On the Analysis of Asymmetrical Switching of SiC MOSFETs

A thorough understanding of SiC MOSFETs' dynamic characteristics, particularly switching behavior and asymmetry, is essential to ensure system stability and enable more precise switching control. However, the fundamental causes and mechanisms of switching asymmetry have yet to be fully understood. This study focuses on investigating the causes of switching asymmetry by analyzing the current and the voltage flow inside the device. DPT experiments and TCAD simulations using the 5-contact method were conducted to analyze the asymmetry observed in the Miller region. The analysis reveals that the difference in the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I_GD</i> during the Miller period is the primary contributor to the switching asymmetry, as it directly affects the charging and discharging behavior of the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C_GD</i>. Furthermore, switching asymmetry was examined under various operating conditions such as drain current, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R_ds_(on)</i>, external gate resistance, and temperature. Among these factors, the drain current was found to be the most influential parameter that contributes to the asymmetry. A cross-over point is observed where the switching asymmetry reverses as the drain current increases. This reversal highlights the dominant role of the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I_GD</i>. These findings are expected to provide valuable insights for the design and optimization of gate-drive circuits in SiC MOSFET-based systems.