Robust digital control of PWM power amplifier by approximate 2-degree-of-freedom system with bumpless 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 bumpless mode switching for PWM power amplifiers, which can satisfy such demands, is proposed. First, a nominal model of PWM power amplifiers which consist of a PWM signal generating part, an electric power conversion part and an LC filter is derived from the linear approximation. The controlled object is described by the discrete-time system with consideration of the input dead time. It is shown that a digital controller can be designed in the same way as the previously proposed digital controller and then the load range spreads more by bumpless mode switching. A DSP is implemented to the digital controller with bumpless mode switching. It is demonstrated from an experiment that a mode-switched digital controller is realizable.