An Electric Field Probe With High Immunity for SiC MOSFET Switching Voltage Measurement

Accurate measurement of switching voltage is the basis for evaluating the dynamic behavior of power devices. With the development of wide bandgap (WBG) devices, the high switching speed of the silicon carbide metal-oxide-semiconductor field-effect transistors (SiC MOSFETs) imposes high bandwidth and strong immunity requirements on the voltage probe. The electric field probe (EFP) based on the principle of electric field coupling has a naturally high bandwidth, which can be considered as a potential competitor. However, due to the noncontact suspended measurement method, the interference signal is easily coupled by the EFP and affects the measurement accuracy. Thus, this article proposes a high noise-immune structure for EFP to implement the measurement of SiC MOSFET switching voltage. The EFP is manufactured from the printed circuit board (PCB), which can provide a more accurate parameter design. Then, the shielded copper clad and via arrays structures are proposed, and the effectiveness of the shielding structure is verified by adding an interference source. Finally, through the double-pulse test, it is demonstrated that the performance of the proposed EFP is sufficient to measure the switching voltage of SiC MOSFETs.