-Click with the right mouse button on an empty location on your Desktop and choose for “Display Settings” in the context menu.
-Navigate to “Power & sleep” and thereafter click in the right pane on “Additional power settings”.
-Navigate in the next screen to “Determine the behavior of closing the lid”.
-Check the settings “Action when I close the lid:” on battery and DC current level.
-Make sure that for both levels the setting “Take no action” has been selected.
-In case “Sleep mode” or any other setting has been selected (other then “Take no action”),then the external screen(s) will indeed turn off.
-Choose for “Take no action” and click on “Save changes”.
You are now able to close the lid of the Laptop and the external screen(s) will remain active.