Sliding-mode quantized control of a class-D audio power amplifier

A quantized control law for a class-D audio power amplifier is presented. The control law consists of two feedback compensators and a sliding-mode quantizer. The feedback compensators are designed to stabilize the class-D amplifier and eliminate switching noise and harmonics in the audio band, while the sliding-mode quantizer converts a continuous control signal to a quantized one that serves as a switching command to an H-bridge power converter. The entire control system is operated in sliding mode. A practical simple approach to designing the compensators is presented, and a three-level class-D audio power amplifier with an LC output filter is built for verification. The experimental results show a high-quality signal reproduction with audio-band distortion and noise as low as 0.019 % for a 1 kHz test input.