Abstract: In order to provide an overheat protection circuit having a small mounting area, the overheat protection circuit includes: a resistor bridge circuit which includes: a plurality of resistors each having a temperature coefficient; an input terminal; and an output terminal; and a comparator circuit connected to the output terminal and the input terminal of the resistor bridge circuit. Parts are each provided in the vicinity of one of the plurality of resistors each having the temperature coefficient, and the comparator circuit outputs an overheat detection signal when a temperature of one of the parts is equal to or higher than an overheat detection temperature. With this structure, a large number of parts can be protected from overheating by a minimum number of overheat protection circuits. Therefore, a circuit scale becomes smaller, and hence a cost for overheat protection becomes lower.

Abstract: Provided is a battery state monitoring circuit for manufacturing a battery device at low cost, and a battery device including the same. A charge control transistor and a discharge control transistor are structured so as to be operated based on a low-level signal which is based on a ground voltage (VSS) and a high-level signal which is based on a voltage of a voltage regulator, which is lower than a power supply voltage (VDD) based on a voltage of a battery, respectively. Accordingly, in the charge control transistor and the discharge control transistor, voltages applied to gates thereof become low, whereby a low-breakdown-voltage element can be used. This leads to a reduction in cost for the charge control transistor and the discharge control transistor, leading to a reduction in manufacturing cost for the battery device.

Abstract: A charge and discharge control circuit which accommodates pulsed charge and pulsed discharge and can control charge and discharge of a secondary battery with safety, and a rechargeable power supply device having the same built therein are provided. The charge and discharge control circuit includes a delay time switching circuit for shortening a delay time of overcharge detection after charge inhibition is canceled. When overcharge is detected after the charge inhibition is canceled, the charge is inhibited in a delay time which is shorter than a normal delay time of the overcharge detection.

Abstract: Provided is a battery state monitoring circuit which is capable of preventing a discharge leak current from a battery so as to eliminate a load conventionally imposed on a user, including: a battery state detector circuit that detects a state of the battery based on a voltage of the battery; a transmitting terminal that transmits battery state information indicative of the state of the battery to an outside; a receiving terminal that receives battery state information of another battery from the outside; a transistor that is used for transmitting the battery state information, and has any one of two terminals except for a control terminal connected to the transmitting terminal; and a diode that is connected in a direction opposite to a direction of a parasitic diode disposed between the two terminals of the transistor, the diode being disposed between the transmitting terminal and one terminal of the transistor.

Abstract: To provide a PWM switching regulator control circuit, which is small in the ripple voltage without a drop of the output voltage which, is attributable to a load at the time of a soft start. A PWM switching regulator control circuit is provided, in which an offset voltage that is lower than a reference voltage is inputted to an error amplifier at the time of a soft start, to thereby prevent an off-time from occurring in the PWM comparator output, prevent the output voltage that is attributable to the load from dropping, and make the ripple voltage small.

Abstract: The invention provides a power source circuit which is capable of preventing a current from being caused to flow from a battery charger to a secondary battery in the over-charge detection state. In order to cut off a current from a parasitic diode of a transistor having a gate electrode to which a signal to release the over-current state is inputted from a switching-device-controlling logic circuit, a charge and discharge controlling circuit includes a diode connected between the transistor and a current detecting circuit, thereby preventing a current from being caused to flow from the battery charger to the secondary battery.

Abstract: The invention provides a power source circuit which is capable of preventing a current from being caused to flow from a battery charger to a secondary battery in the over-charge detection state. In order to cut off a current from a parasitic diode of a transistor having a gate electrode to which a signal to release the over-current state is inputted from a switching-device-controlling logic circuit, a charge and discharge controlling circuit includes a diode connected between the transistor and a current detecting circuit, thereby preventing a current from being caused to flow from the battery charger to the secondary battery.