Powering low powered usb device while computer is off - power consumption

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Limp Gawd
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Apr 4, 2013
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Does anyone know if I power a very low power usb device (ie. like a led desk light) from a computer while the computer is off (for many hours everyday) will it be less power efficient than powering the same device from a wall wort?

Or are there any other downsides like wearing out the psu?
 
I'd risk saying that it would be better to use a regular low power LED lamp connected directly to mains power.
With a USB lamp, rated probably at 5V or a bit more, double conversion is required - your PSU has to bump mains down for the mobo, then the motherboard has to produce and output power once more for the USB socket, and who knows - maybe the lamp itself has some circuitry.
 
By wall-wart do Americans mean an adjustable power supply which down-steps voltage and converts it into direct current?
The lamp in question has an USB plug, yes?
If so, then I'd watch for amperage issues - many adapters like that lack in punch (you probably need at least 500mA to have headroom).
If you have access to LED bulbs then I'd go that route. They work from mains voltage thanks to integrated circuitry and all you need is a bulb 'frame'.
 
Jonnyguru and [H]OCP now do 5v standby numbers (including efficiency). I believe most are around 70% efficient, and the 5v standby circuitry is separate from the main 12v circuitry. I would think it is as efficient as any wall adapter, maybe more so due to EU standby power consumption requirements.

The motherboard doesn't do any conversion for 5v power. It gets 5v direct from the PSU (when shut off, directly from the 5v standby line), and outputs it straight out to USB, with a limitation on maximum current (varies depending on motherboard, minimum 500 mA).
 
Easier to buy your own dc power supply on Amazon and run the light.

Wort = liquid to ferment for beer or distilled liquor

Wart = an abnormal yet common skin growth commonly caused by the HPV virus

They are called wall warts... because they are like warts, but on a wall
 
Tsumi said:
(...)as efficient as any wall adapter, maybe more so due to EU standby power consumption requirements.

The motherboard doesn't do any conversion for 5v power.(...)
Click to expand...

Thanks for the heads up

staticlag said:
They are called wall warts... because they are like warts, but on a wall
Click to expand...

That don't scream 5 Volts to me but you're the teacher.
 
Lol yes wall wart. I only just read that term recently.

I used to call them plug packs but no one seemed to use that term and though I was talking about a battery pack.

I suppose wall power adapter is a good term that can't be confused.
 
I'd honestly use the easiest and cheapest option available. You're talking about a grand total of maybe 1 or 2 watts at absolute most per hour. Running that thing, "The less efficient way," would cost you a grand total of $1.05 per year in electricity (assuming 1 watt power savings and $0.12 / KWHR).
 
I call them single phase adjustable mains power adapters with DC rectification.

I have no warts. Good shampoo.
 
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