Voltage Detector

Abstract

To provide a voltage detection device capable of suppressing the potential difference between a power supply voltage input line and a highest cell voltage input line from increasing beyond a threshold value when the voltage of the top cell drops due to the difference in time constant between the time constant circuit provided in the power supply voltage input line and the time constant circuit provided in the highest cell voltage input line.SOLUTION: The voltage detection device includes a switching diode 60 that connects a portion of a power supply voltage input line 30 closer to a module voltage detection circuit 10 than a power supply voltage filter circuit 50 and a portion closer to the module voltage detection circuit 10 than a cell voltage filter circuit 40 of a highest cell voltage input line 21. The switching diode 60 is configured to flow a current when the potential difference between the power supply voltage input line 30 and the highest cell voltage input line 21 exceeds a predetermined threshold.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] For example, vehicles such as electric vehicles and hybrid vehicles are equipped with a high-voltage, large-capacity battery for supplying power to a motor that serves as a power source. This battery includes a battery module made up of a plurality of cells connected in series. Patent Document 1 discloses a battery monitoring IC (Integrated Circuit) that monitors the voltage of such a battery. The battery monitoring IC of Patent Document 1 is provided with a power supply voltage input terminal to which the power supply voltage of the battery module is input, and a cell voltage terminal to which the voltage of each cell is input. The battery monitoring IC detects the power supply voltage and cell voltage of the battery based on signals input from the power supply voltage input terminal and the cell voltage terminal. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-49239 A Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, a power supply voltage input line is connected to the power supply voltage input terminal of a module voltage detection circuit such as a battery monitoring IC as disclosed in Patent Document 1, and a cell voltage input line is connected to the cell voltage terminal. For example, the voltage of the highest (positive electrode side) cell (top cell) among a plurality of cells included in a battery module is input to the module voltage detection circuit via a top cell voltage input line, which is one of the cell voltage input lines.

[0005] A time constant circuit for noise removal, etc. is provided at an intermediate position of each of the power supply voltage input lines and the cell voltage input lines. The time constant of the time constant circuit provided on the power supply voltage input line and the time constant circuit provided on the cell voltage input line may differ due to differences in the required noise removal level, etc.

[0006] However, both the power supply voltage input line and the top cell voltage input line are connected to the positive terminal of the battery module. Therefore, if the time constant of the time constant circuit provided in the power supply voltage input line differs from the time constant of the time constant circuit provided in the cell voltage input line, when the voltage of the top cell drops sharply, a large temporary potential difference occurs between the voltage of the power supply voltage input line and the top cell voltage input line due to the difference in response speed of the time constant circuits. As a result, the module voltage detection circuit may erroneously determine that there is an abnormality even when there is no abnormality, which may affect voltage detection.

[0007] The present invention has been made in consideration of the above-mentioned problems, and aims to prevent the potential difference between the power supply voltage input line and the top cell voltage input line from increasing beyond a threshold when the voltage of the top cell drops, due to the difference in time constant between the time constant circuit provided in the power supply voltage input line and the time constant circuit provided in the top cell voltage input line. [Means for solving the problem]

[0008] The present invention employs the following configuration as a means for solving the above problems.

[0009] A first aspect of the present invention is a voltage detection device that detects the voltage of a battery module having a plurality of cells connected in series, comprising: a module voltage detection circuit having a power supply voltage input terminal to which the power supply voltage of the battery module is input and a plurality of cell voltage input terminals to which the voltages of the cells are input; a power supply voltage input line having a time constant circuit for power supply voltage provided at an intermediate portion and connected to the power supply voltage input terminal; a top cell voltage input line having a time constant circuit for cell voltage provided at an intermediate portion and inputting the voltage of the topmost cell to the cell voltage input terminal; and a switching circuit that connects a portion of the power supply voltage input line closer to the module voltage detection circuit than the time constant circuit for power supply voltage and a portion of the top cell voltage input line closer to the module voltage detection circuit than the time constant circuit for cell voltage, wherein the switching circuit is configured to pass a current when a potential difference between the power supply voltage input line and the top cell voltage input line exceeds a predetermined threshold.

[0010] A second aspect of the present invention employs a configuration in which, in the first aspect, the power supply voltage time constant circuit is designed to have a smaller time constant than the cell voltage time constant circuit.

[0011] A third aspect of the present invention is the same as the second aspect, in which the switching circuit is provided with a switching diode having a cathode connected to the power supply voltage input line and an anode connected to the top cell voltage input line.

[0012] A fourth aspect of the present invention is the same as the third aspect, in which the switching circuit includes a second switching diode having an anode connected to the power supply voltage input line and a cathode connected to the top cell voltage input line.

[0013] A fifth aspect of the present invention employs a configuration in which, in any one of the first to fourth aspects, a transistor is provided as the switching circuit. Effect of the Invention

[0014] According to the present invention, when the voltage of the top cell drops and the potential difference between the power supply voltage input line and the top cell voltage input line exceeds a threshold, a current flows through the switching circuit, and the potential difference between the power supply voltage input line and the top cell voltage input line is prevented from increasing. Therefore, it is possible to suppress the potential difference between the power supply voltage input line and the top cell voltage input line from increasing beyond the threshold when the voltage of the top cell drops, due to the difference in time constant between the time constant circuit provided in the power supply voltage input line and the time constant circuit provided in the top cell voltage input line. [Brief description of the drawings]

[0015] [Figure 1] 1 is a schematic configuration diagram of a voltage detection device according to a first embodiment of the present invention. [Diagram 2] 1 is a timing chart showing the time changes of the voltage input to the power supply voltage input terminal, the voltage input to the top cell voltage input terminal, and the value obtained by subtracting the voltage input to the top cell voltage input terminal from the voltage input to the power supply voltage input terminal when the voltage of the top cell of a battery module M drops sharply. [Diagram 3] FIG. 6 is a schematic configuration diagram of a voltage detection device according to a second embodiment of the present invention. [Figure 4] FIG. 11 is a schematic configuration diagram of a voltage detection device according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a voltage detection device according to the present invention will be described with reference to the drawings.

[0017] (First embodiment) Fig. 1 is a schematic configuration diagram of a voltage detection device 1 of this embodiment. The voltage detection device 1 of this embodiment is mounted on, for example, an electric vehicle or a hybrid vehicle, and detects the voltage of a battery module M. As shown in Fig. 1, the voltage detection device 1 of this embodiment includes a module voltage detection circuit 10, a cell voltage input line 20, a power supply voltage input line 30, a cell voltage filter circuit 40 (a time constant circuit for cell voltage), a power supply voltage filter circuit 50 (a time constant circuit for power supply voltage), and a switching diode 60 (a switching circuit).

[0018] A plurality of battery modules M whose voltages are detected by the voltage detection device 1 of this embodiment are provided for one battery, for example. These battery modules M are connected in series. In other words, one battery is provided with a plurality of battery modules M connected in series. The voltage detection device 1 of this embodiment is provided for each of the plurality of battery modules M provided for one battery.

[0019] As shown in FIG. 1, the battery module M has a plurality of cells C connected in series. The battery module M has a positive electrode terminal and a negative electrode terminal. The positive electrode terminal side of the battery module M is referred to as the upper side, and the negative electrode terminal side of the battery module M is referred to as the lower side. Of the plurality of cells C, the cell C arranged on the uppermost side (the positive electrode terminal side of the battery module M) is referred to as the uppermost cell Ca. The positive electrode of this uppermost cell Ca is directly connected to the positive electrode terminal of the battery module M and has the same potential as the positive electrode terminal of the battery module M.

[0020] The module voltage detection circuit 10 detects the voltage of each cell C (cell voltage) included in the battery module M and the overall voltage (power supply voltage) of the battery module M. The module voltage detection circuit 10 outputs these detection values ​​to, for example, a battery maintenance unit (not shown).

[0021] The module voltage detection circuit 10 has a plurality of terminals to which input lines that input signals to the module voltage detection circuit 10 are connected. In this embodiment, the module voltage detection circuit 10 has, as the above terminals, a power supply voltage input terminal VBAT and a cell voltage input terminal Cn. The module voltage detection circuit 10 also has a ground terminal GND.

[0022] The power supply voltage input terminal VBAT is a terminal to which the power supply voltage input line 30 is connected. A signal indicating the potential of the positive terminal of the battery module M (a signal indicating the power supply voltage) is input via the power supply voltage input line 30 to the power supply voltage input terminal VBAT.

[0023] A plurality of cell voltage input terminals Cn are provided. Each cell voltage input terminal Cn is a terminal to which a cell voltage input line 20 is connected. A signal indicating the voltage of each cell C (a signal indicating the potential of the electrode of cell C) is input to the cell voltage input terminal Cn via the cell voltage input line 20. Among the plurality of cell voltage input terminals Cn, the terminal to which the potential of the positive electrode of the top cell Ca is input is referred to as the top cell voltage input terminal C1.

[0024] The ground terminal GND is a terminal connected to the negative terminal of the battery module M. A negative wiring 70 is connected to the ground terminal GND. This negative wiring 70 is a wiring that connects the negative terminal of the battery module M and the ground terminal GND.

[0025] Such a module voltage detection circuit 10 is an integrated circuit that operates using the power supply voltage of the battery module M supplied to a power supply voltage input terminal VBAT and a ground terminal GND as a power source. The module voltage detection circuit 10 detects the power supply voltage based on the potential of the positive electrode of the battery module M input to the power supply voltage input terminal VBAT and the potential of the negative electrode of the battery module M input to the ground terminal GND. The module voltage detection circuit 10 also detects the voltage between the electrodes of each cell C (cell voltage) based on the electrode voltage of the cell C input from the cell voltage input line 20.

[0026] Furthermore, in this embodiment, the module voltage detection circuit 10 determines that an abnormality has occurred when the value obtained by subtracting the potential input to the highest cell voltage input terminal C1 from the potential input to the power supply voltage input terminal VBAT falls below -2 V. Note that the calculation of subtracting the potential input to the highest cell voltage input terminal C1 from the potential input to the power supply voltage input terminal VBAT and the determination of the presence or absence of an abnormality may be performed by a battery maintenance unit or the like.

[0027] The cell voltage input line 20 is a wiring that connects the electrode of the cell C to the cell voltage input terminal Cn of the module voltage detection circuit 10, and a plurality of cell voltage input lines 20 are provided. Of the plurality of cell voltage input lines 20, the cell voltage input line 20 connected to the positive electrode of the top cell Ca is referred to as the top cell voltage input line 21. In other words, the top cell voltage input line 21 connects the positive electrode of the top cell Ca to the top cell voltage input terminal C1 of the module voltage detection circuit 10.

[0028] The power supply voltage input line 30 is a wiring that connects the positive electrode of the battery module M (i.e., the positive electrode of the top cell Ca) and the power supply voltage input terminal VBAT of the module voltage detection circuit 10. As shown in FIG. 1, one end of the power supply voltage input line 30 is directly connected to the power supply voltage input terminal VBAT. Meanwhile, the other end of the power supply voltage input line 30 is connected to a portion of the top cell voltage input line 21 that is closer to the battery module M than the cell voltage filter circuit 40. In other words, the other end of the power supply voltage input line 30 is connected to the positive electrode of the top cell Ca (i.e., the positive electrode of the battery module M) via the top cell voltage input line 21.

[0029] 1, a cell voltage filter circuit 40 is provided at a midpoint of each cell voltage input line 20. In addition, a power supply voltage filter circuit 50 is provided at a midpoint of the power supply voltage input line 30.

[0030] The cell voltage filter circuit 40 is a low-pass filter (RC circuit) that removes high-frequency noise contained in the voltage signal flowing through the cell voltage input line 20. In this embodiment, the cell voltage filter circuit 40 is composed of a resistor and a capacitor.

[0031] The power supply voltage filter circuit 50 is a low-pass filter (RC circuit) that removes high-frequency noise contained in the voltage signal flowing through the power supply voltage input line 30. In this embodiment, the power supply voltage filter circuit 50 is composed of a resistor and a capacitor.

[0032] In this embodiment, the power supply voltage filter circuit 50 is designed to have a smaller time constant than the cell voltage filter circuit 40. In other words, the power supply voltage filter circuit 50 is designed such that the resistance values ​​of the resistors and the capacitances of the capacitors are such that the time constant of the power supply voltage filter circuit 50 is smaller than the time constant of the cell voltage filter circuit 40.

[0033] For this reason, the cell voltage filter circuit 40 has a higher noise removal level than the power supply voltage filter circuit 50. On the other hand, the cell voltage filter circuit 40 has a slower response speed of the output signal to changes in the input signal than the power supply voltage filter circuit 50.

[0034] The switching diode 60 is a diode whose cathode is connected to the power supply voltage input line 30 and whose anode is connected to the top cell voltage input line 21. The switching diode 60 connects a portion of the power supply voltage input line 30 closer to the module voltage detection circuit 10 than the power supply voltage filter circuit 50 and a portion of the top cell voltage input line 21 closer to the module voltage detection circuit 10 than the cell voltage filter circuit 40.

[0035] For example, a silicon diode in which a voltage drop of about 0.7 V occurs between the anode and cathode is used as this switching diode 60. When a silicon diode is used as the switching diode 60, the switching diode 60 passes a current from the top cell voltage input line 21 to the power supply voltage input line 30 when the potential of the top cell voltage input line 21 becomes about 0.7 V or more higher than the potential of the power supply voltage input line 30.

[0036] In other words, the switching diode 60 passes a current when the potential difference between the power supply voltage input line 30 and the top cell voltage input line 21 exceeds a predetermined threshold. By passing a current through the switching diode 60 in this manner, the potential difference between the power supply voltage input line 30 and the top cell voltage input line 21 is prevented from increasing beyond the predetermined threshold.

[0037] The voltage detection device 1 detects the power supply voltage of the battery module M and the cell voltage of each cell C based on voltage signals input from the power supply voltage input line 30, the cell voltage input line 20, and the negative electrode wiring .

[0038] Figure 2 is a timing chart showing the changes over time in the voltage input to the power supply voltage input terminal VBAT, the voltage input to the top cell voltage input terminal C1, and the value obtained by subtracting the voltage input to the top cell voltage input terminal C1 from the voltage input to the power supply voltage input terminal VBAT when the voltage of the top cell Ca of the battery module M drops sharply.

[0039] In Figure 2, (a) shows the changes over time of the voltage of the top cell Ca in the voltage detection device 1 of this embodiment, the voltage input to the power supply voltage input terminal VBAT, the voltage input to the top cell voltage input terminal C1, and the value obtained by subtracting the voltage input to the top cell voltage input terminal C1 from the voltage input to the power supply voltage input terminal VBAT.

[0040] In addition, in Figure 2, (b) shows, for comparison, the changes over time of the voltage of the top cell Ca in a configuration in which the switching diode 60 is removed from the voltage detection device 1 of this embodiment, the voltage input to the power supply voltage input terminal VBAT, the voltage input to the top cell voltage input terminal C1, and the value obtained by subtracting the voltage input to the top cell voltage input terminal C1 from the voltage input to the power supply voltage input terminal VBAT.

[0041] In the voltage detection device 1 of this embodiment, the switching diode 60 passes a current when the potential difference between the power supply voltage input line 30 and the top cell voltage input line 21 exceeds a predetermined threshold. Therefore, as shown in FIG. 2(a), even if the power supply voltage filter circuit 50 has a different time constant than the cell voltage filter circuit 40, the voltage input to the power supply voltage input terminal VBAT and the voltage input to the top cell voltage input terminal C1 decrease at the same rate over time. As a result, the value obtained by subtracting the voltage input to the top cell voltage input terminal C1 from the voltage input to the power supply voltage input terminal VBAT does not exceed the threshold (−0.7V in FIG. 2).

[0042] On the other hand, when the switching diode 60 is not provided, the time constant of the power supply voltage filter circuit 50 is smaller than the time constant of the cell voltage filter circuit 40, so that the voltage input to the power supply voltage input terminal VBAT drops in a shorter time than the voltage input to the top cell voltage input terminal C1, as shown in FIG. 2(b). Furthermore, the value obtained by subtracting the voltage input to the top cell voltage input terminal C1 from the voltage input to the power supply voltage input terminal VBAT increases. As a result, the value obtained by subtracting the voltage input to the top cell voltage input terminal C1 from the voltage input to the power supply voltage input terminal VBAT falls below -2V, at which the module voltage detection circuit 10 determines that an abnormality has occurred.

[0043] As can be seen by comparing Figures 2(a) and 2(b), the voltage detection device 1 of this embodiment can prevent the difference between the voltage input to the power supply voltage input terminal VBAT and the voltage input to the top cell voltage input terminal C1 from increasing, even if the voltage of the top cell Ca of the battery module M drops sharply.

[0044] The voltage detection device 1 of this embodiment as described above detects the voltage of a battery module M having a plurality of cells C connected in series. The voltage detection device 1 of this embodiment also includes a module voltage detection circuit 10. The module voltage detection circuit 10 has a power supply voltage input terminal VBAT to which the power supply voltage of the battery module M is input, and a plurality of cell voltage input terminals Cn to which the voltages of the cells C are input.

[0045] The voltage detection device 1 of this embodiment also includes a power supply voltage input line 30. A power supply voltage filter circuit 50 is provided in the middle of the power supply voltage input line 30, and the power supply voltage input line 30 is connected to a power supply voltage input terminal VBAT. The voltage detection device 1 of this embodiment also includes a top cell voltage input line 21. A cell voltage filter circuit 40 is provided in the middle of the top cell voltage input line 21, and the voltage of the top cell C is input to a cell voltage input terminal Cn.

[0046] The voltage detection device 1 of this embodiment also includes a switching diode 60. The switching diode 60 connects a portion of the power supply voltage input line 30 closer to the module voltage detection circuit 10 than the power supply voltage filter circuit 50 and a portion of the top cell voltage input line 21 closer to the module voltage detection circuit 10 than the cell voltage filter circuit 40. The switching diode 60 also passes a current when the potential difference between the power supply voltage input line 30 and the top cell voltage input line 21 exceeds a predetermined threshold value.

[0047] According to the voltage detection device 1 of this embodiment, when the voltage of the top cell Ca drops and the potential difference between the power supply voltage input line 30 and the top cell voltage input line 21 exceeds a threshold value, a current flows through the switching diode 60, preventing the potential difference between the power supply voltage input line 30 and the top cell voltage input line 21 from increasing. Therefore, it is possible to prevent the potential difference between the power supply voltage input line 30 and the top cell voltage input line 21 from increasing beyond a threshold value when the voltage of the top cell Ca drops, due to the difference in time constant between the time constant circuit provided in the power supply voltage input line 30 and the time constant circuit provided in the top cell voltage input line 21.

[0048] Furthermore, in the voltage detection device 1 of this embodiment, the power supply voltage filter circuit 50 is designed to have a smaller time constant than the cell voltage filter circuit 40. This determines the magnitude relationship between the time constants of the power supply voltage filter circuit 50 and the cell voltage filter circuit 40, and also determines the level of the potential between the cell voltage input line 20 and the power supply voltage input line 30 when the voltage of the top cell Ca drops. This makes it possible to use switching diodes, which do not require control, as the switching circuit, instead of transistors, which require control.

[0049] Furthermore, in the voltage detection device 1 of this embodiment, a switching diode 60 is provided as a switching circuit, the cathode of which is connected to the power supply voltage input line 30 and the anode of which is connected to the top cell voltage input line 21. According to the voltage detection device 1 of this embodiment, since there is no need to control the switching circuit, it is possible to prevent the potential difference between the power supply voltage input line 30 and the top cell voltage input line 21 from increasing beyond a threshold value when the voltage of the top cell Ca drops, without complicating the control of the voltage detection device 1.

[0050] Second embodiment Next, a second embodiment of the present invention will be described. In the description of this embodiment, the description of the same parts as those in the first embodiment will be omitted or simplified.

[0051] 3 is a schematic diagram of a voltage detecting device 1A of this embodiment. As shown in this figure, the voltage detecting device 1A of this embodiment further includes a second switching diode 61 in addition to the components of the voltage detecting device 1 of the first embodiment.

[0052] The second switching diode 61 is a diode whose anode is connected to the power supply voltage input line 30 and whose cathode is connected to the top cell voltage input line 21. Like the switching diode 60, the second switching diode 61 also connects a portion of the power supply voltage input line 30 closer to the module voltage detection circuit 10 than the power supply voltage filter circuit 50 and a portion of the top cell voltage input line 21 closer to the module voltage detection circuit 10 than the cell voltage filter circuit 40.

[0053] In other words, in this embodiment, a switching diode 60 and a second switching diode 61 are connected in parallel at a portion of the power supply voltage input line 30 closer to the module voltage detection circuit 10 than the power supply voltage filter circuit 50, and at a portion of the top cell voltage input line 21 closer to the module voltage detection circuit 10 than the cell voltage filter circuit 40.

[0054] As the second switching diode 61, a silicon diode in which a voltage drop of about 0.7 V occurs between the anode and cathode is used, similar to the switching diode 60. When a silicon diode is used as the second switching diode 61, the second switching diode 61 passes a current from the power supply voltage input line 30 to the top cell voltage input line 21 when the potential of the power supply voltage input line 30 becomes about 0.7 V or more higher than the potential of the top cell voltage input line 21.

[0055] In other words, the second switching diode 61 passes a current when the potential difference between the power supply voltage input line 30 and the top cell voltage input line 21 exceeds a predetermined threshold. By passing a current through the second switching diode 61 in this manner, the potential difference between the power supply voltage input line 30 and the top cell voltage input line 21 is prevented from increasing beyond the predetermined threshold.

[0056] In the voltage detection device 1A of this embodiment, even if the time constant of the power supply voltage filter circuit 50 becomes larger than that of the cell voltage filter circuit 40 due to some kind of malfunction or the like, the potential difference between the power supply voltage input line 30 and the top cell voltage input line 21 is prevented from increasing beyond a predetermined threshold value.

[0057] A more detailed explanation will be given. In the voltage detection device 1A of this embodiment, it is assumed that the time constant of the power supply voltage filter circuit 50 becomes larger than that of the cell voltage filter circuit 40 due to some cause. In such a case, when the voltage of the top cell Ca drops sharply, the potential of the power supply voltage input line 30 becomes higher than that of the top cell voltage input line 21 due to the difference between the time constant of the power supply voltage filter circuit 50 and the time constant of the cell voltage filter circuit 40. When this potential difference exceeds a predetermined threshold (the voltage at which the second switching diode 61 passes a current), the second switching diode 61 passes a current, and the potential difference between the power supply voltage input line 30 and the top cell voltage input line 21 is prevented from expanding beyond the predetermined threshold.

[0058] On the other hand, suppose that there is no cause such as a failure, and the time constant of the power supply voltage filter circuit 50 is smaller than that of the cell voltage filter circuit 40. In this case, when the voltage of the top cell Ca drops sharply, the difference between the time constant of the power supply voltage filter circuit 50 and the time constant of the cell voltage filter circuit 40 causes the potential of the top cell voltage input line 21 to be higher than the potential of the power supply voltage input line 30. When this potential difference exceeds a predetermined threshold (the voltage at which the switching diode 60 passes current), the switching diode 60 passes current, preventing the potential difference between the power supply voltage input line 30 and the top cell voltage input line 21 from expanding beyond the predetermined threshold.

[0059] Thus, in the voltage detection device 1A of this embodiment, even if the time constant of the power supply voltage filter circuit 50 is larger than that of the cell voltage filter circuit 40, or even if the time constant of the power supply voltage filter circuit 50 is smaller than that of the cell voltage filter circuit 40, the potential difference between the power supply voltage input line 30 and the top cell voltage input line 21 is prevented from increasing beyond a predetermined threshold.

[0060] As described above, in the voltage detection device 1A of the present embodiment, a second switching diode 61 is provided as a switching circuit, the anode of which is connected to the power supply voltage input line 30 and the cathode of which is connected to the top cell voltage input line 21. According to the voltage detection device 1 of the present embodiment, as described above, the potential difference between the power supply voltage input line 30 and the top cell voltage input line 21 is prevented from increasing beyond a predetermined threshold, regardless of the magnitude relationship between the time constant of the power supply voltage filter circuit 50 and the time constant of the cell voltage filter circuit 40.

[0061] In the voltage detection device 1A of this embodiment, a case has been described in which an unforeseen event such as a failure causes the time constant of the power supply voltage filter circuit 50 to become larger than that of the cell voltage filter circuit 40. However, it is also possible to make the time constant of the power supply voltage filter circuit 50 and / or the cell voltage filter circuit 40 variable, and to control the time constant of the power supply voltage filter circuit 50 to be larger than that of the cell voltage filter circuit 40.

[0062] Third embodiment Next, a third embodiment of the present invention will be described. In the description of this embodiment, the description of the same parts as those in the first embodiment will be omitted or simplified.

[0063] 4 is a schematic diagram of a voltage detecting device 1B of the present embodiment. As shown in this figure, the voltage detecting device 1B of the present embodiment includes a transistor 62 instead of the switching diode 60 of the voltage detecting device 1 of the first embodiment.

[0064] For example, a bipolar transistor can be used as the transistor 62. For example, when an NPN transistor is used, the collector terminal of the transistor 62 is connected to the top cell voltage input line 21, and the emitter terminal is connected to the power supply voltage input line 30, as shown in Fig. 4. When a PNP transistor is used, the emitter terminal is connected to the top cell voltage input line 21, and the collector terminal is connected to the power supply voltage input line 30.

[0065] In addition, the transistor 62 connects a portion of the power supply voltage input line 30 closer to the module voltage detection circuit 10 than the power supply voltage filter circuit 50 and a portion of the top cell voltage input line 21 closer to the module voltage detection circuit 10 than the cell voltage filter circuit 40.

[0066] Furthermore, the base terminal of the transistor 62 is connected to, for example, the module voltage detection circuit 10. That is, the transistor 62 is driven based on a drive signal input from the module voltage detection circuit 10 to the base terminal.

[0067] For example, when the potential of the top cell voltage input line 21 becomes 0.7 V higher than the potential of the power supply voltage input line 30, the module voltage detection circuit 10 inputs a drive signal to the base terminal of the transistor 62. As a result, a current flows through the transistor 62.

[0068] That is, the transistor 62 passes a current when the potential difference between the power supply voltage input line 30 and the top cell voltage input line 21 exceeds a predetermined threshold. By passing a current through the switching diode 60 in this manner, the potential difference between the power supply voltage input line 30 and the top cell voltage input line 21 is prevented from increasing beyond the predetermined threshold.

[0069] According to the voltage detection device 1B of this embodiment, when the voltage of the top cell Ca drops and the potential difference between the power supply voltage input line 30 and the top cell voltage input line 21 exceeds a threshold value, a current flows through the transistor 62, preventing the potential difference between the power supply voltage input line 30 and the top cell voltage input line 21 from increasing. This makes it possible to prevent the potential difference between the power supply voltage input line 30 and the top cell voltage input line 21 from increasing beyond a threshold value when the voltage of the top cell Ca drops, due to the difference in time constant between the time constant circuit provided in the power supply voltage input line 30 and the time constant circuit provided in the top cell voltage input line 21.

[0070] In this embodiment, a transistor 62 is provided as a switching circuit. Therefore, it is possible to arbitrarily set the potential difference at which the transistor 62 passes a current (the potential difference between the power supply voltage input line 30 and the top cell voltage input line 21).

[0071] Although the preferred embodiment of the present invention has been described above with reference to the attached drawings, it goes without saying that the present invention is not limited to the above embodiment. The shapes and combinations of the components shown in the above embodiment are merely examples, and various modifications can be made based on design requirements, etc., without departing from the spirit of the present invention.

[0072] For example, in the above first embodiment, a configuration has been described in which the power supply voltage filter circuit 50 is designed to have a smaller time constant than the cell voltage filter circuit 40. However, the present invention is not limited to this. It is also possible to adopt a configuration in which the power supply voltage filter circuit 50 is designed to have a larger time constant than the cell voltage filter circuit 40. In such a case, the switching circuit passes a current from the power supply voltage input line 30 to the highest cell voltage input line 21 when the potential difference between the power supply voltage input line 30 and the highest cell voltage input line 21 exceeds a predetermined threshold value. [Explanation of symbols]

[0073] 1 ...... voltage detection device, 1A ...... voltage detection device, 1B ...... voltage detection device, 10 ...... module voltage detection circuit, 20 ...... cell voltage input line, 21 ...... top cell voltage input line, 30 ...... power supply voltage input line, 40 ...... cell voltage filter circuit (cell voltage time constant circuit), 50 ...... power supply voltage filter circuit (power supply voltage time constant circuit), 60 ...... switching diode (switching circuit), 61 ...... second switching diode (switching circuit), 62 ...... transistor (switching circuit), 70 ...... negative wiring, C ...... cell, C1 ...... top cell voltage input terminal, Ca ...... top cell, Cn ...... cell voltage input terminal, M ...... battery module, VBAT ...... power supply voltage input terminal

Claims

1. A voltage detection device for detecting a voltage of a battery module having a plurality of cells connected in series, a module voltage detection circuit having a power supply voltage input terminal to which a power supply voltage of the battery module is input and a plurality of cell voltage input terminals to which voltages of the cells are input; a power supply voltage input line provided with a power supply voltage time constant circuit at a midpoint and connected to the power supply voltage input terminal; A top cell voltage input line having a cell voltage time constant circuit provided in the middle and inputting the voltage of the top cell to the cell voltage input terminal; a switching circuit that connects a portion of the power supply voltage input line closer to the module voltage detection circuit than the power supply voltage time constant circuit and a portion of the top cell voltage input line closer to the module voltage detection circuit than the cell voltage time constant circuit; Equipped with The switching circuit allows a current to flow when a potential difference between the power supply voltage input line and the top cell voltage input line exceeds a predetermined threshold. A voltage detection device comprising:

2. 2. The voltage detection device according to claim 1, wherein the power supply voltage time constant circuit is designed to have a time constant smaller than that of the cell voltage time constant circuit.

3. 3. The voltage detection device according to claim 2, wherein the switching circuit comprises a switching diode having a cathode connected to the power supply voltage input line and an anode connected to the highest cell voltage input line.

4. 4. The voltage detection device according to claim 3, further comprising a second switching diode, the second switching diode having an anode connected to the power supply voltage input line and a cathode connected to the highest cell voltage input line, as the switching circuit.

5. 3. The voltage detection device according to claim 1, wherein the switching circuit is provided with a transistor.

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