Q: Lcd light goes out while using

Hi, kamal117.  

Thank you for visiting Apple Support Communities.  

It sounds like the proximity sensor will engage or the display will sleep when in use.  Here is some information that I would take a look at for these issues.  

Screen

Get help with the screen on your device if it has any of these issues:

• The screen is too dim, too bright, or you see only faint images
• You see a solid color screen (black, white or blue)
• You see lines, missing sections, discoloration, or poor image quality

Get help with other screen issues:

• You have a cracked or shattered screen on your iPhone
• Your screen doesn't respond to touch
• Your screen doesn't rotate
• You notice that some pixels are bright, dark, or it looks like there's debris in the screen

Issue not solved

If you still have an issue with your device, contact Apple Support.

Get help with hardware features on your iPhone, iPad, and iPod touch

Cheers