NE5562D Philipss, NE5562D Datasheet - Page 21

• Manufacturer Part Number: NE5562D
• Description: Switched-mode power supply control circuit
• Manufacturer: Philipss

Philips Semiconductors
Figure 35 shows an actual OC1 charging cycle for continuous fault
current sensed at Pin 14 and a DLY = 1 F.
BULK-SENSE AUXILIARY COMPARATOR WITH
SHUTDOWN
This circuit is intended to act as an automatic low-line detection
mechanism. As shown in Figure 35, a voltage divider is connected
from the main unregulated DC supply to Pin 12. The lower divider
resistor may be a potentiometer of 5-10k resistance with
center-tap connected to Pin 13. The comparator which senses Pin
12 voltage is referenced to 3.80V and Pin 12 divider voltage must be
greater than this voltage by a sufficient margin to operate within the
prescribed low-line limits. For instance, if a line voltage drop of 25%
is considered the shutdown threshold, then V
for a nominal operating voltage as shown in Figure 35.
When the line voltage drops more than 25%, the output stage is
disabled. With the hysteresis connected as shown and the pot
THE OUTPUT DRIVE STAGE
The output stage contains the power NOR inhibit gate, invert logic
function, and source-sink drivers. The driver stage is capable of
sourcing and sinking 100mA at frequencies up to 600kHz. The
output transistors are Schottky clamped to prevent saturation and
the resultant switching delay due to stored charge. A 2.5 current
sense resistor in the emitter of Q419 serves to drive active clamp
Q427 when the output sources more than 200mA. This places a limit
on the peak current available during instantaneous charging of a
1994 Aug 31
Delay Time
Total cycles shutdown
Switched-mode power supply control circuit
=10.7ms
(3.6 X 10
C
13 x 10
DELAY
=4280
16
10.7 X 10
8
2.5 x 10
)(3.86V)
6
A
25k
6
3
V
Z
12
should be calculated
3.80V
Figure 36. Bulk-Sense Comparator
BULK
SENSE
COMP
21
1.5V
26k
18k
adjusted near midway, the line voltage will have to exceed V
before the supply will restart. The hysteresis control may then be
calibrated for the desired over-excursion before restart. This
prevents unstable circuit chatter.
The reset switch provides a means for resetting the shutdown latch
after overcurrent faults have charged C
also provides a discharge path for the delay capacitor. Figure 36
shows internal circuit.
power MOS FET gate. This feature protects the output stage from
inadvertent catastrophic overload.
When sinking current, the output is clamped to a maximum of 1.4V.
Output swing for positive output is typically V
sourcing. Rise time for a 2000pF load at Pin 19 is typically 160ns
with a fall time of 80ns.
The power NOR gate provides a fast response inhibit function to
shutdown the output in the event of a number of different fault
26k
36 A
Figure 35. Bulk-Sense Comparator Divider
N BIAS
BULK
SENSE OUT
12
13
NE/SE5562
BULK
SENSE
HYSTERESIS
+V
SENSE IN
S
BULK
12
13
++
V
R
POTENTIOMETER
R
BULK
A
B
RESET
DLY
V
BULK
to its trip threshold. This
S
NE/SE5562
R
-1.9V at 100mA
R
2
1
Product specification
HYSTERESIS
ADJUST
SL00423
SL00422
NOMINAL