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Thread: Running on undervoltage

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    Default Running on undervoltage

    Just out of interest; what would happen if one ran a voltage regulator, in this case a power supply at under voltage, say 50V. Would it try its best and perhaps burn out the rectifying diodes due to excessive current or is there a shut down mechanism?

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    Quote Originally Posted by ashiekh View Post
    Just out of interest; what would happen if one ran a voltage regulator, in this case a power supply at under voltage, say 50V. Would it try its best and perhaps burn out the rectifying diodes due to excessive current or is there a shut down mechanism?
    It will shut down.

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    I know there is over voltage and current monitoring of the secondary side, but when was monitoring of the primary side introduced?

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    Quote Originally Posted by ashiekh View Post
    I know there is over voltage and current monitoring of the secondary side, but when was monitoring of the primary side introduced?
    What happens during a brown out?

    Charge of bulk cap takes over until power is restored, assuming it's restored while the bulk cap is still charged.

    What happens when the bulk cap no longer has a charge or can be charged? The PSU shuts down.

    It's not "protection", per say. It's just in the design.

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    Come to think of it... I have taken some PSUs rated at 110V down to 90V and had them blow up.

    But 99% of the time, they shut off. Just like how a lot of 230V only PSUs will shut off below 190V. Theoretically, the can RUN at 110V input (but at lower power), but they're often designed not to.

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    ashiekh (01-19-2020)

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    I was thinking of the guy with the video card

    http://www.jonnyguru.com/forums/show...rving-quot-GPU

    that if it were fed too low a voltage would the voltage regulator try to compensate.
    Last edited by ashiekh; 01-19-2020 at 02:15 PM.

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    Oh.. I thought you were talking about AC input.

    Graphics cards have had BIOS's that "know" the input voltage for quite some time.

    I guess that's what you get for posting under PSUs and not "theory" or "hardware". ;-)

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    Actually I didn't want to give the video card guy the idea that he might have caused the damage, so I rephrased it in terms of power supplies, expecting to learn something new; and I did, that some supplies blow at 90V as well as that video cards know about their input voltage.
    Last edited by ashiekh; 01-19-2020 at 02:14 PM.

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