vla504 Powerex, Inc., vla504 Datasheet - Page 5

• Manufacturer Part Number: vla504
• Description: Hybrid Ic Igbt Gate Driver
• Manufacturer: Powerex, Inc.

Powerex, Inc., 173 Pavilion Lane, Youngwood, Pennsylvania 15697-1800 [phone]
VLA504-01
Hybrid IC IGBT Gate Driver
General Description
The VLA504-01-01 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. The VLA504-01 features a com-
pact single-in-line package design. The upright mount-
ing minimizes required printed circuit board space to
allow efficient and flexible layout.
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 com-
parators (+) input is pulled down by D1 to the IGBT’s
V
a fixed voltage (V
tion the comparator’s (+) input will be less than V
and it’s output will be low. During a normal off-state
condition the comparator’s (+) input will be larger than
Rev. 04/07
INPUT
CE(sat)
. The (-) input of the comparator is supplied with
Figure 1. Desaturation Detector
AND
DELAY
t trip
TRIP
CE
DRIVE
GATE
is high and D1 is reverse biased.
). During a normal on-state condi-
COMPARE
SHUTDOWN
+
R G
V+
G
E
V trip
D1
The VLA504-01
IGBT
MODULE
C
E
TRIP
V
into a short circuit, the high current will cause the IGBT’s
collector-emitter voltage to rise above V
though the gate of the IGBT is being driven on. This
abnormal presence of high VCE when the IGBT is
supposed to be on is often called desaturation. Desatu-
ration 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
output to allow for the normal turn on time of the IGBT.
The tTRIP delay is set so that the IGBTs Vce has
enough time to fall below V
switching. If t
tion detection will occur. The maximum allowable t
delay is limited by the IGBT’s short circuit withstanding
capability. In typical applications using Powerex IGBT
modules the recommended limit is 10µs.
Operation of the VLA504-01 Desaturation Detector
The Powerex VLA504-01 incorporates short circuit pro-
tection 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
out. The soft turn-off helps to limit the transient 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 VLA504-01 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 switch-
ing of the IGBT, reduce noise, and limit turn-off tran-
sient voltages. When RG is increased, the switching
delay time of the IGBT will also increase. If the delay
TRIP
and it’s output will be high. If the IGBT turns on
TRIP
TRIP
TRIP
) must be provided after the comparator
) of approximately 2.5µs. This will
is set too short, erroneous desatura-
TRIP
during normal turn on
timer
G
) is near the
) 1.5ms lock
TRIP
even
TRIP