Analyze and Design of Digitally Load Current Modulated Active Gate Driver for GaN HEMTs based Buck DC-DC

The active gate driver (AGD) reduces instability and electromagnetic interference (EMI) resulting from rapid switch-node slew rates in the half-bridge driver of gallium nitride (GaN) high electron mobility transistors (HEMTs) while maintaining the switching speed. This paper seeks to improve the effectiveness of the AGD method by integrating the influence of load current on the voltage slew rates. Consequently, we present a tri-current AGD prototype that employs a 4-bit current-based DAC to accurately regulate the drive current during the Miller Plateau (MP) phase. By measuring the load current, we implement the feedback control of the MP drive strength via a digital loop on the FPGA. Experimental measurements validate that the suggested AGD circuit sustains an overshoot voltage of 0.3V/A when the load current fluctuates between 0.8A and 4A and achieves a driving speed of 25.6% faster than the conventional methods.