The structure and working principle of IGBT The difference between igbt and mos tube
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The structure and working principle of IGBT The difference between igbt and mos tube

Posted Date: 2024-02-08

The structure of IGBT (Insulated Gate Bipolar Transistor) consists of P region, N+ region and N region. Its characteristics are as follows:

P area (P-type substrate): P area is the main support structure of IGBT, also called substrate. It is made of P-type material and has a higher doping concentration, usually mainly doped. The role of the P region is to provide junction capacitance and the ability to withstand switching power.

N+ region and N region (N-type region): N+ region and N region are the conductive regions of IGBT. The N+ region refers to a highly doped N-type material region, used to form the trigger electrode and reduce electrode contact resistance. The N region refers to the N-type material region with lower doping concentration, which serves as the main channel and power current control region.

Insulating layer: The insulating layer is located on the surface of the N region of the IGBT. Insulating materials such as silicon oxide (SiO2) are usually used to isolate the control electrode (gate) and the power electrode (P region and N+ region).

Gate: The gate is the part that controls the conduction and turn-off of the IGBT. It is made of a metallic material (usually aluminum or molybdenum) covered with an insulating layer. The gate adjusts the conductivity of the IGBT by controlling the voltage signal to control the power current.

Diode: IGBT generally also integrates an anti-parallel diode inside to withstand the reverse voltage of the inductive component during the switching process.

The structural characteristics of IGBT include gate control, P-type substrate, highly doped N+ region and lower doped N region, insulating layer and anti-parallel diode. These characteristics allow IGBT to combine the advantages of transistors and MOSFETs at the same time, making it suitable for high-power and high-voltage application scenarios.

Structure and working principle of IGBT

Three-terminal device: gate G, collector C and emitter E

Figure 1-22a—N-channel MOSFET and GTR combination—N-channel IGBT (N-IGBT);

IGBT has one more layer of P+ injection area than MOSFET, forming a large-area P+N junction J1.

When the IGBT is turned on, minority carriers are emitted from the P+ injection region to the N base region, thereby modulating the conductivity of the drift region, making the IGBT have a strong current flow capability;

The simplified equivalent circuit shows that IGBT is a Darlington structure composed of GTR and MOSFET, a thick-base PNP transistor driven by MOSFET;

R is the modulation resistance in the base region of the transistor.

The difference between igbt and mos tube

IGBT (insulated gate bipolar transistor) and MOS tube (metal oxide semiconductor field effect transistor) are two common and important power semiconductor devices. They have some differences in structure, working principle and characteristics.

1. Structure and working principle: IGBT is a bipolar device that combines the characteristics of transistors and MOSFETs. It consists of P area, N+ area and N area, similar to the three-pole structure of a transistor. MOS tube is a field effect tube, consisting of a metal gate, an insulating oxide layer and a semiconductor substrate (N or P type).

2. Conduction mechanism: The conduction mechanism of IGBT combines the conduction mechanism of bipolar transistor and MOSFET. It conducts electricity by injecting and controlling a large number of carriers in the base region. The conductivity of MOS tubes mainly relies on the action of voltage to form a channel on the gate, and regulates the flow of electrons or holes in the channel to achieve conductivity.

3. Switching speed: The switching speed of IGBT is relatively slow. Due to the long time it takes for electrons to be injected and eliminated from the base region, the switching time is long and is not suitable for high-frequency switching applications. The switching speed of MOS tubes is relatively fast, and due to the small impact of capacitance effect, it is suitable for high-frequency switching applications.

4. Loss: The switching loss of IGBT is large, and there is a certain conduction voltage drop and switching time when it is turned on. Therefore, large losses occur in applications with frequent switching. The switching loss of MOS tubes is relatively small, the switching speed is fast, and the power consumption is low.

5. Driving voltage: IGBT requires a higher driving voltage, usually between 10V and 20V. MOS tubes only require a lower driving voltage, usually below 5V.

6. Anti-interference ability: IGBT is relatively strong and has good resistance to electromagnetic interference and noise. The MOS tube is relatively weak and susceptible to electromagnetic interference and noise.

IGBT and MOS tubes have their own characteristics and are suitable for different application scenarios. IGBT is suitable for high-power applications, such as industrial power conversion, motor drive, etc. MOS tubes are suitable for low-power applications, such as mobile devices, computer power supplies, etc. Selecting the appropriate device should be based on specific application needs and performance requirements.

Review Editor: Huang Fei


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