Voltage measuring device

Abstract

A voltage measurement device (12) comprises a first measurement circuit (31), a second measurement circuit (32), a cell balance switch (360), and a correction circuit (33), the first measurement circuit (31) being connected to a plurality of first battery cells (211, 212), a bus bar (23), and a plurality of second battery cells (221, 222) via a plurality of first RC filters, the second measurement circuit (32) being connected to a plurality of first battery cells (211, 212), a bus bar (23), and a plurality of second battery cells (221, 222) via a plurality of second RC filters, the cell balance switch (360) being connected in parallel to the bus bar (23) via two second RC filters (511, 521) connected to the bus bar (23), and the correction circuit (33) using the value of the voltage between both ends of the bus bar (23) measured by the first measurement circuit (31) to correct the value measured by the second measurement circuit (32).

Description

Technical Field

[0001] The present disclosure relates to a voltage measurement device.

Background Art

[0002] Conventionally, a voltage measurement device used in a battery module system including a battery module has been known (see, for example, Patent Document 1). The battery module has a plurality of battery cells connected in series. The voltage measurement device is connected to each battery cell via an RC filter and measures the voltage across both ends of each battery cell. A cell balance switch is connected in parallel across both ends of each battery cell. By controlling the cell balance switch based on the voltage across both ends of each battery cell measured by the voltage measurement device, the voltages across both ends of each of the plurality of battery cells are equalized.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When a battery module system comprises multiple battery modules connected in series, the battery modules are connected to each other by busbars. When measuring the cell voltages of multiple battery modules with a single voltage measuring device, a cell balance switch is also connected in parallel to the busbar. When a load is connected to a battery module and current flows through the battery module, current also flows through the busbar. Therefore, a voltage is applied to the busbar due to its electrical resistance. The voltage applied to the busbar is also applied to the RC filter and the cell balance switch. The cell balance switch connected to the busbar is normally kept in the off state, but current can flow through the body diode of the switching transistor that constitutes the cell balance switch. In other words, current can flow to the RC filter and the cell balance switch connected in parallel to the busbar.

[0005] Here, the RC filter connected in parallel to the busbar is also used as part of the voltage measurement circuit for the battery cells directly connected to the busbar (i.e., adjacent to the busbar). Therefore, a voltage drop occurs across the resistance component of the RC filter due to the current flowing through it. Consequently, an error equal to this voltage drop occurs in the measured voltage of the battery cells directly connected to the busbar. This error in the measurement may prevent the voltage measuring device from detecting abnormal voltages in the battery cells.

[0006] This disclosure aims to solve these problems and to provide a voltage measuring device that can accurately measure the voltage of a battery cell. [Means for solving the problem]

[0007] To solve the above problems, one embodiment of the voltage measuring device according to this disclosure is: A voltage measuring device used in a battery module system comprising: a first battery module having a plurality of first battery cells connected in series; a busbar connected in series to the first battery module; a second battery module connected in series to the first battery module via the busbar and having a plurality of second battery cells connected in series; a plurality of first RC filters and a plurality of second RC filters connected to at least one of the first battery module, the busbar, and the second battery module, wherein the voltage measuring device comprises: a first measuring circuit for measuring the voltage across the busbar; a second measuring circuit for measuring the voltage across each of the plurality of first battery cells and the plurality of second battery cells; and a correction circuit for correcting the measurement value obtained by the second measuring circuit, wherein the second measuring circuit is connected to the plurality of first battery cells, the busbar, and the plurality of second battery cells via the plurality of second RC filters, and the correction circuit corrects the measurement value obtained by the second measuring circuit using the measurement value of the voltage across the busbar obtained by the first measuring circuit.

[0008] To solve the above problems, another embodiment of the voltage measuring device according to this disclosure is: A voltage measuring device used in a battery module system comprising: a first battery module having a plurality of first battery cells connected in series; a busbar connected in series to the first battery module; a second battery module connected in series to the first battery module via the busbar and having a plurality of second battery cells connected in series; and a plurality of first RC filters and a plurality of second RC filters connected to at least one of the first battery module, the busbar, and the second battery module, wherein the voltage measuring device comprises: a first measuring circuit that measures the voltage between each of the plurality of first battery cells, the busbar, and the plurality of second battery cells; and the voltage between each of the plurality of first battery cells, the busbar, and the plurality of second battery cells The system includes a second measurement circuit for measuring pressure and a correction circuit for correcting the measurement value obtained by the first measurement circuit. One of the plurality of first RC filters is connected to each of the anodes of the plurality of first battery cells and the plurality of second battery cells, and to each of the connection points between the busbar and the first battery module. One of the plurality of second RC filters is connected to each of the cathodes of the plurality of first battery cells and the plurality of second battery cells, and to each of the connection points between the busbar and the second battery module. The first measurement circuit is connected to the plurality of first battery cells, the busbar and the plurality of second battery cells via the plurality of first RC filters. The correction circuit corrects the measurement value obtained by the first measurement circuit using the voltage measurement value obtained by the first measurement circuit across the busbar. [Effects of the Invention]

[0009] According to this disclosure, a voltage measuring device capable of accurately measuring the voltage of a battery cell can be provided. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a circuit diagram showing the overall configuration of the battery module system according to Embodiment 1. [Figure 2] Figure 2 is a circuit diagram showing the configuration of the first RC filter according to Embodiment 1. [Figure 3] Figure 3 is a circuit diagram showing the configuration of the second RC filter according to Embodiment 1. [Figure 4] Figure 4 is a flowchart showing a method for detecting the position of a busbar according to Embodiment 1. [Figure 5] Figure 5 is a circuit diagram showing the overall configuration of the battery module system according to Embodiment 2. [Figure 6] Figure 6 is a circuit diagram showing the overall configuration of the battery module system according to Embodiment 3. [Modes for carrying out the invention]

[0011] The embodiments of this disclosure will be described below with reference to the drawings. The embodiments described below are all specific examples of this disclosure. Therefore, the numerical values, shapes, materials, components, and their arrangement and connection configurations shown in the following embodiments are examples only and are not intended to limit this disclosure.

[0012] Furthermore, each figure is a schematic diagram and not necessarily a strictly accurate representation. Therefore, the scale and other aspects may not necessarily be consistent across all figures. In addition, the same reference numerals are used for substantially identical components in each figure, and redundant explanations are omitted or simplified.

[0013] (Embodiment 1) A voltage measurement device and a battery module system according to Embodiment 1 will be described.

[0014] [1-1. Overall Configuration] The overall configuration of a battery module system including the voltage measurement device according to this embodiment will be described using FIG. 1. FIG. 1 is a circuit diagram showing the overall configuration of the battery module system 10 according to this embodiment.

[0015] The battery module system 10 according to this embodiment is a system including a plurality of battery modules connected in series. As shown in FIG. 1, the battery module system 10 includes a first battery module 21, a second battery module 22, a bus bar 23, first RC filters 411 to 413, 421 to 423, second RC filters 511 to 513, 521 to 523, and a voltage measurement device 12.

[0016] The first battery module 21 is a module having a plurality of first battery cells 211 and 212 connected in series. The first battery cells 211 and 212 are, for example, lithium-ion batteries.

[0017] The second battery module 22 is a module having a plurality of second battery cells 221 and 222 connected in series. The second battery module 22 is connected in series to the first battery module 21 via the bus bar 23. The second battery cells 221 and 222 are, for example, lithium-ion batteries.

[0018] The bus bar 23 is a conductive member connected in series to the first battery module 21. The bus bar 23 has a resistance component. In this embodiment, one terminal of the bus bar 23 is connected to the cathode of the first battery cell 211 included in the first battery module 21, and the other terminal of the bus bar 23 is connected to the anode of the second battery cell 221 included in the second battery module 22.

[0019] Each of the first RC filters 411 to 413, 421 to 423 and the second RC filters 511 to 513, 521 to 523 is a filter including a resistance component and a capacitance component. Each of the first RC filters 411 to 413, 421 to 423 and the second RC filters 511 to 513, 521 to 523 is connected to at least one of the first battery module 21, the bus bar 23, and the second battery module 22. More specifically, at each connection point of the first battery cells 211, 212 connected in series, the bus bar 23, and the second battery cells 221, 222, one of the first RC filters 411 to 413, 421 to 423 and one of the second RC filters 511 to 513, 521 to 523 are connected. To the anode of the first battery cell 212, the first RC filter 413 and the second RC filter 513 are connected. To the connection point between the cathode of the first battery cell 212 and the anode of the first battery cell 211, the first RC filter 412 and the second RC filter 512 are connected. To the connection point between the cathode of the first battery cell 211 and the bus bar 23, the first RC filter 411 and the second RC filter 511 are connected. To the connection point between the bus bar 23 and the anode of the second battery cell 221, the first RC filter 421 and the second RC filter 521 are connected. To the connection point between the cathode of the second battery cell 221 and the anode of the second battery cell 222, the first RC filter 422 and the second RC filter 522 are connected. To the cathode of the second battery cell 222, the first RC filter 423 and the second RC filter 523 are connected.

[0020] The configurations of each of the first RC filters and each of the second RC filters will be described with reference to FIGS. 2 and 3. FIGS. 2 and 3 are circuit diagrams showing the configurations of the first RC filter 411 and the second RC filter 511 according to the present embodiment, respectively.

[0021] As shown in Figure 2, the first RC filter 411 has a first resistor 40r and a first capacitor 40c. The first resistor 40r is connected between terminal 41p and terminal 42p. The first capacitor 40c is connected between terminal 42p and terminal 43p. In this embodiment, terminal 41p is connected to the connection point between the cathode of the first battery cell 211 shown in Figure 1 and the busbar 23, terminal 42p is connected to the voltage measuring device 12, and terminal 43p is grounded. In this embodiment, the first RC filters 412, 413, 421-423 also have the same configuration as the first RC filter 411.

[0022] As shown in Figure 3, the second RC filter 511 has a second resistor 50r and a second capacitor 50c. The second resistor 50r is connected between terminal 51p and terminal 52p. The second capacitor 50c is connected between terminal 52p and terminal 53p. In this embodiment, terminal 51p is connected to the connection point between the cathode of the first battery cell 211 shown in Figure 1 and the busbar 23, terminal 52p is connected to the voltage measuring device 12, and terminal 53p is grounded. In this embodiment, the second RC filters 512, 513, 521-523 also have the same configuration as the second RC filter 511.

[0023] In this embodiment, the capacitors of each RC filter are grounded, but this is not necessarily required. For example, the terminal 43p to which the first capacitor 40c is connected, and the terminal 53p to which the second capacitor 50c is connected, may not be grounded and may be connected to terminals to which other RC filters are connected.

[0024] The voltage measuring device 12 is a device used in the battery module system 10. The voltage measuring device 12 measures the voltage across the terminals of each battery cell in the first battery module 21 and the second battery module 22, and also measures the voltage across the terminals of the busbar 23. The voltage measuring device 12 is composed of, for example, a multi-channel input and high-voltage voltage measuring IC, and collects the measured voltage and controls the cell balance switch from a microcontroller or the like. The microcontroller is a single-chip semiconductor integrated circuit having memory such as ROM and RAM where the program is stored, a processor (CPU; Central Processing Unit) that executes the program, a timer, and input / output circuits including an A / D converter and a D / A converter.

[0025] As shown in Figure 1, the voltage measuring device 12 includes a first measuring circuit 31, a second measuring circuit 32, a switch circuit 34, and a correction circuit 33. In this embodiment, the voltage measuring device 12 further includes a switch control circuit 35, a memory circuit 36, a diagnostic circuit 37, and a timing control circuit 38.

[0026] The first measurement circuit 31 is a circuit that measures the voltage across the first battery cells 211, 212, the busbar 23, and the second battery cells 221, 222. The first measurement circuit 31 is connected to the first battery cells 211, 212, the busbar 23, and the second battery cells 221, 222 via first RC filters 411-413 and 421-423.

[0027] The second measurement circuit 32 is a circuit that measures the voltage across the first battery cells 211, 212, the busbar 23, and the second battery cells 221, 222. The second measurement circuit 32 is connected to the first battery cells 211, 212, the busbar 23, and the second battery cells 221, 222 via second RC filters 511-513 and 521-523.

[0028] The switch circuit 34 is a circuit having cell balance switches 360-362, 371, and 372. Each cell balance switch is a switch for equalizing the voltage across the terminals of each battery cell. For example, a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) can be used as each cell balance switch. Each cell balance switch is controlled by the switch control circuit 35. In this embodiment, cell balance switch 360 is connected in parallel to the busbar 23 via second RC filters 511 and 521 connected to the busbar 23. Cell balance switch 361 is connected in parallel to the first battery cell 211 via second RC filters 511 and 512 connected to the first battery cell 211. Cell balance switch 362 is connected in parallel to the first battery cell 212 via second RC filters 512 and 513 connected to the first battery cell 212. Cell balance switch 371 is connected in parallel to the second battery cell 221 via second RC filters 521 and 522 connected to the second battery cell 221. The cell balance switch 372 is connected in parallel to the second battery cell 222 via the second RC filters 522 and 523, which are connected to the second battery cell 222.

[0029] The switch control circuit 35 is a circuit that controls each cell balance switch of the switch circuit 34. The switch control circuit 35 controls each cell balance switch in order to equalize the voltage across the terminals of each battery cell.

[0030] The correction circuit 33 is a circuit that corrects the measured voltage. In this embodiment, the correction circuit 33 corrects the measured value obtained by the second measurement circuit 32. More specifically, the correction circuit 33 corrects the measured value obtained by the second measurement circuit 32 using the measured voltage across the busbar 23 obtained by the first measurement circuit 31. Details of the correction method will be described later.

[0031] The memory circuit 36 ​​is a circuit that stores information used in the voltage measuring device 12. In this embodiment, the memory circuit 36 ​​stores the position to which the busbar 23 is connected. Specifically, it stores that the busbar 23 is connected in parallel with the cell balance switch 360. This position information is used in the switch control circuit 35 and the correction circuit 33.

[0032] The diagnostic circuit 37 is a circuit that compares the measurement value obtained by the first measurement circuit 31 with the measurement value corrected by the correction circuit 33 (i.e., the corrected value). Based on the comparison, the diagnostic circuit 37 outputs a diagnostic result. For example, if the measurement value obtained by the first measurement circuit 31 differs from the measurement value corrected by the correction circuit 33, the diagnostic circuit 37 outputs a diagnostic result indicating that there is an abnormality in at least one of the first measurement circuit 31 and the second measurement circuit 32. Also, if the measurement value obtained by the first measurement circuit 31 matches the measurement value corrected by the correction circuit 33, the diagnostic circuit 37 outputs a diagnostic result indicating that both the first measurement circuit 31 and the second measurement circuit 32 are normal. With such a diagnostic circuit 37, it is possible to detect and notify of abnormalities in the voltage measuring device 12.

[0033] The timing control circuit 38 synchronizes the timing of the measurement of the voltage across the busbar 23 by the first measurement circuit 31 with at least one of the timings at which the second measurement circuit 32 measures the voltage across the busbar 23, specifically the voltage across the first battery cell 211, which is directly connected to the busbar 23, and the timing at which the second battery cell 221, which is directly connected to the busbar 23, is measured by the first measurement circuit 31. For example, the timing control circuit 38 outputs trigger pulse signals simultaneously to the first measurement circuit 31 and the second measurement circuit 32 in order to synchronize the measurement timings.

[0034] [1-2. Measurement Correction Method] A method for correcting the measured voltage between the terminals of each battery cell in the voltage measuring device 12 according to this embodiment will be described.

[0035] As described above, since the busbar 23 has a resistive component, when a load is connected to the battery module system 10 and current flows through each battery module and the busbar 23, a voltage drop occurs in the busbar 23. In this case, the potential at the connection point between the busbar 23 and the second battery cell 221 is higher than the potential at the connection point between the busbar 23 and the first battery cell 211. Therefore, voltage is applied to the second RC filter 521, the cell balance switch 360, and the second RC filter 511. Consequently, current flows through the second RC filter 521, the body diode of the cell balance switch 360, and the second RC filter 511. Along with this, a voltage drop occurs in the second resistor 50r of the second RC filters 511 and 521.

[0036] Here, the second RC filter 511 is included in the circuit used for measuring the voltage across the first battery cell 211, which is directly connected to the busbar 23, by the second measurement circuit 32. As a result, an error occurs in the measured voltage of the first battery cell 211 (measured value V211 shown in Figure 1) due to the voltage drop across the second resistor 50r of the second RC filter 511.

[0037] Similarly, the second RC filter 521 is included in the circuit used to measure the voltage across the second battery cell 221, which is directly connected to the busbar 23. As a result, an error occurs in the measured voltage of the second battery cell 221 (measured value V221 shown in Figure 1) due to the voltage drop across the second resistor 50r of the second RC filter 521.

[0038] Note that the measurements taken by the second measurement circuit 32 for each battery cell that is not directly connected to the busbar 23 (measurements V212 and V222 shown in Figure 1) do not include any error.

[0039] As described above, the measured value V211 of the second measurement circuit 32, which measures the voltage of the first battery cell 211 via the second RC filter 511, may contain errors. Furthermore, the measured value V221 of the second measurement circuit 32, which measures the voltage of the second battery cell 221 via the second RC filter 521, may contain errors.

[0040] On the other hand, while the measurements from the first measurement circuit 31 (V111, V112, V121~V123 shown in Figure 1) do not contain errors, the measurements from the second measurement circuit 32 are also required to be accurate in order to ensure redundancy of the voltage measurement function of the voltage measuring device 12.

[0041] In this embodiment, the measurement value by the second measurement circuit 32 is corrected by the correction circuit 33. As described above, the measurement value V211 of the voltage across the terminals of the first battery cell 211 by the second measurement circuit 32 is measured lower than the actual (i.e., true) voltage value V11 across the terminals of the first battery cell 211 by the voltage drop V511 at the second resistor 50r of the second RC filter 511. Here, the voltage drop V511 is defined as a positive value when the potential is higher on the voltage measuring device 12 side than on the cathode side of the first battery cell 211 to which the second RC filter 511 is connected, and a negative value when the potential is lower on the voltage measuring device 12 side than on the cathode side of the first battery cell 211. In this embodiment, the voltage drop V511 is a negative value.

[0042] Therefore, the following equation holds between the measured voltage V211 across the first battery cell 211 in the second measurement circuit 32, the actual voltage V11 across the first battery cell 211, and the voltage drop V511.

[0043] V211 = V11 + V511

[0044] Similarly, the following equation holds between the measured voltage V221 across the second battery cell 221 in the second measurement circuit 32, the actual voltage value V21 across the second battery cell 221, and the voltage drop V521 across the second resistor 50r of the second RC filter 521.

[0045] V221 = V21 + V521

[0046] Here, the voltage drop V521 is defined as a positive value when the potential on the voltage measuring device 12 side is lower than the potential on the anode side of the second battery cell 221 to which the second RC filter 521 is connected, and a negative value when the potential on the voltage measuring device 12 side is lower than the potential on the cathode side of the first battery cell 211.

[0047] Furthermore, the following equation holds true between the measured voltage V223 across the busbar 23 in the second measurement circuit 32 and the actual voltage V23 across the busbar 23.

[0048] V223 = V23 - V511 - V521

[0049] Furthermore, the actual voltage value V23 across the busbar 23 is equal to the measured voltage V123 across the busbar 23 obtained by the first measurement circuit 31.

[0050] Since the second RC filter 511 and the second RC filter 521 have the same configuration, the voltage drops V511 and V521 are equal.

[0051] Based on the above, the voltage values ​​V11 and V21 can be expressed by the following formulas.

[0052] V11 = V211 - 0.5 × (V123 - V223) V21 = V221 - 0.5 × (V123 - V223)

[0053] The correction circuit 33 uses these relational expressions to calculate corrected values ​​by correcting the measured values ​​V211 and V221.

[0054] As described above, in this embodiment, the correction circuit 33 calculates a correction amount of 0.5 × (V123 - V223) based on the measured voltage V123 across the busbar 23 by the first measurement circuit 31 and the measured voltage V223 across the busbar by the second measurement circuit 32. The correction circuit 33 also subtracts the correction amount from the measured voltages by the second measurement circuit 32 for the voltage across the first battery cell 211, which is directly connected to the busbar 23, and for the voltage across the second battery cell 221, which is directly connected to the busbar 23, among the first battery cells 211 and 212. The configuration of the correction circuit 33 is not limited to this. For example, the correction circuit 33 may add the correction amount (instead of subtracting it) to the measured value by the second measurement circuit 32 by setting the correction amount to 0.5 × (V223 - V123) (i.e., reversing the sign of the correction amount).

[0055] As described above, with the voltage measuring device 12 according to this embodiment, the voltage of the first battery cell 211 and the second battery cell 221 directly connected to the busbar 23 can be accurately measured by correcting the measurement value of the second measuring circuit 32 with the correction circuit 33.

[0056] Furthermore, the cell balance switch 360 connected in parallel to the busbar 23 may be kept in the ON state by the switch control circuit 35. This suppresses the flow of current through the body diode of the cell balance switch 360, thereby preventing the cell balance switch 360 from being damaged by such current.

[0057] Thus, when the cell balance switch 360 is kept in the ON state, if the resistance component in the cell balance switch 360 is small enough to be ignored, the measurement value V223 from the second measurement circuit 32 can be ignored. Therefore, in this case, the voltage values ​​V11 and V21 are expressed by the following formulas.

[0058] V11 = V211 - 0.5 × V123 V21 = V221 - 0.5 × V123

[0059] The correction circuit 33 may calculate a correction value by correcting the measured values ​​V211 and V221 using these relational expressions. In other words, the correction circuit 33 may calculate the correction amount (0.5 × V123) based on the measured voltage across the busbar 23 by the first measurement circuit 31. This makes the correction process simpler.

[0060] In this embodiment, the timing control circuit 38 synchronizes the timing at which the second measurement circuit 32 measures the voltage across the terminals of the first battery cell 211 and the voltage across the terminals of the second battery cell 221 with the timing at which the first measurement circuit 31 measures the voltage across the terminals of the busbar 23. This enables highly accurate measurements even when the current flowing through each battery cell and busbar 23 fluctuates over time.

[0061] [1-3. Busbar position detection] As described above, the position of the busbar 23 may be stored in the memory circuit 36, but the first measurement circuit 31 and the second measurement circuit 32 can also detect the position of the busbar 23. Below, the method for detecting the position of the busbar 23 by the first measurement circuit 31 and the second measurement circuit 32 will be explained with reference to Figure 4. Figure 4 is a flowchart showing the method for detecting the position of the busbar 23 according to this embodiment.

[0062] As shown in Figure 4, first, the battery module system 10 is started (startup step S10).

[0063] Next, the following steps are repeated for all measurement channels of the first measurement circuit 31 and the second measurement circuit 32 (S12).

[0064] The voltage of one channel of the first measurement circuit 31 and the second measurement circuit 32 is measured (measurement step S14).

[0065] Next, based on the measurement value in measurement step S14, the measurement target connected to the channel is determined (determination step S16). Specifically, if the measurement value is positive, it is determined that a battery cell is connected to the measurement channel; if the measurement value is negative, it is determined that a bus bar 23 is connected to the measurement channel; and if the measurement value is zero, it is determined that neither a battery cell nor a bus bar is connected to the measurement channel (i.e., it is an empty channel).

[0066] The measurement step S14 and the determination step S16 described above are repeated for all measurement channels (S18).

[0067] As described above, in this embodiment, at least one of the first measurement circuit 31 and the second measurement circuit 32 may detect the location to which the busbar 23 is connected based on the measured voltage between each first battery cell, the busbar 23, and each of the multiple second battery cells. This allows the voltage measuring device 12 to detect the location of the busbar 23 without storing the location of the busbar 23 in the memory circuit 36.

[0068] (Embodiment 2) The voltage measuring device and battery module system according to Embodiment 2 will now be described. The voltage measuring device according to this embodiment differs from the voltage measuring device 12 according to Embodiment 1 in that it is equipped with an averaging filter for averaging the measured values, but is otherwise identical. The voltage measuring device and battery module system according to this embodiment will be described below, focusing on the differences from the voltage measuring device 12 and battery module system 10 according to Embodiment 1, with reference to Figure 5.

[0069] Figure 5 is a circuit diagram showing the overall configuration of the battery module system 10a according to this embodiment. As shown in Figure 5, the battery module system 10a according to this embodiment comprises a first battery module 21, a second battery module 22, a busbar 23, first RC filters 411-413, 421-423, second RC filters 511-513, 521-523, and a voltage measuring device 12a.

[0070] The voltage measuring device 12a according to this embodiment, like the voltage measuring device 12 according to Embodiment 1, includes a first measurement circuit 31, a second measurement circuit 32, a switch circuit 34, a correction circuit 33, a switch control circuit 35, a memory circuit 36, and a diagnostic circuit 37. In this embodiment, the voltage measuring device 12a further includes a first average filter 61 and a second average filter 62.

[0071] The first average filter 61 is a filter that averages the measured values ​​from the first measurement circuit 31 over time. The first average filter 61 averages the signals corresponding to the measured values ​​of each channel from the first measurement circuit 31 over time. For example, a low-pass filter can be used as the first average filter 61. The output signal from the first measurement circuit 31 is input to the first average filter 61, and the averaged signal is output as the measured value. This measured value is input to the diagnostic circuit 37.

[0072] The second mean filter 62 is a filter that averages the measured values ​​from the second measurement circuit 32 over time. The second mean filter 62 averages the signals corresponding to the measured values ​​of each channel from the second measurement circuit 32 over time. For example, a low-pass filter can be used as the second mean filter 62. The output signal from the second measurement circuit 32 is input to the second mean filter 62, and the averaged signal is output as the measured value. This measured value is input to the correction circuit 33.

[0073] In the battery module system 10a according to this embodiment, the voltage across each battery cell and the busbar 23 fluctuates due to fluctuations in the discharge current output by each battery module. Therefore, the measured values ​​from the first measurement circuit 31 and the second measurement circuit 32 also fluctuate. In this embodiment, the fluctuations in the measured values ​​can be suppressed by averaging the measured values ​​over time using the first average filter 61 and the second average filter 62. Therefore, more accurate voltage measurement becomes possible.

[0074] Furthermore, in this embodiment, by adjusting the filtering characteristics of the first average filter 61 and the second average filter 62, the combined filtering characteristics of the first RC filters 411-413, 421-423, the first measurement circuit 31, and the first average filter 61 are made similar to the combined filtering characteristics of the second RC filters 511-513, 521-523, the second measurement circuit 32, and the second average filter 62. In other words, the difference between the combined filtering characteristics of the first RC filters 411-413, 421-423, the first measurement circuit 31, and the first mean filter 61, and the combined filtering characteristics of the second RC filters 511-513, 521-523, the second measurement circuit 32, and the second mean filter 62, is smaller than the difference between the combined filtering characteristics of the first RC filters 411-413, 421-423, and the first measurement circuit 31, and the combined filtering characteristics of the second RC filters 511-513, 521-523, and the second measurement circuit 32.

[0075] This allows the variation characteristics of the measured values ​​output from the first mean filter 61 and the second mean filter 62 to be aligned, enabling highly accurate voltage measurement and voltage correction.

[0076] (Embodiment 3) The voltage measuring device and battery module system according to Embodiment 3 will now be described. The voltage measuring device and battery module system according to this embodiment differ from the voltage measuring device and battery module system according to Embodiment 1, mainly in the connection configuration of the cell balance switch and the like. The following description will focus on the differences between the voltage measuring device and battery module system according to this embodiment and the voltage measuring device 12 and battery module system 10 according to Embodiment 1.

[0077] [3-1. Overall Structure] The overall configuration of the battery module system equipped with a voltage measuring device according to this embodiment will be explained with reference to Figure 6. Figure 6 is a circuit diagram showing the overall configuration of the battery module system 10b according to this embodiment. As shown in Figure 6, the battery module system 10b comprises a first battery module 21, a second battery module 22, a bus bar 23, first RC filters 411-413, 421-423, second RC filters 511-513, 521, 522, and a voltage measuring device 12b.

[0078] As shown in Figure 6, in this embodiment as well, similar to the battery module system 10 according to Embodiment 1, one of the first RC filters 411-413, 421-423 is connected to the anodes of each of the first battery cells 211, 212 and the second battery cells 221, 222, as well as to each of the connection points between the busbar 23 and the first battery module 21. In addition, one of the second RC filters 511-513, 521, 522 is connected to the cathodes of each of the first battery cells 211, 212 and the second battery cells 221, 222, as well as to each of the connection points between the busbar 23 and the second battery module 22.

[0079] The voltage measuring device 12b comprises a first measuring circuit 31b, a second measuring circuit 32b, a switch circuit 34b, and a correction circuit 33b. In this embodiment, the voltage measuring device 12b further comprises a switch control circuit 35, a memory circuit 36, a diagnostic circuit 37b, and a timing control circuit 38.

[0080] The first measurement circuit 31b is a circuit that measures the voltage across the first battery cells 211 and 212, the busbar 23, and the second battery cells 221 and 222. The first measurement circuit 31b is connected to the first battery cells 211 and 212, the busbar 23, and the second battery cells 221 and 222 via the first RC filters 411 to 413 and 421 to 423.

[0081] The second measurement circuit 32b is a circuit that measures the voltage across the first battery cells 211, 212, the busbar 23, and the second battery cells 221, 222. The second measurement circuit 32 is connected to the first battery cells 211, 212, the busbar 23, and the second battery cells 221, 222 via the first RC filters 411, 412, 421-423 and the second RC filters 511-513, 521, 522.

[0082] The switch circuit 34b is a circuit having cell balance switches 360-362, 371, and 372. Each cell balance switch is controlled by the switch control circuit 35. In this embodiment, cell balance switch 360 is connected in parallel to the busbar 23 via a second RC filter 511 connected to the connection point between the busbar 23 and the first battery module 21, and a first RC filter 421 connected to the connection point between the busbar 23 and the second battery module 22. Cell balance switch 361 is connected in parallel to the first battery cell 211 via a second RC filter 512 and a first RC filter 411 connected to the first battery cell 211. Cell balance switch 362 is connected in parallel to the first battery cell 212 via a second RC filter 513 and a first RC filter 412 connected to the first battery cell 212.

[0083] The cell balance switch 371 is connected in parallel to the second battery cell 221 via the second RC filter 521 and the first RC filter 422, which are connected to the second battery cell 221. The cell balance switch 372 is connected in parallel to the second battery cell 222 via the second RC filter 522 and the first RC filter 423, which are connected to the second battery cell 222.

[0084] In the manner described above, the cell balance switches 360-362, 371, and 372 are connected to the first battery module 21 and the second battery module 22, thereby avoiding direct connection between adjacent cell balance switches. For example, if multiple cell balance switches are directly connected and all of them are kept in the ON state, and both ends of each battery cell connected to them are short-circuited, there is a concern that a large current from the stacked high-voltage battery cells will flow through the multiple cell balance switches, potentially leading to the destruction of the cell balance switches. Therefore, only every other cell can be turned ON. In this embodiment, since adjacent cell balance switches are not directly connected, it is possible to prevent a large current from flowing through the cell balance switches, and equalization of all battery cells can be performed simultaneously. This allows equalization to be performed in a short time.

[0085] The correction circuit 33b corrects the measurement value obtained by the first measurement circuit 31b. More specifically, the correction circuit 33b corrects the measurement value obtained by the first measurement circuit 31b using the voltage measurement value obtained by the first measurement circuit 31b across the busbar 23. Details of the correction method will be described later.

[0086] The diagnostic circuit 37b is a circuit that compares the measured value corrected by the correction circuit 33 (i.e., the corrected value) with the measured value obtained by the second measurement circuit 32b. Based on the comparison, the diagnostic circuit 37b outputs a diagnostic result.

[0087] The switch control circuit 35, memory circuit 36, and timing control circuit 38 of the voltage measuring device 12b have the same configuration as the switch control circuit 35, memory circuit 36, and timing control circuit 38 according to Embodiment 1, respectively.

[0088] [3-2. Measurement Correction Method] A method for correcting the measured voltage between the terminals of each battery cell in the voltage measuring device 12b according to this embodiment will be described.

[0089] As described above, since the busbar 23 has a resistive component, a voltage drop occurs in the busbar 23 when current flows through each battery module and the busbar 23. Therefore, a voltage is applied to the first RC filter 421, the cell balance switch 360 connected in parallel to the busbar 23, and the second RC filter 511. Consequently, current flows through the first RC filter 421, the body diode of the cell balance switch 360, and the second RC filter 511. As a result, a voltage drop occurs in the first resistor 40r of the first RC filter 421 and the second resistor 50r of the second RC filter 511.

[0090] Here, the first RC filter 421 is included in the circuit used for measuring the voltage across the second battery cell 221, which is directly connected to the busbar 23, by the first measurement circuit 31b. As a result, an error occurs in the measured voltage of the second battery cell 221 (measured value V121 shown in Figure 6) due to the voltage drop across the first resistor 40r of the first RC filter 421.

[0091] Note that the measurements of other battery cells by the first measurement circuit 31b (measurements V111, V112, V122 shown in Figure 6) and the measurements of the battery cell by the second measurement circuit 32b (measurements V211, V212, V221, V222 shown in Figure 6) do not include any errors.

[0092] In this embodiment, the measurement value by the first measurement circuit 31b is corrected by the correction circuit 33b. As described above, the measurement value V121 of the voltage across the second battery cell 221 by the first measurement circuit 31b is measured lower than the actual voltage value V21 across the second battery cell 221 by the voltage drop V421 at the first resistor 40r of the first RC filter 421. Here, the voltage drop V421 is defined as a positive value when the potential is higher on the voltage measuring device 12b side than on the anode side of the second battery cell 221 to which the first RC filter 421 is connected, and a negative value when the potential is lower on the voltage measuring device 12b side than on the anode side of the second battery cell 221. In this embodiment, the voltage drop V421 is a negative value.

[0093] Therefore, the following equation holds between the measured voltage V121 across the second battery cell 221 in the first measurement circuit 31b, the actual voltage value V21 across the second battery cell 221, and the voltage drop V421.

[0094] V121 = V21 - V421

[0095] Furthermore, the following equation holds true between the measured voltage V123 across the busbar 23 in the first measurement circuit 31b and the actual voltage V23 across the busbar 23.

[0096] V123 = V23 - V421

[0097] Furthermore, the following equation holds between the measured voltage V223 across the busbar 23 in the second measurement circuit 32b and the actual voltage V23 across the busbar 23.

[0098] V223 = V23 - V421 - V511

[0099] Here, by making the resistance values ​​of the first resistor 40r of the first RC filter 421 and the second resistor 50r of the second RC filter 521 equal, the voltage drop V421 and the voltage drop V511 become equal. Therefore, the voltage value V21 is expressed by the following formula.

[0100] V11 = V211 + V223 - V123

[0101] The correction circuit 33b uses the above relationship to calculate a corrected value by correcting the measured value V121.

[0102] As described above, in this embodiment, the correction circuit 33b calculates a correction amount (V223-V123) based on the measured voltage V123 across the busbar 23 by the first measurement circuit 31b and the measured voltage V223 across the busbar by the second measurement circuit 32b. The correction circuit 33b also adds the correction amount to the measured voltage across the second battery cell 221, which is directly connected to the busbar 23, as measured by the first measurement circuit 31b. The configuration of the correction circuit 33b is not limited to this. For example, the correction circuit 33b may subtract the correction amount (instead of adding it) from the measured value by the first measurement circuit 31b, using the correction amount as (V123-V223) (i.e., with the sign of the correction amount reversed).

[0103] As described above, with the voltage measuring device 12b according to this embodiment, the voltage of the second battery cell 221 directly connected to the busbar 23 can be accurately measured by correcting the measurement value of the first measuring circuit 31b with the correction circuit 33b.

[0104] In this embodiment as well, similar to Embodiment 1, the cell balance switch 360 connected in parallel to the busbar 23 may be kept in the ON state by the switch control circuit 35. This suppresses the flow of current through the body diode of the cell balance switch 360, thereby preventing the cell balance switch 360 from being damaged by such current.

[0105] Thus, when the cell balance switch 360 is kept in the ON state, if the resistance component in the cell balance switch 360 is small enough to be ignored, the measurement value V223 from the second measurement circuit 32b can be ignored. Therefore, in this case, V21 is expressed by the following formula.

[0106] V21 = V221 - V123

[0107] The correction circuit 33b may use this relationship to calculate a correction value by correcting the measured value V121. In other words, the correction circuit 33b may calculate the correction amount (-V123) based on the measured voltage across the busbar 23 by the first measurement circuit 31b. This makes the correction process simpler.

[0108] (Torture, etc.) Although the present disclosure has been described above based on various embodiments, the present disclosure is not limited to the above embodiments.

[0109] For example, in each of the above embodiments, the battery module system comprises two battery modules and one busbar, but it may also comprise three or more battery modules and two or more busbars.

[0110] Furthermore, in each of the above embodiments, each battery module had two battery cells, but it may have three or more battery cells.

[0111] Furthermore, in each of the above embodiments, the correction circuit corrected both the measured voltage values ​​across the first battery cell 211 and the second battery cell 221, but it is sufficient to correct at least one of them.

[0112] Furthermore, although the voltage measuring device in each of the above embodiments includes a memory circuit 36 ​​and a diagnostic circuit 37, the voltage measuring device does not necessarily have to include at least one of the memory circuit 36 ​​and the diagnostic circuit 37.

[0113] Furthermore, the battery module systems according to each of the above embodiments may be housed in, for example, a single enclosure, or they may be separated into multiple units.

[0114] Furthermore, some or all of the components constituting the voltage measuring device and battery module system according to each of the above embodiments may be composed of a single system LSI (Large Scale Integration). The system LSI is a highly functional LSI manufactured by integrating multiple components onto a single chip, and specifically, it is a computer system composed of a microprocessor, ROM, RAM, etc. A computer program is stored in the RAM. The system LSI achieves its function by operating the microprocessor in accordance with the computer program.

[0115] Furthermore, this disclosure also includes forms obtained by applying various modifications to each of the above embodiments that a person skilled in the art could conceive, and forms realized by arbitrarily combining the components and functions of each of the above embodiments without departing from the spirit of this disclosure.

[0116] For example, in the voltage measuring device 12b according to Embodiment 3, a first average filter 61 that averages the measured values ​​from the first measuring circuit 31b over time and a second average filter 62 that averages the measured values ​​from the second measuring circuit 32b over time may be applied, similar to the voltage measuring device 12a according to Embodiment 2. [Industrial applicability]

[0117] The voltage measuring device relating to this disclosure can be used, for example, as a voltage measuring device for an in-vehicle battery module system. [Explanation of Symbols]

[0118] 10, 10a, 10b Battery Module System 12, 12a, 12b Voltage measuring device 21 First Battery Module 22 Second Battery Module 23 Bus Bar 31, 31b First measurement circuit 32, 32b Second measurement circuit 33, 33b correction circuit 34, 34b Switch Circuit 35 Switch control circuit 36 Memory circuit 37, 37b Diagnostic Circuit 38 Timing control circuit 40c First Capacitor 40r first resistance 41p, 42p, 43p, 51p, 52p, 53p terminals 50C Second Capacitor 50r second resistor 61 First Mean Filter 62 Second mean filter 211, 212 First battery cell 221, 222 Second battery cell 360, 361, 362, 371, 372 Cell balance switch 411, 412, 413, 421, 422, 423 First RC filter 511, 512, 513, 521, 522, 523 Second RC filter V111, V112, V121, V122, V123, V211, V212, V221, V222, V223 Measured values

Claims

1. A first battery module having multiple first battery cells connected in series, A busbar connected in series to the first battery module, A second battery module is connected in series to the first battery module via the busbar and has a plurality of second battery cells connected in series, A voltage measuring device used in a battery module system comprising the first battery module, the busbar, and a plurality of first RC filters and a plurality of second RC filters connected to at least one of the second battery modules, The voltage measuring device is A first measurement circuit for measuring the voltage across the busbar, A second measurement circuit for measuring the voltage across each of the plurality of first battery cells and the plurality of second battery cells, The system includes a correction circuit for correcting the measurement value obtained by the second measurement circuit, The second measurement circuit is connected to the plurality of first battery cells, the busbar, and the plurality of second battery cells via the plurality of second RC filters. The correction circuit corrects the measurement value obtained by the second measurement circuit using the measurement value of the voltage across the busbar obtained by the first measurement circuit. Voltage measuring device.

2. One of the plurality of first RC filters and one of the plurality of second RC filters are connected to each connection point of the plurality of first battery cells, the busbar, and the plurality of second battery cells that are connected in series. The voltage measuring device according to claim 1.

3. The first measurement circuit is connected to the plurality of first battery cells, the busbar, and the plurality of second battery cells via the plurality of first RC filters. The voltage measuring device according to claim 1 or 2.

4. The plurality of second RC filters, including two second RC filters connected to the busbar, are further comprising a cell balance switch connected in parallel to the busbar. A voltage measuring device according to any one of claims 1 to 3.

5. The system further comprises a switch control circuit that maintains the cell balance switch in the ON state. The voltage measuring device according to claim 4.

6. At least one of the first measurement circuit and the second measurement circuit detects the location where the busbar is connected based on the measured voltages across each of the plurality of first battery cells, the busbar, and the plurality of second battery cells. A voltage measuring device according to any one of claims 1 to 5.

7. The second measurement circuit further includes a timing control circuit that synchronizes the timing of measuring the voltage across the busbar with at least one of the timings of measuring the voltage across the busbar with the timing of measuring the voltage across the busbar with the timing of measuring the voltage across the busbar with the timing of measuring the voltage across the busbar. A voltage measuring device according to any one of claims 1 to 6.

8. The diagnostic circuit further comprises a diagnostic circuit that compares the measurement value obtained by the first measurement circuit with the measurement value corrected by the correction circuit. A voltage measuring device according to any one of claims 1 to 7.

9. A first average filter that averages the measured values ​​from the first measurement circuit over time, The system further comprises a second mean filter that averages the measured values ​​from the second measurement circuit over time. A voltage measuring device according to any one of claims 1 to 8.

10. The difference between the combined filtering characteristics of the plurality of first RC filters, the first measurement circuit, and the first mean filter and the combined filtering characteristics of the plurality of second RC filters, the second measurement circuit, and the second mean filter is smaller than the difference between the combined filtering characteristics of the plurality of first RC filters and the first measurement circuit and the combined filtering characteristics of the plurality of second RC filters and the second measurement circuit. The voltage measuring device according to claim 9.

11. The correction circuit described above is Based on the voltage measurement value across the busbar by the first measurement circuit, a correction amount is calculated. The correction amount is added to or subtracted from the measurement value obtained by the second measurement circuit for at least one of the voltages between the ends of the first battery cell directly connected to the busbar among the plurality of first battery cells, and the voltage between the ends of the second battery cell directly connected to the busbar among the plurality of second battery cells. A voltage measuring device according to any one of claims 1 to 10.

12. The second measuring circuit measures the voltage across the busbar, The correction circuit calculates a correction amount based on the voltage measurement across the busbar by the first measurement circuit and the voltage measurement across the busbar by the second measurement circuit. The voltage measuring device according to claim 11.

13. A first battery module having multiple first battery cells connected in series, A busbar connected in series to the first battery module, A second battery module is connected in series to the first battery module via the busbar and has a plurality of second battery cells connected in series, A voltage measuring device used in a battery module system comprising the first battery module, the busbar, and a plurality of first RC filters and a plurality of second RC filters connected to at least one of the second battery modules, The voltage measuring device is A first measurement circuit that measures the voltage across each of the plurality of first battery cells, the busbar, and the plurality of second battery cells, A second measurement circuit that measures the voltage across each of the plurality of first battery cells, the busbar, and the plurality of second battery cells, The system includes a correction circuit for correcting the measurement value obtained by the first measurement circuit, One of the multiple first RC filters is connected to each of the anodes of the multiple first battery cells and the multiple second battery cells, as well as to each of the connection points between the busbar and the first battery module. One of the multiple second RC filters is connected to each cathode of the multiple first battery cells and the multiple second battery cells, as well as to each connection point between the busbar and the second battery module. The first measurement circuit is connected to the plurality of first battery cells, the busbar, and the plurality of second battery cells via the plurality of first RC filters. The correction circuit corrects the measurement value obtained by the first measurement circuit using the measurement value of the voltage across the busbar obtained by the first measurement circuit. Voltage measuring device.

14. The second measurement circuit is connected to the plurality of first battery cells, the busbar, and the plurality of second battery cells via the plurality of first RC filters and the plurality of second RC filters. The voltage measuring device according to claim 13.

15. A cell balance switch is connected in parallel to the busbar via a second RC filter, among the plurality of second RC filters, which is connected to the connection point between the busbar and the first battery module, and a first RC filter, among the plurality of first RC filters, which is connected to the connection point between the busbar and the second battery module. The voltage measuring device according to claim 13 or 14.

16. The system further comprises a switch control circuit that maintains the cell balance switch in the ON state. The voltage measuring device according to claim 15.

17. At least one of the first measurement circuit and the second measurement circuit detects the location where the busbar is connected based on the measured voltages across each of the plurality of first battery cells, the busbar, and the plurality of second battery cells. A voltage measuring device according to any one of claims 13 to 16.

18. The second measurement circuit further includes a timing control circuit that synchronizes the timing of measuring the voltage across the busbar with at least one of the timings of measuring the voltage across the busbar with the timing of measuring the voltage across the busbar with the timing of measuring the voltage across the busbar with the timing of measuring the voltage across the busbar. A voltage measuring device according to any one of claims 13 to 17.

19. The diagnostic circuit further comprises a diagnostic circuit that compares the measurement value corrected by the correction circuit with the measurement value obtained by the second measurement circuit. A voltage measuring device according to any one of claims 13 to 18.

20. A first average filter that averages the measured values ​​from the first measurement circuit over time, The system further comprises a second mean filter that averages the measured values ​​from the second measurement circuit over time. A voltage measuring device according to any one of claims 13 to 16.

21. The difference between the combined filtering characteristics of the plurality of first RC filters, the first measurement circuit, and the first mean filter and the combined filtering characteristics of the plurality of first RC filters, the plurality of second RC filters, the second measurement circuit, and the second mean filter is smaller than the difference between the combined filtering characteristics of the plurality of first RC filters and the first measurement circuit and the combined filtering characteristics of the plurality of first RC filters, the plurality of second RC filters, and the second measurement circuit. The voltage measuring device according to claim 20.

22. The correction circuit described above is A correction amount is calculated based on the voltage measurement across the busbar by the first measurement circuit and the voltage measurement across the busbar by the second measurement circuit. The correction amount is added to or subtracted from the measurement value obtained by the first measurement circuit of the voltage between both ends of the second battery cell that is directly connected to the busbar among the plurality of second battery cells. A voltage measuring device according to any one of claims 13 to 21.

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