Ultralow Input–Output Capacitance PCB-Embedded Dual-Output Gate-Drive Power Supply for 650 V GaN-Based Half-Bridges

Abstract

Wide-bandgap devices have been widely used to reduce the size and increase the efficiency of power converters by operating at a high switching frequency, at the expense of heightened radiated and conducted electromagnetic inference (EMI) emissions, of which the latter circulates through the power loop and ancillary circuitry. In effect, the parasitic isolation capacitance $C_{i}$ of the gate-driver power supply represents a key EMI propagation path to be controlled in order to ensure the operational integrity of power converters. To this end, this paper proposes an integrated, dual-output gate-drive power supply for gallium-nitride (GaN) 650 V, 60 A, half-bridge phase legs, rated at 2 W (2 × 1 W), 15 to 2 × 7 V, featuring an ultralow $C_{i}$ of 1.6 pF, an output-to-output parasitic capacitance of 1.6 pF, a power density of 72 W/in3, and an efficiency of 85%. All this is attained using an active-clamp flyback converter switching at 1 MHz using 65 V GaN high-electron-mobility transistor devices and Schottky output rectifiers, and a Pareto-optimized transformer design minimizing its interwinding capacitances, volume, and losses. Finally, the transformer is fully embedded in a printed circuit board (PCB) material, doubling as a substrate for the topside active layer of the power supply. The paper presents the complete design procedure, processing, and experimental demonstration of the proposed integrated power supply, evaluating as well the reliability impact of the magnetic-PCB material interface in high ambient temperature applications (>200 °C).