Six-Switch Bridge CLLC Bidirectional Converter for Energy Storage Systems

Abstract

This paper proposes a new isolated CLLC resonant converter for automotive charging and discharging applications. The input includes a full-bridge structure, and the output battery side involves six switches to realize the rectification function. On the basis of component loss and stress, this paper compares and analyzes three battery-side rectification structures: full-bridge, dual full-bridge (eight switches), and the proposed six-switch bridge architectures. First harmonic approximation analysis indicates that these three architectures have equivalent AC circuits and are thus similar in design to the traditional full-bridge structure. Moreover, the proposed topology demonstrates lower component counts while maintaining the same advantages as those of the dual full bridge, resulting in greater efficiency and lower cost. Furthermore, employing six switches on the secondary side reduces the voltage stress of every switch by half of the output; the low on-resistance power switch is used, resulting in lower conduction loss. In addition, zero-voltage-switching of all power switches in the entire power range is realized to obtain high efficiency. Finally, the proposed 1-kW CLLC resonant converter prototype is successfully constructed and tested to verify the feasibility of the converter at the peak efficiency of 97.1%.