Keep Screen On Free is a screen-time utility app for Android devices. This app will let you control your device's screen-time settings, and it will also let you turn off the screen when your device is in sleep mode or when you close the application. This is a free app that can be downloaded on Google Play. 

How to Use the App

To keep the screen on, just choose your desired option from the three available options, and click the “Start” button.

To turn off the screen, just choose the “Exit All” option.

To set a custom screen-time, you can use the “Custom” option, and enter your desired value.