An in-depth analysis of the influence of voltage and current on the IGBT shutdown process

Date：2024-03-05 17:08:21Views：29

In the field of power electronics, insulated gate bipolar transistors (IGBTs) are a critical power switching device, and the performance of their turn off process directly determines the efficiency and stability of the entire system. The changes in voltage and current play a crucial role in this process. This article will conduct an in-depth analysis of how voltage and current affect the turning off process of IGBTs, and explore how to improve the working efficiency of IGBTs by optimizing control strategies, providing valuable references for engineers and researchers in related fields.

The influence of voltage on the shutdown process

Voltage plays an important role in the shutdown process of IGBT. Firstly, as the collector emitter voltage (VCE) increases, the depletion layer width also increases, leading to an extended turn off time. This is because a larger VCE causes the disappearance of the channel inversion layer to take longer, thereby delaying the shutdown process.

Secondly, high VCE leads to current amplification factor β Reduce, thereby reducing the proportion of trailing current and shortening the shutdown time. This is because the increase in VCE reduces the charge injection rate, slowing down the rate of recombination of excess carriers in the base region, thereby reducing the duration of the trailing current.

In summary, voltage has a dual impact on the turning off process of IGBT. On the one hand, a larger VCE increases the shutdown time; On the other hand, high VCE reduces the proportion of trailing current, thereby shortening the shutdown time.

The influence of current on the shutdown process

In addition to voltage, current also affects the turning off process of IGBT. The turn off time is mainly affected by the current on the time required for the recombination of excess carriers in the n-region. As the current increases, the proportion of trailing current to total current decreases, thereby shortening the turn off time.

When the current is small, the rate of decrease in turn off time is greater. This is because under low current conditions, the recombination rate of excess carriers in the n-region is faster, and it does not take too long to complete the recombination process.

However, when the current is high, the rate of decrease in turn off time slows down. This is because under high current conditions, due to the large number of injected carriers, the recombination speed of excess carriers in the n-region slows down, thereby prolonging the turn off time.

Factors to consider in practical applications

In practical applications, we need to set the dead time reasonably based on the working current range and avoid operating the IGBT under low current conditions to avoid adverse consequences. By setting a reasonable dead time, the impact of trailing current can be reduced and system performance can be improved.

In addition, for high-voltage applications, an increase in VCE can lead to an extension of shutdown time. Therefore, when designing power electronic systems, it is necessary to balance the size of VCE to balance system performance and shutdown time.

This article analyzes the turning off process of IGBT from two aspects: voltage and current. The voltage has a dual effect on the turn off time, on the one hand, it prolongs the turn off time, and on the other hand, it shortens the proportion of trailing current. The current mainly affects the rate of decrease in turn off time. The rate of decrease in turn off time is greater under smaller currents, and slower under larger currents.

In practical applications, we need to set the dead time reasonably based on the working current range and avoid IGBT operating under low current conditions to minimize the shutdown time. In addition, in high-voltage applications, attention should be paid to the impact of VCE size on the shutdown time, balancing system performance and shutdown time.