Proposal of Switching Power Amplifier Using Small-Capacity Linear Amplifier and LC Filter

摘要

High efficiency and low noise in output voltage and current are required in audio-video equipment, medical apparatus, and many other applications. This paper proposes a power amplifier in which a PWM inverter is used as the main circuit. In the proposed power amplifier, a hybrid filter consisting of a simple conventional type LC filter and a small-capacity linear amplifier is connected to the inverter output. The linear amplifier is inserted in series to the filter capacitor to improve the filtering effect of the LC filter. Switching ripples and LC resonances are considerably suppressed by controlling the amplifier using the proposed method, thus implementing a low-distortion switching power amplifier. The effects of the proposal circuit are verified by simulation and experiments. As a result, the proposed circuit achieves low noise about THD = 0.68% in simulation and THD = 1.5% in experiment.