The power delivered over USB port keeps the external USB device powered on even if the system is turned off. I need to unplug the AC adapter to turn all the power off.
LastUpdate : Mon, 07 Mar 2016
Answer
Because in BIOS default, Wake on LAN (WOL) under AC mode is ON, this feature needs continuous power from system, and USB port power sync with Wake on LAN feature, therefore the USB port power is always ON.