外文翻译单级单刀功率因数校正器 ACDC变换器.docx
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外文翻译单级单刀功率因数校正器 ACDC变换器.docx
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外文翻译单级单刀功率因数校正器ACDC变换器
电子与信息工程学院
本科毕业论文(设计)
外文文献翻译
译文题目:
single-stagesingle-switchpowerfactercorrectionAC/DCconverter
学生姓名:
专业:
指导教师:
2010年3月
原文:
Single-stagesingle-switchpowerfactorcorrectionAC/DCconverter
Abstract
Asingle-stagesingle-switchpowerfactorcorrectionAC/DCconverterisproposedinwhichthepowerfactorcorrection(PFC)inductorisconnedtedtoatapontheprimarywindingoftheDC/DCflybackconverterstage;thereisdirectenergytransferofapartoftheinputenergytotheoutputandtheDC-busvoltagefeedback.TheadditionaldischargepathinthePFCinductorandDC-busvoltagefeedbackeffectivelysuppressestheDC-busvoltageandincreasestheoverallefficiency.Experimentalresultsfora60Wconverterataconstantswitchingfrequencyof70kHzareobtainedtoshowtheperformanceoftheproposedconverter.ItisshownthatthevoltageacrosstheDC-buscapacitorcanbeheldbelow405Veventhoughtheconverteroperatesinawiderangeofinputvoltages(90V-265VAC)andthemeasuredinputcurrentharmonicssatisfytheIEC。
1Introduction
ManyPFCAC/DCconvertershavebeenpresentedinrecentyears.PFCtechniquescanbedividedintotwocategories:
asingle-stageapproachandatwo-stageapproach.Thetwo-stageapproachisthemostcommonlyusedapproach.Conventionaltwo-stagePFCconvertersinvolvetheuseofcascadingtwopower-processingstages,responsibleforpowerfactorcorrectionandoutputvoltageregualtion.APFCconverterisadoptedatthefront-endtoforcethelinecurrenttrackingthelinevoltageandanotherconventionalDC/DCconverteriscascadedafterthePFCstagetoobtainthedesiredtightlyregulatedoutputvoltage.Thisapproachcanobtainverygoodperformance,suchashighpowerfactor,andlowvoltagestress.However,duetotheuseoftwopower-processingstages,conversionefficiencyisreducedandanadditionalPFCstageaddscomponentsandcomplexity.Consequentlytheoverallcostincreases.Thetwo-stageapproachhasdisadvantagesoflowpowerdensity,controlcomplexity,andhighcost.Toreducetheoverallsizeandcost,anumberofsiglestagePFCconvertershavebeendevelopedintheliteraturewitchessothatthePFCswitchanditscontrollercanbeeliminated.Thesingle-stageapproachisspeciallyattractiveinlow-costandlow-powerapplicationsduetoitssimplepowerstageandcontrolcircuit.However,itstillhasseveraldrawbackssuchashighcurrentstressinpowerswitchandhighDC-busvoltagestress.ItsmajordrawbackisahighvoltagestressontheDC-buscapacitor.Manysingle-stagePFCAC/DCconverterssufferfromhighDC-busvoltagestressatlightloadandhighline,whichmakestheseconvertersimpractical.AhighDC-busvoltagemeanshighcomponentrating,highcostandlowvoltagestress.Experimentalresultsfora60Wconverterataconstantswitchingfrequencyof70kHzareobtainedtoshowtheperformanceoftheproposedconverter.ItishownthatthevoltageacrosstheDC-buscapacitorcanbeheldbelow404Veventhoughtheconverteroperatesinawiderangeofinputvoltages(90V-265VAC)andthemeasuredinputcurrentharmonicssatisfytheIEC61000-3-2ClassDrequirements.
2Analysisofproposedconverter
Figure1showstheequivalentcircuitsoftheproposedconverter.ThesecondarywindingNbisaddedinthePFCboostinductor.ThefirsttransformerT1inDC/DCpartcanbeoperatedeitherinCCMorDCMdependingontheloadconditionsasintheconventionalflybackconverter.Forsimplification,DC/DCpartisassumedtooperateinCCMforentirelineperiod.ThesecondtransformerT2isoperatedinDCM.AccordingtotheoperationofT2,WhentheDC-busvoltagefeedbackvalueV1(=np2Vab,np2=N2/Np)ishigherthantherectifiedlineinputvoltagevi,theconverteroperationentersregionA.InregionAonlyT1isoperatingandDbisreverse-biasedduringtheon-timeperiodS.WhenViishigherthanV1andlowerthanV2theoperationconverterentersregionB.InthisregionT1andT2worklikeflybacktransformers;V2isdeterminedbyVd+(n1-na)Vowheren1=N1/Nsandna=Na/Nb.WhenviishigherthanV2theconverteroperationentersregionC.InthisregionT1workslikeaflybacktransformerandT2workslikeaboostinductor.SincethevoltageviisVmsinotinthefirstquarteroflineperiod,theboundarytimestxandtyforthreemodesaregivenby
Fig.1Equivalentcircuit
2.1RegionAoperation
InregionAtheinputvoltageviislowerthantheDC-busvoltagefeedbackvalueVl_=(N2/Np)Vd.OnlytheDC/DCpartoperates.ItdeliverspowerfromtheDC-buscapacitorCdtotheloadRLthroughT1.AttotheswitchSisturnedon.SincetheDC-busvoltageVdisappliedacrossthemagnetisinginductanceLm1,themagnetisingcurrentiLm1increaseslinearlyfromitslowpeakvalueImA,Lasfollows:
Att1theswitchSisturnedoffandtheoutputdiodeD1ison.Since-npVoisappliedacrossthemagnetisinginductanceLm1,thecurrentdecreaseslinearlyfromitshighpeakvalueImA,Hasfollows:
ThediodecurrentiD1isgivenby
From(3)and(4)thevoltagegainisdeterminedasfollows:
SincetheDC/DCpartoperatesinCCM,thedutycycleDdoesnotchangewiththeloadvariation.From(6)theturnrationnpcanbedeterminedby
ThedutycycleDcanbeobtainedas
ThedutycycleDisalsoeffectiveinregionsBandC.ThepowerP1deliveredbythetransformerT1isdeterminedas
SincethepowerP1deliveredbythetransformerT1shouldbeequaltotheoutputpowerPo(=Vo2/RL),thefollowingrelationisobtained:
ConsequentlytheDC-buscapacitorprovidesthewholepowertotheload.From(3),(6)and(10),thehighandlowpeakvaluesofiLm1aredeterminedby
2.2RegionBoperation
WhenthevoltageviishigherthanV1andlowerthanV2,theconverteroperatesinregionB.PFCcelloperatesasDCMflybackconverter.Att0theswitchSisturnedon.SincetheDC-busvoltageVdisappliedacrossthemagnetisinginductanceLm1,themagnetisingcurrentiLm1increaseslinearlyfromitslowpeakvalueImB,Lasfollows:
ThemagnetisingcurrentiLm2increaseslinearlyfromzeroasfollows:
Since
theDC-buscapacitorcurrentiCd,thecurrenti2,andtheswitchcurrentisaregivenby
From(15)itcanbeseenthatthemagnetisingcurrentiLm1issuppliedbythemagnetisingcurrentiLm2andthedischargingcurrentiCdoftheDC-buscapacitorCd.From(17)theswitchcurrentisisalsocomposedofthetwocomponents.Thecondutionlosscanbereducedbyselectingsmallernp1.Att1theswitchSisturnedoffandtheoutputdiodesD1andD2areon.SincenpVoisappliedacrossthemagnetisinginductanceLm1,thecurrentiLm1decreaseslinearlyfromitshighpeakvalueImB,Hasfollows:
SincethediodeD2ison,_naVoisappliedacrossthemagnetisinginductanceLm2andthecurrentiLm2decreaseslinearlyfromitspeakvalueIm,pasfollows:
ThepeakvalueIm,pisgivenby
From(20)
Att2thecurrentiLm2arrivesatzeroandthediodeD2isturnedoff.ThepowerP1deliveredbythetransformerT1isgivenby
ThepowerP2deliveredbythetransformerT2isdeterminedby
SincethesumofthepowerP1deliveredbythetransformerT1andthepowerP2deliveredbythetransformerT2shouldbeequaltotheoutputpowerPo,thefollowingrelationis
obtained:
From(6),(13)and(24),thehighandlowpeakvaluesofiLm1aredeterminedby
2.3RegionCoperation
WhenthevoltageviishigherthanV2theconverteroperatesinregionC.ThePFCcelloperatesasaDCMboostconverterandthediodeD2isoffinthisregion.Att0theswitchSisturnedon,iLm1increaseslinearlyas
follows:
iLm2increaseslinearlyasinregionB.Equations(9)–(11)arealsoeffectiveinthisregion.ThemagnetisingcurrentiLm1issuppliedbythemagnetisingcurrentiLm2andthedischarging
currentiCdoftheDC-buscapacitorCd.WhenthecurrentiLm2ishighenoughthatnp2iLm2exceedsiLm1,theDC-buscapacitorcanbeinchargingmodeduringtheontimeintervalofS.Thischargingmodemayoccurnearthelinepeakvoltageasfollows:
Att1theswitchSisturnedoffandtheoutputdiodesD1.Since_npVoisappliedacrossthemagnetisinginductanceLm1,thecurrentiLm1decreaseslinearlyfromitshighpeakvalueImC,Hasfollows:
SincethediodeDbison,thevoltageacrossthemagnetisinginductanceLm2is_Vd_n1Vo+viandthecurrentiLm2decreaseslinearlyfromitspeakvalueIm,pasfollows:
ThepeakvalueIm,pisgivenby
From(31)
Since
thecurrenti1,theDC-buscapacitorcurrentiCd,andthediodecurrentiD1aredetermineasfollows:
ThecurrentiD1iscomposedoftwocomponentswhicharefromLm1andLm2.Therefore,thereisdirectpowertransferfromthelineinputtotheloadduringtheswitchoff-time.Asaresulttheoverallefficiencycanbeimproved.Att2,thecurrentiLm2arrivesatzeroandthediodeDbisturnedoff.ThecurrentiD1isnpiLm1.SincetheoutputpowershouldbeequaltothesumofthepowerfromLm1andthepowerfromLm2,thefollowingrelationis
obtained:
From(6),(13)and(24),thehighandlowpeakvaluesofiLm1aredeterminedby
3Concludingremarks
Asingle-stagesingle-switchpowerfactorcorrectionAC/DCconverterhasbeenproposed.Experimentalresultsfora60Wconverterataconstantswitchingfrequencyof70kHzhavebeengiventoshowtheperformanceoftheproposedconverter.ExperimentalresultshaveshownthatthevoltageacrosstheDC-buscapacitorcanbeheldbelow404Veventhoughtheconverteroperatesinawiderangeofinputvoltages(90B265V).Asaresult,commerciallyavailableelectrolyticcapacitors,canbeused.TheCCMDC/DCstage,directenergytransferandthereducedconductionlossinthepowerswitchcanincreasetheefficiencyanditsmaximumvalueis91.1%.TheconvertermeetsEN/IE
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