Three-Level Gate Drivers for eGaN HEMTs in Resonant Converters

Commercial eGaN HEMT gate drivers focus on high reliability to the strict gate driving voltage against parasitic components. However, they do not consider the high reverse conduction voltage due to the reverse conduction mechanism under ZVS condition. A three-level gate driver is proposed for eGaN control HEMTs. The midlevel voltage reduces the reverse conduction voltage since that the reverse conduction voltage decreases when gate voltage increases. The proposed driver is applied to a 7-MHz isolated resonant SEPIC converter. The efficiency was improved from 72.7% using conventional driver to 73.4% (an improvement of 0.7%) with 24-V input and 5-V/10-W output. An eGaN SR gate driver is proposed to minimize the reverse conduction time. The driver uses a wave-shape circuit, designed by the HEMT rectifier mathematic model built with the MATLAB script, to compensate the driving IC propagation delay and obtain desired driving signal timing. The proposed SR driver improves the efficiency from 79.9% without considering the driving IC delay to 84.7% (an improvement of 4.8%) with 18-V input and 5-V/10-W output.