Design of a class D audio amplifier IC using sliding mode control and negative feedback

In recent years, class D audio amplifiers are becoming the most feasible solution for low-voltage low-power applications due to their high efficiency property; however, to obtain good linearity for high fidelity systems is still a challenge. This work does not require the triangular carrier signal used in conventional class D audio amplifiers. It is shown that by making use of the sliding mode (SM) control technique along with an extra local feedback loop, the design parameters of a class D audio amplifier can be selected according to the linearity requirements. These techniques are applied in the design of a class D audio amplifier to yield a single-chip low distortion audio amplifier with efficiency above 90% and THD as low as 0.08%. Experimental IC results, using a commercial 0.5-mu m CMOS technology verified the theoretical results.