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

This paper reports the design and the first experimental demonstration of the monolithically integrated over-current protection circuit in GaN power converters. The design criterions and protection time estimation methods are proposed. Through the GaN integration platform based on normally-OFF AlGaN/GaN MIS-HEMTs, over-current protection circuit is monolithically integrated with gate driver and GaN switches. At over-current incident, the current sensing signal is compared with over-current thresholds, 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 in current paths, SPICE-based simulations and numerical descriptions of protection process are carried out to support the proposed design criterions and estimation methods. The experiment results show that the GaN DC-DC buck converter can be protected within one duty cycle period according to desired preset over-current thresholds. The consistent results of calculated and measured time periods in over-current protection process have verified the proposed design criterions and estimation methods. The proposed over-current protection circuit together with the analysis can help researchers to design and estimate the over-current protection process in integrated GaN power converters.