The robust control of PWM power amplifier by the approximate 2-degree-of-freedom digital integral-type control system

A robust PWM power amplifier whose transient response characteristics do not deteriorate against an extensive load change and/or direct-current power-supply voltage change is needed. In this paper, a method for designing a digital robust controller for PWM power amplifier 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 an 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 in almost the same way as the previously proposed analog controller and then a 2-degree-of-freedom digital robust systems are constituted. The LC filter and the digital controller which satisfy the design specifications are determined by the proposed design method. A DSP is implemented for the digital controller obtained here. It is shown from an experiment that sufficiently robust digital control systems are realizable.