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Maximum Current Supply

Discussion in 'General Electronics Discussion' started by Proschuno, Aug 1, 2011.

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  1. Proschuno


    Aug 1, 2011
    I've noticed that on almost all voltage supplies, it mentions the voltage, but then they usually mention maximum current capacities; since these aren't 'ideal' voltage sources, what would happen if the resistance was decreased to the point this current limit was reached?

    I know this is an extremely vague question, but what would commonly happen, say with ac/dc adapters? Any other examples I would also like to know
  2. daddles


    Jun 10, 2011
    It depends on the source you're using. A typical constant voltage/constant current lab power supply that I have on my bench will just reach its rated or set current and refuse to put out any more current. Wall warts that I've tested beyond their rated current will usually put out more current, but the regulation can be poorer and the noise can be high. I haven't tested them to failure or shut-down, so I can't say specifically what will happen. But probably one of three things: 1) they self-destruct (unlikely), 2) some protection circuit shuts the thing down, or 3) they refuse to give any more current.
  3. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    I guess the major thing that happens is that when a power supply can't supply more current, the voltage has to drop.

    If this causes an overload that destroys the PSU (a possibility) then the failure mode is largely undefined. It is possible that you could end up with a higher voltage and higher current!
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