Ultra Low EMI and THD+N Multi-Level Class-D

Abstract

This paper is about a multi-level PWM class-D audio amplifier. The recent trend in audio amplifiers is increasing output power for louder sound and more channels for better sound effects. This typically results in EMI problems and lower efficiency. Instead of a simple two-level buck power topology, a multi-level topology was proposed to solve both the EMI and low efficiency problems. However, the linearity of the amplifier is reduced by adopting a multi-level topology rather than a two-level topology. Level shifted-PWM was utilized in a prior Maxim integrated structure to overcome the low linearity problem. In this paper, a very effective and simple Folded-PWM architecture is proposed, and the new modulation scheme shows better linearity, THD+N, and performance than LSPWM. The FPWM is expected to be used commercially, since it has super performance.