ABSTRACT The main characteristic of the variable inductor integrated LLC (VI‐LLC) resonant converter is to achieve voltage gain regulation with fixed switching frequency and constant duty cycle. To fully improve the performance of a VI‐LLC converter, a two‐step optimal design methodology is proposed in this paper. The optimisation goal is set as efficiency and magnetic core volume. The first step is to obtain design candidates that meet design requirements. The time‐domain model of the converter is analysed and the optimal operation mode is determined. Then, operation constraints are set to improve the performance and feasibility of design candidates. The second step is to evaluate the performance of each design candidate. The magnetic core and winding optimal design method is proposed to determine the optimal magnetic design results for each design candidate. The loss model of a VI‐LLC converter is established to evaluate the power loss of each design candidate. The optimal design candidate can be obtained by the definition of Pareto optimality. Finally, a 240 W VI‐LLC prototype is built to verify the feasibility and validity of the proposed optimal design method.
Tang et al. (Thu,) studied this question.