DesignofaLead-AcidBatteryChargingandProtectingICinPhotovoltaicSystemZENGDe-you,LINGChao-dong,LIGuo-gang(YuanshunICDesignR&DCenter,HuaqiaoUniversity,Quanzhou362021,China)Source:MicroelectronicDevice&Technology,June20071.IntroductionSolarenergyasaninexhaustible,inexhaustiblesourceofenergymoreandmoreattention.Solarpowerhasbecomepopularinmanycountriesandregions,solarlightinghasalsobeenputintouseinmanycitiesinChina.Asakeypartofthesolarlighting,batterychargingandprotectionisparticularlyimportant.Sealedmaintenance-freelead-acidbatteryhasasealed,leak-free,pollution-free,maintenance-free,low-cost,reliablepowersupplyduringtheentirelifeofthebatteryvoltageisstableandnomaintenance,theneedforuninterruptedforthevarioustypesofhaswideapplicationinpowerelectronicequipment,andportableinstrumentation.Appropriatefloatvoltage,innormaluse(topreventover-discharge,overcharge,over-current),maintenance-freelead-acidbatteryfloatlifeofupto12~16yearsfloatvoltagedeviationof5%shortenthelifeof1/2.Thus,thechargehasamajorimpactonthistypeofbatterylife.Photovoltaic,batterydoesnotneedregularmaintenance,thecorrectchargeandreasonableprotection,caneffectivelyextendbatterylife.ChargingandprotectionICistheseparationoftheoccupiedareaandtheperipheralcircuitcomplexity.Currently,themarkethasnotyetreal,chargedwiththeprotectionfunctionisintegratedonasinglechip.Forthisproblem,designasetofbatterychargingandprotectionfunctionsinoneICisverynecessary.2.SystemdesignandconsiderationsThesystemmainlyincludestwoparts:thebatterychargermoduleandtheprotectionmodule.Ofgreatsignificanceforthebatteryasstandbypoweruseoftheoccasion,Itcanensurethattheexternalpowersupplytothebattery-powered,butalsointhebatteryovercharge,over-currentandanexternalpowersupplyisdisconnectedthebatteryistoputthestatetoprovideprotection,thechargeandprotectionrolledintoonetomakethecircuittosimplifyandreducevaluableproductwasteofresources.Figure1isaspecificapplicationofthisIcinthephotovoltaicpowergenerationsystem,butalsothesourceofthisdesign.accumulatorDCloadcontrollerDischargecontrollerChargecontrolleraccumulatorDCloadcontrollerDischargecontrollerChargecontrollersolarbatteryarrayFigure1PhotovoltaiccircuitsystemblockdiagramMaintenance-freelead-acidbatterylifeisusuallythecyclelifeandfloatlifefactorsaffectingthelifeofthebatterychargerate,dischargerate,andfloatvoltage.Somemanufacturerssaidthatiftheoverchargeprotectioncircuit,thechargingratecanbeachievedevenmorethan2C(Cistheratedcapacityofthebattery),batterymanufacturersrecommendchargingrateofC/20~C/3.Batteryvoltageandtemperature,thetemperatureisincreasedby1°C,singlecellbatteryvoltagedrops4mV,negativetemperaturecoefficientof-4mV/°Cmeansthatthebatteryfloatvoltage.Ordinarychargerforthebestworkingconditionat25°C;chargelessthantheambienttemperatureof0°C;at45°Cmayshortenthebatterylifeduetosevereovercharge.Tomakethebatterytoextendtheworkinglife,haveacertainunderstandingandanalysisoftheworkingstatusofthebattery,inordertoachievethepurposeofprotectionofthebattery.Battery,therearefourstates:normalstate,over-currentstateoverthestateofcharge,overdischargestate.However,duetotheimpactofthedifferentdischargecurrentover-capacityandlifetimeofthebatteryisnotthesame,sothebatteryoverdischargecurrentdetectionshouldbetreatedseparately.Whenthebatteryischargingthestatealongtime,wouldseverelyreducethecapacityofthebatteryandshortenbatterylife.Whenthebatteryisthetimeofdischargestatusexceedstheallottedtime,thebattery,thebatteryvoltageistoolowmaynotbeabletorecharge,makingthebatterylifeislower.Basedontheabove,thechargeonthelifeofmaintenance-freelead-acidbatterieshaveasignificantimpact,whilethebatteryisalwaysingoodworkingcondition,batteryprotectioncircuitmustbeabletodetectthenormalworkingconditionofthebatteryandmaketheactionthebatterycannevernormalworkingstatebacktonormaloperation,inordertoachievetheprotectionofthebattery.3.Unitsmodulardesign3.1ThechargingmoduleChip,chargingmoduleblockdiagramshowninFigure2.Thecircuitryincludescurrentlimiting,currentsensingcomparator,referencevoltagesource,under-voltagedetectioncircuit,voltagesamplingcircuitandlogiccontrolcircuit.VoltagesamplingcomparatorUndervoltagedetectioncircuitR-powerVoltageamplifierPowerindicatorLimitingamplifierCurrentsamplingcomparatorLogicalmoduleChargingindicatorStatelevelcontrolStartamplifierdriverVoltagesamplingcomparatorUndervoltagedetectioncircuitR-powerVoltageamplifierPowerindicatorLimitingamplifierCurrentsamplingcomparatorLogicalmoduleChargingindicatorStatelevelcontrolStartamplifierdriverFigure2ChargingmoduleblockdiagramThemodulecontainsastand-alonelimitingamplifierandvoltagecontrolcircuit,itcancontroloff-chipdrive,20~30mA,providedbythedriveoutputcurrentcandirectlydriveanexternalseriesofadjustmenttube,soastoadjustthechargeroutputvoltageandcurrent.Voltageandcurrentdetectioncomparatordetectsthebatterychargestatus,andcontrolthestateoftheinputsignalofthelogiccircuit.Whenthebatteryvoltageorcurrentistoolow,thechargetostartthecomparatorcontrolthecharging.Appliancesintothetricklechargestatewhenthecut-offofthedrive,thecomparatorcanoutputabout20mAintothetricklechargecurrent.Thus,whenthebatteryshort-circuitorreverse,thechargercanonlychargeasmallcurrent,toavoiddamagetothebatterychargingcurrentistoolarge.Thismoduleconstitutesachargingcircuitchargingprocessisdividedintotwochargingstatus:high-currentconstant-currentchargestate,high-voltagechargestatusandlow-voltageconstantvoltagefloatingstate.Thechargingprocessfromtheconstantcurrentchargingstatus,theconstantchargingcurrentofthechargeroutputinthisstate.Andthechargercontinuouslymonitorsthevoltageacrossthebatterypack,thebatterypowerhasbeenrestoredto70%to90%ofthereleasedcapacitywhenthebatteryvoltagereachestheswitchingvoltagetochargeconversionvoltageVsamchargermovestothestateofcharge.Inthisstate,thechargeroutputvoltageisincreasedtooverchargepressureVocisduetothechargeroutputvoltageremainsconstant,sothechargingcurrentisacontinuousdecline.CurrentdowntochargeandsuspendthecurrentIoct,thebatterycapacityhasreached100%ofratedcapacity,thechargeroutputvoltagedropstoalowerfloatvoltageVF.3.2ProtectionModuleChipblockdiagramoftheinternalprotectioncircuitshowninFigure3.Thecircuitincludescontrollogiccircuit,samplingcircuit,overchargedetectioncircuit,over-dischargedetectioncomparator,overcurrentdetectioncomparator,loadshort-circuitdetectioncircuit,level-shiftingcircuitandreferencecircuit(BGR).Over-currentdetectioncomparator2LoadshortdetectioncircuitOver-currentdetectioncircuitOver-currentdetectioncomparator1OverchargedetectioncomparatorLevelconversioncircuitOver-currentdetectioncomparator2LoadshortdetectioncircuitOver-currentdetectioncircuitOver-currentdetectioncomparator1OverchargedetectioncomparatorLevelconversioncircuitControllogiccircuitOverdischargedetectioncomparatorSamplingcircuitFigure3BlockdiagramofbatteryprotectionThismoduleconstitutesaprotectioncircuitshowninFigure4.Underthechipsupplyvoltagewithinthenormalscopeofwork,andtheVMpinvoltageattheovercurrentdetectionvoltage,thebatteryisinnormaloperation,thechargeanddischargecontrolofthechiphighpowerendoftheCOandDOarelevel,whenthechipisinnormalworkingmode.LargerwhenthebatterydischargecurrentwillcausevoltageriseoftheVMpinattheVMpinvoltageatabovethecurrentdetectionvoltageViov,thenthebatteryisthecurrentstatus,ifthisstatetomaintainthetiovovercurrentdelaytime,thechipbanonbatterydischarge,thenthechargetocontroltheendofCOishigh,thedischargecontrolsideDOislow,thechipisinthecurrentmode,generalinordertoplayonthebatterysaferandmorereasonableprotection,thechipwillbatteryover-dischargecurrenttotakeoverthedischargecurrentdelaytimeprotection.Thegeneralruleisthattheover-dischargecurrentislarger,overtheshorterthedischargecurrentdelaytime.AboveOverchargedetectionvoltage,thechipsupplyvoltage(Vdd>Vcu),thebatteryisinoverchargestate,thisstateistomaintainthecorrespondingoverchargedelaytimetcuchipwillbeprohibitedfromchargingthebattery,thendischargecontrolendDOishigh,andchargingcontrolterminalCOislow,thechipisinchargingmode.Whenthesupplyvoltageofthechipundertheoverdischargedetectionvoltage(Vdd<Vdl,),thenthebatteryisdischargedstate,thisstateremainstheoverdischargedelaytimetdlchipwillbeprohibitedtodischargethebatteryatthistimeThechargecontrolsideCOishigh,whilethedischargecontrolterminalDOislow,thechipisindischargemode.ProtectionmoduleProtectionmoduleFigure4Protectioncircuitapplicationschematicdiagram4.CircuitDesignTwochargeprotectionmodulestructurediagram,thecircuitcanbedividedintofourparts:thepowerdetectioncircuit(under-voltagedetectioncircuit),partofthebiascircuit(samplingcircuit,thereferencecircuitandbiascircuit),thecomparator(includingtheoverchargedetection/overdischargedetectioncomparator,over-currentdetectionandloadshort-circuitdetectioncircuit)andthelogiccontrolpart.Thispaperdescribestheunder-voltagedetectioncircuit(Figure5),andgivesthebandgapreferencecircuit(Figure6).OutputcircuitdifferenceamplifierBleedercircuitReferencecircuitOutputcircuitdifferenceamplifierBleedercircuitReferencecircuitBiasingcircuitFigure5Under-voltagedetectioncircuitAmplifierAmplifierAmplifierAmplifierFigure6AreferencepowersupplycircuitdiagramBatterycharging,voltagestabilityisparticularlyimportant,undervoltage,overvoltageprotectionisessential,thereforeintegratedovervoltage,undervoltageprotectioncircuitinsidethechip,toimprovepowersupplyreliabilityandsecurity.Andprotectioncircuitdesignshouldbesimple,practical,heredesignedaCMOSprocess,theundervoltageprotectioncircuit,thissimplecircuitstructure,processandeasytoimplementandcanbeusedashigh-voltagepowerintegratedcircuitsandotherpowerprotectioncircuit.UndervoltageprotectioncircuitschematicshowninFigure5,atotaloffivecomponents:thebiascircuit,referencevoltage,thevoltagedividercircuit,differentialamplifier,theoutputcircuit.Thecircuitsupplyvoltageis10V;theM0,M1,M2,R0istheoffsetportionofthecircuittoprovidebiastothepost-stagecircuit,theresistance,Ro,determinethecircuit'soperatingpoint,theM0,M1,M2formacurrentmirror;R1M14isthefeedbackloopoftheundervoltagesignal;therestoftheM3,M4andM5,M6,M7,M8,M9,M10,M11,M12,M13,M14,composedoffouramplificationcomparator;M15,DO,areferencevoltage,thecomparatorinputwiththeinvertinginputisfixed(V+),partialpressureoftheresistanceR1,R2,R3,theinputtotheinvertinginputofthecomparator,whenthenormalworkingofthepowersupplyvoltage,theinvertingterminalofthevoltagedetectionislosttotheinvertingterminalvoltageofthecomparatorisgreaterthanV+.Comparatoroutputislow,M14cutoff,feedbackcircuitdoesnotwork;undervoltageoccurs,thevoltagedividerofR1,R2,R3,reactionismoresensitive,losttotheinvertinginputvoltageislessthanVwhentheresistordivider,thecomparatortheoutputvoltageishigh,thissignalwillbeM14open,thevoltageacrossRintoMatbothendsofthesaturationvoltagecloseto0V,therebyfurtherdrivingdowntheR1>R2,thepartialpressureoftheoutputvoltage,theformationoftheundervoltagepositivefeedback.Output,undervoltagelockout,andplaysaprotectiverole.5.SimulationresultsandanalysisThedesignofthecircuitinCSMC0.6μmindigitalCMOSprocesssimulationandanalysisofthecircuit.Intheoverallsimulationofthecircuit,themainobservationisthattheprotectionmoduleonthebatterychargeanddischargeprocessbymonitoringVddpotentialandVmpotentialleavingchipCOsideandDO-sidechangesaccordingly.ThesimulationwaveformdiagramshowninFigure7,theoverallprotectionmodulewiththebatteryvoltagechangesfromtheusualmodeconversionintooverchargemode,andthenreturntonormalworkingmode,andthenintothedischargemode,andfinallybacktonormalworkingmode.Asthedesignintheearlystagesofthevariousparameterstobeoptimized,buttoprovideapreliminarysimulationresults.Figure7Overvoltageandunder-voltageprotectioncircuitsimulationwaveform6.ConclusionDesignedasetofbatterychargingandprotectionfunctionsinoneIC.Thisdesignnotonlycanreducetheproduct,theycanreducetheperipheralcircuitcomponents.Thecircuitusesthelow-powerdesign.Thisprojectisunderwaytodesignoptimizationstage,acompletesimulationcannotmeettherequirements,butalsoneedtooptimizethedesignofeachmodulecircuit.光伏系統中蓄電池的充電保護IC電路設計曾德友，凌朝東，李國剛〔華僑大學元順集成電路研發中心，福建泉州362021〕來源：微電子器件與技術2007年第6期太陽能作為一種取之不盡、用之不竭的能源越來越受到重視。太陽能發電已經在很多國家和地區開始普及，太陽能照明也已經在我國很多城市開始投入使用。作為太陽能照明的一個關鍵局部，蓄電池的充電以及保護顯得尤為重要。由于密封免維護鉛酸蓄電池具有密封好、無泄漏、無污染、免維護、價格低廉、供電可靠，在電池的整個壽命期間電壓穩定且不需要維護等優點，所以在各類需要不間斷供電的電子設備和便攜式儀器儀表中有著廣泛的應用。采用適當的浮充電壓，在正常使用(防止過放、過充、過流)時，免維護鉛酸蓄電池的浮充壽命可達12~16年，如果浮充電壓偏差5%那么使用壽命縮短1/2。由此可見，充電方式對這類電池的使用壽命有著重大的影響。由于在光伏發電中，蓄電池無需經常維護，因此采用正確的充電方式并采用合理的保護方式，能有效延長蓄電池的使用壽命。傳統的充電和保護IC是分立的，占用而積大并且外圍電路復雜。目前，市場上還沒有真正的將充電與保護功能集成于單一芯片。針對這個問題，設計一種集蓄電池充電和保護功能于一身的IC是十分必要的。系統主要包括兩大局部:蓄電池充電模塊和保護模塊。這對于將蓄電池作為備用電源使用的場合具有重要意義，它既可以保證外部電源給蓄電池供電，又可以在蓄電池過充、過流以及外部電源斷開蓄電池處于過放狀態時提供保護，將充電和保護功能集于一身使得電路簡化，并且減少珍貴的而積資源浪費。圖1是此Ic在光伏發電系統中的具體應用，也是此設計的來源。圖1光伏電路系統框圖免維護鉛酸蓄電池的壽命通常為循環壽命和浮充壽命，影響蓄電池壽命的因素有充電速率、放電速率和浮充電壓。某些廠家稱如果有過充保護電路，充電率可以到達甚至超過2C(C為蓄電池的額定容量)，但是電池廠商推薦的充電率是C/20~C/3。電池的電壓與溫度有關，溫度每升高1℃，單格電池電壓下降4mV，也就是說電池的浮充電壓有負的溫度系數-4mV/℃。普通充電器在25℃處為最正確工作狀態；在環境溫度為0℃時充電缺乏；在45℃時可能因嚴重過充電縮短電池的使用壽命。要使得蓄電池延長工作壽命，對蓄電池的工作狀態要有一定的了解和分析，從而實現對蓄電池進行保護的目的。蓄電池有四種工作狀態:通常狀態、過電流狀態、過充電狀態、過放電狀態。但是由于不同的過放電電流對蓄電池的容量和壽命所產生的影響不盡相同，所以對蓄電池的過放電電流檢測也要分別對待。當電池處于過充電狀態的時間較長，那么會嚴重降低電池的容量，縮短電池的壽命。當電池處于過放電狀態的時間超過規定時間，那么電池由于電池電壓過低可能無法再充電使用，從而使得電池壽命降低。根據以上所述，充電方式對免維護鉛酸蓄電池的壽命有很大影響，同時為了使電池始終處于良好的工作狀態，蓄電池保護電路必須能夠對電池的非正常工作狀態進行檢測，并作出動作以使電池能夠從不正常的工作狀態回到通常工作狀態，從而實現對電池的保護。芯片的充電模塊框圖如圖2所示。該電路包括限流比擬器、電流取樣比擬器、基準電壓源、欠壓檢測電路、電壓取樣電路和邏輯控制電路。圖2充電模塊框圖該模塊內含有獨立的限流放大器和電壓控制電路，它可以控制芯片外驅動器，驅動器提供的輸出電流為20~30mA，可直接驅動外部串聯的調整管，從而調整充電器的輸出電壓與電流。電壓和電流檢測比擬器檢測蓄電池的充電狀態，并控制狀態邏輯電路的輸入信號。當電池電壓或電流過低時，充電啟動比擬器控制充電。電器進入涓流充電狀態，當驅動器截止時，該比擬器還能輸出20mA左右，進入涓流充電電流。這樣，當電池短路或反接時，充電器只能以小電流充電，防止了因充電電流過大而損壞電池。此模塊構成的充電電路充電過程分為二個充電狀態:大電流恒流充電狀態、高電壓過充電狀態和低電壓恒壓浮充狀態。充電過程從大電流恒流充電狀態開始，在這種狀態下充電器輸出恒定的充電電流。同時充電器連續監控電池組的兩端電壓，當電池電壓到達轉換電壓過充轉換電壓Vsam時，電池的電量己恢復到放出容量的70%~90%，充電器轉入過充電狀態。在此狀態下，充電器輸出電壓升高到過充電壓Voc，由于充電器輸出電壓保持恒定不變，所以充電電流連續下降。當電流下降到過充中止電流Ioct時，電池的容量己到達額定容量的100%，充電器輸出電壓下降到較低的浮