In android provides power button for turn off and turn on device. Some cases if your power button is not responding or you have broken power button then you face problem to power off or power on.
If you're in this situation, there are two possibilities: you're phone or tablet is powered on but you can't wake it up or it's switched off and you can't boot it up. We'll look at both these problems individually below.
How to turn on phone without power button: Switched off
If you have a broken power button and you're device is switched off then you're in a tricky position but there is some hope. Different methods will work depending on the make and model of your device so we're making no guarantees.
The first and easiest thing to try is to plug your phone into the charger in case the battery is depleted. Some phones may even switch on this way but it's unlikely so try long pressing the volume buttons in case a boot menu appears.
With some charge in your battery, preferably 5 percent or more, (the screen should show the percentage even if it's off) try unplugging it from the mains charger and connecting to a PC or laptop via USB. We've tried this with a Motorola Moto G and it booted up instantly.
A third option if you happen to have enabled USB debugging before the device switched off is to use a command prompt. Install ADB and open a command prompt window (instructions can be found in our how to install Android Lollipop guide). Once you've done so, with your phone plugged into the computer type 'adb reboot' and hit enter.
How to turn on phone without power button: Switched on
If you're lucky enough to have a device which is still switched on but the power button is broken then things are a lot easier. For starters don't let you phone or tablet run out of charge and therefore power off.
With some phones, like Samsung Galaxy’s and iPhones, a broken power button isn't too much bother because the physical home button below the screen will wake it up. You might also be able to double tap to wake depending on the device you have. Most smartphones don't use physical keys so there's no way of waking it up.
There are various things you can do to wake up your phone without using the power button. Try simply plugging it into a charger or getting someone to ring you. If you have a physical camera button use this to launch the camera app then quit out.
Not all these methods are convenient ways to wake up your phone with no power button so once you have gained access you'll want to install an app which will help you wake the device up. Remember you'll still need to stop it running out of juice.