Low distortion digital pulse width modulation for audio class-D amplifier

Abstract

A pulse width modulation scheme for a high fidelity digital audio amplifier is presented. The uniform PWM is used to utilize the over sampling technology, but the UPWM causes harmonic distortion. The harmonic distortion components at the PWM output are estimated using the derivatives of the input signal and cancelled at the input of the delta-sigma modulator. The output signal of the delta-sigma modulator is coarsely quantized with shaped noise and fed to the pulse width modulator. A simulation result for a dual tone test is presented to illustrate the effectiveness of the proposed method.