Charging and discharging control circuit and charging type power supply device
View Patent ↗An overcharge detecting comparator ( 121 ) detects an overcharged state of a battery ( 101 ), and an overcurrent detecting comparator ( 120 ) detects an overcurrent state of the battery ( 101 ). In response to output signals from those comparators, a control circuit ( 210 ) performs on/off control of each of a switch ( 102 ) and a protection circuit ( 50 ). In response to an output signal from the control circuit ( 210 ), the protection circuit ( 50 ) is turned on, to thereby connect a resistor ( 125 ) to a path connecting a VSS terminal and an overcurrent detecting terminal, and is turned off, to thereby disconnect the resistor ( 125 ) from the path. As a result, even when the battery is in the overcurrent state, current consumption can be reduced.
1. A charging and discharging control circuit for controlling charging and discharging of a battery, comprising:
a voltage divider circuit for dividing a voltage of the battery;
a first reference voltage circuit for outputting a first reference voltage;
a second reference voltage circuit for outputting a second reference voltage;
an overcharge detecting comparator for comparing an output signal of the voltage divider circuit with the first reference voltage to detect an overcharged state of the battery;
an overcurrent detecting comparator for comparing a voltage at an overcurrent detecting terminal with the second reference voltage to detect an overcurrent state of the battery;
a control circuit for performing on/off control of each of the switch provided between one of a charger and a load and the battery, and of a protection circuit provided between a VSS terminal and the overcurrent detecting terminal, in response to an output signal from each of the overcharge detecting comparator and the overcurrent detecting comparator; and
the protection circuit which is turned on in response to an output signal from the control circuit so as to connect a resistor to a path connecting the VSS terminal and the overcurrent detecting terminal, and which is turned off in response to the output signal from the control circuit so as to disconnect the resistor from the path.
2. A charging and discharging control circuit according to claim 1 , wherein the protection circuit comprises an N-type transistor.
3. A charging and discharging control circuit according to claim 2 , wherein the N-type transistor has a back gate which is connected to a source of the N-type transistor through a first parasitic diode, and which is also connected to a drain of the N-type transistor through a second parasitic diode.
4. A charging and discharging control circuit according to claim 2 , wherein the N-type transistor has a back gate which is connected to a source of the N-type transistor through a parasitic diode, and which is also connected to a gate of the N-type transistor through a resistor.
5. A charging type power supply device, comprising:
a switch;
a battery; and
a charging and discharging control circuit mounted to the charging type power supply device, for controlling charging and discharging of the battery, including:
a voltage divider circuit for dividing a voltage of the battery;
a first reference voltage circuit for outputting a first reference voltage;
a second reference voltage circuit for outputting a second reference voltage;
an overcharge detecting comparator for comparing an output signal of the voltage divider circuit with the first reference voltage to detect an overcharged state of the battery;
an overcurrent detecting comparator for comparing a voltage at an overcurrent detecting terminal with the second reference voltage to detect an overcurrent state of the battery;
a control circuit for performing on/off control of each of the switch provided between one of a charger and a load and the battery, and of a protection circuit provided between a VSS terminal and the overcurrent detecting terminal, in response to an output signal from each of the overcharge detecting comparator and the overcurrent detecting comparator; and
the protection circuit which is turned on in response to an output signal from the control circuit so as to connect a resistor to a path connecting the VSS terminal and the overcurrent detecting terminal, and which is turned off in response to the output signal from the control circuit so as to disconnect the resistor from the path.