Boost converter equations

[jayce3390]

How to get the relation giving the output voltage ripple according to C value? and L value?

Thank you very much.

 

[nandrei]

Hello,

I once did a boost converter, from 12Vdc to about 50Vdc, but i don't remember the ecuations. Try searching for "switching mode power supply design guide".

I just wanted to say that in any case you want the output ripple to be as low as possible, for that you will ad an output filter. So the remaining ripple will not depend on the switching elementes (C and L).

Hope this helps
Andrei

 

[jayce3390]

Thank you for the answer.
I don't use any output filter in order to keep bandwidth capability of the boost converter, tha's why I need to optimize the output ripple according to L & C values.

 

[nandrei]

Hi,

I can't find my documents on the subject, i think i gave the disk to somebody.... )

i found this:
https://www.daycounter.com/LabBook/BoostConverter/Boost-Converter-Equations.phtml

They are saying that the ripple current is f(inductor current), so it looks like the ripple voltage would also depend on the R_load.

My math isn't what it used to be, but if you try writing the equations and solve with I_c = C (dv/dt) and V_l = L (di/dt)
eg: for Ton = t2 - t1
i_l = i_c + i_rload
i_l = C (dv/dt) +i_load
.... i used to know how to do this

Andrei

 

[mess123]

Vripple=(L*Ipk^2)/(C * Vout)
Cout= (Iout/Vripple)*Ton