Predictive Synchronous Rectification Control Scheme for Resonant DC-DC Converters for Battery Charging and Telecom Application

Synchronous rectifier schemes for the resonant dc-dc converter significantly improve the power conversion efficiency. The predictive synchronous rectification scheme for an LCLC resonant converter for a battery charging and telecom application is proposed in this work. During converter operation, the resonant capacitor voltage is sensed through an analog to digital converter, and based on the discretized time domain equations, the turn-on and turn-off instances are precisely computed using computation and synchronous MOSFET on time predictor block for varying switching frequency of operation. The proposed predictive technique eliminates the need for current sensors, reducing overall system cost and conduction loss associated with it. The proposed predictive synchronous rectification method is tested in a 1 kW hardware prototype for varying line and load conditions. The proposed control scheme is able to track turn-on and turn-off instances precisely with a low timing error of 2% to 3% of the synchronous MOSFET ON time.