Power Loss Modeling and Impact of Current Measurement on the Switching Characterization in Enhancement-Mode GaN Transistors

Gallium nitride (GaN) high electron mobility transistors (HEMTs) show potential for high-efficiency power converters, but as switching frequencies increase, a need arises for analytical models to predict performance and estimate switching losses. This article presents a precise and straightforward power loss model for high-voltage enhancement-mode GaN HEMTs, accounting for parasitic inductances, non-linear junction capacitances, and transconductance. The model employs MATLAB to predict switching waveforms and compute total losses, and the accuracy is verified against experimental tests and LTspice simulations. Such a simple model with fewer operations and fast computations is advantageous when used in converter optimization problems, such as design optimization, where multiple variables are considered, or in real-time applications, where optimal control is required. It is worth noting that the increased switching speeds enabled by GaN devices pose challenges in measuring switching currents, which are critical for evaluating performance and computing losses in experimental tests. Conventional methods for switching current measurements have limited bandwidth or affect layout inductance. This study also explores the implications of integrating coaxial current shunts, commonly used for measuring current in fast-switching transistors, into the source path of transistors, comparing the circuit's behavior with and without the shunts.