Abstract: To obtain an electric power unit, an electric power controller, and an electric power controlling method that can know a date for starting use of an electric power unit respectively, as well as to obtain a computer that can know a date for starting the use of the built-in electric power unit.

Abstract: In a power supply protection circuit, a FET and a diode are connected to a power line so as to protect an inner circuit from an excessive voltage caused by a device connected to an IEEE1394 bus. A switching circuit connected to the power line turns off the FET when the voltage of a port exceeds a reference voltage, which is lower than the withstand voltage of the inner circuit.

Abstract: An invention to effect charging for a battery pack at the suitable time irrespective of the kind of an installed battery pack. A battery pack detects voltage, electric current, and temperature of an accommodated battery main body. When it is determined that charging for the battery main body is required, the battery pack outputs a charge request signal. Further, when it is determined that the battery main body has been brought into a full-charged state, the battery pack stops outputting of the charge request signal. When the charge request signal is inputted from the battery pack, the charge controller causes a direct current voltage supplied from an AC/DC adapter to be supplied for the battery pack, so as to start charging the battery main body of the battery pack. Further, when the continued inputting of the charge request signal is stopped, and the charging for the battery main body is stopped.