Lincoln Electric 11141 Service Manual page 45

E-7
INSULATED GATE BIPOLAR
TRANSISTOR (IGBT)
OPERATION
An IGBT is a type of transistor. IGBT are semiconduc-
tors well suited for high frequency switching and high
current applications.
Example A in Figure E.6 shows an IGBT in passive
mode. There is no gate signal, zero volts relative to the
source, and therefore, no current flow. The drain termi-
nal of the IGBT may be connected to a voltage supply;
but since there is no conduction, the circuit will not sup-
ply current to components connected to the source.
The circuit is turned OFF like a light switch.
SOURCE
n +
p
n -
n +
p +
DRAIN
A. PASSIVE
THEORY OF OPERATION
FIGURE E.6 – IGBT
GATE
n +
BODY REGION
DRAIN DRIFT REGION
BUFFER LAYER
INJECTING LAYER
POWER WAVE
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 con-
duct and supply current to the 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.
SOURCE
n + n +
p
n -
n +
p +
DRAIN
B. ACTIVE
® 355M/405M
E-7
POSITIVE
VOLTAGE
APPLIED
GATE
BODY REGION
DRAIN DRIFT REGION
BUFFER LAYER
INJECTING LAYER