eem2am
Banned
Hello,
We are doing 53W, isolated Offline flyback PFC with L6561 IC.
Vin = 85-265VAC.
Vout = 36VAC
L6561 DATASHEET:
https://www.st.com/stonline/books/pdf/docs/5408.pdf
A similar circuit for us is as figure 15, page 18 of AN1059:-
https://www.st.com/stonline/books/pdf/docs/5956.pdf
However, the Overvoltage protection , as explained on page 3 of the datasheet cannot be used by us, since we are doing PFC in flyback topology, and not boost PFC.
....but we still need overvoltage protection , for cases of sudden load removal.
-Therefore, we are thinking of simply putting a BJT , collector to the pin 2 (COMP pin) and turning this on via an optocoupler which is instantly activated in the case of overvoltage.
-do you think this will be OK?, ...we are basically going ot be grounding the pin 2 via the BJT in the event of overvoltage, and wonder if this is OK?.....
.....or will we destroy the error amplifier like this, by drawing too much current from its output?
We are doing 53W, isolated Offline flyback PFC with L6561 IC.
Vin = 85-265VAC.
Vout = 36VAC
L6561 DATASHEET:
https://www.st.com/stonline/books/pdf/docs/5408.pdf
A similar circuit for us is as figure 15, page 18 of AN1059:-
https://www.st.com/stonline/books/pdf/docs/5956.pdf
However, the Overvoltage protection , as explained on page 3 of the datasheet cannot be used by us, since we are doing PFC in flyback topology, and not boost PFC.
....but we still need overvoltage protection , for cases of sudden load removal.
-Therefore, we are thinking of simply putting a BJT , collector to the pin 2 (COMP pin) and turning this on via an optocoupler which is instantly activated in the case of overvoltage.
-do you think this will be OK?, ...we are basically going ot be grounding the pin 2 via the BJT in the event of overvoltage, and wonder if this is OK?.....
.....or will we destroy the error amplifier like this, by drawing too much current from its output?