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Opto-Coupler pole in SMPS feedback

Opto-Coupler pole in SMPS feedback

Opto-Coupler pole in SMPS feedback

(OP)
Hello,

On page 12, 13 and 14 of AN1059  application note they do the feedback compensation for the L6561 flyback power factor corrector circuit.

****AN1059 Flyback PFC application note.
http://www.st.com/stonline/products/literature/an/5956.pdf


However, considering the equation at the bottom of page 14 (H(s)),  or any other  transfer functions listed, -None of them include the effect of the opto-coupler pole.

Also, the diagram at figure 15, (top of page 15) does not show the opto-coupler pole equivalent capcitor which should appear accross the Collector-Emitter of the opto transistor.




In relation to this,  -pease may I quote from Basso's book,  page 322.........

- - - - - - - - - - - - - -- - - - - - -- - - - - - -- - - - - - -- - - - - - -- - - - - - -
"Compensating the power supply without keeping in mind the opto-coupler pole position is useless. Always measure or compute the pole position and include it in the loop design process to avoid last-minute bad surprises"
- - - - - - -- - - - - - -- - - - - - -- - - - - - -- - - - - - -- - - - - - -- - - - - - -


The AN1059 application note clearly has taken no account of the opto-coupler pole.

Do you know how this can be so?

Thankyou very much for reading.
 

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