An LLC Converter Based on SiC MOSFETs and Minimized-leakage-inductance Planar Transformer

Wide band gap devices and planar transformers help improving the power density of LLC converters. However, the parasitic parameters of planar transformer make the optimal operating point of the converter offset and reduce the efficiency. In this paper, a SiC MOSFETs based LLC resonant converter with an optimized planar transformer is modeled, analyzed and verified by experiments. The leakage inductance of the proposed winding structure is only 50% of the fully interleaved structure. The proposed converter is more ideal with more accurate resonant frequency and gain. The measured resonant frequency is 99.67 kHz, which is only 0.33% lower than the design value of 100 kHz. With the lower loss, the more ideal transformer increases the efficiency of LLC converter by 3%. Furthermore, the gain of the LLC converter at resonant frequency is higher and the gain-frequency and gain-load curves are more ideal.