LLC Resonant Converter based on Variable Inductor without Auxiliary Switches

Abstract:
The LLC resonant converter is widely used in various applications and industries such as data centers and electric vehicles (EV) due to its soft-switching and wide output voltage characteristics. However, under light load conditions, the LLC resonant converter operates at a very high switching frequency to step down the output voltage. This paper proposes an LLC resonant converter with a variable inductor without auxiliary switches and explains an efficient parameter design method. Based on the proposed winding method, the resonant inductance automatically varies according to the magnitude of the load current, and the proposed parameter design method enables not only a reduction in switching frequency but also a reduction in losses. A 2-kW simulation model was developed and validated through simulation.