hi everybody.

I'm a beginner at building power supplies so please help me out. I've been reading up on Type III compensation networks and Bode plots primarily from this source:

http://www.intersil.com/data/tb/tb417.pdf

I'm trying to graph the equations in excel and i'm plugging in the values from their example provided on page 8.

So far i've been screwing up dismally. Most of my plots don't match their plots.

First I can't seem to make my open loop gain plot match their plot. I'm using the equation from figure 4 (pg1). I converted the frequency to radians, logged the equation and multiplied by 20 to get a decibel plot. My plot has the same shape and slope as their plot (their plot on page 9) but mine is vertically shifted by -70 decibels. I must have really screwed up somewhere.

And that's not the worse part, i tried plotting the phase equations for the type III compensation network (located on page 7) and my phase plots are nothing like their plots.

i've taken into account that excel uses radians instead of degrees and did the proper conversions for the phase plots but they're still messed up.

Also i can't seem to locate their "phase modulation" term, anyone know what the equation for this term is?


Recap of what i can and can't get:

The only plots i could reproduce accurately are the Compensation phase plots, the system gain plots, the modulator & filter gain plots, and the compensation plots.

Everything else i'm stuck.

i've included my spreadsheet in case you want to go over the equations yourselves, i mess of stuff in the columns to the right are my "fixes" to get around the problem of excel giving arctan results in both positive and negative numbers at the wrong instance.

Thanks advance

SAVE ME!!!! SAVE ME!!!! SAVE ME!!!!

P.S. Anyone know of a similar source of information as the above article but hopefully with more explanations as to how they derived their equations and more examples?

Attached Files

compensation_design.xls (73.0 KB, 30 views)