VLA503 Powerex, Inc., VLA503 Datasheet - Page 5

• Manufacturer Part Number: VLA503
• Description: Hybrid Ic Igbt Gate Driver
• Manufacturer: Powerex, Inc.

Powerex, Inc., 173 Pavilion Lane, Youngwood, Pennsylvania 15697-1800 [phone]
VLA503-01
Hybrid IC IGBT Gate Driver
General Description
The VLA503-01 is a hybrid integrated circuit designed
to provide gate drive for high power IGBT modules.
This circuit has been optimized for use with Powerex
NF-Series and A-Series IGBT modules. However, the
output characteristics are compatible with most MOS
gated power devices.
compact single-in-line package design.
mounting minimizes required printed circuit board space
to allow efficient and flexible layout. The VLA503-01
converts logic level control signals into fully isolated
+15V/-8V gate drive with up to 5A of peak drive current.
Control signal isolation is provided by an integrated high
speed opto-coupler. Short circuit protection is provided
by means of destauration detection.
Short Circuit Protection
Figure 1 shows a block diagram of a typical desatura-
tion detector. In this circuit, a high voltage fast recovery
diode (D1) is connected to the IGBT’s collector to moni-
tor the collector to emitter voltage. When the IGBT is
in the off state, V
With D1 off the (+) input of the comparator is pulled up
to the positive gate drive power supply (V+) which is
normally +15V. When the IGBT turns on, the compara-
tors (+) input is pulled down by D1 to the IGBT’s V
The (-) input of the comparator is supplied with a fixed
voltage (V
the comparator’s (+) input will be less than V
it’s output will be low. During a normal off-state condi-
tion the comparator’s (+) input will be larger than V
Rev. 04/07
INPUT
TRIP
Figure 1. Desaturation Detector
AND
DELAY
). During a normal on-state condition
t trip
CE
DRIVE
GATE
is high and D1 is reverse biased.
COMPARE
The VLA503-01 features a
SHUTDOWN
+
R G
V+
G
E
V trip
D1
IGBT
MODULE
The upright
TRIP
CE(sat)
C
E
TRIP
and
.
and it’s output will be high. If the IGBT turns on into a
short circuit, the high current will cause the IGBT’s col-
lector-emitter voltage to rise above V
the gate of the IGBT is being driven on. This abnormal
presence of high V
be on is often called desaturation. Desaturation can
be detected by a logical AND of the driver’s input signal
and the comparator output. When the output of the AND
goes high a short circuit is indicated. The output of the
AND can be used to command the IGBT to shut down in
order to protect it from the short circuit. A delay (t
must be provided after the comparator output to allow
for the normal turn on time of the IGBT. The t
is set so that the IGBTs V
below V
is set too short, erroneous desaturation detection will
occur. The maximum allowable t
the IGBT’s short circuit withstanding capability. In typical
applications using Powerex IGBT modules the recom-
mended limit is 10µs.
Operation of the VLA503-01 Desaturation Detector
The Powerex VLA503-01 incorporates short circuit
protection using desaturation detection as described
above. A flow chart for the logical operation of the
short-circuit protection is shown in Figure 2. When a
desaturation is detected the hybrid gate driver performs
a soft shut down of the IGBT and starts a timed (t
1.5ms lock out. The soft turn-off helps to limit the tran-
sient voltage that may be generated while interrupting
the large short circuit current flowing in the IGBT. During
the lock out the driver pulls Pin 8 low to indicate the fault
status. Normal operation of the driver will resume after
the lock-out time has expired and the control input signal
returns to its off state.
Adjustment of Trip Time
The VLA503-01 has a default short-circuit detection
time delay (t
prevent erroneous detection of short-circuit conditions
as long as the series gate resistance (R
minimum recommended value for the module being
used. The 2.5µs delay is appropriate for most applica-
tions so adjustment will not be necessary. However, in
some low frequency applications it may be desirable to
use a larger series gate resistor to slow the switching of
the IGBT, reduce noise, and limit turn-off transient volt-
ages. When R
of the IGBT will also increase. If the delay becomes
TRIP
TRIP
during normal turn on switching. If t
G
is increased, the switching delay time
) of approximately 2.5µs. This will
CE
when the IGBT is supposed to
CE
has enough time to fall
TRIP
TRIP
delay is limited by
G
) is near the
even though
TRIP
TRIP
delay
timer
TRIP
)
)