If you notice that the screen of the Samsung Galaxy S6 is always on or illuminated during charging, then this is a very high probability at the following setting:
- Stay awake
When "stay awake" is activated, then the Samsung Galaxy S6 does not enter standby mode during charging. To deactivate "stay awake" in Android, you must navigate to the developer options. This works as follows:
- Go to Menu --> Settings --> Developer Options
- Search for the option "Stay awake"
- Remove the check box to disable the function
Now when you connect your Samsung Galaxy S6 to the charger, then the smart phone will after a while switch to stand-by mode and the screen will automatically go out.
So now you know why your Samsung Galaxy S6 has not switched into the stand-by during charging and left the screen lighted up.