Predictive charge control for LLC resonant converters

A predictive charge control method based on an LLC resonant converter is proposed in this paper. The input charge in each cycle is reflected in the change of the resonant capacitor voltage. The threshold is set to compare it with the resonant capacitor voltage to control the input charge. Based on an LLC discrete predictive model, the predictive charge control predicts the threshold of the resonant capacitor voltage to regulate the output voltage. When compared with existing control methods, the predictive charge control has the advantages of an intuitive concept, a strong robustness, a simple implementation, and a simple model. It has excellent dynamic performance under various working conditions. The resonant tank can enter the steady state within one cycle without affecting the steady-state performance of the system. Through a mode analysis, this paper analyzes the proposed predictive charge control in detail. A 500 W LLC resonant converter prototype is built to verify the proposed method. Results show that both the output voltage and the resonant tank return to the steady state without fluctuations in one cycle during the processes of input voltage change and load switching.