PWM开关DC-DC变换器的低频波动

为了揭示PWM开关变换器输出电压出现低频波动的规律，基于电感电流和输出电压包络的波动频率远低于变换器的开关频率的假设，建立了变换器中电感电流和输出电压包络的微分方程，并在s域进行分析，得出了变换器的闭环输出—输入电压传递函数，采用胡尔维茨稳定判据得出了变换器的稳定条件，分析结果表明：反馈环节的滞后是造成变换器输出电压出现低频波动的原因。采用零极点分析的方法确定了变换器低频波动的频率，利用变换器拓扑结构的约束关系，得出了变换器低频波动的幅值。采用SPICE仿真和实验的方法验证了理论分析结果的正确性。

LOW FREQUENCY RIPPLE BEHAVIOR OF PWM SWITCHING DC-DC CONVERTERS

In order to investigate the low-frequency ripple behavior of output voltage of PWM switching DC-DC converters, differential equations for inductor current profile and output voltage profile are established. The equations are based on the assumption that the frequency of inductor current profile and output voltage profile are much lower than the switching frequency of the converter. The converter is analyzed in s filed. The closed loop output to input voltage transfer function is deduced. The stability requirement is obtained based on Hurwitz Stability Criterion. It is pointed out that the delay in the feed back loop leads to the low-frequency ripple in the output voltage. The frequency of the low frequency ripple voltage is determined by using zero-pole analysis method. The amplitude of the low frequency ripple voltage is obtained according to the topology restrain of the converter. The proposed approach is verified by SPICE simulation and experiment results.