A new discrete GaN-based dv/dt control circuit for megahertz frequency power converters

• Presents a novel GaN-based discrete active gate driver (AGD) with closed-loop dv/dt control for MHz-frequency power converters. • The AGD circuit achieves precise dv/dt regulation using a small capacitor dv/dt sensor coupled with a modified cascoded current mirror circuit. • The AGD circuit, utilizing four discrete N-channel GaN FETs, delivers high-bandwidth, high-gain dv/dt control without the complexity of integrated circuits. • Experimental results demonstrate a reduction in turn-on dv/dt from −15 V/ns to −11 V/ns in a 10 MHz, 24 V buck converter, using only a 0.1 pF sensor capacitor. • PSpice simulations validate the AGD's ability to produce feedback currents several orders of magnitude higher, improving gate current control and enhancing system stability. In this paper, we present a novel GaN-based discrete current mirror active gate driver (AGD) for closed-loop dv/dt control, designed specifically for megahertz (MHz) frequency power converters employing power devices with low reverse transfer capacitance ( C R S S ) values. The proposed AGD circuit, implemented using four N-channel GaN FETs, addresses the limitations of existing dv/dt control methods by providing a high-bandwidth, high-gain solution without the complexity of integrated circuits or reliance on conventional complementary current mirror configuration. Experimental validation in a 10 MHz, 24 V buck converter demonstrates a significant reduction in the turn-on dv/dt of the low-side switch from -15 V/ns to -11 V/ns, achieved with a small 0.1 pF sensor capacitor. This reduction was realised while maintaining sub-nanosecond-level response time and ensuring effective dv/dt regulation during the turn-on switching transient. Simulation results, verified through PSpice models, confirm the AGD's ability to generate feedback currents several orders of magnitude higher using the small sensor capacitor, thereby reducing gate current and enhancing system stability. The circuit design also benefits from using GaN technology, enabling higher switching frequencies and improved power conversion efficiency. This work offers a promising solution for discrete dv/dt control in MHz frequency applications, providing a foundation for future advancements in GaN-based AGD systems.