What's IGBT - How it Works

The insulated-gate bipolar transistor (IGTB) device is a type of three-terminal power semiconductor device which are basically used as electronic switch and is also known for providing a combination of  extremely fast switching and high efficiency in the more newer devices.

IGBTs for High Current Applications

A range of modern appliances such as VFDs (Vaiable Frequency Drives), VSFs (variable speed refrigerators), trains, stereo systems with switching amplifiers, electric cars, and air conditioners use insulated-gate bipolar transistor for switching the electric power.

Symbol of depletion mode IGBT

In case the amplifiers use insulated-gate bipolar transistor often synthesize waveforms which are complex in nature along with low-pass filters and pulse width modulation; as insulated-gate bipolar transistor are basically design to turn on and off on a fast and rapid pace.

The pulse repetition rates are boasted by the modern devices which consist of switching application and fall well within the ultrasonic range which are the frequencies which are ten times higher than the highest audio frequency handled by the device when the devices is used in the form of an analog audio amplifier.

The MOSFETs consisting of high current and characteristics of a simple gate-drive is combined with the bipolar transistors which has low-saturation-voltage capacity by the IGTB.

IGBTs are a Combination of BJT and Mosfet

A single device is made by IGBT by combining the bipolar power transistor which acts as a switch and an isolated gate FET which acts as the control input.

The insulated-gate bipolar transistor (IGTB) is majorly used in applications which consists of multiple devices which are placed in parallel to each other and most of the times have capacity of handling very high current which are in the range of hundreds of amperes along with a 6000V of blocking voltage, which in turn is equal to hundreds of kilowatts use medium to high power such as induction heating, switched-mode power supplies, and traction motor control. Insulated-gate bipolar transistors which are large in size.

IGBTs are the Most Advanced Transistors

Insulated-gate bipolar transistor (IGTB) is a new and recent invention of the time. The first-generation devices which were invented and launched in 1980s and the early years of 1990s were found to have slow switching process relatively and are prone to failure through different modes such as latchup (where the device will continue to be switched on and not turn off till the current keeps on flowing through the device) and secondary breakdown (where when high current flows through the device, a localized hotspot present in the device goes into thermal runaway and as a result burns the device).

There was a lot of improvement observed in the second-generation devices and the most new devices on the block, the third-generation devices are considered even better than the first tow generation devices.

New Mosfets are Competing with IGBTs

The third-generation devices consist of MOSFETs with speed rivaling, and tolerance and ruggedness of excellent level.

The devices of second and third generation consists of pulse rating which are extremely high which make them very useful in order to generate large power pulses in various areas such as plasma physics and particle. Thus the second and third generation devices have superseded mostly all the older devices such as triggered spark gaps and thyratrons used in these areas of plasma physics and particle.

These devices also hold attraction for the hobbyist of high-voltage due to their properties of high pulse ratings and availability in the market at low prices. This enables the hobbyist to control huge amounts of power in order to drive devices such as coilgums and Tesla coils.

Insulated-gate bipolar transistors are available at affordable price range and thus act as an important enabler for hybrid cars and electric vehicles.

By Surbhi Prakash

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Melisa Whitt said…
I have a cm400hc6-24nfm 400 amp IGBT and I have found that in order to yurn it off i have to use a pull down resistor anywhere from 10k to 1 meg works ok
do you know if that is with all IGBTs ? oh this is not melisa this is her husband Brandon I come to your site often you have a lot of good tutorials
Swagatam said…
thanks Brandon, yes according to me all IGBTs would require an identical response to shut down completely, in fact all switching devices including BJTs, and mosfets may be recommended to have their own pull down resistors across their triggering terminal and ground in order to safeguard against false tripping of the device.
Melisa Whitt said…
very well said thank you for a fast response
Swagatam said…
you are welcome :)

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