电磁兼容资料第二部分5

EMIFilterDesignCriteriaEMIFilterDesignCriteriaforSMPSforSMPSG.G.SpiazziSpiazziDepartmentofInformationEngineeringDepartmentofInformationEngineering,UniversityofPadova,Italy,UniversityofPadova,Italy2EMIFilterDesignCriteriaEMIFilterDesignCriteriaforSMPSforSMPSOutlineOutline99IntroductionIntroduction99CommonmodeanddifferentialmodefilterCommonmodeanddifferentialmodefilterconfigurationsconfigurations99AnalysisofinstabilitiescausedbyinputfilterinAnalysisofinstabilitiescausedbyinputfilterinswitchingpowersuppliesswitchingpowersupplies99DMnoiseestimationofaPFCDMnoiseestimationofaPFC99CommonmodesourceimpedanceestimationofaCommonmodesourceimpedanceestimationofaPFCPFC99EffectofPFClayoutonoverallnoiseEffectofPFClayoutonoverallnoise99AnalysisofinteractionsbetweenEMIfilterandPFCAnalysisofinteractionsbetweenEMIfilterandPFCconverterconverter99ConclusionsConclusions3FiltersFilters9Toblockanyunintendedsignal(EMI)onconductors(bothsignalconductorsandpowerconductors)9TopreservetheshieldingeffectivenessofanenclosurebypreventingelectromagneticenergyfromenteringorleavingtheenclosureGoal:Antennas4InputFilterforPowerLineInputFilterforPowerLineConductedEmissionsConductedEmissions9Thefiltersmustbetransparenttothepowersupply(AClineorDC)highcomponentpolarization9Lineandloadimpedancesarenotwelldefined9Thefiltersarerequiredtooperateinaverybroadfrequencyrange(filtercomponentschangetheircharacteristicspossibleresonances)5ConductedModeSignalsConductedModeSignalsUUUIIIdd=−=−12122,i1Ud++U2U1i2E.U.TEarthUcUUUIIIcc=+=+12122,i1++U2U1i2E.U.TicEarthCommonmodeDifferentialmode6CMandDMFiltersCMandDMFilters9EachpowerlinefilteriscomposedbyaDifferentialMode(DM)sectionandaCommonMode(CM)section9DMsectionmustbetransparenttothepowerfrequency(DCorACline)¼lowerlimitonfiltercornerfrequencyandhighcomponentpolarization9CMsectiondoesnothavetheselimitations(nousefulsignaltopass).HoweverthemaximumCMcapacitorvaluesinACpowerlineapplicationsarelimitedbyleakagecurrenttoearth(safetyreasons)7ExampleofCMandDMFilterExampleofCMandDMFilterLCMC2C1C3C4DifferentialModeC2+C3//C4LdC1CommonModeC3+C4LCM8FilterConfigurationFilterConfigurationKeypoint:maximumimpedancemismatchatinputandoutputfilterportsCLZgZLUgZg=low,ZL=highCLZgZLUgZg=high,ZL=lowCLZgZLUgCZg=high,ZL=highCLZgZLUgLZg=low,ZL=low9CMInductorCMInductor9Highinductancevaluethroughtheuseofahighpermeabilitycore9lowend-to-endparasiticcapacitancesoastoincreaseselfresonancefrequency1234N1234N568971234N56897N1234NLowend-endcapacitysolenoidalchokewindingsLowend-endcapacity(usedinhighcurrentRFchokes)10InsertionLossInsertionLossFilterUgZSZLU2+-+f2210f2210UUlog20PPlog10IL⋅=⋅=P2=loadpowerwithoutfilterP2f=loadpowerwithfilter11InsertionLossInsertionLoss9Thefilterinsertionlossdependsonsourceandloadimpedances9CommercialEMIfiltersarecharacterizedbyinsertionlossmeasuredwith50Ωsourceandloadimpedances12InputFilterforPowerLineInputFilterforPowerLineConductedEmissionsofSMPSConductedEmissionsofSMPSGoals:9Desiredattenuationatswitchingfrequency9Overallstability9Minimumimpactonconverterperformance(i.e.audiosusceptibility,outputimpedance,loopgain)9Minimumlosses9Minimumsize13InteractionFilterInteractionFilter--ConverterConverterDifferentialModeInputFilterDC-DCConv.SourceLoaduiuo++ZoFZiC14StabilityProblemStabilityProblem+HFuiZOFZIC-ugFFICOFFigT1HZZ1Huu+=+=TFmustsatisfyNyquiststabilitycriterionICOFFZZT=15ConverterInputImpedanceConverterInputImpedanceTheconverterbehavesasaconstantpowerload(atfrequenciesbelowthecontrolloopcrossoverfrequency)TheinputimpedanceisnegativeConsequence:16ConverterInputImpedanceConverterInputImpedanceic2ic2icicicicicRPuiPiPiddiddu−=−=−==DC-DCConv.Loaduo+uic+-iic17ConverterInputImpedanceConverterInputImpedanceConsiderations:9Theconverterbehavesasaconstantpowerloadonlyinthefrequencyregioninsidethecontrolloopbandwidth9Inputfeedforwardtechniquescauseanegativeinputimpedanceindependentlyofthecontrolloopbandwidth18ImpactonConverterImpactonConverterPerformancePerformanceVoltageControl:dc-dcconvertersmall-signalcanonicalmodel-+++Ree(s)d^j(s)d^LeCuo^R1:µFmAeuoREF^+-Zsus^ZeiZi19CanonicalModelParametersCanonicalModelParametersFm=PulsewidthmodulatorgainAe=Voltageregulatortransferfunction()()()sfRsjse=2DL′L2DL′Lej(s)DRUoRDUo′RDDUo′e(s)DUo−′RLs1DUeqo−′RDLs1DDUeqoDD1′DD′µBuckBoostBuck-Boost20VoltageControlVoltageControlZerosourceimpedanceudmGFAT=Loopgain:T1FFOL+=Audiosusceptibility:T1ZZoOLo+=Outputimpedance:()()TZsesj1T1ZZeiOLeiOLei⋅−+=Inputimpedance:21VoltageControlVoltageControlZerosourceimpedance()()TZsesj1T1ZZeiOLeiOLei⋅−+=Inputimpedance:()()()sfRsjseZei−=−≈For|T|1:Negativeinputimpedance22VoltageControlVoltageControlNonZerosourceimpedance()eiOLs2s2ZZ1sfRZ1TTµ+µ−⋅=′Loopgain:eis2ZZ11FFµ+⋅=′Audiosusceptibility:()eis2ees2ooZZ1sLRZ1ZZµ++µ+⋅=′Outputimpedance:23VoltageControlVoltageControlNonZerosourceimpedance()eiOLs2s2eis2isFZZT11sfRZT1TZZZZTµ⋅++µ⋅+−=µ==If|TF|1thecombinationfilter+converterisstable24StabilityConditionStabilityCondition()1ZZ1sfRZeiOLs2s2µµ()1ZZT11sfRZT1TTeiOLs2s2Fµ⋅++µ⋅+−=()TZZ1sfRZ1TTeiOLs2s2≈µ+µ−⋅=′FZZ11F