Development of a class-D audio amplifier with switch-mode rectifier front-end and its waveform control

Abstract

This study presents the development of a switch-mode class-D audio power amplifier and its robust waveform control. First, a pulse-width modulated inverter is designed and implemented to have successful high-frequency switching operation. Then a robust two degree-of-freedom control scheme is proposed to let the inverter-fed loudspeaker possess close and robust voltage arbitrary waveform tracking characteristics within wide audio frequency range. The waveform tracking performance of the developed inverter is evaluated under resistor load and loudspeaker load with the commands of varying-frequency sinewave, random signal and actual music signals. Finally, a front-end flyback switch-mode rectifier (SMR) is developed and employed to establish well-regulated and boostable DC-link voltage for the followed inverter. Significant improved inverter output waveform tracking performance can be obtained. Meanwhile, good line drawn power quality is achieved. Some experimental results are provided to demonstrate the performance of the whole SMR-fed switch-mode audio system.