Quantitative Analysis of Different Operating Conditions' Effect on Dynamic On-Resistance in Enhancement-Mode GaN HEMTs

Abstract

The dynamic on-resistance issue is problematic in existing GaN HEMTs as it increases the conduction loss of the converter in real operations. In this paper, the different operating conditions' effect on the dynamic on-resistance is evaluated experimentally for a commercial enhancement-mode GaN HEMT. Specifically, a double-pulse-test setup with a fast dynamic on-resistance measurement circuit is designed, and the impact of dc-link voltage, load current and turn-on gate resistance on the dynamic on-resistance is assessed. From the experimental results, it is observed, for the first time, that the turn-on gate resistance can affect the dynamic on-resistance especially at the high current and high voltage region. At 400 V/ 25A, more than 27% increase of dynamic on-resistance is observed when the turn-on gate resistance changes from 0 Ω to 20 Ω. Meanwhile, different from the previous studies, it is observed that the dc-link and load current's effect on the dynamic on-resistance relies on the operating conditions. Specifically, their impacts are more significant at the high current and high voltage regions. To find out the reason for these experimental results, a quantitative correspondence of the dynamic on-resistance and the energy used to generate hot electrons is established. It is concluded that the dynamic on-resistance's dependency on turn-on gate resistance, dc-link voltage and load current can be explained by the variation of the hot electron generation during the hard-switching transient.