small formfactor DC/DC converter help?

Discussion in 'General Electronics Chat' started by quaker, Nov 11, 2009.

  1. quaker

    Thread Starter New Member

    Nov 11, 2009
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    I want to add a low power uP and a few other components to a board that is plugging directly into the wall. The unit already has a bridge rectifier set up so there is ~160 DC available on the board. And I need to convert that to <100mA at 12V output to run the logic I want to add. I have found one solution,a EHD-RD3323 from panasonic that has very minimal board space but costs $7 which way more than the total cost of everything else on the board. The other solutions I can think of require adding larger transformers. So I was wondering if anyone has a small egligent solution to getting a low power DC source from rectified AC???

    THANKS
     
  2. SgtWookie

    Expert

    Jul 17, 2007
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  3. quaker

    Thread Starter New Member

    Nov 11, 2009
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    Thanks SgtWookie I've actually broken quite a few of those apart looking for a solution but they all seem to be transformer based even the the more exspensive small ones??
     
  4. KMoffett

    AAC Fanatic!

    Dec 19, 2007
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    Check Goodwill or second hand stores. Look for ones that are very light for their current rating compared to the transformer ones. For example a 12vDC@100ma transformer type weighs about the same or more than a 12v@1A SMPS type.

    Ken
     
  5. beenthere

    Retired Moderator

    Apr 20, 2004
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    If
    means obtaining the DC without the use of a transformer, then, no, there is absolutely no acceptable way. That 160 volt source sounds like simply rectified line voltage - any circuit using that source must be considered as a lethal shock hazard. There is no way to safely use that voltage in a circuit.

    We have repeated questions seeking to save money or weight or space by not using a low voltage transformer. Any such circuit cannot be rendered safe to use.
     
    Last edited: Nov 12, 2009
  6. SgtWookie

    Expert

    Jul 17, 2007
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    A transformer is really the most safe way to go. It provides isolation from the mains power, which is very important. It's also quite efficient.

    The buck-type switcher you found is OK, if it is properly fused - but if the internal current switch ever fails shorted, your low-voltage electronics will be fried to a crisp.

    There isn't a safe way to step line voltage down without the use of inductors.

    Discussions of unsafe methods are against the policy of this Board, and are prohibited.
     
  7. quaker

    Thread Starter New Member

    Nov 11, 2009
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    Thanks beenthere I read your policy, and was impressed, and quite agree that I would not want to encourage someone else to play with rectified line voltage because of some stupid little project I have.

    Thanks everyone.
     
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