Power storage device

Abstract

This power storage device comprises a power storage element and a management device. The management device comprises: a circuit breaker that cuts off a current path between the power storage element and a connection terminal for connecting the power storage element to the outside; a control unit; and a magnetic sensor. The circuit breaker includes a composite switch configured by connecting a plurality of semiconductor switches in parallel, and one of the plurality of semiconductor switches is a first semiconductor switch. The magnetic sensor is disposed in the vicinity of the first semiconductor switch or a conductive path connected to the first semiconductor switch, and is not in electrical contact with the first semiconductor switch. The control unit executes: current value acquisition processing for acquiring a first current value, which is the value of a current flowing in the first semiconductor switch, on the basis of input from the magnetic sensor; and determination processing for determining whether or not the acquired first current value is within a prescribed allowable range.

Description

Power storage device

[0001] The present disclosure relates to an electricity storage device.

[0002] Conventionally, energy storage devices have been developed that include an energy storage element and a circuit breaker that interrupts a current path of a current flowing through the energy storage element (see, for example, Patent Document 1 below). Semiconductor switches such as MOSFETs (Metal Oxide Semiconductor Field Effect Transistors), IGBTs (Insulated Gate Bipolar Transistors), and bipolar transistors are sometimes used as circuit breakers. When bonding wires or gate oxide films inside the semiconductor are damaged by electrical or thermal stress, the semiconductor switch may lose the ability to control its conductive or non-conductive state. For example, a known failure of a semiconductor switch is one in which the semiconductor switch does not close even when an appropriate gate voltage is applied to the semiconductor switch (hereinafter referred to as an open fault).

[0003] Japanese Patent Application Laid-Open No. 2016-118571

[0004] In order to reduce circuit breaker costs and simplify wiring, circuit breakers are sometimes constructed from multiple semiconductor switches connected in parallel, with the gate wiring of the multiple semiconductor switches shared. If one of the semiconductor switches in such a circuit breaker experiences an open circuit fault, current may concentrate in the normal semiconductor switches, causing the normal semiconductor switches to overheat and resulting in circuit breaker malfunction. However, if one of the semiconductor switches experiences an open circuit fault, current may flow through the other normal semiconductor switches, causing the circuit breaker to appear to operate normally, making it difficult to detect the circuit breaker fault.

[0005] To solve the above problem, it is conceivable to connect a current sensor to each of the semiconductor switches and determine whether or not each semiconductor switch has failed based on the current value of the semiconductor switch. However, this configuration is not desirable from the viewpoint of space saving and cost reduction.

[0006] It is also possible to connect a current sensor to one of the multiple semiconductor switches and determine whether any of the multiple semiconductor switches has failed based on the current value of that specific semiconductor switch. However, if the current sensor is connected to only one specific semiconductor switch, the electrical resistance of the current sensor will cause the current value flowing through that specific semiconductor switch to be smaller than the current values ​​flowing through the other semiconductor switches. If the current values ​​flowing through the multiple semiconductor switches are uneven in this way, one of the multiple semiconductor switches may be more susceptible to failure.

[0007] The present disclosure was completed in light of the above circumstances, and has an object to diagnose open faults in semiconductor switches connected in parallel with a simple configuration.

[0008] The energy storage device of the present disclosure includes an energy storage element and a management device. The management device includes a circuit breaker that interrupts a current path between the energy storage element and a connection terminal for connecting the energy storage element to an external device, a control unit, and a magnetic sensor. The circuit breaker includes a composite switch configured by connecting a plurality of semiconductor switches in parallel, one of the plurality of semiconductor switches being a first semiconductor switch. The magnetic sensor is disposed near the first semiconductor switch or a conductive path connected to the first semiconductor switch, and is not in electrical contact with the first semiconductor switch. The control unit executes a current value acquisition process that acquires a first current value, which is the value of a current flowing through the first semiconductor switch, based on an input from the magnetic sensor, and a determination process that determines whether the acquired first current value is within a predetermined tolerance range.

[0009] According to the present disclosure, it is possible to diagnose open faults in semiconductor switches connected in parallel with a simple configuration.

[0010] FIG. 1 is a diagram showing the electrical configuration of the power storage device according to the first embodiment. FIG. 2 is an explanatory diagram illustrating a magnetic field generated by a current. FIG. 3 is a diagram showing a schematic arrangement of semiconductor switches and magnetic sensors. FIG. 4 is a diagram showing a schematic arrangement of semiconductor switches and magnetic sensors different from that shown in FIG. 3. FIG. 5 is a flowchart showing an open circuit failure diagnosis process according to the first embodiment. FIG. 6 is a flowchart showing an open circuit failure diagnosis process according to the second embodiment.

[0011] (Summary of the Present Embodiment) [1] An energy storage device according to the present disclosure includes an energy storage element and a management device. The management device includes a circuit breaker configured to interrupt a current path between the energy storage element and a connection terminal for connecting the energy storage element to an external device, a control unit, and a magnetic sensor. The circuit breaker includes a composite switch configured by connecting a plurality of semiconductor switches in parallel, one of which is a first semiconductor switch. The magnetic sensor is disposed near the first semiconductor switch or a conductive path connected to the first semiconductor switch, and is not in electrical contact with the first semiconductor switch. The control unit executes a current value acquisition process to acquire a first current value, which is the value of a current flowing through the first semiconductor switch, based on an input from the magnetic sensor, and a determination process to determine whether the acquired first current value is within a predetermined tolerance range.

[0012] With this configuration, the magnetic sensor can detect the value of the first current flowing through the first semiconductor switch in a non-contact manner, thereby enabling a simple configuration to diagnose a fault in the composite switch without applying a load to the multiple semiconductor switches.

[0013] [2] In the above [1], it is preferable that the plurality of semiconductor switches are arranged side by side in a first direction, and the first semiconductor switch is arranged at an end of the plurality of semiconductor switches in the first direction.

[0014] With this configuration, the measurement accuracy of the magnetic sensor can be improved, and therefore the accuracy of fault diagnosis of the composite switch can be improved.

[0015] [3] In the above [1] or [2], it is preferable that the control unit is configured to execute the current value acquisition process and the determination process multiple times at a predetermined timing, and the determination process based on the result of the current value acquisition process when the current value flowing through the current path is equal to or greater than a predetermined first threshold value is a first determination process, and when the multiple determination processes include the first determination process, the control unit diagnoses whether or not there is a failure in the composite switch based on the result of the first determination process.

[0016] With this configuration, a fault diagnosis of the composite switch is performed based on the result of the judgment process when the current value flowing through the current path is equal to or greater than the first threshold value, thereby improving the accuracy of the fault diagnosis of the composite switch.

[0017] [4] In the above [3], the judgment process based on the result of the current value acquisition process when the current value flowing through the current path is less than the first threshold value and equal to or greater than a predetermined second threshold value is a second judgment process, and if the multiple judgment processes do not include the first judgment process, they include two or more consecutive second judgment processes, and it is preferable that the composite switch is diagnosed as faulty if the first current value is not within the allowable range in two consecutive second judgment processes.

[0018] With this configuration, even when the value of the current flowing through the current path is less than the first threshold, it is possible to provide an opportunity to perform a fault diagnosis on the composite switch while ensuring the accuracy of the fault diagnosis on the composite switch.

[0019] First Embodiment A first embodiment of the present disclosure will be described with reference to Fig. 1 to Fig. 5. A power storage device 1 according to this embodiment is mounted on a vehicle such as an engine vehicle, an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), a two-wheeled vehicle, or another mobile object.

[0020] As shown in FIG. 1 , the energy storage device 1 includes a battery pack 2, a battery management system (hereinafter referred to as BMS) 3, and connection terminals 4A and 4B. The battery pack 2 is an example of an energy storage element and is configured by connecting multiple cells C in series. Each cell C is a rechargeable secondary battery, such as a lithium-ion battery. The battery pack 2 of this embodiment has four cells C. Note that the battery pack may be configured with only one cell, or two, three, or five or more cells connected in series.

[0021] The BMS 3 is an example of a management device and includes a control unit 31, a circuit breaker 32, gate drivers 36A and 36B, magnetic sensors 37A and 37B, and a current sensor 38.

[0022] The control unit 31 has a central processing unit (hereinafter referred to as CPU) and memory. Various programs for controlling the operation of the BMS 3 are stored in the memory, and the CPU controls each part of the BMS 3 in accordance with the programs read from the memory. The memory includes RAM and ROM. Note that the media on which the various programs are stored may be non-volatile memories such as a CD-ROM, a hard disk drive, or a flash memory, in addition to RAM.

[0023] The circuit breaker 32 is provided in the current path 5 between the battery pack 2 and the connection terminal 4A. The circuit breaker 32 includes a discharge cutoff unit 33 and a charge cutoff unit 34. The discharge cutoff unit 33 cuts off the current (discharge current) that flows when the battery pack 2 supplies power to a load or the like. The charge cutoff unit 34 cuts off the current (charge current) that flows when the battery pack 2 is charged by a charger. The discharge cutoff unit 33 and the charge cutoff unit 34 are each an example of a composite switch.

[0024] The discharge cutoff unit 33 is configured to include three semiconductor switches 35A, 35B, and 35C connected in parallel. The charge cutoff unit 34 is configured to include three semiconductor switches 35D, 35E, and 35F connected in parallel. In this embodiment, the semiconductor switches 35A to 35F are FETs. More specifically, the semiconductor switches 35A to 35F are N-channel MOSFETs. Hereinafter, when the semiconductor switches 35A to 35F are not to be distinguished, they may be referred to as semiconductor switch 35. Parasitic diodes DA to DF exist in each of the semiconductor switches 35A to 35F.

[0025] The forward direction of the parasitic diodes DA to DC is the charging direction of the battery pack 2. When the semiconductor switches 35A to 35C are opened, the discharging current from the battery pack 2 is cut off, but the charging current to the battery pack 2 flows through the parasitic diodes DA to DC. The forward direction of the parasitic diodes DD to DF is the discharging direction of the battery pack 2. When the semiconductor switches 35D to 35F are opened, the charging current to the battery pack 2 is cut off, but the discharging current from the battery pack 2 flows through the parasitic diodes DD to DF.

[0026] The sources of the discharge cutoff unit 33 and the charge cutoff unit 34 are connected in common, i.e., back-to-back. The drain of the discharge cutoff unit 33 is connected to the positive electrode of the battery pack 2. The drain of the charge cutoff unit 34 is connected to the connection terminal 4A. The gates of the discharge cutoff unit 33 and the charge cutoff unit 34 are connected to gate drivers 36A and 36B, respectively. The gates of the semiconductor switches 35A to 35C are unified. The gates of the semiconductor switches 35D to 35F are unified.

[0027] Gate drivers 36A, 36B are each configured to receive a control signal from control unit 31, and in response to the control signal from control unit 31, discharge cut-off unit 33 and charge cut-off unit 34 are each set to a closed (on) state, an open (off) state, or a diagnostic state, which will be described later.

[0028] The current sensor 38 measures the current flowing through the current path 5 between the battery pack 2 and the connection terminal 4A. The current sensor 38 transmits the current measurement result to the control unit 31.

[0029] The magnetic sensor 37A is configured to measure a magnetic field (magnetic flux density) generated by a current flowing through the semiconductor switch 35A (an example of a first semiconductor switch). The magnetic sensor 37B is configured to measure a magnetic field generated by a current flowing through the semiconductor switch 35D (an example of a first semiconductor switch). The magnetic sensors 37A and 37B are not electrically in contact with the semiconductor switches 35A and 35D, respectively. In other words, the magnetic sensors 37A and 37B do not constitute part of the current path 5.

[0030] For example, as shown in Figure 2, when a current (solid arrow) flows through a conductor extending in the vertical direction, a magnetic field is generated in the circumferential direction of the conductor, as shown by the dashed arrow. The magnitude of this magnetic field is proportional to the current value and inversely proportional to the horizontal distance from the conductor (Ampere's Law). Therefore, for example, by placing a magnetic sensor 37A near semiconductor switch 35A, the value of the current flowing through semiconductor switch 35A can be calculated based on the magnetic field detected by magnetic sensor 37A.

[0031] In this embodiment, the magnetic sensors 37A and 37B are, for example, Hall elements. A current is supplied to the Hall elements from a predetermined power source. When the Hall elements are subjected to a magnetic field, a Hall voltage is generated in the Hall elements in a direction perpendicular to both the direction of the current and the direction of the magnetic field. The Hall voltage is proportional to the value of the current supplied to the Hall elements and the magnetic field applied to the Hall elements. The control unit 31 is capable of acquiring this Hall voltage. Alternatively, the magnetic sensors 37A and 37B may be ICs including a Hall element, a power supply, an amplifier circuit, etc., and may be configured to transmit a value proportional to the Hall voltage to the control unit 31.

[0032] As shown in FIG. 3 , three semiconductor switches 35A, 35B, and 35C are arranged on a circuit board in a line in the first direction D1 (left-right direction in the figure). A control unit 31 is also mounted on this circuit board. Of the three semiconductor switches 35A, 35B, and 35C, the semiconductor switch 35A is arranged at one end in the first direction D1 (right side in the figure). Of the three semiconductor switches 35A, 35B, and 35C, the semiconductor switch 35C is arranged at the other end in the first direction D1 (left side in the figure). The semiconductor switch 35B is arranged between the two semiconductor switches 35A and 35C in the first direction D1. In this embodiment, a current (discharge current) flows downward in the figure through each of the semiconductor switches 35A, 35B, and 35C.

[0033] The three semiconductor switches 35D, 35E, and 35F are arranged at positions offset in the vertical direction from the three semiconductor switches 35A, 35B, and 35C in the figure. The three semiconductor switches 35D, 35E, and 35F are arranged side by side in the first direction D1 (left and right direction in the figure). Of the three semiconductor switches 35D, 35E, and 35F, the semiconductor switch 35D is arranged at the end on one side (right side in the figure) in the first direction D1. Of the three semiconductor switches 35D, 35E, and 35F, the semiconductor switch 35F is arranged at the end on the other side (left side in the figure) in the first direction D1. The semiconductor switch 35E is arranged between the two semiconductor switches 35D and 35F in the first direction D1. In this embodiment, current (charging current) flows upward in the figure through each of the semiconductor switches 35D, 35E, and 35F.

[0034] A magnetic sensor 37A is disposed near the semiconductor switch 35A on the circuit board. Specifically, the magnetic sensor 37A is disposed on one side (the right side in the figure) of the semiconductor switch 35A in the first direction D1. This configuration reduces the distance between the semiconductor switch 35A and the magnetic sensor 37A in a direction perpendicular to the direction (downward in the figure) in which current flows through the semiconductor switch 35A, while increasing the distance between the other semiconductor switches 35B and 35C and the magnetic sensor 37A. This makes it easier for the magnetic sensor 37A to detect the magnetic field generated by the current flowing through the semiconductor switch 35A.

[0035] The magnetic sensor 37A may be disposed near a conductive path connected to the semiconductor switch 35A and through which a current of the same magnitude as that of the semiconductor switch 35A flows. For example, as shown in FIG. 4 , the current path 5 between the battery pack 2 and the discharge cutoff unit 33 includes a main conductive path 6, a first conductive path 7A branching from the main conductive path 6 and connected to the semiconductor switch 35A, a second conductive path 7B branching from the main conductive path 6 and connected to the semiconductor switch 35B, and a third conductive path 7C branching from the main conductive path 6 and connected to the semiconductor switch 35C. The magnetic sensor 37A is disposed near the first conductive path 7A. This configuration may further reduce the distance between the first conductive path 7A and the magnetic sensor 37A and further increase the distance between the second conductive path 7B and the third conductive path 7C and the magnetic sensor 37A in a direction perpendicular to the direction of current flow through the first conductive path 7A (the up-down direction in the figure). Therefore, the magnetic sensor 37A may be able to more easily detect the magnetic field generated by the current flowing through the first conductive path 7A.

[0036] As described above, the magnetic sensor 37A is configured to include at least a Hall element. A current flows through the Hall element in a direction perpendicular to the thickness direction of the circuit board (the surface direction of the circuit board). Because the direction of the current flowing through the semiconductor switch 35A is vertical as shown in the figure, a magnetic field is applied to the Hall element arranged on the circuit board in a direction substantially parallel to the thickness direction of the circuit board (the direction perpendicular to the plane of the paper). Because the direction of the current flowing through the Hall element and the direction of the magnetic field are substantially perpendicular to each other, a finite Hall voltage is generated in the Hall element.

[0037] In this embodiment, the distance between the magnetic sensor 37A and the semiconductor switch 35A (or the first conductive path 7A) and the value of the current supplied to the Hall element are each set to a predetermined constant, so that the control unit 31 can calculate the value of the current (an example of the first current value) flowing through the semiconductor switch 35A from the Hall voltage (or a value proportional to the Hall voltage) acquired from the magnetic sensor 37A.

[0038] 3, a magnetic sensor 37B is disposed near the semiconductor switch 35D on the circuit board. Specifically, the magnetic sensor 37B is disposed on one side (the right side in the figure) of the semiconductor switch 35D in the first direction D1. This configuration reduces the distance between the semiconductor switch 35D and the magnetic sensor 37B in a direction perpendicular to the direction (upward in the figure) in which current flows through the semiconductor switch 35D, and increases the distance between the other semiconductor switches 35E and 35F and the magnetic sensor 37B. This makes it easier for the magnetic sensor 37B to detect the magnetic field generated by the current flowing through the semiconductor switch 35D.

[0039] The magnetic sensor 37B may be disposed near a conductive path connected to the semiconductor switch 35D and through which a current of the same magnitude as that of the semiconductor switch 35D flows (see FIG. 4).

[0040] As described above, the magnetic sensor 37B is configured to include at least a Hall element. A current flows through the Hall element in a direction perpendicular to the thickness direction of the circuit board (the surface direction of the circuit board). Because the direction of the current flowing through the semiconductor switch 35D is vertical as shown in the figure, a magnetic field is applied to the Hall element arranged on the circuit board in a direction substantially parallel to the thickness direction of the circuit board (the direction perpendicular to the plane of the paper). Because the direction of the current flowing through the Hall element and the direction of the magnetic field are substantially perpendicular to each other, a finite Hall voltage is generated in the Hall element.

[0041] In this embodiment, the distance between the magnetic sensor 37B and the semiconductor switch 35D (or a conductive path through which a current of the same magnitude as that of the semiconductor switch 35D flows) and the value of the current supplied to the Hall element are each set to a predetermined constant. Therefore, the control unit 31 can calculate the value of the current (an example of the first current value) flowing through the semiconductor switch 35D from the Hall voltage (or a value proportional to the Hall voltage) acquired from the magnetic sensor 37B.

[0042] The control unit 31 of this embodiment diagnoses whether or not any of the semiconductor switches 35 included in the combined switch (the discharge cutoff unit 33 or the charge cutoff unit 34) has an open circuit fault (open circuit fault diagnosis process) in the procedure shown in Fig. 5. Here, the procedure for the open circuit fault diagnosis process will be described in detail using the case where the combined switch to be diagnosed is the discharge cutoff unit 33 as an example.

[0043] First, the control unit 31 inputs an ON signal to the gate driver 36A to close the semiconductor switches 35A to 35C of the discharge cutoff unit 33 (S1). This causes a current to flow through the semiconductor switches 35A to 35C. In other words, a discharge current flows through the current path 5 between the battery pack 2 and the connection terminal 4A, and no current flows through the parasitic diodes DA to DC.

[0044] Next, the control unit 31 acquires a value related to the Hall voltage transmitted from the magnetic sensor 37A, and also acquires a current value I flowing through the current path 5 transmitted from the current sensor 38. ＭＡＩＮ Here, the Hall voltage measured by the magnetic sensor 37A and the current value I measured by the current sensor 38 are obtained (S2). ＭＡＩＮ The measurements are performed at approximately the same timing.

[0045] The control unit 31 determines the value of the current flowing through the semiconductor switch 35A (hereinafter referred to as the first current value I) based on the input (value related to the Hall voltage) from the magnetic sensor 37A of S2. １ ) is calculated (current value acquisition process, S3). Specifically, the first current value I is calculated by multiplying the numerical value input from the magnetic sensor 37A by a predetermined coefficient. １ The predetermined coefficient can be determined experimentally in advance.

[0046] Next, the control unit 31 calculates the first current value I １is determined to be within the allowable range (determination process, S4). The allowable range is a range of values ​​that can be assumed when none of the semiconductor switches 35A to 35C has an open circuit fault. When none of the semiconductor switches 35A to 35C has an open circuit fault, it is considered that the same amount of current flows through each of the semiconductor switches 35A to 35C. In other words, each of the semiconductor switches 35A to 35C has a current value I ＭＡＩＮ is divided by the number of semiconductor switches 35A to 35C that make up the discharge cutoff unit 33, ＭＡＩＮ The allowable range is set by taking into consideration the individual differences in the electrical characteristics of the semiconductor switches 35A to 35C. ＭＡＩＮ For example, for a value X where 0<X<1, the lower limit of the allowable range is the average current value I ＭＡＩＮ / 3 multiplied by (1-X), and the upper limit of the allowable range is the average current value I ＭＡＩＮ It may be obtained by multiplying 1 / 3 by (1+X).

[0047] Hereinafter, the first current value I that is assumed when at least one of the semiconductor switches 35A to 35C has an open circuit fault will be referred to as a first current value I １ The following are listed:

[0048] If the semiconductor switch 35A has an open circuit fault, no current flows through the semiconductor switch 35A, and the first current value I １ is assumed to be zero.

[0049] When only one of the semiconductor switches 35B and 35C among the semiconductor switches 35A to 35C has an open circuit fault, the current value I ＭＡＩＮ is divided into two semiconductor switches 35 including the semiconductor switch 35A, and the first current value I １ is approximately I ＭＡＩＮ / 2.

[0050] When the semiconductor switches 35B and 35C among the semiconductor switches 35A to 35C have an open circuit fault, the current value I ＭＡＩＮ flows only through the semiconductor switch 35A, the first current value I１ is I ＭＡＩＮ It is assumed that this is the case.

[0051] The allowable range is the first current value I when at least one of the semiconductor switches 35A to 35C has an open circuit failure. １ is set to be outside the tolerance range. Specifically, the lower limit of the tolerance range is set to be greater than zero, and the upper limit of the tolerance range is set to be greater than I ＭＡＩＮ It is set to be smaller than / 2.

[0052] The control unit 31 determines the first current value I １ is within the allowable range, that is, if the first current value I1 is equal to or greater than the lower limit of the allowable range and equal to or less than the upper limit of the allowable range (S4: YES), it is determined that none of the semiconductor switches 35A to 35C has an open circuit fault, that is, there is no open circuit fault (S5).

[0053] The control unit 31 determines the first current value I １ is not within the allowable range (outside the allowable range), i.e., the first current value I １ is smaller than the lower limit of the allowable range or larger than the upper limit of the allowable range (S4: NO), it is determined that at least one of the semiconductor switches 35A to 35C has an open circuit fault, i.e., an open circuit fault has occurred (S6). This completes the open circuit fault diagnosis process for the discharge cutoff unit 33.

[0054] The control unit 31 may include a display unit that displays text information of the diagnosis result (e.g., "Open fault present," "No open fault present," etc.) after S5 or S6. Alternatively, the control unit 31 may notify the user terminal of the information of the diagnosis result.

[0055] The same procedure as above can be used for the open circuit fault diagnosis process of the charge cutoff unit 34. However, the open circuit fault diagnosis process of the charge cutoff unit 34 is executed when the semiconductor switches 35D to 35F are closed and a charging current is flowing through the current path 5.

[0056] (Effects of the First Embodiment) In the first embodiment, the magnetic sensor 37A detects the first current value I １Therefore, with a simple configuration, it is possible to diagnose a failure in the compound switch (discharge cutoff unit 33) without applying a load to the plurality of semiconductor switches 35A to 35C.

[0057] In the first embodiment, the semiconductor switches 35A to 35C are arranged side by side in the first direction D1, and the first semiconductor switch (semiconductor switch 35A) is arranged at the end of the semiconductor switches 35A to 35C in the first direction D1. This improves the measurement accuracy of the magnetic sensor 37A, thereby improving the accuracy of fault diagnosis of the composite switch (discharge cut-off unit 33).

[0058] Second Embodiment A second embodiment of the present disclosure will be described with reference to Fig. 6. The configuration of this embodiment is substantially the same as that of the first embodiment. In this embodiment, the open fault diagnosis process of the combined switch by the control unit 31 differs from the flow of the first embodiment (see Fig. 5).

[0059] As explained in the first embodiment, the allowable range used in the determination process is the current value I ＭＡＩＮ The accuracy of the open circuit fault diagnosis process may be poor due to noise, the measurement accuracy of the magnetic sensors 37A and 37B, or the like, depending on the configuration of the energy storage device 1. For example, if the energy storage device 1 is used for low current applications and the current value I ＭＡＩＮ When the difference is not large or when the number of semiconductor switches 35 constituting the composite switch is large, the tolerance becomes narrow. Therefore, for example, it is possible that an open circuit fault may be erroneously diagnosed even when there is actually no open circuit fault.

[0060] In the second embodiment, the current value I ＭＡＩＮ The flow of the open fault diagnosis process is modified depending on the magnitude of the error. This makes it possible to suppress misdiagnosis of open faults and ensure opportunities for open fault diagnosis process.

[0061] 6, the control unit 31 of the second embodiment is configured to execute the current value acquisition process and the determination process multiple times at a predetermined timing (S10). ＭＡＩＮ The predetermined timing includes, for example, when the mobile object on which the power storage device 1 is mounted is in use, or when charging of the power storage device 1 starts.

[0062] In this embodiment, the current value I ＭＡＩＮ The determination process is classified into a first determination process, a second determination process, or a third determination process depending on the magnitude of the current value I ＭＡＩＮ is a predetermined first threshold I Ｓ１ The determination process based on the result of the current value acquisition process when the current value I of the current path 5 is equal to or greater than the reference value I is referred to as the first determination process. ＭＡＩＮ is the first threshold I Ｓ１ Less than a predetermined second threshold I Ｓ２ (<I Ｓ１ The determination process based on the result of the current value acquisition process when the current value I of the current path 5 is equal to or greater than the first determination process is referred to as the second determination process. ＭＡＩＮ is the second threshold I Ｓ２ The determination process based on the result of the current value acquisition process when the current value is less than the first threshold I is referred to as the third determination process. The determination in the first determination process is highly accurate. The determination in the second determination process is medium accurate. The determination in the third determination process is low accurate. Ｓ１ and the second threshold I Ｓ２ can be set based on experiments or the like.

[0063] If the multiple determination processes in S10 include the first determination process (S11: YES), the presence or absence of an open circuit fault is diagnosed based on the result of the first determination process (S12). １ If the first current value I is within the allowable range, the control unit 31 diagnoses that there is no open circuit fault. １ If it is not within the tolerance range (outside the tolerance range), it is diagnosed as having an open fault.

[0064] If the multiple determination processes in S10 do not include the first determination process (S11: NO) and include two or more consecutive second determination processes (S13: YES), the control unit 31 determines whether the first current value I １ In the second determination process, it is determined whether the first current value I is outside the allowable range (S14). １ If the first current value I is outside the allowable range (S14: YES), the control unit 31 diagnoses that an open circuit fault has occurred (S15). １ is outside the allowable range (S14: YES), the control unit 31 diagnoses that there is no open circuit fault (S16). １ is outside the allowable range, but the two second determination processes are not consecutive (i.e., the first current value I １ is within the allowable range), it is determined that there is no open fault.

[0065] In the second determination process, the first current value I １ is outside the allowable range (S14: YES), the control unit 31 may not diagnose the presence or absence of an open circuit failure instead of S16.

[0066] If the multiple determination processes in S10 do not include the first determination process (S11: NO) and do not include two or more consecutive second determination processes (S13: NO), the control unit 31 does not diagnose the presence or absence of an open fault (S17). This completes the open fault diagnosis process for the combined switch of embodiment 2.

[0067] (Effects of the Second Embodiment) In the second embodiment, the current value I ＭＡＩＮ The accuracy of the fault diagnosis of the composite switch can be improved by changing the conditions for the fault diagnosis of the composite switch according to the magnitude of the error. That is, when the multiple determination processes include the first determination process, the fault diagnosis of the composite switch is performed based on the result of the first determination process, so that the accuracy of the fault diagnosis of the composite switch can be improved.

[0068] In the second embodiment, even if the multiple determination processes do not include the first determination process, the multiple determination processes may include two or more consecutive second determination processes, and the first current value I １ If the current value I is outside the allowable range, the control unit 31 diagnoses that an open circuit fault has occurred. ＭＡＩＮ Even when the error is not large, it is possible to provide an opportunity to diagnose a fault in the compound switch while ensuring the accuracy of the fault diagnosis of the compound switch.

[0069] <Other Embodiments> The present disclosure is not limited to the first and second embodiments described above and illustrated in the drawings, but is intended to include all modifications within the scope and meaning equivalent to the claims. The technical scope of the present disclosure also includes, for example, the following embodiments.

[0070] The open circuit fault diagnosis process for the composite switch of the first embodiment may be executed only under a predetermined condition. For example, when the current value I ＭＡＩＮ is the first threshold I Ｓ１ Only if the above conditions are met, the open fault diagnosis process for the compound switch may be executed.

[0071] In the first embodiment, the magnetic sensors 37A and 37B are configured to transmit numerical values ​​related to the Hall voltage to the control unit 31, but the magnetic sensors may also be configured to calculate a magnetic field or a first current value and transmit the magnetic field or the first current value to the control unit.

[0072] In the first embodiment, the circuit breaker 32 includes two compound switches, the discharge circuit breaker 33 and the charge circuit breaker 34, but the circuit breaker may include one compound switch or three or more compound switches.

[0073] In embodiment 1, the discharge cut-off unit 33 and the charge cut-off unit 34 each have three semiconductor switches 35 connected in parallel, but the composite switch may also have two or four or more semiconductor switches connected in parallel.

[0074] In the first embodiment, the magnetic sensors 37A and 37B are disposed on the surface of the circuit board on which the semiconductor switches 35A and 35D are mounted, but the magnetic sensors may be disposed in any position where they can detect the magnetic field generated by the first current value. For example, the magnetic sensors may be disposed on the surface of the circuit board opposite to the first semiconductor switch.

[0075] The magnetic sensor of the present disclosure does not need to include a Hall element, but only needs to be configured to be able to detect the magnetic field generated by the first current value.

[0076] In the first embodiment, the semiconductor switch 35 is an N-channel MOSFET, but the semiconductor switch may be a P-channel MOSFET. Also, the semiconductor switch may be other FETs.

[0077] The control unit that executes the open circuit fault diagnosis process of the present disclosure does not have to be provided inside the moving body.

[0078] 1: Energy storage device 2: Battery pack (energy storage element) 3: BMS (management device) 4A, 4B: Connection terminal 31: Control unit 32: Circuit breaker 33: Discharge cut-off unit (composite switch) 34: Charge cut-off unit (composite switch) 35, 35A, 35B, 35C, 35D, 35E, 35F: Semiconductor switch 37A, 37B: Magnetic sensor 38: Current sensor D1: First direction

Claims

1. An energy storage device comprising an energy storage element and a management device, wherein the management device comprises a circuit breaker that interrupts a current path between the energy storage element and a connection terminal for connecting the energy storage element to an external device, a control unit, and a magnetic sensor, wherein the circuit breaker includes a composite switch configured by connecting a plurality of semiconductor switches in parallel, one of the plurality of semiconductor switches being a first semiconductor switch, and the magnetic sensor is disposed near the first semiconductor switch or a conductive path connected to the first semiconductor switch and is not in electrical contact with the first semiconductor switch, and the control unit executes a current value acquisition process that acquires a first current value that is the value of a current flowing through the first semiconductor switch based on an input from the magnetic sensor, and a determination process that determines whether the acquired first current value is within a predetermined allowable range.

2. The energy storage device according to claim 1, wherein the plurality of semiconductor switches are arranged side by side in a first direction, and the first semiconductor switch is arranged at an end of the plurality of semiconductor switches in the first direction.

3. The power storage device according to claim 1, wherein the magnetic sensor includes a Hall element, and the input from the magnetic sensor is a numerical value related to a Hall voltage.

4. The energy storage device according to claim 1, wherein the allowable range is a range of values ​​that is assumed when none of the plurality of semiconductor switches has an open circuit failure.

5. The energy storage device according to any one of claims 1 to 4, wherein the control unit is configured to execute the current value acquisition process and the determination process multiple times at a predetermined timing, the determination process based on the result of the current value acquisition process when the current value flowing through the current path is equal to or greater than a predetermined first threshold value is a first determination process, and when the multiple executions of the determination process include the first determination process, the control unit diagnoses whether or not there is a failure in the composite switch based on the result of the first determination process.

6. The energy storage device according to claim 5, wherein the determination process based on the result of the current value acquisition process when the current value flowing through the current path is less than the first threshold value and equal to or greater than a predetermined second threshold value is a second determination process, and when the multiple determination processes do not include the first determination process, they include two or more consecutive second determination processes, and when the first current value is not within the allowable range in two consecutive second determination processes, the composite switch is diagnosed as faulty.

7. The power storage device according to claim 5, wherein the predetermined timing is when a mobile object equipped with the power storage device is in use or when charging of the power storage device begins.

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