Drop voltage about 1v for 2amps

Discussion in 'General Electronics Chat' started by stoopkid, Jun 6, 2012.

  1. stoopkid

    Thread Starter Member

    Mar 3, 2011
    136
    1
    I really want to use this DC-DC converter (I cannot find any comparable ones,5v 3A, for such a price) for a project but I may be receiving voltages up to 14.5v and it's limit is 13.8. Can I use a diode or something to drop the voltage by 1v? Or even 2v would be better. According to it's efficiency chart I don't suspect the input will ever sink more than 2A. I am also not worried about the voltage being too low, I'm only getting 5v out of it and with that voltage drop I still shouldn't ever go below 11-12v. There's lots of different kinds of diodes and I really only know much about zeners, which would be best for this, or should I do something completely different?

    Calculating its power dissipation would simply be voltage drop*max amperage, correct? What if I also used a 13v or 13.4v zener to protect the input, how would I calculate what it would dissipate? How many amps would be flowing through it if it was sinking extra voltage to ground?

    Thanks
     
  2. absf

    Senior Member

    Dec 29, 2010
    1,490
    371
    That part also appears in my local element 14 (Farnell) catalog. Looks like a good substitute for 7805 at that price. I would order a few to try them out myself soon.

    Your suggestion of adding 2 1N5404 diodes before the switcher should work I presume. Only problem might be the tiny transformer might get too warm when the current exceeds 1 or 2A at the output side. Let me know if it is working well enough for you.....Thanks.:)

    Allen
     
  3. stoopkid

    Thread Starter Member

    Mar 3, 2011
    136
    1
    Why would the diode cause it to get warm?
     
  4. absf

    Senior Member

    Dec 29, 2010
    1,490
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    Not the diodes but the current would causes the transformer to get warm. If you are taking 1A or less from that SMPS it should be fine.
     
  5. stoopkid

    Thread Starter Member

    Mar 3, 2011
    136
    1
    It says that it doesn't require a heatsink. At close to 3 amps would it get too hot to operate? There's a chart showing it delivering 3A at 85c. Should I try to affix a heatsink?
     
  6. absf

    Senior Member

    Dec 29, 2010
    1,490
    371
    Sorry, you're probably right.:p I didnt turn to the end of the pdf and just judging from the size of the ferrite transformer. Looks like the efficiency is also better at higher current than when it was at 0.5A. And lower Vin has better performance than higher Vin too.

    Allen
     
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