Design and Experimental Demonstration of Integrated Over-Current Protection Circuit for GaN DC-DC Converters

This article reports the design and the first experimental demonstration of the monolithically integrated over-current protection (OCP) circuit in GaN power converters. The design criteria and protection time estimation methods are proposed. Through the GaN integration platform based on normally-OFF AlGaN/GaN metal insulator semiconductor high electron mobility transistors (MIS-HEMTs), the OCP circuit is monolithically integrated with the gate driver and GaN switches. At the over-current incident, the current sensing signal is compared with over-current thresholds, and then the generated protection action signal is clamped to disable the high-side gate driver and shut down the GaN dc-dc buck converter. The analysis of current paths, SPICE-based simulations, and numerical description of the protection process are carried out to support the proposed design criteria and estimation methods. The experimental results show that the GaN dc-dc buck converter can be protected within one duty cycle period according to the desired preset over-current thresholds. The consistent results of the calculated and measured time periods in the OCP process have verified the proposed design criteria and estimation methods. The proposed OCP circuit together with the analysis can help researchers to design and estimate the OCP process in integrated GaN power converters.