Thanks...
Do you agree, page 6 of the document
“Practical Feedback Loop Design considerations for switch mode power supplies” is in error?
Practical Feedback Loop....
…..I am referring to equation (18) of page 6, ie, the value “Km = delta IDSpk/delta VEA”.
This “Km” value occurs in the Power stage transfer function of the BuckBoost in equation (21) of the same page.
However, the equation (18) is nonsense. So too is the diagram below it in figure (10).
The “Modulation Gain” that’s being referred to should actually be “R/Ri”
Where:
R = Load resistance
Ri = Current sense resistor in source of FET.
There is usually another gain associated with the modulator (actually an attenuation), which is the factor by which the “VEA” error amplifier output voltage is divided down before it is taken into the PWM comparator. Usually a factor of 0.25 or so. However, the page does not actually mention this.
The document TN-203...(at the bottom of page 9, for buckboost...)
“Voltage mode, current mode (and hysteretic control)”, as follows
https://www.microsemi.com/document-...tage-mode-current-mode-and-hysteretic-control
..Gets the Modulation gain correct, they however, for whatever reason, call the Sense resistor, the “RMAP” …ie, the “PWM ramp voltage divided by the ramp current”…….this is Ohms Law, and is in fact the sense resistance , Ri.
However, they unfortunately don’t make any reference to the gain (attenuation) involving the dividing down of the error amplifier output voltage.
Do you know why none of these papers can “call a spade a spade”?