Power electronics - IGBT
Tutorial on power electronics
Power Electronics - IGBT
Insulated Gate Bipolar Transistor (IGBT) is a three terminal semiconductor device and is mainly used as an electronic switch . It is characterized by fast switching and high efficiency, making it a necessary component in modern devices such as lamp ballasts, electric cars and variable frequency drives (VFD).
Its ability to turn on and off quickly, makes it applicable in amplifiers to process complex wave patterns with pulse width modulation. The IGBT combines the characteristics of MOSFETs and BJTs to achieve high current and low saturation voltage capability respectively. It incorporates an insulated gate using FET (Field Effect Transistor) to obtain a control input.
The amplification of an IGBT is calculatede by the ratio of its output signal to its input signal. In conventional BJTs, the degree of gain (β) is equal to the ratio of its output current to the input current.
The IGBT has a very low ON state resistance (RON) compared to a MOSFET. This implies that the voltage drop (I 2 R) across the bipolar for a particular switching operation is very small. The forward blocking action of the IGBT is similar to that of a MOSFET.
When an IGBT is used as a controlled switch in a static state, its current and voltage are equal to that of the BJT. On the contrary, the insulated door in the IGBT makes it easier to control the BJT loads and therefore less energy is required.
The IGBT is activated or deactivated depending on whether its door terminal has been activated or deactivated. A constant positive potential difference between the gate and the transmitter keeps the IGBT in the ON state. When the sigInput nal is deleted, the IGBT is deactivated.
Principle of operation of the IGBT
The IGBT only requires a low voltage to maintain the conduction in the device unlike BJT. The IGBT is a one-way device, that is, it can only turn on in the forward direction. This means that current flows from the collector to the emitter unlike MOSFETs, which are bidirectional.
The IGBT is used in medium to very high power applications, for example a traction motor. In large IGBTs, it is possible to manage a high current of the order of one hundred amperes and blocking voltages of up to 6kv.
IGBTs are also used in power electronic devices such as converters, inverters and other devices the need for solid state switching is required. Bipolar are available with a courant and high voltage. However, their switching speeds are low. On the contrary, MOSFETs have high switching speeds although they are expensive.