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IC701
OFF
BIAS
2.8V
Ω
4k
2
FB
5. Overcurrent preventive circuit (primary side)
The current detection resistors (R706 and R707) are connected to the
inverter circuit on the primary side. If any overcurrent occurs on the
primary side, the current of the inverter Q701 on the primary side is
increased. The current is detected by R706 and R707, is passed
through R710 and is input to the overcurrent restrictive terminal (3
pin) of IC701 to turn off Q701 in order to shut down the whole output.
As the method to recover the power supply again, the power input is
turned off again to sufficiently discharge the voltage of C705, and the
power input is turned on (when 9V or less stands at the power termi-
nal 6 pin of IC701).
A time of approx. 1 minute is necessary to discharge electricity from
C705. See Fig. 16.
0.56V
+
3.6V
–
DMAX
–0.17V
3
IS
CS
CT
RT
8
7
1
7V
OSC
REF
+
–
–
–
R
Q
–
S
+
Fig. 18
5 – 25
VCC
6
10µL
UVLO
4
GND
FO-4500H
5
OUT
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