LLC-resonant-converter-by-BO-YANG

TopologyInvestigationforFrontEndDC/DCPowerConversionforDistributedPowerSystemBoYangDissertationsubmittedtotheFacultyoftheVirginiaPolytechnicInstituteandStateUniversityinpartialfulfillmentoftherequirementsforthedegreeofDoctorofPhilosophyinElectricalEngineeringFredC.Lee,ChairmanDushanBoroyevichJasonLaiGuo-Quan.LuAlexQ.HuangSeptember12,2003Blacksburg,VirginiaKeywords:distributedpowersystem,DC/DCconverter,integratedmagnetic,smallsignalmodel,resonantconverterCopyright2003,BoYangTopologyInvestigationforFrontEndDC/DCPowerConversionforDistributedPowerSystembyBoYangFredC.Lee,ChairmanElectricalengineering(Abstract)WiththefastadvanceinVLSItechnology,smaller,morepowerfuldigitalsystemisavailable.Itrequirespowersupplywithhigherpowerdensity,lowerprofileandhigherefficiency.PWMtopologieshavebeenwidelyusedforthisapplication.Unfortunately,holduptimerequirementputhugepenaltiesontheperformanceofthesetopologies.Also,highswitchinglosslimitedthepowerdensityachievableforthesetopologies.Twotechniquestodealwithholduptimeissuearediscussedinthisdissertation:rangewindingsolutionandasymmetricwindingsolution,theefficiencyatnormaloperationpointcouldbeimprovedwiththesemethods.Toreducesecondaryrectifierconductionloss,QSWsynchronousrectifierisdeveloped,whichalsohelpstoachieveZVSforsymmetricalhalfbridgeconverter.Althoughwiththesemethods,theefficiencyoffrontendDC/DCconvertercouldbeimproved,theexcessiveswitchinglossprohibitedhigherswitchingfrequency.Toachievethetargets,topologieswithhighswitchingfrequencyandhighefficiencymustbedeveloped.Threeresonanttopologies:SRC,PRCandSPRC,arebeeninvestigatedforthisapplicationbecauseoftheirfameoflowswitchingloss.Unfortunately,todesignwithholduprequirement,noneofthemcouldprovidesignificantimprovementsoverPWMconverter.iiiAlthoughthenegativeoutcome,thedesiredcharacteristicforfrontendapplicationcouldbederived.Baseonthedesiredcharacteristic,athoroughsearchisperformedforthreeelementsresonanttanks.LLCresonanttopologyisfoundtopossesthedesiredcharacteristic.Fromcomparison,LLCresonantconvertercouldreducethetotallossby40%atsameswitchingfrequency.Withdoubledswitchingfrequency,efficiencyofLLCresonantconverterisstillfarbetterthanPWMconverters.TodesignthepowerstageofLLCresonantconverter,DCanalysisisperformedwithtwomethods:simulationandfundamentalcomponentsimplification.Magneticdesignisalsodiscussed.Theproposedintegratedmagneticstructurecouldachievesmallervolume,higherefficiencyandeasymanufacture.Tomakepracticaluseofthetopology,overloadprotectionisacriticalissue.Threemethodstolimitthestressunderoverloadsituationarediscussed.Withthesemethods,theconvertercouldnotonlysurvivetheoverloadcondition,butalsooperateforlongtimeunderoverloadcondition.Nextsmallsignalcharacteristicoftheconverterisinvestigatedinordertodesignthefeedbackcontrol.Forresonantconverter,statespaceaveragemethodisnolongervalid.TwomethodsareusedtoinvestigatethesmallsignalcharacteristicofLLCresonantconverter:simulationandextendeddescribingfunctionmethod.Comparewithtestresults,bothmethodscouldprovidesatisfactoryresults.Toachievebothbreadthanddepth,twomethodsarebothusedtorevealthemyth.Withthisinformation,compensatorforfeedbackcontrolcouldbedesigned.TestcircuitofLLCresonantconverterwasdevelopedforfrontendDC/DCapplication.WithLLCtopology,powerdensityof40W/in3couldbeachievedcomparewith15W/in3forPWMconverter.ivToMyWifeQiaoqiaoBoYangAcknowledgementvACKNOWLEDGMENTIwouldliketothankmyadvisor,Dr.FredC.Lee.Tilltoday,Iamstillamusedbyhisgreatintuition,broadknowledgeandaccuratejudgment.ThemostpreciousthingIlearnedfromhimistheattitudetowardresearch,whichcanbeappliedtoeveryaspectsoflifetoo.Withouthisguidanceandchallenging,Iwillneverbeabletoachievethis.Iamgratefultomycommittee:Dr.DushanBoroyevich,Dr.JasonLai,Dr.AlexQ.HuangandDr.GuoQ.Lu,andDr.DanY.Chenfortheirvaluablesuggestionsandnumeroushelp.IthasbeenagreatpleasuretoworkintheCenterforPowerElectronicsSystems(CPES).IwouldliketoacknowledgetheCPESadministrativeandmanagementstaff,Ms.TeresaShaw,Ms.LindaGallagher,Ms.TrishRose,Ms.AnnCraig,Ms.MarianneHawthome,Ms.ElizabethTranter,Ms.LesliFarmer,Mr.RobertMartin,Mr.SteveZ.Chen,Mr.DanHuff,Mr.GaryKerr,andMr.JamieEvansfortheircountlesshelp.Iwouldliketothankmycolleagues,Dr.QiongLi,Dr.XunweiZhou,Dr.PitleongWong,Dr.RichardZhang,Dr.KunXing,Dr.JindongZhang,Dr.FengfengTao,Dr.WeiyunChen,Mr.DavidWen,Mr.Deng-MingPeng,Mr.ZhouChen,Mr.YuanxuanHu,Dr.YongLi,Mr.WenkangHuang,Dr.SihuaWen,Mr.RengangChen,MissJinghongGuo,Mr.WeiXu,Mr.ZhenxueXu,Dr.BoYangAcknowledgementviMing,Xu,Mr.Ho-PuWu,Mr.XiaowuSun,Mr.KaiweiYao,Mr.YuhuiChen,Mr.MaoYe,Mr.YuMeng,Mr.YuanchengRen,Prof.WeiChenandProf.XiaochuanJia.TheirfriendshipsandhelphavemademystayatCPESpleasantandenjoyable.IamespeciallyindebtedtomyteammatesintheDPSgroup,Dr.PeterBarbosa,Dr.QunZhao,Dr.FranciscoCanales,Dr.WeiDong,Mr.BingLu,Mr.YangQiu,Mr.LiyuYang,MissManjingXie,MissJuanjuanSun,MissTinaSang,andMr.DianboFu.Itwasapleasuretoworkwithsuchatalented,hard-workingandcreativegroup.Myheartfeltappreciationgoestowardmyfather,HuairuiYang,whohasalwaysencouragedmetopursuehighereducation.Ials