The dynamic response of PWM DC-DC converters with input filters

The authors develop computer-aided procedures for the analysis and design of input filters of pulse-width-modulated (PWM) DC-DC converters operating in voltage or current mode. The proposed methodology is based on the switched inductor model (SIM), which is an equivalent circuit approach for modeling and simulation of switch mode systems. The method is compatible with all versions of SPICE-derived electronic circuit simulators. Following a brief discussion of the modeling aspect, the authors examine the question of instability due to the input filters. It is shown that this issue can be easily studied by examining the small signal loop-gain function. Furthermore, the small signal analysis which includes the effect of the filter can then be used to optimize the feedback network to meet desired closed-loop dynamic responses