Inductor for Buck converter

Discussion in 'General Electronics Chat' started by Dritech, Dec 5, 2015.

  1. Dritech

    Thread Starter Well-Known Member

    Sep 21, 2011
    Hi all,

    I am going to implement a buck converter that will step-down a 14V input supply to 10V at 2A.
    From my calculation I determined that the required inductor value should be 3.3mH.
    I found the following inductor on eBay which is listed as "Toroidal chokes 2.2 mH 250 Vac 2.3A Coil Wire Wrap Toroid Inductor Choke".
    Will this inductor work for my application if I connect two in series? Also, since I am working with DC and the mentioned inductor is labelled as 250Vac, will it still work?

    Any kind of help would be highly appreciated.
  2. MikeML

    AAC Fanatic!

    Oct 2, 2009
    You must be running your smps at a very low frequency to requires such a large inductor?
    Have you tried any of the design aids for buck converters offered by Linear or TI? You will find that their solutions come up with inductors that are a few uH, not mH.
    Dritech likes this.
  3. AnalogKid

    AAC Fanatic!

    Aug 1, 2013
    The part is described as intended for noise filter applications. Without knowing your switching frequency and pulse width we can't be specific, but generally speaking I think it is not the right part for your job.

  4. dl324

    AAC Fanatic!

    Mar 30, 2015
    Chokes are typically used for noise suppression and wouldn't work well in a switching regulator.
  5. DickCappels


    Aug 21, 2008
    Besides that, the peak current through the inductor will be considerably larger than the average current, and in this case a 2.5 amp inductor will not be sufficient for a 2.0 amp average current.

    I think you will find this application note from Texas Instruments to be a lot of help:
    Dritech likes this.
  6. Dritech

    Thread Starter Well-Known Member

    Sep 21, 2011
    Thanks for the replies. I will use the design aid from TI to determine a smaller value.
  7. spinnaker

    AAC Fanatic!

    Oct 29, 2009

    Those TI chips are really easy to use. But if you get stuck there are a number of built buck converters on eBay that should suit your needs.
  8. takao21203

    AAC Fanatic!

    Apr 28, 2012
    Lm2596 and doesn't need a large inductivity. I think the delta voltage is important which is just a few volts, and you need higher inductance for larger delta voltage.

    2.2mh is unusual for small buck converters.

    If you put in series dc resistance will double.