Improved Sensing Circuit for On-State Resistance Measurement of High and Low-Side GaN FETs

This paper presents an improved on-state resistance (RDS
on
) measurement scheme for high and low-side GaN FETs, which is critical for reliable and precise assessment of GaN HEMT power devices’ lifetime and degradation patterns. The proposed circuit is based on an active voltage clamp using Si MOSFET and Schottky and Zener diodes. The proposed circuit features lower parasitic inductances and capacitances by replacing the Si MOSFET with e-mode GaN FET. This modification contributed to much lower ringing and spikes in the voltage and current waveform of both the measurement FET and the DUT. The absence of an embedded body diode in the GaN device in the measurement circuit allows zero reverse recovery operation, making it more viable in high-frequency power converters. This study also provides a detailed design analysis of a bootstrap GaN-based on-state voltage (VDS
on
) sensing scheme for high-side FETs, useful in multiple converter configurations for in-situ devices’ health monitoring and conditioning. Simulation and experimental results validate the performance and features of the proposed concepts.