文档介绍：I 摘要电力电子及开关电源技术因应用需求不断向前发展,新技术的出现又会使许多应用产品更新换代,还会开拓更多更新的应用领域。要求电子元件体积更小,耗能更低。开关电源作为电子设备中不可或缺的组成部分也在不断的改进,高频化、高效率、高可靠、低耗、低噪声、抗干扰和模块化等,成了开关电源的发展方向,这也标志着这些技术将不断地发展而变得越来越成熟和稳定,同时实现高效率用电和高品质用电的相互结合。脉宽调制器 SG3525 具有欠压锁定、系统故障关闭、软起动、延时 PW M 驱动等功能,因而得到广泛应用。本设计介绍了一种基于 SG3525 的半桥式开关电源变换器, 对其各电路工作原理进行了分析,并设计了过流保护电路。为了提高效率,辅助电源采用了 UC3843 为主控芯片的反激变换器。为了减低输入电磁干扰,输入端设置了 EMI 滤波电路。对各参数进行了计算,通过实物制作与调试证明了方案的可行性。该电源结构简单,思路清晰,运行稳定性好,有效降低了成本。关键词半桥 SG3525 过流保护 II Abstract Technology for power electronics and switching power supply is going ahead continuously in practice . The emergence of new technology will make replacement in many application products as well as open up more and more new fields . At the same ponents are required to have the smaller volume and lower losses , as an important parts of electronic devices power supply is getting some improvements , for high-frequency , for high efficiency , for high reliability , for low losses , for small noise , for anti-interference , for module and so on. These are ing a development direction for power supply , which show that these technologies will e more mature and stable , it will achieve binability between high-efficiency and high quality to use electric energy . The pulse width modulator SG3525 has been used in various areas for its functions such as locking for the lack of pressure, closing system fault, soft starting, delaying PWM drive and so on. This design introduces a half-bridge based on SG3525 switch power converte - r, the working principle of the circuit is analyzed and designed over-current protec - tion circuit. In order to improve efficiency, auxiliary power for the main chip used UC3843 flyback converter. To reduce the input of ic interference, EMI input filter circuit is set. each parameter was calculated, through the producti - on missioning physical proof the feasibility of the project. The power structure is simple, clear, running stability, and effectively reducing the cost of it. Key words : half-bridge SG3525 ove