Strange Gain and Phase waveforms

[treez]

isn't it strange that page 7 of this app note calls it "closed loop gain" (see red line in graph)
https://www.fairchildsemi.com/application-notes/AN/AN-4164.pdf

 

[treez]

open loop gain has to be defined, what parts of the converter does it include.?

the open loop gain , in a psu, i have always taken to mean going through the power stage & modulator, and error amplifier...ie, round the whole loop.

 

[treez]

..ie this..feedback loop diagram for smps....
As far as I know, this is the main one of any interest to a PSU engineer

 

[Easy peasy]

putting a small perturbation on the Vref and looking at the Vout shows you the closed loop response

 

[treez]

thanks, i'm also certain there is an equation for closed loop response which has the open loop expression in it.....its something like 1+alpha.beta/
(1+alpha)...not that , but something like it...where alpha and beta are transfer functions of error amp and power stage, sort of thing.

I am referring to the closed loop of the diagram, 2 posts up, post #23