Inverter gate drive and phase leg development for 175°C operation

An inverter phase leg has been developed that can operate in an ambient temperature up to 175 degrees Celsius using commercially-available components to the greatest possible extent. This phase leg includes a discrete gate drive circuit that incorporates both level-shifting and isolated power supply functions. A high-temperature prototype gate drive has been built and tested using small- signal bipolar transistors and diodes combined with suitable high-temperature passive components rated for operation at temperatures up to 200degC. A SPICE model was developed to study the gate drive operating characteristics over a wide temperature range from 25 to 175degC. Measured results closely match the simulation results. In addition, the gate drive circuit has been tested as part of a complete half-bridge inverter utilizing a pair of silicon carbide DMOSFETs and Schottky diodes together with stacked ceramic capacitors. Experimental results show that the gate drive and phase leg performance characteristics are well behaved at all temperatures up to 175degC.