EMI和安全方面技术指导

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1、®TOPSwitchPowerSupplyDesignTechniquesforEMIandSafetyApplicationNoteAN-15Offlineswitchingpowersupplieshavehighvoltageandhigh120FCCAQPcurrentswitchingwaveformsthatgenerateElectromagneticFCCBQP100Interference(EMI)intheformofbothconductedandradiatedemissions.Consequently,alloff-linepowersuppliesmustb

2、eV)PI-1622-111695µ80designedtoattenuateorsuppressEMIemissionsbelowcommonlyacceptablelimits.60Thisapplicationnotepresentsdesigntechniquesthatreduce40conductedEMIemissionsinTOPSwitchpowersuppliesbelowAmplitude(dBnormallyspecifiedlimits.Properlydesignedtransformers,PC20boards,andEMIfiltersnotonlyred

3、uceconductedEMIemissionsbutalsosuppressradiatedEMIemissionsandimproveEMI00.010.1110100susceptibility.ThesetechniquescanalsobeusedinapplicationsFrequency(MHz)withDCinputvoltagessuchasTelecomandTelevisionCableFigure1.FCCClassAandBLimits(QuasiPeak).Communication(orCablecom).RefertoAN-14andAN-20forad

4、ditionalinformation.Thefollowingtopicswillbepresented:120EN55022AQP•EMISpecificationsforNorthAmerica,EuropeanEN55022AAVG100Community,andGermanyEN55022BQPV)EN55022BAVG•MeasuringConductedEmissionswithaLISNµPI-1623-11169580•Peak,Quasi-Peak,andAverageDetectionMethods•SafetyPrinciples60•EMIFilterCompo

5、nents•FlybackPowerSupplyEMISignatureWaveforms40•FilterAnalysisAmplitude(dB•PowerCordResonances20•TransformerConstructionTechniques0•SuppressionTechniques0.010.1110100•GeneralPurposeTOPSwitchEMIFiltersFrequency(MHz)•EMIFilterPCLayoutIssuesFigure2.EN55022ClassAandBLimits(AverageandQuasiPeak).•Pract

6、icalConsiderations120120Vfg243QPVfg243QPVfg1046QPVfg46AVG100100(VDE0871BQP)V)V)µPI-1624-111695µPI-1834-042296808060604040Amplitude(dBAmplitude(dB2020000.010.11101000.010.1110100Frequency(MHz)Frequency(MHz)Figure4.Vfg243(QuasiPeak)andVfg46(Average)ClassBFigure3.Vfg1046andVfg243ClassBLimits(QuasiPe

7、ak).Limits.April2005AN-15SafetyisavitalissuewhichdeterminesEMIfiltercomponentselection,thetransformerreinforcedinsulationsystem,andPCboardprimarytosecondaryspacing.Infact,safetyisanintegralINPUTOUTPUTpartofthepowersupp