Battery monitoring module and power supply system

Abstract

To provide a battery monitoring module capable of reducing the consumption current during an over-discharge state of a secondary battery.SOLUTION: The battery monitoring module includes a protection circuit for detecting over-discharge of a secondary battery, and a monitoring circuit that operates using a supply voltage from the protection circuit and monitors the current flowing through the secondary battery. The protection circuit supplies a first voltage to the monitoring circuit, causing the monitoring circuit to enter a sleep state, in a first state where the over-discharge is detected.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a battery monitoring module and a power supply system. [Background technology]

[0002] BACKGROUND ART Conventionally, a protection IC has been known that has a voltage regulator that regulates a power supply voltage supplied to a power supply terminal and supplies the regulated power supply voltage to a secondary battery monitoring IC (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5564955 Summary of the Invention [Problem to be solved by the invention]

[0004] However, if the supply of voltage to a monitoring circuit such as a secondary battery monitoring IC continues when the over-discharge of the secondary battery is detected by a protection circuit such as a protection IC, the over-discharge of the secondary battery 210 may progress further due to the current consumption of the circuit.

[0005] The present disclosure provides a battery monitoring module and a power supply system that can reduce current consumption when a secondary battery is in an over-discharge state. [Means for solving the problem]

[0006] The battery monitoring module of the first aspect includes: a protection circuit for detecting over-discharge of the secondary battery; a monitoring circuit that operates using a voltage supplied from the protection circuit and monitors a current flowing through the secondary battery, In a first state in which the over-discharge is detected, the protection circuit supplies a first voltage to the monitoring circuit, which causes the monitoring circuit to enter a sleep state.

[0007] The power supply system of the second aspect is A secondary battery; a protection circuit for detecting over-discharge of the secondary battery; a monitoring circuit that operates using a voltage supplied from the protection circuit and monitors a current flowing through the secondary battery, In a first state in which the over-discharge is detected, the protection circuit supplies a first voltage to the monitoring circuit, which causes the monitoring circuit to enter a sleep state. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to reduce current consumption when a secondary battery is in an over-discharged state. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a circuit block diagram showing an example of a system including a protection circuit according to a first embodiment. [Figure 2] 10A and 10B are diagrams illustrating an example of an operation when the protection circuit transitions to an over-discharge protection state and when it returns from the over-discharge protection state. [Figure 3] 5 is a diagram showing an example of an operation in which the protection circuit according to the first embodiment reduces the voltage supplied to the monitoring circuit when the secondary battery is in an over-discharge state. FIG. [Figure 4] FIG. 2 is a diagram illustrating an example of the configuration of a protection circuit according to the first embodiment. [Figure 5] 2 is a diagram showing an example of the configuration of a voltage generating circuit provided in the protection circuit according to the first embodiment; FIG. [Figure 6] 5A and 5B are diagrams illustrating an example of the operation of the voltage generating circuit included in the protection circuit according to the first embodiment. [Figure 7] FIG. 10 is a circuit block diagram showing an example of a system including a protection circuit according to a modified example of the first embodiment. [Figure 8] FIG. 10 is a circuit block diagram showing an example of a system including a protection circuit according to a second embodiment. [Figure 9] 10A and 10B are diagrams illustrating an example of an operation when the protection circuit transitions to an over-discharge protection state and when it returns from the over-discharge protection state. [Figure 10] 10 is a diagram showing an example of an operation of the protection circuit according to the second embodiment to reduce the voltage supplied to the monitoring circuit when the secondary battery is in an over-discharge state. FIG. [Figure 11] FIG. 10 is a diagram illustrating an example of the configuration of a protection circuit according to a second embodiment. [Figure 12] FIG. 10 is a diagram illustrating an example of the configuration of a voltage generating circuit included in a protection circuit according to a second embodiment. [Figure 13] 10A and 10B are diagrams illustrating an example of the operation of a voltage generating circuit included in the protection circuit according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0011] Fig. 1 is a circuit block diagram showing an example of a system including a protection circuit according to the first embodiment. The system 501 shown in Fig. 1 includes a battery device 401 and an electronic device 300. The system 501 may also include a charger 302 that charges the battery device 401.

[0012] The electronic device 300 is an example of a load that consumes power supplied from the battery device 401. Specific examples of the load include a mobile phone, a smartphone, a tablet device, and earphones. However, the electronic device 300 is not limited to these devices.

[0013] When connected to a battery device 401, the electronic device 300 operates on power supplied from the battery device 401. A charger 302 that charges the battery device 401 is connected to the electronic device 300. Note that the electronic device 300 itself may be a charger that charges the battery device 401.

[0014] The electronic device 300 has a connector 305, a PMIC (Power Management Integrated Circuit) 303, and an internal circuit 304. The connector 305 is a component for electrically connecting the electronic device 300 and the charger 302. The PMIC 303 is a circuit that controls charging of the secondary battery 210 in the battery device 401. The PMIC 303 controls the charging current supplied from the charger 302 to the secondary battery 210 in the battery device 401. The internal circuit 304 is a circuit within the electronic device 300. Examples of the internal circuit 304 include a processor such as a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and an interface circuit.

[0015] The PMIC 303 or the internal circuit 304 receives battery information (e.g., information about the remaining capacity of the secondary battery 210) supplied from the terminal I / F of the battery device 401. The PMIC 303 or the internal circuit 304 performs a predetermined process based on the received battery information. For example, the internal circuit 304 performs a process of displaying the remaining capacity of the secondary battery 210 on a display provided in the electronic device 300.

[0016] The battery device 401 is an example of a power supply system that supplies power to the electronic device 300. The battery device 401 may be external to the electronic device 300 or may be built into the electronic device 300. The battery device 401 is, for example, a battery pack that is detachably attached to the electronic device 300. The battery device 401 may be in a form other than a battery pack.

[0017] The battery device 401 and the electronic device 300 are connected to each other via a plurality of terminals (in this example, an interface terminal (terminal I / F), a positive power supply terminal (terminal P+), and a negative power supply terminal (terminal P-)). For example, the terminals P+ and P- are electrically connected to the charger 302 when charging the secondary battery 210.

[0018] The battery device 401 includes a secondary battery 210 and a battery monitoring device 601 .

[0019] The secondary battery 210 is an example of a chargeable and dischargeable battery. The secondary battery 210 supplies power to the electronic device 300 connected to the terminals P+ and P-. The secondary battery 210 can be charged by a charger 302 electrically connected to the terminals P+ and P-. Specific examples of the secondary battery 210 include a lithium ion battery and a lithium polymer battery. The secondary battery 210 has a positive electrode 211 and a negative electrode 212.

[0020] The battery monitoring device 601 is an example of a battery monitoring module that monitors the secondary battery 210, and transmits battery information including the monitoring results of the secondary battery 210 to the electronic device 300 via the terminal I / F. The battery monitoring device 601 operates using the secondary battery 210 as a power source.

[0021] The battery monitoring device 601 includes, for example, a terminal P+, a terminal P-, a terminal I / F, a terminal B+, a terminal B-, resistive elements R21, R23, and Rsns, a capacitor C21, a power supply line 201, a ground line 202, a switch circuit 203, a protection IC 101, and a fuel gauge IC 701. IC is an abbreviation for Integrated Circuit.

[0022] The battery monitoring device 601 is a component that includes a board on which at least the protection IC 101 or the fuel gauge IC 701 is mounted, for example.

[0023] Terminal P+ is an example of a first positive terminal for connecting a load, and is connected to the power line of the electronic device 300. Terminal P- is an example of a first negative terminal for connecting a load, and is connected to the ground line of the electronic device 300. Terminal B+ is an example of a second positive terminal for connecting a secondary battery, and is connected to the positive electrode 211 of the secondary battery 210. Terminal B- is an example of a second negative terminal for connecting a secondary battery, and is connected to the negative electrode 212 of the secondary battery 210.

[0024] Terminal B+ and terminal P+ are connected by a power line 201, which is a positive power path. The power line 201 is an example of a first current path that connects terminal B+ and terminal P+. The power line 201 functions as a charging path through which a charging current of the secondary battery 210 flows and a discharging path through which a discharging current of the secondary battery 210 flows.

[0025] Terminal B- and terminal P- are connected by a ground line 202, which is a negative power supply path. The ground line 202 is an example of a second current path that connects terminal B- and terminal P-. The ground line 202 functions as a charge path through which a charging current of the secondary battery 210 flows and a discharge path through which a discharging current of the secondary battery 210 flows.

[0026] The switch circuit 203 is provided in the power supply line 201 between the terminal B+ and the terminal P+. The switch circuit 203 is, for example, a series circuit including a charge control transistor TR1 and a discharge control transistor TR2 connected in series. The charge control transistor TR1 is a semiconductor switching element that cuts off the charge path of the secondary battery 210. The discharge control transistor TR2 is a semiconductor switching element that cuts off the discharge path of the secondary battery 210.

[0027] 1, the charge control transistor TR1 cuts off the power supply line 201 through which the charging current of the secondary battery 210 flows, and the discharge control transistor TR2 cuts off the power supply line 201 through which the discharging current of the secondary battery 210 flows. The charge control transistor TR1 and the discharge control transistor TR2 are switching elements that switch the power supply line 201 between conducting and cutting off, and are inserted in series in the power supply line 201. The charge control transistor TR1 and the discharge control transistor TR2 are, for example, N-channel MOSFETs (Metal Oxide Semiconductor Field Effect Transistors).

[0028] The charge control transistor TR1 has a parasitic diode D1 between its drain and source, whose forward direction is opposite to the direction of the charging current of the secondary battery 210. The charge control transistor TR1 is a switching element inserted in series with the power supply line 201 so that the forward direction of the parasitic diode D1 coincides with the direction of the discharging current of the secondary battery 210.

[0029] The discharge control transistor TR2 has a parasitic diode D2 between its drain and source, whose forward direction is opposite to the direction of the discharge current of the secondary battery 210. The discharge control transistor TR2 is a switch element inserted in series with the power line 201 so that the forward direction of the parasitic diode D2 coincides with the direction in which the charge current of the secondary battery 210 flows.

[0030] The protection IC 101 is an example of a protection circuit used to protect a secondary battery. The protection IC 101 operates using the secondary battery 210 as a power source. The protection IC 101 is a secondary battery protection integrated circuit that includes, for example, a circuit that protects the secondary battery 210 from overcharging and the like by controlling the charging of the secondary battery 210, and a circuit that protects the secondary battery 210 from overdischarging and the like by controlling the discharging of the secondary battery 210.

[0031] The protection IC 101 has a function of protecting the secondary battery 210 from over-discharge and the like by controlling the switch circuit 203. For example, when the detection circuit 222 detects abnormal charging (e.g., over-charge, overcurrent in the charging direction (charging overcurrent)), the protection IC 101 protects the secondary battery 210 from abnormal charging by turning off the charge control transistor TR1. On the other hand, when the detection circuit 222 detects abnormal discharging (e.g., over-discharge, overcurrent in the discharging direction (discharging overcurrent)), the protection IC 101 protects the secondary battery 210 from abnormal discharging by turning off the discharge control transistor TR2.

[0032] The protection IC 101 includes, for example, a charge control terminal (terminal COUT), a discharge control terminal (terminal DOUT), a power supply terminal (terminal VDD), a ground terminal (terminal VSS), a current detection terminal (terminal CS), a monitoring terminal (terminal VP), and an output terminal (terminal VOUT). These terminals are, for example, external connection terminals for connecting the internal circuit of the protection IC 101 to the outside of the protection IC 101.

[0033] The terminal COUT is connected to the gate (control electrode) of the charge control transistor TR1 and outputs a signal to turn the charge control transistor TR1 on or off. The terminal DOUT is connected to the gate (control electrode) of the discharge control transistor TR2 and outputs a signal to turn the discharge control transistor TR2 on or off.

[0034] The terminal VDD is a power supply terminal of the protection IC 101, and is connected to the positive electrode 211 of the secondary battery 210 and the power supply line 201. The terminal VSS is a ground terminal of the protection IC 101, and is connected to the negative electrode 212 of the secondary battery 210 and the ground line 202 via a resistor element R21. A capacitor C21 is connected between the terminals VDD and VSS. The terminal VDD is connected to the power supply line 201 between the switch circuit 203 and the positive electrode 211. In this example, the terminal VDD is connected to the power supply line 201 between the charge control transistor TR1 and the positive electrode 211. The protection IC 101 operates on a power supply voltage Vdd applied between the terminals VDD and VSS.

[0035] Terminal CS is a current detection terminal used to detect a charging current or a discharging current flowing through the secondary battery 210. Terminal CS is connected to the power supply line 201 between terminal P+ and switch circuit 203 (the source of the discharge control transistor TR2). Resistance element Rsns inserted in series with the power supply line 201 has one end connected to terminal CS and the other end connected to terminal P+ and to terminal VP via resistance element R23. Detection circuit 222 in protection IC 101 detects the potential difference between terminal CS and terminal VP to detect a charging overcurrent or a discharging overcurrent flowing through the secondary battery 210. Resistance element Rsns functions as a sense resistor that detects a current I (charging current or discharging current) flowing through the secondary battery 210.

[0036] The terminal VP is an example of a monitoring terminal used to monitor the potential of the terminal P+. The terminal VP is used, for example, by the control circuit 221 in the protection IC 101 to monitor whether the electronic device 300 or the charger 302 is connected. The terminal VP is connected to the power supply line 201 between the switch circuit 203 and the terminal P+ via a resistor element R23. The terminal VP is electrically connected to the power supply line 201 on the opposite side of the switch circuit 203 from the secondary battery 210.

[0037] Terminal VOUT is an example of a first terminal that outputs a voltage to be supplied to the monitoring circuit, and is connected to terminal BAT of fuel gauge IC 701. Terminal VOUT outputs voltage Vb generated by voltage generation circuit 227 in protection IC 101 to fuel gauge IC 701 as the power supply voltage for fuel gauge IC 701.

[0038] The protection IC 101 includes a voltage generating circuit 227 , a detecting circuit 222 , and a control circuit 221 .

[0039] The voltage generation circuit 227 generates a voltage Vb to be supplied to the fuel gauge IC 701 from the power supply voltage Vdd applied between the terminals VDD and VSS. The voltage generation circuit 227 has the function of lowering and raising the voltage Vb. The voltage generation circuit 227 includes, for example, a voltage regulator that regulates the power supply voltage Vdd and generates the regulated voltage Vb. The voltage Vb generated by the voltage generation circuit 227 is supplied to the fuel gauge IC 701 via the terminal VOUT.

[0040] The detection circuit 222 monitors the power supply voltage Vdd between the terminals VDD and VSS to detect overcharge of the secondary battery 210. The detection circuit 222 compares the power supply voltage Vdd with a predetermined overcharge detection voltage Vdet1, and when the power supply voltage Vdd is higher than the overcharge detection voltage Vdet1, generates an overcharge detection signal indicating that overcharge of the secondary battery 210 has been detected.

[0041] The detection circuit 222 detects a charging overcurrent of the secondary battery 210 by monitoring the potential difference ΔV1 between the terminals CS and VP. The detection circuit 222 compares the potential difference ΔV1 with a predetermined charging overcurrent detection voltage Vdet4, and when the potential difference ΔV1 is higher than the charging overcurrent detection voltage Vdet4 with respect to the terminal CS, the detection circuit 222 generates a charging overcurrent detection signal indicating that a charging overcurrent of the secondary battery 210 has been detected. In other words, the detection circuit 222 generates the charging overcurrent detection signal when the voltage of the terminal VP is higher than the charging overcurrent detection voltage Vdet4 with respect to the terminal CS.

[0042] The control circuit 221 controls the charging of the secondary battery 210. When the detection circuit 222 detects overcharging of the secondary battery 210 for a predetermined detection delay time tVdet1, the control circuit 221 outputs a signal (for example, a low-level gate control signal) that switches the charge control transistor TR1 from on to off from the terminal COUT. When the detection circuit 222 detects a charging overcurrent of the secondary battery 210 for a predetermined detection delay time tVdet4, the control circuit 221 outputs a signal (for example, a low-level gate control signal) that switches the charge control transistor TR1 from on to off from the terminal COUT.

[0043] By turning off the charge control transistor TR1, the control circuit 221 prohibits current flowing in the direction of charging the secondary battery 210 from flowing through the power line 201. This stops charging of the secondary battery 210, allowing the protection IC 101 to protect the secondary battery 210 from overcharging or charging overcurrent.

[0044] The detection circuit 222 detects recovery from overcharge of the secondary battery 210 by monitoring the power supply voltage Vdd between terminals VDD and VSS. The detection circuit 222 compares the power supply voltage Vdd with a predetermined overcharge recovery voltage Vrel1, and when the power supply voltage Vdd is lower than the overcharge recovery voltage Vrel1, generates an overcharge recovery signal indicating that recovery from overcharge of the secondary battery 210 has been detected. The overcharge recovery voltage Vrel1 is lower than the overcharge detection voltage Vdet1.

[0045] The detection circuit 222 compares the potential of the terminal VP with a state detection threshold that is lower than the potential of the terminal VDD, and when the potential of the terminal VP is lower than the state detection threshold, generates a load connection signal that indicates a state in which a load such as the electronic device 300 is connected to the terminal P+. This is because when a load such as the electronic device 300 is connected to the terminals P+ and P-, the potential of the terminal VP drops, increasing the potential difference between the terminals VDD and VP.

[0046] When the charge control transistor TR1 is turned off due to the detection of overcharge, the protection IC 101 transitions to a state (overcharge protection state) in which the secondary battery 210 is protected from overcharge by turning off the charge control transistor TR1. If, in the overcharge protection state, the overcharge recovery of the secondary battery 210 is detected continuously for a predetermined recovery delay time tVrel1 and an electrical connection with a load is detected between the terminal P+ and the terminal P-, the control circuit 221 outputs a signal (for example, a high-level gate control signal) from the terminal COUT to switch the charge control transistor TR1 from off to on. This cancels the overcharge protection operation by the protection IC 101, and the protection IC 101 recovers from the overcharge protection state.

[0047] The detection circuit 222 monitors the power supply voltage Vdd between the terminals VDD and VSS to detect over-discharge of the secondary battery 210. The detection circuit 222 compares the power supply voltage Vdd with a predetermined over-discharge detection voltage Vdet2, and when the power supply voltage Vdd is lower than the over-discharge detection voltage Vdet2, generates an over-discharge detection signal indicating that over-discharge of the secondary battery 210 has been detected.

[0048] The detection circuit 222 detects a discharge overcurrent of the secondary battery 210 by monitoring the potential difference ΔV1 between terminals CS and VP. The detection circuit 222 compares the potential difference ΔV1 with a predetermined discharge overcurrent detection voltage Vdet3, and when the potential difference ΔV1 is lower than the discharge overcurrent detection voltage Vdet3 with respect to terminal CS, the detection circuit 222 generates a discharge overcurrent detection signal indicating that a discharge overcurrent of the secondary battery 210 has been detected. In other words, the detection circuit 222 generates a discharge overcurrent detection signal when the voltage of terminal VP is lower than the discharge overcurrent detection voltage Vdet3 with respect to terminal CS.

[0049] The control circuit 221 controls the discharge of the secondary battery 210. When the detection circuit 222 detects over-discharge of the secondary battery 210 for a predetermined detection delay time tVdet2, the control circuit 221 outputs a signal (for example, a low-level gate control signal) that switches the discharge control transistor TR2 from on to off from the terminal DOUT. When the detection circuit 222 detects a discharge overcurrent of the secondary battery 210 for a predetermined detection delay time tVdet3, the control circuit 221 outputs a signal (for example, a low-level gate control signal) that switches the discharge control transistor TR2 from on to off from the terminal DOUT.

[0050] By turning off the discharge control transistor TR2, the control circuit 221 prohibits current flowing in a direction that discharges the secondary battery 210 from flowing through the power line 201. This stops the discharge of the secondary battery 210, allowing the protection IC 101 to protect the secondary battery 210 from over-discharge or discharge overcurrent.

[0051] The detection circuit 222 detects recovery from over-discharge of the secondary battery 210 by monitoring the power supply voltage Vdd between the terminals VDD and VSS. The detection circuit 222 compares the power supply voltage Vdd with a predetermined over-discharge recovery voltage Vrel2, and when the power supply voltage Vdd is higher than the over-discharge recovery voltage Vrel2, generates an over-discharge recovery signal indicating that recovery from over-discharge of the secondary battery 210 has been detected. The over-discharge recovery voltage Vrel2 is higher than the over-discharge detection voltage Vdet2.

[0052] The detection circuit 222 compares the potential of the terminal VP with a state detection threshold that is lower than the potential of the terminal VDD, and when the potential of the terminal VP is higher than the state detection threshold, generates a charger connection signal that indicates that the charger 302 is electrically connected to the terminal P+. This is because when the charger 302 is electrically connected to the terminals P+ and P-, the potential difference between the terminals VDD and VP becomes smaller due to the increase in the potential of the terminal VP.

[0053] When the discharge control transistor TR2 is turned off due to the detection of over-discharge, the protection IC 101 transitions to a state (over-discharge protection state) in which the secondary battery 210 is protected from over-discharge by turning off the discharge control transistor TR2. If, in the over-discharge protection state, the over-discharge recovery of the secondary battery 210 is continuously detected for a predetermined recovery delay time tVrel2 and an electrical connection with the charger 302 is detected between the terminal P+ and the terminal P-, the control circuit 221 outputs a signal (for example, a high-level gate control signal) from the terminal DOUT that switches the discharge control transistor TR2 from off to on. This cancels the over-discharge protection operation by the protection IC 101, and the protection IC 101 recovers from the over-discharge protection state.

[0054] The fuel gauge IC701 is an example of a monitoring circuit that monitors the current I flowing through the secondary battery 210. The fuel gauge IC701 detects the current I flowing through the secondary battery 210 and measures the remaining amount (remaining capacity) of the secondary battery 210 using the result of integrating the current value of the detected current I.

[0055] Fuel gauge IC701 includes, for example, a power supply terminal (terminal BAT), a ground terminal (terminal GND), a current detection terminal (terminal IN1), a current detection terminal (terminal IN2), and an interface terminal (terminal A). These terminals are, for example, external connection terminals for connecting the internal circuitry of fuel gauge IC701 to the outside of fuel gauge IC701.

[0056] The terminal BAT is a power supply terminal of the monitoring IC 701 and is connected to the terminal VOUT of the protection IC 101. The terminal BAT is an example of a second terminal connected to the terminal VOUT, which is an example of a first terminal. The terminal GND is a ground terminal of the monitoring IC 701 and is connected to the negative electrode 212 of the secondary battery 210 and the ground line 202. The fuel gauge IC 701 operates on a power supply voltage (voltage Vb supplied from the protection circuit IC101) applied between the terminal BAT and the terminal GND.

[0057] Terminal IN1 is connected to one end of resistor Rsns. Terminal IN2 is connected to the other end of resistor Rsns. Resistor Rsns is an example of a resistor used for current detection in a monitoring circuit. Fuel gauge IC701 detects current I flowing through secondary battery 210 by monitoring the potential difference ΔIN between terminal IN1 and terminal IN2 (the voltage generated across resistor Rsns). The larger the potential difference ΔIN, the larger the value of current I. Fuel gauge IC701 detects the value of current I corresponding to the magnitude of potential difference ΔIN.

[0058] When the potential of terminal IN2 is higher than the potential of terminal IN1, fuel gauge IC701 determines that current I is a charging current of secondary battery 210, and when the potential of terminal IN2 is lower than the potential of terminal IN1, it determines that current I is a discharging current of secondary battery 210.

[0059] The resistive element Rsns is provided on the power supply line 201 between the transistors TR1, TR2 and the terminal P+. As a result, even if an abnormal current path occurs between the terminal IN1 and the terminal A or the like due to a malfunction of the fuel gauge IC 701 and an overcurrent flows, the overcurrent protection by the protection IC 101 will work, improving the reliability of the battery monitoring device 601.

[0060] The fuel gauge IC 701 measures the remaining capacity of the secondary battery 210 using the detected value of the current I, and outputs information including the measurement value as battery information from the terminal A. The battery information including the measurement value of the remaining capacity is transmitted to the electronic device 300 via the terminal A and the terminal I / F.

[0061] The fuel gauge IC 701 includes a memory 702 that stores data d obtained by monitoring the current I. The data d may include a detected value of the current I or a measured value of the remaining capacity of the secondary battery 210. Examples of the memory 702 include a volatile memory and a non-volatile memory.

[0062] Next, an example of the operation when the protection circuit transitions to an over-discharge protection state and when it returns from the over-discharge protection state will be described.

[0063] Figure 2 shows an example of the operation of the protection circuit when it transitions to an over-discharge protection state and when it returns from the over-discharge protection state. The vertical axis of Figure 2 represents voltage, and the horizontal axis represents time. The solid line represents the voltage at terminal P+, the dotted line represents the voltage at terminal B+, and the dashed-dotted line represents voltage Vb.

[0064] The protection IC 101 detects over-discharge of the secondary battery 210 when the power supply voltage Vdd is lower than the over-discharge detection voltage Vdet2. When the protection IC 101 detects over-discharge of the secondary battery 210, it turns off the discharge control transistor TR2 to block the flow of discharge current of the secondary battery 210, thereby protecting the secondary battery 210 from over-discharge (over-discharge protection state). To return the protection IC 101 from the over-discharge protection state, the charger 302 is connected to the terminals P+ and P-. In the over-discharge protection state, when the power supply voltage Vdd rises to or exceeds the over-discharge recovery voltage Vrel2 and an electrical connection between the terminal P+ and the charger 302 is detected, the protection IC 101 switches the discharge control transistor TR2 from off to on. This cancels the over-discharge protection operation by the protection IC 101, and the protection IC 101 returns from the over-discharge protection state.

[0065] If the voltage supply to the fuel gauge IC 701 continues when the protection IC 101 detects over-discharge of the secondary battery 210, the over-discharge of the secondary battery 210 may progress further due to the current consumption of circuits such as the fuel gauge IC 701. If the over-discharge of the secondary battery 210 progresses further, the deterioration of the secondary battery 210 may progress.

[0066] 2, when over-discharge of the secondary battery 210 is detected, the protection IC 101 cuts off the supply of voltage Vb to the fuel gauge IC 701, thereby reducing the current consumption of the fuel gauge IC 701. However, if the power supply to the memory 702 in the fuel gauge IC 701 is suddenly cut off due to the cutoff of voltage Vb, there is a risk that the data d stored in the memory 702 will be lost.

[0067] 3 is a diagram showing an example of the operation of the protection circuit according to the first embodiment to reduce the voltage supplied to the monitoring circuit when the secondary battery is in an over-discharge state. The vertical axis of FIG. 3 represents voltage, and the horizontal axis represents time. The solid line represents the voltage at terminal P+, the dotted line represents the voltage at terminal B+, and the dashed-dotted line represents voltage Vb.

[0068] As shown in FIG. 3 , in a first state (overdischarge state) in which overdischarge of the secondary battery 210 is detected, the protection IC 101 according to the first embodiment reduces the voltage Vb supplied to the fuel gauge IC 701 to a voltage Vr at which the fuel gauge IC 701 enters a sleep state. When the fuel gauge IC 701 enters the sleep state, the power consumption of the fuel gauge IC 701 decreases. The voltage Vr is lower than the voltage at which the protection IC 101 detects overdischarge (the overdischarge detection voltage Vdet2) and higher than the voltage Vreset at which data d stored in the memory 702 is lost. Therefore, when overdischarge of the secondary battery 210 is detected, the protection IC 101 supplies the fuel gauge IC 701 with the voltage Vr at which the fuel gauge IC 701 enters a sleep state, thereby reducing the current consumption of the fuel gauge IC 701 so that data d is not lost. This reduces the current consumption of the secondary battery 210 in an overdischarge state. By reducing the current consumption in the over-discharge state of the secondary battery 210, the progress of the over-discharge of the secondary battery 210 is suppressed, and therefore the progress of deterioration of the secondary battery 210 is also suppressed.

[0069] When voltage Vb drops below voltage Vsleep, fuel gauge IC701 transitions from a normal monitoring state, in which it performs operations such as monitoring current I, to a sleep state in which circuit operations such as monitoring current I are stopped. When voltage Vb drops below voltage Vreset, which is lower than voltage Vsleep, the circuit operation of fuel gauge IC701 is reset, increasing the risk of data d stored in memory 702 being lost. Voltage Vr, at which fuel gauge IC701 enters the sleep state, is higher than voltage Vreset and lower than voltage Vsleep. The sleep state of fuel gauge IC701 is a state in which circuit operations such as monitoring current I are stopped.

[0070] In the over-discharge protection state, the protection IC 101 transitions from the over-discharge protection state to the normal state when the power supply voltage Vdd rises to or exceeds the over-discharge recovery voltage Vrel2 and an electrical connection between the terminal P+ and the charger 302 is detected. In the normal state, the protection IC 101 raises the voltage Vb supplied to the fuel gauge IC 701 to a voltage higher than the voltage Vr and the voltage Vsleep (for example, a voltage equal to the voltage Vdd supplied from the secondary battery 210 to the protection IC 101). In the normal state, the protection IC 101 can transition the fuel gauge IC 701 from the sleep state to the normal monitoring state by supplying a voltage higher than the voltage Vr and the voltage Vsleep from the terminal VOUT to the fuel gauge IC 701.

[0071] Because voltage Vb is maintained above voltage Vreset in the over-discharge protection state, data d saved in memory 702 in the sleep state remains the data from the normal state immediately before transitioning to the over-discharge protection state (the monitoring state immediately before transitioning to the sleep state). Therefore, when the fuel gauge IC 701 transitions from the sleep state to the normal monitoring state, it can resume measuring the remaining capacity and the like of secondary battery 210 using data d that has a history before over-discharge detection. This improves the reliability of the measurement results of remaining capacity and the like by fuel gauge IC 701.

[0072] In this way, the protection IC 101 can easily transition the fuel gauge IC 701 between the sleep state and the monitoring state by changing the voltage Vb supplied to the fuel gauge IC 701.

[0073] 4 is a diagram showing an example of the configuration of the protection circuit according to the first embodiment. The protection IC 101 has a state detection circuit 226, a detection circuit 222, a control circuit 221, and a voltage generation circuit 227. The state detection circuit 226 may be included in the detection circuit 222. The control circuit 221 has a charge control circuit 221a and a discharge control circuit 221b.

[0074] When the potential of the terminal VP is lower than the status detection threshold (=potential of the terminal VDD−predetermined voltage VREF2), the status detection circuit 226 determines that a load is connected to the terminals P+ and P− and that discharging has commenced for the secondary battery 210. In this case, the status detection circuit 226 makes the load connection signal Sa active (high level in this example) and makes the charger connection signal Sb inactive (low level in this example).

[0075] When the potential of the terminal VP is higher than the status detection threshold (=potential of the terminal VDD−predetermined voltage VREF2), the status detection circuit 226 determines that the charger is connected to the terminals P+ and P− and that charging of the secondary battery 210 has begun. In this case, the status detection circuit 226 makes the load connection signal Sa inactive (low level in this example) and makes the charger connection signal Sb active (high level in this example).

[0076] The detection circuit 222 generates an overcharge detection signal VD1 and an overcharge return signal VR1 by comparing two divided voltages of the power supply voltage Vdd with a reference voltage VREF1. When the power supply voltage Vdd is higher than a predetermined overcharge detection voltage Vdet1, the detection circuit 222 makes the overcharge detection signal VD1 active (high level in this example) and makes the overcharge return signal VR1 inactive (low level in this example). When the power supply voltage Vdd is lower than the predetermined overcharge return voltage Vrel1, the detection circuit 222 makes the overcharge return signal VR1 active (high level in this example) and makes the overcharge detection signal VD1 inactive (low level in this example).

[0077] The detection circuit 222 generates an overdischarge detection signal VD2 and an overdischarge recovery signal VR2 by comparing two divided voltages of the power supply voltage Vdd with a reference voltage VREF1. When the power supply voltage Vdd is lower than a predetermined overdischarge detection voltage Vdet2, the detection circuit 222 makes the overdischarge detection signal VD2 active (high level in this example) and makes the overdischarge recovery signal VR2 inactive (low level in this example). When the power supply voltage Vdd is higher than the predetermined overdischarge recovery voltage Vrel2, the detection circuit 222 makes the overdischarge recovery signal VR2 active (high level in this example) and makes the overdischarge detection signal VD2 inactive (low level in this example).

[0078] The charge control circuit 221 a includes delay circuits 41 and 42 , AND gates 23 and 24 , and an RS flip-flop 25 .

[0079] When the active overcharge detection signal VD1 continues for the detection delay time tVdet1, the delay circuit 41 switches the level of its output signal from inactive (low level in this example) to active (high level in this example). The AND gate 23 receives the output signal of the delay circuit 41 and the inverted output signal QB1 of the RS flip-flop 25, and outputs the logical AND of them. The output signal of the AND gate 23 is input to the set terminal S1 of the RS flip-flop 25.

[0080] When the active overcharge recovery signal VR1 continues for the recovery delay time tVrel1, the delay circuit 42 switches the level of its output signal from inactive (low level in this example) to active (high level in this example). The AND gate 24 receives the output signal of the delay circuit 42, the output signal Q1 of the RS flip-flop 25, and the load connection signal Sa of the state detection circuit 226, and outputs the logical AND of these. The output signal of the AND gate 24 is input to the reset terminal R1 of the RS flip-flop 25.

[0081] The logic level of the output signal Q1 of the RS flip-flop 25 is inverted by the inverter circuit 21, and the inverted signal is output from the terminal COUT as a gate control signal.

[0082] The discharge control circuit 221b includes delay circuits 43 and 44, AND gates 26 and 27, and an RS flip-flop .

[0083] When the active overdischarge detection signal VD2 continues for the detection delay time tVdet2, the delay circuit 43 switches the level of its output signal from inactive (low level in this example) to active (high level in this example). The output signal of the delay circuit 43 and the inverted output signal QB2 of the RS flip-flop 28 are input to the AND gate 26, which outputs the logical product of these. The output signal of the AND gate 26 is input to the set terminal S2 of the RS flip-flop 28.

[0084] When the active overdischarge recovery signal VR2 continues for the recovery delay time tVrel2, the delay circuit 44 switches the level of its output signal from inactive (low level in this example) to active (high level in this example). The AND gate 27 receives the output signal of the delay circuit 44, the output signal Q2 of the RS flip-flop 28, and the charger connection signal Sb of the state detection circuit 226, and outputs the logical AND of these. The output signal of the AND gate 27 is input to the reset terminal R2 of the RS flip-flop 28.

[0085] The logic level of the output signal Q2 of the RS flip-flop 28 is inverted by the inverter circuit 22, and the inverted signal is output from the terminal DOUT as a gate control signal.

[0086] Output signal Q2 of RS flip-flop 28 is input to voltage generation circuit 227 as voltage control signal B, which controls the voltage generation operation of voltage generation circuit 227, which generates voltage Vb. Voltage generation circuit 227 changes voltage Vb in accordance with voltage control signal B generated by discharge control circuit 221b. In accordance with voltage control signal B in the over-discharge protection state, voltage generation circuit 227 reduces voltage Vb supplied to fuel gauge IC701 to voltage Vr, which puts fuel gauge IC701 into a sleep state. Meanwhile, in accordance with voltage control signal B in a state recovered from the over-discharge protection state (over-discharge protection released state), voltage generation circuit 227 raises voltage Vb supplied to fuel gauge IC701 to a voltage that transitions (returns) from the sleep state to the normal monitoring state.

[0087] 5 is a diagram showing an example of the configuration of a voltage generation circuit provided in the protection circuit according to the first embodiment. The voltage generation circuit 227 generates a voltage Vb from a power supply voltage Vdd supplied from terminals VDD and VSS in accordance with a voltage control signal B. The voltage generation circuit 227 includes a transistor 31, an operational amplifier 32, resistors 33 and 34, and a switch 35. The resistor 33 has a resistance value 2R that is twice the resistance value R of the resistor 34.

[0088] When the voltage control signal B in the over-discharge protection release state is input, the switch 35 is turned on. When the switch 35 is on, the voltage generation circuit 227 operates as a low-saturation linear regulator (LDO: Low Drop Out) that can clamp excessive power supply voltage Vdd. On the other hand, when the voltage control signal B in the over-discharge protection state is input, the switch 35 is turned off. When the switch 35 is off, the voltage generation circuit 227 operates as a voltage follower that outputs a constant voltage Vr from the terminal VOUT.

[0089] The voltage generating circuit 227 has the configuration shown in Fig. 5 and can adjust the voltage Vb as shown in Fig. 6. The vertical axis of Fig. 6 represents voltage, and the horizontal axis represents time. The solid line represents the voltage at terminal P+, the dotted line represents the voltage at terminal B+, and the dashed-dotted line represents voltage Vb.

[0090] 6 is a diagram showing an example of the operation of the voltage generation circuit provided in the protection circuit according to the first embodiment. When the over-discharge protection is released, the voltage generation circuit 227 operates as a low-saturation linear regulator capable of clamping an excessive power supply voltage Vdd to a clamp voltage Vov or less. When the power supply voltage Vdd is equal to or less than the clamp voltage Vov in the over-discharge protection released state, the voltage generation circuit 227 generates a voltage Vb that is substantially equal to the power supply voltage Vdd (slightly smaller by the amount of drop).

[0091] When the power supply voltage Vdd supplied from the secondary battery 210 is higher than the overcharge detection voltage Vdet1, the protection IC 101 detects that the secondary battery 210 is overcharged. For example, if the overcharge detection voltage Vdet1 and the clamp voltage Vov are set equal, the voltage generation circuit 227 maintains the voltage Vb at the clamp voltage Vov when an overcharge is detected. Here, by setting the clamp voltage Vov to a value equal to or lower than the withstand voltage of the fuel gauge IC701, it is possible to prevent an excessive voltage exceeding the withstand voltage of the fuel gauge IC701 from being applied to the fuel gauge IC701, even if the power supply voltage Vdd exceeds the withstand voltage of the fuel gauge IC701 due to overcharge of the secondary battery 210. In this way, the voltage generation circuit 227 maintains the voltage Vb generated from the power supply voltage Vdd at or lower than the clamp voltage Vov when an overcharge of the secondary battery 210 is detected.

[0092] When the over-discharge protection is released and recovery of the secondary battery 210 from overcharging is detected, the voltage generating circuit 227 supplies the fuel gauge IC 701 with a voltage Vb that is approximately equal to the power supply voltage Vdd, which has become lower than the clamp voltage Vov.

[0093] When the power supply voltage Vdd is lower than the over-discharge detection voltage Vdet2 (over-discharge protection state), the protection IC 101 detects that the secondary battery 210 is over-discharged. The over-discharge detection voltage Vdet2 is lower than the clamp voltage Vov and higher than the voltage Vr. In the over-discharge protection state, the voltage generation circuit 227 operates as a voltage follower that supplies a constant voltage Vr to the fuel gauge IC 701.

[0094] 7 is a circuit block diagram showing an example of a system including a protection circuit according to a modification of the first embodiment. The system 501A has a battery device 401A which is a modification of the battery device 401 described above. The battery device 401A includes a battery monitoring device 601A. The battery monitoring device 601A includes a protection IC 101A. The protection IC 101A differs from the protection IC 101 described above in that it includes terminals D and E.

[0095] Terminal A is electrically connected to terminal D. Terminal D is electrically connected to terminal E inside protection IC 101A. Terminal E is electrically connected to terminal I / F. If the electrostatic discharge tolerance of fuel gauge IC 701 is smaller than that of protection IC 101A, terminal A is connected to terminal I / F via protection IC 101A, and terminal A is protected from static electricity by the electrostatic discharge tolerance of protection IC 101A. This allows the number of protective elements, such as diodes, externally attached to terminal A to be reduced.

[0096] 8 is a circuit block diagram showing an example of a system including a protection circuit according to the second embodiment. In the second embodiment, the same configurations, actions, and effects as those of the above-described embodiments will not be described again by citing the above descriptions. The second embodiment differs from the first embodiment in that a switch circuit 203 is provided on the low-side ground line 202.

[0097] The system 502 shown in FIG. 8 includes a battery device 402 and an electronic device 300. The system 502 may also include a charger 302 that charges the battery device 402. The battery device 402 is an example of a power supply system that supplies power to the electronic device 300. The battery device 402 includes a secondary battery 210 and a battery monitoring device 602. The battery monitoring device 602 is an example of a battery monitoring module that monitors the secondary battery 210. The battery monitoring device 602 is a component that includes, for example, a board on which at least the protection IC 102 or the fuel gauge IC 701 is mounted. The protection IC 102 is an example of a protection circuit used to protect a secondary battery. The protection IC 102 includes, for example, a charge control terminal (terminal COUT), a discharge control terminal (terminal DOUT), a power supply terminal (terminal VDD), a ground terminal (terminal VSS), a current detection terminal (terminal CS), a monitoring terminal (terminal VM), and an output terminal (terminal VOUTL). The terminal VM has a function similar to that of the terminal VP in the first embodiment. The protection IC 102 includes a voltage generating circuit 228 , a detecting circuit 222 , and a control circuit 221 .

[0098] The voltage generation circuit 228 generates a voltage VbL to be supplied to the fuel gauge IC 701 from the power supply voltage Vdd applied between the terminals VDD and VSS. The voltage generation circuit 228 has the function of lowering and raising the voltage VbL. The voltage generation circuit 228 includes, for example, a voltage regulator that regulates the power supply voltage Vdd and generates the regulated voltage VbL. The voltage VbL generated by the voltage generation circuit 228 is supplied to the fuel gauge IC 701 via the terminal VOUTL.

[0099] The detection circuit 222 detects a charging overcurrent of the secondary battery 210 by monitoring the potential difference ΔV2 between the terminals CS and VM. The detection circuit 222 compares the potential difference ΔV2 with a predetermined charging overcurrent detection voltage Vdet4, and when the potential difference ΔV2 is lower than the charging overcurrent detection voltage Vdet4 with respect to the terminal CS, the detection circuit 222 generates a charging overcurrent detection signal indicating that a charging overcurrent of the secondary battery 210 has been detected. In other words, the detection circuit 222 generates the charging overcurrent detection signal when the voltage of the terminal VM is lower than the charging overcurrent detection voltage Vdet4 with respect to the terminal CS.

[0100] The detection circuit 222 compares the potential of the terminal VM with a state detection threshold that is higher than the potential of the terminal VSS, and when the potential of the terminal VM is higher than the state detection threshold, generates a load connection signal that indicates a state in which a load such as the electronic device 300 is connected to the terminal P-. This is because when a load such as the electronic device 300 is connected to the terminals P+ and P-, the potential of the terminal VM rises, increasing the potential difference between the terminals VSS and VM.

[0101] The detection circuit 222 detects a discharge overcurrent of the secondary battery 210 by monitoring the potential difference ΔV2 between terminals CS and VM. The detection circuit 222 compares the potential difference ΔV2 with a predetermined discharge overcurrent detection voltage Vdet3, and when the potential difference ΔV2 is higher than the discharge overcurrent detection voltage Vdet3 with respect to terminal CS, the detection circuit 222 generates a discharge overcurrent detection signal indicating that a discharge overcurrent of the secondary battery 210 has been detected. In other words, the detection circuit 222 generates a discharge overcurrent detection signal when the voltage of terminal VM is higher than the discharge overcurrent detection voltage Vdet3 with respect to terminal CS.

[0102] The detection circuit 222 compares the potential of the terminal VM with a state detection threshold that is higher than the potential of the terminal VSS, and when the potential of the terminal VM is lower than the state detection threshold, generates a charger connection signal that indicates a state in which the charger 302 is electrically connected to the terminal P-. This is because when the charger 302 is electrically connected to the terminals P+ and P-, the potential of the terminal VM drops, reducing the potential difference between the terminals VSS and VM.

[0103] When the potential of terminal IN2 is lower than the potential of terminal IN1, fuel gauge IC701 determines that current I is a charging current of secondary battery 210, and when the potential of terminal IN2 is higher than the potential of terminal IN1, it determines that current I is a discharging current of secondary battery 210.

[0104] Resistance element Rsns is provided on ground line 202 between transistors TR1, TR2 and terminal P-. As a result, even if an abnormal current path occurs between terminal IN1 and terminal A or the like due to a malfunction of fuel gauge IC 701, causing an overcurrent to flow, overcurrent protection by protection IC 101 will function, improving the reliability of battery monitoring device 602.

[0105] A fuel gauge IC 701 according to the second embodiment differs from the first embodiment in that a terminal BAT is connected to a power supply line 201 and a terminal GND is connected to a terminal VOUTL.

[0106] The terminal BAT is a power supply terminal of the monitoring IC 701 and is connected to the power supply line 201. The terminal GND is an example of a second terminal that is connected to the terminal VOUTL, which is an example of a first terminal. The terminal GND is a ground terminal of the monitoring IC 701 and is connected to the terminal VOUTL. The fuel gauge IC 701 operates on a power supply voltage (voltage VbL supplied from the protection circuit IC102) that is applied between the terminal BAT and the terminal GND.

[0107] Next, an example of the operation when the protection circuit transitions to an over-discharge protection state and when it returns from the over-discharge protection state will be described.

[0108] Fig. 9 shows an example of the operation of the protection circuit when it transitions to an over-discharge protection state and when it returns from the over-discharge protection state. In Fig. 9, the potential of terminal P+ or terminal VDD is shown as a reference potential of 0, so the voltage waveform is upside down compared to Fig. 2. The vertical axis of Fig. 9 represents voltage, and the horizontal axis represents time. The solid line represents the voltage of terminal B-, the dotted line represents the voltage of terminal P-, and the dashed-dotted line represents voltage VbL.

[0109] 9, when over-discharge of the secondary battery 210 is detected, the protection IC 102 cuts off the supply of voltage VbL to the fuel gauge IC 701, thereby reducing the current consumption of the fuel gauge IC 701. However, if the power supply to memory 702 in the fuel gauge IC 701 is suddenly cut off due to the cutoff of voltage VbL, there is a risk that data d stored in memory 702 will be lost.

[0110] Fig. 10 is a diagram showing an example of the operation of the protection circuit according to the second embodiment to reduce the voltage supplied to the monitoring circuit when the secondary battery is in an over-discharge state. In Fig. 10, the potential of terminal P+ or terminal VDD is shown as a reference potential of 0, so the voltage waveform is upside down compared to Fig. 3. The vertical axis of Fig. 10 represents voltage, and the horizontal axis represents time. The solid line represents the voltage of terminal B-, the dotted line represents the voltage of terminal P-, and the dashed-dotted line represents voltage VbL.

[0111] As shown in FIG. 10 , in a first state (overdischarge state) in which overdischarge of the secondary battery 210 is detected, the protection IC 102 according to the second embodiment reduces the voltage VbL supplied to the fuel gauge IC 701 to a voltage Vr at which the fuel gauge IC 701 enters a sleep state, with the potential of the terminal VDD set to a reference potential of 0. When the fuel gauge IC 701 enters the sleep state, the power consumption of the fuel gauge IC 701 decreases. The voltage Vr is lower than the voltage at which the protection IC 101 detects overdischarge (overdischarge detection voltage Vdet2), with the potential of the terminal VDD set to a reference potential of 0, and higher than the voltage Vreset at which data d stored in the memory 702 is lost. Therefore, when overdischarge of the secondary battery 210 is detected, the protection IC 101 supplies the fuel gauge IC 701 with the voltage Vr at which the fuel gauge IC 701 enters a sleep state, thereby reducing the current consumption of the fuel gauge IC 701 to prevent the loss of data d. This reduces the current consumption in the overdischarge state of the secondary battery 210. By reducing the current consumption in the overdischarge state of the secondary battery 210, the progress of overdischarge of the secondary battery 210 is suppressed, and therefore the progress of deterioration of the secondary battery 210 is also suppressed.

[0112] When voltage VbL drops below voltage Vsleep, fuel gauge IC701 transitions from a normal monitoring state, in which it monitors current I and performs other operations, to a sleep state in which circuit operations such as monitoring current I are stopped, with the potential at terminal VDD set as reference potential 0. When voltage VbL drops below voltage Vreset, which is lower than voltage Vsleep, the circuit operation of fuel gauge IC701 is reset, increasing the risk of data d stored in memory 702 being lost. The voltage Vr at which fuel gauge IC701 enters the sleep state is higher than voltage Vreset and lower than voltage Vsleep, with the potential at terminal VDD set as reference potential 0. The sleep state of fuel gauge IC701 is a state in which circuit operations such as monitoring current I are stopped.

[0113] In the over-discharge protection state, the protection IC 102 transitions from the over-discharge protection state to the normal state when the power supply voltage Vdd rises to or exceeds the over-discharge recovery voltage Vrel2 and an electrical connection between the terminal P- and the charger 302 is detected. In the normal state, the protection IC 102 sets the potential of the terminal VDD as a reference potential 0 and raises the voltage VbL supplied to the fuel gauge IC 701 to a voltage higher than the voltage Vr and the voltage Vsleep (for example, a voltage equal to the voltage Vdd supplied from the secondary battery 210 to the protection IC 102). In the normal state, the protection IC 102 supplies a voltage higher than the voltage Vr and the voltage Vsleep from the terminal VOUTL to the fuel gauge IC 701, thereby transitioning the fuel gauge IC 701 from the sleep state to the normal monitoring state.

[0114] Since voltage VbL is maintained at or above voltage Vreset in the over-discharge protection state, with the potential of terminal VDD set as reference potential 0, data d saved in memory 702 in the sleep state remains the data from the normal state immediately before transition to the over-discharge protection state (the monitoring state immediately before transition to the sleep state). Therefore, when the fuel gauge IC 701 transitions from the sleep state to the normal monitoring state, it can resume measuring the remaining capacity, etc. of the secondary battery 210 using data d that has a history before over-discharge detection. This improves the reliability of the measurement results of remaining capacity, etc. by fuel gauge IC 701.

[0115] In this way, the protection IC 102 can easily transition the fuel gauge IC 701 between the sleep state and the monitoring state by changing the voltage VbL supplied to the fuel gauge IC 701.

[0116] 11 is a diagram showing an example of the configuration of a protection circuit according to the second embodiment. The protection IC 102 has a state detection circuit 226, a detection circuit 222, a control circuit 221, and a voltage generation circuit 228. The state detection circuit 226 may be included in the detection circuit 222. The control circuit 221 has a charge control circuit 221a and a discharge control circuit 221b.

[0117] When the potential of the terminal VM is higher than the state detection threshold (=potential of the terminal VSS+predetermined voltage VREF2), the state detection circuit 226 determines that a load is connected to the terminals P+ and P- and that discharging has started from the secondary battery 210. In this case, the state detection circuit 226 makes the load connection signal Sa active (high level in this example) and makes the charger connection signal Sb inactive (low level in this example).

[0118] When the potential of terminal VM is lower than the state detection threshold (=potential of terminal VSS+predetermined voltage VREF2), the state detection circuit 226 determines that the charger is connected to terminals P+ and P- and that charging has commenced for the secondary battery 210. In this case, the state detection circuit 226 makes the load connection signal Sa inactive (low level in this example) and makes the charger connection signal Sb active (high level in this example).

[0119] The output signal Q2 of the RS flip-flop 28 is input to the voltage generation circuit 228 as a voltage control signal B that controls the voltage generation operation of the voltage generation circuit 228, which generates the voltage VbL. The voltage generation circuit 228 changes the voltage VbL in accordance with the voltage control signal B generated by the discharge control circuit 221b. In accordance with the voltage control signal B in the over-discharge protection state, the voltage generation circuit 228 sets the potential of the terminal VDD to reference potential 0 and reduces the voltage VbL supplied to the fuel gauge IC701 to voltage Vr at which the fuel gauge IC701 enters a sleep state. Meanwhile, in accordance with the voltage control signal B in a state after recovery from the over-discharge protection state (over-discharge protection released state), the voltage generation circuit 228 sets the potential of the terminal VDD to reference potential 0 and increases the voltage Vb supplied to the fuel gauge IC701 to a voltage that transitions (returns) the fuel gauge IC701 from the sleep state to the normal monitoring state.

[0120] FIG. 12 is a diagram showing an example of the configuration of a voltage generation circuit provided in the protection circuit according to the second embodiment. The voltage generation circuit 228 generates a voltage VbL from the power supply voltage Vdd supplied from the terminals VDD and VSS in accordance with a voltage control signal B. The voltage generation circuit 228 includes a transistor 31, an operational amplifier 32, resistors 33 and 34, and a switch 35. The resistor 33 has a resistance value 2R that is twice the resistance value R of the resistor 34. The voltage generation circuit 228 in FIG. 12 has the same functions and effects as the voltage generation circuit 227 in FIG. 5, and therefore the above description is incorporated herein for brevity and will not be repeated. The voltage generation circuit 228, having the configuration shown in FIG. 12, can generate a variable voltage Vb as shown in FIG. 13.

[0121] Fig. 13 is a diagram showing an example of the operation of the voltage generating circuit provided in the protection circuit according to the second embodiment. The voltage generating circuit 228 according to the second embodiment has the same action and effect as the voltage generating circuit 227 according to the first embodiment, and therefore the description of Fig. 13 will be omitted by referencing the above description of Fig. 6.

[0122] Although the embodiments have been described above, they are presented as examples and the present invention is not limited to the above embodiments. The above embodiments can be implemented in various other forms, and various combinations, omissions, substitutions, modifications, etc. can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as set forth in the claims.

[0123] For example, the positions of the charge control transistor TR1 and the discharge control transistor TR2 may be interchanged with each other with respect to the positions shown in the figure. The switch circuit 203 may be built into the protection IC. [Explanation of symbols]

[0124] 41, 42, 43, 44 Delay circuit 101,101A,102 Protection IC 201 Power line 202 Ground wire 203 Switch Circuit 210 Secondary battery 211 Positive electrode 212 Negative electrode 221 Control circuit 221a Charging control circuit 221b Discharge control circuit 222 detection circuit 226 Status detection circuit 227,228 Voltage generation circuit 300 Electronic equipment 302 charger 303 PMIC 304 Internal circuit 305 Connector 401, 401A, 402 Battery Device 501, 501A, 502 systems 601,601A,602 Battery monitoring device 701 Fuel Gauge IC 702 memory TR1 Charge control transistor TR2 discharge control transistor

Claims

1. a protection circuit for detecting over-discharge of the secondary battery; a monitoring circuit that operates using a voltage supplied from the protection circuit and monitors a current flowing through the secondary battery, The protection circuit supplies a first voltage to the monitoring circuit, causing the monitoring circuit to enter a sleep state, in a first state in which the over-discharge is detected.

2. 2. The battery monitoring module of claim 1, wherein the protection circuit includes a circuit for detecting overcharging of the secondary battery, and in a second state in which overcharging is detected, supplies a second voltage to the monitoring circuit that is lower than the withstand voltage of the monitoring circuit.

3. the monitoring circuit includes a memory for storing data obtained by monitoring the current; The battery monitoring module according to claim 1 , wherein the first voltage is lower than a voltage at which the protection circuit detects the over-discharge and higher than a voltage at which the data stored in the memory is lost.

4. The battery monitoring module according to claim 3 , wherein the sleep state is a state in which the monitoring circuit stops operating.

5. The battery monitoring module according to claim 1 , wherein the protection circuit supplies a third voltage higher than the first voltage to the monitoring circuit when recovery from the over-discharge is detected.

6. The battery monitoring module according to claim 5 , wherein the third voltage is equal to the voltage supplied from the secondary battery.

7. The battery monitoring module according to claim 2 , wherein the protection circuit includes a voltage generating circuit that generates the second voltage from a voltage supplied from the secondary battery in the second state.

8. 3. The battery monitoring module according to claim 2, wherein the protection circuit supplies a fourth voltage lower than the second voltage to the monitoring circuit when recovery from the overcharge is detected.

9. The battery monitoring module according to claim 8 , wherein the fourth voltage is equal to the voltage supplied from the secondary battery.

10. the protection circuit includes a voltage generating circuit that generates a voltage to be supplied to the monitoring circuit, and a first terminal that outputs the voltage to be supplied to the monitoring circuit; The battery monitoring module of claim 1 , wherein the monitoring circuit has a second terminal connected to the first terminal.

11. 3. The battery monitoring module of claim 2, wherein the protection circuit detects that the secondary battery is over-discharged when the voltage of the secondary battery is lower than the second voltage and lower than a voltage higher than the first voltage, and detects that the secondary battery is over-charged when the voltage of the secondary battery is higher than a voltage higher than the second voltage.

12. a transistor that is turned on or off by the protection circuit to control the current; a first positive terminal and a first negative terminal for connecting a load; a second positive terminal and a second negative terminal for connecting the secondary battery; a resistor for detecting a current in the monitoring circuit, 12. The battery monitoring module according to claim 1, wherein, when the current path in which the transistor is provided is a first current path connecting the first positive terminal and the second positive terminal, the resistor is provided in the first current path between the transistor and the first positive terminal, and when the current path in which the transistor is provided is a second current path connecting the first negative terminal and the second negative terminal, the resistor is provided in the second current path between the transistor and the first negative terminal.

13. A secondary battery; a protection circuit for detecting over-discharge of the secondary battery; a monitoring circuit that operates using a voltage supplied from the protection circuit and monitors a current flowing through the secondary battery, In a first state in which the over-discharge is detected, the protection circuit supplies a first voltage to the monitoring circuit, causing the monitoring circuit to enter a sleep state.

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