What is the full form of IGBT

IGBT: Insulated-Gate Bipolar Transistor

IGBT stands for Insulated-Gate Bipolar Transistor. A three-terminal power semiconductor known as an Insulated-Gate Bipolar Transistor (IGBT) is primarily employed as an electronic switch and has evolved over time to integrate high performance and quick switching. The metal-oxide-semiconductor (MOS) gate structure controls its four alternating layers (P-N-P-N).

IGBTs are utilised for fast switching purposes and are three-pin semiconductor devices. Although the IGBT's structure is topologically identical to that of a MOS-gate thyristor (MCT), only the transistor action is allowed across the entire device operating range. It includes BJT output characteristics and MOSFET input characteristics.

The Insulated Gate Bipolar Transistor has a standard bipolar transistor at the outputs and an insulated gate from a MOSFET at the inputs. The IGBT's conduction pins are the collector and emitter terminals. The control terminal is at the input gate terminal. The gate terminal regulates the conduction.

Identical to bipolar junction transistors, the insulated gate bipolar transistor has voltage and current ratings when IGBT is utilised as a switch with static control. But, the presence of an isolated gate terminal from the MOSFET makes IGBT a less complex device than BJT. When there is a gate terminal that is isolated, the IGBT uses less power.

Electric vehicles, locomotives, variable-speed refrigerators, light ballasts, arc welding equipment, and air conditioning systems are a few examples of high-power applications requiring switching power sources like IGBT.

IGBT Modules

When BJT and MOSFET cannot produce the desired outcomes in high current applications, IGBT is employed in various electronic switching applications. This two-transistor hybrid device has voltage-controlled properties similar to MOSFETs and switching and conduction properties similar to BJTs. There are two main categories for IGBT devices, such as:

NPT-IGBT (Non-Punch Through IGBT)
PT-IGBT (Punch Through)

i) Non-Punch Through IGBT [NPT-IGBT]

Symmetrical devices are another name for these IGBTs. Non-Punch Through-IGBT (NPT-IGBT) is the name of the IGBT transistors that do not include an n+ buffer layer. As both the backward and the forward breakdown voltages in this situation are the same, due to this, these devices are referred to as symmetrical devices.

In the event of a short-circuit failure, these devices are more robust and thermally stable. Additionally, the turn-off loss won't alter significantly as a result of the varying temperature; rather, it stays constant. In Non-Punch Through IGBT, the P-layer (collector side) is also heavily doped.

They are excellent options for AC circuits because they are created using lower-cost diffusion process technology. Additionally, the NPT structure guarantees these devices' capacity to block in both directions. In this scenario, the N base is substantial.

ii) Punch Through IGBT [PT-IGBT]

Another name for these IGBTs is asymmetrical devices. As the forward breakdown voltage is greater than that of the reverse breakdown voltage, due to this, they are said to be asymmetrical.

In the event of a short circuit failure, these devices are less robust and thermally unstable. And in this instance, turn-off loss is closely correlated with temperature; hence, it rises sharply as temperature rises.

The N-epitaxial water process, which is expensive, is used to make these IGBTs. They have a small N base, and the reverse blocking capacity of the PT structure is also less. They are frequently used in DC circuits where the device doesn't require reverse voltage support.

IGBTs will develop the ideal solid-state by combining high switching performance such as MOSFETs & low conduction loss such as BJTs, making them a good choice for various applications.

Importance of IGBT

The power MOSFETs' basic gate-drive properties are combined with the bipolar transistors' high current & low saturation voltage capabilities in the IGBT. A bipolar power transistor is a switch, and an isolated-gate FET is the control input in an IGBT. IGBTs are employed in moderate- to high-power applications such as induction heating, traction motor control, and switched-mode power supplies. Big IGBT modules often have numerous parallel devices and can handle large currents in the range of hundreds of amps with blocking voltages as high as 6500 V. These IGBTs are capable of managing hundreds of kW loads.