bridgelessPFC(1208).ppt

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1、BridgelessPFCViviansunBridgelessPFCThepurpose---Forhigherpowerrange,thebridgepowerlossishigh,especiallyatlowlinecondition.Forexample,thebridgepowerlossof1200WPSisabout24W.---ThebridgelessPFCtopologycanreducetotalpowerloss,improveefficiencyandthermalperformance.BridgelessPFCThecompari

2、sonofbridgeandbridgelessPFCThedesignprocessPowerlosscalculationDesigntoolsThecomparisonofbridgeandbridgelessPFCTopologyPowerLossandPart’sCountCurrentSensingIacSensingFloatingGroundThetopologyofbridgePFCTheTopologyofBridgelessPFCBridgelessPFCOperationComparisonofBridgeandBridgelessPFC

3、CurrentSensingCurrentSensingCurrentSensingIacSensing(bridge)IacSensing(bridgeless)TheFloatingGroundofBridgelessPFCWithacoupledchokeasboostinductor,nocapacitorcanlinkLandNtopowerGND,otherwisethechokewillbeshortened.SothepowerGNDisfloatingwiththeswitchesonandoffataswitchingfrequency.Th

4、eComparisonofEfficiencyDesignSpecificationsVin=90~264VACVo=380VDCPo=1200WFs=100kHzPF>0.98(Fullload&highline)Eff>92%BlockDiagramBoostInductorDesignPeakinputcurrentatlowlineIpk:DutycycleatlowlineD:BoostInductorDesignBoostinductanceL:DeltaIis20%peakcurrentSelectL=300uH(initialinductance

5、)BoostInductorDesignMagneticcore:ArnoldMS-185060-2orDongbuS184-086AMagneticmaterial:sendust(koolMu)Al=86mH/1000T,Bs=0.95TWechoose:N=60Accordingdesigntools,themaximummagneticforceis120Oerstedsandthefluxdensityis0.56T<(2/3)Bs.PowerStageDesignOutputcapacitorselection(holduptime20ms)Sele

6、ctCout=660uF(two330uF/450Vcapacitorinparallel)MainswitchselectionTwoSTW26NM60(600V/30A)inparallelBoostdiodeselectionLowreversecurrentandfastreverserecoverydiodeshallbeselected.SDT12S06orSTTH1506TTIispreferred.ControlCircuitDesignUsingUCC3818asthePFCcontrollerVoltageLoopDesignCurrentL

7、oopDesignCriticalPointofBridgelessPFCVoltageLoopDesign1Thepoleisplacedatthecrossoverfrequency,isabout10~20Hz,thezeroisplacedattheonetenthofthecrossoverfrequency.Thepowerstagegainisgivenby:VoltageLoopDesign2VoltageloopThevoltageamplifierconfigurationasright:Vref=7.5,sowechoose:R125=R1

8、26=R127=332k