基于SG3525的半桥式开关电源变换器

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PWM 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

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 time components 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 becoming a development direction for power supply，which show that these technologies will become more mature and stable，it will achieve the combinability 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 electromagnetic interference, EMI input filter circuit is set. each parameter was calculated, through the producti -on and commissioning 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 overcurrent protection

目录

摘要..................................................................................................................... I Abstract ................................................................................................................. II 第1章绪论 . (1)

1.1 本课题研究的目的和意义 (1)

1.2 国内外技术发展概况 (1)

1.3 21世纪开关电源的发展展望 (2)

1.4 本设计的主要内容和目标 (4)

1.5 方案论证与总体设计 (4)

1.5.1 方案论证 (4)

1.5.2 硬件总体结构设计 (6)

第2章半桥变换器拓扑分析 (7)

2.1 半桥变换器工作原理 (7)

2.2 半桥变换器的漏感问题 (8)

第3章控制芯片的介绍 (9)

3.1 SG3525工作特性分析 (9)

3.2 UC3843工作原理分析 (12)

第4章电路设计 (16)

4.1 EMI滤波电路设计 (16)

4.2 整流滤波电路设计 (18)

4.3 半桥电路设计 (19)

4.4 控制电路分析 (19)

4.5 驱动电路与过电流保护电路原理分析 (20)

4.5.1 驱动电路设计 (20)

4.5.2 过电流保护电路分析 (21)

4.6 辅助电源设计分析 (21)

第5章参数计算及主要元器件选择 (23)