Abstract: In order to avoid damage to a switching regulator in the event of short-circuiting of a load, and to reduce power consumption, the maximum duty ratio of a PWM type switching regulator is provided with a supply voltage dependency.

Abstract: A charge/discharge control circuit is provided for an electric power source apparatus in which a service life is prolonged. A voltage dividing circuit, an overcharge voltage detection circuit, an overdischarge voltage detection circuit and a control circuit are connected in parallel to a secondary cell which is an electric power source, wherein the control circuit detects a condition of the secondary cell from the overcharge/overdischarge voltage detection circuits and outputs a signal Vs for controlling a power supply to an external equipment and a charge by an external power source and controls a switching element provided in series with the voltage dividing circuit and reduces a current which flows through the voltage dividing circuit.

Abstract: A charge/discharge control circuit has a voltage detector for detecting a voltage level of a secondary cell, a switch connected in series with the secondary cell, and a control circuit connected in parallel with the voltage detector for receiving and processing an output signal of the voltage detector and controlling an impedance of the switch. The voltage detector, the switch and the control circuit are integrated in a single substrate. In a preferred embodiment, the switch comprises an external connection terminal and a second terminal connected to the secondary cell, a first IGFET connected between the first and second terminals, a second IGFET connectected between the first terminal and a substrate electrode of the first IGFET, and a third IGFET connected between the second terminal and the substrate electrode of the first IGFET.

Abstract: A charge/discharge control circuit is provided for an electric power source apparatus in which a service life is prolonged. A voltage dividing circuit, an overcharge voltage detection circuit, an overdischarge voltage detection circuit and a control circuit are connected in parallel to a secondary cell which is an electric power source, wherein the control circuit detects a condition of the secondary cell from the overcharge/overdischarge voltage detection circuits and outputs a signal Vs for controlling a power supply to an external equipment and a charge by an external power source and controls a switching element provided in series with the voltage dividing circuit and reduces a current which flows through the voltage dividing circuit.

Abstract: A charge/discharge control circuit comprises two serially connected electric power sources and two overcharge/overdischarge detection circuits. A control circuit outputs a signal for controlling the charge/discharge of the electric power sources in accordance with signals from the two overcharge/overdischarge detection circuits. An intermediate voltage receiving circuit receives, in accordance with the signal from the control circuit, a voltage at a junction point between the two electric power sources and outputs a signal indicative of a relation of the relative voltage between the two electric power sources.

Abstract: A chargeable power supply which has a charge/discharge control circuit is provided in which the service life of a secondary cell is prolonged. A voltage dividing circuit, an overcharge voltage detection circuit, an overdischarge detection circuit and a control circuit are connected in parallel to the secondary cell. The control circuit receives signals indicating the condition of the secondary cell from the overcharge/overdischarge voltage detection circuits and outputs a signal for controlling a switch circuit for disconnecting the secondary cell from external equipment, or to stop a charging operation by an external power source. The control circuit also controls a switching element provided in series with the voltage dividing circuit and reduces a current which flows through the dividing circuit. A current limiting means is provided to limit the current consumption of the charge/discharge control circuit.