E-6

THEORY OF OPERATION

E-6

 

FIGURE E.6 - IGBT

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GATE

 

SOURCE

n +

n +

p

BODY REGION

n -

DRAIN DRIFT REGION

n +

BUFFER LAYER

p +

INJECTING LAYER

 

POSITIVE

 

VOLTAGE

 

APPLIED

 

GATE

 

SOURCE

n +

n +

p

BODY REGION

n -

DRAIN DRIFT REGION

n +

BUFFER LAYER

p +

INJECTING LAYER

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DRAIN

DRAIN

A. PASSIVE

B. ACTIVE

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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.

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.

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NOTE: Unshaded areas of Block Logic Diagram are the subject of discussion

INVERTEC® V205-T AC/DC™

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Lincoln Electric SVM161-A service manual Insulated Gate Bipolar Transistor Igbt Operation, Passive Active