GaN FETs in Polarity Protection Designing and testing reverse current protection solutions for -48V DC system using GaN FETs

Abstract

In -48 V DC telecommunication systems, wiring errors, hot-plug events, and loadside backfeed can create reverse current paths that may damage sensitive electronics. Conventional silicon MOSFET-based protection circuits are widely used to prevent such failures. However, they often require several parallel devices to reduce conduction loss and support higher load current, increasing the required PCB area. To reduce PCB area, Gallium Nitride (GaN) FETs offer a promising alternative due to their low on-state resistance, compact package size, and strong electrical performance. Therefore, this thesis investigates whether GaN FETs can provide reverse current protection in a -48 V DC system with comparable efficiency to silicon-based solutions, while enabling a more compact PCB implementation. The thesis presents the design, simulation, PCB implementation, and experimental validation of single and parallel GaN-based protection circuits. The single-device circuit was validated up to 500 W as a proof of concept, which can be scaled to higher power levels using parallel transistors. The results show that the GaN-based protection circuit conducts during forward operation and blocks reverse current during fault conditions. Compared with the silicon-based reference, the GaN solution provides comparable efficiency and manageable thermal performance, while reducing component count and PCB area. Furthermore, the parallel configuration improves current capability and reduces thermal stress. However, due to GaN sensitivity to parasitic effects, careful gate-drive tuning and PCB layout are required. Overall, the results show that the GaN FET-based approach is a suitable solution for compact polarity protection in -48 V applications, particularly when PCB area reduction is a key design requirement.