A Simplified Time-Domain Gain Model for CLLC Resonant Converter

The CLLC resonant converter is a popular bidirectional isolated dc-dc converter topology due to its ideal sinusoidal ac current through the high-frequency transformer, soft switching at a full range of loads, smaller circulation current. Since the accuracy of the gain model has a direct impact on the converter parameters design, this paper first proposed a simplified time-domain gain model for the CLLC resonant converter based on the superposition principle and the energy conservation law. Compared with the fundamental harmonic approximation (FHA) method, this gain model has higher accuracy and can be adopted with both resistance and battery load. And then, the boundary conditions between different operation modes in CLLC converter have been analyzed. Finally, the proposed time-domain gain model was verified by the simulated and experimental results of a 15 kW prototype.