Instructions
Turn on your PS3 console and a controller and navigate to the ̶0;PlayStation̶1; menu. Select ̶0;Settings.̶1;
Scroll down the list of system settings until you reach ̶0;Power Save Settings.̶1; Click it to open the menu.
Select the ̶0;Off̶1; option under ̶0;System Auto-Off̶1; and then press the ̶0;Back̶1; button.
Confirm the settings change when prompted and then resume the activity you were planning to do. Your PS3 will now turn off only when you select the shutdown command manually.