Ripple feedback filter suitable for analog/digital mixed-mode audio amplifier for improved efficiency and stability

摘要

A new ripple feedback filter is presented for Analog/Digital mixed-mode amplifier (MMA) among audio applications. MMA is composed of two amplifiers: one is analog amplifier responsible for high fidelity and the other is digital switching amplifier in charge of high efficiency. To improve both total harmonic distortion (THD) and efficiency, passive RLC filter is needed at +-he output side of the digital switching amplifier. Conventional filter, however, causes phase delay, which worsens current loop stability and makes the normal operation of MMA impossible. Ripple feedback filter is newly suggested to solve this problem, obtaining excellent efficiency and low THD.