Integrated Gate-commutated Thyristor - Device Description

Device Description

An IGCT is a special type of thyristor similar to a GTO. They can be turned on and off by a gate signal, have lower conduction loss as compared to GTOs, and withstand higher rates of voltage rise (dv/dt), such that no snubber is required for most applications.

The structure of an IGCT is very similar to a GTO thyristor. In an IGCT, the gate turn off current is greater than the anode current. This results in a complete elimination of minority carrier injection from the lower PN junction and faster turn off times. The main difference is a reduction in cell size, plus a much more substantial gate connection with much lower inductance in the gate drive circuit and drive circuit connection. The very high gate currents plus fast dI/dt rise of the gate current means that regular wires can not be used to connect the gate drive to the IGCT. The drive circuit PCB is integrated into the package of the device. The drive circuit surrounds the device and a large circular conductor attaching to the edge of the IGCT die is used. The large contact area and short distance reduces both the inductance and resistance of the connection.

The IGCT's much faster turn-off times compared to the GTO's allows them to operate at higher frequencies—up to several of kHz for very short periods of time. However, because of high switching losses, typical operating frequency up to 500 Hz.