A comparison of IGBT technologies for use in the series connection

This paper is concerned with the performance of IGBTs in series application. The preferred method uses the IGBTs in their active voltage control regime, allowing fast and accurate voltage control of a large number of devices in series. Since turn-off snubbers are not used, the resulting switch is compact and efficient. The advent of high power IGBT modules with square safe operating areas and high overcurrent capabilities allows the method to be used in practical high power circuits. Two well differentiated technologies for IGBTs have emerged-punch trough and nonpunch through. In this paper we discuss briefly the differences between these technology streams and their possible implications with regard to active control for series applications. IGBT modules of 1200 V and 400 A were chosen to represent the two technologies. A gate drive circuit has been developed for use with these modules, which adopts a novel technique to overcome the switching delays associated with such large modules. Results are given for both types of device, in the same circuit, operating near their ratings, without any particular device specific optimisation. The results show that the active voltage control method can be successfully used with both types and the technique largely removes the influence of the technology factors. It is concluded that the methods used are suitable for commercial use in a wide range of applications.