A Novel Feedforward Strategy for the Charge-Modulated LLC Resonant Converter

A novel feedforward strategy for the charge-modulated LLC resonant converter is proposed in this paper. Different from the traditional charge modulation, the ideal input charge over a half switching cycle is predicted in real time and feedforwarded to the linear controller. Thus, once the transient state occurs, the input charge can be regulated to the ideal value in instant so as to suppress the transient process. In other word, the proposed feedforward strategy can realize nonlinear performance during the transient process and also predict stable control input for the new steady state, combining the benefit of both the simplified optimal trajectory control and the pulse-frequency-modulation-based feedforward control. The expression of the predicted input charge only requires the DC signal, which reduce the computational burden and can be implemented with low-cost micro-control unit. The predicted input charge shows good accordance with the simulation results. Experiments are carried out to validate the proposed feedforward strategy.