Lincoln Electric SVM151-A service manual Insulated Gate Bipolar Transistor Igbt Operation

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E-7 E-7

THEORY OF OPERATION

FIGURE E.6 – IGBT OPERATION

POSITIVE

VOLTAGE

APPLIED

	GATE		GATE
SOURCE		SOURCE
n +	n +	n +	n +
p	BODY REGION	p	BODY REGION
n -	DRAIN DRIFT REGION	n -	DRAIN DRIFT REGION
n +	BUFFER LAYER	n +	BUFFER LAYER
p +	INJECTING LAYER	p +	INJECTING LAYER
DRAIN		DRAIN
A. PASSIVE		B. ACTIVE

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INSULATED GATE BIPOLAR TRANSISTOR (IGBT) OPERATION

An IGBT is a type of transistor. IGBTs are semicon- ductors well suited for high frequency switching and high current applications.

Drawing A shows an IGBT in a passive mode. There is no gate signal, zero volts relative to the source, and therefore, no current flow. The drain terminal of the IGBT may be connected to a voltage supply; but since there is no conduction the circuit will not supply current to components connected to the source. The circuit is turned off like a light switch in the OFF position.

Drawing B shows the IGBT in an active mode. When the gate signal, a positive DC voltage relative to the source, is applied to the gate terminal of the IGBT, it is capable of conducting current. A voltage supply con- nected to the drain terminal will allow the IGBT to con- duct and supply current to circuit components coupled to the source. Current will flow through the conducting IGBT to downstream components as long as the posi- tive gate signal is present. This is similar to turning ON a light switch.

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MULTI-WELD 350