Gallium Nitride Efficacy for High-Reliability Forward Converters in Spacecraft

Abstract

Gallium nitride (GaN) devices show particular promise for space-rated power conversion applications that rely on MOSFET technology whose performance is severely limited by the radiation hardening processes. Although the number of radiation-hardened (rad-hard) GaN devices is low, the current space-rated selection pool can still yield significant efficiency and power density improvements. However, the context of GaN research is often future-oriented such that the application of GaN to common, proven, space-rated converter designs is rare. The presented work quantifies the performance benefits of market available, space-rated GaN HEMTs over rad-hard MOSFETs for a synchronous forward converter, which remains an extremely popular topology for isolated, medium-power, dc–dc conversion on various satellite systems. Two 75-W, space-rated forward converters were designed, implemented, and benchmarked, with the power switch technology being the single variable of change. By forming Pareto-optimal fronts of the key device metrics, optimal rad-hard MOSFETs were chosen so that the baseline converter performance was considered the best case. The frequency limitations of common, available, rad-hard PWM controllers limited the power density in the GaN and Si converters alike; however, efficiency gains proved sizeable. The GaN-based converter saw a peak efficiency of 86%, which was a 4.54% improvement over the Si baseline. Detailed efficiency and loss differential plots are presented, which show the GaN converter’s reduced sensitivity to the input voltage.