Flying-Capacitor Linear Amplifier With Capacitor Voltage Balancing for High-Efficiency and Low Distortion

Abstract

This article presents a flying-capacitor linear amplifier (FCLA) that achieves high efficiency, low harmonic distortion, and low electromagnetic interference (EMI). A conventional class-B linear amplifier cannot be used in power conversion applications, because the power loss generated in active-state MOSFETs is high compared with the loss generated in switching operations. In the proposed FCLA, multiple series-connected MOSFETs are used, and only one MOSFET operates in the active state at a time. Thus, the power loss generated in the MOSFETs can be reduced, and the FCLA can achieve high efficiency without performing the switching operation. In this study, the features of the FCLA and conventional linear amplifiers are theoretically compared and evaluated. Moreover, a voltage balancing control for flying capacitors is proposed and verified through simulations and experiments. It is demonstrated that the prototype 12-series FCLA achieves over 89% efficiency and generates low harmonics and low EMI. The proposed configuration is useful for increasing the number of series MOSFETs, and it contributes to realizing a power converter with advantages such as low harmonic distortion, low EMI, and high efficiency.