电池充电电路设计及关键考虑点

1BatteryChargerDesign:Keyconsiderationsandsystemdesignlimitations2Agenda•SingleCellChargerSystems•InputConsiderationsandLimitations•TopologyOptions–Pros&ConsofPowerPathArchitecture•ThermalIssues•MarketTrendsNeedsvs.Limitations•InputCurrentOptimizer(ICO•SummaryandQuestionsSingleCellSystemsOverview3•SingleCell–MostCommonSolutionforSmartphones(1s)andTablets(1sXp)today–Allowsforsimple,lowvoltagedesignonthesystem(MaxBatteryVoltage4.35Vonsomelithiumbasedchemistries)–Simpledesigntochargefroma5Vsupplyasthechargerwillalwaysoperateinstepdownmode–Multiplecellsinparallelallowforlongerruntimesduetoextracapacity•Thiswillrequireahigherchargecurrentstomaintainanacceptablechargetime.Chargecurrentwillbeafunctionofthecurrentcapabilityoftheadapter.1sconfiguration1sXpconfigurationInputConsiderations•Howmanyinputconnectorswillthedevicehave?–SingleInput(i.e.Micro-USB,ProprietaryConnector)–MultipleInputs(i.e.Micro-USBandDockConnector)•Howmanyinputsourceswilltheproductsupport?–USBchargingonly(Maxcurrent:500mAforUSB2.0,900mAforUSB3.0)–USBchargingand/oradapterintosingleport•ForMicro-USBport,maximumcurrentsupportedbyadapteris1.8A•USBspecifiesmaximumcurrentof1.5A•Withalimitonthecurrent,changingtheinputvoltageallowsyoutoincreaseyouroutputcurrent•USBPowerDelivery(USBPD)willallowformorepoweravailableforchargesolutions.4Outputcurrentchangebasedoninputvoltage(assume90%efficiencyand3.6VBattery)AdapterPowerLimits•AdapterPowerLimitsToday–MostSmartphones:5W–8W–MostPopularTablets:10W–15W56CurrentCapabilitiesofAdapters•Powersourceshavetheirlimits–Therearesituationswheretheinputpowersourcedoesnothaveenoughpowertosupplywhattheportabledevicedemands–BecomingincreasinglyimportantwiththestandardizationofinputconnectorssuchastheMicro-USB–InputcurrentlimitsandInputVoltageDynamicPowerManagement(VINDPM)providethefunctionsneededtosolvethisproblem7VoltageInputDynamicPowerManagement(VINDPM)•Utilizingfullcapacityofadapter–VINDynamicPowerManagement(VINDPM)–Loopcontinuouslymonitoringtheinputvoltagetothecharger–WithoutVINDPMthedevicecanenterahiccupmodebetweenpowerupand“brown-out”condition–Wheninputvoltagedrops,devicewilllimittheinputcurrentDevicehitsVINDPMthresholdandinputcurrentisreducedVINIIN500mA/div1V/divUVLO8VoltageInputDynamicPowerManagement(VINDPM)•Utilizingfullcapacityofadapter–VINDynamicPowerManagement(VINDPM)–Loopcontinuouslymonitoringtheinputvoltagetothecharger–WithoutVINDPMthedevicecanenterahiccupmodebetweenpowerupand“brown-out”condition–Wheninputvoltagedrops,devicewilllimittheinputcurrentIVINVINVBATSTATProgrammedChargecurrenthigherthanadaptercapabilityDevicehitsVINDPMthresholdandinputcurrentisreducedPower-pathvs.NonPower-pathTopologies•NonPower-PathTopology•Thesystemvoltageisalwaysequaltothebatteryvoltage•Nosystemstartupfordeeplydischargedbatteries•ICHARGEisalwayssplitbetweenIBATandISYS•ICHARGEmustbeprogrammedtothemaximumchargecurrentforthebatterycell•IfISYSTerminationcurrent,thenterminationwillnotoccur•IBATisreducedforanysystemload•Reducedchargecurrentextendschargetime.Safetytimersmayexpireprematurely•Power-PathTopology•ICONVERTERissettomaximizethecurrentfromthesource.•Moreavailablecurrenttosystemandbatterychargingforfasterchargetime•IBATissetindependentofICONVERTER•Forlowsystemloads,ICONVERTERisreducedtomaintainproperchargecurrent•IBATisalwaysknownbycharger•Accurateterminationcurrent•Safetytimerextendedwhenchargecurrentislessthanprogrammedvalue9ChargerSystemLoadICHARGEISYSIBATConverterSystemLoadChargerICONVERTERISYSIBAT10DynamicPower-PathManagement(DPPM)•Functionthatmonitorstheinputcurrent,inputvoltageandoutputcurrentsofaPower-Pathdeviceandautomaticallygivesprioritytothesystemwhentheadaptercannotsupportthesystemload•SeefollowingexampleofDPPMfunctioninalinearcharger.Sameprinciplealliesforswitchingchargers.Assume5Wadapter(5V,1A)ISYS=0.5AIBAT=0.5AIIN≈1A11DynamicPower-PathManagement(DPPM)•Functionthatmonitorstheinputcurrent,inputvoltageandoutputcurrentsofaPower-Pathdeviceandautomaticallygivesprioritytothesystemwhentheadaptercannotsupportthesystemload•SeefollowingexampleofDPPMfunctioninalinearcharger.Sameprinciplealliesforswitchingchargers.Assume5Wadapter(5V,1A)IIN≈1AISYS=0.8AIBAT=0.2AVINDPMandDPPMworkingtogetherVIN5VAdapterratedfor750mAIINVSYSIBATISYS750mAChargingSupplementMode750mACharging1.2ALoadStepAdapterVoltageFallsduetoAdapterCurrentLimitInputCurrentReducedbyVINDPMfunctiontoPreventAdapterfromCrashing13DoesVINDPM=DPPM?•No.VINDPMpreventstheadapterfromhittinga“brown-out”condition.However,thechargerwillnotknowhowmuchcurrentisgoingtothesystemandhowmuchcurrentisgoingtothebattery.–AchargercanhaveVINDPMandnothavePower-path(DPPM)–Chargecurrentandsystemcurrentiscombinedandthechargerdoesnotknowhowmuchcurrentisbeingdeliveredonlytothebattery•DPPMallowsthechargertoknowexactlyhowmuchcurrentisgoingtothebattery.–Withthisinformation,thechargercanreducethechargecurrentandextendthechargingsafetytimerintheeventhesystemdemandshighercurrents•Whichoneisbetter?–Bothtopologiesallowtochargethebattery.NonDPPMchargerswillrequirethehosttomeasureexactlyhowmuchcurrentgoestothe