Optimal design of GaN HEMT based high efficiency LLC converter

Abstract

LLC converter has the advantages of large range voltage regulation ability, zero voltage switch (ZVS), magnetic isolation and is prevalent in data center power supply. As the increasing of power consumption in data center, the power density and efficiency of LLC converter is being pushed higher and higher. With the adoption of wide bandgap gallium nitride high electron mobility transistor (GaN HEMT), power device switching loss and conduction loss have been largely decreased and the switching frequency can be increased significantly. Thus the efficiency and power density promotion of LLC converter mainly dependent on the optimal design of deadtime and resonant parameters. In this paper, the ZVS working frequency boundary and the analytical calculation equations of both resonant and rectifier currents with the consideration of deadtime are deduced first, based on which a GaN device based LLC converter optimal design method is proposed with the realization of high efficiency and ZVS under wide input voltage range. An accurate GaN HEMT device model based LLC virtual prototype has been further constructed to verify the correctness of the proposed optimal design method. At last, the correctness of the proposed design method has been verified by experiment results.