全桥LLC谐振变换器研究

论文题目：全桥LLC谐振变换器研究专业：电力电子与电力传动硕士生：文美娟(签名)指导教师：张刚刘树林(签名)摘要随着开关电源向高频、高效和高功率密度方向的发展，传统的硬开关在应用中出现了很多问题。为解决这些问题，软开关技术应运而生。谐振型开关变换器作为软开关的一种，具有工作频率高、损耗小、效率高、体积小等优点。而LLC谐振型开关变换器以其兼具能够在全负载范围内实现原边开关管的ZVS开通，整流二极管的ZCS关断的特点和便于磁集成、输入电压范围宽等优势，在高频开关领域获得了广泛的关注和应用。本文首先研究了谐振型开关变换器的发展及其分类，并对各种谐振变换器的优缺点进行了比较和总结。在此基础上对全桥LLC谐振变换器的工作原理进行了详细分析，同时还分析了其频率特性、空载特性以及短路特性，指出了变换器各参数对其工作情况的影响。其次，采用MC33067作为全桥LLC谐振变换器的主要控制芯片，探讨了变换器主电路以及驱动电路的详细设计过程，其中包括主开关管、整流二极管、输出滤波电容等元器件的参数计算及选型，着重给出了谐振电感、谐振电容等谐振元件以及主变压器、驱动变压器等磁性元件的选择依据和设计方法。最后，采用Saber软件对该变换器主电路进行了仿真分析并搭建了实验样机，详细分析了实验过程中遇到的几个问题，如变换器不能工作在感性状态、工作频率不可线性变化，并给出了相应的解决方案。本文设计了一台500W的全桥LLC谐振变换器实验样机。通过对样机的测试得到了变换器开关管的驱动波形、谐振电流以及输出纹波电压等波形。经过对这些波形的分析可知，文中的理论研究和设计方法都是合理可行的。关键词：全桥LLC谐振变换器，ZVS，空载特性，MC33067研究类型：应用研究Subject：ResearchonFullBridgeLLCResonantConverterSpecialty：PowerElectrics&PowerDrivesName：WenMeijuan(Signature)Instructor：ZhangGangLiuShulin(Signature)ABSTRACTWiththedevelopmentoftheswitchingpowersupplytowardthehighfrenquency,efficiencyandpowerdensity,thetraditionalhardswitchingappearsalotofproblemsintheapplication.Tosolvetheseproblems,thesoftswitchingtechnologycomesintobeing.Asakindofsoftswitching,theresonanceswitchingconverterhastheadvantagesofhighfrequency,lowloss,highefficiency,smallsize,andsoon.AstheLLCresonantpowerconvertercanachievebothZVSoftheprimaryswitchandZCSoftherectifierdiodeinfullloadrangeandhavetheadvantagesofeasyintegrating,wideinputvoltagerangeandsoon,itgetswideattentionandapplicationinthehighfrequencyswitchingfield.Firstly,thebasicclassificationofresonantconvertersandtheadvantagesanddisadvantagesofvariousresonantconvertersareanalyzedinthispaper.Onthisbasis,notonlytheworkingprinciplebutalsothefrequencycharacteristic,no-loadcharacteristicandshort-citcuitcharacteristicoftheconverterarediscussedindetail.Andtheimpactsoftheparametersontheconverterarepointedout.Inaddition,thehighperformanceresonantmodecontrollerMC33067isselectedasthemaincontrolchipoftheconverter.Thedetaileddesignprocessoftheconverter’smainanddrivecircuitsareinvestigated,includingtheparameters’calculationandselectionofmainswitch,rectifierdiodeandoutputfiltercapacitor.Especially,theselectingbasisanddesignmethodoftheresonanceelements(e.g.theresonantinductor,capacitorandsoon)andmagneticelements(suchasthemaintransformeranddrivetransformer,etc.)aregiven.Finally,Sabersoftwareisadoptedtosimulateandanalyzethemaincircuitoftheconverter.Anexperimentalprototypeissetup,andsomeproblems,e.g.,theconvertercan’tworkontheinductivestateandtheoperatingfrequencycan’tbelinearchange,intheexperimentareanalyzedindetailandthecorrespondingsolutionsaregiven.A500Wfull-bridgeLLCresonantconverterprototypeisdesignedinthispaper.Waveformsofswitch,resonantcurrentandtheoutputripplevoltagecanbeobtainedaccordingtotheprototypetest.Itprovesthatthetheoreticalresearchanddesignmethodinthispaperarereasonableandfeasible.Keywords：FullbridgeLLCresonantconverter,ZVS,Noloadcharacteristic,MC33067Thesis：ApplicationResearch目录I目录1绪论..........................................................................................................................11.1本课题研究背景及意义................................................................................................11.2国内外研究动态和发展趋势........................................................................................21.2.1谐振型开关变换器的研究动态.............................................................................21.2.2LLC谐振变换器的发展趋势.................................................................................91.3本文的主要研究内容..................................................................................................102全桥LLC谐振变换器的原理及特性........................................................................122.1全桥LLC谐振变换器的主电路结构.........................................................................122.2全桥LLC谐振变换器的等效电路及工作区域..........................................................132.2.1全桥LLC谐振变换器的等效电路......................................................................132.2.2全桥LLC谐振变换器的工作区域......................................................................162.3全桥LLC谐振变换器工作原理分析.........................................................................192.3.1变换器在fmffr时工作原理...............................................................................192.3.2变换器在f=fr时工作原理....................................................................................242.3.3变换器在ffr时工作原理....................................................................................252.4全桥LLC谐振变换器的特性分析.............................................................................282.4.1频率特性..............................................................................................................282.4.2空载特性..............................................................................................................302.4.3短路特性..............................................................................................................322.5本章小结...............................................................................................................