电磁炉有关IGBT的翻译.docx
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电磁炉有关IGBT的翻译.docx
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电磁炉有关IGBT的翻译
电磁炉有关IGBT的翻译
IGBTSelectionMethodfortheDesignofResonantInvertersforDomesticInductionHeating
Abstract
Thepowertransistor(IGBT)isoneofthemostimportantcomponentsoftheinverterofdomesticinductioncookers.Forthisapplicationthemaximumjunctiontemperature(Tjmax)oftheIGBTisoneofthemostcriticaldesignparametersbecausethecookerhastodecreasetheoutputpowerwhenthejunctiontemperatureisneartoTjmaxofthedevice.Thejunctiontemperature(Tj)oftheIGBTprincipallydependsonthepowerlosses.ThispaperproposesamethodtochoosetheIGBTbasedonthecalculationofthetemperaturevariationΔTjafromthepowerlosses.
Nowadays,IGBTbehaviourisatrade-offbetweenconductionandswitchingperformance,soitisnecessarytomeasuretheIGBTpowerlossesseparately.ThispaperproposesamethodtomeasurethepowerlossesseparatelybasedonelectricalmeasurementandtheIGBTconductioncharacteristics.Moreoveritisproposedacriteriontodeterminatethelimitsofthepowerlossesbasedoneliminatetheoffsetofdevicevoltageandtheswitchingareaisdefinedfromthevoltageisover2.5Vtothecurrentiszero.
Finally,theproposedmethodhasbeenappliedtofivedifferentIGBTsfordifferentlevelsofpowerandwithtwostandardpanswithanelectronicboardofacommercialcookerMoreoverthismethodhasbeenverifiedwithathermograficcameraobtainingsimilarresults.
Introduction
Domesticinductioncookerstaketheenergyfromthemainsvoltage,whichisrectifiedandfiltered.Thentheresonantinvertersupplieshigh-frequencycurrenttotheinductioncoil.Thehalf-bridgeseriesresonantinverter(Fig.1(a))isthemostusedduetotheelectricalrequirementsofitscomponents,itssimplicityanditscost-effectiveness[1].Theresonantloadconsistsofthepanandtheinductioncoil.Theircouplingismodelledastheseriesconnectionofaninductorandaresistor,basedonthetransformeranalogy[2].
Domesticinductioncookersenabletoheatthepaninapowerrangebetween3300Wand50W.ThemodulationstrategiestypicallyusedindomesticinductionheatingaretheSquareWave(SW)controlandtheAsymmetricalDutyCycle(ADC)controlforthehighpowerrangeandthePulseDensityModulation(PDM)[3]forthelowpowerrange.
Oneofthemostimportantcomponentsofdomesticinductioncookersisthepowertransistor;usuallyitisanIGBTforitsconductionandswitchingcharacteristics.Forthisapplicationthemaximumjunctiontemperature(Tjmax)oftheIGBTisoneofthemostcriticaldesignparametersbecausethecookerhastodecreasetheoutputpowerwhenTjisneartoTjmaxofthedevice.Thisreductionoftheoutputpowerisnotdesirableforthisapplication,sotheoptimumIGBTisthatoneminimizesthisreductionofpower
Thejunctiontemperature(Tj)oftheIGBTdependsonthepowerlosses,thecoolingsystem,thethermalcharacteristicsofthedeviceandtheenvironmenttemperature(Ta).Therefrigerationsystemconsistsoftheisolationfoil,theheatsinkandthefanandithassomedesignlimitations.Theextrudedheatsinkislimitedbythereduceddimensionsofthecookerandthefanspeedislimitedfortheacousticnoiselevel.Theenvironmenttemperaturedependsontheinstallationandmainlyifthereisanovenbelowthecookerbecausethistemperaturecouldreach80ºC.Thedevicepowerlossescanbeseparatedinconductionandswitchinglossesandtheycanbeminimizedwiththeappropriatemodulationstrategy[4-5]andIGBT.Nowadays,IGBTbehaviourisatrade-offbetweenconductionandswitchingperformance,soitisnecessarytomeasurethelossesseparately.Fig.1(b)showsthetendencyofthecurrenttechnologylimitsforthiskindofdevice.ThemainparameterforconductionlossesistheSaturationVoltage(VCESAT)andforswitchinglossesistheSwitch-offEnergy(Eoff).Theprincipalthermalcharacteristicsofthedeviceareitsthermalresistancesandthemaximumjunctiontemperature.InthispaperitispresentedamethodtochoosetheIGBTbythecalculationofthetemperaturevariationbetweenthejunctionofthedeviceandtheenvironment(ΔTja)fromthemeasurementofthepowerlosses.
Methodtomeasurethepowerlosses
Commercialpoweranalyzersandthermalmethodsonlycanmeasurethetotalpowerlosses.Inthispaperisproposedamethodbasedonelectricalmeasurements.Themaindifferencebetweentheproposedmethodandothersworksisthecriteriontoseparateconductionandswitchinglosses.Othersworksproposecriteriabasedonapercentageofthedevicevoltage(vCE)[6-7]orbasedontheslopeofthedevicecurrent(ic)[8].Inthispaper,itisproposedthattheswitchingareabeginswhenthevCEminusthevoltageoffset(Voffset)isover2.5V(selectedtotakeaccountofvoltagesignalnoise)anditfinisheswhenthecurrentiszero(Fig.2).ThevoltageVoffsetistheaverageofvCEduringtheperiodbetweenthediodeturn-offandthebeginningoftheswitchingarea.TheIGBTconductionlossesareconsideredfromthediodeturn-offtotheendofthe“tailcurrent”.ThereasontochoosethiscriterionisthattheconventionaldifferentialprobesdonothaveenoughsensitivitytomeasuretheIGBTconductionvoltage(vCE,ONIGBT)andtheoffsetoftheseprobescanbehigherthanvCE,ONIGBT.Moreover,thiscriterionisindependentofthemaximumdevicevoltageandthemeasurementsystem.
A.Conductionpowerlosses.
Conductionlosses(Pon)canbeseparateintoIGBTanddiodelosses(Fig.2).Bothlossescanbemodelledastheseriesconnectionofaresistance(Ron)andavoltagesource(Von)[9].Thus,powerlossesarecalculatedasfollows
whereIandIrmsaretheaverageandrmscurrentsduringtheconductionofthedevice.The
manufacturerofthedeviceprovidesacurveforthediodeandtheIGBTwhereitcanbecalculatedRonandVonaccordingtothedevicetemperature(Fig.3).Thiscurvealsocanbeobtainedwithacurvetracer.Sotocalculatetheconductionpowerlossesitisnecessarytomeasureonlythedevicecurrent.
B.Switchingpowerlosses.
Switchinglosses(Psw)areproducedintheIGBTturn-off.Itcanbeseparatedintotwodifferentareas:
dV/dtandtailcurrentareas,asitisshowninFig.2.Themostsignificantpartofswitchinglossesareproducedinthetailcurrentarea,becausethelossesproducedinthedV/dtareacanbereducedwiththeappropriatesnubbernetwork.Traditionallytheswitchinglosseshavebeencalculatedassumingthatthedevicecurrentandvoltagearelinearatturn-off[10].Thismethodhastheproblemthatthe“tailcurrent”isnottakenintoaccount,soitisnecessarytoestimatetheswitchingcharacteristicsofthedevice.InthispaperthemethodproposedtomeasuretheswitchinglossesisbasedonmeasuringthedevicecurrentandvoltageduringtheIGBTturn-off,soPswiscalculatedas
wheretturn-offisdefinedwiththeproposedcriterion,vCEismeasuredwithaconventionaldifferentialvoltageprobeandicismeasuredwithaRogowskicurrentprobe(Fig.4(a)).TheprincipalcharacteristicsoftheRogowskiprobearethatitisnotnecessarytomodifythecircuitbecausethecoilofthisprobecanbeopen(Fig.4(b))anditishighlylinearduetoithasnoironcoretosaturate.
Thermalanalysis
Theprincipalcomponentstobeaccountinthethermalanalysisaretheswitchingdevices,theisolationfoils,theheatsinkandthefan.TheequivalentthermalcircuitisshowninFig.5.
Fig.5showsthatthetemperaturevariationbetweenjunctiontemperatureandenvironment
temperature(ΔTja)forasymmetricalmodulationstrategycanbecalculatedas
whereRjcIGBTandRjcDiodeareprovidedbythedevicemanufacturerandRchisthethermalresistanceoftheisolationfoilanditsvalueis0.3ºC/W.ThethermalresistanceoftheheatsinkisRhaanditsvaluedependsonthefanspeed,suchasitsvalueis0.9ºC/Wforthemaximumspeed.ThepowerlossesPIGBTarethesumofthePonIGBTandthePswandPDiodeisthePonDiode.ThepowerlossesPtotandPHBaredefinedinFig.5.Moreover,Fig.5showsthatTjisthemaximumvalueofTjIGBTandTjDiode,forthisreasonitisnecessarytomeasurethepowerlossesoftheIGBTanddiodeseparately,usuallyTjIGBTisthehighest.
Experimentalresults
TheproposedmethodhasbeenappliedtofivedifferentIGBTs(A-E)withanelectronicboardofacommercialcooker(Fig.6).TheIGBTDistheIGBTusedinthecooker.TheIGBTApresentsagoodswitchingperformance,whiletheIGBTBpresentsagoodconductionperformanceanditsTjmaxisthehighest.TheIGBTChasthelowestRjcIGBTandIGBTEhasalowerprice.ThesefiveIGBTshadbeentestedfordifferentlevelsofpowerandwithtwostandardpans:
HACKMANandZENITH.
A.Experimentalcomparisonofpowerlosses
Fig.7showsthatthepowerlosseswiththepanHACKMANarehigherthanthelosseswiththepanZENITH,duetotheinverteroperatesnearerresonancewiththepanZENITHthanwiththepanHACKMAN.SotheworstcaseistheoperatingwiththepanHACKMANandanoutputpowerof2300W.MoreoveritcanbeobservedthatIGBTsA,BandCachievelowerlossesthantheIGBTsDandE.TheIGBTBhasthelowestconductionlossesandtheIGBTAhasthelowestswitchinglosses,whiletheirtotalpowerlossesaresimilar.
B.ExperimentalcomparisonoftemperaturevariationΔTja
Fig.8(a)showstheexperimentaltemperaturevariationΔTjameasuredwiththeproposedmethodforthefiveIGBTs,anoutputpowerof2300Wandtwopans.Fig.8(a)showsthatthetemperaturevariationΔTjaoftheIGBTsA,BandCarelowerthanthevariationoftheIGBTsDandE.Asresult,consideringTjmaxofthedevices,theIGBTBpresentsthebestperformanceforthedomesticinductionheating.ConsideringaTa=
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