Your tv may shut off automatically if no activity is found on the remote control or on the tv itself. This is a option that can be turned on or off in settings. Typically, after 4 hours and no activity means you fell asleep or walked away from the tv.
1 
Hi,
Please confirm the model number of the TV?
The device you selected is a monitor and not a TV i.e. it cannot receive TV signals.
Also it is powering off i.e. power light turns off or does it just lose the picture but the power light stays on?
由 jayeff 完成的
My tv picture is ulta
由 Savej 完成的
@savej reply to the comment i left on your original post
由 daniel 完成的