Flying-capacitor linear amplifier to realize both high-efficiency and low distortion for power conversion applications requiring high-quality waveforms

This paper proposes Flying-Capacitor Linear Amplifier (FCLA) realizing high-efficiency, low harmonic distortion, and low electromagnetic interferences. Generally, the power loss generated in the active-state MOSFETs is very large, and the conventional class-B linear amplifier is not used on the power conversion applications because both the MOSFETs of the class-B linear amplifier mostly operate in active-state region. In the proposed FCLA, multiple series MOSFETs are connected and only one MOSFET operates as the active-state at the same moment. Thus, the power loss generated in the MOSFETs can be reduced and FCLA achieves high efficiency without the switching operation. In this paper, characteristics of the FCLA and conventional linear amplifiers are theoretically compared and evaluated. As a result of the theoretical calculation, it is clarified that the FCLA has higher efficiency than the conventional linear amplifiers. Finally, experimental waveforms and efficiencies of prototype 4-series, 6-series, and 12-series FCLAs are shown. The efficiency of 88.9% is measured at 57.7 W output in 12-series FCLA.