图2是利用电荷泵构成LED电流控制电路，大部分都是参考开关电源和电子整流器的标准。
d现在大部分LED电源没有统一，此类产品包括E27和GUl0等灯泡型
Intersil公司的ISL97684是用于中等尺寸TFT-LCD背光的四路LED驱动器,输入电压低到4V,输出电压高达45V.还提供8位PWM调光,在时的线性度低至0.009%,或30kHz时为1.35%,主要应用在平板PC和笔记本电脑显示led背光,PMPLED背光.本文介绍了ISL97684主要特性,方框图,以及单电源,双电源应用电路和PWM调光应用电路.
TheISL97682,ISL97683,ISL97684areIntersil’shighlyintegrated2-3-4-channELsLEDdriversthataresuitableformediumsizeTFT-LCDbacklights.ThesepartscandrivemultiplechannelsofLEDsfrominputsaslowas4Vtooutputsofupto45V.Theycanalsooperatefrominputsaslowas3Vtooutputsofupto26.5Vinbootstrapconfiguration.
TheISL97682,ISL97683,ISL97684featureoptionalchannelsphaseshiftcontrol.Thisfeatureisusedtominimizetheinput,outputripplecharacteristicsandloadtransient,whichhelpeliminateorreducethevideoandaudionoiseinterferencefromthebacklightdriveroperation.
TheISL97682,ISL97683,ISL97684offer8-bitPWMdimmingforsystemsthatneedfrequencytuningflexibility.Withtheuniqueadaptiveboostswitchingarchitecture,theISL97682,ISL97683,ISL97684alsoofferDirectPWMdimmingwithoutput,whichfollowsinputandachieveslinearityaslowas0.009%at200Hzor1.35%at30kHz.
ThedriversincorporatedynamicheadroomcontrolthatmonitorsthehighestLEDforwardvoltagestringandusesitsfeedbacksignalfortheminimumoutputregulation.TheISL97682,ISL97683,ISL97684incorporatesextensivefaultprotectionfunctionsincluding
stringopenandshortcircuitdetections,OVP,andOTP.Theswitchingfrequencycanbeselectedateither600kHzor1.0MHzinPFMorPWMmode.Thesepartsareavailableinthethinandcompact16Ld3mmx3mmTQFNpackageandoperateinambienttemperaturefrom-40℃to+85℃.
ISL97684主要特性:
?ISL97682-2x100mAChannels
?ISL97683-3x50mAChannels
?ISL97684-4x50mAChannels
?InputVoltage4.0V~26.5VwithMaxVOUTof45V
?InputVoltage3.0V(seeFigure26)~24VwithMaxVOUTof26.5V
?PWMDimmingLinearity
-PWMDimmingwithAdjustableDimmingFrequencywithDutyCycleLinearfrom0.4%to100%<30kHz
-DirectPWMDimmingwithDutyCycleLinearfrom0.009%to100%at200Hz
?CurrentMatchingof0.7%typicalfrom1%~100%Dimming
?Selectable600kHzor1MHzSwitchingFrequencyinPWM/PFMMode
?DynamicHeadroomControl
?FaultProtection
-StringOpen/ShortCircuitProtections,OVP,OTP
?ThinandCompactTQFN-163mmx3mmPackage
ISL97684应用:
?TablettoNotebookPCDisplaysLEDBacklighting
?PMPLEDBacklighting
图1.ISL97684方框图
图2.ISL97684单电源3V应用电路图
图3.ISL97684双电源2.7V应用电路图
图4.ISL97684直接PWM调光应用电路图
图4.ISL97684采用RFPWM频率可调的PWM调光应用电路图
TheLTR3760isan8-channELLEDdriverwithastep-upDC/DCcontrollercapableofdrivingupto45VofLEDs.
Eachchannelcontainsanaccuratecurrentsinkwith±2%currentmatching.Channelsfollowamasterprogrammablecurrenttoallowbetween20mAto100mAofLEDcurrentperstring.ChannelscanbeparalleledforhigherLEDcurrent.OutputvoltageadaptstovariationsinLEDVFforoptimumefficiencyandopenLEDfaultsdonotaffecttheoperationofconnectedLEDstrings.
TheLT3760allowsaPWMdimmingrangeupto3000:1andananalogdimmingrangeupto25:1.Operatingfrequencycanbeprogrammedfrom100kHzupto1MHzusingasingleresistororsynchronizedtoanexternalclock.
Additionalfeaturesinclude:programmablemaximumVOUTforopenLEDprotection,afaultflagforopenLED,programmableLEDcurrentderatingvstemperature,micropowershutdownandinternalsoft-start.TheLT3760isavailableinathermallyenhanced28-pinTSSOPPackage.
LT3760主要特性:
Upto45VofLEDsx100mA,8-ChannelLEDDriver
WideInputRange:6Vto40V
±2%LEDCurrentMatchingat40mA(Typ±0.7%)
Upto3000:1TrueColorPWM™DimmingRange
SingleResistorSetsLEDCurrent(20mAto100mA)
LEDCurrentRegulatedEvenforPVIN>VOUT
OutputAdaptstoLEDVFforOptimumEfficiency
FaultFlag+ProtectionforOpenLEDStrings
ProtectionforLEDPintoVOUTShort
ParallelChannelsforHigherLEDCurrent
ProgrammableLEDCurrentDeratingvsTemperature
AccurateUndervoltageLockoutThresholdwithProgrammableHysteresis
ProgrammableFrequency(100kHzto1MHz)
SynchronizabletoanExternalClock
LT3760应用:
Automotive,NotebookandTVMonitorBacklight
图1.LT3760方框图
图2.效率92%36W背光LED驱动器
图3.效率92%36WLED驱动器:1MHz升压,8串LED,每串100mA
图4.效率92%28WLED驱动器:750kHz升压,8串LED,每串80mA
图5.15WLED驱动器:750kHz升压,8串LED,每串55mA
图6.29WLED驱动器:400kHz升压,2串LED,每串350mA
图7.25WLED驱动器:400kHz升压,3串LED,每串200mA
图8.28WLED驱动器:700kHz升压,4串LED,每串160mA
图9.14WLED驱动器:700kHz升压,4串LED,每串80mA
图10.28WLED驱动器:1MHzSPEIC,8串LED,每串100mA
，能够工作在高达2MHz的开关频率，中艾电源LED驱动电源厂家Linear公司的LT3798是绝缘无光耦带PFC的反激控制器,功率因素大于0.97,不需要光耦合器,谐波低,恒流和恒压调整,精度在±5%,无负载的功耗小于0.5W,和能源之星标准兼容,主要用在离线5W-100W电源,高DCVIN绝缘应用和离线总线转换器(12V,24V或48V输出).本文介绍了LT3798主要特性,框图以及通用输入24W和48WPFC电源电路图.
IsolatedNoOpto-CouplerFlybackControllerwithActivePFC
TheLT®3798isaconstantvoltage/constantcurrentisolatedflybackcontrollerthatcombinesactivepowerfactorcorrection(PFC)withnoopto-couplerrequiredforoutputvoltagefeedbackintoasingle-stageconverter.ALT3798baseddesigncanachieveapowerfactorofgreaterthan0.97byactivELymodulatingtheinputcurrent,allowingcompliancewithmostHarmonicCurrentEmissionrequirements.
TheLT3798iswellsuitedforawidevarietyofoff-lineapplications.TheinputrangecanbescaLEDupordown,dependingmainlyonthechoiceofexternalcomponents.
Efficiencieshigherthan86%canbeachievedwithoutputpowerlevelsupto100watts.Inaddition,theLT3798caneasilybedesignedintohighDCinputapplications.
LT3798主要特性:
IsolatedPFCFlybackwithMinimumNumberofExternalComponents
VINandVOUTLimitedOnlybyExternalComponents
ActivePowerFactorCorrection
LowHarmonicDistortion
NoOpto-CouplerRequired
Constant-CurrentandConstant-VoltageRegulation
AccurateRegulatedVoltageandCurrent(±5%Typical)
EnergyStarCompliant(<0.5WNoLoadOperation)
ThermallyEnhanced16-leadMSOPPackage
LT3798应用:
Offline5Wto100W+Applications
HighDCVINIsolatedApplications
OfflineBusConverter(12V,24Vor48VOutputs)
图1.LT3798方框图
图2.LT3798通用输入24WPFC总线电源电路图
图3.LT3798通用输入48WPFC电源电路图
，从而引起亮度的较大变化。所以,采用恒压源驱动不能保证LED亮度的一致性，
ADI公司的ADP1650是集成了I2C兼容接口的1.5Aled闪光驱动器.器件集成了1.5MHz或3.0MHz同步电感升压转换器,I2C兼容接口和1500mA电流源.火炬模式电流高达200mA,效率大于90%(峰值),主要用在照相手机和智能手机以及数码相机,摄像机和PDA.本文介绍了ADP1650主要特性,应用电路以及ADP1650评估板套件主要特性,详细电路图和材料清单.
1.5ALEDFlashDriverwithI2C-CompatibleInterface
TheADP1650isaverycompact,highlyefficient,singlewhiteLEDflashdriverforhighresolutioncameraphonesthatimprovespictureandvideoqualityinlowlightenvironments.Thedeviceintegratesaprogrammable1.5MHzor3.0MHzsynchronousinductiveboostconverter,anI2C-compatibleinterface,anda1500mAcurrentsource.Thehighswitchingfrequencyenablestheuseofatiny,1mmhigh,lowcost,1μHpowerinductor,andthecurrentsourcepermitsLEDcathodegroundingforthermallyenhanced,lowEMI,andcompactlayouts.
TheLEDdrivermaximizesefficiencyovertheentirebatteryvoltagerangetomaximizetheinput-power-to-LED-powerconversionandminimizebatterycurrentdrawduringflashevents.AprogrammabledcbatterycurrentlimitsafELymaximizesLEDcurrentforallLEDVFandbatteryvoltageconditions.
TwoindependentTxMASKinputspermittheflashLEDcurrentandbatterycurrenttoreducequicklyduringapoweramplifiercurrentburst.TheI2C-compatibleinterfaceenablesthepro-grammabilityoftimers,currents,andstatusbitreadbackforoperationmonitoringandsafetycontrol.
TheADP1650comesinacompact12-ball,0.5mmpitchpackageandoperateswithinspecificationoverthefull?40℃to+125℃junctiontemperaturerange.
ADP1650主要特性:
Ultracompactsolution
Small,2mm×1.5mm,12-ballWLCSPpackage
Smallestfootprint,1mmheight,1μHpowerinductor
LEDcurrentsourceforlocalLEDgrounding
Simplifiedroutingto/fromLED
ImprovedLEDthermals
Synchronous3MHzPWMboostconverter,noexternaldiode
Highefficiency:90%peak
Reduceshighlevelsofinputbatterycurrentduringflash
Limitsbatterycurrentdrainintorchmode
I2Cprogrammable
Currentsupto1500mAinflashmodeforoneLEDwith7%accuracyoverallconditions
Currentsupto200mAintorchmode
Programmabledcbatterycurrentlimit(4settings)
Programmableflashtimerupto1600ms
LowVBATmodetoreduceLEDcurrentautomatically
4-bitADCforLEDVF,die/LEDtemperaturereadback
Control
I2C-compatiblecontrolregisters
ExternalSTROBEandtorchinputpins
2transmittermask(TxMASK)inputs
Safety
Thermaloverloadprotection
Inductorfaultdetection
LEDshort-/open-circuitprotection
ADP1650应用:
Camera-enabledcellularphonesandsmartphones
Digitalstillcameras,camcorders,andPDAs
图1.ADP1650功能方框图
ADP1650评估板
Theevaluationsystemiscomposedofamotherboard,daughter-boardandLEDsub-board.ThemotherboardprovidestheI2CsignalsfromthePCUSBportandgeneratestheI/Ovoltagesanddigitalhighandlowsignalsforthedaughterboard.Forover-temperaturemeasurement,thedaughterboardcaneitherbepluggeddirectlyintothemotherboardorconnectedtothemotherboardviaaribboncable.
Themotherboardfeaturesa3.3Vregulatorand2.8V/1.8VregulatorsforVDDIO.ThedaughterboardcontainsjumpersandtestpointsforeasyevaluationoftheflashdriverIC.
TheADP1650-EVALZkitincludes:
Cables:power(red/black),USB,2×currentmeasurements
Samples:fiveADP1650devices,twoFDSD3012inductors
LEDboards:OSRAMLUWF65N,LumiLEDsPWF-4
图2.ADP1650评估板外形图
图3.ADP1650评估板主板电路图
图4.ADP1650评估板子板电路图
图5.ADP1650LED插板电路图
图6.ADP1650-EVALZ电路图
评估板材料清单(BOM):
详情请见:
http://www.analog.com/static/imported-files/data_sheets/ADP1650.pdf
输出滤波器C10，同样