To power USB on when the laptop is turned off:-
Power in the USB port is live when the laptop is off, it is useful for charging the cellphone/smartphone battery, or other, without having to turn on the laptop. In other words, the laptop can function as a Power Bank.
Not all laptops/notebooks or netbooks have this USB power-sharing facility, and generally, laptops that have this facility are still disabled or not enabled.
To find out if your laptop supports USB power-sharing when the laptop is shut down, and activate it (if any) if you want, the way is by entering the BIOS and looking for a menu that is related to USB power.
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To enter the laptop BIOS, by restarting the laptop or turning it on from the dead position. A few moments after restarting, before loading the Operating system, we quickly pressed the escape key, F1, F2, or something else depending on the brand of the laptop.
After being on the BIOS page, look for options regarding USB Power sharing.
There are several different terms for USB power-sharing depending on the brand and BIOS of the laptop. there are USB sleep and Charge, USB Charging, USB Power Share, and others.
If there is a choice on your laptop and want to activate it, just select Enable (usually press F5 / F6 to enable/disable) then save.
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Example of some BIOS displays from different laptops to set USB power share:
Thank you for reading.