What is IGBT? The principle of IGBT
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What is IGBT? The principle of IGBT

Posted Date: 2024-01-24

IGBT is the abbreviation of Insulated Gate Bipolar Transistor, which is an insulated gate bipolar transistor. It is a power semiconductor device that combines the advantages of MOSFET and bipolar transistor and can operate under high voltage and high current conditions, so it is widely used in the field of power electronics.

Compared with MOSFET, IGBT has lower driving voltage and higher switching speed, and has the forward conduction capability of bipolar transistor, so it can withstand higher current and voltage. At the same time, IGBT also integrates the insulated gate control function of MOSFET, which can achieve safer and more reliable control.

IGBT usually consists of a PN junction and an N channel, with three ports: collector, emitter and gate. When a forward voltage is applied to the gate, a PNP-type structure is formed, which polarizes the PN junction between the collector and emitter, thereby turning on. When the forward voltage is no longer applied to the gate, the PNP junction will return to the open circuit state and the IGBT will stop conducting.

The work of IGBT can be divided into four main stages:

Off state (off state): When no voltage is applied between the gate and emitter, the IGBT is in the off state and no conduction current flows. In this state, the PN junction between the collector and emitter of the PNP bipolar transistor is forward biased, so it is in a conductive state.

Turning on the transition state: When a forward voltage is applied to the gate, electrons in the insulating gate layer between the gate and emitter form a conducting channel. The conductive channel formed can control the current between the collector and emitter of the PNP bipolar transistor, causing it to start conducting.

On state (conduction state): After turning on the transition state, if sufficient forward voltage is applied between the collector and emitter, the PNP bipolar transistor will enter the saturation region, and at this time the IGBT is in the conduction state, allowing Electric current flows.

Close transition state: When the forward voltage is no longer applied to the gate, the conductive channel is closed, the PNP bipolar transistor returns to the cut-off region, the IGBT enters the off state, and current cannot pass.

IGBT combines the advantages of MOSFET and bipolar transistor, with low voltage control characteristics (MOSFET) and high current driving capability (bipolar transistor). It has lower switching losses and higher switching speed, making it suitable for high-frequency applications. At the same time, due to the use of an insulating gate layer to isolate the gate and other parts, the insulation performance and reliability are improved.


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