Gallium-Nitride (GaN) Transistor Design for Transient-Overload Power Applications

Gallium-nitride (GaN) transistors offer unparal-leled switching speed for power electronics, e.g., for high-frequency applications or drastically reducing magnetics. Of par-ticular importance are the short-term overload capabilities of such circuits. Such short-term overload is required for most real-world applications with short-circuit risk, start-up currents, and a number of emerging special applications in medi-cine as well as scientific instrumentation. The compact packages and lead-frame-free design of typical GaN transistors challenge the thermal design as their transient behavior becomes more pronounced. This paper proposes a design idea of focusing on the thermal dynamics during pulses, and explores different ther-mal configurations for GaN transistors, e.g., by attaching copper mass as a thermal buffer between transistors and heat sink. The configurations are compared through finite-element transient thermal analysis, which verifies the great effectiveness of thermal buffer in improving the thermal performance during short-term and pulsed load. A prototype is built with the proposed thermal configuration. The system achieves MHz-range pulses in hard switching.