Hitachi IGBT Module Application Manual
Figure 2. Structure of IGBT die
Definitions:
C
E
G
Collector
Emitter
Gate
3.4
Symbol and Equivalent Circuit
An IGBT module is essentially a switching transistor controlled by the voltage applied to its gate
terminal. Figure 3 shows the symbol and equivalent circuit of an IGBT module.
Figure 3. IGBT Symbol and Equivalent Circuit
3.5
Operational Switching Description
For IGBT turn-ON, the N-channel MOSFET is turned ON by first applying a positive voltage to gate-
emitter electrode (see Figure 3). As a consequence, all of the MOSFET’s drain current flows as the base
current of the pnp transistor, so this transistor turns ON and the IGBT reaches its ON state.
For IGBT turn-OFF, a zero or minus bias must be applied as the gate-emitter voltage so that the
MOSFET’s current and the base current of the transistor will be cut off, thus causing the IGBT to reach an
OFF state.
Note:
Since an IGBT is comprised of MOSFET and pnp transistor
structures, it is inherently able to reduce its ON state conduction
loss, due mainly to the phenomenon of conductivity modulation.
6
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