A STUDY OF THE INTERNAL DEVICE DYNAMICS OF PUNCH-THROUGH AND NONPUNCH-THROUGH IGBTS UNDER ZERO-CURRENT SWITCHING

The effective use of insulated gate bipolar transistors (IGBT's) requi res a good understanding of their internal device physics, This unders tanding is essential for the optimal interaction among the IGBT's, the ir snubber elements, and the power circuit in which the IGBT's operate , As switching frequencies are pushed to higher values, switching loss reduction becomes an essential part of the design and optimization pr ocess, Soft switching techniques such as zero-voltage (ZVS) and zero-c urrent switching (ZCS) are widely used for this purpose. This study pr ovides insight into the internal dynamic behavior of IGBT's under zero -current switching, The latter is accomplished through mixed-mode simu lation, providing the necessary insight for the improvement of circuit and device performance, In particular, we have analyzed the behavior of the negative current in the nonpunch-through (NPT) devices after th e first zero-current crossing and the effect of the turn-off delay on the tail current, We have also experimentally characterized punch-thro ugh (PT) and NPT IGBT's to confirm the insights provided by the mixed- mode simulation.