Battery impedance measurement device
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- DENSO CORP
- Filing Date
- 2024-04-25
- Publication Date
- 2026-07-03
Smart Images
Figure 00000000_0000_ABST
Abstract
Description
[Technical Field]
[0001] The present invention relates to a device for measuring the AC impedance of a battery pack. [Background technology]
[0002] 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 current based on the measurement results and the measurement results of the voltage of each unit battery. [Prior art documents] [Patent documents]
[0003] [Patent Document 1] International Publication No. 2020 / 003841 Summary of the Invention [Problem to be solved by the invention]
[0004] However, with the configuration of Patent Document 1, if the transistor for passing current from the battery fails and is stuck in the OFF state, it becomes impossible to measure the current and therefore the impedance.
[0005] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a battery impedance measuring device that can detect a failure in a current measuring switch element. [Means for solving the problem]
[0006] According to the battery impedance measuring device of claim 1, the AC impedance of an assembled battery (3) formed by connecting a plurality of unit cells (2) in series is measured. Switching elements (5, 6) are arranged in a path through which an excitation current flows from the assembled battery, and the excitation current is passed through a resistive element (7). Control units (13, 14) control the on / off of the switching elements, and a measuring unit (15) measures the voltage of the resistive element. A diagnosing unit (16, 28, 34, 43) diagnoses the conduction state of the switching elements based on the on / off state of the switching elements as determined by the control unit and the result of current flow through the resistive element.
[0007] 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.
[0008] According to the 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. Thus, even if one or more of the switch elements are stuck on, the current can be interrupted by the other normal switch elements. [Brief explanation of the drawings]
[0009] [Figure 1] FIG. 1 is a diagram showing the configuration of a battery impedance measuring device in a first embodiment. [Figure 2] Flowchart when generating excitation current [Figure 3] Diagnosis Flowchart [Figure 4] Diagram showing the four phases that are the combinations of the on and off states of the two FETs [Figure 5] FIG. 10 is a diagram showing the configuration of a battery impedance measuring device in a second embodiment. [Figure 6]FIG. 10 is a diagram showing the configuration of a battery impedance measuring device and a battery management system in a third embodiment. [Figure 7] 1 is a flowchart showing processing between a battery impedance measuring device and a battery management system. [Figure 8] FIG. 10 is a diagram showing the configuration of a battery impedance measuring device and a battery management system in a fourth embodiment. [Figure 9] FIG. 10 is a diagram showing the configuration of a battery impedance measuring device in a fifth embodiment. [Figure 10] The figure shows the potentials of each node and the differential voltage between nodes when the conduction state is normal, corresponding to states 1 to 4 according to the combination of the on and off states of the two FETs. [Figure 11] Diagnosis Flowchart [Figure 12] FIG. 13 is a diagram showing the configuration of a battery impedance measuring device in a sixth embodiment. [Figure 13] Flowchart when generating excitation current DETAILED DESCRIPTION OF THE INVENTION
[0010] (First embodiment) As shown in Fig. 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. The IC 11 includes functional blocks configured by hardware, microcomputer software, etc., 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.
[0011] The cell voltage detection and equalization unit 12 detects the voltage of each unit cell 2 and performs a process of equalizing 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 switching elements.
[0012] 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 conduction 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.
[0013] Next, the operation of this embodiment will be described. In FIGS. 2 to 4, (1) and (2) are circled numbers, with SW(1) representing FET 5 and SW(2) representing FET 6. As shown in FIG. 2, the diagnostic control unit 14 keeps FET 6 on at all times when generating an excitation current. Then, the excitation current control unit 13 turns on FET 5 (P1). Next, the current detection circuit 15 determines whether or not 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 FET 5 (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).
[0014] If no current is detected in step P2 (OFF), the error determination circuit 16 determines that either FET 5 or FET 6 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 FET 5 is stuck on and that an abnormality has occurred. Then, the error determination circuit 16 turns off FET 6 to interrupt the current path (P7).
[0015] 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 a current is detected. If no current is detected in either step P12 or P14, the error judgment circuit 16 determines that the circuit is normal (P15). If a current is detected in step P12, the error judgment circuit 16 determines that FET 6 is stuck on and that an abnormality has occurred. Then, it turns FET 5 off to interrupt the current path (P16). If a current is detected in step P14, the error judgment circuit 16 determines that FETs 5 and 6 are stuck on and that an abnormality has occurred (P17).
[0016] 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 circuit is "normal." If a current is detected in phase C but not in phase D, the process shown in Fig. 2 determines that the circuit is "normal."
[0017] 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 controlled by the control units 13 and 14 and the results of current flow through the shunt resistor 7.
[0018] Because FETs 5 and 6 and shunt resistor 7 are arranged in a path through which an excitation current flows, the result of current flow through 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.
[0019] (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 different parts are explained. In the battery impedance measuring device 1A of the second embodiment shown in Fig. 5, the 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.
[0020] (Third embodiment) 6, a battery impedance measuring device 21 of the third embodiment includes an IC22 replacing the IC11, and the IC22 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.
[0021] These communication networks are daisy-chain connected, and the connection configuration of the three communication circuits is 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)
[0022] 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 of FETs 5 and 6 from 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 of FETs 5 and 6 match the normal case pattern shown in Fig. 4 (P32). If they match the normal case pattern, the battery impedance measuring device 21 continues current detection (P33). If they do not match the normal case pattern, the microcomputer 26 outputs a signal to the IC 22 instructing it to turn off FETs 5 and 6 (P34).
[0023] (Fourth embodiment) 8, the battery impedance measuring device 21A of the fourth embodiment includes an error determination circuit 28 in an IC 22A, which is provided in the microcomputer 26. The error determination performed by the microcomputer 26 in the third embodiment is performed in the battery impedance measuring device 21A, and the determination result is transmitted to the microcomputer 26A.
[0024] (Fifth embodiment) 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. 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 A to C. The drain and source correspond to conduction terminals.
[0025] Next, the operation of the fifth embodiment will be described. Fig. 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 according to the on / off combinations of FETs 5 and 6. As shown in Fig. 11, in state 1 (P41) in which FETs 5 and 6 are on, the voltage detection circuit 33 detects the differential voltages between nodes A and B and between nodes B and C (P42, P43). If each differential voltage is at a low level, it matches the normal pattern shown in Fig. 10.
[0026] Subsequently, in state 2 (P44) where FET5 is turned off and FET6 is turned on, 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.
[0027] Next, the system switches back to State 1, 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 it to be "normal" (P49).
[0028] In step P42, if the differential voltage between nodes A and B is at a high level in state 1, the pattern corresponds to state 2, and therefore 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 at a high level in state 1, the pattern corresponds to state 3, and therefore error determination circuit 34 determines that FET 6 is stuck-off abnormal (P51).
[0029] In step P45, if the differential voltage between nodes A and B is low in state 2, the pattern corresponds to state 1, and therefore the error determination circuit 34 determines that FET 5 has a fixed-on abnormality. FET 6 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, and therefore the error determination circuit 34 determines that FET 6 has a fixed-on abnormality. FET 5 is then turned off to cut off the current (P53).
[0030] (Sixth embodiment) As shown in Figure 12, the IC42 of the battery impedance measuring device 41 of the sixth embodiment has a configuration in which the FET6 and diagnostic control unit 14 are removed from the battery impedance measuring device 1 of the first embodiment, and the error judgment circuit 16 is replaced with an error judgment circuit 43.
[0031] Next, the operation of the sixth embodiment will be described. As shown in Fig. 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 fixed-off abnormality (P8). If a current is detected in step P4, the error determination circuit 43 determines that the FET 5 is fixed-on abnormality (P9).
[0032] In addition to the inventions described in the claims, this case also includes the following inventions: [1] This device measures the AC impedance of a battery pack (3) made up of a plurality of unit cells (2) connected in series, a switch element (5, 6) disposed on a path through which an excitation current flows from the battery pack; a resistance element (7) through which the excitation current is passed via the switch element; a control unit (13, 14) that controls the on / off of the switch element; a measurement unit (15) that measures the voltage of the resistance element; a diagnostic unit (16, 28, 34, 43) that diagnoses the conduction state of the switch element based on the on / off state of the switch element by the control unit and the result of current flow to the resistance element.
[0033] [2] As the switch element, two or more switch elements are arranged in the path, The battery impedance measuring device according to [1], wherein when the diagnosing unit diagnoses that any one or more switch elements are stuck on, the control unit turns off other normal switch elements.
[0034] [3] The battery impedance measuring device according to [1] or [2], wherein the diagnosing unit (16, 28, 43) determines the result of energizing the resistance element based on the voltage measurement result by the measuring unit (15).
[0035] [4] a voltage measuring unit (33) for measuring a voltage at a conductive terminal of the switch element; The battery impedance measuring device according to any one of [1] to [3], wherein the diagnosing unit (34) determines the result of energizing the resistance element based on the result of measuring the voltage by the voltage measuring unit.
[0036] (Other embodiments) Three or more switch elements may be arranged in the current path of the excitation current. The switch element is not limited to an N-channel MOSFET. Although the present disclosure has been described with reference to the embodiments, it is understood that the present disclosure is not limited to the embodiments or structures. The present disclosure also encompasses various modifications and equivalent modifications. 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.
[0037] 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, if 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.
[0038] 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. [Explanation of symbols]
[0039] In the drawing, 1 is a battery impedance measuring device, 2 is a unit cell, 3 is a battery pack, 5 and 6 are N-channel MOSFETs, 7 is a shunt resistor, 13 is an excitation current control unit, 14 is a diagnosis control unit, 15 is a current detection circuit, and 16 is an error determination circuit.
Claims
1. This device measures the AC impedance of a battery pack (3) consisting of multiple unit cells (2) connected in series. Switch elements (5, 6) are arranged in the path through which the excitation current flows from the aforementioned battery pack, A resistive element (7) through which the excitation current is passed via this switching element, A control unit (13, 14) that controls the on / off state of the switch element, A measuring unit (15) for measuring the voltage of the resistor element, The system includes a diagnostic unit (16, 28, 34, 43) that diagnoses the conductivity state of the switch element based on the on / off state of the switch element by the control unit and the result of energizing the resistive element, As the aforementioned switch element, two or more switch elements are arranged in the path. The control unit is a battery impedance measuring device that, when the diagnostic unit diagnoses that one or more switch elements are stuck in the "on" position, turns off the other normal switch elements.
2. The battery impedance measuring device according to claim 1, wherein the diagnostic unit (16, 28, 43) determines the result of energizing the resistive element based on the voltage measurement result by the measurement unit (15).
3. The switch element is equipped with a voltage measuring unit (33) for measuring the voltage at the conductive terminal, The battery impedance measuring device according to claim 1, wherein the diagnostic unit (34) determines the result of energizing the resistive element based on the voltage measurement result by the voltage measurement unit.