Charging and discharging control circuit and charging type power supply device
View Patent ↗Provided is a charging and discharging protection circuit realizing low current consumption in an overcurrent detection state, easy calculation of an automatic return impedance, and high usability. A pull-down circuit for pulling down an overcurrent detection terminal to a VSS terminal is connected in series between the overcurrent detection terminal and a switching circuit. The switching circuit is connected in series between the pull-down circuit and the VSS terminal.
1. A charging and discharging control circuit for monitoring one of a voltage and a current of a secondary battery to control a connection between an external terminal and the secondary battery, comprising:
an overcurrent detection circuit for monitoring a voltage at an overcurrent detection terminal to detect an overcurrent state;
a control circuit for controlling the connection between the external terminal and the secondary battery based on an output from the overcurrent detection circuit;
a pull-down circuit connected with the overcurrent detection terminal, for connecting the overcurrent detection terminal with a VSS terminal at a predetermined resistance value in the overcurrent state, the pull-down circuit comprising:
a resistor; and
a first N-channel transistor comprising a drain coupled to the overcurrent detection terminal and a source coupled to the resistor;
a charger connection detection circuit connected with the overcurrent detection terminal, for detecting whether or not a charger is connected with the external terminal; and
a switching circuit controlled in response to an output from the charger connection detection circuit, the switching circuit comprising a second N-channel transistor comprising a source coupled to the resistor of the pull-down circuit and a drain coupled to the VSS terminal, wherein the resistor is connected between the sources of the first and second N-channel transistors.
2. The charging and discharging control circuit according to claim 1 , wherein the first N-channel transistor further comprises a
gate connected with the control circuit.
3. The charging and discharging control circuit according to claim 1 , wherein
a source voltage and a substrate voltage of the first N-channel transistor and a source voltage and a substrate voltage of the second N-channel transistor are equal to one another.
4. A charging type power supply device, comprising:
an external terminal connected with one of a load and a charger;
a secondary battery which is chargeable and dischargeable and connected with the external terminal;
a charging and discharging control switch connected between the external terminal and the secondary battery; and
the charging and discharging control circuit according to claim 1 , for monitoring one of the voltage and the current of the secondary battery to control the charging and discharging control switch.
5. The charging and discharging control circuit according to claim 1 , wherein the charger connection detection circuit comprising a third N-channel transistor comprising a source connected directly to the drain of the first N-channel transistor and to the overcurrent detection terminal.
6. A charging and discharging control circuit for monitoring one of a voltage and a current of a secondary battery to control a connection between an external terminal and the secondary battery, comprising:
an overcurrent detection circuit for monitoring a voltage at an overcurrent detection terminal to detect an overcurrent state;
a control circuit for controlling the connection between the external terminal and the secondary battery based on an output from the overcurrent detection circuit;
a pull-down circuit connected with the overcurrent detection terminal, for connecting the overcurrent detection terminal with a VSS terminal at a predetermined resistance value in the overcurrent state, the pull-down circuit comprising:
a first N-channel transistor comprising a drain and a source; and
a resistor connected between the overcurrent detection terminal and the drain of the first N-channel transistor;
a charger connection detection circuit connected with the overcurrent detection terminal, for detecting whether or not a charger is connected with the external terminal; and
a switching circuit controlled in response to an output from the charger connection detection circuit, the switching circuit comprising a second N-channel transistor comprising a source coupled to the source of the first N-channel transistor and a drain coupled to the VSS terminal.
7. The charging and discharging control circuit according to claim 6 , wherein the first N-channel transistor further comprises a gate connected with the control circuit.
8. The charging and discharging control circuit according to claim 6 , wherein a source voltage and a substrate voltage of the first N-channel transistor and a source voltage and a substrate voltage of the second N-channel transistor are equal to one another.
9. The charging and discharging control circuit according to claim 6 , wherein the charger connection detection circuit comprising a second N-channel transistor comprising a source connected directly to the resistor of the pull-down circuit and to the overcurrent detection terminal.