Active Gate Driver for Dynamic Current Balancing of Parallel-Connected SiC MOSFETs

In high-power applications, parallel connection of discrete silicon carbide (SiC) mosfets is necessary to increase the current rating. However, the unbalanced dynamic current during switching transient may cause unequal power loss and thermal distribution, which is a great challenge in parallel applications. In this article, a dynamic current balancing method based on a new active gate driver (AGD) is proposed to improve the current sharing. The principle of the AGD is based on di/dt feedback control and voltage controlled current source to adjust gate drive current of SiC mosfets. Therefore, the switching trajectory of the paralleled devices can be changed to achieve current balance. In addition, by using master-slave control strategy, the proposed AGD can be easily used for multiple paralleled devices. The double pulse tests are conducted to verify the effectiveness of the proposed AGD. For two paralleled devices, the turn-on and turn-off switching energy imbalances are reduced from 13.4% and 56.0% (12.1% and 52.9%) to 8.8% and 15.3% (8.0% and 8.8%) by the current source (current sink) circuit. For six paralleled devices, the degrees of turn-on and turn-off switching energy imbalances can be reduced from 21.8% and 16.1% to 11.8% and 7.8% by the proposed AGD.

Automated summary

In this article, a dynamic current balancing method based on a new active gate driver (AGD) is proposed to improve current sharing in parallel applications. The AGD adjusts the gate drive current of SiC mosfets by di/dt feedback control and voltage controlled current source, changing the switching trajectory to achieve current balance. The proposed AGD can be easily used for multiple paralleled devices using a master-slave control strategy. Experimental results show that the proposed AGD effectively reduces the turn-on and turn-off switching energy imbalances in paralleled devices.