C-<i>RC</i> Snubber Optimization Design for Improving Switching Characteristics of SiC MOSFET
Mengwei Xu, Xin Yang, Jiawen Li
Abstract
The switching oscillations and voltage overshoots excited by ultrafast switching transients are urgently required to be overcome for SiC <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> . Herein, the C- <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RC</i> snubber is employed to address these adverse issues. An optimized C- <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RC</i> snubber design is proposed, which can not only suppress the switching oscillation and overvoltage, but also effectively reduce the snubber loss compared with the dc-link <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RC</i> snubber. This will be beneficial to the actual application of this snubber into the high-power and high-frequency field. For the turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> overvoltage, the varying tendency of the overshoot with snubber parameters are analyzed according to the equivalent impedance network so that the parameter selection principle can be obtained preliminarily. Then, the C- <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RC</i> snubber parametric region where both oscillations and overvoltages can be sufficiently suppressed is established using the root locus. Distinctive from the prior-art C- <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RC</i> design to seek the peak impedance, the proposed switching ringing suppression method is developed by the way of actively assigning poles of fifth-order system to tune an optimal damping ratio. Then, the final design can be determined by minimizing the snubber loss within the obtained parametric range. Finally, the influence of snubber circuit on overvoltage, switching oscillation, and snubber loss are illustrated and verified in detail using the double-pulse tests. Moreover, the application of C- <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RC</i> snubber in the chopper circuit further highlights its superiority of low snubber loss.