An Improved Equivalent Circuit Model of SiC MOSFET and Its Switching Behavior Predicting Method
Xin Li, Fei Xiao, Yifei Luo, Ruitian Wang, Z.W. Shi
Abstract
Wide-bandgap (WBG) power devices have better dynamic characteristics and higher working temperatures compared to traditional Si devices and are more suitable for high-frequency and high-voltage applications because of fast turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> and turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> speeds. The main obstacle for the use of WBG devices is the high-frequency oscillation (HF-Osc) in voltage and current during the switching process. In this article, a new method of predicting the SiC <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> switching behavior (including HF-Osc and slow switching) is proposed. First, the models of nonlinear capacitances are improved and parasitic elements are taken into account for improving the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RLC</i> equivalent circuit of the <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> switching transient. On this basis, the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC</i> equivalent frequency is obtained. Then, a new method is proposed to obtain the SiC <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> instantaneous frequency. The comparison between them in the time domain makes it possible to analyze the SiC <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> switching behavior. The prediction method is verified using a CREE SiC <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> via a double pulse test. Experimental and simulation results show that the prediction method is effective in describing the HF-Osc characteristics. The proposed method can be used to effectively improve the <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> HF-Osc, which provides guidance for the application of SiC <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> s.