Wen Zhang,
Candidate for Master's Degree
Defense of a Master's Thesis
Faculty Advisor: Dr. Fred Wang

Title: 
Current Sensor for Wide-bandgap Devices Dynamic Characterization

Abstract:
High bandwidth sensors are required to measure the wide-bandgap devices' transient behavior because of their very fast switching speed. In addition to the high bandwidth, the current sensor must also introduce little disturbance to the switching power loop. Specifically, excessive extra parasitic inductance introduced by the current sensor drastically changes the switching behavior, making the measurement result invalid.

Conventional high bandwidth current sensors are first reviewed here to understand their limitations. By combining the structure of coaxial shunt resistor and alumina substrate of surface mount thin film resistors, a novel current sensor surface mount coaxial shunt resistor (SMDCSR) is then introduced. Its performance is modeled and experimentally characterized. Experimental testing verifies its capability of achieving very high bandwidth of up to 2 GHz while introducing little parasitic inductance of less than 0.2 nH. Compared with state-of-the-art commercial products, SMDCSR achieves more than 10x higher bandwidth and less than 1/10 insertion inductance. SMDCSRs are thus ideal for current measurement where high bandwidth and low electrical footprint are required, especially the wide-bandgap devices dynamic characterization.