A Commutation Overlap Period Reduction Method Expanding Buck Operating Range for a Bi-directional Isolated DC-DC Converter

Abstract

This paper proposes a bi-directional isolated DC-DC converter with an active clamp circuit and two novel control methods in the buck mode. A circulating current reduction method decreases the conduction loss. A commutation overlap period reduction method maintains the output power by expanding the maximum actual duty cycle even if the input voltage decreases. The experimental result shows that the proposed method increased the maximum output 1.5 times, without increasing the voltage applied to the low-voltage side MOSFETs under the minimum input voltage condition. A 2 kW class prototype showed a higher than 90% efficiency over a wide operating range for a greater than 20 input-output voltage ratio at 100kHz switching frequency.