Optimisation and integration of an active clamping circuit for IGBT series association

Among the various solutions for the series association of high power IGBTs, the active clamping circuit insures both protection and voltage balancing, within good reliability and compactness. Therefore, this structure has been chosen to be integrated closed to the IGBTs. The design of this circuit leads to the resolution of a compromise between a good balancing and limited additional losses. The aim of this paper is to optimise this circuit, in order to reduce the losses, in the IGBTs as well as in the active clamping circuit. This design has been validated in a 3 kV 400 A test bench, using three 1.7 kV components in series.