A Modified Gain Model and the Corresponding Design Method for an LLC Resonant Converter

In this paper, a modified gain model and the corresponding design method for an LLC resonant converter are proposed. To derive the gain model, two important factors-resonant factor and load factor are considered and discussed in detail by combining time domain and frequency domain. Compared with fundamental harmonic approximation (FHA) method, the accuracy of the gain model is highly improved. Referring to the modified gain model, the corresponding design method is also obtained that can inherit conciseness and practicability of the FHA method. Thus, the design method can be used to replace the FHA method in practical design procedures. Finally, the simulation results are given and a prototype of the LLC resonant converter used for power electronic traction transformer is built to verify the accuracy and validity of the proposed gain model and the corresponding design method.