I 摘摘 要要 开关电源是应用于广泛领域的一种电力电子装置。它具有电能转换效率高、 体积小、重量轻、控制精度高和快速性好等优点，在小功率范围内基本取代了线 性电源，并迅速想大功率范围推进，在很大程度上取代了晶闸管相控整流电源。 可以说，开关电源技术是目前中小功率直流电能变换装置的主流技术。 本文首先描述了开关电源的发展， 对目前出现的几种典型的开关电源技术作 了归纳总结和分析比较， 在此基础上指出了开关电源技术的发展状况和开关电源 产品的发展趋势。并且对开关电源的发展史、应用范围、主电路的选择、控制方 法作了简要的介绍。在设计中主要采用了脉宽调制（PWM）、全桥整流、自锁保 护等技术，应用了控制芯片 UC3842 做为 PWM 控制芯片，对变压器次级线圈采用 堆叠式绕法，改进光耦反馈电路的选择，使电路能达到所需基本要求同时，力求 稳定、高效。 关键字：开关电源，拓扑结构，变压器，正激式 II Abstract The switch power supply is a kind of electric power electronics which applies in the extensive realm to be used.It has an electric power conversions efficiency high, the physical volume is small, the weight is light, the control accuracy is high with fast etc. advantage, within the scope of small power replaced line power supply, and in high-power scope propulsion quickly, to a large extent,it replaced the thyristor phase - controlled rectifying power supply .We can say, the switch power supply technique is the essential technique which wins small electric power transformation of the power direct current to equip currently. This text described the development of switch power supply first, to a few kinds which appear currently typical model of the switch power supply technique made to induce summary and analysis comparison, pointing out the development trend of the technical development condition of the switch power supply and switch power supply product on this foundation.And introduce the switch power supplys phylogeny,application, main electric circuit of power supply and controled a method. The design adopted PWM, the whole bridgeses commutated, lock protection etc. technique, applied control the chip UC3842 to be used as PWM control chip, the transformer adoprt adopt pile circle, improve the choice of the electric circuit, make the electric circuit be able to attain need basic request in the meantime, try hard for stability, efficiently. Key words：Switch power supply，topology，transform，Forward III 目录目录 摘要 . I Abstract . II 目录 . III 1 绪论 . 1 1.1 引言 . 1 1.2 开关电源的发展历史 . 1 1.2.1 国外发展历史 . 1 1.2.2 国内发展状况 . 2 1.3 目前需要克服的困难 . 2 1.4 开关电源的发展趋势 . 3 1.5 本文的设计要求 . 4 2 开关电源的工作原理 . 6 2.1 开关电源的基本构成 . 6 2.2 开关电源常用的拓扑结构分析 . 6 2.2.1 降压型 . 6 2.2.2 升压型 . 7 2.2.3 升降压型 . 8 2.2.4 反激式 . 9 2.2.5 正激式 . 11 2.2.6 推挽式 . 12 2.3 拓扑结构的确定 . 13 3. 基于 UC3842 的开关电源的设计与实现 . 14 3.1 开关电源电路的设计 . 14 3.1.1 开关电源电路的总体简介 .