Control and Performance of New Asymmetrical Operation for Switched-Capacitor-based Resonant Converters

Abstract

This paper proposes a new asymmetrical control method for a switched-capacitor-based resonant converter consisting of two half-bridge circuits using four switching devices. While the existing control method only adjusts the switching frequency and phase-shift angle, the proposed method additionally controls the duty ratio of each half-bridge circuit independently. The proposed method makes it possible to adjust the average voltage across the switched capacitor although the resonant current has an asymmetric waveform. The proposed control method also enables to operate the SCRC at a frequency closer to the resonant frequency between the resonant inductor and the switched capacitor than the existing control method. Moreover, the switching devices in three of the four arms are turned off at their minimum current requirement for ZVS operation. Thus, it is possible to reduce the switching power loss significantly in a wide power range. A 350-kHz, 3-kW prototype is constructed and tested in this paper. The experimental result shows an improved power conversion efficiency as high as 98% even under various output voltage conditions.