GaN-HEMT fast switching current measurement method based on current surface probe

With the advantage of high bandwidth and small insertion impedance, a current surface probe (CSP) used to measure switching current waveforms is presented in this paper. Its transfer impedance is characterized and validated in the first time by measuring an IGBT switching current with a passive current probe (CP) and a Hall effect current probe (HECP). It is also shown that a return current beneath the PCB on which is put the CSP can reduce its transfer impedance. In the second time, the CSP is used to measure a GaN-HEMT switching current and the obtained results are compared with those measured with a current shunt (CS). The comparison of these results prove that CSP and CS are able to measure fast switching current (of the order a few nanoseconds). However, the advantage of the CSP is that it has no influence on the power device VDS voltage measurement. Also, the CSP brings less parasitic inductance in the commutation mesh than the CS and it does not have the ground connection drawback, which is the case for the CS.