High Voltage -> Low Voltage Power Supply

Discussion in 'General Electronics Chat' started by dksoba, Sep 7, 2010.

  1. dksoba

    Thread Starter New Member

    Jan 8, 2010
    25
    0
    So I'm working on a motor driver board. Right now the supply voltage to my board is 24VDC, with a 12V buck converter, and 5V and 3V LDO's for logic stuff. My buck converter is limited to around 40V, which makes me wonder, what if I wanted to use a 60VDC or 100VDC power supply? What type of device would I use to convert a high voltage DC supply, which would be used for the motors, to a low voltage supply (3.3V, 250ma or so)?

    I know I could just use two DC power supplies, which is essentially converting from AC twice with different size transformers, but there must be a way to do this directly from DC.

    Thanks,
    Matt
     
  2. Ghar

    Active Member

    Mar 8, 2010
    655
    72
    You look for a buck converter with a higher input range.
    Generically a "buck converter" just means stepping down voltage, the internals can vary significantly.
     
  3. dksoba

    Thread Starter New Member

    Jan 8, 2010
    25
    0
    Any particular recommendations. There doesn't seem to be many "simple" options over about 36V or 48V inputs. Maybe I'm looking in the wrong place?

    On this page:

    http://www.mouser.com/Power/Power-Management-ICs/_/N-6g7lv/

    I typically look in:

    -DC/DC Switching Controllers
    -DC/DC Switching Converters
    -DC/DC Switching Regulators
    -Switching Converters, Regulators & Controllers

    But don't really find what I'm looking for.

    Matt
     
  4. Ghar

    Active Member

    Mar 8, 2010
    655
    72
    Well you do get into a bit of a specialized application with that input voltage.

    These guys have some converters that would work:
    http://www.vicr.com/cms/home/products/brick/dc-dc_converters

    They're fairly expensive, $100 each or so.

    Looking for these on Mouser isn't very fun, why are regulators and converters different categories, and why are there essentially no filters? Who knows...
    I have some issues with all of these distributors but Digikey has a much better search for these converters as well as Newark.

    There's a lot of parts that go up to 75V or so input.

    For example:
    http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=102-1519-ND

    It just takes a lot of hunting, never stay with one website. Every distributor will have some glaring problems with particular categories and excel at others.
     
  5. schmitt trigger

    Active Member

    Jul 12, 2010
    36
    7
    My feelings indeed.... Mouser is quite difficult to search, with very limited filtering on their search function. More than once, I've gone somewhere else.
     
  6. hobby16

    Active Member

    Aug 30, 2010
    30
    4
    Why not try a $2 ebay USB charger. Most can deliver 5V-500mA and are made of just transistors and a feedback opto so I'm sure they don't mind you apply a 40-100DC instead of 110V AC.

    I've already modified some to output 9V (instead of 5V), never tried 40V DC inputs, but chances are it'll work flawlessly. The ones that may pose problem are with IC (like Topswitch) with brownout detect which would prevent you applying 40V but I've always seen 500mA chargers without ICs.
     
  7. Dyslexicbloke

    Active Member

    Sep 4, 2010
    420
    19
    I dont have anything to offer here ... in fact I have a very simmilar issue and wanted to subscribe to this thread.
    I hav a supply that swings from 12VAC to 120 VAC and I need a 10VDC supply, fortunatly only at a couple of tens of mA
    Looking for anything that might help.
    Al
     
  8. hobby16

    Active Member

    Aug 30, 2010
    30
    4
    @Dyslexicbloke
    Well it might interest you, I'm just trying a USB charger with 12V DC input (instead of 110-220V AC) and I do have clean 5V output (on my scope) with 100R load.
    All remains cool, nothing has exploded yet.
     
  9. hobby16

    Active Member

    Aug 30, 2010
    30
    4
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