flyback feedback
FvM:
"Obviously, it's a simplified transfer function, only valid when certain assumptions come true.One assumption is written on the schematic. It also answers your question regarding L3. It's simply ignored in the feedback transfer function, otherwise it must play a role within."
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.....-Indeed, the inductor L3 does not appear in the transfer function in the Original Post.
However, the derivation of the above transfer function is dependent on the assumption that V(out) is steady DC, but that the voltage at the secondary diode’s cathode is more dynamically changing.
In other words, as explained on page 288 & 289 of Basso’s book, this transfer function assumes that R(LED) is in the so-called “fast-lane” and R(upper) is in the so-called “slow-lane”.
-And the reason that the “fast-lane” is fast and the “slow-lane” is slow is because of the inductor L3.
So , the question is still, does the removal of L3 (ie shorting out L3) result in a different transfer function than the above?……and if so, what will the new transfer function be?
Unfortunately, there is not a book on the face of this planet which tells this.