UC3827-1: Design Review: 140W, Multiple Output High Density DC/DC Converter

Hi,

The below is from a reference design which can help answer your questions.

Unless you can ask more questions so we know where to help, I think your support need is resolved.

Hello,
the center tap of the trasnformer has no capciatnce there and it is always shorted to ground or Vin, the VCT as output voltage and bulding a compensator around it did not help at all. the compensator always had a gain of .100 dB or around that, can you explain more how this can be the solution ?

on the other hand, when I used Vout with type 2 compensator for the outer loop ( Vout )  and inductor current ( inner loop ) now I have a tight regulation at DC and at AC: I was doing peak current control and I want to try avearge current control and see which control behviour gives better results.

this reference design you mentioned up, do there exist a PDF with details of the design steps ?

Thank you for your support! and sorry if my reply was late.

I was following an article called Average current mode control of switching power supplies.I can't see what is happening in the IC. but I believe it would be similar to the picture below. I got the transfer function of CA and wanted to put the pole and zero one octave below and after the crossover frequency. unfortunately I have my current loop compensator in negative magnitude and looks wired. I don’t know if this should be related to the poles and zeros of VA. Any ideas ?

attached you will find my schematic and results, I was expecting the current loop compensator to start high and go low and stay constant for a bit and then go low again because of the pole, I am speaking about the bode plot.
I changed teh AC source place to put it before VIL and got the last result.

Hello, all the transfer functions I have look as expected except this one I showed above. I am trying to see the effect of current sense amplifier on my output voltage Vo1, VIL is the current in the inductor modelled through a sense resistor and a gain modulator. what is it that you don't understand, I can try to explain.

how can I do that ?

I tried as you said, what I find wired is that, I don’t expect the transfer function to be like this but like a type 2 compensator. changing Vin, Rsense, Gain doesn't do many changes. I am starting to suspect the simulation engine here ( Simterix). does this behaviour look normal to you ?

so I should simulate a transient voltage to the input of the op amp ? how to judge the output if it is as it should ?

unfortunately I cant see anything like that in time domain.

I tried a pulse and triangle wave with 50% duty cycle and 500k frequency.

Hi, my problem was that I did not take the voltage after AC source as the input to bode. when I did this I dont get that anymore. now I think the design work but I would say with a lucky punch. I am still struggling to know the correct technique or design steps how to adjust both loops the current loop and then the voltage loop. I will search for more literature in that topic and come back with a concrete question. thanks for your support and sorry for any disturbances.