Hi,
Thanks for reaching out. This could be an issue with the video drivers, video card or the LCD itself. We can try few troubleshooting steps to isolate the issue.
Please connect an external desktop monitor to the laptop and switch the display on to the external monitor. When the screen blanks out on the LCD, check if the same happens on desktop monitor.
Uninstall video drivers and components from Programs and Features and Device manager. Restart the system. Install latest video drivers available from the Dell support site. (Display adapters in Device manager will list the video card model)
Run LCD BIST (Built In Self Test) This article gives instructions to run LCD BIST and resolve LCD display issues: http://dell.to/15MXGPv