一种Buck输出纹波比的简化计算及设计方法

Buck变换器是一种高效的DC-DC降压开关电路，其输出的直流电压受到纹波干扰。纹波比是一个重要的性能指标，它受开关频率、滤波电感电容、占空比和负载电流（或负载电阻）等参数共同影响，不易精确计算。先构建一种与Buck变换器（电感电流连续）完全等效的理想电路拓扑；分析此电路的频率响应特性后得到电路的稳态输出；进一步的纹波理论计算及仿真分析表明，电路输出纹波比的计算完全可以由基波纹波比代替。基于上述简化纹波比计算的结论，又提出了一种设计滤波元件L、C参数的方法，并将这种方法运用于实例设计中，最后的仿真及实验数据都说明采用此方法能有效地计算出满足纹波比指标要求的L、C参数范围。

Simplified Calculation and Design Method for Ripple Ratio of Buck Output

A Buck converter is a kind of highly efficient DC-DC step-down switching circuit, whose output DC vol-tage is disturbed by ripple waves. The ripple ratio is an important performance index, which is affected by factors such as switching frequency, inductance capacitance, duty ratio and load current(load resistance), and it is not easy to calculate accurately. An ideal circuit topology which is completely equivalent to a buck converter(in continuous con-duction mode) is constructed at first. Then, the circuit''s frequency response characteristics are analyzed, and its steady-state output is obtained. Furthermore, theoretical calculations based on the ripple theory and simulation analysis show that the ripple ratio of fundamental wave can be used to replace the total ripple ratio of the circuit output completely. Based on the conclusions from the above simplified ripple calculations, a design method for the L and C parameters of filter elements is also put forward and further applied to a case design. At last, simulation and experimental data of a prototype show that this method can be used to effectively calculate the parameter ranges of L and C that satisfy the requirement of the ripple ratio index.