Hitachi IGBT Module Application Manual
Figure 42. Control Signal, Driver Voltage, and IGBT Collector Voltage Waveforms
Because the dead time ( T
D
) of the logic circuit deviates due to delays ( t
1
and t
3
the driver output voltage and switching delays ( t
2
and t
4
) in the IGBT modules, this situation results in a
real dead time referred to as T
D’
(see below):
Definitions:
t
1
Output delay time between ON control signal and ON drive voltage
t
2
Output delay time between ON drive voltage and IGBT turn-ON
Output delay time between ON control signal and OFF drive voltage
t
3
t
4
Output delay time and OFF drive voltage and IGBT turn-OFF (provided that, in
each of the above cases, there is no difference between the top and bottom
arms). The relationship between the dead time ( T
D
) set on the logic and
that of a real dead time ( T
D’
) between IGBT and CE are expressed by
Equation 28:
T
D’
= T
D
- (t
3
+ t
4
) + (t
l
+ t
2
)
Thus, the dead time ( T
D
) of the logic circuit changes with the magnitude of the delay times t
1
through
t
4
and results in a real dead time ( T
D’
).
The next section examines and verifies delays ( t
l
and t
3
) on the driver line and delays ( t
2
and t
4
) in
the IGBT modules.
38