Silicon Carbide (SiC) MOSFETs are being widely adopted in the industry as a viable substitute for
conventional power transistors, due to their superior figure-of-merit and compact, efficient power
conversion. However, the relatively novel manufacturing technology of these devices raises further
questions regarding long-term reliability, as SiC devices have been known to suffer from degradation
over time, manifesting in an increased on-state resistance or a spike in gate leakage current. In order
to identify the remaining useful lifetime of a SiC MOSFET, measuring the on-state resistance
periodically is essential, though the operating voltage and current levels in kilovolts and kiloamperes
presents a challenge, due to the resistance values typically falling in the range of several dozen
Our recent design, as depicted in Figure 1, successfully addresses this challenge and enables reliable
on-state resistance characterization, even during an active converter operation, with an estimated
resistance error of less than 5%. As shown in Figure 2, the key idea behind the proposed design involves
injecting a sinusoidal current in the MHz range, with the resultant voltage being filtered out by custom-engineered analog circuitry. Then, necessary calculations are performed by the circuit, enabling on-state resistance and package inductance to be accurately estimated in the milliohm and nanohenry
ranges, respectively.

Figure 1. Set-up enabling reliable on-state resistance characterization

Figure 2. Circuit for injecting sinusoidal current in the MHz range.