Methods for Solving Problems in the Feedback System using the PWM (Pulse Width Modulation) Power Amplifier

A feedback system using the PWM power amplifier has three major problems: time delay; nonlinearity; and noise. In this paper, we discuss the time delay problem that causes narrowing bandwidth of the feedback system, and the nonlinearity problem that causes the difficulties of optimization and instability of the feedback system. And, we propose the solutions for both of them. For the time delay problem, we propose improved PWM method carrying its information both at the rising edge and the falling edge. For the nonlinearity problem, we propose the PWM gain controller to cancel the nonlinearity. The technologies presented here are helpful not only for improving the performance of the PWM feedback loop, but also for simplifying the de-modulation LC filter.