Which power supply to use?
December 13, 2018 5:29 PM   Subscribe

I bought a used Samsung soundbar that had the wrong power supply. The specifications says it needs a 19 volt, 15 watt power supply. Ohms Law, I=P/E says the power supply needs to generate 780 milliamperes.

I found a replacement that was 19.5 volts and 4.35 amps. But while I was hunting for a replacement, all of them mentioned a "max" wattage. Does that mean a device only draws as much current as it needs? Or will it deliver the entire 4.35 amps and burn the soundbar to a crisp?
posted by CollectiveMind to Technology (7 answers total)
 
Does that mean a device only draws as much current as it needs?
Yes.
posted by kickingtheground at 5:38 PM on December 13, 2018 [5 favorites]


This should work.
posted by H21 at 5:54 PM on December 13, 2018


Yes, amps listed are max amps available, devices only draw what they need. You cannot fry electronics by providing too many amps: you fry them by somehow giving them the wrong polarity or incredibly wrong voltages, etc.

TLDR; the idea that a power supply can ‘push’ too much current into a modern consumer electronics device is not correct.
posted by SaltySalticid at 5:58 PM on December 13, 2018


SallyScalicid, I learned a long time ago that voltage was "potential" meaning it was a force. Instructors said it pushed itself through wires though I was never clear on how current was different.
posted by CollectiveMind at 6:25 PM on December 13, 2018


If you want to use that hydraulic analogy, as you said, voltage is water pressure. Available current is how much water flows through the pipe, depending on its diameter. But you are hooking that supply pipe to a device that has a much smaller pipe inside. A three inch supply pipe going into a one inch device pipe will only allow one inch of water to flow through it, no matter how large the supply pipe.

So, your power supply will be okay.
posted by JackFlash at 7:03 PM on December 13, 2018 [1 favorite]


Yep JackFlash has it: the hydraulic analogy is your friend.
posted by SaltySalticid at 7:11 PM on December 13, 2018


Thanks, all. The soundbar is humming along happily.
posted by CollectiveMind at 9:20 PM on December 13, 2018 [1 favorite]


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