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how to get isolated feedback with SMPS

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eem2am

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smps isolated feedback

hello

Page 8 , Figure 1 of LM2587 PWM controller datasheet

**broken link removed**

...shows the comp pin (pin 1)

If i do this isolated, using opto feedback (4N35 & TL431 error amp on secondary side) then how can i connect the opto transistor....can i just put the collactor to pin 1 and the emitter to ground...?
 

Why do you think that pin 1 should be used for feedback purpose? This operation isn't suggested by National in any application circuit, as far as I see. Pin 2 is intended for feedback.
 

hello,

thankyou for your interest, in non-isolated form, pin 2 is for feedback, but when isolated, please see this app note.....(Figure 5, page 4)

**broken link removed**

It is of great mystery to me when it is, and when it isnt possible to go stright to the output of the error amplifier like in this app note.

Any help greatly appreciated....
 

As the National AN answers your previous questions to my opion, also from your other thread, e. g. regarding typical OC pole, which are still left open?
 

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