Control and performance of a class d audio power converter under sliding-mode control with variable hysteretic bands

A hysteretic controller is used to control a class D amplifier and the performance is compared with that of an open-loop PWM class D amplifier. The effect of control loop gains on THD is explored, as well as the effect of the hysteresis bandwidth. Investigation into the dependency of the switching frequency on the input reference frequency and amplitude is also performed. Additionally, the output spectrums of the amplifiers are simulated and compared with the expected results from the analytical treatment of the spectrum of PWM signals. The proposed amplifier has superior THD over most of the audio range when compared to that of a typical open-loop PWM class D amplifier, and the switching frequency is lower in all cases.