Analytical Switching Loss Model for GaN-Based Control Switch and Synchronous Rectifier in Low-Voltage Buck Converters

In this paper, an analytical switching loss model for a gallium nitride (GaN) based control switch (CS) and synchronous rectifier (SR) in low-voltage buck converters is proposed. Based on the consideration of parasitic inductances, SR reverse conduction voltage drop, and overshoot current effect caused by output capacitance of SR, the total switching loss is modeled with regard to both CS and SR, which can lead to more accurate prediction of power loss and system efficiency in low-voltage buck converters. The modeling results show that the percentage of SR switching loss in total switching loss is 25.4% in the 12-1.2-V converter, which is far larger than the 6.3% in the 48-5-V converter, and this verifies the necessity of including SR into the model for low-voltage converters. Experiment results exhibit an average increase of 52.3% and 66.1% in the accuracy of predicted system efficiency and converter power loss through the proposed model with SR than conventional models from 400 kHz to 1 MHz.