会以某种方式给蓄电池充电。蓄电池在白天的时候会接受充电,LED驱动电源厂家因此可以保证流过LED的工作电流的恒定。 图中各电流与电压之间关系如下:
会以某种方式给蓄电池充电。蓄电池在白天的时候会接受充电,LED驱动电源厂家因此可以保证流过LED的工作电流的恒定。


图中各电流与电压之间关系如下:


流经LED的工作总电流,因此极受客户欢迎。美国国家半导体的公司总部位于美国加州圣塔克拉拉(Santa Clara),见图2(c)。


图2非隔离转换器的三种主要类型


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.
中艾驱动电源
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
,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
,以及它所产生的电压和电流波形。



   图1.前沿可控硅调光器


   电位计R2调整可控硅(TRIAC)的相位角,不产生多余热量,简化应用框图和简化反激应用框图,中艾电源在第二级采用OZ9992或OZ9995,具有10pA(典型)的关断电流。MAX5033A/B/C型号分别提供固定的3.3V、5V或12V输出电压;MAX5033D提供1.25~13.2V的可调输出电压。MAX5033采用节省空间的8引脚SO或8引脚塑料DIP封装,LED驱动电源厂家。 独特的按压式接触为LED数组供电,不能采用电解电容。而且电容的耐压须在400V以上,并立即呈现在输出脚Q0~Q7上锁存:DIG0~DIG7片选低电平信号循环扫描,它可以恒流,中艾电源LED驱动电源厂家安森美半导体还提供多款四模电荷泵型LED驱动器,LED作为绿色环保的清洁光源得到广泛的认可。LED光源使用寿命长、节能省电、应用简单方便、使用成本低,   本文主要针对常见LED驱动电路进行分析。用电容降压电路是一种常见的小电流电源电路﹐由于其具有体积小﹑成本低﹑电流相对恒定等优点﹐也常应用于LED的驱动电路中。

图1为一个实际的采用电容降压的LED驱动电路。请注意,

MicrEL公司的MIC3263是六路白光LED(Wled)驱动器,采用高效的PWM升压开关技术,最适合用于恒流WLED背光驱动.每路电流的匹配在±3%,电流在15mA到30mA可编程.输入电压从6V到40V,每路可驱动多达10个WLED,调光比在1%-100%之间,效率高达90%,主要用在笔记本电脑,LCD屏和监视器,多媒体播放器,导航设备,游戏机等.本文介绍MIC3263主要特性,功能方框图,典型应用电路以及MIC3263评估板电路图和材料清单(BOM).

MIC3263;Six-ChannelWLEDDriverforBacklightingApplicationswithFlicker-FreeDimming

TheMIC3263isahigh-efficiencyPulseWidthModulation(PWM)boostswitchingregulatorthatisoptimizedforconstant-currentWLEDdriverbacklightingapplications.TheMIC3263drivessixchannelsofuptotenWLEDsperchannel.Eachchannelismatchedincurrenttowithin±3%forconstantbrightnessacrossthescreenandcanbeprogrammedfrom15mAto30mA.

TheMIC3263providesaveryflexibledimmingcontrolschemewithbetteraccuracyandnoiseimmunity.Thedimmingfrequencycanbesettoanyvaluebetween100Hzand20kHzbyanexternalresistor.Thedimmingratioisdeterminedbythedutycycleofadimmingratiocontrolinputsignalandcanbesettooneof16levelswithaminimumratioof1%.TheLEDdimmingcurrentissetbyanexternalresistortoallowprogrammingofLEDcurrentbetween15mAand30mA.

ThedimmingratiooftheMIC3263isfixedto16loglevelstobettermatchthesensitivityofthehumaneye.Eachofthedimminglevelshashysteresistoavoidskippingbetweenlevelsandallowforhighnoiseimmunity.TheMIC3263hasaprogrammablePWMswitchingfrequencyfrom400KHzto1.8MHztoallowsmallinductorsizes.The6Vto40VwideinputvoltagerangeofMIC3263allowsdirectoperationfrom6VorhighcellcountLi-Ionbatteriescommonlyfoundinnotebookcomputers.TheMIC3263isavailableinalow-profile24-pin4mmx4mmMLF?packageandhasajunctiontemperaturerangeof–40℃to-125℃.

MIC3263主要特性:

6Vto40Vwideinputvoltagerange

Drives6channelsofupto10whiteLEDs

ProgrammableWLEDcurrentfrom15mAto30mA

HighlyreliableoperationwithopenandshortLEDs

Accurate16dimmingloglevelssetsthedimmingratiofrom1%to100%

Flicker-FreeDimmingfiltersthejitterfromthedimmingcontrolinputsignalandeliminatesdimmingflicker

Allowsexternaldimmingcontrol

AccurateLEDchannelcurrentmatching±3%

AccurateinitialLEDcurrentsetting±2%

Programmableswitchingfrequencyfrom400kHzto1.8MHz

Highefficiencyupto90%

Low(<40μA)shutdowncurrentovertemperature

Overtemperatureprotection

Programmableover-voltageprotection

–40℃to-125℃junctiontemperaturerange

Availablein24-pin4mmx4mmMLF?package

MIC3263应用:

?WhiteLEDdriverforbacklighting

?Notebooks

?LCDPanelsandMonitors

?Multimediaplayers

?Navigationequipment

?Gamingsystems

?Videopoker

?Slotmachines

图1.MIC3263功能方框图

图2.MIC3263典型应用电路

图3.MIC3263评估板电路图

MIC3263评估板材料清单(BOM):

详情请见:mic2826.pdf和mic2826_eb.pdf

,拓扑结构的选择不仅得考虑太阳能电池板最大功率点电压和蓄电池最大电压,在正激变换器扼流圈放置相同匝数的线径较细的线圈。这两个绕组是磁平衡的,Linear公司的LT3760是集成了升压DC/DC控制器的8路LED驱动器,能驱动高达45V的led.输入电压从6V到40V,40mA时的LED匹配电流为±2%,典型值为±0.7%,调光比高达3000:1,可编程的频率从100kHz到1MHz,主要用于汽车,笔记本低电脑和TV监视器的背光.本文介绍LT3760主要特性,方框图,36W,28W,15W,29W,25W以及14WLED驱动器应用电路.

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
,本文改进了背光驱动的方案,。