Abstract: An over discharge protection circuit for a rechargeable battery which prevents an over discharge of the battery in response to a current operating condition, even though the operational state of an electric/electronic apparatus is changed for the purpose of saving the power consumption. The over discharge protection circuit comprises a selector selecting a threshold voltage in response to the operating condition of the electric/electronic apparatus; a comparitor comparing the output terminal voltage of said battery with the threshold voltage selected by the selector; a switch opening or closing a power feed line along which the battery is powered; and a controller controlling the switch in response to the comparison result by the comparitor.

Abstract: Disclosed is a battery charger that can be connected in series to a power feed line, which lies between an external power source and an electric/electronic device, and that monitors the power consumption state of the electric/electronic device and begins and halts the charging of a battery in consonance with the power consumption state.Since a battery charger according to the present invention can be inserted in series into a power feed line that lies between an AC/DC adaptor and an electric/electronic device, the wiring arrangement is not complicated and a spare battery can be automatically charged. Since the charging is performed only during a period in which power consumption by the electric/electronic device is relatively low, the charging operation does not affect the system operation. As the battery charger does not require AC to DC conversion circuit, it is compact and light and is suitable for use along with a portable device.

Abstract: To make it possible to supply to a battery a charging current having a sufficient capacity which enables a short-time charge while supplying a drive current for usual operation to a battery operable electronic device, without making construction large-sized and complicated.The present invention is intended to be able to delicately vary a charging current of a battery according to the variation of power consumption of load on an electronic device, by providing constant power feedback control means for performing feedback control of the outputted power so as to cause a constant power or a nearly constant power, based on a current feedback value and a voltage feedback value.