Integrated circuit, battery monitoring device and battery monitoring system

Abstract

A battery monitoring device (100) includes: a pair of terminals connected to a filter unit including a capacitor element for measuring a voltage or current of a battery (B); an AD converter for measuring a waveform of a voltage between the terminals when the capacitor element is charged or discharged; and a time constant calculation unit (117) for calculating a time constant of the filter unit based on the measured waveform. The AD converter is, for example, a first AD converter (109) or a second AD converter (112). The filter unit is, for example, a first filter unit (103) or a second filter unit (104).

Description

Technical Field

[0001] The present invention relates to a battery monitoring device for monitoring the state of a battery. Background Art

[0002] The development of vehicles such as HEV (Hybrid Electric Vehicle) and EV (Electric Vehicle) that use secondary batteries as power sources is underway. In addition, it is known that a battery management system (BMS) is used to estimate the remaining battery level and detect abnormalities in order to safely use secondary batteries. As such a BMS, a battery monitoring device capable of monitoring the status of a battery in real time is disclosed in Patent Document 1.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent No. 5403437 Summary of the invention

[0006] The present invention provides an integrated circuit capable of calculating a time constant of a filter unit connected to a terminal for measuring a voltage or current of a battery. In addition, the present invention provides a battery monitoring device and a battery monitoring system including such an integrated circuit.

[0007] An integrated circuit of one embodiment of the present invention comprises: a pair of terminals connected to a filter unit including a capacitor element for measuring a voltage or current of a battery; an AD (Analog to Digital) converter for measuring a waveform of a voltage between the terminals when the capacitor element is charged or discharged; and a time constant calculation unit for calculating a time constant of the filter unit based on the measured waveform.

[0008] A battery monitoring device according to one embodiment of the present invention includes the above-mentioned integrated circuit and the above-mentioned filter unit.

[0009] A battery monitoring system according to one embodiment of the present invention includes the above-mentioned battery monitoring device and the above-mentioned battery.

[0010] According to one embodiment of the present invention, an integrated circuit capable of calculating a time constant of a filter connected to a terminal for measuring a voltage or current of a battery is realized. In addition, according to one embodiment of the present invention, a battery monitoring device and a battery monitoring system including such an integrated circuit are realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1This is a block diagram showing the functional configuration of the battery monitoring system according to the first embodiment.

[0012] Figure 2 This is a flowchart of the operation of calculating the time constant of the first filter unit.

[0013] Figure 3 This is a diagram showing a voltage waveform for explaining a method of calculating the time constant of the first filter unit.

[0014] Figure 4 This is a flowchart of the operation of calculating the time constant of the second filter unit.

[0015] Figure 5 This is a diagram showing a voltage waveform for explaining a method of calculating the time constant of the second filter unit.

[0016] Figure 6 This is a block diagram showing the functional configuration of a battery monitoring system in which the arrangement of resistors is changed. DETAILED DESCRIPTION

[0017] Hereinafter, the embodiments will be described with reference to the accompanying drawings. In addition, the embodiments described below all represent general or specific examples. The numerical values, shapes, materials, components, configuration positions of components, connection forms, steps, and the order of steps shown in the following embodiments are used as examples and are not intended to limit the present invention. In addition, among the components of the following embodiments, components not described in the independent claims are described as arbitrary components.

[0018] In addition, each figure is a schematic diagram and does not necessarily illustrate strictly. In addition, in each figure, the same reference numeral is attached to the substantially same structure, and there is a case where the repeated description is omitted or simplified.

[0019] (Implementation Method 1)

[0020] [structure]

[0021] First, the configuration of the battery monitoring system according to the first embodiment will be described. Figure 1 This is a block diagram showing the functional configuration of the battery monitoring system according to the first embodiment.

[0022] Figure 1The battery monitoring system 200 shown includes a battery monitoring device 100 and a battery pack 101. The battery monitoring device 100 is a device that monitors the state of the battery pack 101. The battery pack 101 includes a plurality of batteries B. In other words, the battery B is a battery cell. Specifically, the battery B is a lithium-ion battery, but it may also be another battery such as a nickel-metal hydride battery. The battery pack 101 functions as a power source for a load 102 and supplies power to the load 102. The load 102 is, for example, a motor of an EV, but is not particularly limited. In addition, there is also a case where a charging device for charging the battery pack 101 is connected to the position of the load 102 instead of the load 102.

[0023] Specifically, the battery monitoring device 100 can calculate and monitor the AC impedance of the battery B. The AC impedance of the battery B is used, for example, to calculate the degree of deterioration of the battery B. The degree of deterioration of the battery B is represented by a parameter called SOH (State of Health), for example.

[0024] The battery monitoring device 100 includes a plurality of first filter units 103, a second filter unit 104, an integrated circuit 105, a resistor 106, and a switch 107. The integrated circuit 105 includes a plurality of first terminals 108, a plurality of first AD (Analog to Digital) converters 109, a second terminal 110, a power supply 111, a second AD converter 112, an AC impedance calculation unit 113, a plurality of first switches 115, a control unit 116, a time constant calculation unit 117, and a second switch 118.

[0025] The first terminals 108 are a pair of terminals for measuring the voltage of the battery B. The plurality of first terminals 108 (more specifically, a plurality of first terminal groups) correspond one-to-one to the plurality of batteries B. One battery B is connected between one first terminal 108 via the first filter unit 103 .

[0026] The plurality of first AD converters 109 are measuring units for measuring the voltages of the plurality of batteries B. The plurality of first AD converters 109 correspond one-to-one to the plurality of batteries B. One first AD converter 109 converts the voltage across one battery B (i.e., an analog signal) into a digital signal. The first AD converter 109 is, for example, a ΔΣ type AD converter.

[0027] In the integrated circuit 105, the plurality of first AD converters 109 have the same AD conversion characteristics. The so-called AD conversion characteristics are various parameters such as resolution (number of bits). Specifically, the same AD converter is used as a product for the plurality of first AD converters 109. Thus, the measurement error of the voltage of the plurality of batteries B caused by AD conversion can be reduced.

[0028] The second terminals 110 are a pair of terminals for measuring the current of the battery B. A resistor 106 is connected between the second terminals 110 via the second filter unit 104 .

[0029] The resistor 106 is a resistor disposed on a path P2 different from the path P1 of the current flowing from the battery pack 101 to the load 102. That is, the resistor 106 is a resistor that does not allow the current flowing to the load 102 to flow. The resistor 106 is connected in series to the battery pack 101. The resistor 106 is, for example, a discrete component provided outside the integrated circuit 105.

[0030] The switch 107 is a switch for passing current from the battery pack 101 to the resistor 106. The switch 107 is, for example, a FET (Field Effect Transistor), but may also be a bipolar transistor. The switch 107 is turned on and off by, for example, the control unit 116 of the integrated circuit 105.

[0031] Thus, if resistor 106 is disposed on path P2, current can flow from battery pack 101 to resistor 106 by turning on switch 107 regardless of whether battery pack 101 is being charged or discharged. That is, the current of battery B can be measured regardless of whether battery pack 101 is being charged or discharged.

[0032] The second AD converter 112 is a measuring unit that measures the current flowing through the resistor 106. Specifically, the second AD converter 112 converts the voltage (i.e., analog signal) at both ends of the resistor 106 into a digital signal. The second AD converter 112 is, for example, a ΔΣ type AD converter. For the second AD converter 112, for example, an AD converter having the same AD conversion characteristics as the plurality of first AD converters 109 (i.e., the same as the product) is used. Thus, the measurement error caused by AD conversion generated between the plurality of first AD converters 109 and the second AD converter 112 can be reduced.

[0033] The AC impedance calculation unit 113 calculates the AC impedance of the plurality of batteries B based on the voltages of the plurality of batteries B measured by the plurality of first AD converters 109 and the current of the battery pack 101 (i.e., the current of the battery B) measured by the second AD converter 112. Specifically, the AC impedance calculation unit 113 converts the voltages of the plurality of batteries B into complex voltages, converts the currents of the batteries B into complex currents, and calculates the AC impedance of each of the plurality of batteries B by dividing the complex voltage by the complex current.

[0034] [Calculation of the time constant of the first filter unit]

[0035] In addition, in order to remove noise when measuring the voltage of the battery B, the first filter unit 103 is connected to each of the plurality of first terminals 108. Specifically, the first filter unit 103 is a low-pass filter. The first filter unit 103 is a filter circuit composed of a resistor 103r1, a resistor 103r2, and a capacitor 103c. The capacitor 103c included in the first filter unit 103 requires a large capacitance, so it is difficult to build the first filter unit 103 into the integrated circuit 105. Therefore, the first filter unit 103 is composed of discrete components and is externally mounted on the integrated circuit 105.

[0036] When the first filter unit 103 is formed of discrete components, there may be a large error in the design value of the time constant of the first filter unit 103. If the time constant can be calculated, the calculation accuracy of the AC impedance can be improved by correcting the AC impedance according to the time constant.

[0037] Therefore, the integrated circuit 105 has a function of calculating the time constant of the first filter unit 103. The integrated circuit 105 includes a plurality of first switches 115, a control unit 116, and a time constant calculation unit 117 as components for calculating the time constant of the first filter unit 103.

[0038] The first switch 115 is provided at each of the plurality of first terminals 108, and switches between short circuit and open circuit between the first terminals 108. The first switch 115 is, for example, a FET, but may also be other switch elements such as a bipolar transistor.

[0039] The control unit 116 discharges the capacitor 103c included in the first filter unit 103. The control unit 116 outputs a control signal to turn on the first switch 115, thereby short-circuiting the first terminals 108 and discharging the capacitor 103c. The control unit 116 is implemented by, for example, a microcomputer or a processor.

[0040] The time constant calculation unit 117 calculates the time constant of the first filter unit 103 based on the waveform of the voltage between the first terminals 108 (i.e., the waveform of the voltage across the capacitor 103c) when the capacitor 103c is charged by the battery B just after being discharged. The time constant calculation unit 117 is implemented by, for example, a microcomputer or a processor.

[0041] The following describes the calculation operation of the time constant using such components. Figure 2 4 is a flowchart of the operation of calculating the time constant of the first filter unit 103 . Figure 3 1 is a diagram showing a voltage waveform for explaining a method of calculating the time constant of the first filter unit 103 .

[0042] like Figure 3 As shown in FIG. 1 , normally, the voltage V of the battery B is applied to the capacitor element 103c. In this state, the control unit 116 discharges the capacitor element 103c by turning on the first switch 115 (S11). Specifically, the control unit 116 Figure 3 The first switch 115 is turned on at timing t4, and the first switch 115 is kept on during a period T0 (discharging period) until timing t0.

[0043] Next, the control unit 116 turns off the first switch 115 at timing t0 (S12). Thus, the battery B starts charging the capacitor 103c. The first AD converter 109 measures the waveform of the voltage between the first terminals 108 when the capacitor 103c is charged (S13). That is, the first AD converter 109 measures the waveform of the voltage across the two ends of the capacitor 103c when the capacitor 103c is charged.

[0044] The voltage across the capacitor 103c reaches the voltage V after a period corresponding to the time constant of the first filter unit 103 has passed. Therefore, the time constant calculation unit 117 calculates the time constant of the first filter unit 103 based on the waveform measured by the first AD converter 109 (S14). The specific calculation method of the time constant is not particularly limited, and an example is described below.

[0045] The time constant calculation unit 117 calculates the time constant of the first filter unit 103 based on, for example, the integral value DINT1 of the first interval T1 of the measured waveform and the integral value DINT2 of the second interval T2 of the measured waveform that is different from the first interval T1. The first interval T1 is an interval from timing t1 to timing t2, and the second interval T2 is an interval from timing t2 to timing t3. That is, the first interval T1 and the second interval T2 are continuous intervals. The length of the first interval T1 and the length of the second interval T2 are not particularly limited.

[0046] The waveform x of the voltage across the capacitor 103 c when the capacitor 103 c is charged is expressed by the following equation 1 using a time constant τ, and the integrated value of the waveform x is expressed by the following equation 2.

[0047]

Number 1

[0048]

[0049]

[0050] The length of the first interval T1 and the length of the second interval T2 are respectively set to Ts, and the integrated value DINT1 is divided by the integrated value DINT2 to obtain the following equation 3. By transforming equation 3, the time constant τ is obtained as in equation 4 below.

[0051]

Number 2

[0052]

[0053]

[0054] In this way, the time constant calculation unit 117 can calculate the time constant of the first filter unit 103 based on the waveform measured by the first AD converter 109 .

[0055] [Calculation of the time constant of the second filter unit]

[0056] In addition, in order to remove noise when measuring the current of battery B, the second filter unit 104 is connected to the second terminal 110. The second filter unit 104 is specifically a low-pass filter. The second filter unit 104 is a filter circuit composed of a resistor 104r1, a resistor 104r2, and a capacitor 104c. The capacitor 104c included in the second filter unit 104 requires a large capacitance, so it is difficult to build the second filter unit 104 into the integrated circuit 105. Therefore, the second filter unit 104 is composed of discrete components and is externally mounted on the integrated circuit 105.

[0057] When the second filter unit 104 is formed of discrete components, there may be a large error in the design value of the time constant of the second filter unit 104. If the time constant can be calculated, the calculation accuracy of the AC impedance can be improved by correcting the AC impedance according to the time constant.

[0058] Therefore, the integrated circuit 105 has a function of calculating the time constant of the second filter unit 104. The integrated circuit 105 includes a second switch 118 as a component for calculating the time constant of the second filter unit 104 in addition to the control unit 116 and the time constant calculation unit 117 described above.

[0059] The second switch 118 is provided between the power supply 111 and the second terminal 110 to switch the electrical connection between the power supply 111 and the capacitor 104c. The second switch 118 is, for example, a FET, but may also be a bipolar transistor. Figure 1 In the figure, the power source 111 is illustrated as a current source, but it can also be a voltage source.

[0060] The following describes the calculation operation of the time constant using such components. Figure 4 4 is a flowchart of the operation of calculating the time constant of the second filter unit 104 . Figure 5 1 is a diagram showing a voltage waveform for explaining a method of calculating the time constant of the second filter unit 104 .

[0061] like Figure 5 As shown in FIG. 1 , when the switch 107 is turned off, the voltage of the battery pack 101 is not applied to the capacitor element 104c. That is, the capacitor element 104c is not charged. In this state, the control unit 116 charges the capacitor element 104c by turning on the second switch 118 (S21). Specifically, the control unit 116 Figure 5 The second switch 118 is turned on at timing t4, and the second switch 118 is kept on during a period T0 (charging period) from timing t0 to timing t0.

[0062] Next, the control unit 116 turns off the second switch 118 at timing t0 (S22). Thus, the discharge of the capacitor 104c begins. The second AD converter 112 measures the waveform of the voltage between the second terminals 110 when the capacitor 104c is discharged (S23). That is, the second AD converter 112 measures the waveform of the voltage at both ends of the capacitor 104c when the capacitor 104c is discharged.

[0063] The voltage across the capacitor 104c reaches a voltage in a discharged state after a period of time corresponding to the time constant of the first filter unit 103 has passed. Therefore, the time constant calculation unit 117 calculates the time constant of the second filter unit 104 based on the waveform measured by the second AD converter 112 (S24). The specific calculation method of the time constant can use the calculation method described using the above-mentioned equations 1 to 4, for example.

[0064] In this way, the time constant calculation unit 117 can calculate the time constant of the second filter unit 104 based on the waveform measured by the second AD converter 112 .

[0065] Furthermore, the second AD converter 112 measures the voltage across the resistor 106 disposed on the path P2 , but the resistor 106 may be disposed on the path P1 of the current flowing from the battery pack 101 to the load 102 . Figure 6 1 is a block diagram showing the functional configuration of a battery monitoring system 200 in which the arrangement of the resistor 106 is changed. Figure 6 In the example of , the switch 107 is also arranged on the path P1. Figure 6 In the example of FIG. 1 , the resistor 106 and the switch 107 are provided as components other than the components of the battery monitoring device 100 , but they may also be components of the battery monitoring device 100 .

[0066] [Correction of AC impedance]

[0067] The AC impedance calculation unit 113 can correct the AC impedance using the time constant of the first filter unit 103 and the time constant of the second filter unit 104. The following describes a method of correcting the AC impedance.

[0068] Assuming that the resistance values ​​of the resistor 103r1 and the resistor 103r2 are R, and the capacitance value of the capacitor 103c is C, the impedance of the first filter unit 103 is expressed by the following equation 5.

[0069]

[0070] Here, assuming that the angular velocity is ω, the frequency is f, and the time constant is τ, the gain G and the phase θ when passing through the first filter unit 103 are expressed by the following equations 6 and 7.

[0071]

[0072] θ=tan -1 (2πfτ) ··Formula 7

[0073] The correction gain Gcomp for correcting such a gain G is expressed by the following equation 8, and the correction phase θcomp for correcting the phase θ is expressed by the following equation 9.

[0074]

[0075] θ comp =-θ = -tan -1 (2πfτ) ··Formula 9

[0076] The AC impedance calculation unit 113 can correct the voltage measured by the first AD converter 109 using the voltage correction gain GVcomp and the correction phase θVcomp. If the voltage V measured by the first AD converter 109 is expressed by the following equation 10, the corrected voltage V is expressed by the following equation 11.

[0077] V=V meas exp(jθ Vmeas ) ··Formula 10

[0078] V=G Vcomp V meas exp(j(θ Vmeas +θ Vcomp )) ··Formula 11

[0079] Similarly, the AC impedance calculation unit 113 can correct the current measured by the second AD converter 112 using the correction gain GIcomp and the correction phase θIcomp for the current. If the current I measured by the second AD converter 112 is expressed by the following equation 12, the corrected current I is expressed by the following equation 13. That is, the corrected AC impedance Z is expressed by the following equation 14.

[0080] I=I meas exp(jθ Imeas ) ··Formula 12

[0081] I=G Icomp I meas exp(j(θ Imeas +θ Icomp )) ··Formula 13

[0082]

[0083] [Effects, etc.]

[0084] As described above, the integrated circuit 105 includes: a pair of terminals connected to a filter unit including a capacitor element for measuring the voltage or current of the battery B; a control unit 116 for charging or discharging the capacitor element connected between the terminals; an AD converter for measuring the waveform of the voltage between the terminals when the capacitor element is charged or discharged; and a time constant calculation unit 117 for calculating the time constant of the filter unit based on the measured waveform. The AD converter is, for example, the first AD converter 109 or the second AD converter 112. The filter unit is, for example, the first filter unit 103 or the second filter unit 104.

[0085] Such an integrated circuit 105 can calculate the time constant of the filter unit connected to the terminal for measuring the voltage or current of the battery B. If the AC impedance is corrected according to the calculated time constant, the calculation accuracy of the AC impedance can be improved.

[0086] For example, the first terminal 108 is a terminal for measuring the voltage of the battery B, and is electrically connected to both ends of the battery B via the first filter unit 103. The integrated circuit 105 further includes a first switch 115 for switching between the short circuit and the open circuit between the first terminals 108. The control unit 116 short-circuits the first terminals 108 by turning on the first switch 115 and discharges the capacitor element 103c, and then charges the capacitor element 103c by turning off the first switch 115. The first AD converter 109 measures the waveform of the voltage between the first terminals 108 when the capacitor element 103c is charged.

[0087] Such an integrated circuit 105 can calculate the time constant of the first filter unit 103 by measuring the waveform of the capacitor 103 c during charging.

[0088] In addition, for example, the second terminal 110 is a terminal for measuring the current of the battery B, and is electrically connected to both ends of the resistor 106 connected in series with the battery B via the second filter unit 104. The integrated circuit 105 further includes a power supply 111 and a second switch 118 for switching the electrical connection between the power supply 111 and the capacitor 104c. The control unit 116 electrically connects the power supply 111 and the capacitor 104c by turning on the second switch 118 and charges the capacitor 104c, and then discharges the capacitor 104c by turning off the second switch 118. The second AD converter 112 measures the waveform of the voltage between the second terminals 110 when the capacitor 104c is discharged.

[0089] Such an integrated circuit 105 can calculate the time constant of the second filter unit 104 by measuring the waveform of the capacitor 104 c during discharge.

[0090] Furthermore, for example, the time constant calculation unit 117 calculates the time constant of the filter unit based on the measured integrated value DINT1 of the first section T1 of the waveform and the measured integrated value DINT2 of the second section T2 of the waveform different from the first section T1 .

[0091] Such an integrated circuit 105 can calculate the time constant of the filter unit based on the integrated value DINT1 of the first interval T1 and the integrated value DINT2 of the second interval T2.

[0092] Furthermore, for example, the integrated circuit 105 further includes an AC impedance calculation unit 113 that calculates the AC impedance of the battery B using the voltage and current of the battery B and the calculated time constant of the filter unit.

[0093] Such an integrated circuit 105 can calculate the AC impedance with high accuracy by utilizing the time constant of the filter unit.

[0094] In addition, the battery B is one of the plurality of batteries B included in the battery pack 101 .

[0095] Such an integrated circuit 105 can calculate the time constant of the filter unit connected to the terminal for measuring the voltage or current of the battery B included in the battery pack 101.

[0096] Furthermore, the battery monitoring device 100 includes an integrated circuit 105 and a filter unit.

[0097] Such a battery monitoring device 100 can calculate the time constant of the filter unit.

[0098] Furthermore, the battery monitoring system 200 includes the battery monitoring device 100 and a battery B.

[0099] Such a battery monitoring system 200 can calculate the time constant of the filter unit.

[0100] (Other embodiments)

[0101] As mentioned above, although embodiment was described, this invention is not limited to the said embodiment.

[0102] For example, in the above-mentioned embodiment, the battery monitoring device is described as monitoring a battery used in a car such as an EV, but the battery monitoring device may monitor batteries of any application.

[0103] In addition, in the above-mentioned embodiment, the battery monitoring system includes a battery pack, but it is sufficient to include at least one battery. In other words, the battery monitoring device and the integrated circuit only need to monitor at least one battery.

[0104] In addition, the circuit structure described in the above embodiment is an example, and the present invention is not limited to the above circuit structure. That is, a circuit that can achieve the characteristic function of the present invention in the same way as the above circuit structure is also included in the present invention. For example, within the scope of being able to achieve the same function as the above circuit structure, a structure in which a switching element (transistor), a resistor element, a capacitor element, etc. are connected in series or in parallel to a certain element is also included in the present invention.

[0105] In addition, in the above-mentioned embodiments, the components included in the integrated circuit are implemented by hardware. However, a part of the components included in the integrated circuit can also be implemented by executing a software program suitable for the component. A part of the components included in the integrated circuit can also be implemented by a program execution unit such as a CPU (Central Processing Unit) or a processor reading and executing a software program recorded in a recording medium such as a hard disk or a semiconductor memory.

[0106] Furthermore, in the above-mentioned embodiments, the processing performed by a specific processing unit may be performed by another processing unit. Furthermore, in the operations described in the above-mentioned embodiments, the order of a plurality of processing may be changed, and a plurality of processing may be performed in parallel.

[0107] In addition, various modifications that can be conceived by those skilled in the art to the embodiments, or embodiments achieved by arbitrarily combining components and functions in the embodiments without departing from the gist of the present invention are also included in the present invention.

[0108] Marking Description

[0109] 100 Battery Monitoring Device

[0110] 101 Battery Pack

[0111] 102 Load

[0112] 103 First filter section

[0113] 103c, 104c capacitor element

[0114] 103r1, 103r2, 104r1, 104r2, 106 resistors

[0115] 104 Second filter unit

[0116] 105 Integrated Circuits

[0117] 107 Switch

[0118] 108 First terminal

[0119] 109 First AD Converter

[0120] 110 Second terminal

[0121] 111 Power

[0122] 112 Second AD converter

[0123] 113 AC impedance calculation unit

[0124] 115 First switch

[0125] 116 Control Department

[0126] 117 Time constant calculation unit

[0127] 118 Second switch

[0128] 200 Battery Monitoring System

[0129] B Battery

Claims

1. An integrated circuit, characterized in that: have: A pair of terminals connected to a filter unit including a capacitor and a resistor for measuring a voltage or current of a battery; The AD converter is an analog-to-digital converter, which measures the waveform of the voltage between the terminals when the capacitor is charged or discharged. a time constant calculation unit that calculates a time constant of the filter unit based on the measured waveform; and A switch for charging and discharging the capacitor element. The switch is connected to a terminal connected to the resistance element.

2. The integrated circuit according to claim 1, wherein: The terminals are electrically connected to both ends of the battery via the filter unit and are terminals for measuring the voltage of the battery.

3. The integrated circuit according to claim 2, characterized in that A control unit for charging or discharging the capacitor element connected between the terminals is provided, The control unit discharges the capacitor element by turning on the switch to short-circuit between the terminals, and then charges the capacitor element by turning off the switch.

4. The integrated circuit according to claim 2 or 3, characterized in that The AD converter measures a waveform of a voltage between the terminals when the capacitive element is charged.

5. The integrated circuit according to claim 1, wherein: The terminals are electrically connected to both ends of a resistor connected in series to the battery via the filter unit and are terminals for measuring a current of the battery.

6. The integrated circuit according to claim 5, characterized in that A control unit for charging or discharging the capacitor element connected between the terminals is provided, The control unit turns on the switch to electrically connect a power source and the capacitor element to charge the capacitor element, and then turns off the switch to discharge the capacitor element.

7. The integrated circuit according to claim 5 or 6, characterized in that The AD converter measures a waveform of a voltage between the terminals when the capacitive element is discharged.

8. The integrated circuit according to claim 1, wherein: The time constant calculation unit calculates the time constant of the filter unit based on a measured integrated value of a first section of the waveform and a measured integrated value of a second section of the waveform different from the first section.

9. The integrated circuit according to claim 1, wherein: The method further includes an AC impedance calculation unit for calculating the AC impedance of the battery using the voltage and current of the battery and the calculated time constant of the filter unit.

10. The integrated circuit according to claim 1, wherein: The above-mentioned battery is one of a plurality of batteries included in a battery pack.

11. A battery monitoring device, characterized in that: have: The integrated circuit according to any one of claims 1 to 10; and The filter section described above.

12. A battery monitoring system, characterized in that: have: The battery monitoring device according to claim 11; and The above battery.

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