摘要：在信息和数字时代，所有电子设备都需要有一个稳定可靠的电源来提供能量。因此，开关电源的发展对于国家的发展和建设有着极其重要得作用，经过几十年的发展，开关电源方面的技术已经有了长足得发展。为了小型化，高效率可靠的开关电源，全世界的工程师做出了不懈的努力。随着电力电子技术的发展，开关电源的应用越来越广泛。开关电源以其小型、轻量和高效的特点，被广泛地应用于各种电器设备和系统中，其性能的优劣直接关系到整个系统功能的实现。开关稳压电源有多种类型，其中单端反激式开关电源由于具有线路简单、所需要的元器件少、能够提供多路隔离输出、体积小、成本低等优点，在中小功率场合得到了广泛的应用。

传统的反激式开关电源一般由PWM控制芯片和功率开关管组成，PWM芯片控制环路设计复杂，功率开关管有时需要外加驱动电路。高效率与小型化在一定程度上是互相限制的，因为实现高效率会要求电路有相当的复杂度，大量的器件对小型化十分不利。在开关电源设计初期，采用的都是分立元件，集成度很低，大部分电路只能在PCB板上实现，极大的限制了小型化实现的可能。而且大量器件暴露在外，也影响了系统的稳定性。近年来，为了实现更高的效率和更小的体积，开关电源的工作频率有了很大的提高。高工作频率能够减小外围电感和电容尺寸的大小，从而减小系统的体积。另外，反激变压器的设计也是一个难点，其往往导致电源设计周期延长。反激变换器中的变压器与其他开关电源变压器不同，它本质上是一个储能电感，因此，反激变换器中的变压器设计具有一些独特的地方。

本文对一种5V1A反激变换器开关电源进行了深入研究，建立了完整的仿真模型并成功运行；设计了电气原理图，并绘制了PCB板。

关键词：反激式变换器   高频变压器   开关电源    LTSpice                      

Design of switching power supply for 5V1A Flyback converter

Abstract：With the development of power electronics technology, the application of switching power supply is more and more extensive. Switching power supply, with its small size, light weight and high efficiency, is widely used in various electrical equipment and systems. There are different types of switching power supply, including single-ended flyback switch power supply. Because of the simple lines, can provide the multiple output isolation, and its advantages of simple design, small number of components, small size and low cost, the flyback converter power supply is widely used in low power applications area.

Traditional flyback switching power supply is generally composed of PWM control chip and power switch tube, PWM chip control loop design complex, power switch devices sometimes require additional driver circuit. High efficiency and miniaturization are limited to a certain extent, because high efficiency requires considerable complexity of the circuit, and a large number of devices are detrimental to miniaturization. At the initial stage of switching power supply design, discrete components are adopted and the integration degree is very low. Most circuits can only be realized on the PCB board, which greatly limits the possibility of miniaturization. Moreover, a large number of devices are exposed, which affects the stability of the system. In recent years, in order to achieve higher efficiency and smaller volume, the working frequency of switching power has been greatly improved. High operating frequency can reduce the size of the peripheral inductor and capacitance, thus reducing the volume of the system.In addition, the design of inverter is also a difficult problem, which often leads to the extension of the design period of power supply. With the advent of a new generation of power management IC, many of the above problems have been well solved.