determine core, windings and L for choke in SMPS

[wcorten]

Hi all,

I`m creating an SMPS that will convert 12Vdc to +-30Vdc.
Now I found all previous discussion concerning this kind of SMPS but I miss an explanation on how to calculate the chokes that ar e placed in series with the input and the chokes that are placed in the outputs.
I want to know what kind of core-size I need. (I will use torroid ferrite)
and how many windings or inductance the coil needs to have.
(switching frequency is 50kHz and output current is 6amps per rail)

At the input the choke is needed to filter out the pulses coming from the SMPS to the source supply and on the outputs the chokes are needed for a better DC with lower ripple. So basicly two times for energy storage. When it comes to capacitors it is easy, take as much C as you have, the more the better, is this the same case for the L or is the C-L combination important ?

Thanks for helping me out.