Battery state monitoring circuit and battery device
View Patent ↗Provided is a battery state monitoring circuit including a control circuit that applies, to a gate of a signal output transistor provided at a terminal for transmitting an overcharge detection signal, a potential at which the signal output transistor is turned off at a voltage lower than a minimum circuit operating voltage. Accordingly, in a battery device that uses the cascade-connected battery state monitoring circuits, charge is inhibited securely even at a power supply voltage lower than the minimum circuit operating voltage.
1. A battery state monitoring circuit, which is to be connected to each of batteries connected in series, and has functions of monitoring a voltage of a corresponding one of the batteries and transmitting/receiving data indicative of monitoring results, the battery state monitoring circuit comprising:
a first voltage monitoring terminal and a second voltage monitoring terminal that are to be connected to the corresponding one of the batteries;
a first transmitting terminal;
a second transmitting terminal;
a first receiving terminal;
a second receiving terminal;
an overcharge detection circuit that detects whether or not the corresponding one of the batteries is in an overcharged state based on a voltage between the first voltage monitoring terminal and the second voltage monitoring terminal, and outputs an overcharge detection signal indicative of a result of the detecting;
an overdischarge detection circuit that detects whether or not the corresponding one of the batteries is in an overdischarged state based on the voltage between the first voltage monitoring terminal and the second voltage monitoring terminal, and outputs an overdischarge detection signal indicative of a result of the detecting;
an overcharge information communication circuit that transmits, when at least one of an overcharge detection signal indicative of whether or not another one of the batteries is in the overcharged state, which has been received via the first receiving terminal, and the overcharge detection signal that has been output from the overcharge detection circuit indicates that at least one of the another one of the batteries and the corresponding one of the batteries is in the overcharged state, an overcharge signal indicating that the at least one of the another one of the batteries and the corresponding one of the batteries is in the overcharged state from the first transmitting terminal to an outside; and
an overdischarge information communication circuit that transmits, when at least one of an overdischarge detection signal indicative of whether or not another one of the batteries is in the overdischarged state, which has been received via the second receiving terminal, and the overdischarge detection signal that has been output from the overdischarge detection circuit indicates that at least one of the another one of the batteries and the corresponding one of the batteries is in the overdischarged state, an overdischarge signal indicating that the at least one of the another one of the batteries and the corresponding one of the batteries is in the overdischarged state from the second transmitting terminal to the outside,
the overcharge information communication circuit comprising:
an output transistor that outputs the overcharge detection signal to the first transmitting terminal; and
a control circuit that controls the output transistor to output the overcharge signal when the voltage of the corresponding one of the batteries becomes lower than a voltage with which the overcharge information communication circuit is allowed to operate,
the battery state monitoring circuit being formed as one semiconductor device.
2. A battery state monitoring circuit according to claim 1 , wherein:
the output transistor comprises an open-drain output N-channel transistor; and
the control circuit comprises a pull-down circuit.
3. A battery state monitoring circuit according to claim 2 , wherein the pull-down circuit comprises an N-channel depletion transistor including a gate terminal and a source terminal that are saturation-connected with each other.
4. A battery state monitoring circuit according to claim 1 , wherein:
the output transistor comprises an open-drain output P-channel transistor; and
the control circuit comprises a pull-up circuit.
5. A battery state monitoring circuit according to claim 4 , wherein the pull-up circuit comprises an N-channel depletion transistor including a gate terminal and a source terminal that are saturation-connected with each other.
6. A battery device, comprising:
a first external terminal and a second external terminal that are to be connected to one of a load and a charger;
a plurality of batteries that are connected in series;
charge/discharge control switches that are provided between one of the first external terminal and the second external terminal, and the plurality of batteries that are connected in series; and
the battery state monitoring circuit according to claim 1 that is provided to each of the plurality of batteries.