A Resonant Gate Driver with Variable Gain and a Capacitively Decoupled High-Side GaN-FET

Abstract

Here we describe a gate-driver with resonant action that minimizes gating loss at high switching frequencies (10-20 MHz) while facilitating variable voltage gain that can exceed the supply rails. The gate voltage swing can be controlled with minimal duty cycle constraints, making this driver capable of meeting the diverse drive requirements of different switch technologies and converter topologies. A prototype uses two small N-channel gallium nitride (GaN) transistors within the drive structure, significantly decreasing parasitics. To do so, a capacitive decoupling technique is used to allow the high-side N- channel device’s ‘flying’ driver to receive power; a distinct challenge for flying drivers commuting between two variable voltages. The prototype was applied to several high frequency switching devices. Up to a 72% reduction in gating-loss is observed as compared to a conventional hard-charged gate-driver while maintaining rise and fall times <18 ns for the devices tested.