Applying Digital Technology to PWM Control-Loop Designs

This topic discusses the application of digital-control to DC/DC-switching converters and how to model the digitally controlled system. The main blocks that appear in almost every digital controller—the error ADC, the compensator, and the digital PWM engine—are discussed and used to model small-signal characteristics such as frequency response, stability criteria, the effects of quantization, as well as the impact of sampling rate and delay introduced by the digital controller to the system. This model is extended to include nonlinear gain and its benefits. Finally, a graphical user interface is introduced and demonstrated for use with the design of a two-phase synchronous-buck converter.