Optimal Design of Resonant Network for CLLC Resonant Converter

CLLC converter is widely used due to its bidirectional symmetry, high efficiency, and low reactive power. In the resonant network, the design of the inductance ratio (resonant inductance L
r
/magnetizing inductance L
m
) determines ZVS realization, circulation loss, and dv/dt. The existing L
r
/L
m
method only considers the realization of ZVS. And it can’t give the precise boundary of ZVS because there are too many assumptions. As a result, the existing design method cannot give an optimal value. This paper proposes an optimal design method for L
r
/L
m
based on CLLC resonant converter. It can reduce circulation loss and dv/dt while ensuring soft-switching. And this method gives a precise boundary of ZVS by establishing a dead zone model. By using this, an optimal region of L
r
/L
m
can be given. Finally, a 4kW, 500kHz bidirectional CLLC platform is designed based on GaN Hemts devices. The experiment verifies the precision of the proposed optimal design method.