A Study of Current and Voltage Measurements in Gan Modules for High-Power Applications

Abstract

Gallium Nitride (GaN) devices are increasingly considered for high-power power electronics applications due to their high efficiency and fast switching capability. However, their voltage rating is typically limited to 650 V, requiring the use of multi-level converter topologies to address higher DC bus voltages. This paper investigates a 1200 V / 150 A GaN power module designed for high-power flying capacitor applications. The module integrates four GaN transistors with embedded decoupling capacitors to reduce parasitic inductance and facilitate the implementation of multi-level architectures. Static and dynamic characterization is performed up to 80 A and junction temperatures reaching 125°C. An ON-State Voltage Measurement Circuit (OVMC) is implemented to accurately measure the drain-source voltage during switching transitions, enabling extraction of the dynamic on-state resistance over a wide operating range. Results show a clear temperature dependence of $R_{DS,on}$, increasing from approximately 15–16 mΩ at 25°C to about 26–30 mΩ at 100°C, while remaining relatively stable with current. In addition, a modeling-based method is proposed to estimate the internal transistor current during double-pulse testing when direct measurement is impractical due to module packaging constraints. The method reconstructs the switching current waveform using a transfer-function model of the sensing path, enabling estimation of switching energies without direct access to the device current.