Theory of operation, Insulated gate bipolar transistor (igbt) operation – Lincoln Electric POWER WAVE SVM173-A User Manual

Page 45

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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
connected to the drain terminal will allow the IGBT to
conduct and supply current to circuit components cou-
pled to the source. Current will flow through the con-
ducting IGBT to downstream components as long as
the positive gate signal is present. This is similar to
turning ON a light switch.

E-11

E-11

THEORY OF OPERATION

POWER WAVE 455M/MSTT

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FIGURE E.9 – IGBT OPERATION

DRAIN

SOURCE

GATE

INJECTING LAYER

BUFFER LAYER

DRAIN DRIFT REGION

BODY REGION

p +

n +

n -

p

n +

n +

DRAIN

SOURCE

GATE

INJECTING LAYER

BUFFER LAYER

DRAIN DRIFT REGION

BODY REGION

p +

n +

n -

p

n +

n +

POSITIVE
VOLTAGE
APPLIED

B. ACTIVE

A. PASSIVE

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