember" order="1.6200" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_VestingDomain" xlink:to="vicr_TrancheFiveMember" order="1.6400" priority="2" use="optional"/>
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/DisclosureStockBasedCompensationAndEmployeeBenefitPlansStockBasedCompensationExpense">
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AllocatedShareBasedCompensationExpense" xlink:label="us-gaap_AllocatedShareBasedCompensationExpense"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_CostOfSalesMember" xlink:label="us-gaap_CostOfSalesMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_IncomeStatementLocationAxis" xlink:label="us-gaap_IncomeStatementLocationAxis"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="us-gaap_IncomeStatementLocationDomain"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ResearchAndDevelopmentExpenseMember" xlink:label="us-gaap_ResearchAndDevelopmentExpenseMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable" xlink:label="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_SellingGeneralAndAdministrativeExpensesMember" xlink:label="us-gaap_SellingGeneralAndAdministrativeExpensesMember"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:to="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable" order="100.0000" xbrldt:closed="true" xbrldt:contextElement="segment" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:to="us-gaap_AllocatedShareBasedCompensationExpense" order="1.0100" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_IncomeStatementLocationAxis" xlink:to="us-gaap_IncomeStatementLocationDomain" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_IncomeStatementLocationDomain" xlink:to="us-gaap_CostOfSalesMember" order="1.0200" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_IncomeStatementLocationDomain" xlink:to="us-gaap_SellingGeneralAndAdministrativeExpensesMember" order="1.0300" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_IncomeStatementLocationDomain" xlink:to="us-gaap_ResearchAndDevelopmentExpenseMember" order="1.0400" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable" xlink:to="us-gaap_IncomeStatementLocationAxis" order="1.0000" priority="2" use="optional"/>
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/DisclosureStockBasedCompensationAndEmployeeBenefitPlansWeightedAverageAssumptionsForFairValueForStockOptions">
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AwardTypeAxis" xlink:label="us-gaap_AwardTypeAxis"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2013/dei-2013-01-31.xsd#dei_EntityDomain" xlink:label="dei_EntityDomain"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2013/dei-2013-01-31.xsd#dei_EntityDomain" xlink:label="dei_EntityDomain_2"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:label="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueByBalanceSheetGroupingTable" xlink:label="us-gaap_FairValueByBalanceSheetGroupingTable"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_FiscalYearAxis" xlink:label="vicr_FiscalYearAxis"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_FiscalYearDomain" xlink:label="vicr_FiscalYearDomain"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_FiscalYearDomain" xlink:label="vicr_FiscalYearDomain_2"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2013/dei-2013-01-31.xsd#dei_LegalEntityAxis" xlink:label="dei_LegalEntityAxis"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_NonPerformanceBasedStockOptionMember" xlink:label="vicr_NonPerformanceBasedStockOptionMember"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_PicorMember" xlink:label="vicr_PicorMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_TwoThousandElevenMember" xlink:label="vicr_TwoThousandElevenMember"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_TwoThousandTwelveMember" xlink:label="vicr_TwoThousandTwelveMember"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_ViChipMember" xlink:label="vicr_ViChipMember"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_VicorMember" xlink:label="vicr_VicorMember"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_AwardTypeAxis" xlink:to="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_EntityDomain" xlink:to="vicr_VicorMember" order="1.0100" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_EntityDomain" xlink:to="vicr_ViChipMember" order="1.0200" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_EntityDomain" xlink:to="vicr_PicorMember" order="1.0300" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_FairValueByBalanceSheetGroupingTable" order="100.0000" xbrldt:closed="true" xbrldt:contextElement="segment" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate" order="1.0400" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate" order="1.0500" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate" order="1.0600" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1" order="1.0700" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_FairValueByBalanceSheetGroupingTable" xlink:to="us-gaap_AwardTypeAxis" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_FairValueByBalanceSheetGroupingTable" xlink:to="dei_LegalEntityAxis" order="2.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_FairValueByBalanceSheetGroupingTable" xlink:to="vicr_FiscalYearAxis" order="3.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="vicr_FiscalYearAxis" xlink:to="vicr_FiscalYearDomain" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="vicr_FiscalYearAxis" xlink:to="vicr_FiscalYearDomain_2" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="vicr_FiscalYearDomain" xlink:to="vicr_TwoThousandTwelveMember" order="1.0900" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="vicr_FiscalYearDomain" xlink:to="vicr_TwoThousandElevenMember" order="1.1000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="dei_LegalEntityAxis" xlink:to="dei_EntityDomain" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="dei_LegalEntityAxis" xlink:to="dei_EntityDomain_2" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="vicr_NonPerformanceBasedStockOptionMember" order="1.0800" priority="2" use="optional"/>
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/DisclosureStockBasedCompensationAndEmployeeBenefitPlansSummaryOfTheActivityUnderTheVicorStockOptionPlans">
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:label="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueByBalanceSheetGroupingTable" xlink:label="us-gaap_FairValueByBalanceSheetGroupingTable"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueByMeasurementBasisAxis" xlink:label="us-gaap_FairValueByMeasurementBasisAxis"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueDisclosureItemAmountsDomain" xlink:label="us-gaap_FairValueDisclosureItemAmountsDomain"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageExercisePrice" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageExercisePrice"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageRemainingContractualTerm1" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageRemainingContractualTerm1"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised" xlink:label="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_VicorMember" xlink:label="vicr_VicorMember"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_FairValueByBalanceSheetGroupingTable" order="100.0000" xbrldt:closed="true" xbrldt:contextElement="segment" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber" order="1.0100" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross" order="1.0200" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod" order="1.0300" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised" order="1.0400" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber" order="1.0600" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber" order="1.0700" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice" order="1.0800" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice" order="1.0900" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice" order="1.1000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice" order="1.1100" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice" order="1.1300" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageExercisePrice" order="1.1400" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2" order="1.1500" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1" order="1.1600" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageRemainingContractualTerm1" order="1.1700" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue" order="1.1800" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1" order="1.1900" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue" order="1.2000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_FairValueByBalanceSheetGroupingTable" xlink:to="us-gaap_FairValueByMeasurementBasisAxis" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_FairValueByMeasurementBasisAxis" xlink:to="us-gaap_FairValueDisclosureItemAmountsDomain" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueDisclosureItemAmountsDomain" xlink:to="vicr_VicorMember" order="1.2100" priority="2" use="optional"/>
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/DisclosureStockBasedCompensationAndEmployeeBenefitPlansSummaryOfTheActivityUnderThePicorStockOptionPlans">
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:label="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueByBalanceSheetGroupingTable" xlink:label="us-gaap_FairValueByBalanceSheetGroupingTable"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueByMeasurementBasisAxis" xlink:label="us-gaap_FairValueByMeasurementBasisAxis"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueDisclosureItemAmountsDomain" xlink:label="us-gaap_FairValueDisclosureItemAmountsDomain"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_PicorMember" xlink:label="vicr_PicorMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageExercisePrice" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageExercisePrice"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageRemainingContractualTerm1" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageRemainingContractualTerm1"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised" xlink:label="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_FairValueByBalanceSheetGroupingTable" order="100.0000" xbrldt:closed="true" xbrldt:contextElement="segment" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber" order="1.0100" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross" order="1.0200" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod" order="1.0300" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised" order="1.0400" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber" order="1.0600" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber" order="1.0700" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice" order="1.0800" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice" order="1.0900" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice" order="1.1000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice" order="1.1100" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice" order="1.1300" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageExercisePrice" order="1.1400" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2" order="1.1500" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1" order="1.1600" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageRemainingContractualTerm1" order="1.1700" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue" order="1.1800" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1" order="1.1900" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue" order="1.2000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_FairValueByBalanceSheetGroupingTable" xlink:to="us-gaap_FairValueByMeasurementBasisAxis" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_FairValueByMeasurementBasisAxis" xlink:to="us-gaap_FairValueDisclosureItemAmountsDomain" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueDisclosureItemAmountsDomain" xlink:to="vicr_PicorMember" order="1.2100" priority="2" use="optional"/>
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/DisclosureStockBasedCompensationAndEmployeeBenefitPlansSummaryOfTheActivityUnderTheVIChipStockOptionPlans">
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:label="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueByBalanceSheetGroupingTable" xlink:label="us-gaap_FairValueByBalanceSheetGroupingTable"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueByMeasurementBasisAxis" xlink:label="us-gaap_FairValueByMeasurementBasisAxis"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueDisclosureItemAmountsDomain" xlink:label="us-gaap_FairValueDisclosureItemAmountsDomain"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageExercisePrice" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageExercisePrice"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageRemainingContractualTerm1" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageRemainingContractualTerm1"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised" xlink:label="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_ViChipMember" xlink:label="vicr_ViChipMember"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_FairValueByBalanceSheetGroupingTable" order="100.0000" xbrldt:closed="true" xbrldt:contextElement="segment" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber" order="1.0100" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross" order="1.0200" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod" order="1.0300" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised" order="1.0400" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber" order="1.0600" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber" order="1.0700" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice" order="1.0800" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice" order="1.0900" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice" order="1.1000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice" order="1.1100" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice" order="1.1300" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageExercisePrice" order="1.1400" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2" order="1.1500" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1" order="1.1600" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageRemainingContractualTerm1" order="1.1700" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue" order="1.1800" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1" order="1.1900" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue" order="1.2000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_FairValueByBalanceSheetGroupingTable" xlink:to="us-gaap_FairValueByMeasurementBasisAxis" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_FairValueByMeasurementBasisAxis" xlink:to="us-gaap_FairValueDisclosureItemAmountsDomain" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueDisclosureItemAmountsDomain" xlink:to="vicr_ViChipMember" order="1.2100" priority="2" use="optional"/>
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/DisclosureStockBasedCompensationAndEmployeeBenefitPlansSummaryOfTheActivityUnderTheVIChipStockOptionPlansParenthetical">
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AwardTypeAxis" xlink:label="us-gaap_AwardTypeAxis"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ChiefExecutiveOfficerMember" xlink:label="us-gaap_ChiefExecutiveOfficerMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:label="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueByBalanceSheetGroupingTable" xlink:label="us-gaap_FairValueByBalanceSheetGroupingTable"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_2"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_TitleOfIndividualAxis" xlink:label="us-gaap_TitleOfIndividualAxis"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_TitleOfIndividualWithRelationshipToEntityDomain" xlink:label="us-gaap_TitleOfIndividualWithRelationshipToEntityDomain"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_TitleOfIndividualWithRelationshipToEntityDomain" xlink:label="us-gaap_TitleOfIndividualWithRelationshipToEntityDomain_2"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_ViChipStockOptionsMember" xlink:label="vicr_ViChipStockOptionsMember"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_AwardTypeAxis" xlink:to="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_AwardTypeAxis" xlink:to="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_2" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_FairValueByBalanceSheetGroupingTable" order="100.0000" xbrldt:closed="true" xbrldt:contextElement="segment" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross" order="1.0200" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_FairValueByBalanceSheetGroupingTable" xlink:to="us-gaap_TitleOfIndividualAxis" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_FairValueByBalanceSheetGroupingTable" xlink:to="us-gaap_AwardTypeAxis" order="2.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="vicr_ViChipStockOptionsMember" order="1.0300" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_TitleOfIndividualAxis" xlink:to="us-gaap_TitleOfIndividualWithRelationshipToEntityDomain" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_TitleOfIndividualAxis" xlink:to="us-gaap_TitleOfIndividualWithRelationshipToEntityDomain_2" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_TitleOfIndividualWithRelationshipToEntityDomain" xlink:to="us-gaap_ChiefExecutiveOfficerMember" order="1.0100" priority="2" use="optional"/>
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/DisclosureShortTermAndLongTermInvestmentsAdditionalInformation">
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_AggregateTemporaryImpairmentLoss" xlink:label="vicr_AggregateTemporaryImpairmentLoss"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_AuctionFailedSecuritiesUnrealizedLossPositionMinimumPeriod" xlink:label="vicr_AuctionFailedSecuritiesUnrealizedLossPositionMinimumPeriod"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AuctionRateSecuritiesMember" xlink:label="us-gaap_AuctionRateSecuritiesMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AvailableForSaleSecurities" xlink:label="us-gaap_AvailableForSaleSecurities"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AvailableForSaleSecuritiesAmortizedCost" xlink:label="us-gaap_AvailableForSaleSecuritiesAmortizedCost"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_AvailableForSaleSecuritiesGrossUnrealizedLossAccumulatedInInvestments" xlink:label="vicr_AvailableForSaleSecuritiesGrossUnrealizedLossAccumulatedInInvestments"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_DecreaseInFairValueOfFailedAuctionSecurities" xlink:label="vicr_DecreaseInFairValueOfFailedAuctionSecurities"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_FairValueAvailableForSaleOfSecuritiesRedemption" xlink:label="vicr_FairValueAvailableForSaleOfSecuritiesRedemption"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_InterestRatesAuctionPeriod" xlink:label="vicr_InterestRatesAuctionPeriod"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis" xlink:label="us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain" xlink:label="us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_MaximumMember" xlink:label="us-gaap_MaximumMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_MinimumMember" xlink:label="us-gaap_MinimumMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsCreditLossesOnDebtSecuritiesHeld" xlink:label="us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsCreditLossesOnDebtSecuritiesHeld"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_PeriodForWhichFailedAuctionSecuritiesBeenInUnrealizedLossPosition" xlink:label="vicr_PeriodForWhichFailedAuctionSecuritiesBeenInUnrealizedLossPosition"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_RangeAxis" xlink:label="us-gaap_RangeAxis"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_RangeMember" xlink:label="us-gaap_RangeMember"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_SubsequentLossRecovery" xlink:label="vicr_SubsequentLossRecovery"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_UnrealizedLossesOnShortTermAndLongTermInvestmentsLineItems" xlink:label="vicr_UnrealizedLossesOnShortTermAndLongTermInvestmentsLineItems"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_UnrealizedLossesOnShortTermAndLongTermInvestmentsTable" xlink:label="vicr_UnrealizedLossesOnShortTermAndLongTermInvestmentsTable"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis" xlink:to="us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain" xlink:to="us-gaap_AuctionRateSecuritiesMember" order="1.1300" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_RangeAxis" xlink:to="us-gaap_RangeMember" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RangeMember" xlink:to="us-gaap_MinimumMember" order="1.1200" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RangeMember" xlink:to="us-gaap_MaximumMember" order="1.1400" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="vicr_UnrealizedLossesOnShortTermAndLongTermInvestmentsLineItems" xlink:to="vicr_UnrealizedLossesOnShortTermAndLongTermInvestmentsTable" order="100.0000" xbrldt:closed="true" xbrldt:contextElement="segment" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="vicr_UnrealizedLossesOnShortTermAndLongTermInvestmentsLineItems" xlink:to="us-gaap_AvailableForSaleSecuritiesAmortizedCost" order="1.0100" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="vicr_UnrealizedLossesOnShortTermAndLongTermInvestmentsLineItems" xlink:to="vicr_InterestRatesAuctionPeriod" order="1.0200" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="vicr_UnrealizedLossesOnShortTermAndLongTermInvestmentsLineItems" xlink:to="vicr_PeriodForWhichFailedAuctionSecuritiesBeenInUnrealizedLossPosition" order="1.0300" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="vicr_UnrealizedLossesOnShortTermAndLongTermInvestmentsLineItems" xlink:to="vicr_AuctionFailedSecuritiesUnrealizedLossPositionMinimumPeriod" order="1.0400" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="vicr_UnrealizedLossesOnShortTermAndLongTermInvestmentsLineItems" xlink:to="us-gaap_AvailableForSaleSecurities" order="1.0500" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="vicr_UnrealizedLossesOnShortTermAndLongTermInvestmentsLineItems" xlink:to="vicr_DecreaseInFairValueOfFailedAuctionSecurities" order="1.0600" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="vicr_UnrealizedLossesOnShortTermAndLongTermInvestmentsLineItems" xlink:to="vicr_FairValueAvailableForSaleOfSecuritiesRedemption" order="1.0700" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="vicr_UnrealizedLossesOnShortTermAndLongTermInvestmentsLineItems" xlink:to="vicr_AvailableForSaleSecuritiesGrossUnrealizedLossAccumulatedInInvestments" order="1.0800" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="vicr_UnrealizedLossesOnShortTermAndLongTermInvestmentsLineItems" xlink:to="us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsCreditLossesOnDebtSecuritiesHeld" order="1.0900" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="vicr_UnrealizedLossesOnShortTermAndLongTermInvestmentsLineItems" xlink:to="vicr_AggregateTemporaryImpairmentLoss" order="1.1000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="vicr_UnrealizedLossesOnShortTermAndLongTermInvestmentsLineItems" xlink:to="vicr_SubsequentLossRecovery" order="1.1100" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="vicr_UnrealizedLossesOnShortTermAndLongTermInvestmentsTable" xlink:to="us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="vicr_UnrealizedLossesOnShortTermAndLongTermInvestmentsTable" xlink:to="us-gaap_RangeAxis" order="2.0000" priority="2" use="optional"/>
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/DisclosureShortTermAndLongTermInvestmentsSummaryOfAvailableforSaleSecurities">
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AuctionRateSecuritiesMember" xlink:label="us-gaap_AuctionRateSecuritiesMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AvailableForSaleSecurities" xlink:label="us-gaap_AvailableForSaleSecurities"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AvailableForSaleSecuritiesAmortizedCost" xlink:label="us-gaap_AvailableForSaleSecuritiesAmortizedCost"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_AvailableForSaleSecuritiesGrossUnrealizedGainsAccumulatedInInvestments" xlink:label="vicr_AvailableForSaleSecuritiesGrossUnrealizedGainsAccumulatedInInvestments"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_AvailableForSaleSecuritiesGrossUnrealizedLossAccumulatedInInvestments" xlink:label="vicr_AvailableForSaleSecuritiesGrossUnrealizedLossAccumulatedInInvestments"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_BrokeredCertificatesOfDepositMember" xlink:label="vicr_BrokeredCertificatesOfDepositMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_CertificatesOfDepositMember" xlink:label="us-gaap_CertificatesOfDepositMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis" xlink:label="us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain" xlink:label="us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems" xlink:label="us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesTable" xlink:label="us-gaap_ScheduleOfAvailableForSaleSecuritiesTable"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis" xlink:to="us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain" xlink:to="us-gaap_AuctionRateSecuritiesMember" order="1.0500" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain" xlink:to="vicr_BrokeredCertificatesOfDepositMember" order="1.0600" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain" xlink:to="us-gaap_CertificatesOfDepositMember" order="1.0700" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems" xlink:to="us-gaap_ScheduleOfAvailableForSaleSecuritiesTable" order="100.0000" xbrldt:closed="true" xbrldt:contextElement="segment" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems" xlink:to="us-gaap_AvailableForSaleSecuritiesAmortizedCost" order="1.0100" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems" xlink:to="vicr_AvailableForSaleSecuritiesGrossUnrealizedGainsAccumulatedInInvestments" order="1.0200" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems" xlink:to="vicr_AvailableForSaleSecuritiesGrossUnrealizedLossAccumulatedInInvestments" order="1.0300" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems" xlink:to="us-gaap_AvailableForSaleSecurities" order="1.0400" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_ScheduleOfAvailableForSaleSecuritiesTable" xlink:to="us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis" order="1.0000" priority="2" use="optional"/>
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/DisclosureShortTermAndLongTermInvestmentsAmortizedCostAndEstimatedFairValueOfAvailableforSaleSecurities">
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/DisclosureShortTermAndLongTermInvestmentsRollForwardOfCreditLossRecognizedInEarningsOnAvailableforSaleAuctionRateSecurities">
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/DisclosureFairValueMeasurementsAssetsMeasuredAtFairValueOnRecurringBasis">
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AuctionRateSecuritiesMember" xlink:label="us-gaap_AuctionRateSecuritiesMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AvailableForSaleSecurities" xlink:label="us-gaap_AvailableForSaleSecurities"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_BrokeredCertificatesOfDepositMember" xlink:label="vicr_BrokeredCertificatesOfDepositMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_CashAndCashEquivalentsAxis" xlink:label="us-gaap_CashAndCashEquivalentsAxis"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_CashAndCashEquivalentsFairValueDisclosure" xlink:label="us-gaap_CashAndCashEquivalentsFairValueDisclosure"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_CertificatesOfDepositMember" xlink:label="us-gaap_CertificatesOfDepositMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:label="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable" xlink:label="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:label="us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueByMeasurementFrequencyAxis" xlink:label="us-gaap_FairValueByMeasurementFrequencyAxis"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueInputsLevel1Member" xlink:label="us-gaap_FairValueInputsLevel1Member"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueInputsLevel2Member" xlink:label="us-gaap_FairValueInputsLevel2Member"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueInputsLevel3Member" xlink:label="us-gaap_FairValueInputsLevel3Member"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueMeasurementFrequencyDomain" xlink:label="us-gaap_FairValueMeasurementFrequencyDomain"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueMeasurementFrequencyDomain" xlink:label="us-gaap_FairValueMeasurementFrequencyDomain_2"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="us-gaap_FairValueMeasurementsFairValueHierarchyDomain_2"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueMeasurementsRecurringMember" xlink:label="us-gaap_FairValueMeasurementsRecurringMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis" xlink:label="us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain" xlink:label="us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain" xlink:label="us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain_2"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_MoneyMarketFundsMember" xlink:label="us-gaap_MoneyMarketFundsMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember" xlink:label="us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember" xlink:label="us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_2"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_ShortTermBrokeredCertificatesOfDepositMember" xlink:label="vicr_ShortTermBrokeredCertificatesOfDepositMember"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_CashAndCashEquivalentsAxis" xlink:to="us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_CashAndCashEquivalentsAxis" xlink:to="us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_2" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:to="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable" order="100.0000" xbrldt:closed="true" xbrldt:contextElement="segment" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:to="us-gaap_CashAndCashEquivalentsFairValueDisclosure" order="1.0600" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:to="us-gaap_AvailableForSaleSecurities" order="1.0700" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable" xlink:to="us-gaap_FairValueByMeasurementFrequencyAxis" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable" xlink:to="us-gaap_FairValueByFairValueHierarchyLevelAxis" order="2.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable" xlink:to="us-gaap_CashAndCashEquivalentsAxis" order="3.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable" xlink:to="us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis" order="4.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:to="us-gaap_FairValueMeasurementsFairValueHierarchyDomain" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:to="us-gaap_FairValueMeasurementsFairValueHierarchyDomain_2" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_FairValueByMeasurementFrequencyAxis" xlink:to="us-gaap_FairValueMeasurementFrequencyDomain" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_FairValueByMeasurementFrequencyAxis" xlink:to="us-gaap_FairValueMeasurementFrequencyDomain_2" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueMeasurementFrequencyDomain" xlink:to="us-gaap_FairValueMeasurementsRecurringMember" order="1.0500" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:to="us-gaap_FairValueInputsLevel1Member" order="1.0100" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:to="us-gaap_FairValueInputsLevel2Member" order="1.0200" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:to="us-gaap_FairValueInputsLevel3Member" order="1.0300" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis" xlink:to="us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis" xlink:to="us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain_2" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain" xlink:to="vicr_ShortTermBrokeredCertificatesOfDepositMember" order="1.0800" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain" xlink:to="us-gaap_AuctionRateSecuritiesMember" order="1.0900" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain" xlink:to="vicr_BrokeredCertificatesOfDepositMember" order="1.1000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain" xlink:to="us-gaap_CertificatesOfDepositMember" order="1.1100" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember" xlink:to="us-gaap_MoneyMarketFundsMember" order="1.0400" priority="2" use="optional"/>
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/DisclosureFairValueMeasurementsAdditionalInformation">
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/DisclosureFairValueMeasurementsQuantitativeInformationAboutLevel3FairValueMeasurements">
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AuctionRateSecuritiesMember" xlink:label="us-gaap_AuctionRateSecuritiesMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AvailableForSaleSecurities" xlink:label="us-gaap_AvailableForSaleSecurities"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_CumulativeProbabilityOfDefaultMember" xlink:label="vicr_CumulativeProbabilityOfDefaultMember"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_CumulativeProbabilityOfEarningMaximumRateUntilMaturityMember" xlink:label="vicr_CumulativeProbabilityOfEarningMaximumRateUntilMaturityMember"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_CumulativeProbabilityOfPrincipalReturnPriorToMaturityMember" xlink:label="vicr_CumulativeProbabilityOfPrincipalReturnPriorToMaturityMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain" xlink:label="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain" xlink:label="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_2"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueByAssetClassAxis" xlink:label="us-gaap_FairValueByAssetClassAxis"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:label="us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueByMeasurementBasisAxis" xlink:label="us-gaap_FairValueByMeasurementBasisAxis"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueDisclosureItemAmountsDomain" xlink:label="us-gaap_FairValueDisclosureItemAmountsDomain"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueDisclosureItemAmountsDomain" xlink:label="us-gaap_FairValueDisclosureItemAmountsDomain_2"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueInputsLevel3Member" xlink:label="us-gaap_FairValueInputsLevel3Member"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueMeasurementsValuationTechniques" xlink:label="us-gaap_FairValueMeasurementsValuationTechniques"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_FairValueMeasurementUnobservableInput" xlink:label="vicr_FairValueMeasurementUnobservableInput"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_FairValueOfAssetsAndLiabilitiesMeasuredOnNonRecurringBasisLineItems" xlink:label="vicr_FairValueOfAssetsAndLiabilitiesMeasuredOnNonRecurringBasisLineItems"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_LiquidityRiskPremiumMember" xlink:label="vicr_LiquidityRiskPremiumMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_MaximumMember" xlink:label="us-gaap_MaximumMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_MinimumMember" xlink:label="us-gaap_MinimumMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_RangeAxis" xlink:label="us-gaap_RangeAxis"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_RangeMember" xlink:label="us-gaap_RangeMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_RangeMember" xlink:label="us-gaap_RangeMember_2"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_RecoveryRateInDefaultMember" xlink:label="vicr_RecoveryRateInDefaultMember"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_WeightedAverageRateUseToMeasureFairValue" xlink:label="vicr_WeightedAverageRateUseToMeasureFairValue"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:to="us-gaap_RangeAxis" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:to="us-gaap_FairValueByAssetClassAxis" order="2.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:to="us-gaap_FairValueByFairValueHierarchyLevelAxis" order="3.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:to="us-gaap_FairValueByMeasurementBasisAxis" order="4.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain" xlink:to="us-gaap_AuctionRateSecuritiesMember" order="1.0400" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_FairValueByAssetClassAxis" xlink:to="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_FairValueByAssetClassAxis" xlink:to="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_2" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:to="us-gaap_FairValueMeasurementsFairValueHierarchyDomain" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_FairValueByMeasurementBasisAxis" xlink:to="us-gaap_FairValueDisclosureItemAmountsDomain" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_FairValueByMeasurementBasisAxis" xlink:to="us-gaap_FairValueDisclosureItemAmountsDomain_2" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueDisclosureItemAmountsDomain" xlink:to="vicr_CumulativeProbabilityOfEarningMaximumRateUntilMaturityMember" order="1.0500" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueDisclosureItemAmountsDomain" xlink:to="vicr_CumulativeProbabilityOfPrincipalReturnPriorToMaturityMember" order="1.0600" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueDisclosureItemAmountsDomain" xlink:to="vicr_CumulativeProbabilityOfDefaultMember" order="1.0700" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueDisclosureItemAmountsDomain" xlink:to="vicr_LiquidityRiskPremiumMember" order="1.0800" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueDisclosureItemAmountsDomain" xlink:to="vicr_RecoveryRateInDefaultMember" order="1.0900" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:to="us-gaap_FairValueInputsLevel3Member" order="1.0100" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="vicr_FairValueOfAssetsAndLiabilitiesMeasuredOnNonRecurringBasisLineItems" xlink:to="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" order="100.0000" xbrldt:closed="true" xbrldt:contextElement="segment" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="vicr_FairValueOfAssetsAndLiabilitiesMeasuredOnNonRecurringBasisLineItems" xlink:to="us-gaap_AvailableForSaleSecurities" order="1.1000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="vicr_FairValueOfAssetsAndLiabilitiesMeasuredOnNonRecurringBasisLineItems" xlink:to="us-gaap_FairValueMeasurementsValuationTechniques" order="1.1100" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="vicr_FairValueOfAssetsAndLiabilitiesMeasuredOnNonRecurringBasisLineItems" xlink:to="vicr_FairValueMeasurementUnobservableInput" order="1.1200" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="vicr_FairValueOfAssetsAndLiabilitiesMeasuredOnNonRecurringBasisLineItems" xlink:to="vicr_WeightedAverageRateUseToMeasureFairValue" order="1.1300" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_RangeAxis" xlink:to="us-gaap_RangeMember" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_RangeAxis" xlink:to="us-gaap_RangeMember_2" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RangeMember" xlink:to="us-gaap_MinimumMember" order="1.0200" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RangeMember" xlink:to="us-gaap_MaximumMember" order="1.0300" priority="2" use="optional"/>
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/DisclosureFairValueMeasurementsChangeInEstimatedFairValuesForAssetsValuedOnRecurringBasisUtilizingLevel3Inputs">
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/DisclosureInventoriesSummaryOfInventories">
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/DisclosurePropertyPlantAndEquipmentAdditionalInformation">
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_CapitalExpenditureCommitments" xlink:label="vicr_CapitalExpenditureCommitments"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_Depreciation" xlink:label="us-gaap_Depreciation"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_MaximumMember" xlink:label="us-gaap_MaximumMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_MinimumMember" xlink:label="us-gaap_MinimumMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_PropertyPlantAndEquipmentLineItems" xlink:label="us-gaap_PropertyPlantAndEquipmentLineItems"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_PropertyPlantAndEquipmentUsefulLife" xlink:label="us-gaap_PropertyPlantAndEquipmentUsefulLife"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_RangeAxis" xlink:label="us-gaap_RangeAxis"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_RangeMember" xlink:label="us-gaap_RangeMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable" xlink:label="us-gaap_ScheduleOfPropertyPlantAndEquipmentTable"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_PropertyPlantAndEquipmentLineItems" xlink:to="us-gaap_ScheduleOfPropertyPlantAndEquipmentTable" order="100.0000" xbrldt:closed="true" xbrldt:contextElement="segment" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_PropertyPlantAndEquipmentLineItems" xlink:to="us-gaap_PropertyPlantAndEquipmentUsefulLife" order="1.0100" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_PropertyPlantAndEquipmentLineItems" xlink:to="us-gaap_Depreciation" order="1.0200" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_PropertyPlantAndEquipmentLineItems" xlink:to="vicr_CapitalExpenditureCommitments" order="1.0300" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_RangeAxis" xlink:to="us-gaap_RangeMember" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RangeMember" xlink:to="us-gaap_MaximumMember" order="1.0400" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RangeMember" xlink:to="us-gaap_MinimumMember" order="1.0500" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_ScheduleOfPropertyPlantAndEquipmentTable" xlink:to="us-gaap_RangeAxis" order="1.0000" priority="2" use="optional"/>
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/DisclosurePropertyPlantAndEquipmentPropertyPlantAndEquipment">
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/DisclosureOtherInvestmentsAdditionalInformation">
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassificationOfVariableInterestEntityDomain" xlink:label="us-gaap_ClassificationOfVariableInterestEntityDomain"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassificationOfVariableInterestEntityDomain" xlink:label="us-gaap_ClassificationOfVariableInterestEntityDomain_2"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:label="us-gaap_ClassOfStockDomain"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ConvertiblePreferredStockMember" xlink:label="us-gaap_ConvertiblePreferredStockMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_DueToRelatedPartiesCurrentAndNoncurrent" xlink:label="us-gaap_DueToRelatedPartiesCurrentAndNoncurrent"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_EquityMethodInvestmentOwnershipPercentage" xlink:label="us-gaap_EquityMethodInvestmentOwnershipPercentage"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ScheduleOfVariableInterestEntitiesTable" xlink:label="us-gaap_ScheduleOfVariableInterestEntitiesTable"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StatementClassOfStockAxis" xlink:label="us-gaap_StatementClassOfStockAxis"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis" xlink:label="us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_VariableInterestEntityActivityBetweenVIEAndEntityOperatingIncomeOrLoss" xlink:label="us-gaap_VariableInterestEntityActivityBetweenVIEAndEntityOperatingIncomeOrLoss"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_VariableInterestEntityActivityBetweenVIEAndEntityPurchases" xlink:label="us-gaap_VariableInterestEntityActivityBetweenVIEAndEntityPurchases"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_VariableInterestEntityEntityMaximumLossExposureAmount" xlink:label="us-gaap_VariableInterestEntityEntityMaximumLossExposureAmount"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_VariableInterestEntityLineItems" xlink:label="us-gaap_VariableInterestEntityLineItems"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_VariableInterestEntityNotPrimaryBeneficiaryMember" xlink:label="us-gaap_VariableInterestEntityNotPrimaryBeneficiaryMember"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ClassificationOfVariableInterestEntityDomain" xlink:to="us-gaap_VariableInterestEntityNotPrimaryBeneficiaryMember" order="1.0600" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ClassOfStockDomain" xlink:to="us-gaap_ConvertiblePreferredStockMember" order="1.0700" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_ScheduleOfVariableInterestEntitiesTable" xlink:to="us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_ScheduleOfVariableInterestEntitiesTable" xlink:to="us-gaap_StatementClassOfStockAxis" order="2.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_StatementClassOfStockAxis" xlink:to="us-gaap_ClassOfStockDomain" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis" xlink:to="us-gaap_ClassificationOfVariableInterestEntityDomain" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis" xlink:to="us-gaap_ClassificationOfVariableInterestEntityDomain_2" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_VariableInterestEntityLineItems" xlink:to="us-gaap_ScheduleOfVariableInterestEntitiesTable" order="100.0000" xbrldt:closed="true" xbrldt:contextElement="segment" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_VariableInterestEntityLineItems" xlink:to="us-gaap_EquityMethodInvestmentOwnershipPercentage" order="1.0100" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_VariableInterestEntityLineItems" xlink:to="us-gaap_VariableInterestEntityEntityMaximumLossExposureAmount" order="1.0200" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_VariableInterestEntityLineItems" xlink:to="us-gaap_VariableInterestEntityActivityBetweenVIEAndEntityPurchases" order="1.0300" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_VariableInterestEntityLineItems" xlink:to="us-gaap_DueToRelatedPartiesCurrentAndNoncurrent" order="1.0400" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_VariableInterestEntityLineItems" xlink:to="us-gaap_VariableInterestEntityActivityBetweenVIEAndEntityOperatingIncomeOrLoss" order="1.0500" priority="2" use="optional"/>
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/DisclosureGoodwillAndOtherIntangibleAssetsAdditionalInformation">
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AmortizationOfIntangibleAssets" xlink:label="us-gaap_AmortizationOfIntangibleAssets"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths" xlink:label="us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFive" xlink:label="us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFive"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFour" xlink:label="us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFour"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearThree" xlink:label="us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearThree"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo" xlink:label="us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis" xlink:label="us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsLineItems" xlink:label="us-gaap_FiniteLivedIntangibleAssetsLineItems"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:label="us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:label="us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_2"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_GoodwillImpairmentLoss" xlink:label="us-gaap_GoodwillImpairmentLoss"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_PatentRenewalFees" xlink:label="vicr_PatentRenewalFees"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_PatentsMember" xlink:label="us-gaap_PatentsMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable" xlink:label="us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis" xlink:to="us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis" xlink:to="us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_2" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_FiniteLivedIntangibleAssetsLineItems" xlink:to="us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable" order="100.0000" xbrldt:closed="true" xbrldt:contextElement="segment" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FiniteLivedIntangibleAssetsLineItems" xlink:to="us-gaap_GoodwillImpairmentLoss" order="1.0100" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FiniteLivedIntangibleAssetsLineItems" xlink:to="vicr_PatentRenewalFees" order="1.0200" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FiniteLivedIntangibleAssetsLineItems" xlink:to="us-gaap_AmortizationOfIntangibleAssets" order="1.0300" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FiniteLivedIntangibleAssetsLineItems" xlink:to="us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths" order="1.0400" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FiniteLivedIntangibleAssetsLineItems" xlink:to="us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo" order="1.0500" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FiniteLivedIntangibleAssetsLineItems" xlink:to="us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearThree" order="1.0600" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FiniteLivedIntangibleAssetsLineItems" xlink:to="us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFour" order="1.0700" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FiniteLivedIntangibleAssetsLineItems" xlink:to="us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFive" order="1.0800" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:to="us-gaap_PatentsMember" order="1.0900" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable" xlink:to="us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis" order="1.0000" priority="2" use="optional"/>
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/DisclosureGoodwillAndOtherIntangibleAssetsScheduleOfPatentCostAndOtherAsset">
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization" xlink:label="us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis" xlink:label="us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsGross" xlink:label="us-gaap_FiniteLivedIntangibleAssetsGross"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsLineItems" xlink:label="us-gaap_FiniteLivedIntangibleAssetsLineItems"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:label="us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsNet" xlink:label="us-gaap_FiniteLivedIntangibleAssetsNet"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_PatentsMember" xlink:label="us-gaap_PatentsMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable" xlink:label="us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis" xlink:to="us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_FiniteLivedIntangibleAssetsLineItems" xlink:to="us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable" order="100.0000" xbrldt:closed="true" xbrldt:contextElement="segment" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FiniteLivedIntangibleAssetsLineItems" xlink:to="us-gaap_FiniteLivedIntangibleAssetsGross" order="1.0200" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FiniteLivedIntangibleAssetsLineItems" xlink:to="us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization" order="1.0300" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FiniteLivedIntangibleAssetsLineItems" xlink:to="us-gaap_FiniteLivedIntangibleAssetsNet" order="1.0400" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:to="us-gaap_PatentsMember" order="1.0100" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable" xlink:to="us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis" order="1.0000" priority="2" use="optional"/>
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/DisclosureSeveranceChargesAdditionalInformation">
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/DisclosureSeveranceChargesASummaryOfActivityRelatedToSeveranceCharges">
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_BbuMember" xlink:label="vicr_BbuMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_PaymentsForRestructuring" xlink:label="us-gaap_PaymentsForRestructuring"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_RestructuringReserveCurrent" xlink:label="us-gaap_RestructuringReserveCurrent"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable" xlink:label="us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_SegmentDomain" xlink:label="us-gaap_SegmentDomain"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_SeveranceAndOtherChargesLineItems" xlink:label="vicr_SeveranceAndOtherChargesLineItems"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_SeveranceCosts1" xlink:label="us-gaap_SeveranceCosts1"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis" xlink:label="us-gaap_StatementBusinessSegmentsAxis"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_ViChipMember" xlink:label="vicr_ViChipMember"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable" xlink:to="us-gaap_StatementBusinessSegmentsAxis" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_SegmentDomain" xlink:to="vicr_BbuMember" order="1.0100" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_SegmentDomain" xlink:to="vicr_ViChipMember" order="1.0200" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="vicr_SeveranceAndOtherChargesLineItems" xlink:to="us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable" order="100.0000" xbrldt:closed="true" xbrldt:contextElement="segment" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="vicr_SeveranceAndOtherChargesLineItems" xlink:to="us-gaap_RestructuringReserveCurrent" order="1.0300" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="vicr_SeveranceAndOtherChargesLineItems" xlink:to="us-gaap_SeveranceCosts1" order="1.0400" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="vicr_SeveranceAndOtherChargesLineItems" xlink:to="us-gaap_PaymentsForRestructuring" order="1.0500" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_StatementBusinessSegmentsAxis" xlink:to="us-gaap_SegmentDomain" order="1.0000" priority="2" use="optional"/>
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/DisclosureProductWarrantiesProductWarrantyActivity">
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/DisclosureStockholdersEquityAdditionalInformation">
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AwardTypeAxis" xlink:label="us-gaap_AwardTypeAxis"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_CashDividendsPaidToParentCompany" xlink:label="us-gaap_CashDividendsPaidToParentCompany"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:label="us-gaap_ClassOfStockDomain"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_CommonClassBMember" xlink:label="us-gaap_CommonClassBMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_CommonStockCapitalSharesReservedForFutureIssuance" xlink:label="us-gaap_CommonStockCapitalSharesReservedForFutureIssuance"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ConversionOfStockSharesConverted1" xlink:label="us-gaap_ConversionOfStockSharesConverted1"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_DividendPaidToShareholder" xlink:label="vicr_DividendPaidToShareholder"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_DividendsCash" xlink:label="us-gaap_DividendsCash"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_DividendsPayableAmountPerShare" xlink:label="us-gaap_DividendsPayableAmountPerShare"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2013/dei-2013-01-31.xsd#dei_EntityDomain" xlink:label="dei_EntityDomain"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2013/dei-2013-01-31.xsd#dei_LegalEntityAxis" xlink:label="dei_LegalEntityAxis"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_PaymentsOfDividendsMinorityInterest" xlink:label="us-gaap_PaymentsOfDividendsMinorityInterest"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:label="us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StatementClassOfStockAxis" xlink:label="us-gaap_StatementClassOfStockAxis"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised" xlink:label="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StockRepurchasedDuringPeriodShares" xlink:label="us-gaap_StockRepurchasedDuringPeriodShares"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StockRepurchasedDuringPeriodValue" xlink:label="us-gaap_StockRepurchasedDuringPeriodValue"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StockRepurchaseProgramAuthorizedAmount" xlink:label="us-gaap_StockRepurchaseProgramAuthorizedAmount"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount" xlink:label="us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_SubsidiariesMember" xlink:label="us-gaap_SubsidiariesMember"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_TenderOfferExpirationDate" xlink:label="vicr_TenderOfferExpirationDate"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_VicorStockOptionsMember" xlink:label="vicr_VicorStockOptionsMember"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_AwardTypeAxis" xlink:to="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ClassOfStockDomain" xlink:to="us-gaap_CommonClassBMember" order="1.1500" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_EntityDomain" xlink:to="us-gaap_SubsidiariesMember" order="1.1400" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="dei_LegalEntityAxis" xlink:to="dei_EntityDomain" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:to="us-gaap_AwardTypeAxis" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:to="dei_LegalEntityAxis" order="2.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:to="us-gaap_StatementClassOfStockAxis" order="3.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" order="100.0000" xbrldt:closed="true" xbrldt:contextElement="segment" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="us-gaap_StockRepurchasedDuringPeriodShares" order="1.0100" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="us-gaap_StockRepurchasedDuringPeriodValue" order="1.0200" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="vicr_TenderOfferExpirationDate" order="1.0300" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="us-gaap_StockRepurchaseProgramAuthorizedAmount" order="1.0400" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount" order="1.0500" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="us-gaap_DividendsPayableAmountPerShare" order="1.0600" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="vicr_DividendPaidToShareholder" order="1.0700" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="us-gaap_DividendsCash" order="1.0800" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="us-gaap_CashDividendsPaidToParentCompany" order="1.0900" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="us-gaap_PaymentsOfDividendsMinorityInterest" order="1.1000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised" order="1.1100" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="us-gaap_ConversionOfStockSharesConverted1" order="1.1200" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="us-gaap_CommonStockCapitalSharesReservedForFutureIssuance" order="1.1300" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="vicr_VicorStockOptionsMember" order="1.1600" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_StatementClassOfStockAxis" xlink:to="us-gaap_ClassOfStockDomain" order="1.0000" priority="2" use="optional"/>
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/DisclosureOtherIncomeNetComponentsOfOtherIncome">
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/DisclosureIncomeTaxesScheduleOfReconciliationOfFederalStatutoryRateToEffectiveIncomeTaxRate">
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/DisclosureIncomeTaxesAdditionalInformation">
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_DeferredTaxAssetsLiabilitiesLineItems" xlink:label="vicr_DeferredTaxAssetsLiabilitiesLineItems"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_DeferredTaxAssetsLiabilitiesTable" xlink:label="vicr_DeferredTaxAssetsLiabilitiesTable"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_DeferredTaxAssetsValuationAllowance" xlink:label="us-gaap_DeferredTaxAssetsValuationAllowance"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_DeferredTaxAssetsValuationAllowanceIncrease" xlink:label="vicr_DeferredTaxAssetsValuationAllowanceIncrease"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_DeferredTaxLiabilityNotRecognizedAmountOfUnrecognizedDeferredTaxLiabilityUndistributedEarningsOfForeignSubsidiaries" xlink:label="us-gaap_DeferredTaxLiabilityNotRecognizedAmountOfUnrecognizedDeferredTaxLiabilityUndistributedEarningsOfForeignSubsidiaries"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_DomesticCountryMember" xlink:label="us-gaap_DomesticCountryMember"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_EquityImpactDueToRealizationOfDeferredTaxAssets" xlink:label="vicr_EquityImpactDueToRealizationOfDeferredTaxAssets"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_FederalNetOperatingLossCarryforwardsExpirationYear" xlink:label="vicr_FederalNetOperatingLossCarryforwardsExpirationYear"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_IncomeTaxAuthorityAxis" xlink:label="us-gaap_IncomeTaxAuthorityAxis"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_IncomeTaxAuthorityDomain" xlink:label="us-gaap_IncomeTaxAuthorityDomain"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_IncomeTaxAuthorityDomain" xlink:label="us-gaap_IncomeTaxAuthorityDomain_2"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_IncomeTaxExaminationPeriod1" xlink:label="vicr_IncomeTaxExaminationPeriod1"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_IncomeTaxReceivable" xlink:label="us-gaap_IncomeTaxReceivable"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_MaximumMember" xlink:label="us-gaap_MaximumMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_MinimumMember" xlink:label="us-gaap_MinimumMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_RangeAxis" xlink:label="us-gaap_RangeAxis"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_RangeMember" xlink:label="us-gaap_RangeMember"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_ResearchTaxCreditCarryforwardExtensionPeriod" xlink:label="vicr_ResearchTaxCreditCarryforwardExtensionPeriod"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_TaxCreditCarryforwardDeferredTaxAsset" xlink:label="us-gaap_TaxCreditCarryforwardDeferredTaxAsset"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_UndistributedEarningsOfForeignSubsidiaries" xlink:label="us-gaap_UndistributedEarningsOfForeignSubsidiaries"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_UnrecognizedTaxBenefits" xlink:label="us-gaap_UnrecognizedTaxBenefits"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_UnrecognizedTaxBenefitsInterestOnIncomeTaxesAccrued" xlink:label="us-gaap_UnrecognizedTaxBenefitsInterestOnIncomeTaxesAccrued"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_UnrecognizedTaxBenefitsInterestOnIncomeTaxesExpense" xlink:label="us-gaap_UnrecognizedTaxBenefitsInterestOnIncomeTaxesExpense"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="vicr_DeferredTaxAssetsLiabilitiesLineItems" xlink:to="vicr_DeferredTaxAssetsLiabilitiesTable" order="100.0000" xbrldt:closed="true" xbrldt:contextElement="segment" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="vicr_DeferredTaxAssetsLiabilitiesLineItems" xlink:to="us-gaap_DeferredTaxAssetsValuationAllowance" order="1.0100" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="vicr_DeferredTaxAssetsLiabilitiesLineItems" xlink:to="vicr_DeferredTaxAssetsValuationAllowanceIncrease" order="1.0200" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="vicr_DeferredTaxAssetsLiabilitiesLineItems" xlink:to="us-gaap_IncomeTaxReceivable" order="1.0300" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="vicr_DeferredTaxAssetsLiabilitiesLineItems" xlink:to="vicr_EquityImpactDueToRealizationOfDeferredTaxAssets" order="1.0400" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="vicr_DeferredTaxAssetsLiabilitiesLineItems" xlink:to="us-gaap_UndistributedEarningsOfForeignSubsidiaries" order="1.0500" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="vicr_DeferredTaxAssetsLiabilitiesLineItems" xlink:to="us-gaap_DeferredTaxLiabilityNotRecognizedAmountOfUnrecognizedDeferredTaxLiabilityUndistributedEarningsOfForeignSubsidiaries" order="1.0600" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="vicr_DeferredTaxAssetsLiabilitiesLineItems" xlink:to="vicr_ResearchTaxCreditCarryforwardExtensionPeriod" order="1.0700" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="vicr_DeferredTaxAssetsLiabilitiesLineItems" xlink:to="us-gaap_TaxCreditCarryforwardDeferredTaxAsset" order="1.0800" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="vicr_DeferredTaxAssetsLiabilitiesLineItems" xlink:to="vicr_FederalNetOperatingLossCarryforwardsExpirationYear" order="1.0900" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="vicr_DeferredTaxAssetsLiabilitiesLineItems" xlink:to="us-gaap_UnrecognizedTaxBenefits" order="1.1000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="vicr_DeferredTaxAssetsLiabilitiesLineItems" xlink:to="us-gaap_UnrecognizedTaxBenefitsInterestOnIncomeTaxesAccrued" order="1.1100" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="vicr_DeferredTaxAssetsLiabilitiesLineItems" xlink:to="us-gaap_UnrecognizedTaxBenefitsInterestOnIncomeTaxesExpense" order="1.1200" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="vicr_DeferredTaxAssetsLiabilitiesLineItems" xlink:to="vicr_IncomeTaxExaminationPeriod1" order="1.1300" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="vicr_DeferredTaxAssetsLiabilitiesTable" xlink:to="us-gaap_IncomeTaxAuthorityAxis" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="vicr_DeferredTaxAssetsLiabilitiesTable" xlink:to="us-gaap_RangeAxis" order="2.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_IncomeTaxAuthorityAxis" xlink:to="us-gaap_IncomeTaxAuthorityDomain" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_IncomeTaxAuthorityAxis" xlink:to="us-gaap_IncomeTaxAuthorityDomain_2" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_IncomeTaxAuthorityDomain" xlink:to="us-gaap_DomesticCountryMember" order="1.1400" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_RangeAxis" xlink:to="us-gaap_RangeMember" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RangeMember" xlink:to="us-gaap_MinimumMember" order="1.1500" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RangeMember" xlink:to="us-gaap_MaximumMember" order="1.1600" priority="2" use="optional"/>
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/DisclosureIncomeTaxesScheduleOfDomesticAndForeignComponentsOfIncomeLossBeforeIncomeTaxes">
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/DisclosureIncomeTaxesScheduleOfComponentsOfProvisionBenefitForIncomeTaxes">
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/DisclosureIncomeTaxesScheduleOfSignificantComponentsOfDeferredTaxAssetsAndLiabilities">
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/DisclosureIncomeTaxesScheduleOfReconciliationOfBeginningAndEndingAmountOfUnrecognizedTaxBenefits">
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/DisclosureCommitmentsAndContingenciesSummaryOfFutureMinimumRentalCommitmentsUnderNonCancelableOperatingLeases">
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/DisclosureCommitmentsAndContingenciesAdditionalInformation">
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/DisclosureSegmentInformationAdditionalInformation">
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/DisclosureSegmentInformationSignificantSegmentFinancialData">
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_Assets" xlink:label="us-gaap_Assets"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_BbuMember" xlink:label="vicr_BbuMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ConsolidationItemsAxis" xlink:label="us-gaap_ConsolidationItemsAxis"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ConsolidationItemsDomain" xlink:label="us-gaap_ConsolidationItemsDomain"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ConsolidationItemsDomain" xlink:label="us-gaap_ConsolidationItemsDomain_2"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_CorporateMember" xlink:label="us-gaap_CorporateMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_DepreciationDepletionAndAmortization" xlink:label="us-gaap_DepreciationDepletionAndAmortization"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_IntersegmentEliminationMember" xlink:label="us-gaap_IntersegmentEliminationMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_OperatingIncomeLoss" xlink:label="us-gaap_OperatingIncomeLoss"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_OperatingSegmentsMember" xlink:label="us-gaap_OperatingSegmentsMember"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_PicorMember" xlink:label="vicr_PicorMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_SalesRevenueNet" xlink:label="us-gaap_SalesRevenueNet"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable" xlink:label="us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_SegmentDomain" xlink:label="us-gaap_SegmentDomain"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_SegmentDomain" xlink:label="us-gaap_SegmentDomain_2"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_SegmentReportingInformationLineItems" xlink:label="us-gaap_SegmentReportingInformationLineItems"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis" xlink:label="us-gaap_StatementBusinessSegmentsAxis"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_ViChipMember" xlink:label="vicr_ViChipMember"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_ConsolidationItemsAxis" xlink:to="us-gaap_ConsolidationItemsDomain" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_ConsolidationItemsAxis" xlink:to="us-gaap_ConsolidationItemsDomain_2" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ConsolidationItemsDomain" xlink:to="us-gaap_OperatingSegmentsMember" order="1.0100" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ConsolidationItemsDomain" xlink:to="us-gaap_IntersegmentEliminationMember" order="1.0200" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable" xlink:to="us-gaap_ConsolidationItemsAxis" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable" xlink:to="us-gaap_StatementBusinessSegmentsAxis" order="2.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_SegmentDomain" xlink:to="vicr_BbuMember" order="1.0700" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_SegmentDomain" xlink:to="vicr_ViChipMember" order="1.0800" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_SegmentDomain" xlink:to="vicr_PicorMember" order="1.0900" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_SegmentDomain" xlink:to="us-gaap_CorporateMember" order="1.1000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_SegmentReportingInformationLineItems" xlink:to="us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable" order="100.0000" xbrldt:closed="true" xbrldt:contextElement="segment" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_SegmentReportingInformationLineItems" xlink:to="us-gaap_SalesRevenueNet" order="1.0300" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_SegmentReportingInformationLineItems" xlink:to="us-gaap_OperatingIncomeLoss" order="1.0400" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_SegmentReportingInformationLineItems" xlink:to="us-gaap_Assets" order="1.0500" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_SegmentReportingInformationLineItems" xlink:to="us-gaap_DepreciationDepletionAndAmortization" order="1.0600" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_StatementBusinessSegmentsAxis" xlink:to="us-gaap_SegmentDomain" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_StatementBusinessSegmentsAxis" xlink:to="us-gaap_SegmentDomain_2" order="1.0000" priority="2" use="optional"/>
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/DisclosureQuarterlyResultsOfOperationsUnauditedSummaryOfUnauditedQuarterlyFinancialData">
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/DisclosureQuarterlyResultsOfOperationsUnauditedAdditionalInformation">
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/DisclosureScheduleIIValuationAndQualifyingAccounts">
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AllowanceForDoubtfulAccountsMember" xlink:label="us-gaap_AllowanceForDoubtfulAccountsMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ValuationAllowancesAndReservesBalance" xlink:label="us-gaap_ValuationAllowancesAndReservesBalance"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ValuationAllowancesAndReservesChargedToCostAndExpense" xlink:label="us-gaap_ValuationAllowancesAndReservesChargedToCostAndExpense"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ValuationAllowancesAndReservesDeductions" xlink:label="us-gaap_ValuationAllowancesAndReservesDeductions"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ValuationAllowancesAndReservesDomain" xlink:label="us-gaap_ValuationAllowancesAndReservesDomain"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ValuationAllowancesAndReservesDomain" xlink:label="us-gaap_ValuationAllowancesAndReservesDomain_2"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ValuationAllowancesAndReservesTypeAxis" xlink:label="us-gaap_ValuationAllowancesAndReservesTypeAxis"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ValuationAndQualifyingAccountsDisclosureLineItems" xlink:label="us-gaap_ValuationAndQualifyingAccountsDisclosureLineItems"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ValuationAndQualifyingAccountsDisclosureTable" xlink:label="us-gaap_ValuationAndQualifyingAccountsDisclosureTable"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ValuationAllowancesAndReservesDomain" xlink:to="us-gaap_AllowanceForDoubtfulAccountsMember" order="1.0500" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_ValuationAllowancesAndReservesTypeAxis" xlink:to="us-gaap_ValuationAllowancesAndReservesDomain" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_ValuationAllowancesAndReservesTypeAxis" xlink:to="us-gaap_ValuationAllowancesAndReservesDomain_2" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_ValuationAndQualifyingAccountsDisclosureLineItems" xlink:to="us-gaap_ValuationAndQualifyingAccountsDisclosureTable" order="100.0000" xbrldt:closed="true" xbrldt:contextElement="segment" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ValuationAndQualifyingAccountsDisclosureLineItems" xlink:to="us-gaap_ValuationAllowancesAndReservesBalance" order="1.0100" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ValuationAndQualifyingAccountsDisclosureLineItems" xlink:to="us-gaap_ValuationAllowancesAndReservesChargedToCostAndExpense" order="1.0200" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ValuationAndQualifyingAccountsDisclosureLineItems" xlink:to="us-gaap_ValuationAllowancesAndReservesDeductions" order="1.0300" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_ValuationAndQualifyingAccountsDisclosureTable" xlink:to="us-gaap_ValuationAllowancesAndReservesTypeAxis" order="1.0000" priority="2" use="optional"/>
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsOrganizationConsolidationAndPresentationOfFinancialStatementsDisclosureTextBlock">
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsSignificantAccountingPoliciesTextBlock">
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsSignificantAccountingPoliciesTextBlockPolicies">
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsSignificantAccountingPoliciesTextBlockTables">
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfCompensationRelatedCostsShareBasedPaymentsTextBlock">
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfCompensationRelatedCostsShareBasedPaymentsTextBlockTables">
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_PicorPlanMember" xlink:label="vicr_PicorPlanMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_PlanNameAxis" xlink:label="us-gaap_PlanNameAxis"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_PlanNameDomain" xlink:label="us-gaap_PlanNameDomain"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationStockOptionsActivityTableTextBlock" xlink:label="us-gaap_ScheduleOfShareBasedCompensationStockOptionsActivityTableTextBlock"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ScheduleOfShareBasedPaymentAwardStockOptionsValuationAssumptionsTableTextBlock" xlink:label="us-gaap_ScheduleOfShareBasedPaymentAwardStockOptionsValuationAssumptionsTableTextBlock"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StatementLineItems" xlink:label="us-gaap_StatementLineItems"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StatementTable" xlink:label="us-gaap_StatementTable"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_ViChipPlanMember" xlink:label="vicr_ViChipPlanMember"/>
    <loc xlink:type="locator" xlink:href="vicr-20131231.xsd#vicr_VicorPlanMember" xlink:label="vicr_VicorPlanMember"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_PlanNameAxis" xlink:to="us-gaap_PlanNameDomain" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_PlanNameDomain" xlink:to="vicr_VicorPlanMember" order="1.0300" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_PlanNameDomain" xlink:to="vicr_PicorPlanMember" order="1.0400" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_PlanNameDomain" xlink:to="vicr_ViChipPlanMember" order="1.0500" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StatementTable" order="100.0000" xbrldt:closed="true" xbrldt:contextElement="segment" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_ScheduleOfShareBasedCompensationStockOptionsActivityTableTextBlock" order="1.0100" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_ScheduleOfShareBasedPaymentAwardStockOptionsValuationAssumptionsTableTextBlock" order="1.0200" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_PlanNameAxis" order="1.0000" priority="2" use="optional"/>
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsInvestmentsInDebtAndMarketableEquitySecuritiesAndCertainTradingAssetsDisclosureTextBlock">
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsInvestmentsInDebtAndMarketableEquitySecuritiesAndCertainTradingAssetsDisclosureTextBlockTables">
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsFairValueDisclosuresTextBlock">
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsFairValueDisclosuresTextBlockTables">
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsInventoryDisclosureTextBlock">
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsInventoryDisclosureTextBlockTables">
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsPropertyPlantAndEquipmentDisclosureTextBlock">
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsPropertyPlantAndEquipmentDisclosureTextBlockTables">
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsOtherInvestmentsTextBlock">
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsGoodwillAndIntangibleAssetsDisclosureTextBlock">
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsGoodwillAndIntangibleAssetsDisclosureTextBlockTables">
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis" xlink:label="us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:label="us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_PatentsMember" xlink:label="us-gaap_PatentsMember"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTableTextBlock" xlink:label="us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTableTextBlock"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StatementLineItems" xlink:label="us-gaap_StatementLineItems"/>
    <loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StatementTable" xlink:label="us-gaap_StatementTable"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis" xlink:to="us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain" order="1.0000" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:to="us-gaap_PatentsMember" order="1.0200" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StatementTable" order="100.0000" xbrldt:closed="true" xbrldt:contextElement="segment" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTableTextBlock" order="1.0100" priority="2" use="optional"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis" order="1.0000" priority="2" use="optional"/>
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsRestructuringAndRelatedActivitiesDisclosureTextBlock">
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsRestructuringAndRelatedActivitiesDisclosureTextBlockTables">
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsProductWarrantyDisclosureTextBlock">
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsProductWarrantyDisclosureTextBlockTables">
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsStockholdersEquityNoteDisclosureTextBlock">
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsOtherIncomeAndOtherExpenseDisclosureTextBlock">
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsOtherIncomeAndOtherExpenseDisclosureTextBlockTables">
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsIncomeTaxDisclosureTextBlock">
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsIncomeTaxDisclosureTextBlockTables">
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsCommitmentsAndContingenciesDisclosureTextBlock">
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsCommitmentsAndContingenciesDisclosureTextBlockTables">
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsSegmentReportingDisclosureTextBlock">
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsSegmentReportingDisclosureTextBlockTables">
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsQuarterlyFinancialInformationTextBlock">
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsQuarterlyFinancialInformationTextBlockTables">
  </definitionLink>
  <definitionLink xlink:type="extended" xlink:role="http://vicorpower.com/taxonomy/role/NotesToFinancialStatementsScheduleOfValuationAndQualifyingAccountsDisclosureTextBlock">
  </definitionLink>
</linkbase>
