Voltage detection device

Abstract

To provide a voltage detection device capable of suppressing a decrease in compensation accuracy for the temperature characteristics of path resistance values when a temperature sensor fails.SOLUTION: The voltage detection device for detecting cell voltages of a battery pack via predetermined voltage detection lines includes multiple temperature sensors that detect the temperature of the voltage detection lines as detection line temperatures, a correction temperature setting unit that sets the average of the detection line temperatures as a correction temperature when the detection temperature difference among the detection line temperatures exceeds a predetermined threshold, and a correction temperature acquisition unit that obtains corrected cell voltages by correcting the cell voltages on the basis of the correction temperature.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a voltage detection device. [Background technology]

[0002] The following Patent Document 1 discloses a fault detection technique that reliably detects faults in a temperature sensor provided in a battery system including a secondary battery. This fault detection technique periodically acquires temperature measurements from a temperature sensor to determine the rate of change over time of the temperature measurements, and detects faults based on this rate of change. Specifically, the temperature sensor is determined to have failed when the measured temperature deviates from a predetermined temperature range and the rate of change over time of the measured temperature exceeds a predetermined threshold. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-325110 Summary of the Invention [Problem to be solved by the invention]

[0004] In order to improve the accuracy of detecting the cell voltage of a secondary battery in a battery system, it is necessary to cancel the temperature characteristic of the resistance value (path resistance value) of the voltage detection line connected to the secondary battery. In this case, the temperature characteristic is canceled based on the temperature of the voltage detection line detected by a temperature sensor, but if the temperature sensor fails due to temperature drift, the accuracy of canceling the temperature characteristic cannot be ensured.

[0005] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a voltage detection device that can suppress a decrease in the compensation accuracy of the temperature characteristics of the path resistance value when the temperature sensor fails. [Means for solving the problem]

[0006] In order to achieve the above object, the present invention adopts, as a first solution related to a voltage detection device, a voltage detection device that detects the cell voltage of a battery pack via a specified voltage detection line, and is equipped with a plurality of temperature sensors that detect the temperature of the voltage detection line as a detection line temperature, a correction temperature setting unit that sets the average value of the detection line temperatures to a correction temperature when the detected temperature difference of the detection line temperatures exceeds a specified threshold value, and a correction temperature acquisition unit that acquires a corrected cell voltage by correcting the cell voltage based on the correction temperature.

[0007] In the present invention, as a second solution related to the voltage detection device, in the above-mentioned first solution, the correction temperature setting unit adopts a means for setting the correction temperature to the average value of the detection values ​​of a plurality of temperature sensors that are not abnormal among the plurality of temperature sensors.

[0008] The present invention employs, as a third solution related to the voltage detection device, the solution of the first or second solution, in which the temperature sensor is provided corresponding to the battery module that constitutes the battery pack. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a voltage detection device that can suppress a decrease in the accuracy of compensation for the temperature characteristics of the path resistance value when the temperature sensor fails. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a circuit diagram showing a configuration of a voltage detection device according to an embodiment of the present invention; [Figure 2] 3 is a first flowchart showing the operation of the voltage detection device according to one embodiment of the present invention. [Figure 3] 3A and 3B are schematic diagrams illustrating the operation of a voltage detection device according to an embodiment of the present invention. [Figure 4] 6 is a second flowchart showing the operation of the voltage detection device according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 1, a voltage detection device A according to this embodiment is an on-board device that detects a battery pack B and is mounted on a vehicle together with the battery pack B. As shown in the figure, the voltage detection device A includes a plurality of voltage detection lines L, three LiB-ICs 1a to 1c, an insulating element 2, a communication IC 3, three thermistors TH1 to TH3, six resistors R1a, R1b, R2a, R2b, R3a, and R3b, three capacitors C1 to C3, and an MPU 4.

[0012] The battery pack B is made up of three battery modules b1 to b3 connected in series, and supplies DC power to a load in the vehicle. Each of the three battery modules b1 to b3 has a predetermined output voltage (module voltage). That is, the output voltage (battery voltage) of the battery pack B is the sum of the module voltages of the three battery modules b1 to b3.

[0013] Each of the three battery modules b1 to b3 includes multiple battery cells. That is, each of the three battery modules b1 to b3 has multiple battery cells connected in series. That is, the module voltage V1 of the first battery module b1 is the total voltage of the output voltages (cell voltages) of the multiple battery cells.

[0014] The module voltage V2 of the second battery module b2 is the sum of the output voltages (cell voltages) of the multiple battery cells, and the module voltage V3 of the third battery module b3 is the sum of the output voltages (cell voltages) of the multiple battery cells.

[0015] In the voltage detection device A, the voltage detection lines L are electric wires that connect the electrodes of the battery cells in the three battery modules b1 to b3 to the input terminals of the three LiB-ICs 1a to 1c. That is, one end of each of the voltage detection lines L is connected to the electrodes of the battery cells, and the other end is connected to the input terminals of the three LiB-ICs 1a to 1c.

[0016] The voltage detection lines L have a path resistance value that is temperature dependent. That is, when the temperature of the voltage detection lines L changes, the path resistance value of the voltage detection lines L changes in accordance with the amount of temperature change.

[0017] In the voltage detection device A, the three LiB-ICs 1a to 1c are provided corresponding to the three battery modules b1 to b3 in the battery pack B. Although not shown in FIG. 1, the three LiB-ICs 1a to 1c are interconnected so as to be able to communicate freely.

[0018] The first LiB-IC1a is provided corresponding to the first battery module b1, and has a plurality of input terminals connected to a plurality of electrodes in the first battery module b1 via a plurality of voltage detection lines L. The first LiB-IC1a detects cell voltages V1 of a plurality of battery cells in the first battery module b1 based on the electrode voltages in the first battery module b1 input to a pair of input terminals, and transmits the cell voltages V1 to the MPU 4 via the isolation element 2, the communication IC 3, etc.

[0019] The second LiB-IC1b is provided corresponding to the second battery module b2, and a pair of input terminals are connected to a pair of electrodes in the second battery module b2 via a plurality of voltage detection lines L. This second LiB-IC1b detects cell voltages V2 of the plurality of battery cells in the second battery module b2 based on the electrode voltages in the second battery module b2 input to the pair of input terminals, and transmits the plurality of cell voltages V2 to the MPU 4 via the isolation element 2, the communication IC 3, etc.

[0020] The third LiB-IC1c is provided corresponding to the third battery module b3, and a pair of input terminals are connected to a pair of electrodes in the third battery module b3 via a plurality of voltage detection lines L. This third LiB-IC1c detects cell voltages V3 of the plurality of battery cells in the third battery module b3 based on the electrode voltages in the third battery module b3 input to the pair of input terminals, and transmits the plurality of cell voltages V3 to the MPU4 via the isolation element 2, communication IC3, etc.

[0021] The insulating element 2 is an electronic element for avoiding electrical interference between the three LiB-ICs 1a to 1c and the communication IC 3, and a pair of first input / output terminals is connected to a pair of input / output terminals in the third LiB-IC 1c, and a pair of second input / output terminals is connected to a pair of first input / output terminals in the communication IC 3.

[0022] The power supply voltages of the power supply systems (high-voltage power supply systems) of the three LiB-ICs 1a to 1c are different from those of the power supply systems (low-voltage power supply systems) of the communication IC 3 and MPU 4. As shown in the figure, the low-voltage power supply system has a power supply voltage of 5V, whereas the high-voltage power supply system has a power supply voltage exceeding 5V.

[0023] To prevent electrical interference between the low-voltage power supply system and the high-voltage power supply system, the isolation element 2 prevents a direct current connection of signals transmitted and received between the three LiB-ICs 1a to 1c and the communication IC 3. Such an isolation element 2 is, for example, an optical coupler or a pulse transformer.

[0024] The communication IC 3 has a pair of first input / output terminals connected to a pair of second input / output terminals in the isolation element 2, and four second input / output terminals connected to four input / output terminals in the MPU 4. This communication IC 3 is an integrated circuit (IC) that mediates communication between the three LiB-ICs 1a to 1c and the MPU 4.

[0025] That is, the communication IC 3 performs wired communication with the three LiB-ICs 1a to 1c in accordance with a predetermined communication protocol, and transmits and receives signals with the MPU 4 in accordance with a communication protocol that is different from the above-mentioned communication protocol.

[0026] For example, communication signals of a plurality of cell voltages V1 to V3 input from three LiB-ICs 1a to 1c to a communication IC 3 via an insulating element 2 are converted into communication signals of different formats in the communication IC 3 and output to an MPU 4.

[0027] Three thermistors TH1 to TH3 are provided corresponding to three battery modules b1 to b3. These three thermistors TH1 to TH3 detect the temperatures (module temperatures) of the three battery modules b1 to b3 as substitute temperatures of the voltage detection lines L connected thereto. In other words, the three thermistors TH1 to TH3 are multiple temperature sensors that detect the temperatures of the voltage detection lines L as detection line temperatures.

[0028] The first thermistor TH1 is provided corresponding to the first battery module b1, and has one end grounded and the other end connected to one end of the first resistor R1a and one end of the second resistor R1b. The first thermistor TH1 detects the temperature of the first battery module b1 as a first detection line temperature T1 and outputs a first temperature detection signal indicating the first detection line temperature T1 to one end of the first resistor R1a and one end of the second resistor R1b.

[0029] The second thermistor TH2 is provided corresponding to the second battery module b2, and has one end grounded and the other end connected to one end of the third resistor R2a and one end of the fourth resistor R2b. The second thermistor TH2 detects the temperature of the second battery module b2 as a second detection line temperature T2 and outputs a second temperature detection signal indicating the second detection line temperature T2 to one end of the third resistor R2a and one end of the fourth resistor R2b.

[0030] The third thermistor TH3 is provided corresponding to the third battery module b3, has one end grounded, and the other end connected to one end of the fifth resistor R3a and one end of the sixth resistor R3b, detects the temperature of the third battery module b3 as a third detection line temperature T3, and outputs a third temperature detection signal indicating the third detection line temperature T3 to one end of the fifth resistor R3a and one end of the sixth resistor R3b.

[0031] Of the six resistors R1a, R1b, R2a, R2b, R3a, and R3b, the first resistor R1a, the third resistor R2a, and the fifth resistor R3a, together with the three capacitors C1 to C3, form three low-pass filters.

[0032] That is, the first resistor R1a has a predetermined resistance value (first resistance value) and constitutes a first low-pass filter together with the first capacitor C1. One end of the first resistor R1a is connected to the other end (output end) of the first thermistor TH1 and one end of the second resistor R1b, and the other end is connected to one end of the first capacitor C1 and the first input end AD1 of the MPU4.

[0033] The third resistor R2a has a predetermined resistance value (third resistance value) and constitutes a second low-pass filter together with the second capacitor C2. One end of the third resistor R2a is connected to the other end (output end) of the second thermistor TH2 and one end of the fourth resistor R2b, and the other end is connected to one end of the second capacitor C2 and the second input end AD2 of the MPU4.

[0034] Furthermore, the fifth resistor R3a has a predetermined resistance value (fifth resistance value) and constitutes a third low-pass filter together with the third capacitor C3. One end of the fifth resistor R3a is connected to the other end (output end) of the third thermistor TH3 and one end of the sixth resistor R3b, and the other end is connected to one end of the third capacitor C3 and the third input end AD3 of the MPU4.

[0035] Of the six resistors R1a, R1b, R2a, R2b, R3a, and R3b, the second resistor R1b, the fourth resistor R2b, and the sixth resistor R3b are pull-up resistors. That is, the second resistor R1b has a predetermined resistance value (second resistance value), one end of which is connected to the other end (output end) of the first thermistor TH1 and one end of the first resistor R1a, and the other end of which is connected to a low-voltage power supply (5V).

[0036] The fourth resistor R2b has a predetermined resistance value (fourth resistance value), one end is connected to the other end (output end) of the second thermistor TH2 and one end of the third resistor R2a, and the other end is connected to the low-voltage power supply (5 V). The sixth resistor R3b has a predetermined resistance value (sixth resistance value), one end is connected to the other end (output end) of the third thermistor TH3 and one end of the fifth resistor R3a, and the other end is connected to the low-voltage power supply (5 V).

[0037] The three capacitors C1 to C3, along with the first resistor R1a, the third resistor R2a, and the fifth resistor R3a, form three low-pass filters. One end of the first capacitor C1 is connected to the other end of the first resistor R1a and the first input terminal AD1 of the MPU 4, and the other end is grounded. The first capacitor C1 has a predetermined capacitance (first capacitance) and forms a first low-pass filter together with the first resistor R1a.

[0038] One end of the second capacitor C2 is connected to the other end of the third resistor R2a and the second input terminal AD2 of the MPU 4, and the other end is grounded. The second capacitor C2 has a predetermined capacitance (second capacitance) and constitutes a second low-pass filter together with the third resistor R2a.

[0039] One end of the third capacitor C3 is connected to the other end of the fifth resistor R3a and the third input terminal AD3 of the MPU 4, and the other end is grounded. The third capacitor C3 has a predetermined capacitance (third capacitance) and constitutes a third low-pass filter together with the fifth resistor R3a.

[0040] The MPU 4 has at least four input / output terminals and first to third input terminals AD1 to AD3. The four input / output terminals of the MPU 4 are connected to the four second input / output terminals of the communication IC 3. The first input terminal AD1 of the MPU 4 is connected to the other end of the first resistor R1a and one end of the first capacitor C1, the second input terminal AD2 is connected to the other end of the third resistor R2a and one end of the second capacitor C2, and the third input terminal AD3 is connected to the other end of the fifth resistor R3a and one end of the third capacitor C3.

[0041] 1, the MPU 4 is also provided with a communication terminal for transmitting and receiving signals to and from an external device such as a higher-level control device. That is, the MPU 4 transmits and receives information by communicating with the external device using the communication terminal.

[0042] The MPU 4 is an integrated circuit that executes predetermined information processing (temperature correction processing) based on a pre-stored program. That is, the MPU 4 performs temperature correction processing on the plurality of cell voltages V1-V3 based on the first to third detection line temperatures T1-T3, thereby obtaining a plurality of corrected cell voltages V1h-V3h that have been temperature-corrected by the first to third detection line temperatures T1-T3.

[0043] The temperature correction process will be described in detail later, but the MPU 4 functions as a correction temperature setting unit and a correction temperature acquisition unit in the present invention. That is, when the detected temperature difference between the multiple detected line temperatures T1 to T3 exceeds a predetermined threshold value Rt, the MPU 4 sets the average value of the multiple detected line temperatures T1 to T3 as a correction temperature Th, and corrects the cell voltages V1 to V3 based on the correction temperature Th to obtain corrected cell voltages V1h to V3h.

[0044] Next, the operation (temperature correction process) of the voltage detecting device A according to this embodiment will be described in detail with reference to the flowchart shown in FIG.

[0045] In this voltage detection device A, when the vehicle ignition switch (IG) is set to "ON" (step S1), the three LiB-ICs 1a to 1c detect cell voltages V1 to V3 of multiple battery cells in the battery pack B (step S2). These cell voltages V1 to V3 are then transmitted from the LiB-ICs 1a to 1c to the MPU 4 via the isolation element 2 and the communication IC 3.

[0046] Then, the MPU 4 determines whether the cell voltages V1 to V3 are within the normal voltage range (step S3). If the determination in step S3 is "Yes," that is, if the cell voltages V1 to V3 are normal, the MPU 4 acquires the three detected line temperatures T1 to T3 (step S4). Then, the MPU 4 calculates the mutual temperature differences among the three detected line temperatures T1 to T3 (step S5).

[0047] Specifically, the MPU 4 calculates three temperature differences ΔT12, ΔT23, and ΔT31 based on the following arithmetic expressions (1) to (3). ΔT12=|T1-T2| (1) ΔT23=|T2-T3| (2) ΔT31=|T3-T1| (3)

[0048] Then, the MPU4 determines whether the three temperature differences ΔT12, ΔT23, and ΔT31 are normal (step S6). That is, the MPU4 compares the three temperature differences ΔT12, ΔT23, and ΔT31 with a pre-stored temperature difference threshold Rt to evaluate the normality of the three temperature differences ΔT12, ΔT23, and ΔT31, i.e., the health of the three thermistors TH1 to TH3 (temperature sensors).

[0049] Here, if all three thermistors TH1 to TH3 are normal, the three detection line temperatures T1 to T3 will be close to each other, and the three temperature differences ΔT12, ΔT23, and ΔT31 will be smaller than the temperature difference threshold value Rt. Therefore, the determination in step S6 will be "No." On the other hand, if any one of the three thermistors TH1 to TH3 is abnormal, any two of the three temperature differences ΔT12, ΔT23, and ΔT31 will be larger than the temperature difference threshold value Rt.

[0050] If the determination in step S6 is "Yes," that is, if at least one of the three temperature differences ΔT12, ΔT23, and ΔT31 is greater than the temperature difference threshold value Rt, the MPU 4 determines whether two or more of the three temperature differences ΔT12, ΔT23, and ΔT31 are greater than the temperature difference threshold value Rt (step S7). If the determination in step S6 is "No," the MPU 4 repeats the processing of step S4.

[0051] As described above, if any one of the three thermistors TH1 to TH3 is abnormal, any two of the three temperature differences ΔT12, ΔT23, and ΔT31 will be greater than the temperature difference threshold value Rt, so if any one of the three thermistors TH1 to TH3 is abnormal, the judgment in step S7 will be "Yes."

[0052] If the determination in step S7 is "Yes," the MPU 4 identifies the abnormal thermistor (abnormal temperature sensor) (step S8). For example, if the second thermistor TH2 of the three thermistors TH1 to TH3 is the abnormal thermistor, then, as shown in the following equations (4) to (63), of the three temperature differences ΔT12, ΔT23, and ΔT31, two temperature differences ΔT12 and ΔT23 will be greater than the temperature difference threshold value Rt, and the remaining temperature difference ΔT31 will be smaller than the temperature difference threshold value Rt.

[0053] ΔT12>Rt (4) ΔT23>Rt (5) ΔT31 <Rt (6)

[0054] That is, the two temperature differences ΔT12 and ΔT23 related to the temperature detection value (detection line temperature T2) of the abnormal thermistor (second thermistor TH2) are greater than the temperature difference threshold value Rt. As shown in Figure 3, the MPU 4 identifies the abnormal thermistor (abnormal temperature sensor) based on the results of comparing the three temperature differences ΔT12, ΔT23, and ΔT31 with the temperature difference threshold value Rt.

[0055] Then, the MPU 4 sets the average (average temperature) of the temperature detection values ​​of the normal thermistors excluding the temperature detection values ​​of the abnormal thermistors as the correction temperature, and uses this average temperature to temperature-correct the multiple cell voltages V1-V3 (step S9). That is, the MPU 4 obtains multiple corrected cell voltages V1h-V3h by temperature-correcting the multiple cell voltages V1-V3 using the average temperature.

[0056] For example, if the second thermistor TH2 is an abnormal thermistor, the MPU 4 calculates the average temperature T13 of the first and third detection line temperatures T1 to T3, and performs temperature correction on the multiple cell voltages V1 to V3 using the average temperature T13. As a result, the MPU 4 obtains multiple corrected cell voltages V1h to V3h.

[0057] On the other hand, if the determination in step S3 is "No," there is a concern that abnormal heat may be generated in the battery cells constituting the three battery modules b1 to b3, so the MPU 4 masks the abnormality detection process for the three thermistors TH1 to TH3 (step S10).Then, the MPU 4 sets the equalization process for the battery cells constituting the three battery modules b1 to b3 to the "OFF" state (step S11).

[0058] That is, if the determination in step S3 is "No," the MPU 4 omits the abnormality detection (fault diagnosis) for the three thermistors TH1 to TH3. Also, if the determination in step S3 is "No," the MPU 4 does not omit the equalization process for equalizing the cell voltages of multiple battery cells.

[0059] Furthermore, if the determination in step S7 described above is "No," that is, if one of the three temperature differences ΔT12, ΔT23, and ΔT31 is greater than the temperature difference threshold value Rt, the MPU4 performs temperature correction on the multiple cell voltages V1 to V3 using the temperature detection value (normal temperature) of one normal thermistor (step S12).

[0060] The voltage detection device A of this embodiment detects the cell voltage of a battery pack B via a predetermined voltage detection line L, and is equipped with a plurality of thermistors TH1 to TH3 (temperature sensors) that detect the temperature of the voltage detection line L as detection line temperatures T1 to T3, an MPU4 (correction temperature setting unit) that sets the average value T13 of the detection line temperatures T1 and T3 as a correction temperature when the temperature difference ΔT12, ΔT23, ΔT31 of the detection line temperature L exceeds a predetermined temperature difference threshold Rt, and an MPU4 (correction temperature acquisition unit) that acquires corrected cell voltages V1h to V3h by correcting the cell voltages V1 to V3 based on the correction temperature.

[0061] According to this embodiment, it is possible to correct the cell voltages V1 to V3 even if any of the multiple thermistors TH1 to TH3 (temperature sensors) fails, so it is possible to provide a voltage detection device A that can suppress a decrease in the compensation accuracy of the temperature characteristics of the path resistance value when multiple thermistors TH1 to TH3 (temperature sensors) fail.

[0062] Furthermore, in the voltage detection device A according to this embodiment, the MPU4 (correction temperature setting unit) sets the correction temperature to the average (average temperature) of the detected values ​​of the plurality of temperature sensors that are not abnormal among the plurality of thermistors TH1 to TH3 (temperature sensors). According to this embodiment, the temperature detected values ​​of the abnormal temperature sensors are excluded from the calculation of the average temperature, which further reduces the deterioration of the compensation accuracy of the temperature characteristic of the path resistance value.

[0063] Furthermore, in the voltage detection device A according to this embodiment, the multiple thermistors TH1 to TH3 (temperature sensors) are provided corresponding to the multiple battery modules b1 to b3 that constitute the battery pack B. According to this embodiment, of the multiple voltage detection lines L, the detection line temperatures T1 to T3 can be obtained for each of the battery modules b1 to b3, which further reduces the deterioration in the compensation accuracy for the temperature characteristics of the path resistance value.

[0064] The temperature correction process of the voltage detection device A may be modified as shown in the flowchart of Fig. 4. In Fig. 3, the same steps as those in the temperature correction process of Fig. 2 are denoted by the same reference numerals.

[0065] 3, the temperature correction process according to the modified example involves performing steps S13 and S14 between steps S4 and 5. That is, after acquiring the three detection line temperatures T1 to T3, the MPU 4 determines whether a certain time has elapsed (step S13). If the determination in step S13 is "Yes," the MPU 4 then calculates the average temperature and correction coefficient (step S14).

[0066] In this modified example, the three temperature differences ΔT12, ΔT23, and ΔT31 are obtained after a certain time has elapsed since the vehicle's ignition switch (IG) was set to "ON," thereby improving the accuracy of abnormality detection (fault diagnosis) for the three thermistors TH1 to TH3. [Explanation of symbols]

[0067] A Voltage detection device B Battery pack b1~b Battery modules C1~C3 capacitors L Voltage detection wire R1a, R1b, R2a, R2b, R3a, R3b resistor TH1~TH3 thermistors 1a~1c LiB-IC 2. Isolation element 3. Communication IC 4 MPU4

Claims

1. A voltage detection device that detects cell voltages of a battery pack via a predetermined voltage detection line, a plurality of temperature sensors that detect temperatures of the voltage detection lines as detection line temperatures; a correction temperature setting unit that sets an average value of the detected line temperatures as a correction temperature when the detected temperature difference of the detected line temperatures exceeds a predetermined threshold value; a correction temperature acquisition unit that acquires a corrected cell voltage by correcting the cell voltage based on the correction temperature; A voltage detection device comprising:

2. 2. The voltage detection device according to claim 1, wherein the correction temperature setting unit sets the correction temperature to an average value of detected values ​​from a plurality of temperature sensors that are not abnormal, among the plurality of temperature sensors.

3. 3. The voltage detection device according to claim 1, wherein the temperature sensor is provided corresponding to a battery module that constitutes the battery pack.

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