So I was simulating a boost converter on plecs, wanted to calculate Gvd. Firstly I solved the model by hand and drew the bode plot, then I drew the schematic on plecs, made sure of the values and parameters are equal to what I designed by hand. my issue is that my dc gain that I calculated by hand is twice that got drawn by plecs. I made sure of my calculations by referring to this to make sure that I made no mistake. my calculations are equal to the model presented here.

Model
this is the schematic on plecs. D = 0.5


Schematic
This is the average Dc output voltage.

And this is the bode plot of the converter.

Gvd
As you can see, the dc gain is about Vinput/(1-D), instead of Voutput/(1-D).
I really hope that this is not a dumb question and itsnot a silly mistake of mine since I spent too much time working and searching what did I do wrong :S.
Thanks

 

Your FET is drawn upside down....

Here's the LTSpice equivalent, D = 0.5, f=100kHz
I'm not sure how you're generating your bode plot



Close up of 1 cycle @ steady-state

 

Your FET is drawn upside down....

Here's the LTSpice equivalent, D = 0.5, f=100kHz
I'm not sure how you're generating your bode plot

View attachment 248491

Close up of 1 cycle @ steady-state
View attachment 248493

Hello Sir, thanks for replying and I hope I am not wasting your time.
Plecs has an intrinsic small signal model generator analysis. My time domain analysis lies inline with my hand written calculations, but the bode plots are not..
I tried another schematic which is already drawn in my book, the issue is always the Gd0 or the low frequency gain, its always lower that whats expected to be.
Again thanks for your time .

 

Understood, LTSpice also has a small signal analysis capability. Confusingly you talk about DC gain but a Bode plot is an AC analysis. So what are your input and output signals?

 

Pleased to see your question as I think I have the same question, I am also confused and in need of light on this same issue. Need help.

<Mod: link deleted.E>

 

Understood, LTSpice also has a small signal analysis capability. Confusingly you talk about DC gain but a Bode plot is an AC analysis. So what are your input and output signals?

Hi, sorry for the confusion, I meant with the dc gain is that low frequencies gain, its written in books as Gd0. I just fixed it and it was a pwm issue. Thanks for yout time

 

Pleased to see your question as I think I have the same question, I am also confused and in need of light on this same issue. Need help.

<Mod: link deleted.E>

Hi budd, can you please email me at <Mod: Deleted email address, avoid Spam.E>

 

Hi, sorry for the confusion, I meant with the dc gain is that low frequencies gain, its written in books as Gd0. I just fixed it and it was a pwm issue. Thanks for yout time

No problem.

BTW, that other message was an advertising Bot, not a real person...