  In this paper, we investigated a gate driver using a GaN HEMT push-pull
configuration for the high-frequency hard switching of a SiC power MOSFET. Low
on-resistance and low input capacitance of GaN HEMTs are suitable for a
high-frequency gate driver from the logic level, and robustness of SiC MOSFET
with high avalanche capability is suitable for a valve transistor in power
converters. Our proposed gate driver consists of digital isolators,
complementary Si MOSFETs, and GaN HEMTs. The GaN HEMT push-pull stage has a
high driving capability owing to its superior switching characteristics, and
complementary Si MOSFETs can enhance the control signal from the digital
isolator. We investigated limiting factors of the switching frequency of the
proposed gate driver by focusing on each circuit component and proposed an
improved driving configuration for the gate driver. As a result, 20-MHz hard
switching of a SiC MOSFET was achieved using the improved gate driver with GaN
HEMTs.
