The Impact of Multi-MHz Switching Frequencies on Dynamic On-Resistance in GaN-on-Si HEMTs

Dynamic on-resistance (dR
_on
), where the on-resistance immediately after turn-on is higher than the DC resistance, increases the conduction losses in power converters with gallium nitride high-electron-mobility transistors (GaN HEMTs). There exist no direct dR
_on
measurements in the literature above 1 MHz, leaving designers unable to predict conduction losses in emerging multi-MHz applications. We address this literature gap by collecting the first on-state voltage dR
_on
measurements at multi-MHz frequencies, with a focus on the zero-voltage-switching conditions that are predominantly employed at high frequency. On the selected commercially-available HEMT with a breakdown voltage below 200 V, the dynamic contribution asymptotes above ≈ 2 MHz, a finding predicted by the slow time constants of the traps that cause dR
_on
. For the tested HEMT, we find a maximum dR
_on
increase over the DC resistance of 2× in a multi-MHz, zero-voltage-switched application.