Efficiency Improvement of GaN Dual-Active-Bridge DC-DC Converter with a Three-level Active Gate Driver

Abstract

Gallium nitride (GaN) high electron mobility transistor (HEMT) is used in various high frequency applications, due to its extremely fast switching speed and low conduction resistance. However, GaN HEMT has poor reverse conduction characteristics under the turn-off condition which causes a dead-time loss. Therefore, as the system switching frequency increases, the effect of the dead-time loss becomes significant. Prior research tried to optimize the dead-time to handle the loss, but these methods need complex mathematical models and real-time calculations according to the load current. To overcome these complex model and calculations, this paper proposes an active gate driver (AGD) to reduce the dead-time loss without any real-time calculation. The circuit design of the proposed AGD is described and the operation sequence is verified with experiment. And the proposed AGD is applied in GaN-based dual active bridge converter to prove the effectiveness of the proposed method. By using the proposed method, the experiment results show that the system efficiency is increased in all load condition.