There is a need for robust PWM power amplifiers whose transient response characteristics do not deteriorate in the presence of extensive load variation and/or direct-current power-supply voltage variation. In this paper, a methodology is proposed for designing a digital robust controller using only voltage feedback for PWM power amplifiers which can satisfy such demands. The controlled object (PWM power amplifier) is represented by a discrete-time system with consideration of input dead-time and the conversion of current feedback to voltage feedback. First, a model matching system using only voltage (output) feedback is created for this controlled object. Next, it is shown that an approximate two-degree-of-freedom digital robust control system can be created by connecting the robust compensator obtained by approximating this model matching system. Furthermore, it is shown that a digital integral-type controller using only voltage feedback is obtained by equivalent transformation. Methods for determining the parameters of the LC filter and the controller, and a sampling time which satisfies design specifications are shown. Finally, it is verified by simulation and experiment that all the given specifications are satisfied by the proposed digital controller and that the design method with consideration of input dead-time is useful. (C) 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 86(6): 1-12, 2003; Published online in Wiley InterScience (www.interscience. wiley.com). DOI 10.1002/ecjb.10110.
