Efficent Buck (DC-DC) convertor

Discussion in 'The Projects Forum' started by skybox, Aug 19, 2009.

  1. skybox

    Thread Starter Active Member

    Mar 2, 2009
    68
    1
    Hi guys,

    I was wondering if anyone has any recommendations for an IC that does DC-DC conversion. I posted a similar thread yesterday but looking for any recommendations now. Apparently the regulator I look at yesterday (LM317) consumes more power than is required for the design.

    Design requirement: Convert 12Vdc to 3.0 to 3.6 Vdc. Current max should be about 1A.

    If anyone has any recommendations, it would be greatly appreciated! :)
     
  2. skybox

    Thread Starter Active Member

    Mar 2, 2009
    68
    1
  3. n9352527

    AAC Fanatic!

    Oct 14, 2005
    1,198
    4
    It is a good device. Recommended.
     
  4. skybox

    Thread Starter Active Member

    Mar 2, 2009
    68
    1
    Yea I might be going with this. I have to see how big the inductor value it recommends is (150 uH) as I have very little space for the height and width of components.
     
  5. skybox

    Thread Starter Active Member

    Mar 2, 2009
    68
    1
    Yep, inductors are too big. Looked at the recommended inductors from the spec sheet and the height of most of them is 11-13 mm. The max height of my components on this design is limited to 6 mm! Damn!
     
  6. skybox

    Thread Starter Active Member

    Mar 2, 2009
    68
    1
    How about the LM2653? It requires more parts, but through the inductance calculations via the spec sheet, I would need an inductor around 17 uH with a 1.5A output and .45A ripple current.
     
  7. bertus

    Administrator

    Apr 5, 2008
    15,649
    2,348
    Hello,

    You could also look at the MAX1967.

    Greetings,
    Bertus
     
  8. skybox

    Thread Starter Active Member

    Mar 2, 2009
    68
    1
    Thanks Bertus. Looked at the chip. Inductor values still come out a little too big for my design. I looked at the LM27341 and it might work out great. With its design calculations, I'll only need a 1.5 uH inductor and it uses its own internal SYNC clock at 2 MHz, which lowers the size of the inductor
     
    Last edited: Aug 19, 2009
  9. skybox

    Thread Starter Active Member

    Mar 2, 2009
    68
    1
    Here is the spec sheet
     
  10. Tahmid

    Active Member

    Jul 2, 2008
    344
    25
    Hi skybox,
    For efficient design, you use switching power supply. LM317 is very simple but extremely inefficient. I have attached a simple switching buck regulator with L4976 from ST with input from 8v to 55v and output 3.3v 1a.
    You could also look at LM2575 from National.
     
  11. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
    5,699
    907
    Check the National site again. It offers Simple Switchers that work at higher frequencies and use smaller inductors. I have used the LM2678, which works well at over 3A with just 22 uH.

    As for inductors, Coilcraft (such as the 5040H series) and Coiltronics (Cooper Bussmann) make some pretty small inductors suitable for up to 3A or so. At 1A, I suspect they have some that are even smaller. If your power needs are not continuous, you might even go smaller and tolerate the heat.

    John
     
  12. skybox

    Thread Starter Active Member

    Mar 2, 2009
    68
    1
    Thanks guys. I will be using the LM27341 in my final design, it fits my design specifications well.

    I did go with an inductor from Coilcraft. I'll need a 1.5 uH for my design and Coilcraft has some nice, shielded inductors that are only 3.8 mm in height! Works out perfectly.
     
  13. skybox

    Thread Starter Active Member

    Mar 2, 2009
    68
    1
    That 260 uH inductor is going to be huge, probably around 12-15 mm. Thanks though. Check out my design if you are curious on what I chose.
     
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