Abstract
The major purposes of this thesis are to develop a switch-mode class-D power amplifier for audio system and to perform its robust waveform control. First, some basic issues are explored for facilitating the system development, these issues include structure and modeling of loudspeaker, power circuits and control schemes of class-D amplifiers, key specifications of audio system, etc. In addition, some existing commercialized class-D amplifiers are surveyed to understand their progress. Next, a switch mode pulse-width modulated inverter is designed and implemented. The power circuit and switching scheme are properly designed to let the inverter be successfully operated under switching frequency of 300kHz. Then a robust two-degree-of-freedom control (2DOFC) scheme is proposed to let the inverter-fed loudspeaker possesses close and robust voltage arbitrary waveform tracking within wide frequency range. The proposed 2DOFC scheme consists of a feedback controller, a command feedforward controller and a robust disturbance cancellation feedforward controller. Performance evaluation for the developed class-D amplifier is conducted under resistive load and physical loudspeaker load. The waveform tracking control performance is first verified experimentally at some fixed frequencies between 20Hz to 20kHz. Then further evaluations are made using the band-pass filtered random signal and the physical music signal generated from CD player. Finally, to let the developed audio system have satisfactory line drawn input power quality, a flyback switch mode rectifier (SMR) is designed and implemented. Under discontinuous current mode operation, a robust voltage controller is proposed to establish well-regulated DC-link voltage with high input drawn power quality. Some simulated and experimental results are provided to demonstrate the performance of the whole SMR-fed switch-mode audio system.