Insulated Gate Bipolar Transistor (Igbt) Operation - Lincoln Electric RANGER 250 SVM150-A Service Manual

E-5
SOURCE
n +
p
n -
n +
p +
DRAIN
A. PASSIVE
INSULATED GATE BIPOLAR
TRANSISTOR (IGBT) OPERATION
An IGBT is a type of transistor. IGBTs are semiconduc-
tors 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.
THEORY OF OPERATION
FIGURE E.5 – IGBT OPERATION
GATE
n +
BODY REGION
DRAIN DRIFT REGION
BUFFER LAYER
INJECTING LAYER
RANGER 250
SOURCE
n + n +
p
n -
n +
p +
DRAIN
B. ACTIVE
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.
E-5
POSITIVE
VOLTAGE
APPLIED
GATE
BODY REGION
DRAIN DRIFT REGION
BUFFER LAYER
INJECTING LAYER