Analysis of the Desaturation Circuit Behaviour Under Paralleled GaN Devices Including the Effects of Parasitic Parameters

The paper introduces a desaturation-based short-circuit protection scheme, optimized for GaN devices in parallel configuration and subject to parasitic effects. When connecting GaN devices in parallel, a careful design is essential to limit mismatches in the parasitic inductances and capacitances in the power and drive paths among the different legs in parallel. Even when well balanced, parasitic parameters generate oscillations that are responsible for false alarms or delays in short-circuit detection. The paper analyzes in detail the origins of these instabilities and introduces design guidelines to mitigate their impact. A simulation campaign investigates a half-bridge circuit composed of four paralleled GaN devices. Key design challenges are identified, and targeted recommendations are provided to improve robustness and ensure timely fault detection. The results demonstrate that, with proper design, the desaturation technique can ensure reliable short-circuit detection. The detection time achieved at 400V DC is 150ns with a total protection response time of 250ns.