1144310298--IGBT驱动电路设计精髓

1SnubbernetworksforIGBTs2MotivationWhylowinductiveDC-linkdesign?DuetostrayinductancesintheDClink,voltageovershootsoccurduringswitchoffoftheIGBT:ThesevoltageovershootsmaydestroytheIGBTmodulebecausetheyareaddedtotheDC-linkvoltageandmayleadtoVCEVCEmaxWithlowinductiveDC-Linkdesign(smallLstray)thesevoltageovershootscanbereducedsignificantly.dtdiLvstrayovershootlinkDCovershootCEvvv3LowInductanceDC-linkDesignThemechanicaldesignhasasignificantinfluenceonthestrayinductanceoftheDC-linkTheconductorsmustbeparalleledLstray=100%Lstray20%4LowInductanceDC-linkDesignThemechanicaldesignhasasignificantinfluenceonthestrayinductanceoftheDC-linkTheconnectionsmustbeinlinewiththemaincurrentflowLstray=100%Lstray=30%5LowInductanceDC-linkDesignThemechanicaldesignhasasignificantinfluenceonthestrayinductanceoftheDC-linkAlsotheorientationmustbetakenintoregard+-+-Lstray=100%Lstray=80%6LowInductanceDC-linkDesignThemechanicaldesignhasasignificantinfluenceonthestrayinductanceoftheDC-linkAparallelingofthecapacitorsreducestheinductancefurtherLstray=100%Lstray=50%7-+-+-+-+-+-+IGBTModulsCapacitorLowinductivesolutionLowInductanceDC-linkDesignComparisonofdifferentdesignsTwocapacitorsinseriesTwoserialcapacitorsinparallel-+-+-+-+-+-+IGBTModulsCapacitor++--+++Typicalsolution8“Lowcost”solutionForparallelingstandardmodulesaminimumrequirementisaDC-linkdesignwithtwoparalleledbarsLowInductanceDC-linkDesign9LowInductanceDC-linkCapacitorsAlsothecapacitorshavetobedecidedCapacitorswithdifferentinternalstrayinductanceareavailableChooseacapacitorwithverylowstrayinductance!Lstray=?Askyoursupplier!10MotivationWhyuseasnubber?DuetostrayinductancesintheDClink,voltageovershootsoccurduringswitchoffoftheIGBT:ThesevoltageovershootsmaydestroytheIGBTmodulebecausetheyareaddedtotheDC-linkvoltageandmayleadtoVCEVCEmaxThesnubberworksasalowpassfilterand“takesover”thevoltageovershootdtdiLvstrayovershootlinkDCovershootCEvvv11SnubberNetworksSEMIKRONrecommendsforIGBTapplications:FastandhighvoltagesnubbercapacitorparalleltotheDClinkNottoincreaseLstray,thesnubbermustbelocatedveryclosetotheIGBTmodule12NotSufficientSnubberCapacitorsButstill:thesnubbernetworksneedtobeoptimisedThewrongsnubberdoesnotreducethevoltageovershootsTogetherwiththestrayinductanceoftheDC-linkoscillationscanoccurIGBTswitchoff(raiseofVCE)beforeoptimisationVoltageovershootOscillation13NotSufficientSnubberCapacitorsThesecapacitorsdidnotworksatisfactoryassnubber:14AvailableSnubberCapacitorsFromdifferentsuppliersdifferentsnubbercapacitorsareavailable.Ina“trialanderror”processtheoptimumcanbefind,basedonmeasurements.15OptimalSnubberCapacitorAfteroptimisation:SignificantlyreducedvoltageovershootsNooscillationsIGBTswitchoff(raiseofVCE)afteroptimisationVoltageovershootNooscillation16SnubbernetworksforIGBTs17Calculationofasnubbercapacitor18ConclusionWhenusinglatestgenerationsofIGBTmodulesitisrecommendedandadvantageoustoDoalowinductive(“sandwich”)DC-linkdesignDecideforlowinductiveDC-linkcapacitorsOptimisethesnubbercircuitDealingwithIGBTModules