VLA500-01
Hybrid IC IGBT Gate Driver +
DC/DC Converter
Powerex, Inc., 200 E. Hillis Street, Youngwood, Pennsylvania 15697-1800 (724) 925-7272
7Rev. 2/08
voltages. When R
G
is increased, the switching delay
time of the IGBT will also increase. If the delay be-
comes long enough so that the voltage on the detect Pin
30 is greater than V
SC
at the end of the t
trip
delay the
driver will erroneously indicate that a short circuit has
occurred. To avoid this condition the VLA500-01 has
provisions for extending the t
trip
delay by connecting a
capacitor (C
trip
) between Pin 29 and V
EE
(Pins 21 and
22). A curve showing the effect of adding C
trip
on time
is given in the characteristic data section of this data
sheet. The waveform defining trip time (t
trip
) is shown
in Figure 3. If t
trip
is extended care must be exercised
not to exceed the short-circuit withstanding capability
of the IGBT module. Normally this will be satisfied for
Powerex NF and A-Series IGBT modules as long as the
total shut-down time does not exceed 10µs.
Adjustment of Soft Shutdown Speed
As noted above the VLA500-01 provides a soft turn-off
when a short circuit is detected in order to help limit the
transient voltage surge that occurs when large short
circuit currents are interrupted. The default shutdown
speed will work for most applications so adjustment is
usually not necessary. In this case C
S
can be omitted.
In some applications using large modules or parallel
connected devices it may be helpful to make the shut-
down even softer. This can be accomplished by
connecting a capacitor (C
S
) at Pin 27. A curve showing
the effect of C
S
on short circuit fall time (t
1
, t
2
) is given
in the characteristic data section of this data sheet. The
waveform defining the fall time characteristics is shown
in Figure 3.
NO
START
IS
V
CE
> V
SC
IS
V
CE
> V
SC
IS
INPUT
SIGNAL
ON
SLOW SHUTDOWN
DISABLE OUTPUT
SET FAULT SIGNAL
WAIT t
timer
IS
INPUT
SIGNAL
OFF
YES
NO
DELAY
t
trip
YES
YES
YES
YES
YES
NO
NO
CLEAR FAULT
SIGNAL
ENABLE OUTPUT
Figure 2. VLA500-01 Desaturation Detector
10%
50%
-5V
90%
t
1
10V
10V
t
timer
t
trip
V
O
(PIN 23)
FAULT SIGNAL
(PIN 28)
SHORT CIRCUIT
PROTECTION
TIMING
DIAGRAM
(PIN 30 OPEN)
t
2
Figure 3. Adjustment of t
trip
and Slow Shutdown Speed
