Investigation of Time Domain Design of Digital Controllers for PWM Converters

Abstract

A design method for digital controller of PWM DC-DC converters was developed, tested by simulations and verified experimentally. The proposed approach is based on the fact that the closed loop response of a digitally controlled system is largely determined by the first few samples of the compensator. This concept is used to fit a digital PID template to the desired response. The proposed controller design method is carried out in the time domain and thus, bypasses errors related to continuous o discrete domain transformation and discretization. A digital PID controller for a Buck type converter was implemented experimentally on a TMS320LF2407 DSP core. The measured closed loop attributes were 3.5KHz bandwidth and phase margin of 40°. Good agreement was found between the design goals and the experimentally determined response.