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.

2 Whilesinkingthe entire2-A chargecurrentthat showsthe poweroperationamplifierand additionalcircuitryneededto makethe October2013 BuildingYourOwnBatterySimulatorSubmitDoc umentationFeedbackCopyright 2013,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.

3 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).

4 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.

5 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. 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.

6 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.

7 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 )

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