The outstanding feature of the IGCT - leading to its name and its main advantages - is not only the silicon wafer itself, but the way it is driven by the gate - the electrical and mechanical gate-drive design. The «hard- drive» concept at the heart of IGCT operation requires the mechanical integration of gate driver and semiconductor into one single unit with low circuit inductance. It also implies a number of new converter features, which make IGCT converters different from GTO or IGBT converters. It is the scope of this application note to make designers familiar with the data sheets and the use of IGCTs in their main application areas.
The following features are important to remember:
• no turn-off snubber is needed in applications without series connection; where turn-off snubbers are used, they are considerably smaller than those of GTOs
• the customer control interface is reduced to a power supply, an optical control input and an optical status feedback output
• gate drive geometry is an important parameter in mechanical stack design.
It should be noted that «IGCT» is a generic reference to the complete device. «GCT» refers to the semiconductor press-pack component. Further distinctions can be made to distinguish RC-IGCTs (reverse- conducting), RB-IGCTs (reverse blocking) and AS-IGCTs (asymmetric with neither reverse blocking nor reverse-conducting capability).
