其中，LED电源批发隧道，支持12Vdc或12Vac电源输入，削弱了LED的优势。因而无电解电容LED驱动解决方案就有很大的吸引力。图1为美芯晟科技推出的基于MT7920的无电解电容LED驱动解决方案。
该方案中，节约的电能就越多，图4对能效与电流负载进行了对比分析。在全负载时，研究路灯节能控制系统，
Allegro公司的A8735是超低功耗Xenon闪光灯充电集成电路,封装尺寸只有2x2mm,关断模式的电流仅为0.5uA,峰值电流1A限制,效率大于75%,很适合用于手机单个锂离子电池充电以及小型照相机.本文介绍了A8735主要特性和优势,功能方框图,典型应用电路图以及推荐的PCB布局图.
TheAllegro
A8735isaXenonphotoflashchargerICdesignedtomeettheneedsofultralowpower,smallformfactorcameras,particularlycameraphones.Byusingprimary-sidevoltagesensing,theneedforasecondary-sideresistivevoltagedividerisELiminated.Thishastheadditionalbenefitofreducingleakagecurrentsonthesecondarysideofthetransformer.Toextendbatterylife,theA8735featuresverylowsupplycurrentdraw(0.5μAmaxinshutdownmode).TheIGBTdriveralsohasinternalgateresistorsforminimumexternalcomponentcount.Thechargeandtriggervoltagelogicthresholdsaresetat1VHI(min)tosupportapplicationsimplementinglow-voltagecontrollogic.
TheA8735isavailableinan8-contact2mm×2mmDFN/MLPpackagewitha0.60maximumoverallpackageheight,andanexposedpadforenhancedthermalperformance.Itislead(Pb)freewith100%mattetinleadframeplating.
A8735主要特性和优势:
?Ultrasmall2×2DFN/MLP-8package
?Lowquiescentcurrentdraw(0.5μAmax.inshutdownmode)
?Primary-sideoutputvoltagesensing;noresistordividerrequired
?Fixed1Apeakcurrentlimit
?1Vlogic(VHI(min))compatibility
?IntegratedIGBTdriverwithinternalgateresistors
?Optimizedformobilephone,1-cellLi+batteryapplications
?Zero-voltageswitchingforlowerloss
?>75%efficiency
?Chargecompleteindication
?Integrated50VDMOSswitchwithself-clampingprotection
图1.A8735功能方框图
图2.A8735单电源应用电路图
图3.A8735带单独偏压电源的应用电路图
图4.A8735推荐的应用电路图
图5.A8735推荐的元件布局图
详情请见:
http://www.allegromicro.com/en/Products/Part_Numbers/8735/8735.pdf
Semtech公司的SX1507,SX1508和SX1509是超低功耗4/8/16路通用并行输入/输出(GPIO)扩展器,并集成了LED驱动器,工作电压1.2V-3.6V,主要用在手机,PDA,MP3播放器,数码相机,笔记本电脑,GPS和其它以电池为能源的设备.本文介绍SX1507,SX1508和SX1509主要特性,方框图,典型应用框图和电路,以及SX1508EVK评估板电路图和PCB布局图.
TheSX1507,SX1508andSX1509arecompleteultralowvoltage1.2Vto3.6VGeneralPurposeparallELInput/Output(GPIO)expandersidealforlowpowerhandheldbatterypoweredequipment.ThisfamilyofGPIOscomesin4-,8-,16-channelconfigurationandallowseasyserialexpansionofI/Othroughastandard400kHzI2Cinterface.GPIOdevicescanprovideadditionalcontrolandmonitoringwhenthemicrocontrollerorchipsethasinsufficientI/Oports,orinsystemswhereserialcommunicationandcontrolfromaremotelocationisadvantageous.
Thesedevicescanalsoactasalevelshiftertoconnectamicrocontrollerrunningatonevoltageleveltoacomponentrunningatadifferentvoltagelevel,thuseliminatingtheneedforextraleveltranslatingcircuits.Thecoreisoperatingaslowas1.425VwhilethedualI/Obankscanoperatebetween1.2Vand3.6Vindependentofthecorevoltageandeachother(5.5Vtolerant).
TheSX1507,SX1508andSX1509featureafullyprogrammableledDriverwithinternaloscillatorforenhancedlightingcontrolsuchasintensity(via256-stepPWM),blinkingandbreathing(fadein/out)makethemhighlyversatileforawiderangeofLEDapplications.Inaddition,keypadapplicationisalsosupportedwiththeon-chipscanningenginewhichenablescontinuouskeypadmonitoringupto64keyswithoutanyadditionalhostinteractionandfurtherreducethebusactivity.
TheSX1507,SX1508andSX1509havetheabilitytogeneratemask-programmableinterruptsbasedonfalling/risingedgeofanyofitsGPIOlines.Adedicatedpinindicatestoahostcontrollerthatastatechangeoccurredinoneormoreofthelines.
EachGPIOisprogrammablevia8-bitconfigurationregisterssuchasdataregisters,directionregisters,pull-up/pull-downregisters,interruptmaskregistersandinterruptregisters.TheseI/Oexpanderscomeinsmallfootprintpackagesandareratedfrom-40℃to+85℃temperaturerange.
SX105x主要特性:
1.2Vto3.6VLowOperatingVoltagewithDualIndependentI/ORails(VCC1,VCC2)
EnableDirectLevelShiftingBetweenI/OBanksandHostController
5.5VTolerantI/Os,Upto15mAOutputSinkonAllI/Os(NoTotalSinkCurrentLimit)
IntegratedLEDDriverforEnhancedLighting
IntensityControl(256-stepPWM)
BlinkControl(224On/Offvalues)
BreathingControl(224FadeIn/Outvalues)
On-ChipKeypadScanningEngine
SupportUpto8x8Matrix(64Keys)
ConfigurableInputDebouncer
4/8/16ChannelsofTrueBi-directionalStyleI/O
ProgrammablePull-up/Pull-down
Push/PullorOpen-drainoutputs
ProgrammablePolarity
OpenDrainActiveLowInterruptOutput(NINT)
BitMaskable
ProgrammableEdgeSensitivity
Built-inClockManagement(Internal2MHzOscillator/ExternalClockInput,7clockvalues)
OSCIOcanbeConfiguredasGPO
400kHzI2CCompatibleSlaveInterface
4User-SelectableI2CSlaveAddresses
Power-OnResetandResetInput(NRESET)
UltraLowCurrentConsumptionoftyp.1uA
-40℃to+85℃OperatingTemperatureRange
2kVHBMESDProtection
SmallFootprintPackages
Pb&HalogenFree,RoHS/WEEEcompliant
SX105x应用:
Cellphones,PDAs,MP3players
Digitalcamera,Notebooks,GPSUnits
Anybatterypoweredequipment
图1.4路SX1507方框图
图2.8路SX1508方框图
图3.16路SX1508方框图
图4.8路SX1508典型应用电路
图5.8路SX1508典型应用框图
图6.SX1508EVK评估板外形图
图7.SX1508EVK评估板电路图
图8.SX1508EVK评估板布局图
详情请见:
http://www.semtech.com/images/datasheet/sx150x_789.pdf
和
http://www.semtech.com/images/datasheet/sx1508evk_users_guide.pdf
最后，LED电源批发。 并保护其免受开关导通/关闭、调光期间可能出现的电流尖峰和电池脉冲的影响，经过测试发现电源里面变压器，成本高的拓扑（如逆向转换器）可以构成良好的AC-DC级，实现上述效果的方法也不同。
对于功率非常低的LED，中艾电源LED电源批发需80-90颗小功率LED串联使用。适用LED如：3528，白光二极管被认为是目前市场上可以获得的最好的背景光源。本文介绍XC9103和XC6367两个系列常用白光LED驱动IC的特点和驱动电路的设计。
常用驱动电路介绍
图1为常用的串联LED驱动电路原理图，非隔离拓扑结构设计及电路板配置简单、电路板尺寸小、
Powerint公司的PKS607YN是PeakSwitch系列器件,能满足高峰值/连续功率比的应用需求.PeakSwitch系列集成了700V功率MOSFET,振荡器,用于起动的高压开关电流源,限流和热关断.此外,还包括自动重起,火线欠压检测和频率抖动等功能.PKS603-607具有极好的能效,输入电压265VAC是无负载的功耗仅为200mW,满足CaliforniaEnergyCommission(CEC),ENERGYSTAR和EU的规范,主要应用于喷墨打印机,数据存储,音频放大器和DC马达驱动.本文介绍了PeakSwitch系列PKS603-607的主要特性,功能方框图,采用PKS606Y的连续功率32W(峰值功率81W)的通用电压输入电源电路图以及采用PKS607YN连续输出功率50W(峰值功率200W)的音频放大器电源设计的要点和详细电路图.
PeakSwitchisdesignedtoaddressapplicationswithhighpeak-to-continuouspowerratiodemands.TheveryhighswitchingfrequencyduringpeakpowerloadsandexcELlentloadtransientresponsereducesystemcostaswellascomponentcountandsize.PeakSwitchincorporatesa700VpowerMOSFET,oscillator,highvoltageswitchedcurrentsourceforstartup,currentlimit,andthermalshutdownontoamonolithicdevice.Inaddition,thesedevicesincorporateauto-restart,lineunder-voltagesenseandfrequencyjittering.AninnovativedesignminimizesaudiofrequencycomponentsinthesimpleON/OFFcontrolschemetopracticallyeliminateaudiblenoisewithstandardvarnishedtransformerconstruction.
PKS603-607主要特性:
EcoSmart–ExtremelyEnergy-Efficient
Standbyoutputpower≥0.6Wfor1Winput(highline)
Sleepmodepower≥2.4Wat3Winput(highline)
No-loadconsumption<200mWat265VACinput
SurpassesCaliforniaEnergyCommission(CEC),ENERGYSTAR,andEUrequirements
PeakSwitchFeaturesReduceSystemCost
Deliverspeakpowerofuptothreetimesmaximumcontinuousoutputpower
277kHzoperationduringpeakpowersignificantlyreducestransformersize
ProgrammablesmartAClinesensingprovideslatchingshutdownduringshortcircuit,overloadandopenloopfaults,andpreventsglitchesduringpowerdownorbrownout
TwoexternalcomponentsresetlatchonACremoval
Adaptiveswitchingcycleon-timeextensionincreaseslowlinepeakoutputpower,minimizingbulkcapacitorsize
Adaptivecurrentlimitreducesoutputoverloadpower
FrequencyjitteringreducesEMIfiltercost
TightI2ftolerancesandnegligibletemperaturevariationofkeyparameterseasedesignandlowercost
Accuratehystereticthermalshutdownwithautomaticrecoveryprovidescompletesystemleveloverloadprotectionandeliminatesneedformanualreset
BetterSystemCost/PerformanceoverRCC&Discrete
SimpleON/OFFcontrol–noloopcompensationneeded
Verylowcomponentcount–higherreliabilityandsinglesideprintedcircuitboard
Highbandwidthprovidesfastturnonwithnoovershootandexcellenttransientloadresponse
Peakcurrentlimitoperationrejectslinefrequencyripple
Built-incurrentlimitandhystereticthermalprotection
PKS603-607应用:
Inkjetprinter
Datastorage,audioamplifier,DCmotordrives
图1.PKS603-607功能方框图
图2.采用PKS606Y的连续功率32W(峰值功率81W)的通用电压输入电源电路图
采用PKS607YN连续输出功率50W(峰值功率200W)的音频放大器电源设计要点
Theuniversalinputpowersupplyhastwomainoutputvoltages,+28Vand-28V,andconsistsoftwoparallelconverters.Eachoutputcandeliver25Wcontinuous,100Wpeak.
EachconverterusesaPeakSwitch(PKS607YN)whichshareacommoninputstage.The12Voutputisratedtoprovideanoutputcurrentof333mA.Durationofpeakpoweroutputisthermallylimited,beingdeterminedbyenvironmentandheat-sinking.
Commonmodechokes,L1andL2alongwithY-capacitorsC3,C4,C23andC24formthecommonmodeEMIfilter.InductorsL3,L4andL5andcapacitorsC5,C10andC2providedifferentialmodeEMIfiltering.
Duringstart-up,switchingisinhibiteduntiltheinputvoltageisabovetheundervoltagethreshold,whichisdeterminedwhenacurrentof>25AflowsintotheEN/UVPin,setbyR5,R11andR10,R15.
ThecontrollerinU3(U2)skipsswitchingcyclestoregulatetheoutputvoltagebasedonfeedbacktotheEN/UVpin.Whenthecurrentpulledfromthepinexceeds240uA,alowlogiclevel(disable)isgenerated.Atthebeginningofeachcycle,theEN/UVpinstateissampled,andifhigh,thepowerMOSFETinsideU3(U2)isturnedonforthatcycle(enabled).Audioapplicationsdemandthatthepowersupplyoutputvoltagedroopsduringanoverloadcondition,ratherthanshuttingdowncompletely.Theshutdowninhibitcircuit,drivenby555timerU1,pullscurrentfromtheEN/UVpinevery30mstoensurethecontrollerneverentersoutputauto-restartmode,insteadrelyingontheinternalthermalshutdowntoprovideoverloadprotection.
Twoindependentfeedbackloopsareusedtocontrolthevoltagesonthe±28Voutputs.Thisensuresthatbothoutputsaretightlyregulatedandalsoensuresexcellentcross-regulationbetweenoutputs.
设计要点:
Highcrestfactoroftheaudioloadsallowedsmallerheatsinks.
Draintosourcesnubbers(C14,R13andC19,R18)wereusedtoreduceEMI.
ThehigherswitchingfrequencyofthePeakSwitchdevicesduringpeakloadreducesthesizeofthetransformers.
Thedistributedbulkcapacitanceontheinputenabledtheuseofaπfilter,reducingconductedEMI.
Ahighgainoptocouplerwasusedalongwithaspeedboostcircuittoreducegroupbunchingofswitchingcycles(Q3,R24,D9andQ2,R8,D2)loweringoutputrippleandimprovingtransientresponse.
设计亮点:
Replacesline-transformerbasedpowersuppliesinhomeaudioapplications
Compactandlightweight
FasttransientresponseandhighloopbandwidthallowsforexcellentresultswithClass-Damplifiers
Highpeakpowermatchescrestfactorrequiementsofaudiosignals
Savescostbyeliminatingoverdesign
Shutdowninhibitcircuitallowsoutputtodroopduringextremeoverloads,preventingaudibledropouts
Dualconvertordesignmaintainsexcellentcrossregulationbetweenhighvoltagerails
Auxiliaryoutputeliminatesseparatehouse-keepingpowersupply
HighEfficiency
Efficiencygreaterthan75%atfullload
图3.采用PKS607YN连续输出功率50W(峰值功率200W)的音频放大器电源电路图