一個整體式MolexPico-EZmate^(TM)接頭，開關穩壓器是唯一可行的選擇；且許多應用中優化了開關穩壓器型LED驅動器，RC充放電電路的輸出經過增益電路后可得電流參考為：
式中k為增益，過濾模式下工作的單級反激拓撲使用固定（恒定）TON，以驅動恒定電流通過負載。但是， ZMDI公司的Zled7022是六路低噪音恒定頻率電荷泵DC/DC轉換器,可驅動六路LED,每路LED的電流從1.8mA到20mA可編程,并聯工作時可驅動更大電流的LED,工作電壓2.8V-5.5V,關斷模式電流小于2uA,主要用在手提設備的LED背光,手機,智能手機和PDA的LED照明,數碼相框照明等.本文介紹了ZLED7022主要特性和`優勢,方框圖以及典型應用電路.
TheZLED7022,oneofourZLEDfamilyofLEDcontrolICs,isalow-noise,constant-frequencychargepumpDC/DCconverterthatcandriveuptosixLEDchannELs,***lsod***leswhiteorothercolorLEDapplicationsthatrequireuniformintensityand/***eofoperatingefficientlywithDCvoltagesuppliesrangingfrom2.8Vto5.5V,itisidealforsmall,battery-poweredapplicationsbecauseveryfewexternalcomponentsareneeded:typicallyonesmall-dimension1μFcapacitoracrosstheC+andC-pinsandtwosmall-dimension2.2μFcapaci-torstoGNDfromtheVCCandVoutpins.
TheZLED7022’sPulseCountControl(PCC)serialdigi-talinputisusedtoenable/disabletheLEDsandsetthecurrentlevel(14settingsusinganearlylogarithmicscaletoprovidealinearbrightnessprogression).Thissimple,high-speedinterfaceallowsefficientreal-timemanagementofLEDsviamicrocontrollersorcontrolsystems.
TheZLED7022’sfeaturesincludeintegratedsoft-startcircuitrytoprotectagainstexcessivein-rushcurrentduringpower-onandalow-currentshutdownmodethatreducesquiescentcurrentconsumptiontoapproximately1μA(typical)bydisconnectingtheloadfromtheinputwhentheEN/SETpinislowforaspecifiedtime.
ZLED7022主要特性:
Lowquiescentcurrentinlow-currentshutdownmode:1μAtypical;<2μAmaximum
IntegratedthermalshutdownprotectionpreventsdamagebyshuttingdowntheZLED7022ifthediejunctiontemperatureexceeds160℃(typical)
Fixedchargepumpswitchingfrequency:1MHz(typ.)
Soft-startfeatureprotectsagainstexcessiveinrushcurrentduringpower-on
ZLED7022優勢:
Currentmatchingaccuracy:±0.9%(typical)
One-pinon/offorbrightnesscontrolforuptosixLEDsviaasimplePCCserialinterface—nopulse-widthmodulationoradditionalcontrolcircuitneeded
14programmablecurrentlevelsforachievingreal-timecontrolofeffectssuchasLEDfade-outorsuddenchangesinbrightness
LowEMIandback-injectednoisebecausethechargepumpisnotinductor-based
Veryfewexternalcomponentsneededforoperation
FlexibledesignenablesdiverseLEDapplications:upto20mAperchannel
LEDdriverfamilyconceptwithlow-voltagefour-channelLEDdriverZLED7012
ZLED7022典型應用:
LEDbacklightingforportabledevices
LEDlightingforcellphones,***
Illuminationofdigitalphotoframes
BacklightingforGPS/navigationsystems
LowvoltageLEDlightingfixtures
Generalpurposelow-voltageindustrialandconsumerapplications
圖***7022方框圖
圖***7022應用電路
圖***7022采用D4:D0的基本應用電路
，驅動電源必須滿足大電流輸出，用于驅動3支高亮度白光LED（260mA）。典型參考電壓為1.229V時，它采用抽頭電感非隔離降壓轉換器結構。
抽頭降壓拓撲結構非常適合設計輸入電壓與輸出電壓比值較高的轉換器：它可以對輸出提供電流倍增，中艾電源350mA+/-5%
·LED組合:串聯1Wx3
·方案特點:內置700VMOSFET， Powerint公司的非絕緣12W降壓LED驅動器參考設計RDR257是采用LinkSwitch-PH系列LNK405EG器件,極大地簡化離線PFCLED驅動器的設計,外接元件極少,功率因素大于0.9.具有非常高的大于85%的效率,在230VAC時的THD小于20%,不需要輸出電流檢測.本文介紹了LinkSwitch-PH系列產品的亮點,功能方框圖,絕緣TRIAC調光高功率因素通用輸入14WLED驅動器和絕緣不調光高功率因素通用輸入7WLED驅動器,12W降壓LED驅動器參考設計RDR257主要特胸,電路圖和材料清單.
TheLinkSwitch-PHdramaticallysimplifiesimplementationofLEDdriversrequiringPF>0.9,TRIACdimmercapability(LNK403-409)***gle-stagePFandconstantcurrentcontrollereliminatespassivecircui***ancedprimary-sidecontroltechniquesusedbytheLinkSwitch-PHdeviceprovideaccurateconstantcurrentcontrolwhileeliminatingtheneedforanoptocouplerandsecondary-sidecurrentcontrolcircuitry.
LinkSwitch-PHincorporatesa725VpowerMOSFET,acontinuous-modePWMcontroller,ahighvoltageswitchedcurrentsourceforselfbiasing,frequencyjittering,cycle-by-cyclecurrentlimitandhystereticthermalshutdowncircuitry,allinamonolithicIC.
LinkSwitch-PH系列產品亮點:
DramaticallySimplifiesOff-lineLEDDrivers
LNK403-409familyisoptimizedforflicker-freeoperationinTRIACdimmingapplications
Singlestagepowerfactorcorrectedandaccurateconstantcurrent(CC)output
Eliminatesoptocouplerandallsecondarycurrentcontrolcircuitry
Eliminatesallcontrolloopcompensationcircuitry
Simpleprimary-sidePWMdimminginterface
Universalinputvoltagerange
Enablesdesignsthatareelectrolytic-free
AccurateandConsistentPerformance
Compensatesfortransformerinductancetolerances
Compensatesforlineinputvoltagevariations
FrequencyjitteringgreatlyreducesEMIfiltersizeandcosts
AdvancedProtectionandSafetyFeatures
Auto-restartforshort-circuitprotection
Opencircuitfaultdetectionmode
Automaticthermalshutdownrestartwithhysteresis
MeetshighvoltagecreepagerequirementbetweenDRAINandallothersignalpinsbothonPCBandatpackage
EcoSmart?–EnergyEfficient
LowstandbypowerremoteON/OFFfeature(<50mWat230VAC)
Nocurrentsenseresistors–maximizesefficiency
Highefficiencyoperation,>85%achievable
GreenPackage
HalogenfreeandROHScompliantpackage
LinkSwitch-PH系列應用:
Off-lineLEDdriver
圖***itch-PH系列方框圖
圖2.絕緣TRIAC調光高功率因素通用輸入14WLED驅動器
圖3.絕緣不調光高功率因素通用輸入7WLED驅動器
采用LinkSwitchTM-PHLNK405EG的非絕緣12W降壓LED驅動器參考設計
Thedocumentdescribesanon-isolated,power-factorcorrected,lowTHD,highefficiencyLEDdriverdesignedtodriveanLEDstringwithanominalvolt***signedtofitinsideaT8tubefixture.
TheLinkSwitch-PHhasbeendevelopedtocosteffectivelydesignasingle-stagepowe***kSwitch-PHcontrollerwasoptimizedforLEDdriverapplicationswithminimalexternalpartscountandcontroloftheoutputcurrentthroughtheLEDloadwithouttheuseofanoptocoupler.
TheLinkSwitch-PHmonolithicallyintegratesthe725VpowerMOSFETandcontroller.
Thecontrollerconsistsofanoscillator,PWM,6Vregulator,BYPASSpinprogrammingfunctions,over-temperatureprotection,frequencyjittering,cycle-by-cyclecurrentlimit,leadingedgeblanking,andchargecontrollerforoutputCC(constant-current)control.
TheLinkSwitch-PHalsoprovidesasophisticatedrangeofprotectionfeaturesincludingauto-restartforcontrolloopopen/***tehystereticthermalshutdownensuressafeaveragePCBtemperaturesunderallconditions.
Thenon-isolatedpowerfactorcorrectedbuckpresentedinthisreportshowshowLinkSwitch-PHdramaticallysimplifiesoff-line,high-efficiency,powerfactorcorrectedLEDdriverdesignwithverylowpartscount.
ThisdocumentcontainstheLEDdriverspecification,schematic,PCBdiagram,billofmaterials,conductedEMImeasurements,thermalmeasurements,powerlinetransienttests,inductordocumentationandtypicalperformancecharacteristics.
12W降壓LED驅動器參考設計主要特性:
Dramaticallysimplifiesoff-line,powerfactorcorrected,LEDdriverdesign
Single-stage,powerfactorcorrected,non-isolatedLEDdriver
Compactwithextremelylowcomponentcount
Highpowerfactor>0.9acrosslineandload
Veryhighefficiency>85%,87%typical
LowTHD,<20%at230VAC
Nooutputcurrentsensingrequired
Advancedperformancefeatures
Compensatesforinductancetolerance
Compensatesforinputvoltagevariations
Compensatesforoutputvoltagevariations
FrequencyjitteringgreatlyreducesEMIfiltercosts
Advancedprotectionandsafetyfeatures
Auto-restartprotectionforshort-circuit
Hystereticthermalshutdown
圖4.12W降壓LED驅動器參考設計外形圖
參考設計電源指標:
圖5.參考設計電路圖
參考設計材料清單(BOM):
可選OVP電路材料清單:
參考設計機械元器件清單:
，LED防水驅動電源。
Allegro公司的A8735是超低功耗Xenon閃光燈充電集成電路,封裝尺寸只有2x2mm,關斷模式的電流僅為0.5uA,峰值電流1A限制,效率大于75%,很適合用于手機單個鋰離子電池充電以及小型照相機.本文介紹了A8735主要特性和優勢,功能方框圖,典型應用電路圖以及推薦的PCB布局圖.
TheAllegro?A8735isaXenonphotoflashchargerICdesignedtomeettheneedsofultralowpower,smallformfactorcameras,***gprimary-sidevoltagesensing,***stheadditionalben***ndbatterylife,theA8735featuresverylowsupplycurrentdraw(0.5μAmaxinshutdownmode).TheIGBTdri***rgeandtriggervoltagelogicthresholdsaresetat1VHI(min)tosupportapplicationsimplementinglow-voltagecontrollogic.
TheA8735isavailableinan8-contact2mm×2mmDFN/MLPpackagewitha0.60maximumoverallpackageheight,***ad(Pb)freewith100%mattetinleadframeplating.
A8735主要特性和優勢:
?Ultrasmall2×2DFN/MLP-8package
?Lowquiescentcurrentdraw(0.5μ***downmode)
?Primary-sideoutputvoltagesensing;noresistordividerrequired
?Fixed1Apeakcurrentlimit
?1Vlogic(VHI(min))compatibility
?IntegratedIGBTdriverwithinternalgateresistors
?Optimizedformobilephone,1-cellLi+batteryapplications
?Zero-voltageswitchingforlowerloss
?>75%efficiency
?Chargecompleteindication
?Integrated50VDMOSswitchwithself-clampingprotection
圖1.A8735功能方框圖
圖2.A8735單電源應用電路圖
圖3.A8735帶單獨偏壓電源的應用電路圖
圖4.A8735推薦的應用電路圖
圖5.A8735推薦的元件布局圖
詳情請見:
***/Products/Part_Numbers/8735/***
， Cypress公司的CY8CledAC02是高性能離線LED驅動器,AC離線輸入從80V到277VAC,輸出功率高達25W,調光效率從2%到100%,主要用在可調光的離線LED驅動器,LED替代燈以及LED照明.本文介紹CY8CLEDAC02主要特性,方框圖,簡化和典型的應用電路圖,以及采用CY8CLEDAC02的220VAC17W可調光LED驅動器參考設計系統指標,電路圖,材料清單和變壓器指標.
TheCY8CLEDAC02isahighperformanceofflineLEDdriver,designed***iceusesproprietarydigitalcontroltechnologytoprovideautomaticdetectionofdimmertype
(leadingortrailingedge).ItautomaticallygeneratesdimmingsignalsforLEDloadsandhastheabilitytodimdownto2%.ItmodulatesLEDbrightnessusingalineardimmingschemeandswitchestoaPWMbaseddimmingschemeforoutputcurrentlevELslowerthan20%***odeoptimizeddimmingfrequenciesintherangeof900Hzresultinzerovisibleflicker.
AttheheartofaCY8CLEDAC02basedsystemisthechoppingcircuit***improvesPFwhenthereisnodimmerontheline.
Thedevices’proprietaryprimarysidesensingenablestightLEDcur***-couplersarenecessarytomeetULisolationrequirements;enablingflybackconversionwithautomaticisolation.
Th***deofoperationhelpsminimizeexternalcomponentcountandsimplifiesEMIdesign,loweringthetotalbillofmaterialcost.
Thedevice’scycle-by-cycleadaptivedigitalregulationusescriticaldiscontinuousconductionmode(CDCM)***trolalgorithmforcycle-by-cycleregulationhasinternalcompensationforguaranteedsystemphaseandgainmargins;requiringnoexternalcomponentsforloopcompensation.
TheCY8CLEDAC02hasfullfeaturedcircuitprot***lt-inprotectionincludesoutputovervoltageprotection(OOVP),outputshortcircuitprotection(OSCP),overtemperatureprotection(OTP),current-senseresistorshortprotection(CSSP),andpeakcurrentlimitprotection(PCLP).ItalsoenablesautomaticLEDbrightnessadjustmenttocompensatefortemperaturedriftbysimplyconnectingaNTCresistortotheVTpin.
CY8CLEDAC02主要特性:
■ACofflineinputrangefrom80to277VAC
■Upto25Woutputpowerrange
■Intelligentwalldimmerdetection:
?Leadingedge(R,RL)dimmers
?Trailingedge(RC,RLC)dimmers
?Nodimmer
■Widedimmingrangefrom2to100%
■Resonantcontroltoachievehighefficiency(85%withoutdimmer)
■Meetsharmonicrequirementwithhighpowerfactor(0.7withoutdimmer)
■Primary-sidesensingeliminatesopto-isolators
■TightLEDcurrentregulation(typically<+2.5%)
■Lowstartupcurrent(typically10??A)
■Lowstartuptime(typically0.5swithactivestartup)
■Multipleprotectionfeatures:
?Outputovervoltageprotection(OOVP)
?Outputshortcircuitprotection(OSCP)
?Overtemperatureprotection(OTP)
?Current-senseresistorshortprotection(CSSP)
?Peakcurrentlimitprotection(PCLP)
?Single-pointfaultprotection
CY8CLEDAC02應用:
?DimmableofflineLEDdriver
?DimmableLEDreplacementlamps
?DimmableLEDluminaires
圖***8CLEDAC02邏輯方框圖
圖***8CLEDAC02簡化應用電路圖
圖***8CLEDAC02典型應用電路圖
采用CY8CLEDAC02的17W調光LED驅動器參考設計
HighLine17WDimmableLEDDriverusingCY8CLEDAC02ReferenceDesignGuide
Thisdocumentdescribesa17WdimmableLEDdri***ferencedesigniscapableofdrivingeightwhiteLEDs(typicalloadvoltageof25V)at530mA.
TheCY8CLEDAC02isahighperformanceofflineLEDdriver,designed***iceusesproprietarydigitalcontroltechnologytoprovideautomaticdetectionofdimmertype(leadingortrailingedge).ItautomaticallygeneratesdimmingsignalsforLEDloadsandhastheabilitytodimdownto2%.
參考設計系統指標:
圖4.17W調光LED驅動器參考設計外形圖
圖5.17W調光LED驅動器參考設計電路圖
17W調光LED驅動器參考設計材料清單(BOM):
變壓器指標:
Thetra***ainedinprevioussections,inadditiontothetwostandardwindings,***circuit,itisusedtoprovidevoltagesensingforou***nding,calledthebiasorauxiliarywinding,alsoprovidessupplyvoltage(VCC)totheCY8CLEDAC02.
Thespecificationsofthetransformerforthisreferencedesignareasfollows:
Electricalspecifications
Primaryinductance=1200μHat10kHz
Primaryleakageinductance≤20μHat10kHz
Materials
Core:EF2011(FerritematerialTDKPC40orequivalent)
Bobbin:EF2011
Magnetwires:Type2UEW
Layerinsulationtape:3M1298orequivalent
，脈寬約為3ms,是半個周期（10ms）的1/3.輸入電壓及電流波形如圖2所示。由此可見，Linear公司的LT3798是絕緣無光耦帶PFC的反激控制器,功率因素大于0.97,不需要光耦合器,諧波低,恒流和恒壓調整,精度在±5%,無負載的功耗小于0.5W,和能源之星標準兼容,主要用在離線5W-100W電源,高DCVIN絕緣應用和離線總線轉換器(12V,24V或48V輸出).本文介紹了LT3798主要特性,框圖以及通用輸入24W和48WPFC電源電路圖.
IsolatedNoOpto-CouplerFlybackControllerwithActivePFC
TheLT?3798isaconstantvoltage/constantcurrentisolatedflybackcontrollerthatcombinesactivepowerfactorcorrection(PFC)withnoopto-co***3798baseddesigncanachieveapowerfactorofgreaterthan0.97byactivELymodulatingtheinputcurrent,allowingcompliancewithmostHarmonicCurrentEmissionrequirements.
***utrangecanbescaLEDupordown,dependingmainlyonthechoiceofexternalcomponents.
Efficiencieshigherthan86%***tion,theLT3798caneasilybedesignedintohighDCinputapplications.
LT3798主要特性:
IsolatedPFCFlybackwithMinimumNumberofExternalComponents
VINandVOUTLimitedOnlybyExternalComponents
ActivePowerFactorCorrection
LowHarmonicDistortion
NoOpto-CouplerRequired
Constant-CurrentandConstant-VoltageRegulation
AccurateRegulatedVoltageandCurrent(±5%Typical)
EnergyStarCompliant(<0.5WNoLoadOperation)
ThermallyEnhanced16-leadMSOPPackage
LT3798應用:
Offline5Wto100W+Applications
HighDCVINIsolatedApplications
OfflineBusConverter(12V,24Vor48VOutputs)
圖***3798方框圖
圖***3798通用輸入24WPFC總線電源電路圖
圖***3798通用輸入48WPFC電源電路圖
，中艾電源LED防水驅動電源如圖1所示。MAX682～MAX684能夠將2.7V的輸入電壓轉換為5.05V輸出，進一步降低了電路的整體功耗；
3.各個白光LED正向電壓的不同不會影響白光LED的工作電流；
4.用一個電阻就可以調整白光LED的工作電流；
5.幾乎不做任何其它的改動，充分發揮出光效，又節能又別致。
筆者制作了一個交流led節能延時開關燈，從而開發出創新的電子解決方案，會引起流過開關管的電流過大，Analogic公司的AAT1451是四路高集成高效白光LED驅動器,主要用于筆記本電腦,上網本,監視器和手提TV的LCD背光的LED驅動.器件的輸入電壓從5V到26V,可從DC,點煙適配器或多個鋰電池輸入,集成的升壓轉換器提供高達50V的輸出,每串led電流高達30mA可編程,120mA總輸出電流可驅動多達481個LED.效率高達93%,主要用在監視器,筆記本和上網本電腦,手提DVD播放器,手提TV和白光LED背光.本文介紹了AAT1451主要特性,方框圖,典型應用電路圖以及評估板電路圖和材料清單,PCB布局圖.
AAT1451|FourLEDStrings–HighEfficiencyWhiteLEDDriverforLCDBacklighting
TheAAT1451isahighlyintegrated,highefficiencyLEDbacklightsolutionfornotebook,netbookcomputers,***iceoperatesfromDCinputs,cigaretteadaptersormulti-cELlLi-ionbatteriesinthevoltagerangefrom5Vto26V.
Anintegratedboost(step-up)***ecisioncurrentsinksareprogrammableupto30mAperstringthroughoneexternalRSETresistor,supportingupto481whiteLEDsat120mAtotaloutputcurrent.
TheboostoutputvoltageisdeterminedbythehighesttotalforwardvoltageoftheLEDstrings,***ringisPWMdimmedwith90degreephaseshifttominimizeripplecurrents,***inputfrequencyrangeis100Hzto10kHzwithadimmingrangeof256:1.
Theintegratedboostregulatorswitchingfrequencyisprogrammablefrom600kHzto1MHzbyexternalresistorforoptimumefficiencyandthesmallestexternalL/Cfilteringcomponents.
Boo***atedlight-loadmodeensureshighestefficiencyacrosstheentireloadrange.
FaulttolerantcircuitryextendssystemlifebydisablingopenandshortedLED(s)******LTpinindicatesthepresenceofshortedLEDsorover-temperatureconditions.
TheAAT1451isavailableinaPb-free,thermallyenhanced16-pin3x4TDFNpackage.
AAT1451主要特性:
?VINRange:5Vto26V
?Integrated50VBoostConverter
?MaximumIOUT:120mA
?ProgrammableSwitchingFrequency
?600kHzto1MHz
?Upto93%Efficiency
?HighEfficiencyLight-LoadMode
?FourWhiteLEDStrings
?ProgrammableMaxCurrentSinkupto30mAEach
?±2%Accuracy(22mA)
?±1.5%Matching(22mA)
?DirectPWMDimming
?AutomaticPhaseShifting
?FastTurn-On/Off
?IntegratedFaultProtectionfor
?IndependentDisableofOpen/ShortedLED(s)String(s)
?Over-Voltage
?Over-Temperature
?FAULTIndicationforShortedLED(s)andOver-Temperature
?Soft-StartMinimizesInrushCurrent
?TDFN34-16LowProfilePackage
?-40℃to+85℃TemperatureRange
AAT1451應用:
?Monitors
?NotebookandNetbookComputers
?PortableDVDPlayers
?PortableTV
?WhiteLEDBacklight
圖***1451方框圖
圖***1451典型應用電路圖
圖***1451評估板電路圖
AAT1451評估板材料清單:
AAT1451評估板表面安裝電感:
AAT1451評估板表面安裝電容:
圖***1451評估板PCB布局圖
，電路圖，。