The Impact of Multi-MHz Switching Frequencies on Dynamic On-Resistance in GaN-on-Si HEMTs
Grayson Zulauf, Mattia Guacci, Juan Rivas-Davila, Johann W. Kolar
Abstract
Dynamic on-resistance (dR <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</sub> ), 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 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</sub> 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 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</sub> 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 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</sub> . For the tested HEMT, we find a maximum dR <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</sub> increase over the DC resistance of 2× in a multi-MHz, zero-voltage-switched application.