Digital Pulse Width Modulator: Low-power, Low-Distortion, for Digital Class D Amplifier

We describe the design of a micropower digital pulsewidth modulator (PWM) for a hearing instrument Class D amplifier. The PWM embodies a novel delta- compensation sampling process and a novel pulse generator.The delta-compensation sampling process is sampled at the same low rate as reported algorithmic sampling processes and it features a similar low total harmonic distortion (THD). Its arithmetic computation is however, substantially simplified. We analytically derive the double Fourier series expression and show that the THD is low.The pulse generator is based on a hybrid 9-b counter 3-b tapped-delay-line. We investigate the compromise between the different design parameters that affect its power dissipation and THD. The complete proposed PWM features a simple circuit implementation, micropower low voltage operation, low sampling rate and low harmonic distortion, thereby rendering it suitable for a practical digital hearing instrument.

Huiyun Li received the Ph.D degree from University of Cambridge in 2006. She is now with Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, China. Gwee Bah Hwee received the MEng and PhD degrees from Nanyang Technological University, Singapore in 1992 and 1998. He is with Nanyang Technological University since 1999.