Page 1 of 2 12 LastLast
Results 1 to 10 of 11

Thread: DC - DC convertor

  1. #1
    Join Date
    Sep 2010
    Location
    Utrecht The Netherlands
    Posts
    721

    Default DC - DC convertor

    Just thought it would be interesting to share this.
    I have a blue 1 W which has a driver that powers the laser (analog) and feeds the tec cooler.
    For 1 W output i have to supply 5.75 Volts.

    At the moment i use a 5 V power supply which can be adjusted +/- 5% with a potentiometer but this is not enough to supply the needed voltage.

    Since i also have +12V and +/-24V availlable i thought of the following solution.

    There is a dc - dc converter availlable for about 12 euros

    Type number : OKR-T/6-W12-C
    http://nl.mouser.com/ProductDetail/M...sBJ0tQnQ%3d%3d


    I have 12 V and need 5,75 (V out)

    According to the datasheet the formula is:

    R trim (K ohm) = 1,182 / (V out - 0,591)

    (5,75 - 0,591) = 5,159

    R trim (K ohm) = 1,182 / 5,159 = 0,2291 K ohm = 229 ohm

    So if i put two E24 resistors in parallel

    240//4k7 = 228,3 ohm

    240//5k6 = 230 ohm

    This could be a solution to my needs.

    Agreed? Suggestions?Click image for larger version. 

Name:	okr-t3-w12.pdf 
Views:	44 
Size:	470.4 KB 
ID:	25643


    Michel
    Utrecht
    Netherlands

  2. #2
    Join Date
    Feb 2011
    Location
    Knutsford, UK
    Posts
    286

    Default

    If your powering a blue & TEC with this make sure 3A is enough...... What does the TEC pull?

  3. #3
    Join Date
    Nov 2009
    Posts
    57

    Default

    I would just select a common R value that gives you >5.75V rather than trying to get that exact value. 220 ohm should do it.

  4. #4
    Join Date
    Jan 2007
    Location
    Florida
    Posts
    4,382

    Default

    Dropping from 12 to 5.75V @3A will give you 18.75 Watts which exceeds the device's design limit unless I missed something.

  5. #5
    Join Date
    Feb 2011
    Location
    Knutsford, UK
    Posts
    286

    Default

    Thats my point - while OK for just the blue I doubt it can do the TEC at the same time as most tecs are quite current hungry.

    Quote Originally Posted by steve-o View Post
    Dropping from 12 to 5.75V @3A will give you 18.75 Watts which exceeds the device's design limit unless I missed something.

  6. #6
    Join Date
    Jan 2007
    Location
    Florida
    Posts
    4,382

    Default

    Maybe a buck converter. Those are pretty efficient, and come in various flavors.

  7. #7
    Join Date
    Apr 2010
    Location
    San Francisco
    Posts
    215

    Default

    Quote Originally Posted by steve-o View Post
    Dropping from 12 to 5.75V @3A will give you 18.75 Watts which exceeds the device's design limit unless I missed something.
    The module he linked is a step-down buck converter, not a linear regulator. Take a look at the datasheet.

    It's rated for 6A output but 30W max, so at 5.75V out you'd not want to pull more than 5A or so. Whether that's enough depends on your particular TEC.

  8. #8
    Join Date
    Jan 2007
    Location
    Florida
    Posts
    4,382

    Default

    I didn't say that it was a linear regulator. I stated that the design parameters might be exceeded and the device might fail the needs of the application, depending on the power requirements.

  9. #9
    Join Date
    Sep 2010
    Location
    Utrecht The Netherlands
    Posts
    721

    Default

    i will measure the current at 5V to see how much the tec and driver need.

    Michel

  10. #10
    Join Date
    Apr 2010
    Location
    San Francisco
    Posts
    215

    Default

    Quote Originally Posted by steve-o View Post
    I didn't say that it was a linear regulator.
    Uh, the calculation you gave ((Vi - Vo) * I = Pd) is only applicable to linear regulators.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •