ATX computer power supply conversion

Discussion in 'Radio Circuits, Repair & Performance' started by 9M6BZ, Aug 31, 2011.

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  1. 9M6BZ

    9M6BZ Ham Member QRZ Page

    I have modified the atx computer power supply to supply 12v 18 amps for my icom base station radio (IC 2200H) all works fine, but can only get 12v, thats it.. can i add a variable resistor some where on the mother boart to twit the voltage to go around say 14v?
    De: 9m6BZ
     
  2. G4COE

    G4COE Ham Member QRZ Page

    Personally, I'd never use a ATX or similar PSUs on ANY rigs, their regulation and current ripple rating are a lot to be desired! You can't always believe what it say's on the label.... try scoping one at the rated output.

    I would imagine with these power units to 'up' the voltage you would have to alter the 'Feedback loop that regulates the 'ON' time of the chopper transistor or FET, this would alter ALL the supply rails accordingly.

    Here is a schematic of a ATX power supply -:

    http://www.pavouk.org/hw/en_atxps.html.... can't see the link button dunno where it's gone! They all follow more or less the same routine, maybe a different chip here and there etc.

    dave
     
  3. WA9SVD

    WA9SVD Ham Member QRZ Page

    Agreed. The 5.0 Volt bus still controls the regulation feedback loop, and if that can't be changed, there's no hope of increasing the + 12 Volt output bus.
    From the circuit shown, you would need the Data Sheet for the particular regulator chip used in the supply, but you would ALSO have to re-design the "over-voltage protection" (OVP) circuit; it would most certainly trip with a voltage of 13.8 Volts, when it's designed to regulate and sense 12.0 Volts, +/- 10%.
    Your supply may be a bit unusual; most ATX supplies have considerable current capability at 5 Volts and 3.3 Volts, at the sacrifice of lower and lower current ratings for the 12 Volt rail.
     
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