One-cycle-averaging for digital PWM control system design

Pulse-width modulation (PWM) is a widely used strategy for operating switch controlled systems. A model for PWM systems is reported which provides the discrete-time response of the one-cycle-average value of any signal in the system. The model typically has unstable zero dynamics, as well as a nonlinear dependence on the duty ratio input. Using scheduled output redefinition, an approximate design model is derived which has stable zero dynamics. A controller based on discrete-time input-output linearization is then developed using this approximate design model. Although this approach leads to approximate rather than perfect output tracking, it guarantees internal stability.