A Delta-Sigma Modulator with UPWM Quantizer for Digital Audio Class-D Amplifier

Abstract

In this paper, a delta-sigma modulator (DSM) with uniform pulse-width modulation (UPWM) quantizer for digital audio class-D power amplifier is presented. A pole-moving approach for Inverse Chebyshev filters is proposed to stabilize the UPWM modulator as well as improve its performance. The characteristics of the saw-tooth carrier for UPWM quantizer is explored to reduce the output switching rate and the power loss in class-D amplifier in the pulse-density modulation (PDM) case. In the presented single-loop sixth-order UPWM modulator with the ameliorated saw-tooth carrier, an SNDR of 120 dB within 20-kHz bandwidth can be achieved under full-scale signal input. With the proposed schemes, the highest transfer efficiency of 1 for digital class-D amplifier can also be obtained.