5-MHz Operation of a DC 565-V SiC-MOSFET Half-Bridge Inverter by Reducing Thermal Resistance of General-Purpose Gate Drivers

This paper challenges a 5-MHz operation of a DC 565-V SiC-MOSFET half-bridge inverter by reducing thermal resistance of gate drivers. Experimental results show that the SiC-MOSFET half-bridge inverter can continuously operate under a soft-switching condition at the DC-link voltage of 565 V even the switching frequency of 5 MHz commonly used for driving GaN devices. First, this is achieved by reducing a thermal resistance of the gate driver. The thermal resistance of the gate driver is reduced by removing a resin on a top surface of the gate driver and attaching a heatsink on it. Secondly, the power loss of SiC-MOSFET is reduced by suppressing the increase of an on-resistance of SiC-MOSFET due to the decrease of the gate-source voltage by a common-mode voltage generated by the switching operation of SiC-MOSFET. Inserting a common-mode choke to an isolated DC-DC converter for a high-side gate driver prevents the output voltage of the isolated DC-DC converter from the decrease. Finally, a prototype circuit with 4th Generation SiC-MOSFETs was able to output 1 kW continuously.