A Study on Shunt Resistor-based Current Measurements for Fast Switching GaN Devices

Current viewing resistor (CVR) based measurement of a high frequency switching cell is presented. The drain current of the low-side GaN HEMT switch was measured at 100 kHz switching frequency for a maximum load current of 8 A and a dc input of 80 V. To analyze the results, both simulations and experiments were used. The parasitic elements of the PCB layout (i.e. calculated using the Ansys-Q3D Extractor software) were included in the simulation model. This paper explains the consequences of mounting CVRs in the commonsource path of transistors compared to a circuit without a CVR. Simulation results are found to be in very good agreement with measurements. Hence, the simulation model can be used to estimate the current waveforms when it is not desirable to resort to intrusive measurement methods.