An Optimal Design Scheme of Intermediate Bus Voltage for two-stage LLC Resonant Converter Based on SiC MOSFET

The two-stage LLC resonant converter has numerous superiorities in wide voltage input occasions. The fixed-frequency operating state of LLC converter is conducive to the design of magnetic components and a high efficiency could be achieved. In such a two-stage converter system, the optimal design of the intermediate bus voltage is of great significance. This parameter not only determines the working voltage of tubes, but also affects the efficiency of converter. To optimize the overall performance of the converter, a majorized design scheme of intermediate bus voltage is proposed in this paper. The optimal point can be obtained via building and solving the mathematical model. Finally, a 1-kW converter with the DC-link voltage of 70~120V and the output voltage of 28V is built. The peak efficiency of the prototype is 97.3%.