L6562-35W

November2008Rev11/22AN2838Applicationnote35Wwide-rangehighpowerfactorflybackconverterdemonstrationboardusingtheL6562AIntroductionThisapplicationnotedescribesademonstrationboardbasedonthetransition-modePFCcontrollerL6562A,andpresentstheresultsofitsbenchdemonstration.Theboardisa35W,wide-rangemainsinput,powerfactorcorrectedSMPS(switchedmodepowersupply)suitableforalllowpowerapplicationsrequiringahighPF(powerfactor),suchaslightingapplicationsandpowersuppliesforLEDs.Thelow-costL6562AandthesimpleflybacktopologycombinetoprovideaverycompetitivePFCcontrollersolution.Figure1.EVL6562A-35WFLBdemonstrationboardusingtheL6562A:electricalschematic.....................6Figure3.EVL6562A-35WFLBcompliancewithEN61000-3-2Class-Climits@fullload..........9Figure4.EVL6562A-35WFLBcompliancewithJEIDA-MITIClass-Climits@fullload...........9Figure5.Powerfactorvs.VINandload................................................9Figure6.EVL6562A-35WFLBinputcurrentwaveform@100V-50Hz-35Wload.............10Figure7.EVL6562A-35WFLBinputcurrentwaveform@230V-50Hz-35Wload.............10Figure8.Efficiencyvs.VINandload.................................................10Figure9.StaticVOUTregulationvs.VINandIOUT..................................................10Figure10.EVL6562A-35WFLBoutputvoltageripple@90VAC-fullload.....................11Figure11.EVL6562A-35WFLBoutputvoltageripple@265VAC-fullload....................11Figure12.EVL6562A-35WFLBVDSandID@90VAC-fullload............................11Figure13.EVL6562A-35WFLBVDSandID@90VAC-fullload-detail.......................11Figure14.EVL6562A-35WFLBVDSandID@265VAC-fullload...........................12Figure15.EVL6562A-35WFLBVDSandID@265VAC-fullload-detail......................12Figure16.EVL6562A-35WFLBVDSandID@90VAC-40mA.............................12Figure17.EVL6562A-35WFLBVDSandID@90VAC-40mA-detail........................12Figure18.EVL6562A-35WFLBVDSandID@265VAC-40mA............................13Figure19.EVL6562A-35WFLBVDSandID@265VAC-40mA-detail.......................13Figure20.Thermalmapat90VAC-fullload............................................14Figure21.Thermalmapat265VAC-fullload...........................................14Figure22.115VACandfullload-phase...............................................15Figure23.115VACandfullload-neutral..............................................15Figure24.230VACandfullload-phase...............................................15Figure25.230VACandfullload-neutral..............................................15Figure26.Burstpulseandcharacteristics..............................................16Figure27.Electricalschematicwithsecondarycurrentfeedback............................17Figure28.Powertransformer.......................................................19MaincharacteristicsandcircuitdescriptionAN28384/221MaincharacteristicsandcircuitdescriptionThemaincharacteristicsoftheSMPSdemonstrationboardare:●Linevoltagerange:90to265VAC●Minimumlinefrequency(fL):47-63Hz●Regulatedoutputvoltage:48V●Ratedoutputpower:35W●Powerfactor(load=50%):0.9minimum●Minimumefficiency:85%atfullload●Maximum2fLoutputvoltageripple:1.5Vpk-pk/0.39VRMS(@VIN=90VAC,POUT=35W)●Maximumambienttemperature:50°C●ConductedEMI:Inacc.withEN55022Class-B●Surgerejection:surgetest2.5kV●Primarytosecondaryinsulation:4kV●PCBtypeandsize:double-sided,35µm,FR-4,120x82mmThemainfeatureofthisconverteristhattheinputcurrentisalmostinphasewiththemainsvoltage,thereforethepowerfactorisclosetounity.ThisisachievedbytheL6562Acontroller,whichshapestheinputcurrentasasinewaveinphasewiththemainsvoltage.Thepowersupplyutilizesatypicalflybackconvertertopology,usingatransformertoprovidetherequiredinsulationbetweentheprimaryandsecondaryside.Theconverterisconnectedafterthemainsrectifierandthecapacitorfilter,whichinthiscaseisquitesmalltoavoiddamagetotheshapeoftheinputcurrent.TheflybackswitchisrepresentedbythepowerMOSFETQ1,anddrivenbytheL6562A.Atstartup,theL6562AispoweredbytheVCCcapacitor(C6),whichischargedviaresistorsR1andR2.TheTR1auxiliarywinding(pins8-7)generatestheVCCvoltage,rectifiedbyD4andR4,thatpowerstheL6562Aduringnormaloperation.R3isalsoconnectedtotheauxiliarywindingtoprovidethetransformer