Building Your Own Battery Simulator - TI.com

1 ApplicationReportSLVA618 October2013 BuildingYourOwnBatterySimulatorRushilKKA BSTRACTUsea poweramplifiercircuitwithTI single-cellLi-ionbatterychargersto RIN CINtimeconstantat its input,the outputof the poweramplifierbothsourcesand characterizethe entirechargingprofileof the chargerby tyingthe outputof the batterychargerto the the the 1 A, BatterySimulatorRIN CINTimeConstantof 2 850 mA, V, BatterySimulatorTimeConstantof 2 of the CircuitBatteriesare ratedin 2-A batterychargerrequiresapproximatelyone hourto chargea 2000-mAHrbattery,longerwhenincludingthe effectsof the connectorresistanceand the internalresistanceofthe is inefficientto evaluatechargerperformanceby waitingone hourto chargeand additionaltime to dischargethe batteryfor applicationnoteexplainshow to makea circuitthat can providean observablyslowoutputdv/dt,whilesinkingth e entire2-A chargecurrentthat showsthe poweroperationamplifierand additionalcircuitryneededto makethe October2013 BuildingYourOwnBatterySimulatorSubmitDoc umentationFeedbackCopyright 2013.

2 TexasInstrumentsIncorporatedR2 VBIAS 12 R1 R2 K +RBASE1 kORIN200 kOCIN10 FRE50 kOR1980 kOR2220 kO100 nF10 F10 uF100 nFa+J+JQ1 FMMT2222AJ12 V+12 VU1 OPA544 BAT+VIN+VIN-BATJVBIAS+12 VExplanationof the BatterySimulatorCircuit2 Explanationof the first stageof the circuitcomprisesa chargingcircuitof RIN CIN. In Figure1, the valueschosenareRIN= 200 k and CIN= 10 F, givinga time constantof RIN CIN= 2 s. Userscan slowercharging,increasethe valueof RIN CIN, and for fastercharging,decreasethe valueof RIN voltagedevelopedacrossthe capacitorCINis fed to an collectorterminalof the transistorconnectsto the + emitterconnectsthroughan emitterresistanceREof 50 k to createa biasingvoltage, voltagesimulatesthe internalprotectionmechanismof mostLiIonbatteriesto ensurethat the batteryvoltageneverfalls belowa certainlevel(usually2 to V).

3 The usercan adjustthe VBIAS voltagethroughthe resistordividerformedby R1 and R2.(1)Changethe valueof VBIASby varyingR2. R2 can be a potentiometerto facilitatechangingthe :A Zenerdiodeand seriesresistorwith breakdownvoltageof V (for examplePMLL5230B)can be connectedfromthe junctionof R1 and R2 to connectionpreventsthe voltageat BAT+fromexceedingthe maximumvoltageof the October2013 SubmitDocumentationFeedbackCopyright 2013, outputof the sourcefolloweris fed to the non-invertingterminalof the OPA544unity-gain,stable-poweramplifier,w hichcan comfortablysourceand sink currentsof up to 4 A. This unity-gainconfiguredOPA544amplifieris suppliedwith +12 V and 12 V. The outputof the OPA544is connectedto the BAT+terminalof the Powerthe OP-AMPcircuitwith +12 V and 12 V.

4 The outputvoltagemustbe almostequalto ApplyDC voltagebetweenthe VIN+and VIN the examplecircuit,an inputDC voltageof V is requiredin orderto get a final outputvoltageof V. The usermay haveto find theexactvalueof VIN by trial and error,to providethe exactfinal outputvoltagethat the the choiceof transistorand Whenthe inputvoltageis applied,the voltageacrosscapacitorCINstartsrisingfro m0 V. The outputvoltageshouldnot followthe voltageacrosscapacitorCIN, until it exceedsVBIAS(plusvoltageacrossbase-emitt erjunction).4. Afterthe voltageacrossthe capacitordoesexceedVBIAS(plusvoltageacro ssbase-emitterjunction),the outputvoltageBAT+followsCINup to the final Connectthe BAT+and BAT terminalsto a batterychargerto observethe chargecurrentwith anoscilloscopeand the behaviorof the chargerat October2013 BuildingYourOwnBatterySimulatorSubmitDoc umentationFeedbackCopyright 2013, 1 A, BatterySimulatorRIN CINTimeConstantof 2 sFigure2.

5 ChargeProfileObtainedUsingthe 850 mA, V, BatterySimulatorTimeConstantof 2 sFigure3. ChargeProfileObtainedUsingBatterySimulat orCircuitWithbq24157 Charger5 ConclusionUse the circuitdescribedin this applicationnoteto createthe chargeprofilefor single-cellbatterychargers,as shownin the October2013 SubmitDocumentationFeedbackCopyright 2013,TexasInstrumentsIncorporatedIMPORTA NTNOTICET exasInstrumentsIncorporatedanditssubsidi aries(TI)reservetherighttomakecorrection s,enhancements,improvementsandotherchang estoitssemiconductorproductsandservicesp erJESD46,latestissue,andtodiscontinueany productorserviceperJESD48, (alsoreferredtohereinas components ) aresoldsubjecttoTI s ,in accordancewiththewarrantyin TI s ,testingofallparametersofeachcomponentis productsandapplications, ,eitherexpressorimplied,is grantedunderanypatentright,copyright,mas kworkright,orotherintellectualpropertyri ghtrelatingtoanycombination,machine,orpr ocessin licensetousesuchproductsorservicesora licensefroma thirdpartyunderthepatentsorotherintellec tualpropertyofthethirdparty,ora TIdatabooksordatasheetsis permissibleonlyif reproductionis withoutalterationandis accompaniedbyallassociatedwarranties,con ditions,limitations, is solelyresponsibleforcompliancewithallleg al,regulatoryandsafety-relatedrequiremen tsconcerningitsproducts,andanyuseofTIcom ponentsin itsapplications.

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