A Short-Circuit Protection Circuit With Strong Noise Immunity for GaN HEMTs

Abstract

Gallium nitride high electron mobility transistors (GaN HEMTs) show significant advantages in high frequency and high switching speed applications, which has gathered great interests. Due to the low short-circuit withstand capacity, the short-circuit protection with high response speed is critical for GaN HEMTs. Besides, the high switching speed of GaN HEMTs brings severe interference to protection circuits, which becomes a key obstacle for ultrafast short-circuit protection. This article analyzes the interference mechanism of dv/dt noise on the desaturation short-circuit protection circuits in detail. According to the noise propagation model, an improved protection circuit is proposed, in which a discharging capacitor is employed to enhance the noise immunity behavior. In addition, optimization methods of the key parameters are presented, which allow the designers to evaluate the noise immunity of the protection circuits with different parameters during the design processes. The experimental results show that the response time of the protection circuit is within 110 ns. Without the proposed methods, the noise introduced by a low dv/dt of 2.5 V/ns will generate false-trigger protection actions. The improved protection circuit can survive under the dv/dt up to 84 V/ns, which verifies the validity of the proposed optimization methods.