Is it possible to control the power in a USB port?

Question

I wonder if it's technically possible to lower/increase the output power of a USB port?

I am skeptic myself, but I ask to be sure.

Define "possible". What are the constraints? I mean you could of course change output power by attaching another power source to the port. — davmac, May 04 '11 at 02:49

score 3 · Answer 1 · answered Jan 20 '15 at 21:58

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As mentioned above, yes. To get more than 500mA (USB 2.0), use a combiner cable to parallel two or more USB ports. These cables are very common as they are used by external USB hard drives to get the required current.

answered Jan 20 '15 at 21:58

Steve175

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score 1 · Accepted Answer · edited May 23 '17 at 12:31

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I believe the USB spec allows for different power load states. Initially a device is supplied 100mA. Once a device can handshake with the USB controller and perform a certain request, the controller can supply a "high load" current of 500mA. Check this related SO question for more details.

edited May 23 '17 at 12:31

Community

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answered May 04 '11 at 02:50

jmkeyes

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score -1 · Answer 3 · answered Dec 18 '13 at 13:42

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It is Not Possible..Because USB already provides techniques to reduce the Power level while it connected with USB Port.There will be 3 states.

1.POWERED

2.SUSPENDED.

During suspended state it emit only less power..So it is not needed to control the output power of the USB externally..USB itself offers for Better Power Utility

answered Dec 18 '13 at 13:42

Sundar

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_There will be 3 states._ Where's the third one? – rpax May 06 '14 at 17:04

Is it possible to control the power in a USB port?

3 Answers3