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I本科生毕业设计（论文）题目：反激式开关电源设计姓名：陈信学号：110700205学院：物理与信息工程学院专业：通信工程年级：2007级指导教师：（签名）2011年月日II反激式开关电源设计中文摘要随着电子科技的不断发展，越来越多的电器设备走进了千家万户，要想让这些电器为我们服务，又离不开电源的驱动。而开关电源因其高效率、低体积、低功耗、高可靠性等一系列的优点受到了人们的亲赖。开关电源（电源适配器）实质上就是一个将高压交流电转换成低压直流电的装置。本论文采用了反激式的拓扑结构，所谓反激式即在MOSFET管关断的时候次级的二极管才导通，这时候储存在变压器的能量才会传递到次级，供输出所用。本次设计以LD7576作为核心芯片，它同时具备了过负载保护、过电压保护、过温保护等功能，在很大程度上简化了电路。在这些的基础上运用脉冲宽度调制（PWM）的原理来完成设计，脉宽调制是通过固定脉冲周期，改变占空比来控制MOSFET管导通和断开的比率从而控制输出。使得电路更简单，精度更高，同时也能满足不同的电器对输入电压范围，输出电压大小不同的要求。为了实现电压输出的稳定，同时考虑到各国的市电电压和频率的不同，电路中集合了很多模块，比如EMI滤波电路、变压电路、输出整流滤波电路、光电耦合反馈回路、尖峰电压吸收回路等。这样不但可以提高电路的精度和效率，同时也使得电路稳定性和安全性得到大幅度的提高。该电路具有宽电压输入，多路稳定输出、纹波和噪声可控制等优点。在完成电路的研究和焊接后进行了PCB板的测试，通过不断的改进与完善，最终得到的结果基本符合预期，效果比较理想。关键词：反激式，开关电源，脉宽调制，拓扑结构，电源适配器IIIDesignofFlybackSwitchingPowerSupplyAbstractWiththecontinuousdevelopmentofelectronictechnology,moreandmoreelectricalequipmentcomeintotheordinaryfamily.Toletthemserveus,wecan’tdowithoutpower.Becauseofitshighefficiency,lowvolume,lowpower,highreliabilityandaseriesofadvantages,theswitchingpowersupplyisusedoften.Switchingpowersupplyisessentiallyadevicewhichtransformsthehighvoltagealternatingcurrentintothelowvoltagedirectcurrent.Thispaperusesaflybacktopology,thesecondarydiodeconductsonlywhentheMOSFETisturnedoff,.thentheenergystoredinthetransformerwillbedeliveredtothesecondaryforoutput,sowecalleditflyback.AtthesametimeweuseLD7576asthecorechip,LD7576combineswiththeoverloadprotection,overvoltageprotection,overtemperatureprotectionandsoon,whichsimplifiesthecircuitinalargeextent.Anditusespulsewidthmodulation(PWM)tocompletethedesign,itcontrolstherateofturningonandoffoftheMOSFETbyfixespulsewidthmodulationcycleandchangesthedutycycletocontroltheoutput.Inthisway,thecircuitwillbeeasier,moreaccurate,andalsomeettherangeofinputvoltageandoutputvoltagerequirementsfordifferentelectrical.Inordertoachieveastableoutputvoltage,andinconsiderationofdifferentvoltageandfrequencyindifferentcountries.Thiscircuitincludeslotsofmodules,suchastheEMIfiltercircuit,thetransformercircuit,theoutputrectifierfiltercircuit,coupledoptoelectronicfeedbackloop,thepeakvoltageabsorbingcircuitandsoon.Thiswillnotonlyimprovetheaccuracyandefficiencyofthecircuit,butalsomakethecircuitstabilityandsecuritybegreatlyenhanced.Thecircuithasawidevoltageinput,multipleoutputstability,rippleandnoisecanbecontrolled.WeteststhePCBaftercompletethecircuit,andthroughcontinuousimprovementandperfection,theresultsareconsistentwithexpectationsandtheeffectisideal.Keywords：Flyback,SwitchingPower,PWM,TopologyStructure,AdapterI目录中文摘要...........................................................................IIABSTRACT..........................................................................III第1章绪论.......................................................................11.1课题背景及意义.................................................................11.2研究现状.......................................................................11.3研究内容.......................................................................21.4论文的章节安排.................................................................2第2章原理简介.....................................................................32.1开关电源的工作原理..............................................................32.2开关电源的工作模式..............................................................42.3开关电源的拓扑结构..............................................................42.3.1Boost（StepUp）升压电路....................................................42.3.2Buck（StepDown）降压电路...................................................52.3.3反激（升降压）电路..........................................................62.4电路设计的目标与实现框图........................................................72.5本章小结........................................................................8第3章电路的选择与论证.............................................................93.1电路拓扑结构的选择..............................................................93.2变压器的选择...................................................................103.2.1变压器参数计算.............................................................103.2.2变压器材料选择.............................................................113.3本章小结.......................................................................12第4章电路的设计与分析............................................................134.1输入电路的设计与分析...........................................................134.1.1EMI电路的设计与分析........................................................134.1.2整流电路的设计与分析.......................................................144.2功率电路的设计与分析...........................................................154.2.1LD7576简介与使用...........................................................154.2.2直流变换电路的设计与分析...................................................174.2.3次级整流滤波电路的设计与分析...............................................184.3反馈电路的设计与分析...........................................................204.4本章小结.......................................................................22第5章电路调试....................................................................23结论..........