Impedance-Matching Shunt: Current Sensor With Ultrahigh Bandwidth and Extremely Low Parasitics for Wide-Bandgap Device

The current shunt with high bandwidth and low parasitics is critically needed to satisfy the soaring current slew rate of the wide-bandgap (WBG) device. However, the existing lumped parameter model is inappropriate to model and design the next-generation ultrahigh bandwidth current shunt, leading to the unclear bandwidth limitation, inextricable invasive effect, and lacked design guidance. In this letter, by introducing the transmission line theory, it is revealed that, due to the impedance mismatch, the strong signal reflection inside the current shunt results in the high-frequency parasitic inductance, which severely deteriorates its bandwidth. On this basis, the concept of the impedance-matching shunt (IM-shunt) is then proposed to derive the mathematical model-guided design methodology for the high-performance current shunt. With the aid of the proposed concept, the current shunt with > 3 GHz bandwidth and < 0.1 nH parasitics is developed. The comparative experiments further ensure the accurate and nonintrusive characterization of the switching trajectories for the WBG application.