Inspiron 14 7000, 1080p, i7, touch screen, "black screen" out of warranty

I have an Inspiron 14 7000, 1080p, touch screen,  laptop just over a year old, was working great until one day it boots up but the screen remains black.  All types of maneuvers tried but the screen remains black.  Finally, got a HDMI & connect it to my TV.  The laptop boots up fine & I can see everything works great, even the touch screen movements work normally, on the TV monitor.  So I deduce that the hard drive, mother board, & touch screen are all fine.  It's just the laptop is not feeding the video to the touch screen.  Out of warranty.  Can any one tell me what part controls the video feed to the touch screen & is it difficult or expensive to replace?

thanks,

Joe,