What is IGBT and its function

Introduction

In the world of power electronics, the Insulated Gate Bipolar Transistor (IGBT) plays a vital role. It combines the advantages of both the Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) and the Bipolar Junction Transistor (BJT). This article aims to provide a comprehensive understanding of IGBT and its essential functions in various applications.

What is IGBT

IGBT stands for Insulated Gate Bipolar Transistor. It is a three-terminal semiconductor device that combines the low saturation voltage of a BJT with the high input impedance and switching speed of a MOSFET. The IGBT is constructed by placing a MOSFET input stage on top of a BJT output stage. This unique combination of components results in a device capable of handling high voltage and high current levels.

Structure and Working Principle

In the on-state of the IGBT, when a positive voltage is applied to the gate terminal, it creates an electric field that influences the P base region. This electric field causes the injection of minority carriers (holes in this case) from the P base into the N- drift region. As a result, a conducting channel is formed in the N- drift region, allowing current to flow between the collector and the emitter.

The formation of the conducting channel occurs due to the modulation of the P base region by the electric field. The electric field reduces the width of the depletion region between the P base and the N- drift region, allowing the injected holes to reach the N- drift region. This process is known as the conductivity modulation effect.

The conductivity modulation effect is a significant advantage of the IGBT over conventional MOSFETs. It enables the IGBT to handle high current densities without suffering from excessive voltage drop. As a result, the IGBT can operate at higher power levels while maintaining low saturation voltage characteristics similar to a BJT.

In the off-state of the IGBT, the gate voltage is set to zero or a negative value. This causes the depletion region to expand, preventing the injection of minority carriers into the N- drift region. As a result, the conducting channel is interrupted, and the IGBT behaves as an open switch, blocking the current flow between the collector and the emitter.

The ability of the IGBT to switch between the on-state and off-state rapidly makes it suitable for applications that require high-frequency switching, such as motor control and power conversion. The IGBT offers the advantages of high input impedance and fast switching speed similar to MOSFETs, while also providing the low saturation voltage and current-handling capabilities of BJTs.

In summary, the structure and working principle of the IGBT involve the modulation of the P base region through the electric field created by the gate voltage. This modulation allows the IGBT to function as a low-resistance switch in the on-state and as an open switch in the off-state. The conductivity modulation effect enables the IGBT to handle high currents while maintaining low voltage drops, making it a key component in power electronics applications.

Function of IGBT

Power Switching: One of the primary functions of IGBT is power switching in various applications. It can handle high voltages and currents, making it suitable for controlling the flow of power in systems such as motor drives, renewable energy systems, and high-power industrial equipment.

Amplification: IGBTs can also function as amplifiers in audio and radio frequency (RF) applications. By applying a small signal to the gate terminal, the IGBT can amplify it to a higher power level, allowing it to drive speakers or transmit signals over long distances.

Pulse Width Modulation (PWM): IGBTs are widely used in PWM techniques to control the average power delivered to loads. By rapidly switching the IGBT on and off, the duty cycle can be adjusted to regulate the power output. PWM is commonly used in motor control, uninterruptible power supplies (UPS), and adjustable speed drives.

Voltage and Current Regulation: With their ability to handle high voltage and current levels, IGBTs are essential for voltage and current regulation in power systems. They help maintain stable voltage levels, prevent overloads, and protect sensitive components from damage.

Reference: Global IGBT Shortage (https://www.nevsemi.com/blog/global-igbt-shortage-cause-future-outlook)

Conclusion

In conclusion, the Insulated Gate Bipolar Transistor (IGBT) is a critical component in power electronics due to its ability to handle high voltages and currents. Its unique combination of MOSFET and BJT characteristics enables efficient power switching, amplification, PWM control, and voltage/current regulation in a wide range of applications. Understanding the function and operation of IGBTs is essential for engineers and technicians working in the field of power electronics.