无电解电容的发光二极管照明ACDC电源的研究

南京航空航天大学硕士学位论文无电解电容的发光二极管照明AC/DC电源的研究姓名：顾琳琳申请学位级别：硕士专业：电力电子与电力传动指导教师：阮新波20090301南京航空航天大学硕士学位论文I摘要LED照明电源是一个PFC变换器，将输入交流电压变换为稳定的直流电压，供给LED驱动器。由于LED照明电源的输入功率是脉动的，而输出功率是平直的，因此需要一个储能电容来平衡脉动的输入功率和恒定的输出功率。一般储能电容容量较大，通常选用电解电容，但是电解电容的寿命只有几千小时，远远短于LED的寿命（50,000小时），这使得LED照明电源与LED的长寿命不匹配。本文的研究目的是在满足输入功率因数不低于0.9的前提下，提出减小储能电容容量的方法，用薄膜电容来替代电解电容，以延长LED照明电源的使用寿命。本文提出增大储能电容电压纹波的方法来大幅度减小储能电容容量，这样可以采用薄膜电容替代电解电容。为了保证BoostPFC变换器的正常工作，本文推导了储能电容电压昀大值、昀小值和平均值与储能电容容量大小的关系，并给出储能电容容量的选取原则。为了进一步减小储能电容，本文分析PFC变换器的输入功率脉动与输入功率因数之间的关系，提出在输入电流中注入适量三次谐波的方法。根据照明电源的标准，输入功率因数不能低于0.9，因此注入三次谐波的幅值不得超过基波的48.4%，此时储能电容容量可以减小到输入功率因数为1时的65.6%。论文还给出三次谐波注入的具体实现方法。基于上述减小储能电容容量的方法，本文提出一种无电解电容的两级式LED照明电源方案，其前级为BoostPFC变换器，后级为Flyback变换器，它们均工作在电流临界连续模式。论文讨论该方案的主电路参数设计，给出BoostPFC变换器和Flyback变换器的小信号模型，并进行闭环设计。本文完成一台60W原理样机进行实验验证。实验结果表明本文所提出的方法是可行的。关键词：LED照明，电源，功率因数校正，谐波注入，电压纹波无电解电容的发光二极管照明AC/DC电源的研究IIABSTRACTThepowersupplyforLEDlighting,whichconvertsacommercialacvoltagetoasteadydcvoltage,shouldhavethefunctionofpowerfactorcorrection(PFC)tocomplytherequirementsoftheregulationssuchasEnergyStar.InaPFCconverter,theinputpowerispulsatingwhiletheoutputpowerisconstant,thereforeastoragecapacitorwithlargevalueisrequiredtobalancetheinstantaneouspowerdifference,andelectrolyticcapacitorisusuallyusedasthestoragecapacitor.However,itisremarkablethatthelifetimeofelectrolyticcapacitorisonlyseveralthousandhours,whichismuchlowerthanthelifetimeofLED(longerthan50,000hours),soelectrolyticcapacitoristheobstacleforthematchoflifetimeofthepowersupplyandLED.Theobjectiveofthisthesisistoproposemethodstoreducethestoragecapacitorsignificantlyatthepreconditionthattheinputpowerfactorishigherthan0.9,thusfilmcapacitorcanbeadoptedinsteadofelectrolyticcapacitortoprolongthelifetimeofthepowersupplyforLEDlighting.Inthisthesis,thevoltagerippleofthestoragecapacitorispurposelyincreasedtosignificantlyreducethevalueofthestoragecapacitor,sofilmcapacitorcanbeadoptedtoreplaceelectrolyticcapacitor,andalonglifetimeofthepowersupplyisachieved.Themaximumvoltage,minimumvoltageandaveragevoltageofthestoragecapacitorasafunctionofthevalueofthestoragecapacitorarederivedsoastoensureBoostPFCconverteroperatesnormallyinthewholeinputvoltagerange.Thedeterminationofthevalueofthestoragecapacitorisalsodiscussed.Inordertofurtherreducethevalueofthestoragecapacitor,therelationshipbetweenthepulsationoftheinputpowerandtheinputpowerfactorisanalyzed,andinjectingthe3rdharmoniccurrenttotheinputcurrentisproposedtoreducethepulsationoftheinputpower.Whileensuringtheinputpowerfactorbehigherthan0.9,theamplitudeoftheinjected3rdharmoniccurrentis0.484ofthefundamentalwavecurrent,andthestoragecapacitorcanbereducedto65.6%ofthatwithinputpowerfactorof1.0.Thecontrolmethodof3rdharmonicinjectionisalsopresentedinthisthesis.Atwo-stagepowersupplyforLEDlightingwithoutelectrolyticcapacitorisproposed,includingaBoostPFCconverterandaFlybackconverter.Bothoftheconvertersoperateindiscontinuouscurrentmode-boundarytoachievehighpowerfactorandavoidthereverserecoveryoftherectifierdiodes.Theparameterdesignofthepowerstageofthetwoconvertersisdiscussed.Thesmallsignalmodelsofthetwoconvertersarederived,andbasedonwhich,theclosedloopsaredesigned.A60Wprototypehasbeenbuiltandtestedinthelab,andtheexperimentalresultsverifythe南京航空航天大学硕士学位论文IIIproposedmethodscansignificantlyreducestoragecapacitor.KeyWords:LEDlighting;powersupply;powerfactorcorrection;harmoniccurrentinjection;voltageripple.无电解电容的发光二极管照明AC/DC电源的研究VIII图表清单图1.1飞利浦公司生产的大功率白光LED.......................................................................................2图1.2LED的一些应用实例...............................................................................................................2图1.3LED的特性曲线.......................................................................................................................3图1.4单级结构的LED照明驱动电源..............................................................................................4图1.5NationalSemiconductor生产的LED驱动芯片LM3402.......................................................4图1.6两级式结构的LED照明驱动电源..........................................................................................5图1.7两级式PFC变换器..................................................................................................................5图1.8单级式PFC变换器..................................................................................................................6图1.9PFC变换器的主要波形图.......................................................................................................7图2.1两级式PFC变换器示意图......................................................................................................9图2.2输入功率因数为1时，输入电压、输入电流、瞬时输入功率和储能电容电压的波形..10图2.3Cb电压平均值一定，电压脉动值不同时的Cb电压波形...................................................11图2.4Vc_max、Vc_min和Vc_ave与Cb的关系曲线..............................................................................13图2.5Pin=Po时，输入电压、输入电流、输入功率和输出功率的波形......................................14图2.6Pin=Po时，输入电流中前21次谐波的分布图....................................................................14图2.7基