Battery impedance measuring device

Abstract

A battery impedance measuring device 1 measures the AC impedance of a battery pack 3. FETs 5 and 6 are arranged in a path through which an excitation current flows from the battery pack 3, and a shunt resistor 7 is energized with the excitation current through the FETs 5 and 6. An excitation current control unit 13 and a diagnosis control unit 14 control the turning on and off of the FETs 5 and 6, respectively, and a current detection circuit 15 measures the voltage of the shunt resistor 7. An error determination circuit 16 diagnoses the conduction state of the FETs 5 and 6, on the basis of the on / off state of the FETs 5 and 6 controlled by the control units 13 and 14 and the result of energization of the shunt resistor 7.

Description

Battery Impedance Measuring Device CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on Japanese Application No. 2024-71524, filed on April 25, 2024, the contents of which are incorporated herein by reference.

[0002] The present disclosure relates to a device for measuring AC impedance of a battery pack.

[0003] For example, Patent Document 1 discloses a device that measures the AC impedance of a battery pack by controlling a transistor to pass current from a battery to a resistor on a path separate from the current flowing from the battery to a load, and then measures the AC impedance of the battery pack based on the measurement results and the measurement results of the voltage of each unit battery.

[0004] International Publication No. 2020 / 003841

[0005] However, with the configuration of Patent Document 1, if the transistor for passing current from the battery fails and is stuck in the OFF position, it becomes impossible to measure the current and therefore the impedance.

[0006] The present disclosure has been made in consideration of the above circumstances, and its purpose is to provide a battery impedance measuring device that can detect a failure in a current measurement switch element.

[0007] According to the battery impedance measuring device of claim 1, the AC impedance of an assembled battery formed by connecting a plurality of unit cells in series is measured. A switch element is disposed in a path through which an excitation current flows from the assembled battery, and the excitation current flows through the switch element to the resistor element. A control unit controls the on / off of the switch element, and a measurement unit measures the voltage of the resistor element. A diagnosis unit diagnoses the conduction state of the switch element based on the on / off state of the switch element determined by the control unit and the result of current flow through the resistor element.

[0008] Since the switch element and the resistor element are arranged in the path through which the excitation current flows, the result of current flow through the resistor element is determined according to the on / off state of the switch element. Therefore, by comparing the two, the diagnostic unit can diagnose whether the conduction state of the switch element is normal or abnormal.

[0009] According to a battery impedance measuring device of claim 2, two or more switch elements are arranged in the path as the switch elements. When the diagnosing unit diagnoses that one or more of the switch elements are stuck on, the control unit turns off the other normal switch elements. In this way, even if one or more of the switch elements are stuck on, the other normal switch elements can interrupt the current.

[0010] The above and other objects, features and advantages of the present disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. 1 is a diagram showing the configuration of a battery impedance measuring device in a first embodiment, FIG. 2 is a flowchart when an excitation current is generated, FIG. 3 is a flowchart when a diagnosis is performed, FIG. 4 is a diagram showing four phases consisting of combinations of the on / off states of two FETs, FIG. 5 is a diagram showing the configuration of a battery impedance measuring device in a second embodiment, FIG. 6 is a diagram showing the configuration of a battery impedance measuring device and a battery management system in a third embodiment, FIG. 7 is a flowchart showing the processing between the battery impedance measuring device and the battery management system, FIG. 8 is a diagram showing the configuration of a battery impedance measuring device and a battery management system in a fourth embodiment, FIG. 9 is a diagram showing the configuration of a battery impedance measuring device in a fifth embodiment, FIG. 10 is a diagram showing the potentials of each node and the differential voltage between nodes when the FET conduction state is normal, corresponding to states 1 to 4 depending on the on / off combinations of two FETs, FIG. 11 is a flowchart when a diagnosis is performed, FIG. 12 is a diagram showing the configuration of a battery impedance measuring device in a sixth embodiment, and FIG. 13 is a flowchart when an excitation current is generated.

[0011] 1, a battery impedance measuring device 1 of this embodiment measures the AC impedance of an assembled battery 3 formed by connecting a plurality of unit cells 2 in series. A resistive load 4, two N-channel MOSFETs 5 and 6 constituting the battery impedance measuring device 1, and a series circuit of a shunt resistor 7 are connected in parallel to the assembled battery 3. An IC 11 is mounted on a circuit board 10 of the battery impedance measuring device 1. Functional blocks such as a cell voltage detection and equalization unit 12, an excitation current control unit 13, a diagnosis control unit 14, a current detection circuit 15, and an error determination circuit 16 are configured in the IC 11 by hardware, microcomputer software, etc.

[0012] The cell voltage detection and equalization unit 12 detects the voltage of each unit cell 2 and performs a process to equalize these voltages. The excitation current control unit 13 outputs a PWM (Pulse Width Modulation) signal or a PDM (Pulse Density Modulation) signal as a signal to drive the gate of the FET 5. The diagnosis control unit 14 outputs a signal to drive the gate of the FET 6. When an excitation current is applied to measure the AC impedance of the battery pack 3, the FET 6 is kept in a continuous on state and the FET 5 is driven by the PWM signal or the PDM signal. As will be described later, the FET 6 is also used when performing mutual diagnosis including the FET 5. The FETs 5 and 6 correspond to switch elements.

[0013] Shunt resistor 7, which corresponds to the resistive element, is a resistive element for measuring the excitation current, and its terminal voltage is detected by current detection circuit 15. Current detection circuit 15, which corresponds to the measurement unit, is composed of, for example, an A / D conversion circuit and a comparator. The impedance of battery pack 3 is at most 0.1 mΩ to 1 mΩ, while the resistance value of shunt resistor 7 is approximately 10 mΩ. Error determination circuit 16, which corresponds to the diagnosis unit, diagnoses the continuity state of FETs 5 and 6 based on the signals input from excitation current control unit 13, diagnosis control unit 14, and current detection circuit 15.

[0014] Next, the operation of this embodiment will be described. In Figures 2 to 4, (1) and (2) are circled numbers, with SW(1) representing FET5 and SW(2) representing FET6. As shown in Figure 2, the diagnosis control unit 14 keeps FET6 on when generating an excitation current. The excitation current control unit 13 then turns on FET5 (P1). The current detection circuit 15 then determines whether it has detected a current flowing through the shunt resistor 7 (P2). If a current is detected, the excitation current control unit 13 turns off FET5 (P3). If the current detection circuit 15 does not detect a current in this state, the error determination circuit 16 determines that the circuit is normal (P4 → P5).

[0015] If no current is detected in step P2 (OFF), the error determination circuit 16 determines that either FET5 or FET6 is stuck off and that an abnormality has occurred (P6). If a current is detected in step P4, the error determination circuit 16 determines that FET5 is stuck on and that an abnormality has occurred. Then, the error determination circuit 16 turns off FET6 to interrupt the current path (P7).

[0016] As shown in FIG. 3, when the purpose is solely diagnosis, the diagnosis control unit 14 keeps FET 6 off at all times. Steps P11 to P15 are the same as steps P1 to P5, but the branch in the judgment of step P12 is reversed, depending on whether or not current is detected. If no current is detected in either step P12 or P14, the error determination circuit 16 determines that the system is normal (P15). If current is detected in step P12, the error determination circuit 16 determines that FET 6 is stuck on and therefore an abnormality has occurred. Then, it turns off FET 5 to interrupt the current path (P16). If current is detected in step P14, the error determination circuit 16 determines that FETs 5 and 6 are stuck on and therefore an abnormality has occurred (P17).

[0017] The letters "A to D" attached to each of the decision steps P2, P4, P12, and P14 correspond to the four phases consisting of the combinations of the on and off states of FETs 5 and 6 shown in Fig. 4. If no current is detected in either phase A or B, the process shown in Fig. 3 determines that the system is "normal." If a current is detected in phase C but not in phase D, the process shown in Fig. 2 determines that the system is "normal."

[0018] As described above, according to this embodiment, the battery impedance measuring device 1 measures the AC impedance of the battery pack 3. The FETs 5 and 6 are arranged in a path through which an excitation current flows from the battery pack 3, and the excitation current flows through the shunt resistor 7 via the FETs 5 and 6. The excitation current control unit 13 and the diagnosis control unit 14 control the on / off of the FETs 5 and 6, respectively, and the current detection circuit 15 measures the voltage of the shunt resistor 7. The error determination circuit 16 diagnoses the conduction state of the FETs 5 and 6 based on the on / off states of the FETs 5 and 6 determined by the control units 13 and 14 and the results of current flow through the shunt resistor 7.

[0019] Since FETs 5 and 6 and shunt resistor 7 are arranged in a path through which the excitation current flows, the result of energization of shunt resistor 7 is determined according to the on / off states of FETs 5 and 6. Therefore, by comparing the two, error determination circuit 16 can diagnose whether the conduction states of FETs 5 and 6 are normal or abnormal. Furthermore, when error determination circuit 16 diagnoses that one of FETs 5 and 6 is stuck on, control units 13 and 14 turn off the other FET 5 and 6. As a result, even if one or more switch elements are stuck on, the other normal FET can interrupt the current.

[0020] Second Embodiment In the following, the same parts as those in the first embodiment are denoted by the same reference numerals and their explanations are omitted, and only the differences will be explained. In a battery impedance measuring device 1A of the second embodiment shown in Figure 5, an FET 6 is connected between the positive electrode of the assembled battery 3 and the resistive load 4, and accordingly, the shape of the circuit board 10A is also different.

[0021] 6 , a battery impedance measuring device 21 of the third embodiment includes an IC 22 replacing the IC 11, and the IC 22 includes an arithmetic circuit 23 replacing the error determination circuit 16, and a communication circuit 24. The two battery impedance measuring devices 21(1) and 21(2) communicate with a battery management system 25. The battery management system 25 is made up of a microcomputer (μC) 26 and includes an impedance calculation circuit 27, an error determination circuit 28, and a communication circuit 29.

[0022] These communication networks are daisy-chain connected, and the three communication circuits are connected as follows: Communication circuit 24(1) Transmission buffer of communication circuit 29 → reception buffer of communication circuit 24(2) Transmission buffer of communication circuit 24(2) → reception buffer of communication circuit 24(1)

[0023] Next, the operation of the third embodiment will be described. As shown in Fig. 7, the arithmetic circuit 23 transmits the current detection result and on / off information for FETs 5 and 6 via the communication circuit 24 to the microcomputer 26 (P31). In the microcomputer 26, the error determination circuit 28 determines whether the received current detection result and on / off information for FETs 5 and 6 match the normal case pattern shown in Fig. 4 (P32). If the normal case pattern matches, the battery impedance measuring device 21 continues current detection (P33). If the normal case pattern does not match, the microcomputer 26 outputs a signal to the IC 22 instructing it to turn off FETs 5 and 6 (P34).

[0024] 8, a battery impedance measuring device 21A of the fourth embodiment includes an error determination circuit 28 in an IC 22A, which was previously included in the microcomputer 26. The error determination performed by the microcomputer 26 in the third embodiment is now performed in the battery impedance measuring device 21A, and the determination result is sent to the microcomputer 26A.

[0025] 9, an IC 32 of a battery impedance measuring device 31 of the fifth embodiment includes a voltage detection circuit 33 and an error determination circuit 34 that replaces the error determination circuit 16. The three input terminals of the voltage detection circuit 33 are connected to the drain (node ​​A) of FET 5, the drain (node ​​B) and the source (node ​​C) of FET 6, respectively. The voltage detection circuit 33 detects the potentials of nodes A to C relative to ground, and the differential voltage between nodes B and C. The drain and source correspond to conduction terminals.

[0026] Next, the operation of the fifth embodiment will be described. Figure 10 shows the potentials of nodes A to C and the differential voltages between nodes A and B and between nodes B and C when the conduction states of FETs 5 and 6 are normal, corresponding to states 1 to 4 based on the on / off combinations of FETs 5 and 6. As shown in Figure 11, in state 1 (P41) in which FETs 5 and 6 are on, the voltage detection circuit 33 detects the differential voltage between nodes A and B and the differential voltage between nodes B and C (P42, P43). If each differential voltage is at a low level, it matches the normal pattern shown in Figure 10.

[0027] Subsequently, in state 2 where FET5 is turned off and FET6 is turned on (P44), the voltage detection circuit 33 detects the differential voltage between nodes A and B (P45). If the differential voltage is at a high level, it matches the normal pattern shown in FIG.

[0028] Next, the system switches to State 1 again, turning on FETs 5 and 6 (P46), and then switches to State 3, turning on FET 5 and turning off FET 6 (P47). The voltage detection circuit 33 detects the differential voltage between nodes B and C (P48). If the differential voltage is high, it matches the normal pattern shown in Figure 10, and the error determination circuit 34 determines that the system is "normal" (P49).

[0029] In step P42, if the differential voltage between nodes A and B is high in state 1, the pattern corresponds to state 2, and therefore the error determination circuit 34 determines that FET 5 is stuck-off abnormal (P50). Also, in step P43, if the differential voltage between nodes B and C is high in state 1, the pattern corresponds to state 3, and therefore the error determination circuit 34 determines that FET 6 is stuck-off abnormal (P51).

[0030] In step P45, if the differential voltage between nodes A and B is low in state 2, the pattern corresponds to state 1, so the error determination circuit 34 determines that FET5 has a fixed-on abnormality. FET6 is then turned off to cut off the current (P52). Also, in step P48, if the differential voltage between nodes B and C is low in state 3, the pattern corresponds to state 1, so the error determination circuit 34 determines that FET6 has a fixed-on abnormality. FET5 is then turned off to cut off the current (P53).

[0031] (Sixth embodiment) As shown in Figure 12, an IC 42 of a battery impedance measuring device 41 of the sixth embodiment has a configuration in which the FET 6 and the diagnostic control unit 14 are removed from the battery impedance measuring device 1 of the first embodiment, and the error determination circuit 16 is replaced with an error determination circuit 43.

[0032] Next, the operation of the sixth embodiment will be described. As shown in Figure 13, steps P1 to P5 are the same as those of the first embodiment. If no current is detected in step P2, the error determination circuit 43 determines that the FET 5 is stuck-off (P8). If a current is detected in step P4, the error determination circuit 43 determines that the FET 5 is stuck-on (P9).

[0033] In addition to the inventions described in the claims, this application also includes the following inventions: [1] A battery impedance measuring device for measuring the AC impedance of an assembled battery (3) formed by connecting a plurality of unit cells (2) in series, the battery impedance measuring device comprising: switch elements (5, 6) arranged in a path through which an excitation current flows from the assembled battery; a resistive element (7) through which the excitation current flows via the switch elements; a control unit (13, 14) for controlling the on / off of the switch elements; a measurement unit (15) for measuring the voltage of the resistive element; and a diagnostic unit (16, 28, 34, 43) for diagnosing the conduction state of the switch elements based on the on / off state of the switch elements determined by the control unit and the result of current flow through the resistive element. [2] The battery impedance measuring device according to [1], wherein two or more switch elements are arranged in the path as the switch elements, and the control unit turns off the other normal switch elements when the diagnostic unit diagnoses that one or more switch elements are stuck on. [3] The battery impedance measuring device according to [1] or [2], wherein the diagnostic unit (16, 28, 43) determines whether or not current is being applied to the resistance element based on the voltage measurement result by the measurement unit (15). [4] The battery impedance measuring device according to any one of [1] to [3], further comprising a voltage measurement unit (33) that measures the voltage of a conductive terminal of the switch element, and wherein the diagnostic unit (34) determines whether or not current is being applied to the resistance element based on the voltage measurement result by the voltage measurement unit.

[0034] (Other Embodiments) Three or more switch elements may be arranged in the current path of the excitation current. The switch elements are not limited to N-channel MOSFETs. Although the present disclosure has been described based on examples, it is understood that the present disclosure is not limited to these examples and structures. The present disclosure also encompasses various modifications and modifications within the scope of equivalents. In addition, various combinations and forms, including only one element, more than one element, or less than one element, are also within the scope and spirit of the present disclosure.

[0035] The means and / or functions provided by each device, etc., can be provided by software recorded in a tangible memory device and a computer that executes the software, software alone, hardware alone, or a combination thereof. For example, when a control device is provided by electronic circuits that are hardware, it can be provided by digital circuits including a large number of logic circuits, or analog circuits.

[0036] The control unit and the method described herein may be implemented by a special-purpose computer configured by configuring a processor and memory programmed to perform one or more functions embodied in a computer program. Alternatively, the control unit and the method described herein may be implemented by a special-purpose computer configured by configuring a processor with one or more dedicated hardware logic circuits. Alternatively, the control unit and the method described herein may be implemented by one or more special-purpose computers configured by combining a processor and memory programmed to perform one or more functions with a processor configured with one or more hardware logic circuits. Furthermore, the computer program may be stored as instructions executed by a computer on a computer-readable non-transitory tangible storage medium.

Claims

1. A battery impedance measuring device for measuring the AC impedance of a battery pack (3) formed by connecting a plurality of unit cells (2) in series, comprising: a switch element (5, 6) arranged in a path for flowing an excitation current from the battery pack; a resistive element (7) through which the excitation current is passed via the switch element; a control unit (13, 14) for controlling the on / off of the switch element; a measurement unit (15) for measuring the voltage of the resistive element; and a diagnosis unit (16, 28, 34, 43) for diagnosing the conduction state of the switch element based on the on / off state of the switch element controlled by the control unit and the result of current flow to the resistive element.

2. A battery impedance measuring device according to claim 1, wherein two or more switch elements are arranged in the path as the switch elements, and when the diagnostic unit diagnoses that one or more of the switch elements is stuck on, the control unit turns off the other normal switch elements.

3. A battery impedance measuring device according to claim 1 or 2, wherein the diagnostic unit (16, 28, 43) determines the result of energization of the resistance element based on the result of voltage measurement by the measurement unit (15).

4. A battery impedance measuring device according to claim 1 or 2, further comprising a voltage measuring unit (33) that measures the voltage of the conductive terminal of the switch element, and the diagnostic unit (34) determines the result of current flow to the resistance element based on the voltage measurement result by the voltage measuring unit.

Images