A general expression for IGBT turn-off loss for switched mode operation

Accurate loss analysis of switch mode circuits that use IGBTs as a switching device is difficult. Switching losses are a function of switch current, collector Voltage and junction temperature. These 3D parameters increase equation complexity and are often time consuming in their determination. However, computer programs such as Mathcad, provide a practical means of curve fitting empirical data. This article outlines a methodology for recording and converting empirical IGBT performance data into accurate and useful equations. These equations may then be used as simple function calls for loss analysis calculations. The example covered in this paper is that of the IGBT clamped inductive turn-off. Predicted loss from the empirical equation is compared with in-circuit measurements.