Peter Mack

Abstract

This paper presents a 2kW, 100V GaN-based halfbridge power module optimized for high efficiency and power density. The proposed module features a PCB-ceramic stackup combining the advantages of printed circuit board and ceramic substrate technologies. A multilayer flex-PCB design is employed to minimize parasitic inductances, while a highly thermally conductive AIN ceramic interface ensures efficient heat dissipation. These design measures enable high-speed switching operation with output currents up to 70A. Two 100V, 7mΩ GaN bare dies are connected in parallel and used as highand low-side switches. The flex-PCB power-loop design with a 25 μm thin isolation layer enables the realization of a power-loop inductance of 98.6 pH, supporting voltage transitions reaching 48V/ns with maximal voltage overshoots of 17% of the input voltage. The 250μm thick AlN ceramic baseplate provides a low thermal resistance path to the heat sink, resulting in a simulated thermal resistance of 0.49K/W between the GaN die to the heat sink. Evaluated in a 48 V and 75 V buck converter topology, the power module reaches dc-to-dc efficiencies above 98% and output powers of 1.6 kW at 48 V and 2.2 kW at 75 V with maximum operating temperatures of 65° C. With a power density exceeding 800W/cm3 and the capability to operate at MHz frequencies, this GaN half-bridge module based on the proposed PCB-ceramic stack-up offers significant advantages in terms of efficiency, power density, and thermal performance for high-current switched-mode power supplies.