Power Electronics IGBT - Power Electronics

What is IGBT in Power electronics?

IGBT (Insulated gate bipolar transistor) is a semiconductor device which consists of three terminals and is mostly used as an electronic switch. IGBT can be distinguished by fast switching and high effectiveness, this is the reason why it acts as an essential component in modern appliances like lamp ballasts, electric cars and variable frequency drives (VFDs).

IGBT has the ability to turn on and off rapidly and this quality will make it appropriate in amplifiers for processing difficult wave-patterns with pulse width modulation. IGBT will combine the characteristics of MOSFETs and BJTs for getting high current and low saturation voltage capacity correspondingly. It will integrate an isolated gate through FET (Field effect transistor) for getting a control input.

IGBT Symbol

igbt_symbol.jpg

In conventional BJTs, the degree of gain (β) will be equivalent to the ratio of its output current to the input current. Amplification of an IGBT can be calculated by the ratio of its output signal to its input signal.

IGBT will have a very less value of ON state resistance (RON) when compared to a MOSFET. This means that the voltage drop (I2R) across the bipolar for a specific switching operation is very less and the forward blocking action of the IGBT is same as MOSFET.

While using IGBT as controlled switch in a static state, it’s current and voltage ratings will be equal to BJT. In contrast, the isolated gate in IGBT will make it simple for driving BJT charges and thus less power is needed.

IGBT will be switched ON or OFF depending on if its gate terminal is activated or deactivated. A steady positive potential difference across the gate and the emitter will be maintaining the IGBT in the ON state. After removing the input signal, IGBT will be turned OFF.

IGBT Principle of Operation

IGBT needs less voltage for maintaining conduction in the device unlike in BJT. IGBT is a unidirectional device which switches ON in the forward direction. This means that the current will be flowing from the collector to the emitter when compared to MOSFETs which are bi-directional.

Applications of IGBT

IGBT can be used in medium to ultra-high power applications such as traction motor. Large it is also used for handling high current in the range of hundred amperes and blocking voltages of up to 6kv.

IGBTs are also used in power electronic devices like converters, inverters and other appliances which need solid state switching. Bipolars will be available with high current and voltage, though their switching speed is less. In contrast, MOSFETs have high switching speeds though they are expensive.

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