after you click the power options
left hand collumm
pick choose what happens when i close lid, then click the choice "nothing"
also
then click change display options
you will be presented with timer choices .. for battery operation and plugged in operation
when done click save then exit/close window
on mine for plugged in i set turn off display at 30 minutes
and shut down PC at never
so when i go off to bed or walk away from it, it still keeps doing whatever task i left running, either downloading some file or processing some video