Electrical Energy Management Group

Resonant gate drivers for SiC MOSFETs

Resonant gate drivers are not generally used in commercially available converters, due to the perceived additional complexity. However, there are some striking advantages over conventional gate drivers. These silicon gate drivers can be located at a safe distance from wide-bandgap power devices with a higher thermal rating. And, the energy used to charge the gate can be recycled. At MHz switching frequencies this becomes significant.‌ In the shown example, a current is set up in inductor L1, which is then re-routed into the gate to turn on the SiC device.

Conventional versus resonant gate driver for SiC

‌‌A conventional voltage source driver can create unwanted oscillations in voltage and current, as shown on the right. This leads to the risk of cross-talk between device gates, which could potentially lead to spurious turn-on of devices and resulting converter failure. 

The resonant gate driver is seen, in the lower figure, to switch the SiC device faster with lower oscillation in the gate signal. A portion of the charge used to raise the gate voltage is recycled at turn-off. At switching frequencies above MHz this provides a significant increase in converter efficiency.