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Thread: Powering DC-DC PSu

  1. 05-07-2002, 11:33 AM #1
    phil.45
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    Powering DC-DC PSu

    I built a DC-DC PSU based on the Sproggy design using the same IC`s, it seems to work fine and outputs the correct voltages, but when I connect it to the MB, and use the 12vline of a 300w AT PSU to power the DC-DC PSU, the AT supply just clicks constantly on and off.

    I am worried that something is wrong and dont fancy connecting it up to a high amperage car battery. What are peoples opinions on this?
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  2. 05-07-2002, 11:58 AM #2
    mp3z24
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    what is the 12v line on the at power supply rated at?

    you are probably trying to pull to many amps from the AT supply which cant handle the high current draw. hooking it up to a car battery will give it high current and most likely solve your problem..

    take a look at the sticker on the side of the supply that tells you the current ratings for each line...if your supply is putting out low amps on the 12v line then i would say that is the problem!

    ~mike
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  3. 05-07-2002, 12:09 PM #3
    phil.45
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    20amp at 12v, which does seem quite hefty. Should my DC supply really be drawing THAT much?
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  4. 05-07-2002, 12:31 PM #4
    mp3z24
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    more than 20 amps... probably not. what were you using to test it? hooked up to the same piwer supply, but without a load on the sproggy...

    are you just trying to power up the mobo? or do you have a bunch of stuff on there.

    is it the same as a sproggy, or is it of your own design based on the sproggy?

    im stuck on ideas right now!! sorry

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  5. 05-07-2002, 04:01 PM #5
    CrazyLittle
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    Originally posted by phil.45
    20amp at 12v, which does seem quite hefty. Should my DC supply really be drawing THAT much?
    That sounds really fishy to me, even for a 300w PSU
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  6. 05-08-2002, 03:30 AM #6
    phil.45
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    Originally posted by mp3z24
    more than 20 amps... probably not. what were you using to test it? hooked up to the same piwer supply, but without a load on the sproggy...

    are you just trying to power up the mobo? or do you have a bunch of stuff on there.

    is it the same as a sproggy, or is it of your own design based on the sproggy?

    im stuck on ideas right now!! sorry

    ~Mike
    Yeah, it was plugged into the same PSU, only without a load to test the voltages. Its a sproggy design without 3.3v line. Im just powering up MB(with Cyrix 333 cpu) Hard drive, and graphics card.

    That sounds really fishy to me, even for a 300w PSU
    Do you think the 20amp @ 12v is a lie?
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  7. 05-08-2002, 09:13 AM #7
    mp3z24
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    20A might be a little high... but i know 300W ATX supplys are 15A or so on the 12v, so for an AT supply you might have 20A...

    anyway, do you have the inline fuse on the 12v supply line for the sproggy... that is a 10A fuse so you SHOULDN'T be pulling more than 10A peak on a normal sproggy or everyone's inline fuse would be blowing. im talking about the inline fuse mastero included in his kit, if you built your own kit you might not have a fuse on the 12v feed wire.

    is this the exact same circuit as the sproggy?

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  8. 05-08-2002, 11:13 AM #8
    phil.45
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    Having looked at a few other PSUs I see they are all around 8-10amp on the 12v line, so I think that mine is wrong on the label. I will add a 10amp fuse in line and connect to a car batt.

    Does anyone know what the "average" current draw for a sporggy design would be?
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  9. 05-09-2002, 08:13 PM #9
    MP3DUB
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    The AT psu might not like the huge drain on only the 12vdc rail with out any draw on anything else. You might try loading the 5vdc rail to see if it helps.
    -Nick

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