An optimal design of the LLC resonant converter based on peak gain estimation

The LLC resonant converter topology is widely used in DC-DC converter applications for its advantage in achieving high efficiency and high power density. However, due to the complexity in the analysis, the converter lacks a clear design method to help selecting the optimal circuit parameters. In this paper, an optimal design method is developed based on the operation mode analysis and peak gain estimation. With the optimal design, the converter can minimize the conduction loss while maintaining the required gain range. A 400W, 400V output and 25V-38V input LLC converter is built using the proposed method, which achieves above 98% peak efficiency. As a comparison, the conventional searching method is used to reselect the LLC components for the same specifications, and the experiments show that the optimal design has better performance.