Improvement of Efficiency in Bidirectional DC-DC Converter with Dual Active Bridge Using GaN-HEMT

A prototype bi-directional isolated DC-DC converter with 3.6 kW output power, operating at the maximum frequency of 400 kHz, using GaN-HEMTs was developed and evaluated. Typical circuits for bidirectional isolated DC-DC converters are the LLC resonant converter and the dual active bridge (DAB), both of which have the disadvantage of low efficiency at light loads. In this study, loss reduction by zero-voltage switching using the excitation current of the transformer and natural commutation was performed for DAB. As a result of the efficiency comparison between LLC resonant converter and DAB under the same components and input/output conditions, higher efficiency was obtained in DAB under most conditions. The maximum efficiency was 98.6%.