PIM-Discretization of Analog PWM Control for DC-DC Switching Converters

A digital PWM controller is designed to suppress the output voltage fluctuations under load changes for a buck DC-DC switching converter using the IA-PIM method, which is a digital redesign method to discretize an analog controller. Since the performance degradation due to discretization is beyond the acceptable level, the analog plant is modified by increasing the output capacitance, and the analog controller is redesigned. This redesigned analog controller is then discretized into an IA-PIM digital controller and implemented on a fixed-point microcomputer. Experiments show that, with the proposed digital controller, the amplitude of spikes in the output voltage caused by load-transients is comparable to one under the original analog controller even at the sampling frequency of 50kHz, while the system under popular Tustin's controller is unstable at this sampling frequency and has unacceptable performance even at 100kHz.