基于单片机的智能手机充电器的设计.docx
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基于单片机的智能手机充电器的设计
基于单片机的智能手机充电器的设计
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ImprovementsinBatteryChargerICsKeepPacewithRapidIncreasesinMobileHandsetCapabilities
Intheeraofglobalwirelessconnectivity,almostnothingismoreimportantthankeepingasmartphoneormobileInternetdevicecharged.ExpandingfeaturesontheconstantlyimprovingportableandhandhelddevicecreateamajorchallengefordesignersofbatterychargerICs.Highresolutionscreensandlargermemoriescombinewithnewcapabilitiestotaxthebattery,requiringbatterychargertechnologythatisnotonlymoreefficientbutalsocapableofmanagingpowerdistribution.
Optimizingpowerconsumptiontoprolongbatterylifehasalwaysbeenadrivingforceinhandheldpowermanagement.Howeverwhatischangingaretheefficiencyexpectationsforcharginghandhelddeviceswhentheyarepluggedintothewall.Thelatestgenerationsofdevicedesignsareusinghigh-efficiencyswitchingchargersinplaceoftraditionallinearchargers.Customerstodaycontinuetodemandshorterchargecycleswhenchargingtheirbattery.Besidehigherefficiencywithrespecttotheconventionallinearchargers,oneofthegreatadvantagesofusingswitchingchargerssolutionisthecapabilitytoboostthechargecurrentfromwhatsuppliedbythesource.ThisisespeciallyimportantwhenpoweringoffofaUSBportwherethecurrentavailablemightbelimitedtolessthan500mA.Higherchargecurrentsequatetoshorterchargecyclesthussatisfyingcustomerexpectations.
Therearetwokindsofbatterychargersusedinmosthandheldsnow–linearchargersandswitchingdevices.Linearchargershavealongerhistory.Theyhavetypicallyprovidedarelativelyefficient,simplewaytochargeportabledevices,creatingminimalnoisewithoutmanyexternalcomponents.Butasportabledevicesbecomemorecomplexandaddlayersofnewfeatures,theyneedhigherbatterycapacity.Linearchargerspresentliabilitiesduetopowerdissipation,whichbecomeclearifauserwantstochargeadevicewhileusingatthesametime.Theheatgeneratedwhilesimultaneouslyusingandchargingcandamagethesystemorbattery.Notagoodoutcome.
Thealternativeisaswitchingdevice,orswitchmodebatterychargerIC,thatcandeliverhighercurrentlevelstoabatterywhilerequiringaslittlepoweraspossible.Historically,therehavebeensomenoiseissueswiththesekindsofICs.Inaddition,someearlygenerationsofswitchmodedeviceshaverequiredseveralexternalcomponents.
However,thebenefitsoftheswitchedmodebatterytopologyareclear.Theyincludehigherefficiencyandlowerpowerdissipation,alongwithfastchargingcycles.Thesedevicesalsoarecapableofchargingfromhigherinputvoltages,whichallowstheuseoflowercostunregulatedadapters.Theycanincreasethechargingcurrentfromcurrentrestrictedsources.
Thenoisefromswitchingchargersusuallycomesduringlightloadoperation,particularlyduringpreconditioning.Asitdecreases,manyswitchingchargersmoveintoanoperationknownaspulseskipping.Inpulseskipping,thePWMfrequencychangesasynchronously.TherehavebeenbatterychargerICsdevelopedthatsupplyhighchargecurrentwithminimalthermalimpacttothesystemusingaswitchingcharger,thenswitchintoalinearchargerduringlowcurrentchargingmodestominimizenoise.ThistypeofPWMswitchmodechargerwithalinearmodehasbeenagooddevelopment,providinghighefficiencyatthefullconstantcurrent（fastcharge）rate.Theswitchingchargercontrolslargeconstantcurrentcharge（upto2A）withaPWMswitchingregulator.Itautomaticallymovestolinearmodewhilethebatteryispreconditioningandneartheendofconstantvoltagetaperchargemode,whichlowersthenoisewhiletheswitchmodespeedsupcharging.Oncethechargecurrentleveldipsbelow300mA,thelinearmodekicksincompletelyandnoisegeneratedbytheswitchingconverteriseliminated.
Butnowtherearefurtheradvances.Forexample,anidealsolutionfornewhandheldsisacompletechargerforsinglecellLi+/Polymerbatterieswithupto1Achargecurrentandadvancedindicationcapabilitiesforfullchargesystemmonitoring.USBCompliant100mA/500mAchargecurrentsettingsarebeneficialasareprogrammablepre-chargeandfastcharge.Manyproductsalsoincludebatterytemperaturemonitoring,whichensuressafecharging.
CompaniessuchasIntersilareleadingthedevelopmenteffortfornewgenerationsofchargerICs.Thesefullyintegratedsolutionsservecompactapplicationsandprovidechargecontrollersforhigherpowerapplications.Chargevoltageaccuracyisnowat0.5percent,animprovementoverjustafewyearsago,whenanaccuracyratingof1percentwasconsideredgood.Switchingfrequenciesareupto3MHzandnewswitchingchargersnowprovideupto2Achargecurrent,withonerecentexamplebeingtheISL9220,whichissuitableforboth1and2cellsLiIonapplications.
Inaddition,newdesignsrestrictleakage--thereisnolessthan0.5uAtypicalleakagecurrentoffthebatterywhennoinputpowerisattached.Theseimprovementsalsohavebecomeavailableinsmallerandsmallerpackages,suchas4x4mmQFNsor2x2mmCSPs,whichsaverealestateinspace-constrainedhandheldequipment.
ThelatestbatterychargerICsalsoareabletomonitortheinputvoltage,thebatteryvoltage,andthechargecurrent.Whenanyofthethreeparametersexceedsspecificlimits,theICturnsoffaninternalN-channelMOSFETtoremovethepowerfromthechargingsystemtothebattery.Thiskindofflexibleefficiencyisanotheroftheimprovementsnowavailableintheseimportantdevices,whicharevitaltothecontinuinggrowthandfeaturesetexpansionofmobile,handheldproducts.
【作者】Marino,Giampaolo;Schmitz,Tamara
【刊名】ElectronicComponentNews
【出版日期】2010
【卷号】Vol.54
【期号】No.1
【页码】16
DESIGNANDIMPLEMENTATIONOFAMICROCOMPUTER8051SYSTEMPOWEREDBYDUALBATTERIESCHARGEDBYSOLARCELLS
Abstract
Single-chipmicrocomputersystemsarebecomingincreasinglypopularincurrentcontrolandinformationapplications.However,duetotheirbatteryenergylimitations,thesesystemshaveaveryrestrictedoperationtimeorrechargecycleifasinglerechargeablebatterysuppliestheirpower.Weproposeadesignandimplementationforthesoftwareandhardwareofamicrocomputer8051systempoweredbyadualrechargeablebatterythatischargedbysolarcells.Fromafeasibilityanalysisofthequeueingmodelforthestochasticcharginganddischargingprocessofthedualbatterysystem,duetotherandomcharacteristicsofweatherconditionsandusers'operationalbehavior,weconfirmthattheaverageoperationtimeforthismodelcanbemuchlongerthanthatofasinglerechargeablebatterypowersupply.Theexperimentalresultsofourdesignalsoshowapproximatelythesameresultsasourmodel.Withatwo-thirdsutilizationratio,wecanobtainanaverageoperationtimefourtimesaslongintheoreticalresults,andthreeandhalftimesaslonginexperimentalresultsthanwithasinglerechargeablebatterypowersupply.Inaddition,thetechnologytrendshowsthatthepowerconsumptionrateforatypicalmicrocomputersystemisdecreasingandthepowergenerationefficiencyfortypicalsolarcellsisincreasing.Hence,solarcellsasthepowerchargingsourcesforamicrocomputer8051systemsuppliedbyadualrechargeablebatterycanbefeasibleinthenearfuture.
Overthepastfewyears,microcomputersystemdesignresearchershavebeenworkingwithdifferentlevelsoflow-powertechnology.Intermsofsystem,circuits,anddevicepowersaving,theresultsshowthateveryyearfrom1992to1997theaveragepowerconsumptionofamicrocomputercomputerdecreasedmorethan20%,andfrom1998to2001itdecreasedby10%.Reducingpowerconsumptionisimportantbecauseofitspotentialtoextendtherechargeperiodofportableinformationapplications.Thelongerthebatteryoperationtimebeforearechargeisneeded,themoreconvenientitisformobileuserstooperateaportablemicrocomputersystem.
Eventually,thepowerconsumptionofasingle-chipmicrocomputersystemwillbesmallenoughtobesuppliedorrechargedbyotherpowersources.Oneoftheproposedpowersourcesismechanicalvibration.Amongothers,wepreviouslyproposedsolarcellsthatcanbeusedaspowersupplysources.Althoughcurrentmc-Sisolarcellpowergenerationefficiencyisnothighenough,theirefficiencyincreasedfrom14.2%to16.8%from1990to1997.Thisimprovementcanreducethegapbetweenthecharginganddischargingrateofthepowersupplyofamicrocomputersystem,sotheprobabilityofpowerexhaustionwithinacertainoperationaltimeisreducedeachyear.
Toprolongthebatteryoperationtimebeforerecharging,inthisarticlewepresentthesoftwareandhardwaremoduleforasingle-chipmicrocomputer8051systemwithadualbatterychargedbysolarcells.Basedonitsdesignandimplementation,thisworkalsopresentstheestimationforpowerexhaustionprobabilityandtheexperimentalmeasurementforoperati
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