Loading...
Reverse Current/Battery Protection Circuits
The simplest protection against reverse battery protection is a diode in series with the battery as seen in Figure 1. +. LOAD. –. VBAT. –. Figure
AN1535: Prevent Reverse Charging of a Lithium Battery to Meet UL
Jul 14 2010 Figure 2 shows the actual circuit with the external protection diode. (Note that a high value series resistor would provide similar protection
Worked Examples from Introductory Physics (Algebra–Based) Vol
Jan 20 2008 4.2.5 Resistors in Series and in Parallel . ... sists of two opposite charges ±q separated by a distance which is usually taken to be “small ...
Automotive MOSFETs - Reverse Battery Protection by Marco Pürschel
Datasheet Explanation. Table of Contents. Page. Application Note. 2 The easiest way for reverse battery protection would be a series diode in the.
Protecting Automotive Motor Drive Systems from Reverse Polarity
The first technique for implementing reverse battery protection is to include a diode in series with the power supply path as shown in Figure 1 and Figure 2.
Experiment 21D THE ELECTROCHEMICAL ACTIVITY SERIES AND
Oct 20 2010 2- (aq) + 2 e- ? PbSO4 (s) + 2 H2O (l). (8). Figure 2. The Lead Storage Battery. The reverse reactions take place when the battery is ...
AP Physics 2 – Practice Workbook – Book 2 - Electricity Magnetism
2. A parallel–plate capacitor is charged by connection to a battery. If the battery is (A) acceleration in a direction opposite to that of the field.
WF-9800-AD SERIES
A battery does not have to be installed for WF-9800-AD Series Converter-Chargers operation. When a battery is installed two reverse polarity fuses are
Electrodialysis-Reverse Electrodialysis (ED-RED) Battery
Specifically Point 2/Energy storage by using ElectroDialysis/Reverse which can be cationic (CEM) or anionic (AEM)
batteries and chargers connected in series & parallel
Four Batteries in Series / Parallel (Example 2) Two Chargers . wire W1 must be connected to the opposite end of the battery pack as the black wire at.
67_8slva835 1SLVA835A-October2016-RevisedFebruary2019SubmitDocumentationFeedbackCopyright©2016-2019,TexasInstrumentsIncorporatedProtectingautomotivemotor-drivesystemsfromreversepolarityconditions(1)
Alltrademarksarethepropertyoftheirrespectiveowners.(1)ApplicationReportSLVA835A-October2016-RevisedFebruary2019Protectingautomotivemotor-drivesystemsfromreversepolarityconditionsMichaelBifalco.................................................................................AdvancedProtectionMotorDriversABSTRACT
Electronicsareintegratedintovirtuallyeverysystemofthemodernautomobile,fromsafetytoinfotainment.Nowmorethaneveritisimportantformanufacturerstobuildrobustprotectionintotheelectricalsystemsoftheirvehicles.Onedangerthatallelectricalsystemsfaceisareversedpolarityfromthepowersource.Thiseventcanbecausedbyashortcircuit,butisusuallycausedbysimplyswitchingthepowerandgroundterminalswhenconnectingapowersupply.Inthecaseofanautomobile,thepowerformostelectronicsissuppliedfromthebattery.Acarbatterythatisinstalledwiththeterminalconnectionsreversedcoulddamagetheelectricalsystemsiftheyarenotprotected.Theelectronicscouldalsobedamagefromreversepolarityifajump-startisattemptedwiththejumpercablesreversed.Severaltechniquesexistthatcanbeusedtoprovidereversebatteryprotectionwhendesigningelectricalsystems,butallhavethecommonpurposeofpreventingcurrentflowwhenthebatteryterminalsareconnectedinreverse.Contents
1Technique1:SeriesDiodeMethod.......................................................................................22Technique2:SingleFET...................................................................................................23Technique3:ICSolution....................................................................................................24Technique4:NMOSandBJT..............................................................................................34.1UsingTechnique4WithanIntegratedBoostRegulatorOrAnIntegratedChargePumpMotorDriveIC..............................................................................................................35ComparisonofPowerDissipation.........................................................................................5ListofFigures1ReverseBatteryProtectionWithDiodeatSupplyTerminal...........................................................22ReverseBatteryProtectionWithDiodeatGroundTerminal...........................................................23ReverseBatteryProtectionWithSupplySidePMOSFET.............................................................24ReverseBatteryProtectionWithGroundSideNMOSFET............................................................25ReverseBatteryProtectionWithBJTandNMOS.......................................................................36ReverseBatteryProtectionWithMotorDriveIC........................................................................47RegulatorVoltageversusVS..............................................................................................5
Power
PMOSVBATAutomotive
System
Supply
GND GND VBATPower
NMOSAutomotive
System
Supply
GND GNDAutomotive
SystemVBATSupply
GND GNDAutomotive
SystemVBATSupply
GND GNDTechnique1:SeriesDiodeMethodwww.ti.com2SLVA835A-October2016-RevisedFebruary2019SubmitDocumentationFeedbackCopyright©2016-2019,TexasInstrumentsIncorporatedProtectingautomotivemotor-drivesystemsfromreversepolarityconditions1Technique1:SeriesDiodeMethodThefirsttechniqueforimplementingreversebatteryprotectionistoincludeadiodeinserieswiththepowersupplypath,asshowninFigure1andFigure2.Ifthebatteryterminalsareconnectedinreverse,thediodewillbereversebiasedandwillnotallowcurrenttoflowthroughthesystem.Thistechniquepreventsthereversedpolarityconditionfromharmingtheelectronicsorthebattery.Figure1.ReverseBatteryProtectionWithDiodeatSupplyTerminalFigure2.ReverseBatteryProtectionWithDiodeatGroundTerminalThistechniqueiscosteffectiveasitrequiresonlyasinglediodetoimplementinthesimplestform,butitcomeswiththedrawbacksoflowerefficiencyandasmallerusablebatteryrangebecauseofthevoltagedropintroducedbythediode.Furthermore,thediodecouldoverheatinhigh-currentapplications.Aheatsinkcanbeaddedtothediodeormultiplediodescanbeconnectedinparalleltospreadoutthepowerdissipation,butbothofthesesolutionsincreasethecomponentcostandusevaluableboardspace.2Technique2:SingleFETAnothertechniqueforreversebatteryprotectionistoincludeapowerFETinserieswiththepowersupplypath.Eitherap-channelpowerFET(PMOS)orann-channelpowerFET(NMOS)canbeusedasshowninFigure3andFigure4.Whenproperlyconnected,thebatterywillbrieflyconductcurrentintothesystemthroughthebodydiodeoftheFETwhiletheFETisswitchingon.Afterwards,theFETconductsthecurrentwithanextremelylowonresistance.Whenthebatteryisconnectedinreverse,theFETwillbeoffineitherimplementationandnocurrentcanflow.Thistechniquehelpsprotectthesystemandthebatteryfromthereversedpolaritycondition.Figure3.ReverseBatteryProtectionWithSupplySidePMOSFETFigure4.ReverseBatteryProtectionWithGroundSideNMOSFETThistechniqueismoreefficientthanusingonlyadiodebecauseofthelowRdsonofpowerMOSFETs.WithanRdsonvalueinthetensofmilliohmsorlower,thevoltagedropintroducedbytheFETisoftenfarlowerthantheforwardvoltageofadiode,resultinginbetterefficiency,lowerlossofusablebatteryvoltage,andlessheat.However,usingthiscircuithassomedrawbacks.TheRdsonofaPMOSishigherthanthatofanNMOSofthesamesize,soanNMOSisusuallythebetterchoicefromacostperspective.ThegroundsideNMOSimplementationcanliftupthegroundreferencewhichcouldaffectsensitivecircuits.
3Technique3:ICSolutionIntegratedcircuitsdesignedspecificallytoaccomplishreversebatteryprotectionarealsoanoptioninanautomotivesystem.TexasInstruments'LM74610-Q1orLM74700-Q1smartdiodecontrollersareexamplesofthosetypeofdevices.Forareferencedesignusingthosedevices,gotowww.ti.com/tool/PMP9498orwww.ti.com/tool/DRV8912-Q1EVM.
Automotive SystemSupply
OVERDRIVE
VBAT R limitR BASEwww.ti.comTechnique4:NMOSandBJT3SLVA835A-October2016-RevisedFebruary2019SubmitDocumentationFeedbackCopyright©2016-2019,TexasInstrumentsIncorporatedProtectingautomotivemotor-drivesystemsfromreversepolarityconditionsIfthemotordriveICdoesn'thaveanexternalaccessiblehighsidesupplytoprovideareverseprotectionswitchingcontrolsignal,suchas:DRV8912-Q1,theabovethreetechniquescanbeadoptedfortheinputsourcereverseprotection.4Technique4:NMOSandBJTThecircuitinFigure5makesuseofapowerNMOSandanNPNbipolarjunctiontransistor(BJT)toachievereversebatteryprotection.Ifthebatteryisconnectedinreverse,thebodydiodeoftheNMOSwillnotconductcurrentnorwilltheNMOSturnon,therebyprotectingthesystemfromthereversepolaritycondition.Whenthebatteryisconnectedcorrectly,thecircuitpermitscurrenttoflowwithverylittlepowerlostbecauseofthelowRdsonoftheNMOS.Figure5.ReverseBatteryProtectionWithBJTandNMOSForthepowerNMOStoturnon,thegatevoltagemustbehigherthanthesourcevoltagewhichcannotbeaccomplishedwithVBATalone.ThereforethegateistiedtoasignalcalledOVERDRIVE,representingagatedrivingvoltage.Thistechniqueusuallyrequiresadditionalcircuitrytoproduceasuitablegate-to-sourcevoltagetoturnontheNMOS,oftenintheformofachargepumporboostregulator.TheBJTisusedtogroundtheNMOSgateduringthereversepolarityconditiontoensuretheNMOSturnsoff.Whenthebatteryisconnectedcorrectly,thebasevoltageislowerthanthecollectorandemittervoltagessotheBJTwillbeoff.Whenthebatteryterminalsareconnectedinreverse,thegroundnodebecomesthepositivebatteryterminalandtheVBATnodebecomesthenegativebatteryterminal.ApositivevoltageispresentfromthebasetotheemitteroftheBJT,sotheBJTwillturnonwhichconnectstheNMOSgatetogroundthroughtheBJTandturnsofftheNMOS.Theresistor,RBASE,isusedtolimitthecurrentintothebaseoftheBJT,andthediodepreventscurrentfromenteringtheBJTwhenthebatteryisconnectedcorrectly.ThelowRdsonoftheNMOSresultsinexcellentefficiencyandlesslossinbatteryvoltagerangefromtheprotectioncircuit.ThistechniquealsoremovesthedisadvantageofliftingthegroundupthatiscausedbythesingleNMOSsolution.4.1UsingTechnique4WithanIntegratedBoostRegulatorOrAnIntegratedChargePumpMotorDriveICThistechniqueisparticularlywell-suitedformotordriveapplications.ManyTImotordrivedevicesincludeintegratedboostregulatordeviceDRV3205-Q1andintegratedchargepumpdevices,suchas:DRV3245Q-Q1,DRV8343-Q1,DRV8703-Q1andDRV8873-Q1cansupporttherequiredoverdrivevoltagefortheNMOSgatewithouttheneedforadditionalexternalcircuitry.Figure6showsthecircuitforreversebatteryprotectionusingamotordrivedevice.
Technique4:NMOSandBJTwww.ti.com4SLVA835A-October2016-RevisedFebruary2019SubmitDocumentationFeedbackCopyright©2016-2019,TexasInstrumentsIncorporatedProtectingautomotivemotor-drivesystemsfromreversepolarityconditionsFigure6.ReverseBatteryProtectionWithMotorDriveICThebodydiodeoftheFETallowscurrenttoflowintothedeviceinitially,allowingthedevicetopoweron.Whenthedeviceispoweredon,theboostregulatoroutputBOOSTorthechargepumpoutputVCPprovidesavoltageabovethesupplyvoltagewhichishighenoughtoturnonthereverseblockingFET,ensuringlowRdsontomaximizeefficiencyofthereversebatteryprotectioncircuit.Tominimizecostandsimplifythebillofmaterials(BOM),thesamepowerNMOSmodelusedforthehalfbridgesofthedriverstagecanbeusedasthereversebatteryprotectionNMOS.AsystemdesignermustselectaBJTthatsupportsthedifferentvoltagesitcanbeexposedtointhesystem.Whenthebatteryisconnectedcorrectly,thecollector-to-emittervoltageoftheBJTiseffectivelythesameastheBOOSTorVCPpinvoltageiswithrespecttosupply.MostBJTsdesignedforpowerapplicationscanacceptthatlevelofcollector-to-emittervoltage.TheBJTmustalsohaveasufficientlylargecollector-to-basevoltagespecificationtoavoiddamagefromtheBOOSTorVCPpinvoltage.Thisvoltagespecificationisrequiredbecausethebasewillremaingroundedwhenthebatteryisconnectedcorrectly,buttheBOOSTorVCPpinoutputwillincreasewithrespecttogroundasthesupplyincreases.Forexample,theDRV8703-Q1willregulateat24Vwhenthebatteryis14V(typical)sotheBJTmustsupportatleast24Vfromcollectortobase.WhenselectingtheBJT,alsoconsiderautomotiveconditionssuchasloaddumpthatcaneffectthevoltagesthatthesystemisexposedto.Whenthebatteryisconnectedinreverse,thespecifiedbase-to-emittervoltagemustbegreaterthanthebatteryvoltagebecausethebatteryvoltagewillappearfrombasetoemitter.Thebaseresistormustbeselectedtolimitthecurrentintothebase.MostBJTdatasheetsrecommendaresistorofafewkilo-Ohms.TheresistorbetweentheBOOSTorVCPpinandthegateoftheFETshouldbesizedsothattheexternalcurrentlimitoftheBOOSTorVCPpinisnotexceeded,includinganyadditionalloadfromotherexternalcircuitry.Asanexample,assumethatthecurrentislimitedtohalfthemaximumexternalloadtogivemarginforpoweringotherexternalloadsinthesystem.ForDRV8703-Q1,thiscurrentlimitis12mAandthetypicalvoltageis10Vabovesupply.TheBJTwillbeincutoffmodewhenthebatteryisconnectedcorrectly,socurrentwillbesourcedonlyintothegateoftheFET.UseEquation1tocalculateavalueforthecurrentlimitingresistor(Rlimit).
VS (V)
Regulator Voltage (V)
46810121416182022248
10 12 14 16 18 20 2224
26
28
30
32
34
36
3840
D001 BOOST VCPH VREG
www.ti.comComparisonofPowerDissipation5SLVA835A-October2016-RevisedFebruary2019SubmitDocumentationFeedbackCopyright©2016-2019,TexasInstrumentsIncorporatedProtectingautomotivemotor-drivesystemsfromreversepolarityconditions(1)
Forotherdevices,BOOSTorVCPpincanprovidedifferentoutputcurrentlimitandvoltage,pleasecheckthedatasheetandEVMdesignfiletoadjustthevalue.Theslewrateofthechargepumporboostregulatoratstartupwillalsolimitthecurrent.TheFETwilltakelongertoturnonforlargervaluesofRlimit,whichdecreasesefficiencyatstartup.Allowingforalargercurrentlimitwhenpossiblewillimprovetheefficiency.AsshowninFigure7,bothintegratedboostregulatoroutput(suchas:DRV3205-Q1)orintegratedchargepumpoutputVCP(suchas:DRV8703-Q1)arereferencedtotheinputsupplyandincreaseasitincreases.EitheroftheseregulatorscouldsupplytheVGSrequiredtoturnontheNMOSevenasthesupplyvoltagechanges.
Figure7.RegulatorVoltageversusVS5ComparisonofPowerDissipationAcomparisonofthepowerdissipationofthedifferentcircuitscanbemadebychoosingacurrentandsolvingforthepower.Foranexample,assumethat10mAflowsintothedeviceDRV8703-Q1.ForTechnique1,iftheforwardvoltageofthediodeis300mV,useEquation2tocalculatethepowerdissipation(PD).
ComparisonofPowerDissipationwww.ti.com6SLVA835A-October2016-RevisedFebruary2019SubmitDocumentationFeedbackCopyright©2016-2019,TexasInstrumentsIncorporatedProtectingautomotivemotor-drivesystemsfromreversepolarityconditions(2)
ForTechnique2,eitheraPMOSorNMOScanbeused.Witha10-mAcurrent,andassumingaPMOSwithRdsonof10m,useEquation3tocalculatethePD.(3)
Ingeneral,aPMOSwillhaveahigherRdsonforthesamearea(andthereforeahighercost)asanNMOS.Witha10-mAcurrentandanNMOSwitha2-mRdson,useEquation4tocalculatethePD.(4)
Technique4willhavenearlyidenticalperformanceasthesingleNMOScase.Thepowerdissipatedacrossthecurrentlimitingresistoratstartupisnegligible.UsinganNMOSoveraPMOSordiodeforreversebatteryprotectionhasaclearpoweradvantage.TheimprovementinpowerdissipationofferedbyTechnique4isclearwhenconsideringthatthecurrentoftheentiresystemflowsthroughthereversepolarityprotectioncircuit.Forexample,iftheaveragesystemcurrentis20AtheNMOSwilldissipateonly0.8W,whilethesinglediodesolutioninTechnique1woulddissipate6W.Thediodesolutioncontributessignificantlymoreheatanddrivestheefficiencyofthesystemdown.