UC3842设计的小功率开关电源

兰州交通大学毕业设计（论文）-I-摘要随着电力电子技术的发展以及创新，使得开关电源这一项技术也在不断地发展与创新，由于这一成本反转点日益向低输出电力端的移动，为开关电源提供了广阔的发展空间。开关电源是利用现代电力电子技术，控制开关管开通和关断的时间比率，维持稳定输出电压的一种电源，开关电源一般由脉冲宽度调制（PWM）控制IC和MOSFET构成。开关电源和线性电源相比，二者的成本都随着输出功率的增加而增长，但二者增长速率各异。线性电源成本在某一输出功率点上，反而高于开关电源，这一点称为成本反转点。设计论文主要是利用一种性能优良的电流控制型脉宽调制器UC3842。假如由于某种原因使输出电压升高时，脉宽调制器就会改变驱动信号的脉冲宽度，亦即占空比D，使斩波后的平均值电压下降，从而达到稳压目的，反之亦然。UC3842可以直接驱动MOS管、IGBT等，适合于制作20～80W小功率开关电源。关键词：开关电源；UC3842；脉宽调制；占空比兰州交通大学毕业设计（论文）-II-AbstractAlongwiththePowerelectronictechnologydevelopmentandinnovation,itmakethattechnologySwitchingpowersupplyisalwaysinthewayofdevelopingandinnovating,whitthecostofinversionpointsincreasinglytothelowoutputpowerendmobile,maketheSwitchpowersupplyprovideabroadspacefordevelopment.SwitchingpowersupplyusetheModernelectronictechnologytocontroltheturn-onandturn-offtimeratio,maintainthestabilityoftheoutputvoltageofPowersupply.SwitchingpowersupplyusedbyPulsewidthmodulation(PWM)ControlICandMOSFET.SwitchingpowersupplyandLinearpowercomparison,theyarecost'sastheOutputPowerincreases,Buttheirgrowthisdifferent.LinearpowersupplycostsinCertainoutputpowerpoint,ishigherthanSwitchingpowersupply.ThispointiscalledCostinversionpoint.DesignthesisismainlyusingakindofhighperformancecurrentcontrolPulsewidthmodulationUC3842.Ifsomereasonsmaketheoutputvoltagerise,Pulsewidthmodulatorcanchangethedrivesignalpulsewidth,theDutyratioD,thechopperaftertheaveragevoltagedrop,toachievethegoalofstabilizingvoltage,Thereverseisalsotrue.UC3842CandirectlydriveMOSFET,IGBTandsoon.Suitablefortheproductionof20～80WSmallpowerswitchpowersupply.KeyWords：Switchingpowersupply，UC3842，Pulsewidthmodulation，Dutyratio兰州交通大学毕业设计（论文）-III-目录摘要.............................................................................................................................IAbstract.............................................................................................................................II1绪论................................................................................................................................11.1课题背景与意义.................................................................................................11.2课题研究现状.....................................................................................................11.3本课题的研究内容与目标.................................................................................12开关电源的基本工作原理与电路结构........................................................................22.1开关电源的概述.................................................................................................22.1.1开关电源的工作原理..............................................................................22.1.2开关电源的组成......................................................................................32.1.3开关电源的特点......................................................................................42.2开关器件.............................................................................................................52.1.1开关器件的特征......................................................................................52.1.2器件TL431..............................................................................................52.1.3电力二极管..............................................................................................62.1.4光耦PC817..............................................................................................73主要开关变换电路........................................................................................................83.1滤波电路.............................................................................................................83.2反馈电路.............................................................................................................83.2.1电流反馈电路..........................................................................................83.2.2电压反馈电路..........................................................................................93.3过电压保护电路...............................................................................................104UC3842.........................................................................................................................114.1UC3842的简介.................................................................................................114.1.1UC3842的引脚及其功能......................................................................114.1.2UC3842的内部结构..............................................................................124.1.3UC3842的使用特点..............................................................................135基于UC3842设计的小功率开关电源......................................................................145.1开关电源设计指标............................................................................................145.1.1元件的选择............................................................................................145.1.2电路结构的选择....................................................................................15兰州交通大学毕业设计（论文）-IV-5.2启动电路............................