I want to use an old PSU I have for studying electrical engineering; to power my circuits. What will happen if I place a 0.6Ω load on the 12V output of a PSU rated for 10A?

I'm sure the PSU will heat up, but will it deliver its max current or will it blow up?

I could experiment, of course, but I don't want to risk ruining the PSU.

  • 1
    \$\begingroup\$ Depends on the power supply. The PSU data sheet should have something on there about what it does under overcurrent conditions. (If you don't have a manual/datasheet google the part number). For the power supply I have in my lab, if I were to overload it, the output voltage would drop. So if my PSU could only supply 10A and I put 0.6 ohm load on 12V, the output would drop to 6V and the overcurrent LED would light up. Another supply I have at home though shuts off the output if overcurrent occurs. \$\endgroup\$
    – I. Wolfe
    Dec 8, 2015 at 23:00
  • \$\begingroup\$ Does an audio amp protect itself if the speaker impedance is too low? \$\endgroup\$
    – Andy aka
    Dec 8, 2015 at 23:17
  • \$\begingroup\$ @I.Wolfe, thank you! My PSU has overload protection, it shuts down (www.datasheetspdf.com/datasheet/download.php?id=546702). It although says the protection triggers when current exceeds 24A, will PSU be working normally until that current while it says +12V @ 13A on PSU's case? Thank you, your comment suits me as an answer \$\endgroup\$
    – Qeeet
    Dec 8, 2015 at 23:22
  • \$\begingroup\$ It sounds like current limit shutdown protection. So what should happen is under 24A but above 13A it will constant current limit, or the current will stay at 13A and the voltage will fall. When it detects a load equivalent to 23A it will then shut off completely. btw I was unable to use the link you provided, probably need to just share the part number or direct link to pdf \$\endgroup\$
    – I. Wolfe
    Dec 9, 2015 at 2:18
  • \$\begingroup\$ @I.Wolfe, thank you! The link is datasheetspdf.com/PDF/FSP250-60ATV/546702/5 \$\endgroup\$
    – Qeeet
    Dec 9, 2015 at 12:02

1 Answer 1


If it's a simple linear power supply it will probably either blow a fuse or overheat, break and possibly burn down your house, since most don't have active overtemperature or short circuit protection, altrough some do. This type can be recognized by the heavy transformer it inevitably contains, whose purpose is to step down the mains voltage to about 12V.

The tranformer inside a 12 V 10 A linear power supply probably looks similar to this:

Switching mode power supplies have become ubiquitous in recent years, since they are lighter, more compact and more energy efficient. A switching mode power supply usually has a somewhat "intelligent" control circuit that has features like short circuit protection and over temperature protection. Such a power supply will probably shut down to protect itself if you try to draw too much current. Keep in mind that the absolute cheapest power supplies from e.g. eBay are always built down to a price and in some cases lack any sort of protection.
Switching power supplies replace the chunky tranformer with a smaller, high frequency tranformer driven by transistors:


It depends completely on which type of power supply you have, and you should check if it has overtemperature and short circuit protection.


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