Analysis of the working structure and principle of IGBT

Date：2024-03-21 16:11:33 Views：190

IGBT, also known as insulated gate bipolar transistor, is an important component in the field of power electronics. It has advantages such as voltage control, simple driving, high-speed switching, low power consumption, large safe working area, and can withstand high currents/voltages. This article will provide a detailed introduction to the structure and working principle of IGBT.

1、 The structure of IGBT

IGBT consists of three parts: a P-type semiconductor (called voltage controlled switching diode or JFET) and two N-type semiconductors. The voltage controlled switch diode is located at the top, and two N-type semiconductors are located at the bottom, forming two collector regions. By applying voltage between the collector areas, the on-off of the diode can be controlled, thereby achieving current switching control.

2、 The working principle of IGBT

The working principle of IGBT is mainly based on voltage control and composite modulation of charge carriers. When a forward voltage is applied, that is, when a forward voltage is applied between the P-type semiconductor and the N-type semiconductor, that is, when UCE<0, that is, when a forward voltage is applied between the emitter and collector, that is, when UCE>0, electrons flow from the N-type semiconductor to the P-type semiconductor, forming a current. At the same time, a small amount of holes flow from P-type semiconductors to N-type semiconductors, forming a reverse current. At this point, the IGBT is in a conductive state.

When a reverse voltage is applied, that is, when a reverse voltage is applied between the P-type semiconductor and the N-type semiconductor, that is, when UCE>0, that is, when a reverse voltage is applied between the emitter and collector, that is, when UCE<0, holes flow from the P-type semiconductor to the N-type semiconductor, and electrons flow from the N-type semiconductor to the P-type semiconductor, forming a very small current. At this time, the IGBT is in the off state.

3、 The switching process of IGBT

The switching process of IGBT includes two stages: on and off. During the turn-on phase, when a forward voltage is applied, i.e. UCE<0, electrons flow from N-type semiconductors to P-type semiconductors, forming a large amount of current. At this point, a small amount of holes flow from the P-type semiconductor to the N-type semiconductor, forming a reverse current. When the current reaches a certain value, the IGBT enters a saturation state.

In the turn off stage, when reverse voltage is applied, i.e. UCE>0, holes flow from P-type semiconductor to N-type semiconductor, and electrons flow from N-type semiconductor to P-type semiconductor, forming a very small current. As time goes on, electrons and holes gradually decrease, the current decreases, and finally reaches zero. At this point, the IGBT is in the off state.

4、 Factors affecting IGBT performance

The main factors that affect the performance of IGBT are as follows:

Switching speed: The switching speed of IGBT has a significant impact on its performance. Switching too fast may cause excessive surge current and damage the IGBT; Slow switching speed can lead to increased losses.

Thermal performance: IGBTs are prone to thermal collapse and breakdown at high temperatures. Therefore, effective heat dissipation measures need to be taken to improve its thermal performance.

Safe working area: The safe working area of IGBT is limited by its physical characteristics. In applications, it is necessary to ensure that it operates within a safe working area to avoid damage or failure.

Driving circuit: The driving circuit of IGBT also has a significant impact on its performance. A suitable driving circuit can improve the performance and stability of IGBT.

In summary, the structure and working principle of IGBT have a significant impact on its performance and stability. Understanding the structure and working principle of IGBT can help to better apply and optimize its performance. With the development of power electronics technology, IGBT will be widely used in more fields.