A frequency controlled bidirectional synchronous rectifier converter for HEV using super-capacitor

In this paper, a control method of a bidirectional zero-voltage-switching (ZVS) DC-DC converter for HEV power system is presented. By controlling the minimum and maximum values of the inductor current, the ZVS condition is achieved. Also employing the variable frequency control with respect to the variation of the DC-link current and the super-capacitor voltage, the circulating energy loss at the light load condition is minimized. A 1.25 kW experimental hardware prototype module is built to verity the efficiency improvement, especially at the light load condition. It shows about 34% efficiency improvement compared to the fixed frequency control at the light load condition.