A High-Bandwidth Integrated Current Measurement for Detecting Switching Current of Fast GaN Devices

Abstract

Gallium nitride (GaN) devices are suitable for high-frequency power converters due to their excellent switching performance. To maximize the performance of GaN devices, it is necessary to study the switching characteristics, which requires measuring the switching current. However, GaN devices have a fast switching speed and are sensitive to parasitic parameters, so the current measurement should have a high bandwidth and should not introduce excessive parasitic inductance into the power converters. Traditional current measurements are difficult to meet these requirements, especially for fast GaN devices. This paper presents a high-bandwidth integrated current measurement for detecting the switching current of fast GaN devices. By effectively utilizing the parasitic inductance in the circuit, a single-turn coil is embedded in the printed circuit board. This coil could pick up a sufficiently strong voltage signal, which is then processed to reconstruct the switching current. Moreover, corrections are carried out to further improve the accuracy. The current measurement has a small insertion impedance and a high bandwidth with a small influence on the parasitic inductance of the converter. The accuracy of the current measurement is experimentally verified by a 40 V GaN-based double pulse test circuit with a load current up to 25 A.