An Online Gate Oxide Degradation Monitoring Method for SiC MOSFETs With Contactless PCB Rogowski Coil Approach
Jianlong Kang, Ankang Zhu, Yu Chen, Haoze Luo, Lei Yao, Zhen Xin
Abstract
Real-time degradation monitoring (DM) of the gate oxide is an effective method to improve the reliability of SiC <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> applications <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">.</i> Currently, the existing DM methods generally require direct electrical connection with the device, which undoubtedly reduces the reliability of monitored system. This article proposes a contactless DM method based on the turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> transient current rate with fixed delay time ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">di/dt</i> - <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Delay</sub> ), which is realized by a printed circuit board (PCB) Rogowski Coil. First, the effectiveness of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">di/dt</i> - <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Delay</sub> as a degradation precursor is verified by high temperature gate-bias test. The results show that the maximum <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">di/dt</i> of planar and trench gate devices decreases gradually with the gate oxide degradation and finally decreases by 51.2% and 33.6%, respectively. Secondly, the low-temperature sensitivity of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">di/dt</i> is verified, and the conclusion that the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">di/dt</i> under short delay time is independent of drain-source voltage ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DS</sub> ) and current ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DS</sub> ) is given. Then, a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">di/dt-</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Delay</sub> extraction circuit based on PCB Rogowski Coil is designed, which has a measurement bandwidth of at least 38 MHz. The effectiveness of this real-time DM method is verified in a buck converter. The proposed method can provide a valuable tool for continuous health monitoring in emerging applications of SiC <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> s to high-reliability applications.