复合控制型低纹波PWM AC/DC-DC变换器

在PWM AC／DC-DC变换器中,通常采用大电容滤除前级整流产生的纹波。但在某些应用场合,滤波电容不能太大。如果只用较小的电容滤波,变换器输出电压的纹波较大。本文提出了前馈及局部负反馈控制方案,即利用变换器直流中间环节的纹波移相控制芯片UC3875的移相角,使输出电压产生与采用这种方式前反相的纹波,调节这种纹波的幅度就可以减小输出电压纹波,在此基础上,本文增加了局部负反馈环节,进一步降低纹波。仿真和实验结果表明了方案的可行性。

Design of Compound Control and Low Ripple PWM AC/DC-DC Converter

In PWM AC/DC-DC converter, the capacitance usually used to filter the ripple produced by preceding uncontrolled recitfication is great. But in some application occasion, the capacitance can not be too large. When it is small, the output voltage ripple is larger. An approach of feedforward and local-negative feedback is brought forward. The medium ripple of converter is applied to control the phase shift angle of phase shift control IC - UC3875.By this method, the output voltage ripple is reverse as before, and the output voltage ripple is diminished by regulate the ripple magnitude. The local-negative feedback loop is used to reduce ripple. The results of simulation and experiment have proved the feasibility of the means.