A High-Bandwidth and Easy-to-Integrate Parasitics-Based Switching Current Measurement Method for Fast GaN Devices

Abstract

While the very high switching speed of the gallium nitride devices can easily enable power electronics converters to operate at multi megahertz, it also brings huge challenges to switching current measurement, which is very important for the evaluation of switching performance. The conventional switching current measurement methods either have low bandwidth or have influence on layout inductance. To address these issues, this article proposes a high-bandwidth and easy-to-integrate switching current measurement method, with almost no influence on power loop layout. The proposed method utilizes the power loop trace from the source terminal of bottom switch to circuit ground as the sensing trace. By measuring the sensing voltage and considering the frequency-dependent parasitic inductance and resistance of the sensing trace, the switching current is derived based on the Fourier series theory. The simulation verification is firstly performed by using LTspice, and shows consistent results. Then, to accurately measure the sensing voltage, the used voltage probe TPP1000 is carefully modeled for measurement compensation and correction. Finally, two double pulse test (DPT) boards are designed, one with coaxial current shunt and the other without coaxial current shunt. Through DPT experiment, the accuracy of the proposed method with almost no insertion inductance is verified.