摘要： The dynamic on-resistance is problematic as it can impair the converter's efficiency due to the increased conduction loss. In this paper, the hard-switching transient's effect on the dynamic on-resistance is, for the first time, evaluated experimentally on a commercial high-voltage GaN HEMT. A new R_dyn-ds,on measurement circuit with fast sensing speed is designed, and an accurate measurement of R_dyn-ds,on can be realized experimentally within 49.6 ns after the device's current reaches to the load current. A double-pulse-test setup is designed to comprehensively evaluate the switching transient's effect on R_dyn-ds,on under different operating conditions. From the experimental results, it is found that the turn-on and turn-off gate resistance have a significant impact on the dynamic on-resistance whereas the cross-talk effect on R_dyn-ds,on is negligible. Specifically, at 400 V/25 A, more than 27% (28.2%) increase in R_dyn-ds,on is observed when the external turn-on (turn-off) gate resistance increases from 0 Ω to 20 Ω. Detailed discussion and quantitative analysis are provided to explain the experimental results. In terms of the turn-on process, it is concluded that the R_dyn-ds,on variation is mainly caused by the different numbers of generated hot electrons. For the turn-off transient, it is confirmed the variation of drain current at different dv/dt slew rate leads to the R_dyn-ds,on difference.