Secondary-battery monitoring device and battery pack

摘要

A secondary-battery monitoring device capable of realizing highly reliable overcurrent detection and a battery pack having it are provided. When an overcurrent flowing to a secondary battery is to be detected by utilizing a current detection voltage generated via on-resistance of a discharge-control switch and a charge-control switch, a voltage correction circuit that generates a correction voltage having a characteristic varied by positive slope or negative slope along with increase in a power supply voltage is provided, and the correction voltage is added to the detection voltage or a reference power supply voltage with the polarity that cancels out the slope of voltage variation caused in the detection voltage, and then the voltage is input to a comparator circuit. In this manner, variation in the overcurrent determination current is reduced.

主权项

1. A secondary-battery monitoring device comprising:
first and second battery connection terminals to which a secondary battery is to be connected; first and second external terminals to which a load or a charger is to be connected; a first current path arranged between the first battery connection terminal and the first external terminal; a second current path arranged between the second battery connection terminal and the second external terminal; a switch circuit including a pair of FETs that control a flow of a discharge current and a flow of a charge current, respectively, the switch circuit being inserted in the second current path so as to control the charge current and the discharge current flowing in the secondary battery; and a switch control unit, wherein the switch control unit is provided with: a second power-supply terminal connected to the second current path at a line connecting the second battery connection terminal and one node on the second current path of the switch circuit; a first power-supply terminal to which a first power supply voltage from the secondary battery is supplied via the first current path with using a voltage at the second power-supply terminal as a reference; a pair of control terminals; driver circuits configured to supply control voltages to gates of corresponding FETs via the control terminals; a detection terminal connected to the second current path at a line connecting the other node on the second current path of the switch circuit and the second external terminal; a first detection circuit configured to monitor the charge current flowing in the second current path based on a detection voltage detected at the detection terminal, and output a detection signal when the detection voltage reaches a predetermined value; a second detection circuit configured to monitor the discharge current and output a detection signal when the detection voltage reaches a predetermined value; and a control circuit configured to supply the control voltage via the corresponding driver circuit in response to the detection signal to carry out control of shutting off the corresponding FET, and wherein at least one of the first and second detection circuits is provided with: a comparator circuit configured to determine, based on a voltage of one input node of the comparator circuit serving as a reference voltage, magnitude of a voltage of the other input node of the comparator circuit to output the detection signal based on a result of the determination; and a voltage correction circuit configured to generate a correction voltage having a characteristic that varies by a slope approximating a slope of variation in the detection voltage that decreases along with an increase in the first power supply voltage, add the correction voltage to the detection voltage or a reference power supply voltage with such a polarity as canceling the slope of variation caused in the detection voltage by the slope of variation in the correction voltage, and input the voltage thus corrected to the comparator circuit.