5.实际参数计算方法:
已知C1为0.33μF,交流输入为220V/50Hz,求电路能供给负载的最大电流。
C1在电路中的容抗Xc为:
Xc=1/(2πfC)=1/(2*3.14*50*0.33*10-6)=9.65K
流过电容器C1的充电电流(Ic)为:
Ic=U/Xc=220/9.65=22mA.
二线性驱动电路:
1.典型的电路如(图2)
作者简介
ChristopheVaucourt现任TI(德国)系统工程师, PowerInt公司的TFS762HG是HiperTFS系列成员,集成了两个大功率双开关正向转换器和中功率反激(副)转换器,所提供的主功率高达414W,副转换器提供高达20W功率.器件具有可编程的火线欠压(UV)检测,过压(OV)检测以及精确的延迟热关断(OTP)等保护,满负荷效率大于90%,主要应用在PC,打印机,LCDTV,视频游戏机,大功率适配器以及工业和电器大功率适配器.本文介绍了TFS762HG产品特性和亮点,方框图,主输出12V/25A,待机电源5V/2.5A的电路图以及采用TFS762HG的14.5W待机和300W主电源参考设计电路图,材料清单和主副电源变压器电路图.
TheHiperTFSdevicefamilymembersincorporatebothahigh-powertwo-switch-forwardconverterandamid-powerflyback(standby)converterintoasingle,low-profileeSIP™powerpackage.Thesinglechipsolutionprovidesthecontrollersforthetwo-switch-forwardandflybackconverters,high-andlow-sidedrivers,allthreeofthehigh-voltagepowerMOSFETs,andELiminatestheconverter’sneedforcostlyexternalpulsetransformers.Thedeviceisidealforhighpowerapplicationsthatrequirebothamainpowerconverter(two-switchforward)upto414W,andstandbyconverter(flyback)upto20W.HiperTFSincludesPowerIntegrations’standardsetofcomprehen-siveprotectionfeatures,suchasintegratedsoft-start,faultandover-loadprotection,andhystereticthermalshutdown.HiperTFSutilizesadvancedpowerpackagingtechnologythatsimplifiesthecomplexityoftwo-switchforwardlayout,mountingandthermalmanagement,whileprovidingveryhighpowercapabilitiesinasinglecompactpackage.Thedevicesoperateoverawideinputvoltagerange,andcanbeusedfollowingapower-factorcorrectionstagesuchasHiperPFS.
Two-switch-forwardpowerconvertersareoftenselectedforapplicationsdemandingcost-effectiveefficiency,fasttransientresponse,andaccuratetolerancetolinevoltagefluctuation.Thetwo-switch-forwardcontrollerincorporatedintoHiperTFSdevicesimprovesontheclassictopologybyallowingoperationconsiderablyabove60%dutycycle.ThisimprovementreducesRMScurrentsconductionlosses,minimizesthesizeandcostofthebulkcapacitor,andminimizesoutputdiodevoltageratings.Theadvanceddesignalsoincludestransformerfluxresetcontrol(saturationprotection)andcharge-recoveryswitchingofthehigh-sideMOSFET,whichreducesswitchinglosses.ThiscombinationofinnovationsyieldsanextremelyefficientpowersupplywithsmallerMOSFETs,fewerpassivesanddiscretecomponents,andalower-costtransformer.
HiperTFS’sflybackstandbycontrollerandMOSFETsolutionisbasedonthehighlypopularTinySwitch™technologyusedinbillionsofpowerconverterICsduetoitssimplicityofoperation,lightloadefficiency,andrugged,reliable,performance.Thisflybackconvertercanprovideupto20Wofoutputpowerandthebuiltinoverloadpowercompensationreducescomponentdesignmargin.
TFS762HG产品亮点:
ProtectedTwo-SwitchForwardandFlybackCombinationSolution
Incorporatesthreehigh-voltagepowerMOSFETs,mainandstandbycontrollers,andgatedrivers
Levelshifttechnologyeliminatesneedforpulsetransformer
Programmablelineundervoltage(UV)detectionpreventsturn-offglitches
Programmablelineovervoltage(OV)detection;latchingandnon-latching
Accuratehystereticthermalshutdown(OTP)
Accurateselectablecurrentlimit(mainandstandby)
Outputover-currentprotection(OCP)
Fullyintegratedsoft-startforminimumstart-upstress
SimplefastACreset
ReducedEMI
Synchronized66kHzforwardand132kHzflybackconverters
Frequencyjitter
Eliminatesupto30discretecomponentsforhigherreliabilityandlowercost
AsymmetricalTwo-SwitchForwardReducesLosses
Allows>50%dutycycleoperation
ReducesprimarysideRMScurrentsandconductionlosses
Minimizesthesizeandcostofthebulkcapacitor
Allowsreducedcapacitanceorlongerhold-uptime
Allowslowervoltageoutputdiodes
Transformerresetcontrol
Preventstransformersaturationunderallconditions
ExtendsdutycycletosatisfyACcycledropoutridethrough
Dutycyclesoft-startwith115%currentlimitboost
Satisfies2ms~20msstart-upwithlargecapacitanceatoutput
Outputshortcircuitprotection(SCP)withauto-restart
RemoteON/OFFfunction
Voltagemodecontrollerwithcurrentlimit
20WFlybackwithSelectablePowerLimit
TinySwitch-IIIbasedconverter
Selectablepowerlimit(10W,12.5W,15W,or20W)
Built-inoverloadpowercompensation
Flatoverloadpowervs.inputvoltage
Reducescomponentstressduringoverloadconditions
Reducesrequireddesignmarginfortransformerandoutputdiode
Outputovervoltage(OV)protectionwithfastACreset
Latching,non-latching,orauto-restart
Auto-restart
AdvancedPackageforHighPowerApplications
434Woutputpowercapabilityinahighlycompactpackage
Upto550Wpeak
Simpleclipmountingtoheatsink
Canbedirectlyconnectedtoheatsinkwithoutinsulationpad
ProvidesthermalimpedanceequivalenttoaTO-220
HeatslugconnectedtogroundpotentialforlowEMI
Staggeredpinarrangementforsimpleroutingofboardtracesandhigh-voltagecreepagerequirements
Singlepowerpackagefortwopowerconvertersreducesassemblycostslayoutsize
TFS762HG主要优势:
Singlechipsolutionfortwo-switchforwardmainandflybackstandby
Highintegrationallowssmallerformfactorandhigherpowerdensitydesigns
Incorporatescontrol,gatedrivers,andthreepowerMOSFETS
Levelshifttechnologyeliminatesneedforpulsetransformer
Protectionfeaturesinclude:UV,OV,OTP,OCP,andSCP
Transformerresetcontrol
Preventstransformersaturationunderallconditions
Allows>50%dutycycleoperation
ReducesprimarysideRMScurrentsandconductionlosses
Standbysupplyprovidesbuilt-inoverloadpowercompensation
Upto434Wtotaloutputpowerinahighlycompactpackage
Upto550Wpeak
Highefficiencysolutioneasilyenablesdesigntomeetstringentefficiencyspecifications
>90%efficiencyatfullload
No-loadregulationandlowlossesatlight-load
Simpleclipmountingtoheatsinkwithoutneedforinsulationpad
HalogenfreeandRoHScompliant
TFS762HG应用:
PC
Printer
LCDTV
Videogameconsoles
High-poweradapters
Industrialandappliancehigh-poweradapters
图1.TFS762HG两开关正向转换器方框图
图2.TFS762HG两开关正向和反激(副)转换器简化电路图
图3.TFS762HG高效电路图:主输出12V/25A,副电源5V/2.5A
采用TFS762HG的14.5W副和300W主电源参考设计
参考设计主要特性:
HighefficiencyMainandStandbyconverters
Remoteon/off
Built-inmainandstandbyundervoltagethresholdsprotectionensuresgraceful
powersupplystart-upandshutdown
Latchingoutputovervoltageprotection
Integratedhigh-sidedriver
Outputshort-circuitandopenloopprotection
Maintransformerresetprotection
Flatstandbyoverloadversusinputvoltage
Thisdocumentisanengineeringreportdescribinga5V,2.9AStandbyanda12V,25AMainpowersupplyutilizingtheTFS762HGdevicefromtheHiperTFSfamily.
ThisexamplepowersupplyusesafixedDCinputvoltage,butinatypicalapplication,itwouldbeconnectedtoaPFCboostinputstage,deliveringapproximately385VDCtoimplementa300Wpowersupplywithvariousoutputvoltages.AlabbenchDCpowersupplycapableof400VDCat3AoranACinputrectifierstageisrequiredsupplytotheinputforevaluation.ItisalsopossibletousethepowerfactorcircuitRDK-236toprovidetheregulated385VDCneededtopowerRDK-249.
TypicallyPCpowersupplieshaveauniversalACinputpowerfactorcorrected(PFC)inputstagebutasthebiasstandbysupplymustoperatebeforethePFCstageisactive,theStandbyoutputmustoperatewiththeDCequivalentofuniversalACinputvoltages(85VACto265VACand100VDCto400VDC).
图4.采用TFS762HG的电源外形图
采用TFS762HG的电源指标:
图5.采用TFS762HG的参考设计电源电路图
采用TFS762HG的参考设计电源材料清单(BOM):
StandbyTransformerSpecification
图6.副电源变压电路图
MainTransformerSpecification
图7.主电源变压电路图
,
5。1A18为实测电流输出为18.4-18.8mA之间, 1、分布式恒流技术
分布式恒流就是:在各并联支路点均设立独立恒流源,从而管理、维持、控制支路与整体线路稳定。在使用上可视为一个完整的线路结构,而实际应用是分布在线路各节点的恒流控制并能相互通讯。分布式恒流设计LED产品,有着非常高的产品稳定性。在当前,LED产品宣称与实际使用寿命有较大的差距,在驱动线路设计技术积累有限的情况下,评估产品寿命与实际使用有距离。驱动线路稳定性直接影响产品整体稳定,分布式恒流有着独有的优势。
保持支路和整体电流稳定,还要能方便控制管理支路和整体线路工作,这是分布式恒流技术的包含范围。驱动LED需要恒流,但是电流的大小取决于应用环境,LED照明智能化发展是关键,分布式恒流技术充份预留智能化接口。
在分布式LED驱动设计中,驱动回搜、色温可调、灰度控制都要变得方便。这是分布式恒流技术发展的必要性,随温度变化驱动电压要适当调整,客户设计因产品而异LED数量不一,支路恒流平衡都需要回授线路完成。LED在迅速替代CCFL作为新一代背光源,但是我们发现显色性并没有CCFL好,色温也不能可调,不是我们不需要LED色温可调整,关键是设计线路不支持色温可调整。
在LED应用中,灰度也需要很好的表现,灰度控制总是会和亮度混淆,实际上有着本质的区别,灰度控制代表着智能化的水平程度,而亮度在产品中只设定一次,智能化一定离不了灰度等级再现。
分布式恒流技术还有一个特点是,让AC电源部分继续采用传统开关电源,恒压的供电模式。开关电源技术积累会给LED电源设计创造品质条件,虽然加速老化估算电源寿命是一种办法,和传统开关电源长期实战技术积累还是有些差距!
分布式恒流也有它缺点,开始会增加部分设计成本,产品设计品质与线路设计选择需要权衡。可能成本增加是短暂的,表面的,应该综合考量。
2、分布式恒流源节点设置
分布式恒流技术就是在需要恒流的节点上串接,低压差线性恒流驱动器。低压差很重要,关系到产品驱动效率。做到恒流驱动有很多种,其中低压差线性恒流就可以实现一切LED应用设计,即稳定又简单,结合开关电源,有着完美的恒流驱动架构。
恒流源放置点灵活,在所有的并联支路,不会因支路电流变化影响其它支路工作。都希望挑选LED得到负载阻抗匹配,分布式恒流可以设计变得更完美,要求不是很高也可以免除挑选。保持各支路和整体线路电流稳定,才能提升灯具产品稳定性。
恒流源放置,在每个并联支路节点,也可以是整体的恒流点设计,恒流源串接支路中在某一个位置都能起到很好的作用。一般恒流驱动通道数很难与设计匹配,分布式恒流会有着高度的设计灵活性。
在LED照明线路设计中,AC电源需要回授电路,配合输出LED驱动数量,和驱动效率的合理性。在分布式恒流驱动源中,每一个驱动源都可以直接完成光耦回授任务。
3、恒流输出软件化将开辟,LED应用技术的飞跃
在日常驱动电源设计中,周边器件累计误差处理起来很是棘手,结果驱动电源参数离设计初衷相差甚远。恒流驱动需要电流检测,通常做法是在支路中串接毫偶电阻获取回授信息,要达到高的效率,电阻值会越小,过小的毫偶电阻给生产、测试都带来麻烦,一般的仪器无法验证到正确值,生产过程会影响到精度,电流值被固定,调整非常不便。
分布式恒流输出软件化将开辟,LED应用技术的飞跃,LED恒流技术软件化,大幅提升LED应用的灵活性。恒流驱动器电流设定软件化实际上也很简单,在IC内部设立寄存器,根据实际产品应用存储的方式设置输出电流大小,这一切都是软件化过程,不需要更改线路设计。在销售器件的同时附赠上微机操作软件,直观的数字写入完成电路电流设定。
驱动线路周边0器件,这是我们的目标,周边0器件不会带来设计器件参数误差累计,因周边器件误差累计而造成的恒流精度回升到0。
4、驱动优势
我们将恒流输出范围均等的划分若干等级,每阶电流被数字化描述,指定在一定空间内的寄存器,上电驱动IC会读取对应数字并执行相应电流值。内置E2PROM是首选,任何寄存器都能完成其任务,按照应用需要和工艺允许程度,决定存储器的类型选择。
在开发驱动技术的同时,也要同时开发应用软件,友好的界面支持数字化写入技术,使得LED驱动电源设计变得更简单,更智能。
电流阶划分与设计要求有所不同,因长运通公司型号对应市场不同有所区别。分布式恒流内置寄存器后,电流值划分会弥补工艺上的精度不足,因制造工艺原因输出电流总是有误差,因此得到改善。
驱动IC出厂时可以确定输出电流大小,可根据不同的客户,提供不同的电流输出值,免除批量校准过程。对于小客户来讲,通过附赠上微机软件改写电流值,是最为方便的方式。还有一种情况,也是客户经常需要的,比如对产品的亮度要求,允许驱动电流不同,要求产品亮度一致,从而通过产品设计接口解决终端客户对亮度的要求。在年久后,因LED光衰减或根据现实使用情况,再次确定驱动电流值及用途。
5、分布式接口
分布式恒流技术需要分布式通讯方式支持,LED智能化要有先进的通讯技术完成。单线数据传输,被选定为LED分布式技术通讯方式,采用曼彻斯特编码,固定速率400Kbps,通讯可靠传输距离大于1米,级联可达1024个恒流源,内置150℃温度保护,同时提供光耦驱动接口。
在分布式恒流技术中,每一颗独立的恒流源,都能完成光耦回授。根据恒流源压差信息,直接驱动光耦,完成电路回授过程。做到周边设计0器件,电源输出电压与负载阻抗匹配,实现恒流源与光源集成。
6、AC电源发展方向分析
1.原边反馈电源
用于小功率LED灯具驱动,采用原有原边反馈充电器开关电源移植而来。这部分AC驱动没有因LED应用而改变规格,有着诸多的型号供选择,除体积受限外设计上与开关电源没有本质区别,借来应用到LED也算合理。
2.大功率隔离照明电源
LED全部是采用开关电源而设计,任何公司到目前为止都没有推出针对LED专用AC驱动器件,隔离设计就是设计开关电源,LED产业热顺道说给LED开发而已,基本可以断言开关电源就是LED-AC驱动,也是主要的应用方式之一。
3.非隔离LED驱动电源
非隔离LED驱动推出较多针对性电源技术,是值得肯定的,是LED电源一个方向。隔离安全主要取决于与外壳爬电间隙设计,并没有规定LED电源一定要隔离设计,也没有限制输出电压值,关键是采用哪种隔离安全,非隔离有驱动效率高等优点,结合结构也能设计出优质、安全、高效的LED产品。
4.可控硅调光兼容性电源
特殊应用,数量受限,有过渡性安排。
最后总结!
这几年我们主张《先恒压,再恒流》,会是LED照明市场主流,经过这两年的发展严谨的定义为《分布式恒流》技术。虽然各大公司,诸多的专家学者在致力于《LED照明电源》研究,我们依然看到的还是开关电源而已!为此LED照明电源主要研究的重点应该放在:次级DC部分,恒压开关电源与分布式恒流技术结合。
,最新推出了用于住宅及商业LED照明应用的LED驱动器NCL30000。这器件使用临界导电模式(CrM)反激架构,中艾电源
TheZLED7022,oneofourZLEDfamilyofLEDcontrolICs,isalow-noise,constant-frequencychargepumpDC/DCconverterthatcandriveuptosixLEDchannELs,providingaprogrammableconstantcurrentlevelrangingfrom1.8mAto20mAperLEDchannel.ItcanalsodrivehighercurrentLEDsbecauseitscurrentsinkscanoperateinparallel.ItenableswhiteorothercolorLEDapplicationsthatrequireuniformintensityand/orlinearprogressionsinbrightness.CapableofoperatingefficientlywithDCvoltagesuppliesrangingfrom2.8Vto5.5V,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优势:
Currentmatchingaccuracy:±0.9%(typical)
One-pinon/offorbrightnesscontrolforuptosixLEDsviaasimplePCCserialinterface—nopulse-widthmodulationoradditionalcontrolcircuitneeded
14programmablecurrentlevelsforachievingreal-timecontrolofeffectssuchasLEDfade-outorsuddenchangesinbrightness
LowEMIandback-injectednoisebecausethechargepumpisnotinductor-based
Veryfewexternalcomponentsneededforoperation
FlexibledesignenablesdiverseLEDapplications:upto20mAperchannel
LEDdriverfamilyconceptwithlow-voltagefour-channelLEDdriverZLED7012
ZLED7022典型应用:
LEDbacklightingforportabledevices
LEDlightingforcellphones,smartphones.PDAs
Illuminationofdigitalphotoframes
BacklightingforGPS/navigationsystems
LowvoltageLEDlightingfixtures
Generalpurposelow-voltageindustrialandconsumerapplications
图1.ZLED7022方框图
图2.ZLED7022应用电路
图3.ZLED7022采用D4:D0的基本应用电路
,普通白光LED需要3.6V偏置电压和最大20mA的偏置电流。图1给出了可以调节7个白光LED串亮度的低成本电感型升压电路。
这个电路可以分成两个部分:由Q1和Q2组成的升压电路,
NS公司的RD-173-MR16和PAR38LED灯参考设计采用LM3429多功能高压LED控制器和LM2841/42PWMDC/DC降压稳压器.LM3429的输入电压可从4.5V到75V,具有快速(50kHz)PWM调光特性;而LM2841/42的输入电压从表面上看4.5V到42V,输出电流300mA或600mA可选择.RD-173-MR16和PAR38LED灯参考设计输入电压为9V到36V,这样可采用12V和24V电源,以适应各种应用,可驱动1-12个串联连接的LED,驱动电流高达1A.本文介绍了LM3429和LM2841/42的主要特性以及典型应用电路.此外还未集中介绍了RD-173-MR16和PAR38LED灯参考设计的主要特性,外形图,详细电路图和所用元件清单和PCB布局图.
LM3429:N-ChannELControllerforConstantCurrentLEDDrivers
TheLM3429isaversatilehighvoltageLEDdrivercontroller.WiththecapabilitytobeconfiguredinaBuck,Boost,Buck-Boost(Flyback),orSEPICtopology,andaninputandoutputoperatingvoltageratingof75V,theLM3429isidealforilluminatingLEDsinaverydiverse,largefamilyofapplications.
Adjustablehigh-sidecurrentsensewithatypicalsensevoltageof100mVallowsfortightregulationoftheLEDcurrentwiththehighestefficiencypossible.OutputLEDcurrentregulationisbasedonpeakcurrent-modecontrolwithpredictiveOff-TimeControl.Thismethodofcontroleasesthedesignofloopcompensationwhileprovidinginherentinputvoltagefeed-forwardcompensation.
TheLM3429includesahigh-voltagestartupregulatorthatoperatesoverawideinputrangeof4.5Vto75V.TheinternalPWMcontrollerisdesignedforadjustableswitchingfrequenciesofupto2.0MHz,thusenablingcompactsolutions.Additionalfeaturesinclude:precisionreference,logiccompatibleDIMinputsuitableforfastPWMdimming,cycle-by-cyclecurrentlimit,andthermalshutdown.
TheLM3429comesinalowprofile,thermallyefficientTSSOPEP14-leadpackage.
详情请见PDF文档LED驱动方案.rar
来源:NS
,IOUT=IIN/K。
因此,中艾电源LED电源批发驱动电流可达500mA,且无需额外电容,
高压、可调恒流LED驱动器MAX16800及其应用
读全文请点击PDF文件
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
TheHiperTFSdevicefamilymembersincorporatebothahigh-powertwo-switch-forwardconverterandamid-powerflyback(standby)converterintoasingle,low-profileeSIP™powerpackage.Thesinglechipsolutionprovidesthecontrollersforthetwo-switch-forwardandflybackconverters,high-andlow-sidedrivers,allthreeofthehigh-voltagepowerMOSFETs,andELiminatestheconverter’sneedforcostlyexternalpulsetransformers.Thedeviceisidealforhighpowerapplicationsthatrequirebothamainpowerconverter(two-switchforward)upto414W,andstandbyconverter(flyback)upto20W.HiperTFSincludesPowerIntegrations’standardsetofcomprehen-siveprotectionfeatures,suchasintegratedsoft-start,faultandover-loadprotection,andhystereticthermalshutdown.HiperTFSutilizesadvancedpowerpackagingtechnologythatsimplifiesthecomplexityoftwo-switchforwardlayout,mountingandthermalmanagement,whileprovidingveryhighpowercapabilitiesinasinglecompactpackage.Thedevicesoperateoverawideinputvoltagerange,andcanbeusedfollowingapower-factorcorrectionstagesuchasHiperPFS.
Two-switch-forwardpowerconvertersareoftenselectedforapplicationsdemandingcost-effectiveefficiency,fasttransientresponse,andaccuratetolerancetolinevoltagefluctuation.Thetwo-switch-forwardcontrollerincorporatedintoHiperTFSdevicesimprovesontheclassictopologybyallowingoperationconsiderablyabove60%dutycycle.ThisimprovementreducesRMScurrentsconductionlosses,minimizesthesizeandcostofthebulkcapacitor,andminimizesoutputdiodevoltageratings.Theadvanceddesignalsoincludestransformerfluxresetcontrol(saturationprotection)andcharge-recoveryswitchingofthehigh-sideMOSFET,whichreducesswitchinglosses.ThiscombinationofinnovationsyieldsanextremelyefficientpowersupplywithsmallerMOSFETs,fewerpassivesanddiscretecomponents,andalower-costtransformer.
HiperTFS’sflybackstandbycontrollerandMOSFETsolutionisbasedonthehighlypopularTinySwitch™technologyusedinbillionsofpowerconverterICsduetoitssimplicityofoperation,lightloadefficiency,andrugged,reliable,performance.Thisflybackconvertercanprovideupto20Wofoutputpowerandthebuiltinoverloadpowercompensationreducescomponentdesignmargin.
TFS762HG产品亮点:
ProtectedTwo-SwitchForwardandFlybackCombinationSolution
Incorporatesthreehigh-voltagepowerMOSFETs,mainandstandbycontrollers,andgatedrivers
Levelshifttechnologyeliminatesneedforpulsetransformer
Programmablelineundervoltage(UV)detectionpreventsturn-offglitches
Programmablelineovervoltage(OV)detection;latchingandnon-latching
Accuratehystereticthermalshutdown(OTP)
Accurateselectablecurrentlimit(mainandstandby)
Outputover-currentprotection(OCP)
Fullyintegratedsoft-startforminimumstart-upstress
SimplefastACreset
ReducedEMI
Synchronized66kHzforwardand132kHzflybackconverters
Frequencyjitter
Eliminatesupto30discretecomponentsforhigherreliabilityandlowercost
AsymmetricalTwo-SwitchForwardReducesLosses
Allows>50%dutycycleoperation
ReducesprimarysideRMScurrentsandconductionlosses
Minimizesthesizeandcostofthebulkcapacitor
Allowsreducedcapacitanceorlongerhold-uptime
Allowslowervoltageoutputdiodes
Transformerresetcontrol
Preventstransformersaturationunderallconditions
ExtendsdutycycletosatisfyACcycledropoutridethrough
Dutycyclesoft-startwith115%currentlimitboost
Satisfies2ms~20msstart-upwithlargecapacitanceatoutput
Outputshortcircuitprotection(SCP)withauto-restart
RemoteON/OFFfunction
Voltagemodecontrollerwithcurrentlimit
20WFlybackwithSelectablePowerLimit
TinySwitch-IIIbasedconverter
Selectablepowerlimit(10W,12.5W,15W,or20W)
Built-inoverloadpowercompensation
Flatoverloadpowervs.inputvoltage
Reducescomponentstressduringoverloadconditions
Reducesrequireddesignmarginfortransformerandoutputdiode
Outputovervoltage(OV)protectionwithfastACreset
Latching,non-latching,orauto-restart
Auto-restart
AdvancedPackageforHighPowerApplications
434Woutputpowercapabilityinahighlycompactpackage
Upto550Wpeak
Simpleclipmountingtoheatsink
Canbedirectlyconnectedtoheatsinkwithoutinsulationpad
ProvidesthermalimpedanceequivalenttoaTO-220
HeatslugconnectedtogroundpotentialforlowEMI
Staggeredpinarrangementforsimpleroutingofboardtracesandhigh-voltagecreepagerequirements
Singlepowerpackagefortwopowerconvertersreducesassemblycostslayoutsize
TFS762HG主要优势:
Singlechipsolutionfortwo-switchforwardmainandflybackstandby
Highintegrationallowssmallerformfactorandhigherpowerdensitydesigns
Incorporatescontrol,gatedrivers,andthreepowerMOSFETS
Levelshifttechnologyeliminatesneedforpulsetransformer
Protectionfeaturesinclude:UV,OV,OTP,OCP,andSCP
Transformerresetcontrol
Preventstransformersaturationunderallconditions
Allows>50%dutycycleoperation
ReducesprimarysideRMScurrentsandconductionlosses
Standbysupplyprovidesbuilt-inoverloadpowercompensation
Upto434Wtotaloutputpowerinahighlycompactpackage
Upto550Wpeak
Highefficiencysolutioneasilyenablesdesigntomeetstringentefficiencyspecifications
>90%efficiencyatfullload
No-loadregulationandlowlossesatlight-load
Simpleclipmountingtoheatsinkwithoutneedforinsulationpad
HalogenfreeandRoHScompliant
TFS762HG应用:
PC
Printer
LCDTV
Videogameconsoles
High-poweradapters
Industrialandappliancehigh-poweradapters
图1.TFS762HG两开关正向转换器方框图
图2.TFS762HG两开关正向和反激(副)转换器简化电路图
图3.TFS762HG高效电路图:主输出12V/25A,副电源5V/2.5A
采用TFS762HG的14.5W副和300W主电源参考设计
参考设计主要特性:
HighefficiencyMainandStandbyconverters
Remoteon/off
Built-inmainandstandbyundervoltagethresholdsprotectionensuresgraceful
powersupplystart-upandshutdown
Latchingoutputovervoltageprotection
Integratedhigh-sidedriver
Outputshort-circuitandopenloopprotection
Maintransformerresetprotection
Flatstandbyoverloadversusinputvoltage
Thisdocumentisanengineeringreportdescribinga5V,2.9AStandbyanda12V,25AMainpowersupplyutilizingtheTFS762HGdevicefromtheHiperTFSfamily.
ThisexamplepowersupplyusesafixedDCinputvoltage,butinatypicalapplication,itwouldbeconnectedtoaPFCboostinputstage,deliveringapproximately385VDCtoimplementa300Wpowersupplywithvariousoutputvoltages.AlabbenchDCpowersupplycapableof400VDCat3AoranACinputrectifierstageisrequiredsupplytotheinputforevaluation.ItisalsopossibletousethepowerfactorcircuitRDK-236toprovidetheregulated385VDCneededtopowerRDK-249.
TypicallyPCpowersupplieshaveauniversalACinputpowerfactorcorrected(PFC)inputstagebutasthebiasstandbysupplymustoperatebeforethePFCstageisactive,theStandbyoutputmustoperatewiththeDCequivalentofuniversalACinputvoltages(85VACto265VACand100VDCto400VDC).
图4.采用TFS762HG的电源外形图
采用TFS762HG的电源指标:
图5.采用TFS762HG的参考设计电源电路图
采用TFS762HG的参考设计电源材料清单(BOM):
StandbyTransformerSpecification
图6.副电源变压电路图
MainTransformerSpecification
图7.主电源变压电路图
,其最小值可通过以下公式计算得出:
其中,。