Super User is a question and answer site for computer enthusiasts and power users. It's 100% free, no registration required.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

There are some circumstances where I would like to switch off power to a USB port, but still allow the port to function as normal.

Is it possible to switch off power to a USB port using software settings?


If power to a USB port is turned off, will it still function as normal (ignore devices and functions that require the power usually supplied through a USB port, e.g. external hard drives, charging of phones)?

[edit] Nobody seemed to read the "circumstances" link I had in the original post. So here it is as it relates to this question:
If your notebook is low on power, and you require a connection to your phone (e.g. for tethering to the internet), the connection with the lowest possible power use that I can think of is a USB connection, but only if the phone does not draw power to charge itself.

share|improve this question
Could you clarify abit, why this could be useless? Most devices you input into a USB port is requiring power to operate, the only thing I could think of would be phones tha already had power og an external harddrives with and external power supply. – Patrick Jørgensen Apr 24 '12 at 8:20
Its possible to switch off power, I know this because Zentimo xStorage Manager software can do this after removing a usb device using their software, just don't know how they do it. Would be a nice experiment to see if the communications bus remains active after you somehow disable power. – Moab Apr 24 '12 at 11:14
you may use wifi/bluetooth tethering for that while. I'm not sure if cutting out the outer power pins of usb would leave your phone detected to pc. – d-coder Oct 5 '14 at 15:01
up vote 3 down vote accepted

The simple answer is no, if you remove power to that USB port it will not function as a USB port.

Part of the specification is for power, and all devices plugged into a USB port expect power.

What is it you are trying to achieve? That may help us provide an alternative answer you can use without trying to breach the spec.

share|improve this answer
I've updated my question with a use-case. Since the spec includes power, I'll approach the problem from the other side. It'll be interesting to see if there are ways to prevent a phone from charging when plugged in to a USB port. – chobok Apr 26 '12 at 10:05
@chobok - The phones on the market today do not provide a method to not charge unless they are already fully charged. Its an engineering decision, 99.9% of people want to charge their device, when they plug in the cord. – Ramhound Apr 26 '12 at 12:38

Buy an extra cable, remove the +5v pin (pin 1), give it a try. I bet if the device has its own power it will still work.

share|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.