f) Two internal high precision TL431 shunt regula-

tors are built-in. It provides stable referencevoltages

with a voltage precision of 1.6%.

SUPERVISORY CIRCUIT OPERATION

The system power ON/OFF logic is generated by

the PC, which is ”Low” in system ”On” condition and

”High” when the system is ”Off”. This is connected

to remote pin 7.

The IC’s internal logic circuit generatesa control sig-

nal on pin 6. In normal operation, when there is no

over voltage or over current at the three inputs, the

voltage on pin 6 follows the Remote pin 7 voltage,

i.e. if the remote pin 7 is low the pin 6 is also low or

vice versa.

When fault is detected on the inputs, control pin 6

goes ”High”. This control pin 6 output can be used

to turn off the Mains Power Supply during fault con-

dition. An optocoupler is connected directly, with

cathode connected to the IC pin 6 and anode to

5V (from STDBY supply).

In normal operation the voltage on pin 6 is (opto

cathode) is around 3.7 V. On the primary side the

opto transistor collector is pulled through a resistor

to Vref.

It is required to invert the signal before connecting

to the feedback compensation pin 6 of L5991A for

reverse logic. i.e during normal operation the com-

pensation pin is not affected and during fault condi-

tion the pin is pulled Low. Slight delay (R34,C32) is

introduced on the primary side to avoid fault turn on

condition.

Note : Once the fault conditi on is removed, it is required to

reset the Remote pin to make the system functi on again.

TSM111

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