Robust control of PWM power amplifier by approximate 2-degree-of-freedom digital controller with mode switching

Robust PWM power amplifiers whose transient response characteristics do not deteriorate against an extensive load change and/or direct-current power-supply voltage change are needed. In this paper, a digital robust controller with mode switching for PWM power amplifiers which can satisfy such demands is proposed. First, a nominal model of PWM power amplifiers which consists of a PWM signal generating part, an electric power conversion part and a LC filter is derived from the linear approximation. The controlled objective is described by the discrete-time systems with consideration of the input dead time. It is shown that a digital controller can be designed by the same way as the previously proposed digital controller and then the load range spreads more by mode switching. A DSP is implemented to the digital controller with mode switching. It is shown from an experiment that mode-switched digital controllers are realizable.