 Hitachi IGBT Module Application Manual
5.3.3 Gate Driving Loss Calculation
Gate driver circuit power loss can be calculated from an examination of the gate electric charge
characteristics. Figure 27 shows the gate electric charge characteristics (including the negative bias voltage
area) where V
GP
and V
GN
are the positive and negative bias voltage values. Gate electric charge varies as
the value of Q
GO
depends on V
GN
to V
GP
transfer (that is, turn-ON) and V
GP
to V
GN
transfer (that is,
turn-OFF). In this case, Equation 11 can be used to calculate the driver circuit ( P
G
) power (where f
c
represents switching frequency).
Equation 11:
P
G
=( V
GP
+ V
GN
)
!
Q
GO
!
f
c
Note:
Driver circuit power for switching must be supplied by the driver
circuit power supply and is directly proportional to the switching
frequency. Remember to take this fact into account when designing
the power supply circuit.
Figure 27. Driving Voltage and Gate Electric Charge
5.3.4 IGBT Driving Voltage
The IGBT driving voltage needs to set up both positive and negative bias voltages. Lower positive bias
causes increased ON-state loss, and higher positive bias promotes increased short-circuit current. For these
reasons, it is particularly important to always select an appropriate driving voltage.
Note:
A positive bias of 15V Â± 10% and a negative bias of from -5V to -
15V are recommended to prevent misoperation when the other arm
(device) switching occurs.
25
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