Very Fast Short Circuit Protection for Gallium-Nitride Power Transistors Based on Printed Circuit Board Integrated Current Sensor

Gallium-Nitride power transistors have a limited short-circuit withstand time, which can be as low as 200 ns. Typical short-circuit detection methods such as the desaturation detection method and current based methods present difficulties when they are applied to Gallium Nitride devices. The former requires a blanking time and therefore can detect a short-circuit at a relatively late stage, this method also reacts slowly under high-inductive short circuits. Current based methods require either a special transistor with a current mirror or a special package with a Kelvin connection. This work presents the use of a current sensor integrated into a printed circuit board to perform a very fast short-circuit detection. Two detection methods using the integrated current sensor were implemented, which neither use a blanking time nor require a special transistor package. The functioning under both Hard Switch Fault and Fault Under Load types of short circuit was experimentally tested and a resulting short circuit detection time as low as 30 ns is demonstrated.