Feedback Compensation in SMPS

[fethiyeli]

Hi, i would like to ask about feedback compensation. How do u get the bode plot that is needed for feedback compensation ? We have two choices as i know, one of them is to use network analyser and second one is simulations. I am using Orcad and PSIM for SMPS but it is almost impossible to get bode plot. Is there any easier way to get bode plot ? I would like to implement feedback compensation network correctly.

 

[treez]

to get bode plot, use equations in basso book "switch mode power supplys".
If yoU measure in lab, use AP300..by rayridleyengineering.

Bode plot, as you know, does not tell all, you still need to do transient response tests, as the bode plot will not tell you what happens if the error amplifier saturates, such as in no load, or when suddenly hit from no load to full load transient.

 

[FvM]

Did you realize that you don't get a correct bode plot from a SMPS circuit in AC analysis? Some circuit analyzers have special simulations modes covering the AC behaviour of switching circuits, e.g. SIMetrix. Another option is to derive a continuous time equivalent circuit for the pwm modulator and output stage and use it in a standard AC simulation.

 

[treez]

do you mean that the equations on pages 226 to 234 of basso's book are inaccurate?

 

[FvM]

I'm referring to circuit simulation in AC analysis.

 

[treez]

the equations on pages 226 to 234 of basso's book contain the "s" operator, so I assumed they were "AC analysis"?

...but I agree that is not the simulator