LLC电路基本原理分析及公式推导.pdf

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1、SimplifiedAnalysisandDesignofSeries-resonantLLCHalf-bridgeConvertersMLDGROUPINDUSTRIAL&POWERCONVERSIONDIVISIONOff-lineSMPSBUApplicationLabI&PCDiv.-Off-lineSMPSAppl.LabPresentationOutline•LLCseries-resonantHalf-bridge:operationandsignificantwaveforms•Simplifiedmodel(FHAa

2、pproach)•300WdesignexampleI&PCDiv.-Off-lineSMPSAppl.LabSeries-resonantLLCHalf-BridgeTopologyandfeaturesQ1Center-tappedoutputwithfull-CrLswaverectification
Multi-resonantLLCtankcircuit(lowvoltageandhighcurrent)Vin
VariablefrequencycontrolDriver
Fixed50%dutycycleforQ1&Q2H

3、alf-bridgeQ2LpVout
Dead-timebetweenLGandHGtoallowMOSFET’sZVS@turn-onLLCtankcircuit
fsw»fr,sinusoidalwaveforms:lowturn-offlosses,lowEMI
Equalvoltage¤tstressforPreferablyintegratedintoasingleVoutsecondaryrectifiers;ZCS,thennomagneticstructurerecoverylosses
Nooutputc

4、hoke;costsaving3reactiveelements,2resonantfrequenciesSingle-endedoutputwith
Integratedmagnetics:bothL’scan1bridgerectifiicationfr1(highvoltageandlowcurrent)berealizedwiththetransformer.2p××LsCr×f>f
Highefficiency:>96%achievabler1r21fr22p××(Ls+Lp)Cr×I&PCDiv.-Off-lineSMPS

5、Appl.LabLLCResonantHalf-bridgeWaveformsatresonance(f=f)swr1Dead-timeGate-drivesignalsHBmid-pointVoltageResonantcapvoltageTankcircuitcurrentissinusoidalMagnetizingcurrentistriangularTransformercurrentsDiodevoltagesOutputcurrentCCMoperationDiodecurrentsI&PCDiv.-Off-lineSM

6、PSAppl.LabLLCResonantHalf-bridgeSwitchingdetailsatresonance(f=f)swr1Dead-timeGate-drivesignalsZVS!HBmid-pointVoltageResonantcapvoltageTankcircuitcurrent>0TransformercurrentsMagnetizingcurrentV(D1)<0DiodevoltagesI(D1)=0ZCS!DiodecurrentsI&PCDiv.-Off-lineSMPSAppl.LabLLCRes

7、onantHalf-bridgeOperatingSequenceatresonance(Phase1/6)1/6Q1OFFQ1ONQ1OFFQ1Q2ONQ2OFFQ2ONCoss1LsCrVinn:1:1D1CoutCoss2VoutLpQ2D2
Q1isOFF,Q2isON
D1isOFF,D2isON;V(D1)=-2·Vout
Lpisdynamicallyshorted:V(Lp)=-n·Vout.
CrresonateswithLs,fr1appears
OutputenergycomesfromCrandLs
Phase

8、endswhenQ2isswitchedoffI&PCDiv.-Off-lineSMPSAppl.LabLLCResonantHalf-bridgeOperatingSequenceatresonance(Phase2/