Short Circuit Study of 600 V GaN GITs

The short-circuit robustness of 600 V/30 A GaN gate injection transistors (GITs) was evaluated under various operating conditions to determine the worst-case short-circuit scenario. Although a decrease in maximum short-circuit current was observed with higher bus voltage, the short-circuit withstand time decreases dramatically. At room temperature and a bus voltage of 500 V, the short-circuit withstand time is as short as 160 ns as opposed to 220 ns at 400 V. The withstand time also depends on the maximum short-circuit current and can be extended significantly by reducing the drain current during a short-circuit event. The devices were shown to withstand a short-circuit event for considerably longer period with an elevated initial junction temperature as a result of lower drain current. With short-circuit current reduced from 110 A to 70 A, the withstand time was increased from 215 ns at 25°C to over 10 μs at 150°C and V
_dc
= 400 V. A gate-sensing protection scheme for GaN GIT was evaluated over various operating conditions and shown to successfully protect devices in less than 150 ns after short-circuit condition up to T
_j
= 150°C and V
_dc
= 500 V.