Insulated Gate Bipolar Transistor (Igbt) Operation - Lincoln Electric POWER WAVE SVM135-B Service Manual

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SOURCE
n+ n+
P
n-
n+
P+
DRAIN
A. PASSIVE
INSULATED GATE BIPOLAR
TRANSISTOR (IGBT)
OPERATION
An IGBT is a type of transistor. IGBT are
semiconductors well suited for high frequen-
cy switching and high current applications.
Example A in Figure E.8 shows an IGBT in
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 sup-
ply; but since there is no conduction, the cir-
cuit will not supply current to components
THEORY OF OPERATION
FIGURE E.8 — IGBT OPERATION.
GATE
BODY REGION
DRAIN DRIFT REGION
BUFFER LAYER
INJECTING LAYER
POWER WAVE 455/POWER FEED 10
POSITIVE
VOLTAGE
APPLIED
GATE
SOURCE
n+ n+
BODY REGION
P
n- DRAIN DRIFT REGION
n+
BUFFER LAYER
P+
INJECTING LAYER
DRAIN
B. ACTIVE
connected to the source. The circuit is
turned OFF like a light switch.
Example 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 conduct and supply current to the
circuit components coupled to the source.
Current will flow through the conducting
IGBT to downstream components as long
as the positive gate signal is present. This is
similar to turning ON a light switch.
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