FPGA based D-PLL control technique of CLL resonant converter for EV battery chargers

In this paper, FPGA based Digital Phase Locked Loop (D-PLL) control technique is applied to the CLL resonant converter for Electric Vehicle (EV) battery charger applications. In order to improve charging efficiency, switching losses must be reduced to have a maximum energy transfer among the variable converter components. Also, fast and secure battery charging requires controlling voltage and current values at the battery terminals. The presented digital phase locked loop control technique is implemented under ZVS-ZCS conditions with variable load and variable input voltages. The designed dc/dc resonant converter, fed by a power-factor-corrector (PFC) with 100-150 V output, provides 48 V / 15 A at 720 W maximum power. At the same time, the battery constant voltage (CV) and current (CC) regulation are realized from PFC with a variable dc link. The application results show that ZVS-ZCS are maintained with input voltage and current in phase under different input voltage and output load conditions.