摘 要: 由于电力电子技术在近几十年不断取得进步和发展，开关电源的性能不断得到优化和提升。DC/DC直流变换器作为开关电源应用方面的重要种类之一，正在向着方便携带、效率高、耗能低的方向快速发展着，尤其是在便携式电子产品中的大量应用发挥着不可或缺的作用。57722

    针对直流转直流（DC/DC）变换的控制电路，本文采用SG3525芯片为基础的脉冲宽度控制电路来完成功率MOSFET的驱动。通过控制SG3525输出的PWM波形占空比大小来设定主电路中开关管的通断时间，从而产生相应的输出电压值。针对该设计方案的主电路，选择升压型DC/DC直流变换电路，选择IGBT作为主电路中的开关管，能较精确的控制电流通断时间，输出品质较好的电压。在完成升压型DC/DC直流变换器主体设计后，设计了相关的隔离驱动电路、电容滤波电路和保护电路，从而使本方案设计的预期效果得到了保证。通过仿真验证证明，本方案是切实可行的，所得PWM波形占空比良好，所含谐波也较少，直流电压的转换效率很高。

毕业论文关键词: 开关电源 , DC/DC变换器 , SG3525 , PWM

Abstract : Due to the fast advancement and development of the power electronic technology in recent years, the performance of switching power supply is optimized and advanced in a obvious speed. As one of the important types of switching power supply applications, DC/DC DC converter is being developed rapidly toward high efficiency and low consumption, especially playing an indispensable role in a large number of applications in portable electronics.

  For the control circuit of DC/DC converter, the chip of SG3525 is adopted to drive the power MOSFET in this thesis, which is based on the control of pulse width circuit. By controlling the output of SG3525, the duty ratio of PWM is set by the switching on and off time of the main circuit, producing the corresponding outputting voltage value. According to the designation of main circuit, the booster DC/DC DC conversion circuit is chosen, IGBT is chosen as the switch tube of the main circuit, which can be more precise in controlling the electric current time, and better voltage output quality can be obtained. Upon the completion of the main circuit for the booster DC/DC DC converter, the related separation filter circuit, protecting circuit, driving circuit are also designed. Simulation results show that the expected results obtained by the scheme design is feasible, the PWM duty ratio is good, the content of harmonic is less, and the DC voltage conversion efficiency is higher.

Keywords：Switching Power Supply , DC/DC Transformation , SG3525 , PWM

目  录

1 绪论 3

1.1 课题研究背景和意义 3

1.2 DC/DC变换器发展趋势 3

1.3 本文主要内容 6

2 DC/DC直流变换器介绍 6

2.1 DC/DC变换器基本原理 6

2.2 DC/DC直流变换器类型 6

2.3 DC/DC直流变换器开关控制方式 10

2.4 PWM控制的反馈模式 13

3 升压型DC/DC直流变换器设计方案 14

3.1 SG3525控制电路基本原理 14

3.2 升压型DC/DC直流变换器设计方案 16

4 升压型DC/DC直流变换器硬件电路设计 17

4.1 主电路设计 17

4.2 控制电路设计