An electric supply system and device therefor including an AC adapter for supplying
electric power received from external thereto; a battery being charged with electric
power supplied from this AC adapter and enabled to supply electric power to the
system by discharging the charged electric power; and a controller for controlling
the supply of the electric power to the system from the AC adapter and the battery.
The controller stops the supply of the electric power to the system from the AC
adapter so as to supply the electric power to the system from the battery while
the AC adapter connected to the system is powered off or loaded lightly.
