For the Inspiron 11 3147 computer, shut down the computer. Then turn on the computer and keep pressing F2 until the BIOS screen appears. Then go to the Advance tab. Find
USB wake support and enable it. Save the BIOS setting and exit. Start up windows. Now you can close the lid of the computer to enter sleep mode and still keep charging your phone via USB.
============= OR TRY ============
Here are the steps to get your external device (USB) charged even when the computer is in sleep mode:
a. Click Start -> in the start search field type: Device Manager, press enter.
If you are prompted for access either press continue or supply the necessary username and password.
b. When Device Manager opens, expand the Universal Serial Bus controllers category.
c. Here you will see several USB Root Hub listings, for each right-click and select Properties.
d. In the properties window, click Power Management.
e. Uncheck ‘Allow the computer to turn off this device to save power’, click OK.