A novel scheme for a bi-directional isolated DC-DC converter with a DC-link diode using reverse recovery current

A bi-directional isolated DC-DC converter using a novel circuit topology and its control method are described. The proposed circuit is based on a voltage-fed full-bridge circuit on the high-voltage side and a current-fed full-bridge circuit with an active clamp circuit on the low-voltage side. In order to make use of only MOSFETs with slow body diodes in the high-voltage full-bridge circuit to reduce the switching loss, the high-voltage side has a newly added DC-link fast recovery diode. The proposed control method, reverse recovery commutation and acceleration, recovers the reverse recovery current of the DC-link diode and stores the current in Lr, and accelerates the current for smooth boost operation so that the voltage applied to the low-voltage side MOSFETs is kept down. All nine MOSFETs can be turned on under zero-voltage switching conditions in both buck and boost modes. The results of testing under minimum input voltage conditions demonstrated that the proposed method increases the maximum output power without increasing the voltage applied to the low-voltage side MOSFETs. A 1.5-kW prototype exhibited efficiency of 94 % at maximum output power at a switching frequency of 100 kHz.