IGBT And Its Applications

Insulated Gate Bipolar Transistor

The Insulated Gate Bipolar Transistor also called an IGBT for short, is something of a cross between a conventional Bipolar Junction Transistor, (BJT) and a Field Effect Transistor, (MOSFET) making it ideal as a semiconductor switching device.

The IGBT transistor takes the best parts of these two types of transistors, the high input impedance and high switching speeds of a MOSFET with the low saturation voltage of a bipolar transistor, and combines them together to produce another type of transistor switching device that is capable of handling large collector-emitter currents with virtually zero gate current drive.

Typical IGBT (Single)

Toshiba MG300J2YS50 - 600V 300A Half-Bridge / Dual IGBT Module

The Insulated Gate Bipolar Transistor, (IGBT) uses the insulated gate (hence the first part of its name) technology of the MOSFET with the output performance characteristics of a conventional bipolar transistor, (hence the second part of its name). The result of this hybrid combination is that the “IGBT Transistor” has the output switching and conduction characteristics of a bipolar transistor but is voltage-controlled like a MOSFET.
IGBTs are mainly used in power electronics applications, such as inverters, converters and power supplies, were the demands of the solid state switching device are not fully met by power bipolars and power MOSFETs. High-current and high-voltage bipolars are available, but their switching speeds are slow, while power MOSFETs may have high switching speeds, but high-voltage and high-current devices are expensive and hard to achieve.
The advantage gained by the insulated gate bipolar transistor device over a BJT or MOSFET is that it offers greater power gain than the bipolar type together with the higher voltage operation and lower input losses of the MOSFET. In effect it is an FET integrated with a bipolar transistor in a form of Darlington configuration as shown.

Applications for IGBTs:

IGBTs are used in high power applications such as:

• Appliance motor drives
• Electric vehicle motor drives
• Power factor correction converters
• Uninterruptible power supplies
• Solar inverters
• High frequency welders
• Inductive heating cookers

The pictures below are the IGBT half bridge switch that I used in one of my early inverters.
























The two orange wires are the gate leads. The bare twisted cable on the bottom is the conductor linking the Emitters/Sources. It is a high gauge wire, pure copper. The black materials that the single IGBTs are attached are aluminum heat-sinks. NOTE! The two heat-sinks must not touch each other. As you see them bin the below picture, they are separated from each other.

 Today, I use IGBTs more than MOSFETs in my homemade Inverters.