# bode plot DC gain not shwing in boost converter transfer function?

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Dears Sir/madam,

I have designed a boost converter with peak current mode control and I wanted to evaluate the transfer function in bode plot of the Verr to Voutas you can see in the files added the boost converter gives a bode plot without ADC gain meanwhile in the figure added you can see the DC gain when I use the math transfer function and use Matlab to get the bode plot.

I would love to know what I have missed getting the DC gain as the shape of the bode plot is good.?

thank you
asked Apr 13, 2018

## 1 Answer

0 votes
This is not a PLECS problem as the model behaves as expected.
answered Apr 19, 2018 by (245 points)
Hello Kyburz, as you know there must be a DC gain because from its mathematical transfer function there is a DC gain of around 28 dB and in the open loop as well I see the DC gain, so what is the problem? did I simulate it wrong or did I placed the perturbation not correctly? I try almost all cases but DC gain is 0 in the current closed loop. thank you
Please give your mathematical transfer function and explain why the model has this transfer function. Please also explain why the DC open loop gain must match the DC closed loop gain. If the input of the closed loop system is 40 Volt (DC) and the resulting output voltage is 40 Volt (DC), which gain does the system have?
Hi Oliver,

the DC open loop gain must not much the DC closed loop gain but there must be DC closed loop gain as you see in teh tranfer function given by Christophe Basso in his book when s tend to 0.

the DC closed loop gain is between the Vout and Verr=Vref-Vout positioned after the substraction and bofore the PI cntroller
Sorry, but it seems that there is some misunderstanding. If the system had a DC gain other than 0 dB it becomes unstable (for a gain > 0 dB) or the output decays to 0 (for a gain < 0 dB).