Panasonic FX-55 Series Operating Instructions Manual page 25

The screen automatically turns off after :
10 minutes (when AC adaptor is connected) of inactivity
4 minutes (when operating on battery power) of inactivity
*1
The computer automatically enters sleep after :
10 minutes (when AC adaptor is connected) of inactivity
4 minutes (when operating on battery power) of inactivity
*1 : Refer to "Sleep/Hibernation Functions" about resuming from sleep.