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1ExplanationofElectromagneticInterferenceExplanationofElectromagneticInterference(EMI)inSwitchingPowerSupply(EMI)inSwitchingPowerSupplyPowereLabHKUPreparedbyPreparedbyFrankiFrankiPoonPoon&BryanPong&BryanPongEMIinSwitchingPowerSupplyEMIinSwitchingPowerSupply©copyright2002AbriefintroductiontotheAbriefintroductiontothePowereLabOurMission:Toadvanceswitchingpowerconvertertechnologies„Todevelopexcellenceinpowerelectronicstechnologies„ToapplythetechnologiestoproductsandfostercooperationwithindustriesContactPerson:Dr.BryanM.H.PongPowerElectronicsLab.,DepartmentofElectrical&ElectronicEngineering,HongKongUniversity,PokfulamRoad,HongKongTel:(852)28597099Fax:[phone]or25598738Email:[e-mail]:„Easy–EMIBasics.Whatandhowpeopletestyourproduct.„Notsoeasy–GeneralattitudeofanEMIengineer.„Difficult–HowEMIisproduced.„Moredifficult–HowEMIcomesandgoes.PowereLabHKUPreparedbyPreparedbyFrankiFrankiPoonPoon&BryanPong&BryanPongEMIinSwitchingPowerSupplyEMIinSwitchingPowerSupply„EveryEMIissuehasthefollowing3basicblocksNoiseSourceCouplingPathReceiverPowereLabHKUPreparedbyPreparedbyFrankiFrankiPoonPoon&BryanPong&BryanPongEMIinSwitchingPowerSupplyEMIinSwitchingPowerSupply„SwitchingvoltageandcurrentwaveformsinaswitchingpowersupplyPowereLabHKUPreparedbyPreparedbyFrankiFrankiPoonPoon&BryanPong&BryanPongEMIinSwitchingPowerSupplyEMIinSwitchingPowerSupply„RectangularTime0s4us8us12us16us20usV(R1:2)0V50V100VFrequency10KHz100KHz1.0MHz10MHz100MHz500MHzV(R1:2)100uV1.0V1.0uV100VTime0s4us8us12us16us20usV(R2:2)0V50V100VFrequency10KHz100KHz1.0MHz10MHz100MHz500MHzV(R2:2)100uV1.0V1.0uV100VTime0s4us8us12us16us20usV(R3:2)-100V0V100VFrequency10KHz100KHz1.0MHz10MHz100MHz500MHzV(R3:2)100uV1.0V1.0uV100V„Forward„Bridge10kHz500MHz10001000100-100PowereLabHKUEMIinSwitchingPowerSupplyEMIinSwitchingPowerSupply(R5)0A5A10AFrequency10KHz100KHz1.0MHz10MHz100MHz500MHz-I(R5)100uA1.0A1.0uATime0s4us8us12us16us20us-I(R6)0A5A10AFrequency10KHz100KHz1.0MHz10MHz100MHz500MHz-I(R6)100uA1.0A1.0uA„ContinuousFlyback„DiscontinuousFlyback10kHz500MHz100100PowereLabHKUPreparedbyPreparedbyFrankiFrankiPoonPoon&BryanPong&BryanPongEMIinSwitchingPowerSupplyEMIinSwitchingPowerSupply(R8)0V50V100VFrequency10KHz100KHz1.0MHz10MHz100MHz500MHzV2(R8)100uV1.0V1.0uV100VTime0s4us8us12us16us20usV2(R9)0V50V100VFrequency10KHz100KHz1.0MHz10MHz100MHz500MHzV2(R9)100uV1.0V1.0uV100V10001000„Dutycycle=0.210kHz500MHz„Dutycycle=0.6PowereLabHKUPreparedbyPreparedbyFrankiFrankiPoonPoon&BryanPong&BryanPongEMIinSwitchingPowerSupplyEMIinSwitchingPowerSupply(Effectofwaveformslope(dv/dtdv/dt))„30nsriseandfalltimeTime0s4us8us12us16us20usV(R1:2)0V50V100VFrequency10KHz100KHz1.0MHz10MHz100MHz500MHzV(R1:2)100uV1.0V1.0uV100V10kHz500MHz1000Time0s4us8us12us16us20usV(R7:2)0V50V100VFrequency10KHz100KHz1.0MHz10MHz100MHz500MHzV(R7:2)100uV1.0V1.0uV100V1000„300nsriseandfalltimePowereLabHKUPreparedbyPreparedbyFrankiFrankiPoonPoon&BryanPong&BryanPongEMIinSwitchingPowerSupplyEMIinSwitchingPowerSupply„Voltageandcurrentw