I ran LG monitor as 2nd monitor off my laptop for a long time then it started going into analog power mode also. I did what forums said nothing worked, cables fine so know it had to be a settings problem. Figured out my solution
Control panel-->appearance-->Display--> screen resolution
noticed resolution was at 1366*768, but it was grayed out so I couldn't change it.
Set multiple displays to extend
Clicked display drop-down box to 1. mobile PC display
Changed the resolution to 1024*768
Changed display back to 2. Generic Monitor
And screen popped up on 2nd monitor per usual