Performance optimization of LLC converter based on double loop control

In order to improve the regulation capability of the wide range output voltage and light load efficiency, this paper proposed two level control strategy. Asymmetrical Pulse Width Modulation(APWM) was used in the LLC series resonance with voltage double rectifier and a feedback controller was added to get the proper crossover frequency and enough relative stability. Phase-locked loop control(PLL) was used to track the resonant frequency. In addition, considering the high switching frequency of the secondary leakage inductance will affect the input and output voltage gain, this paper added secondary leakage inductance to the model to reduce the reverse blocking voltage of rectifier diode, which can improve the accuracy of modeling. Simulation and experiment have verified the correctness of the theoretical analysis and the feasibility of the control strategy.