Pulsed performance of high voltage IGBTs and other input controlled devices

This paper examines the switching properties of IGBTs and other input controlled devices for driving thermionic devices. In particular, attention is drawn to the turn off behaviour under short pulse operation, with a load fault condition. Examination of potential fault conditions when the device is conducting, leads one to the conclusion that switching stress at the gate input, when the output of the device is rapidly switched due to a load fault, can result in relatively high voltages and currents in the gate structure. If not fully analysed and controlled, these conditions could result in sudden unexpected failure, or gradual degradation and subsequent failure of the device, in a time significantly shorter than the expected design life. During turn off, following a load fault, the let-through charge and peak current may also be damaging for both the switching device and the load being driven. The paper presents a test circuit used for the evaluation, some results from those tests, an examination of important parameters for device selection and suggestions for device selection. An important conclusion for pulse applications was that the selection of the devices required great care and one should avoid focusing on the headline parameters of the devices. Some outline computer modelling was also introduced to support the view that the nature of the internal gate resistance required further study