The role of the IGBT anti-parallel diode

IGBT is a powerful power semiconductor device that is widely used in high-voltage, high-current, and high-speed switching applications. Compared with traditional large-power transistors, IGBT can provide higher power density, as well as higher efficiency and lower conduction loss. However, even with the latest IGBTs, there are still power consumption issues when they are turned off. In this case, it is very important to use IGBT anti-parallel diodes. In this article, we will explain in detail the role of IGBT anti-parallel diodes.

The switching process of IGBT

Before understanding the role of IGBT anti-parallel diodes, we need to understand the switching process of IGBT. When IGBT is turned on, the current drops to a few hundred volts with a very large voltage. In the turn-off process, this current must be quickly reduced to zero. If the turn-off time is too long, a large amount of heat will be generated and may lead to device failure.

When the control signal of IGBT changes, its internal capacitance will discharge, causing the current to change suddenly, which in turn leads to the turn-off of IGBT. This sudden current change is also known as di/dt. In the turn-off process, this di/dt will cause a voltage response, causing the reverse voltage of IGBT to rise sharply. This reverse voltage must be high enough, otherwise IGBT will continue to conduct and cause device damage.

The role of IGBT anti-parallel diodes

IGBT anti-parallel diodes are special diodes that are specially used to support the turn-off process of IGBT. These diodes are typically connected in parallel with IGBT, with the positive pole connected to the negative pole of IGBT and the negative pole connected to the positive pole of IGBT. After IGBT is turned off, it will automatically turn on to protect IGBT from being heated and damaged by exceeding its reverse voltage limit.

When IGBT is turned off, the anti-parallel diode becomes the main channel, which can quickly absorb the current generated by IGBT and limit the change in reverse voltage. Therefore, the main function of IGBT anti-parallel diodes is to protect IGBT from overvoltage and loss, in order to ensure the normal operation and life of IGBT. In addition, IGBT anti-parallel diodes can also reduce the turn-off time of IGBT and lower di/dt, thereby further reducing the power consumption and failure risk of the device.

Conclusion

IGBT anti-parallel diodes can help us solve the turn-off problem of IGBT, keeping di/dt and reverse voltage within a safe range, thereby ensuring that the device can operate normally. Compared with other protective devices, anti-parallel diodes have a faster response speed and lower response time, and can quickly respond when IGBT is turned off. Therefore, IGBT anti-parallel diodes are widely used in various high-power circuits and systems and are an important protective component.