In-situ Measurement and Physical Mechanism of Dynamic RON in GaN-on-Si Monolithic Half-Bridge Power IC
Abstract
Dynamic on-resistance (RON) is a critical stability concern for GaN high-electron mobility transistors (HEMTs). In GaN monolithic half-bridges on conductive Si substrate, the dynamic RON of high-side (HS) device can be more severe than that of discrete HEMTs due to the back-gating effect. However, current evaluation methods typically apply a DC or pulsed substrate bias while keeping the HS device always ON, which differs from the application-use condition in power converters. This work proposes a new circuit method for accurate in-situ extraction of the dynamic RON of an HS device in steady-state hard switching. The measured dynamic RON is found to be nearly twice the value measured by the conventional pulsed bias method. This suggests an interplay between the back-gating effect and the hard-switching stress to deteriorate dynamic RON. To validate this interplay effect, two buck converters are constructed based on a monolithic half-bridge and a discrete device-based half-bridge, respectively. We tune the converter loss to be dominated by the HS device by implementing a hard turn-on for the HS device and a zero-voltage-switching for the low-side device. A lower efficiency is observed in the monolithic half-bridge-based converter, and the dynamic RON is verified to be higher than that obtained from the pulsed bias method. The physical mechanism of this interplay phenomenon is also revealed. Overall, this work manifests the importance of dynamic RON measurement of GaN-on-Si power IC under practical switching conditions; the proposed circuit method provides a powerful tool for the evaluation and qualification of GaN monolithic half-bridge.
Xin Yang
Ph.D. Student
Hongchang Cui
Ph.D. Student
