A Junction Temperature Smoothing Control Method for SiC MOSFETs Based on the Gate Driving Signal Delay

Abstract

Low frequency junction temperature fluctuation caused by changes in load current or ambient temperature can severely accelerate the aging development and reduce the operational lifetime of power switching devices. Therefore, junction temperature smoothing control (JTSC) is important for high reliability operation. Conventional JTSC methods require complex additional hardware. Moreover, they are invasive with compromising on the output power quality of the converter. To solve these problems, a novel JTSC method is proposed based on the adjustment of the gate driving signal delay ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</sub> ). <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">First</i> , the relationship between <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</sub> and the power loss is analyzed. It is discovered that the power loss is positively linear to <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</sub> , which is the basis for JTSC. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Second</i> , a JTSC strategy is proposed based on the proportional-integral control. The gate driving signal delay can be adjusted adaptively according to the proposed control algorithm. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Third</i> , the effectiveness of the proposed JTSC method is verified by experiments. The junction temperature fluctuation can be eliminated by 50 % in various load conditions. Compared with conventional JTSC methods, the proposed method has almost no compromising on the output power quality of the converter, and it requires no additional hardware with low cost.