CONTROL SYSTEM, CONTROL METHOD, AND SECONDARY BATTERY PROTECTION INTEGRATED CIRCUIT

Abstract

A control system, a control method, and a secondary battery protection integrated circuit are provided that are capable of controlling the balance of the cell voltages of a plurality of secondary battery cells connected in series with high precision. [Solution] A control system 310 includes a battery pack 15 having a secondary battery protection device 110 and an external device 140. The secondary battery protection device has one or more monitor terminals that are provided so that the potential of one or more negative electrodes of multiple secondary battery cells connected in series can be monitored via a path different from the power supply path, one or more internal wirings 85, 86 interposed between the one or more negative electrodes and the one or more monitor terminals, and one or more internal switches 21-24 inserted in series with each of the one or more internal wirings. The external device has a balance control circuit that controls the balance of the cell voltages of the multiple secondary battery cells by controlling the current flowing through a wiring path that includes at least one of the internal wirings based on the potential of the one or more monitor terminals.

Description

[Technical field]

[0001] The present invention relates to a control system, a control method, and a secondary battery protection integrated circuit. [Background technology]

[0002] Conventionally, there is known a charging device that charges a battery pack having a plurality of secondary battery cells connected in series and a midpoint terminal connected between the plurality of secondary battery cells. The charging device includes a charging control microcomputer that adjusts the voltage balance between the cells by charging and discharging from the midpoint terminal. The charging control microcomputer calculates the voltage of two cells from the voltage between the + terminal and - terminal of the battery pack and the voltage between the midpoint terminal and - terminal, and adjusts the voltage balance between the cells when the difference between the voltages of both cells is equal to or greater than a predetermined value. Meanwhile, the battery pack includes a pair of protection FETs between the - terminal and the secondary battery cells to protect the plurality of secondary battery cells. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2010-57249 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, because a voltage drop occurs due to the on-resistance of a pair of protection FETs between the negative terminal and the secondary battery cell, the inter-terminal voltage between the midpoint terminal and the negative terminal becomes higher than the actual cell voltage, which may result in a decrease in the accuracy of adjusting the voltage balance between the cells.

[0005] The present disclosure provides a control system, a control method, and a secondary battery protection integrated circuit that are capable of controlling the balance of the cell voltages of a plurality of secondary battery cells connected in series with high precision. [Means for solving the problem]

[0006] The present disclosure relates to A plurality of secondary battery cells connected in series; a power supply path connected in series to the plurality of secondary battery cells; At least one switch element inserted in series in the power supply path; a secondary battery protection device that protects the plurality of secondary battery cells by controlling the switch elements; an external device that controls a balance of the cell voltages of the plurality of secondary battery cells; The secondary battery protection device includes: an abnormality detection circuit that detects overcharging or overdischarging by monitoring the voltage of all or each of the plurality of secondary battery cells; A potential of one or more electrodes including an electrode to which the switch element is connected among the electrodes of the plurality of secondary battery cells can be monitored via a path that does not include the switch element. a first monitor terminal connected to the external device and a second monitor terminal connected to the secondary battery cell; and, At least the first monitor terminal and the second monitor terminal one or more internal wirings interposed between the monitor terminal; one or more internal switches that are inserted in series with the one or more internal wirings, respectively, and that cut off a current flowing through the internal wirings when an overcharge or overdischarge is detected by the abnormality detection circuit; a switch control circuit that turns on or off each of the internal switches in response to a result of the abnormality detection by the abnormality detection circuit; The switch control circuit provides a control system that turns off the internal switch when at least one of the plurality of secondary battery cells is in an over-discharged state.

[0007] The present disclosure relates to A control method performed by a secondary battery protection circuit that protects a plurality of secondary battery cells connected in series by controlling at least one switch element inserted in series in a power supply path connected in series to the plurality of secondary battery cells, the method comprising: The secondary battery protection circuit includes: an abnormality detection circuit that detects overcharging or overdischarging by monitoring the voltage of all or each of the plurality of secondary battery cells; A potential of one or more electrodes including an electrode to which the switch element is connected among the electrodes of the plurality of secondary battery cells can be monitored via a path that does not include the switch element. a first monitor terminal connected to an external device and a second monitor terminal connected to the secondary battery cell; and, At least the first monitor terminal and the second monitor terminal one or more internal wirings interposed between the monitor terminal; one or more internal switches that are inserted in series with the one or more internal wirings, respectively, and that cut off a current flowing through the internal wirings when an overcharge or overdischarge is detected by the abnormality detection circuit; a switch control circuit that turns on or off each of the internal switches in response to a result of the abnormality detection by the abnormality detection circuit; The switch control circuit turns off the internal switch when at least one of the plurality of secondary battery cells is in an over-discharged state.

[0008] The present disclosure relates to A secondary battery protection integrated circuit that protects a plurality of secondary battery cells connected in series by controlling at least one switch element inserted in series in a power supply path connected in series to the plurality of secondary battery cells, an abnormality detection circuit that detects overcharging or overdischarging by monitoring the voltage of all or each of the plurality of secondary battery cells; A potential of one or more electrodes including an electrode to which the switch element is connected among the electrodes of the plurality of secondary battery cells can be monitored via a path that does not include the switch element. a first monitor terminal connected to an external device and a second monitor terminal connected to the secondary battery cell; and, At least the first monitor terminal and the second monitor terminal one or more internal wirings interposed between the monitor terminal; one or more internal switches that are inserted in series with the one or more internal wirings, respectively, and that cut off a current flowing through the internal wirings when an overcharge or overdischarge is detected by the abnormality detection circuit; a switch control circuit that turns on or off each of the internal switches in response to a result of the abnormality detection by the abnormality detection circuit; The switch control circuit provides a secondary battery protection integrated circuit that turns off the internal switch when at least one of the plurality of secondary battery cells is in an over-discharged state. Effect of the Invention

[0009] According to the present disclosure, the balance of the cell voltages of a plurality of secondary battery cells connected in series can be controlled with high precision. [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is a diagram showing a configuration example of a control system in the first embodiment, and is a diagram showing a first discharge path in a normal state in which no abnormality is detected in a plurality of secondary battery cells. [Diagram 2] FIG. 2 is a diagram showing a configuration example of the control system in the first embodiment, and is a diagram showing a second discharge path in a normal state in which no abnormality is detected in a plurality of secondary battery cells. [Diagram 3] FIG. 2 is a diagram showing a configuration example of a control system in the first embodiment, illustrating a discharge path in a state in which over-discharge of at least one secondary battery cell among a plurality of secondary battery cells is detected. [Figure 4] FIG. 2 is a diagram showing an example of a configuration of a control system in a first embodiment, illustrating a charging path when a charger is connected in a state in which over-discharge of at least one secondary battery cell among a plurality of secondary battery cells is detected. [Diagram 5] FIG. 2 is a diagram showing a configuration example of the control system in the first embodiment, illustrating a discharge path in a state in which overcharging of a secondary battery cell on a lower potential side among a plurality of secondary battery cells is detected. [Figure 6] FIG. 2 is a diagram showing a configuration example of the control system in the first embodiment, illustrating a discharge path in a state in which overcharging of a secondary battery cell on a higher potential side among a plurality of secondary battery cells is detected. [Figure 7]FIG. 13 is a diagram showing a configuration example of a control system in a second embodiment, illustrating a charging path in cell balance control by charging and discharging a secondary battery cell on a lower potential side among a plurality of secondary battery cells. [Figure 8] FIG. 13 is a diagram showing a configuration example of a control system in a second embodiment, illustrating a discharge path in cell balance control by charging and discharging a secondary battery cell on a lower potential side among a plurality of secondary battery cells. [Figure 9] FIG. 13 is a diagram showing a configuration example of a control system in a third embodiment, illustrating a discharge path in cell balance control by discharging a secondary battery cell on a lower potential side among a plurality of secondary battery cells. [Figure 10] FIG. 13 is a diagram showing a configuration example of a control system in a third embodiment, illustrating a discharge path in cell balance control by discharging a secondary battery cell on a higher potential side among a plurality of secondary battery cells. [Figure 11] FIG. 13 is a diagram showing a configuration example of a control system in a third embodiment, illustrating a charging path in cell balance control by charging a secondary battery cell on a lower potential side among a plurality of secondary battery cells. [Figure 12] FIG. 13 is a diagram showing a configuration example of a control system in a fourth embodiment, illustrating a discharge path in cell balance control by discharging a secondary battery cell on a lower potential side among a plurality of secondary battery cells. [Figure 13] FIG. 13 is a diagram showing an example of the configuration of a control system in a fourth embodiment, illustrating charge / discharge paths in cell balance control by discharging a secondary battery cell on the higher potential side or charging a secondary battery cell on the lower potential side among multiple secondary battery cells. [Figure 14] FIG. 13 is a diagram showing a configuration example of a control system in a fifth embodiment, illustrating a discharge path in cell balance control by discharging a secondary battery cell on a higher potential side among a plurality of secondary battery cells. [Figure 15] FIG. 13 is a diagram showing a configuration example of a control system in a sixth embodiment, illustrating a discharge path in cell balance control by discharging a secondary battery cell on a higher potential side among a plurality of secondary battery cells. [Figure 16]1A and 1B are diagrams illustrating an example of switch control and terminal processing in each state. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings.

[0012] First Embodiment Fig. 1 is a diagram showing an example of the configuration of a control system in the first embodiment. A control system 301 shown in Fig. 1 is a system that controls the balance of the cell voltages of multiple (two in this example) secondary battery cells 201, 202 connected in series. The control system 301 includes an external device 140 and a battery pack 151.

[0013] The external device 140 is a device connected to the battery pack 151. The external device 140 may be a charger that charges the battery pack 151, or may be a device that operates on power supplied from the battery pack 151. Specific examples of devices that operate on power supplied from the battery pack 151 include electronic devices such as smartphones, tablets, and mobile phones.

[0014] The external device 140 has a balance control circuit 33 that controls the balance of the cell voltages of the multiple secondary battery cells. The balance control circuit 33 will be described later.

[0015] The battery pack 151 is a component that houses a plurality of secondary battery cells 201, 202 connected in series, and is used by being connected to an external device 140. The battery pack 151 includes a plurality of secondary battery cells 201, 202 and a secondary battery protection device 110.

[0016] The multiple secondary battery cells 201 are rechargeable battery cells. Specific examples of secondary batteries include lithium ion batteries and lithium polymer batteries.

[0017] The secondary battery cell 201 is an example of a first secondary battery cell, and has a positive electrode 201b and a negative electrode 201a. The positive electrode 201b is an example of a first positive electrode. The negative electrode 201a is an example of a first negative electrode having the lowest potential among a plurality of negative electrodes which are electrodes on the low potential side of each of the plurality of secondary battery cells. The secondary battery cell 202 is an example of a second secondary battery cell, and has a positive electrode 202b and a negative electrode 202a. The positive electrode 202b is an example of a second positive electrode. The negative electrode 202a is connected to the positive electrode 201b.

[0018] The secondary battery protection device 110 operates using multiple secondary battery cells 201, 202 as a power source, and protects the multiple secondary battery cells 201, 202 from over-discharge, etc. by controlling the charging and discharging of the multiple secondary battery cells 201, 202. The secondary battery protection device 110 includes, for example, a switch circuit 13, a protection IC 120, resistive elements R1, R2, R3, R4, R5, capacitive elements C1, C2, and a substrate (not shown) on which these are mounted.

[0019] A specific example of the substrate is a printed circuit board. The substrate is provided with terminals B-, B+, BM, P-, P+, BSL, and BSM. Each of these terminals is, for example, an electrode formed on the substrate. Furthermore, the substrate is provided with power supply paths 7 and 8.

[0020] The terminal B- is an example of a negative battery terminal and is connected to the negative electrode 201a of the secondary battery cell 201 having the lowest potential among the secondary battery cells connected in series. The terminal B+ is an example of a positive battery terminal and is connected to the positive electrode 202b of the secondary battery cell 202 having the highest potential among the secondary battery cells connected in series. The terminal BM is an example of a battery monitor terminal and is connected between adjacent secondary battery cells among the secondary battery cells connected in series. In this example, the terminal BM is connected to the positive electrode 201b of the secondary battery cell 201 and the negative electrode 202a of the secondary battery cell 202.

[0021] The terminal P− is an example of a negative load terminal, and is connected to the ground terminal of the external device 140. The terminal P+ is an example of a positive load terminal, and is connected to the power supply terminal of the external device 140.

[0022] Terminal B- and terminal P- are connected by a negative power supply path 7. The power supply path 7 is a current path between terminal B- and terminal P-, through which a charging current or a discharging current flows. The power supply path 7 is connected in series to the negative electrode 201a of the secondary battery cell 201.

[0023] The terminals B+ and P+ are connected by a positive power supply path 8. The power supply path 8 is a current path between the terminals B+ and P+, through which a charging current or a discharging current flows. The power supply path 8 is connected in series to the positive electrode 202b of the secondary battery cell 202.

[0024] The terminal BSL is an example of a first monitor terminal, and is provided so that the potential of the negative electrode 201a of the secondary battery cell 201 can be monitored via a path different from the power supply paths 7 and 8. The terminal BSL is connected to a low potential side monitor unit of the balance control circuit 33. The terminal BSM is an example of a second monitor terminal, and is provided so that the potential of the negative electrode 202a of the secondary battery cell 202 can be monitored via a path different from the power supply paths 7 and 8. The terminal BSM is connected to a high potential side monitor unit of the balance control circuit 33.

[0025] The switch circuit 13 is inserted in series in the power supply path 7 between the terminal B- and the terminal P-. The switch circuit 13 is, for example, a series circuit in which a charge control transistor 11 and a discharge control transistor 12 are connected in series. When the charge control transistor 11 is turned off, the power supply path 7 through which the charging current of the secondary battery cells 201, 202 flows is interrupted, and the flow of the charging current of the secondary battery cells 201, 202 is prohibited. When the discharge control transistor 12 is turned off, the power supply path 7 through which the discharging current of the secondary battery cells 201, 202 flows is interrupted, and the flow of the discharging current of the secondary battery cells 201, 202 is prohibited.

[0026] The charge control transistor 11 and the discharge control transistor 12 are, for example, N-channel type MOSFETs (Metal Oxide Semiconductor Field Effect Transistors). The charge control transistor 11 is a switch element inserted in series into the power supply path 7 so that the forward direction of the parasitic diode of the charge control transistor 11 coincides with the direction of the discharge current of the secondary battery cells 201, 202. The discharge control transistor 12 is a switch element inserted in series into the power supply path 7 so that the forward direction of the parasitic diode of the discharge control transistor 12 coincides with the direction of the charge current of the secondary battery cells 201, 202.

[0027] The protection IC 120 is an example of a secondary battery protection integrated circuit. The protection IC 120 operates using the secondary battery cells 201, 202 as a power source. The protection IC 120 protects the secondary battery cells 201, 202 from over-discharge and the like by controlling the switch circuit 13. For example, the protection IC 120 protects the secondary battery cells 201, 202 from charging abnormalities (e.g., over-charge, overcurrent in the charging direction (charging overcurrent), etc.) by turning off the charge control transistor 11. On the other hand, the protection IC 120 protects the secondary battery cells 201, 202 from discharging abnormalities (e.g., over-discharge, overcurrent in the discharging direction (discharging overcurrent), etc.) by turning off the discharge control transistor 12.

[0028] The protection IC 120 includes a terminal VDD, a terminal VSS, a terminal VBM, a terminal DO, a terminal CO, a terminal VM, a terminal BS1, and a terminal BS2. These terminals are external connection terminals for connecting the internal circuit of the protection IC 120 to the outside of the protection IC 120.

[0029] The terminal VDD is an example of a positive power supply terminal connected to the power supply path 8, and is connected to the positive electrode 202b of the secondary battery cell 202 via the terminal B+. In this example, the terminal VDD is connected to the positive electrode 202b of the secondary battery cell 202 via a resistive element R1 and the terminal B+. A CR filter is configured by the resistive element R1 and the capacitive element C1.

[0030] The terminal VSS is an example of a negative side power supply terminal connected to the power supply path 7 between the negative electrode 201a of the secondary battery cell 201 and the switch circuit 13, and is a ground terminal connected to the negative electrode 201a of the secondary battery cell 201 via the terminal B-.

[0031] The terminal VBM is an example of an intermediate monitor terminal that is provided so as to be able to monitor the potential (intermediate potential) between adjacent secondary battery cells among the secondary battery cells connected in series. In this example, the terminal VBM is connected between the positive electrode 201b of the secondary battery cell 201 and the negative electrode 202a of the secondary battery cell 202 via a resistive element R2 and a terminal BM. A CR filter is configured by the resistive element R2 and the capacitive element C2.

[0032] The terminal CO is an example of a charge control terminal that outputs a signal for prohibiting charging of the secondary battery cells 201, 202, and is connected to the control electrode of the charge control transistor 11 (for example, the gate in the case of a MOSFET).

[0033] The terminal DO is an example of a discharge control terminal that outputs a signal for prohibiting the discharge of the secondary battery cells 201, 202, and is connected to the control electrode of the discharge control transistor 12 (for example, the gate in the case of a MOSFET).

[0034] The terminal VM is an example of a monitoring terminal that monitors the potential of the terminal P-, and is connected to the power supply path 7 between the terminal P- and the switch circuit 13. The terminal VM is connected to the terminal P- via a resistive element R3.

[0035] The terminal BS1, like the terminal BSL, is an example of a first monitor terminal and is provided so that the potential of the negative electrode 201a of the secondary battery cell 201 can be monitored through a path different from the power supply paths 7 and 8. In this example, the terminal BS1 is connected to the terminal BSL through a resistive element R5. The current value of the current flowing through the wiring path including the terminal BS1 and the terminal BSL can be adjusted by the resistance value of the resistive element R5.

[0036] The terminal BS2, like the terminal BSM, is an example of a second monitor terminal and is provided so that the potential of the negative electrode 202a of the secondary battery cell 202 can be monitored through a path different from the power supply paths 7 and 8. The terminal BS2 is connected to the terminal BSM through a resistive element R4. The current value of the current flowing through the wiring path including the terminal BS2 and the terminal BSM can be adjusted by the resistance value of the resistive element R4.

[0037] The protection IC 120 includes a discharge control circuit 81, a charge control circuit 82, a switch control circuit 83, internal wirings 85 and 86, internal switches 21, 22, 23, 24, and 43, and internal resistors 51 and 52.

[0038] The discharge control circuit 81 has an abnormality detection circuit that detects a discharge abnormality in the secondary battery cells 201, 202. The discharge control circuit 81 is an example of a control circuit that controls the switch circuit 13 based on the detection result of the abnormality detection circuit when a discharge abnormality in the secondary battery cells 201, 202 is detected by the abnormality detection circuit. The charge control circuit 82 has an abnormality detection circuit that detects a charging abnormality in the secondary battery cells 201, 202. The charge control circuit 82 is an example of a control circuit that controls the switch circuit 13 based on the detection result of the abnormality detection circuit when a charging abnormality in the secondary battery cells 201, 202 is detected by the abnormality detection circuit.

[0039] The charge control circuit 82 includes an overcharge detection circuit (an example of an abnormality detection circuit) that detects overcharging (an example of a predetermined abnormality) of the secondary battery cells 201, 202. The overcharge detection circuit monitors the power supply voltage VD between the terminals VDD and VSS. The overcharge detection circuit may monitor the cell voltages of each of the secondary battery cells 201, 202. For example, the overcharge detection circuit monitors the voltage between the terminals VBM and VSS as the cell voltage VC1 of the secondary battery cell 201, and monitors the voltage between the terminals VDD and VBM as the cell voltage VC2 of the secondary battery cell 202. When the overcharge detection circuit detects that at least one of the cell voltages VC1 and VC2 is equal to or higher than a predetermined overcharge detection threshold Vdet1, the charge control circuit 82 outputs a charge control signal from the terminal CO that turns off the charge control transistor 11 (overcharge protection operation). By turning off the charge control transistor 11, the current in the charging direction of the secondary battery cells 201, 202 is cut off, so that the secondary battery cells 201, 202 can be prevented from being overcharged.

[0040] The discharge control circuit 81 includes an overdischarge detection circuit (an example of an abnormality detection circuit) that detects overdischarge (an example of a predetermined abnormality) of the secondary battery cells 201, 202. The overdischarge detection circuit monitors the power supply voltage VD between the terminals VDD and VSS. The overdischarge detection circuit may monitor the cell voltages of each of the secondary battery cells 201, 202. For example, the overdischarge detection circuit monitors the voltage between the terminals VBM and VSS as the cell voltage VC1 of the secondary battery cell 201, and monitors the voltage between the terminals VDD and VBM as the cell voltage VC2 of the secondary battery cell 202. When the overdischarge detection circuit detects that at least one of the cell voltages VC1 and VC2 is equal to or lower than a predetermined overdischarge detection threshold Vdet2, the discharge control circuit 81 outputs a discharge control signal from the terminal DO that turns off the discharge control transistor 12 (overdischarge protection operation). By turning off the discharge control transistor 12, the current in the discharging direction of the secondary battery cells 201, 202 is cut off, so that the secondary battery cells 201, 202 can be prevented from being over-discharged.

[0041] The discharge control circuit 81 includes a discharge overcurrent detection circuit (an example of an abnormality detection circuit) that detects a discharge overcurrent (an example of a predetermined abnormality) of the secondary battery cells 201, 202. The discharge overcurrent detection circuit monitors a current detection voltage VI between the terminal VM and the terminal VSS. When the discharge overcurrent detection circuit detects that the current detection voltage VI is equal to or greater than a predetermined discharge overcurrent detection threshold Vdet3, the discharge control circuit 81 outputs a discharge control signal that turns off the discharge control transistor 12 from the terminal DO (discharge overcurrent protection operation). By turning off the discharge control transistor 12, the current in the discharge direction of the secondary battery cells 201, 202 is interrupted, so that it is possible to prevent an overcurrent from flowing in the direction of discharging the secondary battery cells 201, 202.

[0042] The charging control circuit 82 includes a charging overcurrent detection circuit (an example of an abnormality detection circuit) that detects a charging overcurrent (an example of a predetermined abnormality) of the secondary battery cells 201, 202. The charging overcurrent detection circuit monitors a current detection voltage VI between the terminal VM and the terminal VSS. When the charging overcurrent detection circuit detects that the current detection voltage VI is equal to or lower than a predetermined charging overcurrent detection threshold Vdet4, the charging control circuit 82 outputs a charging control signal from the terminal CO that turns off the charging control transistor 11 (charging overcurrent protection operation). By turning off the charging control transistor 11, the current in the charging direction of the secondary battery cells 201, 202 is cut off, so that it is possible to prevent an overcurrent from flowing in the direction of charging the secondary battery cells 201, 202.

[0043] The internal wiring 85 is a current path between the negative electrode 201a and the terminal BSL, more specifically, between the terminal VSS and the terminal BS1. The internal wiring 86 is a current path between the negative electrode 202a and the terminal BSM, more specifically, between the terminal VBM and the terminal BS2.

[0044] The switch control circuit 83 is a circuit that turns on or off each of the multiple internal switches 21, 22, 23, 24, and 43 in response to the result of abnormality detection by the abnormality detection circuit described above.

[0045] The internal switch 21 is inserted in series in the internal wiring 85. The internal switch 22 is provided so as to be able to short-circuit the terminal BS1 and the terminal VM. The internal switch 23 is inserted in series in the internal wiring 86. The internal switch 24 is provided so as to be able to short-circuit the terminal BS2 and the terminal VM. The internal switch 43 is provided so as to be able to select a state in which the terminal VM is pulled down to the terminal VSS via the internal resistor 51, a state in which the terminal VM is pulled up to the terminal VDD via the internal resistor 52, or a state in which the terminal is neither pulled up nor pulled down. Each of the multiple internal switches 21, 22, 23, 24, 43 is turned on or off by the switch control circuit 83 according to the abnormality detection result by the abnormality detection circuit described above.

[0046] The external device 140 includes a balance control circuit 33. The balance control circuit 33 controls the balance of the cell voltages of the multiple secondary battery cells 201, 202 by controlling the current flowing through a wiring path including at least one of the multiple internal wirings 85, 86 based on the potentials of the multiple terminals BSL, BSM. In this example, the external device 140 includes a current control circuit 30 that controls the current flowing through a wiring path including at least one of the multiple internal wirings 85, 86. The balance control circuit 33 controls the balance of the cell voltages of the multiple secondary battery cells 201, 202 by controlling the current control circuit 30.

[0047] The current control circuit 30 includes, for example, a plurality of current sources 31, 32 connected in parallel to corresponding secondary battery cells among the plurality of secondary battery cells 201, 202. The balance control circuit 33 controls the current control circuit 30 so that a constant current flows from one of the plurality of current sources 31, 32 to a wiring path including at least one of the plurality of internal wirings 85, 86, thereby controlling the balance of the cell voltages of the plurality of secondary battery cells 201, 202.

[0048] The current source 32 is, for example, a constant current source connected in parallel to the secondary battery cell 201. The balance control circuit 33 controls the discharge amount of the secondary battery cell 201 by passing a constant current generated by the current source 32 through a wiring path DR1 (see FIG. 1) including the internal wiring 86 and the power supply path 7. As a result, even if the resistance value of the resistive element R4 in the battery pack 151 changes due to aging deterioration, design change, etc., the external device 140 can pass a desired amount of discharge current through the wiring path DR1 including the secondary battery cell 201, the internal wiring 86, and the power supply path 7.

[0049] The current source 31 is, for example, a constant current source connected in parallel to the secondary battery cell 202. The balance control circuit 33 controls the discharge amount of the secondary battery cell 202 by flowing the constant current generated by the current source 31 through a wiring path DR2 (see FIG. 2) including the internal wiring 86 and the power supply path 8. As a result, even if the resistance value of the resistive element R4 in the battery pack 151 changes due to aging deterioration, design change, etc., the external device 140 can flow a desired amount of discharge current through the wiring path DR2 including the secondary battery cell 202, the internal wiring 86, and the power supply path 7.

[0050] The current control circuit 30 has, for example, a switching circuit including a plurality of switches 25, 26 connected in parallel to corresponding secondary battery cells among the plurality of secondary battery cells 201, 202. The balance control circuit 33 controls the balance of the cell voltages of the plurality of secondary battery cells 201, 202 by controlling this switching circuit. The switching circuit switches between conduction and non-conduction of a wiring path including at least one internal wiring among the plurality of internal wirings 85, 86.

[0051] The switch 26 is connected in parallel to the secondary battery cell 201 and in series to the current source 32. The switch 26 switches the wiring path DR1 (see FIG. 1 ) including the internal wiring 86 and the power supply path 7 between conductive and non-conductive states in response to a switching signal from the balance control circuit 33. This allows the external device 140 to control the desired amount of discharge to the wiring path DR1 including the secondary battery cell 201, the internal wiring 86, and the power supply path 7.

[0052] The switch 25 is connected in parallel to the secondary battery cell 202 and in series to the current source 31. The switch 25 switches the wiring path DR2 (see FIG. 2 ) including the internal wiring 86 and the power supply path 8 between conductive and non-conductive states in response to a switching signal from the balance control circuit 33. This allows the external device 140 to control the desired amount of discharge to the wiring path DR2 including the secondary battery cell 202, the internal wiring 86, and the power supply path 8.

[0053] Fig. 16 is a diagram showing an example of switch control and terminal processing in each state. An example of the operation of the control system will be described below with reference to Fig. 16 as needed.

[0054] The charge control circuit 82 turns on the charge control transistor 11 when neither overcharging nor a charging overcurrent is detected in the secondary battery cells 201, 202. On the other hand, the charge control circuit 82 turns off the charge control transistor 11 when at least one of overcharging and a charging overcurrent is detected in the secondary battery cells 201, 202.

[0055] The discharge control circuit 81 turns on the discharge control transistor 12 when neither over-discharge nor discharge overcurrent is detected in the secondary battery cells 201, 202. On the other hand, the discharge control circuit 81 turns off the discharge control transistor 12 when at least one of over-discharge and discharge overcurrent is detected in the secondary battery cells 201, 202.

[0056] 1 and 2 show a normal state where no abnormality is detected in the secondary battery cells 201, 202. When overcharging, overdischarging, discharging overcurrent, and charging overcurrent are not detected in the secondary battery cells 201, 202 (normal state), the switch control circuit 83 turns on the internal switch 21, turns off the internal switch 22, turns on the internal switch 23, turns off the internal switch 24, and turns off the internal switch 43. As a result, the terminal BSL has approximately the same potential as the terminal B-, the terminal VSS, and the negative electrode 201a, and the terminal BSM has approximately the same potential as the terminal BM, the terminal VBM, and the negative electrode 202a.

[0057] 1 and 2, the balance control circuit 33 can measure the cell voltage of the secondary battery cell 201 with high accuracy by monitoring the potential difference between the terminals BSM and P-. Also, in the normal state shown in Figures 1 and 2, the balance control circuit 33 can measure the cell voltage of the secondary battery cell 202 with high accuracy by monitoring the potential difference between the terminals BSM and P+. Also, in the normal state shown in Figures 1 and 2, the balance control circuit 33 can measure the cell voltage (total cell voltage VC) obtained by adding up the cell voltages of the secondary battery cells 201 and 202 with high accuracy by monitoring the potential difference between the terminals BSL and P+.

[0058] 1 shows a case where, in a normal state, the cell voltage of the secondary battery cell 201 is higher than the cell voltage of the secondary battery cell 202. When the balance control circuit 33 determines that the cell voltage of the secondary battery cell 201 is higher than the cell voltage of the secondary battery cell 202, the balance control circuit 33 switches the switch 26 from off to on to lower the cell voltage of the secondary battery cell 201, thereby discharging the secondary battery cell 201 through the wiring path DR1.

[0059] 2 shows a case where, in a normal state, the cell voltage of the secondary battery cell 202 is higher than the cell voltage of the secondary battery cell 201. When the balance control circuit 33 determines that the cell voltage of the secondary battery cell 202 is higher than the cell voltage of the secondary battery cell 201, the balance control circuit 33 switches the switch 25 from off to on to lower the cell voltage of the secondary battery cell 202, thereby discharging the secondary battery cell 202 through the wiring path DR2.

[0060] When the difference between the cell voltage of the secondary battery cell 201 and the cell voltage of the secondary battery cell 202 becomes equal to or less than a predetermined threshold, the balance control circuit 33 stops discharging the secondary battery cells 201 and 202 through cell balance control by turning off both switches 25 and 26.

[0061] FIG. 3 is a diagram showing a configuration example of the control system in the first embodiment, and is a diagram showing a discharge path in a state where over-discharge of at least one of the multiple secondary battery cells is detected. In a state where over-discharge of at least one of the multiple secondary battery cells 201, 202 is detected, the switch control circuit 83 turns off the internal switch 21, turns on the internal switch 22, turns off the internal switch 23, turns on the internal switch 24, and sets the internal switch 43 to the pull-up side. As a result, the terminal BSL (terminal BS1) and the terminal BSM (terminal BS2) are shorted to the terminal P- (terminal VM), and the terminal P- is pulled up to the terminal VDD. Therefore, in a state where over-discharge is detected, the leakage current path DR3 that flows from the power supply path 8 to the terminals BS1 and BS2 via the power supply terminal VDD of the external device 140, the resistance component 143 of the external device 140, and the parasitic diodes 141 and 142 can be cut off. As a result, the progress of discharge of the secondary battery cells 201 and 202 can be suppressed.

[0062] FIG. 4 is a diagram showing a configuration example of the control system in the first embodiment, and is a diagram showing a charging path when a charger is connected in a state where over-discharge of at least one secondary battery cell among the multiple secondary battery cells is detected. When the charger 130 is connected in a state where over-discharge of at least one secondary battery cell among the multiple secondary battery cells 201, 202 is detected, the switch control circuit 83 turns on the internal switch 21, turns off the internal switch 22, turns on the internal switch 23, turns off the internal switch 24, and sets the internal switch 43 to the pull-up side. As a result, the terminal BSL (terminal BS1) is shorted to the terminal P- (terminal VSS), the terminal BSM (terminal BS2) is shorted to the terminal BM (terminal VBM), and the terminal P- is pulled up to the terminal VDD. Therefore, when the charger 130 is connected in a state where over-discharge is detected, the secondary battery cells 201, 202 can be charged through the wiring path CR1 from the charger 130 to the secondary battery cells 201, 202. Furthermore, the external device 140 can measure the cell voltages of the secondary battery cells 201, 202 with high accuracy without being affected by the forward voltages of the parasitic diodes 141, 142 (see FIG. 3), so that unnecessary repetition of pre-charging and quick charging can be prevented.

[0063] FIG. 5 is a diagram showing a configuration example of the control system in the first embodiment, and shows a discharge path in a state where overcharging of a secondary battery cell on the low potential side among the multiple secondary battery cells is detected. In a state where overcharging of only one of the multiple secondary battery cells 201, 202 is detected, the switch control circuit 83 turns off the internal switch 21, turns on the internal switch 22, turns on the internal switch 23, turns off the internal switch 24, and turns off the internal switch 43. As a result, the terminal BSL (terminal BS1) is shorted to the terminal P- (terminal VM), the terminal BSM (terminal BS2) is shorted to the terminal BM (terminal VBM), and the terminal P- becomes high impedance (Hi-Z). When the balance control circuit 33 determines that the cell voltage of the secondary battery cell 201 is higher than the cell voltage of the secondary battery cell 202, the balance control circuit 33 switches the switch 26 from off to on to lower the cell voltage of the secondary battery cell 201, thereby discharging the secondary battery cell 201 through the wiring path DR1. Therefore, even if overcharging is detected, the secondary battery cells 201 can be discharged by cell balance control.

[0064] FIG. 6 is a diagram showing a configuration example of the control system in the first embodiment, and is a diagram showing a discharge path in a state where overcharging of a secondary battery cell on the high potential side among the multiple secondary battery cells is detected. In a state where overcharging of only one of the multiple secondary battery cells 201, 202 is detected, the switch control circuit 83 turns off the internal switch 21, turns on the internal switch 22, turns on the internal switch 23, turns off the internal switch 24, and turns off the internal switch 43. As a result, the terminal BSL (terminal BS1) is shorted to the terminal P- (terminal VM), the terminal BSM (terminal BS2) is shorted to the terminal BM (terminal VBM), and the terminal P- becomes high impedance (Hi-Z). When the balance control circuit 33 determines that the cell voltage of the secondary battery cell 202 is higher than the cell voltage of the secondary battery cell 201, the balance control circuit 33 switches the switch 25 from off to on to lower the cell voltage of the secondary battery cell 202, thereby discharging the secondary battery cell 202 through the wiring path DR2. Therefore, even if overcharging is detected, the secondary battery cells 202 can be discharged by cell balance control.

[0065] <Second embodiment> Fig. 7 is a diagram showing an example of the configuration of a control system in the second embodiment, and is a diagram showing a charging path in cell balance control by charging and discharging a secondary battery cell on the low potential side among a plurality of secondary battery cells. Fig. 8 is a diagram showing an example of the configuration of a control system in the second embodiment, and is a diagram showing a discharging path in cell balance control by charging and discharging a secondary battery cell on the low potential side among a plurality of secondary battery cells. In the second embodiment, the description of the same configuration as in the above-mentioned embodiment will be omitted by invoking the above description.

[0066] 7 and 8, the external device 140 includes a current control circuit 30 that controls a current flowing through a wiring path including at least one of the internal wirings 85 and 86. The current control circuit 30 has a current source 38 connected in series to the internal wiring 86, and a switching circuit including a switch 27 connected in series to the current source 38.

[0067] 7 and 8 show a normal state in which no abnormality is detected in the secondary battery cells 201, 202. In the normal state shown in Fig. 7 and 8, the balance control circuit 33 charges the secondary battery cell 201 with a charging current flowing through the wiring path CR2 (see Fig. 7) or discharges the secondary battery cell 201 with a discharging current flowing through the wiring path DR1 (see Fig. 8), thereby making the cell voltage of the secondary battery cell 201 closer to the cell voltage of the secondary battery cell 202.

[0068] 7 shows a case where, in a normal state, the cell voltage of the secondary battery cell 201 is lower than the cell voltage of the secondary battery cell 202. When the balance control circuit 33 determines that the cell voltage of the secondary battery cell 201 is lower than the cell voltage of the secondary battery cell 202, the balance control circuit 33 charges the secondary battery cell 201 through the wiring path CR2 by switching the switch 27 from off to on in order to increase the cell voltage of the secondary battery cell 201. The secondary battery cell 201 is charged with a current output by a current source 38. The current source 38 is, for example, a constant current source.

[0069] 8 shows a case where, in a normal state, the cell voltage of the secondary battery cell 201 is higher than the cell voltage of the secondary battery cell 202. When the balance control circuit 33 determines that the cell voltage of the secondary battery cell 201 is higher than the cell voltage of the secondary battery cell 202, the balance control circuit 33 switches the switch 26 from off to on to discharge the secondary battery cell 201 through the wiring path DR1 in order to lower the cell voltage of the secondary battery cell 201. The secondary battery cell 201 is discharged with a current output by a current source 32. The current source 32 is, for example, a constant current source.

[0070] <Third embodiment> Fig. 9 is a diagram showing a configuration example of a control system in the third embodiment, and is a diagram showing a discharge path in cell balance control by discharging a secondary battery cell on the low potential side among multiple secondary battery cells. Fig. 10 is a diagram showing a configuration example of a control system in the third embodiment, and is a diagram showing a discharge path in cell balance control by discharging a secondary battery cell on the high potential side among multiple secondary battery cells. Fig. 11 is a diagram showing a configuration example of a control system in the third embodiment, and is a diagram showing a charge path in cell balance control by charging a secondary battery cell on the low potential side among multiple secondary battery cells. In the third embodiment, the description of the same configuration as in the above-mentioned embodiments will be omitted by invoking the above description.

[0071] In the control system 303 shown in Figures 9, 10, and 11, the protection IC 120 does not include the terminals BS1, BSL and the internal wiring 85. Figures 9, 10, and 11 show the case of a normal state in which no abnormality in the secondary battery cells 201, 202 is detected.

[0072] 9 shows a case where, in a normal state, the cell voltage of the secondary battery cell 201 is higher than the cell voltage of the secondary battery cell 202. When the balance control circuit 33 determines that the cell voltage of the secondary battery cell 201 is higher than the cell voltage of the secondary battery cell 202, the balance control circuit 33 switches the switch 26 from off to on to discharge the secondary battery cell 201 through the wiring path DR1 in order to lower the cell voltage of the secondary battery cell 201. The secondary battery cell 201 is discharged with a current output by a current source 32. The current source 32 is, for example, a constant current source.

[0073] 10 shows a case where, in a normal state, the cell voltage of the secondary battery cell 202 is higher than the cell voltage of the secondary battery cell 201. When the balance control circuit 33 determines that the cell voltage of the secondary battery cell 202 is higher than the cell voltage of the secondary battery cell 201, the balance control circuit 33 switches the switch 25 from off to on to discharge the secondary battery cell 202 through the wiring path DR2 in order to lower the cell voltage of the secondary battery cell 202. The secondary battery cell 202 is discharged with a current output by a current source 31. The current source 31 is, for example, a constant current source.

[0074] 11 shows a case where, in a normal state, the cell voltage of the secondary battery cell 201 is lower than the cell voltage of the secondary battery cell 202. When the balance control circuit 33 determines that the cell voltage of the secondary battery cell 201 is lower than the cell voltage of the secondary battery cell 202, the balance control circuit 33 charges the secondary battery cell 201 through the wiring path CR2 by switching the switch 27 from off to on in order to increase the cell voltage of the secondary battery cell 201. The secondary battery cell 201 is charged with a current output by a current source 38. The current source 38 is, for example, a constant current source.

[0075] <Fourth embodiment> FIG. 12 is a diagram showing a configuration example of a control system in the fourth embodiment, and is a diagram showing a discharge path in cell balance control by discharging a secondary battery cell on the low potential side among multiple secondary battery cells. FIG. 13 is a diagram showing a configuration example of a control system in the fourth embodiment, and is a diagram showing a charge / discharge path in cell balance control by discharging a secondary battery cell on the high potential side among multiple secondary battery cells or charging a secondary battery cell on the low potential side among multiple secondary battery cells. In the fourth embodiment, the description of the same configuration as in the above-mentioned embodiment is omitted by citing the above description. In the control system 301 in the above-mentioned embodiment, the cell balance discharge path through which the discharge current flows passes through the external device 140. In contrast, in the control system 304 shown in FIGS. 12 and 13 in the fourth embodiment, the cell balance discharge path through which the discharge current (excluding the control current described later) flows is on the battery pack 151 side.

[0076] 12 shows a case where, in a normal state, the cell voltage of the secondary battery cell 201 is higher than the cell voltage of the secondary battery cell 202. When the balance control circuit 33 determines that the cell voltage of the secondary battery cell 201 is higher than the cell voltage of the secondary battery cell 202, it switches the switch 29 from off to on in order to lower the cell voltage of the secondary battery cell 201. This generates a control current that flows through a wiring path DR5 from the positive electrode 201b of the secondary battery cell 201 to the negative electrode 201a of the secondary battery cell 201 via the terminal BM, the terminal VBM, the terminal BS2, the terminal BSM, the switch 29, the terminal P-, the switch circuit 13, and the terminal B-.

[0077] The secondary battery protection device 110 includes a current detection circuit 44 that detects a current flowing through the internal wiring 86 under the control of the balance control circuit 33, and a plurality of discharge circuits 36, 37 provided for the plurality of secondary battery cells 201, 202, respectively. The current detection circuit 44 and the discharge circuits 36, 37 are provided outside the battery IC 121 and mounted on a substrate. The discharge circuit 36 ​​discharges the corresponding secondary battery cell 201 of the secondary battery cells 201, 202 in accordance with the current detection result by the current detection circuit 44. The discharge circuit 37 discharges the corresponding secondary battery cell 202 of the secondary battery cells 201, 202 in accordance with the current detection result by the current detection circuit 44.

[0078] In this example, the current detection circuit 44 includes a resistive element R7 connected in series to the internal wiring 86, and detects a voltage drop occurring in the resistive element R7 due to the control current. The resistive element R7 is inserted in series in the current path between the terminal BM (negative electrode 202a) and the terminal VBM.

[0079] The discharge circuit 36 ​​includes a switch 41 that discharges the corresponding secondary battery cell 201 of the multiple secondary battery cells 201, 202 in response to a voltage drop occurring in the resistance element R7, and a resistance element R9 that is connected in series to the switch 41. A series circuit of the switch 41 and the resistance element R9 is connected in parallel to the secondary battery cell 201. The switch 41 is, for example, a P-channel MOS transistor having a source connected to one end of the resistance element R7, a drain connected to one end of the resistance element R9, and a gate connected to the other end (terminal VBM) of the resistance element R7. The other end of the resistance element R9 is connected to the terminal VSS.

[0080] The discharge circuit 37 includes a switch 40 that discharges the corresponding secondary battery cell 202 out of the multiple secondary battery cells 201, 202 in response to a voltage drop occurring in the resistance element R8, and a resistance element R8 that is connected in series to the switch 40. A series circuit of the switch 40 and the resistance element R8 is connected in parallel to the secondary battery cell 202. The switch 40 is, for example, an N-channel MOS transistor having a source connected to one end of the resistance element R7, a drain connected to one end of the resistance element R8, and a gate connected to the other end (terminal VBM) of the resistance element R7. The other end of the resistance element R8 is connected to the terminal VDD.

[0081] When the balance control circuit 33 turns on the switch 29 to allow a control current to flow, and the current detection circuit 44 detects a voltage drop equal to or greater than a threshold value using the resistance element R7, the discharge circuit 36 ​​performs cell balance discharge by turning on the switch 41 connected in parallel to the secondary battery cell 201. This generates a discharge current that flows through a wiring path DR4 from the positive electrode 201b of the secondary battery cell 201 to the negative electrode 201a of the secondary battery cell 201 via the terminal BM, the resistance element R9, the switch 41, and the terminal B-. The resistance element R9 is an element for adjusting (limiting) the current value of this discharge current.

[0082] 13 shows a case where, in a normal state, the cell voltage of the secondary battery cell 202 is higher than the cell voltage of the secondary battery cell 201. When the balance control circuit 33 determines that the cell voltage of the secondary battery cell 202 is higher than the cell voltage of the secondary battery cell 201, it switches the switch 28 from off to on in order to lower the cell voltage of the secondary battery cell 202. This generates a control current that flows through a wiring path CR4 from the power source V of the external device 140 to the positive electrode 201b of the secondary battery cell 201 via the switch 28, the terminal BSM, the terminal BS2, the terminal VBM, and the terminal BM.

[0083] When the balance control circuit 33 turns on the switch 28 to allow a control current to flow, and the current detection circuit 44 detects a voltage drop equal to or greater than a threshold value using the resistance element R7, the discharge circuit 37 performs cell balance discharge by turning on the switch 40 connected in parallel to the secondary battery cell 202. This generates a discharge current that flows through a wiring path DR6 from the positive electrode 202b of the secondary battery cell 202 through the terminal B+, the resistance element R1, the resistance element R8, the switch 40, and the terminal BM to the negative electrode 202a of the secondary battery cell 202. The resistance element R8 is an element for adjusting (limiting) the current value of this discharge current.

[0084] <Fifth embodiment> 14 is a diagram showing a configuration example of a control system in the fifth embodiment, and is a diagram showing a discharge path in cell balance control by discharging a secondary battery cell on the high potential side among a plurality of secondary battery cells. In the fifth embodiment, the description of the same configuration as in the above-mentioned embodiments will be omitted by citing the above description.

[0085] 14, the external device 140 includes a current control circuit 30 that controls a current flowing through a wiring path including at least one of the internal wirings 85, 86. The current control circuit 30 has a current source 31 connected in series to the internal wiring 86, and a switching circuit including a switch 25 connected in series to the current source 31.

[0086] Fig. 14 shows a normal state in which no abnormality is detected in the secondary battery cells 201, 202. In the normal state shown in Fig. 14, the balance control circuit 33 discharges the secondary battery cell 202 by a discharge current flowing through the wiring path DR2 (see Fig. 14) to make the cell voltage of the secondary battery cell 202 approach the cell voltage of the secondary battery cell 201.

[0087] 14 shows a case where, in a normal state, the cell voltage of the secondary battery cell 202 is higher than the cell voltage of the secondary battery cell 201. When the balance control circuit 33 determines that the cell voltage of the secondary battery cell 202 is higher than the cell voltage of the secondary battery cell 201, the balance control circuit 33 switches the switch 25 to the on state to lower the cell voltage of the secondary battery cell 202, thereby discharging the secondary battery cell 202 through the wiring path DR2.

[0088] Sixth Embodiment 15 is a diagram showing a configuration example of a control system in the sixth embodiment, and is a diagram showing a discharge path in cell balance control by discharging a secondary battery cell on the high potential side among a plurality of secondary battery cells. In the sixth embodiment, the description of the same configuration as in the above-mentioned embodiments will be omitted by citing the above description.

[0089] In the control system 306 shown in Fig. 15, the protection IC 120 includes a terminal VB2, and the substrate includes a terminal BSH. The internal wiring 86 connects the terminal VBM2 and the terminal BS2. The terminal VBM2 is connected to the terminal BM without a resistive element R2, and the terminal VBM1 is connected to the terminal BM through the resistive element R2. The terminal BSH is connected to the terminal B+ (positive electrode 202b) through a resistive element R6, and the terminal P+ is connected to the terminal B+ (positive electrode 202b) without a resistive element R6.

[0090] The protection IC 120 measures the cell voltage of the secondary battery cell 201 by detecting the potential difference between the terminal VBM1 and the terminal VSS, and measures the cell voltage of the secondary battery cell 202 by detecting the potential difference between the terminal VBM1 and the terminal VDD. This improves the measurement accuracy because the cell voltages of the secondary battery cells 201, 202 are measured via a wiring path different from the wiring path through which the discharge current flows.

[0091] Moreover, the balance control circuit 33 measures the cell voltage of the secondary battery cell 202 by detecting the potential difference between the terminals BSH and BSM, and measures the total cell voltage VC of the secondary battery cells 201, 202 by detecting the potential difference between the terminals BSH and BSL. This improves the measurement accuracy because the cell voltage of the secondary battery cell 202 and the total cell voltage VC of the secondary battery cells 201, 202 are measured via a wiring path different from the wiring path through which the discharge current flows.

[0092] In this way, in each of the above-mentioned embodiments, the external device 140 can monitor the cell voltages of the multiple secondary battery cells 201, 202 by bypassing the switch circuit 13, and the monitoring accuracy is high. Therefore, cell balance control is performed based on the monitoring results, and the balance of the cell voltages of the multiple secondary battery cells can be controlled with high accuracy. Also, since an internal switch is inserted in series in the internal wiring through which the external device 140 measures the cell voltages of the multiple secondary battery cells, the current generated in the internal wiring can be cut off by turning off the internal switch.

[0093] Although the control system, the control method, and the secondary battery protection integrated circuit have been described above by way of embodiments, the present invention is not limited to the above-described embodiments. Various modifications and improvements, such as combinations or replacements with part or all of the other embodiments, are possible within the scope of the present invention.

[0094] For example, the positions of the charge control transistor 11 and the discharge control transistor 12 may be interchanged with each other with respect to the positions shown in the figure. The switch circuit 13 may be built into the protection IC 120. The charger 130 may be mounted on a substrate. [Explanation of symbols]

[0095] 7,8 Power Path 13 Switch Circuit 21, 22, 23, 24 Internal Switch 25,26,27,28,29,40,41,42 Switch 30 Current control circuit 31,32,38 Current source 33 Balance control circuit 36,37 Discharge circuit 43 Internal Switch 44 Current detection circuit 51,52 Internal resistance 81 Discharge control circuit 82 Charging control circuit 83 Switch control circuit 85,86 Internal wiring 110 Secondary battery protection device 120,121 Protection IC 130 charger 140 External equipment 141,142 Parasitic Diode 143 resistance 151 Battery Pack 201,202 Secondary battery cell 201a,202a negative electrode 201b,202b positive electrode 301, 302, 303, 304, 305, 306 Control Systems

Claims

1. A plurality of secondary battery cells connected in series; a power supply path connected in series to the plurality of secondary battery cells; At least one switch element inserted in series in the power supply path; a secondary battery protection device that protects the plurality of secondary battery cells by controlling the switch elements; an external device that controls a balance of the cell voltages of the plurality of secondary battery cells; The secondary battery protection device includes: an abnormality detection circuit that detects overcharging or overdischarging by monitoring the voltage of all or each of the plurality of secondary battery cells; a first monitor terminal connected to the external device and a second monitor terminal connected to the secondary battery cell, the first monitor terminal being provided so as to be capable of monitoring a potential of one or more electrodes, including an electrode to which the switch element is connected, among the electrodes of the plurality of secondary battery cells, via a path that does not include the switch element; one or more internal wirings interposed at least between the first monitor terminal and the second monitor terminal; one or more internal switches that are inserted in series with the one or more internal wirings, respectively, and that cut off a current flowing through the internal wirings when an overcharge or overdischarge is detected by the abnormality detection circuit; a switch control circuit that turns on or off each of the internal switches in response to a result of the abnormality detection by the abnormality detection circuit; The switch control circuit turns off the internal switch when at least one of the plurality of secondary battery cells is in an over-discharged state.

2. The control system according to claim 1 , wherein the switch control circuit turns on the internal switch when a charger is connected via the secondary battery protection device.

3. a current control circuit for controlling a current flowing through a wiring path including at least one of the one or more internal wirings, The control system according to claim 1 , wherein the external device controls the current control circuit to control a balance of the cell voltages of the plurality of secondary battery cells.

4. the current control circuit has a switching circuit that switches between conductive and non-conductive states of the wiring path, The control system according to claim 3 , wherein the external device controls the switching circuit to control a balance of the cell voltages of the plurality of secondary battery cells.

5. The control system according to claim 4 , wherein the switching circuit includes a plurality of switches connected in parallel to corresponding ones of the plurality of secondary battery cells.

6. the current control circuit includes a plurality of current sources connected in parallel to corresponding ones of the plurality of secondary battery cells, and a plurality of switches connected in series to corresponding ones of the plurality of current sources; The control system according to claim 3 , wherein the external device controls a balance of the cell voltages of the plurality of secondary battery cells by controlling the plurality of current sources and the plurality of switches.

7. The plurality of secondary battery cells include a first secondary battery cell having a first positive electrode and a first negative electrode having a lowest potential among the negative electrodes of the plurality of secondary battery cells; a second secondary battery cell having a second positive electrode and a second negative electrode connected to the first positive electrode; The one or more monitor terminals include: The control system according to claim 1 , further comprising a monitor terminal arranged to be able to monitor the potential of the second negative electrode.

8. A control method performed by a secondary battery protection circuit that protects a plurality of secondary battery cells connected in series by controlling at least one switch element inserted in series in a power supply path connected in series to the plurality of secondary battery cells, the method comprising: The secondary battery protection circuit includes: an abnormality detection circuit that detects overcharging or overdischarging by monitoring the voltage of all or each of the plurality of secondary battery cells; a first monitor terminal connected to an external device and a second monitor terminal connected to the secondary battery cell, the first monitor terminal being provided so as to be capable of monitoring a potential of one or more electrodes, including an electrode to which the switch element is connected, among the electrodes of the plurality of secondary battery cells, via a path not including the switch element; one or more internal wirings interposed at least between the first monitor terminal and the second monitor terminal; one or more internal switches that are inserted in series with the one or more internal wirings, respectively, and that cut off a current flowing through the internal wirings when an overcharge or overdischarge is detected by the abnormality detection circuit; a switch control circuit that turns on or off each of the internal switches in response to a result of the abnormality detection by the abnormality detection circuit; The switch control circuit turns off the internal switch when at least one of the plurality of secondary battery cells is in an over-discharged state.

9. A secondary battery protection integrated circuit that protects a plurality of secondary battery cells connected in series by controlling at least one switch element inserted in series in a power supply path connected in series to the plurality of secondary battery cells, an abnormality detection circuit that detects overcharging or overdischarging by monitoring the voltage of all or each of the plurality of secondary battery cells; a first monitor terminal connected to an external device and a second monitor terminal connected to the secondary battery cell, the first monitor terminal being provided so as to be capable of monitoring a potential of one or more electrodes, including an electrode to which the switch element is connected, among the electrodes of the plurality of secondary battery cells, via a path not including the switch element; one or more internal wirings interposed at least between the first monitor terminal and the second monitor terminal; one or more internal switches that are inserted in series with the one or more internal wirings, respectively, and that cut off a current flowing through the internal wirings when an overcharge or overdischarge is detected by the abnormality detection circuit; a switch control circuit that turns on or off each of the internal switches in response to a result of the abnormality detection by the abnormality detection circuit; The switch control circuit turns off the internal switch when at least one of the plurality of secondary battery cells is in an over-discharge state.

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