3 x Inductance one core

[polfort]

Hello.

I am looking for a Inductor which I want to use in a SEPIC DC/DC Converter.
What I need are thre coils (each 25uH) at one core.
Saturation current and resonance frequency are not exactly specified yet.
After simulating the whole thing with LTspice I_sat turned out the be about 9A.
Not sure if I can lower that current.
I dont how the resonance frequency should be chosen.
My converter works at 600kHz so 2MHz resonance frequency should be ok?

What coils should I look for?


Best regards,

polfort

 

[Kevin Weddle]

The problem with high current inductors is that their XL/R is always inherently low. So the frequency needs to be very high to get good resonant filtering. A series of three inductors would probably still be inadequate. A typical AC to DC power supply doesn't have resonance, and has better perfomance.

Can you give more detail as to the high current and resonance in the DC to DC converter.

 

[polfort]

The high current occurs as high peaks (in simulation).
I think that even if there are onyl small peaks the core could get saturated if I dont choose a proper one.
Have already seen inductors with I_sat about 10A

Maybe I should look for a transformer to have three coils on one core...


I am not sure If I explained the resonance frequency issue well..
By looking after some inductors to fit my requirements I saw resonance frequency as one limiting value among others like I_sat.
I dont really understand how the resonance would affect my cirucuitry..
But I think my system works with frequencies much lower than the resonance frequency of the inductor i would choose, so it must be all right..

 

[Kevin Weddle]

Inductors have a self resonant frequency because of the winding capacitance. I'm not sure why the self resonant frequency is avoided, but it may be because the winding capacitance is equal to a poorly constructed capacitor.