Use of Sliding-Mode Modulation in Switch-Mode Power Amplification

This paper presents a recently developed feedback modulation scheme called sliding-mode modulation. Sliding-mode modulation, operating in sliding mode, simultaneously minimizes the accumulated quantization error and in-band modulation error while converting a continuous input signal into a coarsely quantized signal. With these minimization mechanisms, the modulator exhibits simple tractable behavior in the sliding mode and high in-band linearity in signal conversion. These two distinct properties make sliding-mode modulation an attractive substitute for other modulation schemes such as pulsewidth modulation and sigma-delta modulation. A simple method is presented for designing sliding-mode modulators. Moreover, a class-D audio power amplifier with three-level sliding-mode modulation is designed to demonstrate the practicality and superiority of this modulation technique.

I. Introduction

The Term sliding-mode modulation denotes the feedback modulation in sliding mode that converts a band-limited input signal into a coarsely quantized signal while preserving the information of the input signal. The sliding mode is an operating mode that is intrinsic to a large group of relay feedback systems [1], single-bit delta modulators [2], and single-bit sigma–delta modulators [3]. A recent attempt to apply the sliding mode concept to design novel multibit modulators has been made elsewhere [3], [4]. The sliding-mode modulators exhibit tractable linear behavior in the sliding mode; therefore, they can exactly be analyzed and designed. Most important, with proper feedback filtering, the sliding-mode modulators show high in-band linearity with noise and distortion eliminated.