基于MAX17127设计的高效白光LED驱动技术

基于MAX17127设计的高效白光LED驱动技术MAX17127是Maxim公司的高效白光LED(WLED)驱动器,它的内部开关电流模式升压转换器能驱动LED阵列,多达并联6串LED,每串13个LED.每串电流匹配达到±2%,输入电压5V-26V,可调电流从10mA到30mA.可调开关频率从250kHz到1MHz.主要用在汽车电子系统,手持终端以及笔杆子电脑和便携式计算机显示器.本文介绍了MAX17127主要特性,功能方框图,以及典型应用电路.

TheMAX17127isahigh-efficiencydriverforwhitelight-emittingdiodes(LEDs).Itisdesignedforlargeliquid-crystaldisplays(LCDs)thatemployanarrayofLEDsasthelightsource.Aninternalswitchcurrent-modestep-upconverterdrivestheLEDarray,whichcanbeconfiguredforuptosixstringsinparalleland13LEDsperstring.Eachstringisterminatedwithballastthatachieves±2%current-regulationaccuracy,ensuringevenLEDbrightness.TheMAX17127hasawideinput-voltagerangefrom5Vto26V,andprovidesanadjustable10mAto30mAfull-scaleLEDcurrent.

TheMAX17127canimplementbrightnesscontrolthroughthePWMsignalinput,andLEDcurrentisdirectlycontrolledbytheexternaldimmingsignal’sfrequencyanddutycycle.

TheMAX17127hasmultiplefeaturestoprotectthecontrollerfromfaultconditions.Onceanopen/shortstringisdetected,thefaultstringisdisabledwhileotherstringscanstilloperatenormally.Thecontrollerfeaturescycle-by-cyclecurrentlimittoprovideconstantoperationandsoft-startcapability.IftheMAX17127isincurrent-limitcondition,thestep-upconverterislatchedoffafteraninternaltimerexpires.Athermal-shutdowncircuitprovidesanotherlevelofprotection.Whenthermalshutdownhappens,theMAX17127islatchedoff.

TheMAX17127’sstep-upcontrollerfeaturesaninternal0.12Ω(typ),48V(max)powerMOSFETwithlocalcurrent-senseamplifierforaccuratecycle-by-cyclecurrentlimit.ThisarchitecturegreatlysimplifiestheexternalcircuitryandsavesPCBspace.Low-feedbackvoltageateachLEDstringhelpsreducepowerlossandimproveefficiency.TheMAX17127featuresresistor-adjustableswitchingfrequencyfrom250kHzto1MHz,whichenablesawidevarietyofapplicationsthatcantradeoffcomponentsizeforoperatingfrequency.

TheMAX17127isavailableinathermallyenhanced,lead-free,20-pin,4mmx4mmthinQFNpackage.

MAX17127主要特性:

5Vto26VInputSupplyVoltage

UptoSixParallelStringsMultipleSeries-ConnectedLEDs

250kHzto1MHzAdjustableSwitchingFrequency

0.12ΩInternalHVPowerMOSFET(48Vmax)

LowStringFeedbackVoltage:480mVat20mALEDCurrent

Full-ScaleLEDCurrentAdjustablefrom10mAto30mA

±2%Current-RegulationAccuracyBetweenStrings

400nsMinimumStringOn-Time

100Hzto25kHzPWMInputRange

OpenandShortLEDProtection

OutputOvervoltageProtection

ThermalShutdown

Small20-Pin,4mmx4mmThinQFNPackage

MAX17127应用:

Automotive