Abstract: A charge and discharge circuit that reduces the power consumption at charging and discharging without shortening the life of secondary batteries is described. The charge and discharge circuit includes charge current control circuits connected in parallel to the secondary batteries for performing bypass control of a charge current supplied to the secondary batteries. A potential difference detection circuit detects a voltage difference between the secondary batteries and controls the charge current control circuits in accordance with the voltage difference to selectively bypass the charge current supplied to the secondary batteries.

Abstract: A discharge control circuit that securely prevents an over discharge of a battery. The control circuit includes a discharge control switch connected to the battery for cutting off a discharge current of the battery in response to a discharge stop signal. A control circuit is connected to the battery and the discharge control switch generates the discharge stop signal for deactivating the discharge control switch when a voltage of at least one cell reaches a lower limit. The control circuit includes a switch holding circuit for continuously supplying the discharge stop signal to the discharge control switch for a predetermined time after the discharge stop signal is generated regardless of the cell voltage.

Abstract: A charge/discharge control circuit for controlling charging and discharging of a secondary battery that includes a cell. The charge/discharge control circuit includes an overdischarge detection circuit for detecting an overdischarged state of the battery, and an overcharge detection circuit for detecting an overcharged state of the battery. A discharge control switch is deactivated in the overdischarged state. A first charge control switch is deactivated in the overdischarged state. A second charge control switch is activated in the overdischarged state. A current-limiting circuit is connected in series with the second charge control switch for limiting the charging current when charging is performed.

Abstract: A discharge control circuit that securely prevents an over discharge of a battery. The control circuit includes a discharge control switch connected to the battery for cutting off a discharge current of the battery in response to a discharge stop signal. A control circuit is connected to the battery and the discharge control switch generates the discharge stop signal for deactivating the discharge control switch when a voltage of at least one cell reaches a lower limit. The control circuit includes a switch holding circuit for continuously supplying the discharge stop signal to the discharge control switch for a predetermined time after the discharge stop signal is generated regardless of the cell voltage.

Abstract: One end of a resistor R1 is connected to a charger detection terminal OCV and the other end of the resistor R1 is connected to a base terminal of an NPN type bipolar transistor Q2 of open collector structure to thereby supply a driving bias current. An emitter terminal of the transistor Q2 is connected to a reference potential and a collector terminal of the transistor Q2 is connected to a gate terminal COUT of a charge control P type FET 204. Not only the resistor R1 but also a collector terminal of an NPN type bipolar transistor Q1 of an open collector structure is connected to the base terminal of the transistor Q2. An emitter terminal of the transistor Q1 is connected to the reference potential and an overcharge control signal from an overcharge control circuit 231 is connected to a base terminal of the transistor Q1.