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insulated gate bipolar transistor (IGBT)

Insulated Gate Bipolar Transistors (IGBT) are power semiconductors used in power electronics, energy and HVDC technology. They were first introduced in 1979 and have since evolved into high- power electronic components due to technological and process advancements.

The power range of IGBTs is characterized by the voltage range between several hundred volts and several kilovolts, the current range exceeds several kilo-amperes. They are used, among other things, as power semiconductor switches in motor drives, traction controls, UPS systems and switched- mode power supplies.

IGBTs are characterized by the lowest power losses in the on-state and off-state, they require only low drive power and have a high efficiency, which is largely determined by the shading frequency. IGBTs are used at voltages between 600 V and 6 kV and operate at switching frequencies of 2 kHz to 50 kHz. To ensure that they require as little control power as possible, MOSFET gates are used technologically, which has the additional advantage of high input impedance.

Structure of an IGBT

Structure of an IGBT

IGBTs are constructed similarly to MOSFETs, they are available as n- channel or p-channel versions. The main difference compared to MOSFETs is that the p- and n-zones are double diffused and that a p(+) substrate layer is used for the collector, respectively the drain. Since holes drift from the p(+) zone into the n-doped zone, the behavior changes accordingly as in a bipolar device.

The on/off state of an IGBT is controlled by the gate voltage, as in a MOSFET. If the gate voltage is lower than the emitter voltage, the junction between emitter and gate is blocked and no current flows through the IGBT, it is "Off". All applied voltages are then at the oppositely biased junction between the gate and the drift zone. Only a small leakage current flows. The forward breakdown voltage is determined by the breakdown voltage of this junction. This is important because semiconductor power components operate at high voltages and currents. The breakdown voltage of the junction depends on the dopants of both zones.

Semiconductors used in power electronics

IGBT module (IHV) for 4.5 kV, photo: Infineon

IGBT module (IHV) for 4.5 kV, photo: Infineon

Power semiconductors include thyristors, GTOthyristors, MCT thyristors, integrated gate commutated thyristors( IGCT), super junction transistors( SJT), light activated silicon controlled rectifiers ( LASCR), silicon controlled switches( SCS), static induction transistors ( SIT) and static induction thyristors (SITh).

Power semiconductor components are supplied in a wide variety of TO packages such as the TO-3 or the TO-220, or in module form as IGBT High Power Modules( IHM).

Englisch: insulated gate bipolar transistor - IGBT
Updated at: 07.04.2015
#Words: 403
Links: power (P), electronics, high voltage direct current (HVDC), power electronic, process
Translations: DE

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