JP7675308B2 - Voltage Detector - Google Patents

Description

The present invention relates to a voltage detection device.

For example, vehicles such as electric vehicles and hybrid vehicles are equipped with high-voltage, large-capacity batteries to supply power to the motor that serves as the power source. This battery has a battery module consisting of multiple 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 in 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.

JP 2017-49239 A

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) cell (top cell) among multiple 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.

A time constant circuit for noise removal, etc. is provided at each of the intermediate positions of the power supply voltage input line and the cell voltage input line. 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.

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 none, which may affect voltage detection.

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.

The present invention adopts the following configuration as a means for solving the above problems.

The 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 power supply voltage time constant circuit provided at an intermediate portion and connected to the power supply voltage input terminal; a top cell voltage input line having a cell voltage time constant circuit provided at an intermediate portion and inputting the voltage of the top 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 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, and the switching circuit is configured to pass a current when the potential difference between the power supply voltage input line and the top cell voltage input line exceeds a predetermined threshold.

The second aspect of the present invention is the first aspect, but with the power supply voltage time constant circuit designed to have a smaller time constant than the cell voltage time constant circuit.

The third aspect of the present invention is the second aspect, in which the switching circuit is a switching diode whose cathode is connected to the power supply voltage input line and whose anode is connected to the top cell voltage input line.

The fourth aspect of the present invention is the third aspect, in which the switching circuit includes a second switching diode whose anode is connected to the power supply voltage input line and whose cathode is connected to the top cell voltage input line.

The fifth aspect of the present invention is any one of the first to fourth aspects, in which a transistor is provided as the switching circuit.

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 value, 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 prevent the potential difference between the power supply voltage input line and the top cell voltage input line from increasing beyond the 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 top cell voltage input line.

1 is a schematic configuration diagram of a voltage detection device according to a first embodiment of the present invention; 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. FIG. 6 is a schematic configuration diagram of a voltage detection device according to a second embodiment of the present invention. FIG. 11 is a schematic configuration diagram of a voltage detection device according to a third embodiment of the present invention.

Below, one embodiment of a voltage detection device according to the present invention will be described with reference to the drawings.

First Embodiment
Fig. 1 is a schematic 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).

The battery modules M whose voltages are detected by the voltage detection device 1 of this embodiment are provided, for example, for one battery. These battery modules M are connected in series. In other words, one battery has multiple battery modules M connected in series. The voltage detection device 1 of this embodiment is provided for each of the multiple battery modules M provided for one battery.

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

The module voltage detection circuit 10 detects the voltage of each cell C (cell voltage) 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).

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 the power supply voltage input terminal VBAT and the cell voltage input terminal Cn as the above terminals. The module voltage detection circuit 10 also has a ground terminal GND.

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 to the power supply voltage input terminal VBAT via the power supply voltage input line 30.

There are multiple cell voltage input terminals Cn. 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 multiple 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.

The ground terminal GND is a terminal that is connected to the negative terminal of the battery module M. The 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 to the ground terminal GND.

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 the power supply voltage input terminal VBAT and the 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.

In addition, in this embodiment, the module voltage detection circuit 10 determines that an abnormality has occurred if the value obtained by subtracting the potential input to the top 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 top 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, etc.

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 multiple cell voltage input lines 20 are provided. Of the multiple cell voltage input lines 20, the cell voltage input line 20 that is 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.

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.

As shown in FIG. 1, a cell voltage filter circuit 40 is provided at an intermediate portion of each cell voltage input line 20. Also, a power supply voltage filter circuit 50 is provided at an intermediate portion of the power supply voltage input line 30.

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.

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.

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 value of the resistor and the capacitance of the capacitor 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.

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.

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.

For example, a silicon diode that generates a voltage drop of about 0.7 V between the anode and cathode is used as the 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.

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.

Such a voltage detection device 1 detects the power supply voltage of the battery module M and the cell voltage of each cell C based on the voltage signals input from the power supply voltage input line 30, the cell voltage input line 20, and the negative electrode wiring 70.

Figure 2 is a timing chart showing the time change of 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.

In FIG. 2, (a) shows the time change 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.

In addition, in FIG. 2, (b) shows, for comparison, the time change 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.

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).

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 as shown in FIG. 2(b), 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. 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.

As can be seen by comparing FIG. 2(a) and FIG. 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.

The voltage detection device 1 of this embodiment as described above detects the voltage of a battery module M having multiple 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 multiple cell voltage input terminals Cn to which the voltages of the cells C are input.

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

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.

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.

In addition, 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. Therefore, the magnitude relationship between the time constants of the power supply voltage filter circuit 50 and the cell voltage filter circuit 40 is determined, and 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 is also determined. Therefore, it is possible to use a switching diode, which does not require control, as the switching circuit, instead of a transistor, which requires control.

In addition, 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. With the voltage detection device 1 of this embodiment, control of the switching circuit is not required, so the control of the voltage detection device 1 is not complicated, and 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 when the voltage of the top cell Ca drops.

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 of the first embodiment will be omitted or simplified.

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

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.

In other words, in this embodiment, the switching diode 60 and the second switching diode 61 are connected in parallel to 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 to 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.

As for this second switching diode 61, a silicon diode in which a voltage drop of about 0.7 V occurs between the anode and cathode, similar to the switching diode 60, is used. 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.

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.

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 failure, 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.

A more detailed explanation will be given. In the voltage detection device 1A of this embodiment, assume that the time constant of the power supply voltage filter circuit 50 becomes larger than that of the cell voltage filter circuit 40 for some reason. 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 current), the second switching diode 61 passes 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.

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.

In this way, 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.

As described above, in the voltage detection device 1A of this 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 this embodiment, as described above, 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, 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.

In the voltage detection device 1A of this embodiment, a case has been described in which the time constant of the power supply voltage filter circuit 50 becomes larger than that of the cell voltage filter circuit 40 due to an unforeseen event such as a failure. However, for example, it is also possible to make the time constant of either or both of the power supply voltage filter circuit 50 and 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.

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 of the first embodiment will be omitted or simplified.

Figure 4 is a schematic diagram of the voltage detection device 1B of this embodiment. As shown in this figure, the voltage detection device 1B of this embodiment has a transistor 62 instead of the switching diode 60 of the voltage detection device 1 of the first embodiment.

For example, a bipolar transistor can be used as the transistor 62. For example, when an NPN transistor is used, as shown in FIG. 4, 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. Note that 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.

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.

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 to the base terminal from the module voltage detection circuit 10.

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.

In other words, 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.

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, and the potential difference between the power supply voltage input line 30 and the top cell voltage input line 21 is prevented 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 the 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.

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

The above describes a preferred embodiment of the present invention with reference to the attached drawings, but 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.

For example, in the first embodiment, a configuration was described in which the power supply voltage filter circuit 50 was 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 top cell voltage input line 21 when the potential difference between the power supply voltage input line 30 and the top cell voltage input line 21 exceeds a predetermined threshold.

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 (5)

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,
The voltage detection device, wherein the switching circuit passes a current when a potential difference between the power supply voltage input line and the top cell voltage input line exceeds a predetermined threshold. The voltage detection device according to claim 1, characterized in that the time constant circuit for the power supply voltage is designed to have a smaller time constant than the time constant circuit for the cell voltage. The voltage detection device according to claim 2, characterized in that the switching circuit is provided with a switching diode whose cathode is connected to the power supply voltage input line and whose anode is connected to the top cell voltage input line. The voltage detection device according to claim 3, characterized in that the switching circuit includes a second switching diode whose anode is connected to the power supply voltage input line and whose cathode is connected to the top cell voltage input line. 3. The voltage detection device according to claim 1, wherein the switching circuit is provided with a transistor.

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