An in-depth analysis of the working mechanism and characteristics of IGBT

Date：2024-03-20 13:51:27 Views：212

In modern electronic devices, IGBT (Insulated Gate Bipolar Transistor) plays an important role and is widely used in the field of power electronics. It not only has the advantages of MOSFET and GTR, but also has the characteristics of high input impedance and low on state voltage drop. In order to better understand the working principle of IGBT, we need to conduct in-depth research on its internal structure and dynamic characteristics. This article will take you to uncover the mystery of IGBT and explore its working principle and characteristics.

1、 The structure and equivalent circuit of IGBT

Equivalent circuit of IGBT

The internal structure of IGBT is complex and precise, and its equivalent circuit is shown in Figure 1. From the figure, it can be seen that when a forward voltage is applied between the gate and emitter of the IGBT, the MOSFET conducts, forming a low resistance state between the collector and base of the PNP transistor, thereby causing the transistor to conduct. On the contrary, when a 0V voltage is applied between the gate and emitter of the IGBT, the MOSFET shuts off, cutting off the base current supply to the PNP transistor, causing the transistor to shut off.

2、 Analysis of the working characteristics of IGBT

static characteristic

The static characteristics of IGBT mainly include volt ampere characteristics, transfer characteristics, and switching characteristics. The volt ampere characteristics describe the relationship between gate source voltage and drain current. By controlling the gate source voltage, we can adjust the magnitude of the drain current. The transfer characteristic describes the relationship between the output drain current and the gate source voltage, usually in a linear relationship in a conducting state. The switch characteristics describe the relationship between the drain current and the drain source voltage. When the IGBT is in the on state, the drain current is mainly borne by the MOSFET, and the on state voltage is relatively low, resulting in strong voltage resistance.

Dynamic characteristics

The dynamic characteristics of IGBT include the opening process and the closing process. During the turn-on process, it is mainly operated by MOSFETs. Only in the later stage of the decrease in drain source voltage, will the PNP transistor change from the amplification region to the saturation region, and this process has a certain delay time. During the shutdown process, the waveform of the drain current becomes two segments, and due to the presence of stored charges, the tail time of the drain current is longer.

3、 Key factors and safety reliability of IGBT

The determining factors of voltage and current

The safety and reliability of IGBT are mainly determined by the following factors: voltage between gate and emitter, voltage between collector and emitter, current flowing through collector emitter, and junction temperature. Properly controlling these factors can ensure the normal operation and long lifespan of IGBT.

Limitations of voltage and current

If the driving voltage is too low, the IGBT cannot operate stably; On the contrary, if the pressure resistance is exceeded, it may cause permanent damage. Similarly, if the voltage between the collector and emitter exceeds its withstand voltage, the current flowing through the IGBT will also exceed its maximum allowable value, leading to damage. In addition, the junction temperature of IGBT also needs to be controlled within the allowable range to avoid permanent damage.

4、 Outlook and Innovation Trends of IGBT Applications

Multi domain applications

With the continuous development of electronic technology, IGBT has been widely used in various fields. It is used in high-voltage power systems, transportation vehicles, electric boilers, solar and wind power generation systems, etc. IGBT plays a crucial role in these applications, improving system efficiency and stability.