Understanding IGBT Basics: What is it? What’s the Working Principle?

July 14, 2021

IGBT (Insulated Gate Bipolar Transistor) is a composite fully controlled-voltage-driven-power semiconductor device composed of BJT (Bipolar Junction Transistor) and MOS (Insulated Gate Field Effect Transistor), which has self-shutdown The characteristics of the break. Simply put, it is a non-on-and-off switch. The IGBT has no function of amplifying voltage. It can be regarded as a wire when it is turned on, and it is regarded as an open circuit when it is off. IGBT combines the advantages of BJT and MOSFET, such as low driving power and reduced saturation voltage.

IGBT module is a modular semiconductor product that is packaged by IGBT and FWD (freewheeling diode chip) through a specific circuit bridge. It has the characteristics of energy saving, convenient installation and maintenance, and stable heat dissipation.

IGBT is the core device for energy conversion and transmission, and the “CPU” of power electronic devices. The use of IGBT for power conversion can improve the efficiency and quality of electricity consumption, has the characteristics of high efficiency, energy saving and environmental protection, and is a key supporting technology to solve the problem of energy shortage and reduce carbon emissions.

IGBT is a Darlington composite device with GTR as the dominant element and MOSFET as the driving element. There are three electrodes on the outside, namely G-gate, C-collector, and E-emitter.

During the use of the IGBT, the collector-emitter voltage UCE and gate-emitter voltage UGE can be controlled to control the on/off/blocking state of the IGBT.

1) When 0 or negative voltage is applied to the gate-emitter of the IGBT, the channel in the MOSFET disappears and the IGBT is turned off.

2) When the collector-emitter voltage UCE0, there are two situations:

② If the gate-emitter voltage UGEUth, the gate channel is formed, and the IGBT is in a conducting state (normal operation). At this time, holes are injected from the P+ region into the N base region for conductance modulation, reducing the value of the resistance RN of the N base region, and reducing the on-state voltage drop of the IGBT.

Main application areas of IGBT

As the mainstream device of new power semiconductor devices, IGBT has been widely used in traditional industrial fields such as industry, 4C (communication, computer, consumer electronics, automotive electronics), aerospace, national defense and military industry, as well as rail transit, new energy, smart grid, new Strategic emerging industries such as energy vehicles.

1) New energy vehicles

IGBT modules play a vital role in electric vehicles and are the core technical components of electric vehicles and charging piles. IGBT modules account for nearly 10% of the cost of electric vehicles and about 20% of the cost of charging piles. IGBT is mainly used in the following aspects in the field of electric vehicles:

A) The electric control system drives the car motor after a high-power DC/AC (DC/AC) inverter;

B) Vehicle air-conditioning control system Low-power DC/AC (DC/AC) inverter, using small current IGBT and FRD;

C) Charging pile The IGBT module in the intelligent charging pile is used as a switching element;

2) Smart grid

IGBTs are widely used in power generation, transmission, substation and power consumption of smart grids:

From the perspective of power generation, rectifiers and inverters in wind power generation and photovoltaic power generation all require the use of IGBT modules.

From the perspective of the transmission end, the FACTS flexible transmission technology in UHV DC transmission requires a large number of power devices such as IGBTs.

From the point of view of the substation, IGBT is a key component of the power electronic transformer (PET).

From the perspective of power consumption, household white electricity, microwave ovens, and LED lighting drivers all have a large demand for IGBTs.

3) Rail transit

IGBT devices have become mainstream power electronic devices for traction converters and various auxiliary converters of rail transit vehicles. AC drive technology is one of the core technologies of modern rail transit. In the AC drive system, the traction converter is a key component, and the IGBT is one of the core components of the traction converter.

More about IGBT: https://www.utmel.com/blog/categories/transistors/characteristics-and-working-principle-of-igbt

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