Insulated Gate Bipolar Transistor (Igbt) Operation - Lincoln Electric INVERTEC CV350-R Service Manual

E-6
n +
p
n -
n +
p +
DRAIN
A PASSIVE
INSULATED GATE BIPOLAR
TRANSISTOR (IGBT) OPERATION
An IGBT is a type of transistor. IGBTs are
semiconductors well suited for high frequency
switching and high current applications.
Drawing A in Figure E-4 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 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.
Theory of Operation
FIGURE E.5 – IGBT OPERATION
GATE
SOURCE
n +
BODY REGION
DRAIN DRIFT REGION
BUFFER LAYER
INJECTING LAYER
INVERTEC
n +
p
n -
n +
p +
DRAIN
ACTIVE
B
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 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.
TM
CV350-R
POSITIVE
VOLTAGE
APPLIED
GATE
SOURCE
n +
BODY REGION
DRAIN DRIFT REGION
BUFFER LAYER
INJECTING LAYER
E-6