Abnormality detection device and battery system

Abstract

The voltage measurement circuit measures the voltage of a plurality of cells connected in series. A plurality of input resistors are connected to each of the plurality of voltage measurement lines. A plurality of capacitors are connected between the lines. A plurality of discharge circuits are connected between the lines on the side closer to the voltage measurement circuit than the low-pass filter. The control circuit turns off a switch of a certain channel after the switch is turned on for a given time, and determines that an abnormality has occurred in a voltage measurement line connected to a positive electrode of a cell of the channel when the voltage of the channel does not return to a threshold voltage for a set time from the turn-off time.

Description

Technical Field

[0001] This disclosure relates to an anomaly detection device for detecting anomalies in voltage measuring lines connected to a battery pack, and to a battery system. Background Technology

[0002] For battery packs, from a safety perspective, voltage, temperature, and current are constantly monitored. Lithium-ion batteries, in particular, require strict voltage management due to the proximity of commonly used areas to prohibited use areas; voltage is measured / monitored on a cell-by-cell basis.

[0003] Patent Document 1 discloses the following method: In order to detect the breakage of the voltage measurement line connected to each cell constituting the battery pack, the balancing adjustment circuit for equalizing discharge of the target channel is activated to diagnose whether there is a suspected breakage, and the balancing adjustment circuit of the adjacent channel is further activated to determine the breakage (see reference). Figure 2 , Figure 3 ).like Figure 3 As shown, when the first voltage measuring line L1 is disconnected, the voltage of the channel of the first unit V1 decreases when the first discharge switch Qd1 is turned on. Subsequently, when the second discharge switch Qd2 is turned on, the voltage of the channel of the second unit V2 rises to approximately the total voltage of the first unit V1 and the second unit V2.

[0004] Prior art literature

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2009-89488 Summary of the Invention

[0007] In the above method, at least two balance adjustment circuits must be activated sequentially, which takes a considerable amount of time until the disconnection is confirmed. Furthermore, for the IC, which connects both the voltage measurement line and the balance adjustment input line, a large number of ports are required.

[0008] An anomaly detection device according to one aspect of this disclosure includes: a voltage measuring circuit connected to the positive terminals of a plurality of units connected in series via a plurality of voltage measuring lines, and connected to the negative terminal of the lowest-order unit among the plurality of units via a ground line, for measuring the voltage of each of the plurality of units; a plurality of input resistors connected to the plurality of voltage measuring lines; a plurality of capacitors connected between every two adjacent voltage measuring lines and between the voltage measuring line of the lowest-order unit and the ground line, and forming a low-pass filter with the plurality of input resistors; a plurality of discharge circuits connected between every two adjacent voltage measuring lines and between the voltage measuring line of the lowest-order unit and the ground line, respectively, closer to the voltage measuring circuit than the low-pass filter; and a control circuit that controls the plurality of discharge circuits based on the voltages of the plurality of units measured by the voltage measuring circuit, thereby performing equalization processing among the plurality of units. Each of the plurality of discharge circuits includes a discharge resistor and a switch connected in series. The control circuit turns off the switch of a certain channel after a given time from when the switch is turned on. If the voltage of the channel does not recover to the threshold voltage within a set time from when the switch is turned off, it determines that an abnormality has occurred in the voltage measurement line connected to the positive terminal of the unit of the channel among the plurality of voltage measurement lines.

[0009] According to this disclosure, it is possible to detect anomalies in voltage measurement lines in a short time while suppressing costs. Attached Figure Description

[0010] Figure 1 This is a diagram showing the overall structure of the battery system involved in the embodiment.

[0011] Figure 2 This is a diagram illustrating a specific structural example of the battery pack and analog front-end IC involved in the comparative example.

[0012] Figure 3 It is used for explanation Figure 2 A diagram showing the method for detecting a broken voltage measuring line in a circuit structure.

[0013] Figure 4 This is a diagram illustrating a specific structural example of the battery pack, analog front-end IC, and dual protection IC involved in the implementation method.

[0014] Figure 5 It is used for explanation Figure 4 A diagram showing the method for detecting a broken voltage measuring line in a circuit structure.

[0015] Figure 6 This is a schematic timing diagram illustrating a specific example 1 of a typical wire break detection method.

[0016] Figure 7 This is a schematic timing diagram of Example 1, which illustrates a method for detecting broken wires during unit balancing.

[0017] Figure 8 This is a schematic timing diagram illustrating a specific example 2 of a typical wire break detection method.

[0018] Figure 9 This is a schematic timing diagram of Example 2, which illustrates a method for detecting broken wires during unit balancing. Detailed Implementation

[0019] Figure 1 This is a diagram showing the overall structure of the battery system 1 according to the embodiment. The battery system 1 according to this embodiment is, for example, a system that can be used as a backup power system for a data center. The battery system 1 includes a battery pack 2 and an anomaly detection device 3.

[0020] Battery pack 2 comprises multiple cells connected in series. For each cell, lithium-ion battery cells, nickel-metal hydride battery cells, lead-acid battery cells, etc., can be used. Hereinafter, this specification presents an example using a lithium-ion battery cell (nominal voltage: 3.6-3.7V).

[0021] Battery pack 2 is connected to DC / DC converter 4. DC / DC converter 4 is connected to the commercial power system and the load via an inverter. DC / DC converter 4 can charge battery pack 2 with power input from the commercial power system via the inverter. At this time, DC / DC converter 4 can control the current or voltage to perform constant current charging or constant voltage charging. In addition, DC / DC converter 4 can supply power from battery pack 2 to the load via the inverter. In the case of DC load, power can be supplied without going through the inverter.

[0022] A disconnect switch is inserted into the power line connecting battery pack 2 and DC / DC converter 4. Figure 1 In the example shown, the first cut-off switch Q1 and the second cut-off switch Q2, both composed of N-channel MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors), are connected in reverse series to form a cut-off switch. In an N-channel MOSFET, a parasitic diode is formed from the source to the drain. By connecting two N-channel MOSFETs in reverse series, current flowing through the parasitic diode can be blocked, thus forming a bidirectional switch. Figure 1 In the example shown, by disconnecting the first disconnect switch Q1, the discharge current from the battery pack 2 can be cut off, and by disconnecting the second disconnect switch Q2, the charging current to the battery pack 2 can be cut off.

[0023] The anomaly detection device 3 has an analog front-end (AFC) IC10, a microcontroller (MCU) 20, and a dual protection IC30 as its main structural elements. The analog front-end IC10 measures / monitors the voltage of each cell in the battery pack 2, the current flowing through the battery pack 2, and the temperature of the battery pack 2, and sends the measured data to the microcontroller 20.

[0024] The analog front-end IC 10 includes an A / D converter 11. A current sensing element Rs is connected to the power line connecting the battery pack 2 and the DC / DC converter 4. For example, a shunt resistor can be used for the current sensing element Rs. The voltage across the shunt resistor is amplified by a differential amplifier and output as an analog voltage to the A / D converter 11. The A / D converter 11 converts the analog voltage representing the current flowing through the battery pack 2 from the differential amplifier input into a digital value and sends it to the microcontroller 20. Alternatively, a Hall element can be used instead of the shunt resistor and the differential amplifier.

[0025] At least one thermistor T1 is disposed on the surface of the battery pack 2. Thermistor T1 is a temperature-sensing element whose resistance changes with temperature. Specifically, for example, the voltage obtained by dividing the voltage of the power supply driving the microcontroller 20 and analog front-end IC 10 by thermistor T1 and voltage divider resistors is input to A / D converter 11. A / D converter 11 converts the input analog voltage representing the surface temperature of battery pack 2 into a digital value and sends it to microcontroller 20. Furthermore, it is preferable to provide thermistor T1 at multiple locations in battery pack 2. Alternatively, other temperature-sensing elements such as thermocouples or platinum resistance thermometers may be used instead of thermistor T1.

[0026] The A / D converter 11 is connected to the positive terminals of each of the multiple cells constituting the battery pack 2 via multiple voltage measurement lines. Additionally, the A / D converter 11 is connected to the negative terminal of the lowest-order cell constituting the battery pack 2 via a ground wire. The A / D converter 11 converts the analog voltages of each of the multiple cells constituting the battery pack 2 into digital values ​​and sends them to the microcontroller 20.

[0027] The microcontroller 20 includes a first communication unit 21, a charge / discharge control unit 22, and a second communication unit 23. The microcontroller 20 receives the voltage, current, and temperature of each cell in the battery pack 2 from the analog front-end IC 10 via the first communication unit 21. The microcontroller 20 can transmit the voltage, current, and temperature of each cell in the battery pack 2 as battery data to the host microcontroller 5 via the second communication unit 23.

[0028] The charge / discharge control unit 22 determines whether there is an overcharged or over-discharged cell based on the voltage of each cell of the battery pack 2 received from the analog front-end IC 10, determines whether there is an overcurrent based on the current of the battery pack 2, and determines whether there is an overtemperature based on the temperature of the battery pack 2.

[0029] In the event of overcharging, over-discharging, overcurrent, or overtemperature, the charge / discharge control unit 22 will turn off either the first cut-off switch Q1 or the second cut-off switch Q2 to protect the battery pack 2. Figure 1 The diagram illustrates a structure in which the gate voltages of the first cut-off switch Q1 and the second cut-off switch Q2 are controlled via an analog front-end IC 10. Alternatively, the gate voltages of the first cut-off switch Q1 and the second cut-off switch Q2 can also be controlled from the microcontroller 20 via a separate drive circuit.

[0030] Furthermore, in the event of at least one of overcharging, over-discharging, overcurrent, or overtemperature, the charge / discharge control unit 22 sends an abnormality detection signal to the host microcontroller 5 via the second communication unit 23. Upon receiving the abnormality detection signal from the microcontroller 20, the host microcontroller 5 stops the operation of the DC / DC converter 4. Additionally, in the event of overcharging, the charge / discharge control unit 22 can also directly stop the DC / DC converter 4 via an alarm signal line with diode D2 inserted.

[0031] In cases of abnormality in battery pack 2, overcharging can easily lead to early smoke / fire, posing a high urgency. From a fault protection perspective, the abnormality detection device 3 described in this embodiment includes a dual protection IC 30. The dual protection IC 30 monitors the voltage of each cell in battery pack 2, and if a cell exceeds the overcharge threshold, it directly stops the DC / DC converter 4 via an alarm signal line with diode D1 inserted. The alarm signal output from the dual protection IC 30 is also input to the microcontroller 20. When the alarm signal is input from the dual protection IC 30, the microcontroller 20 turns off either the first cut-off switch Q1 or the second cut-off switch Q2 and sends an overcharge stop signal to the upper-level microcontroller 5.

[0032] To suppress the random occurrence of hardware shutdowns caused by the dual protection IC30, the threshold voltage for overcharging determined by the dual protection IC30 is set higher than the threshold voltage for overcharging determined by the microcontroller 20.

[0033] Figure 2 This is a diagram illustrating a specific structural example of the battery pack 2 and the analog front-end IC 10 involved in the comparative example. Figure 2 The diagram shows an example of battery pack 2 consisting of first unit V1 to fourth unit V4 connected in series. A / D converter 11 is connected to the positive terminals of each of the first unit V1 to fourth unit V4 via first voltage measurement lines L1 to fourth voltage measurement lines L4, and is connected to the negative terminal of first unit V1 via ground line L0. A / D converter 11 measures the voltage of each of the four channels.

[0034] In voltage measurement lines L1 through L4, input resistors R1 through R4 are connected respectively. Input capacitors C1 through C4 are connected between every two adjacent voltage measurement lines and between voltage measurement line L1 and ground line L0. Input resistors R1 through R4 and input capacitors C1 through C4 constitute a low-pass filter to suppress aliasing.

[0035] Between every two adjacent voltage measurement lines and between the first voltage measurement line L1 and the ground line L0, four discharge circuits (hereinafter referred to as balance adjustment circuits) for equalization processing (hereinafter referred to as unit balancing) are connected respectively. Each balance adjustment circuit includes a first discharge resistor Rd1-a fourth discharge resistor Rd4 and a first discharge switch Qd1-a fourth discharge switch Qd4 connected in series.

[0036] For the first discharge switch Qd1 to the fourth discharge switch Qd4, semiconductor switches such as MOSFETs can be used. The first discharge switch Qd1 to the fourth discharge switch Qd4 are located within the analog front-end IC 10, and their on / off control is achieved through the charge / discharge control unit 22 of the microcontroller 20. The first discharge resistor Rd1 to the fourth discharge resistor Rd4 are located outside the analog front-end IC 10, and are connected to the first voltage measurement line L1 to the fourth voltage measurement line L4 at positions closer to the battery pack than the low-pass filter.

[0037] The A / D converter 11 monitors the voltage of each channel and performs both voltage measurement of each unit V1-V4 and disconnection diagnosis of each voltage measurement line L1-L4.

[0038] The charge / discharge control unit 22 of the microcontroller 20 controls the balancing circuit connected in parallel with each cell based on the voltages of the first cell V1 to the fourth cell V4 in the battery pack 2, as measured by the analog front-end IC 10. This enables cell balancing among the first cell V1 to the fourth cell V4. In a typical passive battery balancing method, other cells are discharged to the voltage of the cell with the lowest voltage among the multiple cells V1-V4 (hereinafter referred to as the target value). Furthermore, the target value can also be specified by capacity, state of charge (SOC), dischargeable amount, or rechargeable amount.

[0039] The charge / discharge control unit 22 sets the measured value of the unit with the lowest voltage among the multiple units V1-V4 as the target value, and calculates the difference between this target value and the measured values ​​of the other multiple units. Based on the calculated differences, the charge / discharge control unit 22 calculates the discharge amount of the other multiple units. Based on the calculated discharge amounts, the charge / discharge control unit 22 calculates the discharge time of the other multiple units. The charge / discharge control unit 22 generates a unit balance control signal that includes the discharge time of the multiple units and sends it to the analog front-end IC 10. Based on the control signal received from the charge / discharge control unit 22, the analog front-end IC 10 controls the multiple discharge switches Qd1-Qd4 to be in the conducting state for a specified time.

[0040] Figure 2 The circuit structure shown is suitable for large-capacity battery packs 2, such as those used in automotive applications. In large-capacity battery packs 2, even when a discharge current flows for cell balancing, the impact on the voltage of each cell is minimal. Therefore, voltage sampling of each cell can be performed during cell balancing. Since cell balancing in large-capacity battery packs 2 takes time, controls are often used to prevent the equalization discharge from stopping during voltage measurement timing.

[0041] Figure 3 It is used for explanation Figure 2 A diagram showing the method for detecting a broken voltage measuring line in a circuit structure. Figure 3 The example shown illustrates a situation where the first voltage measuring line L1 is broken. When diagnosing a break in the first voltage measuring line L1, the charge / discharge control unit 22 turns on the first discharge switch Qd1 of the first channel connected to the first unit V1. In the case of a broken first voltage measuring line L1, the voltage input to the first channel of the A / D converter 11 decreases. However, since the voltage of the first channel may also decrease due to reasons other than a broken first voltage measuring line L1, a break in the first voltage measuring line L1 cannot be determined at this stage.

[0042] When the voltage of the first channel decreases due to the first discharge switch Qd1 being turned on, the charge / discharge control unit 22 turns on the second discharge switch Qd2. If the first voltage measuring line L1 is disconnected, the voltage of the second channel, connected to the second unit V2, rises to approximately the total voltage of the first unit V1 and the second unit V2. If the first voltage measuring line L1 is not disconnected, the voltage of the second channel is measured as the voltage of the second unit V2. The charge / discharge control unit 22 determines that the first voltage measuring line L1 is disconnected when the voltage of the second channel rises to the voltage of the two series-connected units.

[0043] Thus, in the comparative example, a time difference needs to be set between the first discharge switch Qd1 and the second discharge switch Qd2 to activate them, which will take time for the disconnection diagnosis.

[0044] Figure 4 This diagram illustrates a specific structural example of the battery pack 2, the analog front-end IC 10, and the dual protection IC 30 involved in the embodiment. Figure 4 In China, for the sake of Figure 2 The same parts of the circuit shown are given the same reference number, and sometimes the description is omitted.

[0045] A voltage measuring line L1 is connected to the positive terminal of unit V1 via an input resistor R1. A voltage measuring line L2 is connected to the positive terminal of unit V2 via an input resistor R2. A voltage measuring line L3 is connected to the positive terminal of unit V3 via an input resistor R3. A voltage measuring line L4 is connected to the positive terminal of unit V4 via an input resistor R4.

[0046] Input resistors R1 through R4 are connected to voltage measurement lines L1 through L4, respectively. Input capacitors C1 through C4 are connected between two adjacent voltage measurement lines (i.e., between any two closely spaced upper and lower voltage measurement lines) and between voltage measurement line L1 and ground line L0, respectively. Input resistors R1 through R4 and input capacitors C1 through C4 form low-pass filters Lf1 through Lf4, suppressing aliasing.

[0047] Between two adjacent voltage measurement lines (i.e., between each pair of adjacent upper and lower voltage measurement lines) and between the first voltage measurement line L1 and the ground line L0, four discharge circuits Dh1-Dh4 (hereinafter referred to as balance adjustment circuits) are connected for equalization processing (hereinafter referred to as unit balancing). Discharge circuits Dh1-Dh4 respectively include first discharge resistors Rd1-Rd4 and first discharge switches Qd1-Qd4 connected in series.

[0048] For the first discharge switch Qd1 to the fourth discharge switch Qd4, semiconductor switches such as MOSFETs can be used. The first discharge switch Qd1 to the fourth discharge switch Qd4 are located in the analog front-end IC10, and their on / off control is performed by the charge / discharge control unit 22 of the microcontroller 20.

[0049] In this implementation, the first discharge switch Qd1 to the fourth discharge switch Qd4 and the first discharge resistor Rd1 to the fourth discharge resistor Rd4 are both located within the analog front-end IC10. The first discharge resistor Rd1 to the fourth discharge resistor Rd4 are respectively connected to the first voltage measurement line L1 to the fourth voltage measurement line L4 at a position closer to the A / D converter 11 than the low-pass filter.

[0050] A voltage measuring line L1 is connected to the positive terminal of unit V1 via an input resistor R1. A voltage measuring line L2 is connected to the positive terminal of unit V2 via an input resistor R2. A voltage measuring line L3 is connected to the positive terminal of unit V3 via an input resistor R3. A voltage measuring line L4 is connected to the positive terminal of unit V4 via an input resistor R4.

[0051] Unit V1 and voltage measuring line L1 connected to the positive terminal of unit V1 via input resistor R1 constitute the first channel. The first channel also has a first low-pass filter Lf1 composed of the first input resistor R1 and the first capacitor C1, and a first discharge circuit Dh1 composed of the first discharge switch Qd1 and the first discharge resistor Rd1 connected in series. Unit V2 and voltage measuring line L2 connected to the positive terminal of unit V2 via input resistor R2 constitute the second channel. The second channel also has a second low-pass filter Lf2 composed of the second input resistor R2 and the second capacitor C2, and a second discharge circuit Dh2 composed of the second discharge switch Qd2 and the second discharge resistor Rd2 connected in series. Unit V3 and voltage measuring line L3 connected to the positive terminal of unit V3 via input resistor R3 constitute the third channel. The third channel also includes a third low-pass filter Lf3 consisting of a third input resistor R3 and a third capacitor C3, and a third discharge circuit Dh3 consisting of a third discharge switch Qd3 and a third discharge resistor Rd3 connected in series. The fourth channel is formed by unit V4 and a voltage measurement line L4 connected to the positive terminal of unit V4 via an input resistor R4. The fourth channel also includes a fourth low-pass filter Lf4 consisting of a fourth input resistor R4 and a fourth capacitor C4, and a fourth discharge circuit Dh4 consisting of a fourth discharge switch Qd4 and a fourth discharge resistor Rd4 connected in series.

[0052] Multiple units V1-V4 are connected in series between ground line L0 and the voltage measuring line L4, which has the highest voltage, to form battery pack 2. The negative terminal of unit V1 is connected to ground line L0, and the positive terminal of unit V4 is connected to voltage measuring line L4. The negative and positive terminals of the series-connected units V1-V4 are connected in series between ground line L0 and voltage measuring line L4. Figure 2 , Figure 4The circuit contains units with different potentials. Among units V1-V4, unit V1, with the lowest potential, is the lowest-order unit. Unit V2 has a higher potential than unit V1, therefore unit V2 is the immediately adjacent upper-order unit of unit V1, and unit V1 is the immediately adjacent lower-order unit of unit V2. Similarly, unit V3 has a higher potential than unit V2, therefore unit V3 is the immediately adjacent upper-order unit of unit V2, and unit V2 is the immediately adjacent lower-order unit of unit V3. Unit V4 has a higher potential than unit V3, therefore unit V4 is the immediately adjacent upper-order unit of unit V3, and unit V3 is the immediately adjacent lower-order unit of unit V4. Among units V1-V4, unit V4, with the highest potential, is the highest-order unit. Based on the above, the channel containing unit V1 and voltage measurement line L1 is the lowest-order channel. The second channel, containing unit V2 and voltage measurement line L2, is the immediately adjacent upper-order channel of the first channel, which contains unit V1 and voltage measurement line L1, and the first channel is the immediately adjacent lower-order channel of the second channel. The third channel, which includes unit V3 and voltage measurement line L3, is the immediately adjacent upper channel of the second channel, and the second channel is the immediately adjacent lower channel of the third channel. The fourth channel, which includes unit V4 and voltage measurement line L4, is the immediately adjacent upper channel of the third channel, and the third channel is the immediately adjacent lower channel of the fourth channel. The fourth channel is the highest channel.

[0053] The dual protection IC30 is connected to the first branch voltage measurement line L1a-the fourth branch voltage measurement line L4a and the branch ground line L0a, which branch off from the first voltage measurement line L1-the fourth voltage measurement line L4a and the ground line L0, respectively, at a position closer to the battery pack side than the low-pass filter. The first branch voltage measurement line L1a-the fourth branch voltage measurement line L4a are connected to the first branch input resistor R1a-the fourth branch input resistor R4a respectively. Between every two adjacent branch voltage measurement lines, and between the first branch voltage measurement line L1a and the branch ground line L0a, the first branch input capacitor C1a-the fourth branch input capacitor C4a are connected respectively. The first branch input resistor R1a-the fourth branch input resistor R4a and the first branch input capacitor C1a-the fourth branch input capacitor C4a constitute a low-pass filter and suppress aliasing.

[0054] Within the dual protection IC 30, high-resistance detection resistors R31 to R34 are connected between every two adjacent branch voltage measurement lines and between the first branch voltage measurement line L1a and the branch ground line L0a. When any of the voltages across the first to fourth detection resistors R34 exceeds the overcharge threshold voltage, the dual protection IC 30 outputs an alarm signal. Thus, the dual protection IC 30 detects overcharge in units V1 to V4 by monitoring the voltages between every two adjacent voltage measurement lines and between the first voltage measurement line L1a and the ground line L0a.

[0055] Figure 5 It is used for explanation Figure 4 A diagram showing the method for detecting a broken voltage measuring line in a circuit structure. Figure 5 The example shown illustrates a situation where the first voltage measurement line L1 is broken. When diagnosing the breakage of the first voltage measurement line L1, the charge / discharge control unit 22 turns on the first discharge switch Qd1 of the first channel connected to the first unit V1. As a result, the voltage input to the first channel of the A / D converter 11 becomes a voltage divider voltage between the first input resistor R1 and the first discharge resistor Rd1, significantly reducing its voltage.

[0056] The charge / discharge control unit 22 turns off the first discharge switch Qd1 after a given time since it was turned on. The conduction time of the first discharge switch Qd1 is the time used to release the charge of the first input capacitor C1. Since it is only a short time (for example, about 1 msec), the effect on the capacity balance between the multiple cells V1-V4 can be ignored.

[0057] After the first discharge switch Qd1 is turned off, under normal conditions where the first voltage measurement line L1 is not disconnected, charge accumulates on the first input capacitor C1 via the first input resistor R1, resulting in a faster voltage recovery for the first channel. On the other hand, under abnormal conditions where the first voltage measurement line L1 is disconnected, charge accumulates on the first input capacitor C1 via the dual protection IC30, resulting in a slower voltage recovery for the first channel.

[0058] Figure 6 This is a schematic timing diagram illustrating a specific example 1 of a normal open circuit detection method. The charge / discharge control unit 22 performs an open circuit diagnosis of the first voltage measuring line L1 at a set time elapsed after the first discharge switch Qd1 is turned off. Under normal conditions, the voltage of the first channel exceeds the first judgment level (first threshold voltage), and under abnormal conditions, it falls below the first judgment level. If the voltage of the first channel does not recover to the judgment level within the set time from the turn-off of the first discharge switch Qd1, the charge / discharge control unit 22 determines that an abnormality such as an open circuit has occurred in the first voltage measuring line L1. Even if the first voltage measuring line L1 is not physically broken, it is still considered abnormal if it becomes unenergized.

[0059] For example, when the first input resistor R1 is set to 220Ω and the first discharge resistor Rd1 is set to 10Ω, after a timing interval of 1ms from when the first discharge switch Qd1 is turned off, the voltage of the first channel recovers to approximately 78% under normal conditions, but only to approximately 9.2% under abnormal conditions. For example, when the first judgment level for determining an abnormality is set to a value less than 60% (e.g., 2.2V) of the voltage measurement value before the first discharge switch Qd1 is turned on (e.g., 3.8V), an abnormality determination can be performed after a timing interval of at least 1ms from when the first discharge switch Qd1 is turned off.

[0060] In the simulation conducted by the inventors, the following results were obtained: the voltage of the target channel exceeded the first judgment level in about 0.55 ms when the connection was not broken, and did not exceed the first judgment level even after about 8 ms when the connection was broken. It was confirmed that if there is 1 ms, an anomaly can be determined.

[0061] The second and subsequent channels are also diagnosed for disconnection in the same way as the first channel. That is, the charge and discharge control unit 22 periodically sets the conduction period of the first discharge switch Qd1 to the fourth discharge switch Qd4 in sequence, and performs disconnection diagnosis based on the voltage action of the target channel after the discharge switch of the target channel is turned off.

[0062] Figure 7 This is a schematic timing diagram illustrating a specific example 1 of the method for detecting a broken wire during cell balancing. During cell balancing, the first discharge switch Qd1 through the fourth discharge switch Qd4 are essentially controlled to be in the on state. During cell balancing, the charge / discharge control unit 22 sets a periodic disconnection period for the first discharge switch Qd1 through the fourth discharge switch Qd4. The disconnection period is set to the aforementioned set time (1 msec) + α, that is, a time slightly longer than the set time.

[0063] The charge / discharge control unit 22 periodically sets the disconnection period for the first discharge switch Qd1 to the fourth discharge switch Qd4 in sequence. First, the charge / discharge control unit 22 performs a disconnection check on the first voltage measurement line L1 after a set time elapsed since the first discharge switch Qd1 was turned off. After the disconnection check, before turning the first discharge switch Qd1 back on, the charge / discharge control unit 22 measures the voltage of the first channel. Disconnection checks and voltage measurements are performed on the second and subsequent channels in the same manner as on the first channel.

[0064] In this way, during cell balancing, the charge / discharge control unit 22 periodically sets the disconnection period for the discharge switch of each channel to diagnose whether any abnormality has occurred in the voltage measurement line of that channel. During this disconnection period, the charge / discharge control unit 22 measures the voltage of that channel. Thus, disconnection diagnosis of each channel can also be performed during cell balancing. At this time, the balancing adjustment circuit stops, generating a period during which cell discharge stops, but this stop period is short (for example, about 1 msec), so the impact on the delay of cell balancing is minimized.

[0065] In the smaller capacity battery pack 2, the influence of the discharge current used for cell balancing on the variation of cell voltage needs to be considered. However, by utilizing the stop period of the balancing adjustment circuit during disconnection diagnosis, the voltage of each cell V1-V4 can be measured at a time when no discharge current flows. Therefore, the voltage of each cell V1-V4 can also be measured with high accuracy during cell balancing.

[0066] Figure 8 This is a schematic timing diagram illustrating a specific example 2 of a normal open circuit detection method. As described above, when the first discharge switch Qd1 is turned on, the voltage input to the first channel (voltage measurement line L1) of the A / D converter 11 becomes the voltage divided by the first input resistor R1 and the first discharge resistor Rd1, and decreases significantly. Simultaneously, the voltage of the adjacent upper channel (second voltage measurement line L2) of the first channel increases significantly.

[0067] When the first discharge switch Qd1 is turned off, under normal conditions where the first voltage measurement line L1 is not disconnected, charge accumulates on the first input capacitor C1 via the first input resistor R1, and the voltage of the first channel recovers to the voltage of the first unit V1 earlier. Simultaneously, the voltage of the second channel drops to the voltage of the second unit V2 earlier.

[0068] On the other hand, in the event of an anomaly where the first voltage measurement line L1 is disconnected, charge accumulates on the first input capacitor C1 via the dual protection IC30, resulting in a slower voltage recovery for the first channel. Consequently, the voltage of the second channel remains high.

[0069] The charge / discharge control unit 22 performs a time-lapse test on the first voltage measurement line L1 after a set time elapsed since the first discharge switch Qd1 was turned off. Under normal conditions, the voltage of the second channel is lower than the second judgment level (second threshold voltage), and under abnormal conditions, it exceeds the second judgment level. If the voltage of the second channel exceeds the second judgment level after a set time elapsed since the first discharge switch Qd1 was turned off, the charge / discharge control unit 22 determines that an abnormality such as a break in the first voltage measurement line L1 has occurred.

[0070] For example, when the first input resistor R1 is set to 220Ω and the first discharge resistor Rd1 is set to 10Ω, after a timing of 3ms from when the first discharge switch Qd1 is turned off, under normal conditions, the voltage of the second channel recovers to the voltage of the second unit V2, and under abnormal conditions, it rises to approximately 190% of the voltage of the second unit V2. For example, when the judgment level for determining an abnormality is set to a value greater than 160% of the voltage measurement value before the first discharge switch Qd1 is turned on (e.g., 3.8V) (e.g., 5.6V), an abnormality can be determined after a timing of at least 1ms from when the first discharge switch Qd1 is turned off.

[0071] In the simulation conducted by the inventors, the following results were obtained: the voltage of the upper adjacent channel of the target channel was always lower than the second judgment level when the line was not disconnected. However, when the voltage measurement line of the target channel was disconnected, it exceeded the second judgment level after about 0.45 ms from the turn-off of the first discharge switch Qd1. It was confirmed that if there was 1 ms, an anomaly judgment could be made.

[0072] The second and subsequent channels are also diagnosed for disconnection in the same way as the first channel. That is, the charge and discharge control unit 22 periodically sets the conduction period of the first discharge switch Qd1 to the fourth discharge switch Qd4 in sequence, and performs disconnection diagnosis based on the voltage action of the upper adjacent channel after the discharge switch of the target channel is turned off.

[0073] Figure 9 This is a schematic timing diagram of Example 2, used to illustrate a method for detecting broken wires during unit balancing. (and) Figure 7 Similarly, in the timing diagram of Specific Example 1 shown, during cell balancing, the charge / discharge control unit 22 periodically sets the discharge switch of each channel to an off period and diagnoses whether any abnormalities have occurred in the voltage measurement line of that channel. During this off period, the charge / discharge control unit 22 measures the voltage of that channel. At this time, the balancing adjustment circuit stops, creating a period during which cell discharge stops; however, this stopping period is short (e.g., about 1 msec), thus minimizing the impact on the delay of cell balancing.

[0074] exist Figure 4 In the circuit structure shown, after the discharge switch connected to the lower side of the voltage measurement line of the object being diagnosed, i.e., the discharge switch containing the channel of the voltage measurement line of the object, is turned off, the current for charge accumulation on the input capacitor connected to the lower side of the voltage measurement line is designed to be reduced to less than 1 / 10 of the current when the voltage measurement line is abnormal. The resistance values ​​of the first detection resistor R31 to the fourth detection resistor R34 in the dual protection IC30 are set to be more than 10 times the resistance values ​​of the first input resistor R1 to the fourth input resistor R4. For example, if the resistance values ​​of the first input resistor R1 to the fourth input resistor R4 are designed to be 220Ω, the resistance values ​​of the first detection resistor R31 to the fourth detection resistor R34 can also be set to 1MΩ or more.

[0075] exist Figure 1 , Figure 4The circuit structure shown can also be a structure that omits the dual protection IC 30. In this case, if the first voltage measurement line L1 is disconnected, when the first discharge switch Qd1 is turned off while the charge of the first input capacitor C1 is being released, the first input capacitor C1 is not charged via the dual protection IC 30, but rather by the leakage current of the second discharge switch Qd2 (MOSFET). Since the leakage current of the MOSFET is small, the time taken until the first input capacitor C1 is fully charged is further increased. Therefore, similar to the case where the dual protection IC 30 is provided, abnormality detection of the first voltage measurement line L1 can be performed.

[0076] As explained above, according to this embodiment, by monitoring the voltage behavior of the target channel or the adjacent channel after the discharge switch is turned off while the input capacitor has released its charge, abnormalities in the voltage measurement line can be detected in a short time while suppressing costs. Since no additional circuitry is required, no increase in hard costs is incurred.

[0077] exist Figure 2 In the circuit structure involved in the comparative example shown, the first discharge resistor Rd1 to the fourth discharge resistor Rd4 are located outside the analog front-end IC10. Conversely, in... Figure 4 In the circuit structure of the illustrated embodiment, the first discharge resistor Rd1 to the fourth discharge resistor Rd4 are located within the analog front-end IC10. Therefore, it is unnecessary to include a balance adjustment port in the analog front-end IC10. Figure 2 Compared to the circuit structure involved in the comparative example shown, the number of ports can be halved, and the analog front-end IC10 can be miniaturized.

[0078] Furthermore, since disconnection diagnosis can be performed in a short time, the impact of disconnection diagnosis on cell voltage is almost negligible. Diagnosis can also be performed during the charging and discharging of battery pack 2 and during cell balancing. The charging and discharging control unit 22 can periodically set the conduction period of the discharge switch regardless of whether battery pack 2 is charging, discharging, or idle, thereby diagnosing whether any abnormalities have occurred in the voltage measurement line.

[0079] The present disclosure has been described above based on the embodiments. The embodiments are illustrative, and those skilled in the art should understand that various modifications can be made to the combination of these constituent elements and processing procedures, and such modifications are also within the scope of the present disclosure.

[0080] In the above implementation, voltage measurement and disconnection diagnosis are performed by analog front-end IC10. However, an application-specific integrated circuit (ASIC) can also be used instead of analog front-end IC10 to perform voltage measurement and disconnection diagnosis.

[0081] In addition, the implementation method can also be determined by the following items.

[0082] [Project 1]

[0083] An anomaly detection device (3) comprises:

[0084] The voltage measuring circuit (11) is connected to the positive terminals of multiple units (V1-V4) connected in series through multiple voltage measuring lines (L1-L4), and is connected to the negative terminal of the lowest unit (V1) among the multiple units (V1-V4) through the ground line (L0), so as to measure the voltage of each of the multiple units (V1-V4).

[0085] Multiple input resistors (R1-R4) are respectively connected to the multiple voltage measurement lines (L1-L4);

[0086] Multiple capacitors (C1-C4) are respectively connected between every two adjacent voltage measurement lines among the multiple voltage measurement lines (L1-L4), and between the voltage measurement line (L1) of the lowest unit (V1) among the multiple voltage measurement lines (L1-L4) and the ground line (L0), and respectively form a low-pass filter with the multiple input resistors (R1-R4);

[0087] Multiple discharge circuits, located closer to the voltage measuring circuit (11) than the low-pass filter, are respectively connected between every two adjacent voltage measuring lines and between the voltage measuring line (L1) of the lowest unit (V1) and the ground line (L0); and

[0088] The control circuit (20), based on the voltages of the plurality of units (V1-V4) measured by the voltage measuring circuit (11), controls the plurality of discharge circuits, thereby performing equalization processing among the plurality of units (V1-V4).

[0089] The plurality of discharge circuits each include discharge resistors (Rd1-Rd4) and switches (Qd1-Qd4) connected in series.

[0090] The control circuit (20) turns off the switch of a certain channel after a given time from turning on the switch. If the voltage of the channel does not recover to the threshold voltage within a set time from the time of turning off, it determines that an abnormality has occurred in the voltage measurement line connected to the positive terminal of the unit of the channel in the plurality of voltage measurement lines (L1-L4) and the plurality of units (V1-V4).

[0091] Therefore, it is possible to detect anomalies in the voltage measurement line in a short time while suppressing costs.

[0092] [Project 2]

[0093] In the anomaly detection device (3) described in Project 1,

[0094] After the switch (Qd1-Qd4) connected to the lower side of the voltage measuring line of the object among the plurality of voltage measuring lines (L1-L4) is turned off, the current for charge accumulation on the capacitor (C1-C4) connected to the lower side of the voltage measuring line of the object is designed to be reduced to less than 1 / 10 of the current when the voltage measuring line of the object is normal in the event of an abnormality in the voltage measuring line of the object.

[0095] Therefore, depending on whether there is any abnormality in the voltage measurement line of the object, a large difference can be made in the rate at which charge accumulates on the capacitor after the switch is turned off.

[0096] [Project 3]

[0097] In the anomaly detection device (3) described in Project 2,

[0098] The anomaly detection device (3) further includes: a dual protection circuit (30) that monitors the voltage between every two adjacent voltage measurement lines and between the voltage measurement line (L1) of the lowest unit (V1) and the ground line (L0) on the side closer to the plurality of units (V1-V4) than the low-pass filter, thereby detecting overcharging.

[0099] The resistive component of the current path between the two ends of each unit (V1-V4) of the dual protection circuit (30) is designed to be more than 10 times the resistance value of the input resistance (R1-R4).

[0100] Therefore, depending on whether there is any abnormality in the voltage measurement line of the object, the voltage behavior measured after the switch is turned off can produce a large difference.

[0101] [Project 4]

[0102] In the anomaly detection device (3) described in Project 1,

[0103] During the execution of the equalization process, the control circuit (20) periodically sets the switch to an open period to diagnose whether an abnormality has occurred in the voltage measurement line of the channel corresponding to the switch among the plurality of voltage measurement lines (L1-L4).

[0104] Therefore, abnormality diagnosis of voltage measurement lines can also be performed during the equalization process.

[0105] [Project 5]

[0106] In the anomaly detection device (3) described in Project 1,

[0107] The control circuit (20) measures the voltage of the channel corresponding to the switch during the period when the switch is open.

[0108] Therefore, even when the cell capacity is small, the cell voltage can be measured with high accuracy during the equalization process.

[0109] [Project 6]

[0110] In the anomaly detection device (3) described in Project 1,

[0111] The control circuit (20) periodically sets the conduction period of the switch, regardless of whether the plurality of units (V1-V4) are charging, discharging or resting, in order to diagnose whether an abnormality has occurred in the voltage measurement line.

[0112] Therefore, it is possible to diagnose abnormalities in the voltage measurement line regardless of the charging / discharging state.

[0113] [Project 7]

[0114] A battery system (1) comprising:

[0115] Battery pack (2), comprising multiple cells (V1-V4) connected in series; and

[0116] The anomaly detection device (3) described in any one of items 1 to 6.

[0117] Therefore, it is possible to construct a battery system that can detect anomalies in the voltage measurement line in a short time while suppressing costs.

[0118] -Symbol Explanation-

[0119] 1 Battery System

[0120] 2 Battery Packs

[0121] 3 Anomaly Detection Device

[0122] 4 DC / DC converters

[0123] 5. Host Microcontroller

[0124] 10 Analog Front-End ICs

[0125] 11 A / D converter

[0126] 20 microcontrollers

[0127] 21 1st Communications Department

[0128] 22 Charge / Discharge Control Unit

[0129] 23 2nd Communications Department

[0130] 30 Dual Protection ICs

[0131] V1-V4 units

[0132] L0 ground wire

[0133] L1-L4 Voltage Measurement Line

[0134] Input resistors R1-R4

[0135] Input capacitors C1-C4

[0136] Discharge resistors Rd1-Rd4

[0137] Qd1-Qd4 Discharge Switches

[0138] L0a Branch Ground

[0139] L1a-L4a Branch Voltage Measurement Line

[0140] Branch input resistors R1a-R4a

[0141] C1a-C4a Branch Input Capacitors

[0142] R31-R34 probe resistors

[0143] D1-D2 diodes

[0144] Q1-Q2 Disconnect Switch

[0145] T1 Thermistor

[0146] Rs Current sensing element.

Claims

1. An anomaly detection device, comprising: The voltage measuring circuit is connected to the positive terminals of multiple units connected in series via multiple voltage measuring lines, and to the negative terminal of the lowest unit among the multiple units via a ground line, so as to measure the voltage of each of the multiple units. Multiple input resistors are connected to the multiple voltage measurement lines, respectively; Multiple capacitors are respectively connected between every two adjacent voltage measurement lines among the multiple voltage measurement lines, and between the voltage measurement line of the lowest unit among the multiple voltage measurement lines and the ground line, and respectively form a low-pass filter with the multiple input resistors. Multiple discharge circuits are respectively connected between every two adjacent voltage measurement lines and between the voltage measurement line of the lowest unit and the ground line, on the side closer to the voltage measurement circuit than the low-pass filter. and The control circuit, based on the voltages of the plurality of units measured by the voltage measuring circuit, controls the plurality of discharge circuits, thereby performing equalization processing among the plurality of units. The plurality of discharge circuits each include a discharge resistor and a switch connected in series. The control circuit turns off the switch of a certain channel after a given time from when the switch is turned on. If the voltage of the channel does not recover to the threshold voltage within a set time from when the switch is turned off, it determines that an abnormality has occurred in the voltage measurement line connected to the positive terminal of the unit of the channel among the plurality of voltage measurement lines.

2. The anomaly detection device according to claim 1, wherein, When the switch connected to the lower side of the voltage measuring line of one of the plurality of voltage measuring lines is turned off, the current for charge accumulation on the capacitor connected to the lower side of the voltage measuring line of the object is designed to be reduced to less than 1 / 10 of the current when the voltage measuring line of the object is normal in the event of an abnormality in the voltage measuring line of the object.

3. The anomaly detection device according to claim 2, wherein, The anomaly detection device also includes a dual protection circuit, which monitors the voltage between every two adjacent voltage measurement lines and between the voltage measurement line of the lowest unit and the ground line, respectively, on the side closer to the plurality of units than the low-pass filter, thereby detecting overcharging. The resistive component of the current path between the two ends of each unit of the dual protection circuit is designed to be more than 10 times the resistance of the input resistance.

4. The anomaly detection device according to claim 1, wherein, During the execution of the equalization process, the control circuit periodically sets the switch to an open period to diagnose whether any abnormality has occurred in the voltage measurement line of the channel corresponding to the switch among the plurality of voltage measurement lines.

5. The anomaly detection device according to claim 1, wherein, The control circuit measures the voltage of the channel corresponding to the switch during the period when the switch is open.

6. The anomaly detection device according to claim 1, wherein, The control circuit, regardless of whether the plurality of units are charging, discharging or resting, periodically sets the on period of the switch to diagnose whether any abnormality has occurred in the voltage measurement line.

7. A battery system comprising: A battery pack, comprising multiple cells connected in series; and The anomaly detection device according to any one of claims 1 to 6.

Images