Darkside-of-flyback-converter

1•ChrisBasso–APEC2011TheDarkSideofFlybackConvertersPresentedbyChristopheBassoSeniorScientistIEEESeniorMember2•ChrisBasso–APEC2011CourseAgenda
TheFlybackConverter
TheParasiticElements
HowTheseParasiticsAffectyourDesign?
Current-ModeistheMostPopularScheme
FixedorVariableFrequency?
MorePowerthanNeeded
TheFrequencyResponse
CompensatingWiththeTL4313•ChrisBasso–APEC2011WhatistheSubject?
TherehasbeennumerousseminarsonFlybackconverters
Seminarsareusuallyhighlytheoretical–linktothemarket?
Industrialrequirementsusuallynotcovered
This3-hourseminarwillshedlightsonlesscoveredtopics:Whytheconverterdeliversmorepowerthanexpected?Solutions?Bookstalkaboutcompensationwithopamps,IhaveaTL431!TheoriginoftheRight-HalfPlaneZero,howdoIdealwithit?Quasi-resonantconverterspresenceincreases,howdotheywork?Ina3-hourcourse,wearejustscratchingthesurface…!4•ChrisBasso–APEC2011TheFlyback,aPopularStructure
TheflybackconverteriswidelyusedinconsumerproductsEaseofdesign,low-cost,well-knownstructurePoorEMIsignature,bulkytransformer,practicalupto150Wflyback≈40–180WNotebookflyback≈3–5WChargerflyback≈10–35WDVDplayerSet-topboxNetbook5•ChrisBasso–APEC2011124drv75drv891211drvVoutVoutVoutgndgndbuck-boostgroundreferencedbuck-boostinputreferencedflybackisolatedgroundreferencedabcVinDCSW1L1NVinDCSW1LVinSW1DCAnIsolatedBuck-Boost
Theflybackconverterisderivedfromthebuck-boostcell
Theadditionofatransformerbrings:Vin-k.Vin+•UpordownscaleVin•Isolation•Polaritychange•Morethan1output6•ChrisBasso–APEC2011..inonpVSL=
ThecurrentincreasesintheinductorinrelationshiptoVinandLp
TheoutputcapacitorsuppliestheloadonitsowninpeakvalleyonpVIItL=+CCMinpeakonpVItL=DCMPIVinoutVNV=+ReversevoltageonthediodeSimplified,noleakageTheTurn-onEvent
Thepowerswitchturnson:currentrampsupinLp,DisblockedinVSWpIsec0I=inNV-outVpLspNNN=0VontontpeakIpeakIvalleyICIinV()pIt7•ChrisBasso–APEC2011..,outDSoffininrVVVVVN=+=+Reflectedvoltage()11outonswinoffswVNtNDTNDVtDTD===--VLp(t)ton=DTswtoff=(1-D)TswVinVout/NApplyvolt-secondbalancedctransferfunctioninCCMApplyingVolt-SecondBalance,CCM
Thepowerswitchturnsoff:Dconducts,VoutfliesbackinVpLoutVoutVNpINCI8•ChrisBasso–APEC2011..VLp(t)ton=DTswtoff=(1-D)TswVout/NVinDT2outloadinpswVRDVLF=NnolongerplaysaroleRload,LpandFswdo,DSoffinVV=ApplyingVolt-SecondBalance,DCMApplyvolt-secondbalance
InDCM,whenLpisfullydepletedDopens:VoutreflectionislostdctransferfunctioninDCMinVpL0Vsec0I=CI9•ChrisBasso–APEC201124X1PSW1RON=10mROFF=1Meg3Cout470uIC=10V240PULSE05010n10n3u10uRload25Vin100V2Vout61X2XFMRRATIO=-0.1LsVdsIIn..Lp2.2mD1DSFlyback,TypicalWaveforms
Belowisasimpleflybackconverter,withoutparasitics
Itwillrunopenloopforsimplicity,Vout≈8VNoparasitics10•ChrisBasso–APEC2011Flyback,TypicalWaveforms,CCM0400m800m1.201.60iininamperesplot11750m850m950m1.051.15i(lp)inamperesplot2210.070.0130190250vdsinvoltsplot338.818.838.858.878.89voutinvoltsplot443.002m3.006m3.010m3.014m3.018mtimeinseconds04.008.0012.016.0id(d1)inamperesplot55Iin(t)ILp(t)VDS(t)Vout(t)LIΔIpeakVinoutVNoutinVNV+Outputcap.refuelingOutputcapacitorsuppliestheloadDiodeblocksId(t)Ipeak/N0400m800m1.201.60iininamperesplot11750m850m950m1.051.15i(lp)inamperesplot2210.070.0130190250vdsinvoltsplot338.818.838.858.878.89voutinvoltsplot443.002m3.006m3.010m3.014m3.018mtimeinseconds04.008.0012.016.0id(d1)inamperesplot55Iin(t)ILp(t)VDS(t)Vout(t)LIΔIpeakVinoutVNoutinVNV+Outputcap.refuelingOutputcapacitorsuppliestheloadDiodeblocksId(t)Ipeak/NCCMflyback–noparasiticsInputcurrentIvalleyEvalleyEpeakInductorcurrentDrainvoltageOutputvoltageDiodecurrent11•ChrisBasso–APEC20110100m200m300m400miininamperesPlot110100m200m300m400mi(lp)inamperesPlot220100200300400vdsinvoltsPlot3312.63212.63612.64012.64412.648voutinvoltsPlot443.002m3.006m3.010m3.014m3.018mtimeinseconds-1.0001.002.003.00id(d1)inamperesPlot55Iin(t)ILp(t)VDS(t)Vout(t)LIΔIpeakVinoutVNoutinVNV+DCM(corereset)Outputcap.refuelingOutputcapacitorsuppliestheloadDiodeblocksId(t)Ipeak/N0100m200m300m400miininamperesPlot110100m200m300m400mi(lp)inamperesPlot220100200300400vdsinvoltsPlot3312.63212.63612.64012.64412.648voutinvoltsPlot443.002m3.006m3.010m3.014m3.018mtimeinseconds-1.0001.002.003.00id(d1)inamperesPlot55Iin(t)ILp(t)VDS(t)Vout(t)LIΔIpeakVinoutVNoutinVNV+DCM(corereset)Outputcap.refuelingOutputcapacitorsuppliestheloadDiodeblocksId(t)Ipeak/NEvalley=0EpeakFlyback,TypicalWaveforms,DCMInputcurrentInductorcurrentDrainvoltageOutputvoltageDiodecurrentDCMflyback–noparasitics12•ChrisBasso–APEC20112,12pLvalleypvalleyELI=2,12pLpeakppeakELI=InitiallystoredenergyStoredenergyatton()2222,111222pLtransppeakpvalleyppeakvalleyELILILII=-=-TransmittedenergyatTsw()2212outpeakvalleypswPIILFη=-CCMDCM,Ivalley=0EnergyTransferinCCMandDCMEta,theefficiency
Theprimaryinductance,Lp,storesandreleasesenergy
Power(W)isenergy(J)averagedovertime(s):212outpeakpswPILFη=13•ChrisBasso–APEC2011CourseAgenda
TheFlybackConverter
TheParasiticElements
HowTheseParasiticsAffectyourDesign?
Current-ModeistheMostPopularScheme
FixedorVariableFrequency?
MorePowerthanNeeded
TheFrequencyResponse
CompensatingWiththeTL43114•ChrisBasso–APEC201