JP4180560B2 - Battery voltage measurement circuit - Google Patents

Description

  The present invention relates to a battery voltage measuring circuit for measuring a voltage of an assembled battery, and more particularly to a battery voltage measuring circuit for measuring a cell voltage while scanning an assembled battery in which a large number of cells are connected in series such as a fuel cell. .

  A fuel cell is a cell that generates an electromotive force by electrochemically reacting a fuel gas mainly composed of hydrogen with oxygen. Since the cell voltage of such a fuel cell is about 1V, in general, one fuel cell stack is formed by connecting several hundred cells in series and used at a high voltage (for example, 260V). At this time, if the power generation of the fuel cell is continued with one cell in an extremely low voltage state (for example, a state of 0.5 V), the malfunctioning cell corrodes and the output voltage of the entire fuel cell is lowered. Or damage the fuel cell. Therefore, during operation of the fuel cell, the cell voltage is measured and monitored while scanning each cell constituting the fuel cell stack one by one or a plurality of cells sequentially. In other words, if one or more cells are damaged during operation of the fuel cell, the voltage of the corresponding cell is significantly reduced. Therefore, if the cell voltage is constantly measured and monitored, the occurrence of an abnormal cell is immediately observed. Therefore, it is possible to immediately stop the operation of the fuel cell and prevent the damage from expanding due to the detection delay of the abnormality.

  For this reason, various techniques for measuring the cell voltage of a fuel cell have been reported. FIG. 5 is a diagram showing an input circuit as a conventional battery voltage measuring circuit. As shown in FIG. 5, when the cells constituting the fuel cell are divided into a plurality of cell groups and, for example, the switches S31, S32, S33, and S34 of the first stage are simultaneously turned on in each cell group, the first stage Are detected by differential amplifiers D31, D32, and D33 of the input circuit 30 and transmitted to an A / D converter of a CPU (central processing unit) (not shown). The voltage of each cell is measured and monitored. Next, when the switches S31, S32, S33, and S34 of the first stage are simultaneously turned OFF and the switches S35, S36, S37, and S38 of the second stage are simultaneously turned ON, the voltages of the cells C34, C35, and C36 of the second stage are turned on. Are detected by the differential amplifiers D31, D32, and D33 and transmitted to an A / D converter of a CPU (not shown), and the voltage of each cell is measured and monitored by the CPU. In this way, when scanning is performed for each group while the switch groups of each stage are sequentially turned ON / OFF, the voltages of all the cells constituting the fuel cell can be measured.

  FIG. 6 is an explanatory diagram showing the polarity of the measurement voltage for each cell in the input circuit shown in FIG. That is, when the cell group of each stage is sequentially scanned as described above, as shown in FIG. 6, the voltage polarity of each cell is the same polarity in any stage and is supplied to each differential amplifier D31, D32, D33. Entered. Therefore, each of the differential amplifiers D31, D32, D33 can use a single power supply (that is, a unidirectional power supply in which one is a ground GND and the other is a positive power supply), and therefore the differential amplifiers D31, D32, D33. The configuration is simplified. The filters F31, F32, and F33 formed on each line of the input circuit 30 are elements for removing noise, and the buffers B31, B32, and B33 are elements for shaping the waveform of the detection voltage of each cell. It is.

Also, in a battery pack in which a large number of cells are connected in series, for example, a capacitor is connected in parallel for each cell corresponding to a plurality of five cells, and switches corresponding to each cell are sequentially switched. A voltage detection circuit technique for an assembled battery using a so-called flying capacitor method is disclosed, in which the voltage of each cell is applied to a corresponding capacitor and the voltage of each capacitor is measured to measure all cell voltages of the assembled battery. ing. According to this technique, the circuit configuration can be simplified (for example, see Patent Document 1). Furthermore, a technique is also disclosed in which, in an assembled battery in which a plurality of unit cells are connected in series, the voltage of the unit cells is sequentially measured using a plurality of switching means. According to this technique, the voltage of a single cell can be measured with high accuracy with a relatively simple configuration (see, for example, Patent Document 2).
JP-A-2002-156392 (see paragraph numbers 0051 to 0058 and FIG. 1) JP-A-11-237455 (see paragraph numbers 0018 to 0024 and FIGS. 1 and 2)

  However, in the input circuit as shown in FIG. 5, since a large number of cells are connected in series, more switches than the number of cells are required to measure the voltage of each cell individually. Specifically, a cell existing at the boundary position of each stage requires two switches in order to turn off the cell line of the previous stage and turn on the line of the next stage. For example, the cell C34 existing at one boundary position of the second stage requires two switches S34 and S35, and the cell C36 existing at the other boundary position of the second stage is two switches S38 and S39. Switch is required. From this, for example, when 180 cells are connected in series and three cells are combined in one stage, the number of switches is not limited to 181 but 181 + 180 ÷ 3-1 = 240 are also required. Since such a switch normally uses a high-breakdown-voltage photoMOS switch, the more the number of switches used, the higher the material cost. If the number of cells in one stage is increased, the number of switches corresponding to the cells existing at the boundary position of each stage can be reduced, so that the total number of switches can be slightly reduced. However, if the number of cells in one stage is increased, the number of filters, buffers, differential amplifiers, etc. in the input circuit 30 will increase, resulting in an increase in the material cost of the input circuit, that is, the battery voltage measurement circuit. It becomes.

  In addition, the assembled battery voltage detection circuit disclosed in the above-mentioned Patent Document 1 requires a capacitor for applying the voltage of each cell, although the circuit configuration by the switch is simplified. This will increase costs. Further, the assembled battery voltage detection circuit disclosed in Patent Document 2 also has problems such as a complicated circuit configuration of the switching means.

  The present invention has been made in view of the above problems, and when measuring a plurality of cell voltages at the same time, the number of switches is reduced as much as possible to perform efficient measurement with a simple circuit configuration. An object of the present invention is to provide a battery voltage measurement circuit that can be realized at low cost.

  The battery voltage measurement circuit of the present invention was created to achieve the above-described object, and scans the cell group of the assembled battery in which a plurality of cells are connected in series, and the voltage of each cell group. Battery voltage measuring circuit for measuring a plurality of open / close means connected in series to each signal line for outputting the voltage of each cell, and two signal lines existing at the boundary positions on both sides of the cell group And a plurality of voltage detecting means for detecting the voltage of each cell individually connected to each signal line corresponding to each cell of each cell group. . At this time, each time one of the two signal lines is grounded by the switching operation of the switching means, the voltage detection means can always detect a cell voltage having the same polarity.

  With such a circuit configuration, each switching means connected to the two signal lines existing at the boundary positions on both sides of the cell group is shared by two adjacent cells of the adjacent cell group. Therefore, the total number of switching means in the battery voltage measurement circuit can be reduced to the minimum necessary. Further, by sharing the opening / closing means, when detecting the voltage of each cell in the adjacent cell group, the cell voltage input to the voltage detecting means is reversed (that is, the positive electrode and the negative electrode are reversed). Entered. However, each time the cell group to be measured is switched, the signal line connected to the ground is also switched, so that apparently the cell voltage having the same polarity is always input to the voltage detection means. As a result, the voltage detecting means can be operated with a single power source of a unidirectional power source.

  According to the battery voltage measuring circuit of the present invention, by inverting the voltage polarity of adjacent cells for each cell group for measuring the cell voltage, it is possible to reduce the number of parts by sharing a switch between the cells, Moreover, even if the polarity of the cell voltage is reversed, the cell voltage with the same polarity can be detected by switching the grounded signal line, so that voltage measurement can be performed using a single power supply with a unidirectional voltage. It becomes. As a result, since a device (for example, a differential amplifier) that operates with a single power source can be used, the material cost of the battery voltage measurement circuit can be significantly reduced. In addition, every time the polarity of the cell group to be measured is inverted, the signal lines on both sides of the cell group are alternately switched and connected to the ground, so that scanning can be performed at a time compared to when the signal lines are not switched to the ground. The number of cells can be doubled. As a result, since multiple channels can be scanned at a higher speed, the cell voltage measurement of a cell group in which a large number of cells are connected in series like a fuel cell can be performed at a higher speed.

<< Summary of Invention >>
The battery voltage measuring circuit of the present invention is a fuel cell in which a large number of cells are connected in series, and one switch is provided by sharing a switch provided in a cell signal line at the boundary position of each stage for measuring a plurality of cells at once. To reduce the total number of switches. Furthermore, even if the switch is shared and the reverse voltage of the cell is input to the differential amplifier of the input circuit by scanning the previous stage cell group and the next stage cell group, the reference potential (ground potential) is always a negative potential signal. A switch is provided in the signal line of the negative potential of the cell at the boundary position of each stage so as to be a line, and connected to the ground GND. Each time the measurement stage is switched, these switches are switched to drop the negative potential signal line to the ground. That is, a switch is provided on the signal lines at both ends of one stage cell group, which is one detection step, and these switches are turned ON / OFF each time the stage for scanning the cell group (that is, the cell group) is switched. Thus, the signal lines at both ends are alternately connected to the ground GND.

  Thus, regardless of which stage cell group is scanned, in the differential amplifier of the input circuit, the negative input terminal of the operational amplifier serving as the measurement reference is determined as the reference potential (ground potential). Therefore, the differential amplifier can achieve normal operation with a single power supply without requiring both positive and negative power supplies. As a result, the number of switches in the entire battery voltage measuring circuit can be reduced, and the configuration of the differential amplifier can be simplified. Furthermore, by providing a changeover switch on the signal lines at both ends of the one-stage cell group, even if the signal line for detecting the cell voltage is disconnected, the number of cells in which voltage detection is impossible can be minimized.

<< Embodiment of the Invention >>
Hereinafter, the battery voltage measurement circuit of the present invention will be described in detail with reference to the drawings. When measuring the cell voltage of a fuel cell in which a large number of cells are connected in series, such as the voltage measurement of individual cells of a fuel cell, each cell group is divided into cell groups consisting of a plurality of cells, An efficient measurement method is to measure the voltages of individual cells in a cell group for each stage and scan to the cell group of the next stage. At this time, a switch is provided at a voltage measurement input terminal (that is, a signal line) of each cell in the cell group, and the measurement stage is sequentially scanned by collectively turning on / off the corresponding switch group for each stage. be able to. At this time, the switches provided in the signal line of the cell at the boundary position of each stage are not provided separately, such as the switch for the previous stage and the switch for the next stage, but a common switch. That is, even when the scan of the cell group of the previous stage is switched to the scan of the cell group of the next stage, the switch provided in the signal line of the cell at the boundary position is kept ON. With such a configuration, the number of switches can be reduced. Therefore, an embodiment of the battery voltage measuring circuit according to the present invention will be described below with such a configuration as a background.

Before describing the battery voltage measuring circuit according to the present invention, the circuit as the background of the present invention will be described. FIG. 1 is a circuit diagram showing a main part of an input circuit which shares a switch provided in a signal line of a cell at a boundary position of each stage, which is a precondition for the present invention. The input circuit 10 is connected to an A / D converter of a CPU that reads a voltage detection value as a battery voltage measurement circuit.
In FIG. 1, for convenience of explanation, a mode will be described in which three cells are used as one stage cell group, and the voltage of each cell is measured while scanning the cell group of each stage. However, the number of cells in the cell group in each stage is not limited to three, and the cell group in one stage may be configured with a larger number of cells. Naturally, if the number of cells in one stage cell group is increased, the measurement time of all cells is shortened.

  In FIG. 1, an input circuit 10 includes a part of cells C1 to C9 connected in series in a fuel cell in which a number of cells are connected in series. Each of the cells C1 to C9 includes cells C1, C2, and C3 that are first. The stage, cells C4, C5, and C6 are the second stage, and cells C7, C8, and C9 are the third stage, and a group of cells that are simultaneously measured is configured for each stage. Further, switches (opening / closing means) S1 to S10 are connected to the respective signal lines which are voltage measuring terminals of the cells C1 to C9. At this time, a common switch S4 is provided for the signal lines of the last cell C3 of the first stage and the first cell C4 of the second stage. Similarly, a common switch S7 is provided in the signal line of the last cell C6 of the second stage and the first cell C7 of the third stage. The negative signal line of the first cell C1 in the first stage is connected to the ground GND. Note that the switches S1 to S10 may be a photo MOS switch having a withstand voltage capable of withstanding the maximum voltage generated by the number of series cells of the fuel cell (for example, 260V when 200 cells are connected in series).

  Furthermore, the signal lines of the cell groups for each stage are connected to the input circuit 10 for taking in the voltages of the cell groups of each stage, and are induced by noise and each signal line when the switches S1 to S10 are turned on / off. Filters F1, F2, and F3 for removing generated noise, and buffers B1 that are connected in series to these filters F1, F2, and F3, and shape irregularities of rising waveforms and falling waveforms of detection voltage signals of the cells. B2 and B3 and the negative voltage and the positive voltage of each cell C1 to C9 are input to detect the voltage of each cell C1 to C9, and each differential is output to the A / D converter of the CPU (not shown). The amplifier (voltage detection means) D1, D2, D3 and a resistor R for adjusting the offset voltage of each differential amplifier D1, D2, D3 are provided. A resistor r provided between the output of each buffer B1, B2, B3 and the + input terminal of each differential amplifier D1, D2, D3 is a signal at the + input terminal of each differential amplifier D1, D2, D3. It is a resistance for adjusting the level.

  Next, an operation for measuring the voltages of the cells C1 to C9 by the input circuit 10 shown in FIG. 1 will be described. In the example of the input circuit shown in FIG. 1, when the switches S1 to S4 are simultaneously turned on, the voltages of the cells C1, C2, and C3 in the first stage are measured simultaneously. That is, the negative electrode potential of the cell C1 becomes the ground GND and is input to the negative input terminal of the differential amplifier D1, and the positive electrode potential of the cell C1 passes through the filter F1 and the buffer B1 to the positive input terminal of the differential amplifier D1. Is input. As a result, the voltage of the cell C1, which is the difference between the negative potential of the cell C1 and the positive potential of the cell C1, is output to the output terminal of the differential amplifier D1.

  Similarly, the negative potential of the cell C2 is input to the negative input terminal of the differential amplifier D2 via the filter F1 and the buffer B1, and the positive potential of the cell C2 is differentially changed via the filter F2 and the buffer B2. The signal is input to the + input terminal of the amplifier D2. As a result, the voltage of the cell C2, which is the difference between the negative potential of the cell C2 and the positive potential of the cell C2, is output to the output terminal of the differential amplifier D2. Similarly, the negative potential of the cell C3 is input to the negative input terminal of the differential amplifier D3 via the filter F2 and the buffer B2, and the positive potential of the cell C3 is changed via the filter F3 and the buffer B3. Input to the positive input terminal of the dynamic amplifier D3.

  As a result, the voltage of the cell C3, which is the difference between the negative potential of the cell C3 and the positive potential of the cell C3, is output to the output terminal of the differential amplifier D3. In this way, the voltages of the cells C1, C2, and C3 in the first stage are simultaneously measured by the differential amplifiers D1, D2, and D3 and taken into a CPU (not shown). Hereinafter, in this way, the voltage of the cell C1 is measured by the differential amplifier D1, the voltage of the cell C2 is measured by the differential amplifier D2, and the voltage of the cell C3 is measured by the differential amplifier D3 (hereinafter referred to as the cell). The measurement order of C1 → differential amplifier D1, cell C2 → differential amplifier D2, and cell C3 → differential amplifier D3) will be referred to as forward measurement.

  Next, when the voltage measurement of the first stage cells C1, C2, and C3 is finished and the voltage measurement of the second stage cells C4, C5, and C6 is started, the switch S4 is kept on, S1 to S3 are turned off at the same time, and switches S5 to S7 are turned on at the same time. That is, when the measurement is switched from the cell group of the first stage to the cell group of the second stage, the common switch S4 in the common signal line of the last cell C3 of the first stage and the first cell C4 of the second stage is It remains in the ON state. As a result of the ON / OFF operation of the switches, in the second stage cell group, the voltage of the cell C4 is measured by the differential amplifier D3, the voltage of the cell C5 is measured by the differential amplifier D2, and the voltage of the cell C6 is As measured by the differential amplifier D1, the corresponding order of the differential amplifiers is reversed from that of the first stage. Hereinafter, such a measurement order (that is, cell C4 → differential amplifier D3, cell C5 → differential amplifier D2, cell C6 → differential amplifier D1) will be referred to as backward measurement.

  The measurement of the second stage cells C4, C5, and C6 will be described in more detail. When the voltage measurement of the first stage cells C1, C2, and C3 is completed, the switches S1 to S3 are simultaneously turned off, the switch 4 is kept on, the switches S5 to S7 are simultaneously turned on, and the second stage cell C4 is turned on. , C5 and C6 are started. As a result, the negative potential of the cell C4 is input to the positive input terminal of the differential amplifier D3 via the filter F3 and the buffer B3, and the positive potential of the cell C4 is input to the differential amplifier via the filter F2 and the buffer B2. It is input to the negative input terminal of D3. As a result, the voltage of the cell C4, which is the difference between the negative potential of the cell C4 and the positive potential of the cell C4, is output to the output terminal of the differential amplifier D3.

  Similarly, the negative potential of the cell C5 is input to the positive input terminal of the differential amplifier D2 via the filter F2 and the buffer B2, and the positive potential of the cell C5 is differentially transmitted via the filter F1 and the buffer B1. The signal is input to the negative input terminal of the amplifier D2. As a result, the voltage of the cell C5, which is the difference between the negative potential of the cell C5 and the positive potential of the cell C5, is output to the output terminal of the differential amplifier D2. Similarly, the negative potential of the cell C6 is input to the positive input terminal of the differential amplifier D1 via the filter F1 and the buffer B1, and the positive potential of the cell C6 becomes the ground GND. -Input to the input terminal. As a result, the voltage of the cell C6, which is the difference between the negative potential of the cell C6 and the positive potential of the cell C6, is output to the output terminal of the differential amplifier D1. In this way, the voltages of the second stage cells C4, C5 and C6 are simultaneously measured by the differential amplifiers D3, D2 and D1 and taken into a CPU (not shown). That is, in the second stage, reverse measurement is performed such as cell C4 → differential amplifier D3, cell C5 → differential amplifier D2, and cell C6 → differential amplifier D1.

  Further, when the voltage measurement of the second stage cells C4, C5, C6 is completed, the switches S4 to S6 are simultaneously turned off, the switch 7 is kept on, and the switches S8 to S10 are simultaneously turned on to turn on the third stage. Measurement of the cells C7, C8, C9 is started. In the third stage, the same forward measurement as in the first stage is performed, such as cell C7 → differential amplifier D1, cell C8 → differential amplifier D2, and cell C9 → differential amplifier D3. In this way, the voltages of the third stage cells C7, C8, and C9 are simultaneously measured by the differential amplifiers D1, D2, and D3, and are taken into the CPU (not shown).

  As described above, when the voltages of the cells C1 to C9 are measured by the input circuit 10 shown in FIG. 1, the switch at the boundary position of each stage is shared, so that the conventional circuit as shown in FIG. The total number of switches can be reduced as compared with the input circuit 30. For example, if 180 cells are connected in series and 3 cells are combined as a single-stage cell group, the conventional input circuit 30 shown in FIG. 5 requires 240 switches. However, the number of switches in the case of the input circuit 10 shown in FIG. That is, 59 switches can be reduced compared to the prior art. In other words, the number of switches can be reduced by approximately the number of measurement stages.

  Although not directly related to the present invention, the A / of the CPU to which the output signals of the differential amplifiers D1, D2, and D3 (that is, the detection voltages of the respective cells) are input as measured by the input circuit 10 shown in FIG. When the voltage input to the D converter becomes negative, the specifications for the A / D converter become stricter. Therefore, such a state can be avoided by switching the offset voltage. For example, assuming that the electromotive force of the cell C is about 0 V to 1.3 V as in the case of a fuel cell, the offset voltage at the time of forward measurement is +1 V and the offset voltage at the time of backward measurement in the example of FIG. When + is set to + 5V, the voltage input to the A / D converter falls within the range of + 1V to + 5V, and the specification of the A / D converter can be made more gradual.

  Next, the voltage polarity of each cell taken into each differential amplifier D1, D2, D3 for each stage will be described with reference to the drawings. FIG. 2 is an explanatory diagram showing the polarity of the measurement voltage for each cell in the input circuit 10 shown in FIG. That is, when the voltage of each cell group is measured by turning on / off the switch group of each stage with the input circuit 10 as shown in FIG. 1, the detection of each cell for each stage with the polarity as shown in FIG. The voltage is input to each differential amplifier D1, D2, D3. That is, as shown in FIG. 2, the odd-numbered measurement stages such as the first stage and the third stage are in a state where the negative electrode of the cell (C1, C7, etc.) having the lowest potential is connected to the ground GND. The voltage of each cell (C1, C2, C3) in the forward direction is input to each differential amplifier D1, D2, D3. However, in the even-numbered measurement stage such as the second stage, each cell (C6, C5, C4) in the reverse direction is connected with the positive electrode of the cell having the highest potential (C6, etc.) connected to the ground. Input to each differential amplifier D1, D2, D3.

  As can be seen from FIG. 2, the polarities of the voltages input to the differential amplifiers D1, D2, and D3 are opposite in the odd-numbered stage and the even-numbered stage. Therefore, when measuring even-numbered stage cell groups and when measuring odd-numbered stage cell groups, the power supply voltages applied to the differential amplifiers D1, D2, and D3 must have opposite polarities. For example, each of the differential amplifiers D1, D2, and D3 requires a power supply of 0 to +5 V when measuring an odd-numbered stage cell group, but is 0 when measuring an even-numbered stage cell group. A -5V power supply is required. That is, each differential amplifier D1, D2, D3 requires both positive and negative power supplies (that is, both power supplies) in order to measure all the cells of the fuel cell. Therefore, the power supply circuit (not shown) in the input circuit 10 shown in FIG. 1 becomes complicated, and a differential amplifier for both power supplies that is more expensive than that of a single power supply must be used.

  Further, in the input circuit shown in FIG. 1, since the power supply voltage of each differential amplifier D1, D2, D3 is defined by the device rating, the number of channels that can be scanned at one time (within the range of the power supply voltage ( That is, the number of cells) is determined. For example, if the rated voltage of the differential amplifiers D1, D2, and D3 is 20Vmax and the cell voltage is 3V for one set of two cells, the number of cells that can be scanned at one time is 20V ÷ 2 ÷ 3V≈3 cells. That is, since the number of cells that can be scanned at one time is determined to be 3 cells, the number of cells in one stage cannot be increased in order to speed up the measurement time. In the input circuit 10 shown in FIG. 1, when a signal line connected to the ground among the common signal lines of each stage is broken due to disconnection or the like, for example, the signal of the switch S4 common to the first stage and the second stage If the line breaks due to disconnection or the like, it becomes impossible to measure the voltages of the six cells of the first stage cells C1, C2, and C3 and the second stage cells C4, C5, and C6.

  In the input circuit according to the present invention, the number of switches is reduced as shown in FIG. 1, and the negative voltage of the cell input to the differential amplifier serving as the measurement reference of the input circuit 10 is the reference regardless of which stage is scanned. A signal line connected to the ground GND is switched by a switch so that the potential (ground potential) is obtained. By doing so, the differential amplifier detects a cell voltage having the same polarity at any stage, so that a differential amplifier operating with a single power supply can be used. As a result, the cost of the input circuit, that is, the battery voltage measuring circuit can be further reduced. Further, even if a common signal line between the stages breaks due to disconnection or the like, it is possible to prevent measurement of all cells for two stages from being impossible and measurement of only a minimum number of cells.

  FIG. 3 is a circuit diagram showing an input circuit according to the present invention. That is, the input circuit (battery voltage measuring circuit) 10a shown in FIG. 3 switches (switching means) S11 for switching the ground GND of the signal line input to the input circuit 10a with respect to the input circuit 10 shown in FIG. , S12 is added. The other components are the same as the configuration of the input circuit 10 shown in FIG. Note that the newly added switches S11 and S12 have a breakdown voltage that can withstand the maximum voltage generated by the number of series cells of the fuel cell (for example, 260V in a series connection of 200 cells), similarly to the switches S1 to S10. The photo MOS switch can be used.

  That is, as shown in FIG. 3, the signal line (that is, the negative signal line of the first stage cell C1) is connected to the ground GND via the switch S11 from the signal line input to the negative input terminal of the differential amplifier D1. The signal line input to the + input terminal of the differential amplifier D3 (that is, the common signal line of the positive electrode of the first stage cell C3 and the negative electrode of the second stage cell C4) is connected to the ground GND via the switch S12. A new connection configuration has been added.

  With such a circuit configuration, each time the stage to be measured is changed, the switch S11 and the switch S12 are switched ON / OFF so that the signal lines are alternately connected to the ground GND. In other words, by alternately switching the switches S11 and S12 connected to the ground GND every time the stage to be measured changes, the reference potential (that is, the ground potential) of the cell voltage input for each stage to be measured becomes the upper and lower differentials. Move to the amplifier. In other words, the reference potential (that is, the ground potential) of the cell voltage input for each stage to be measured moves between the negative input terminal of the differential amplifier D1 and the positive input terminal of the differential amplifier D3.

  More specifically, each time the stage to be measured changes, the cell voltage input to the differential amplifiers D1, D2 and D3 changes from the cell C1 to the differential amplifier D1, the cell C2 to the differential amplifier D2, and the cell C3 to differential. Even if the forward direction of the amplifier D3 and the reverse direction of the cell C4 → the differential amplifier D3, the cell C5 → the differential amplifier D2, and the cell C6 → the differential amplifier D1 are changed, the differential amplifier on the side which is always the measurement reference is used. A negative potential is connected to the ground GND. In this way, the ground GND of the differential amplifiers D1, D2, and D3 is regulated in accordance with the cell measurement order. As a result, the power sources of the differential amplifiers D1, D2, and D3 are supplied with the reference potential (that is, A unidirectional power source (that is, a single power source) applied from the ground potential to one potential can be used.

  The operation of the input circuit 10a shown in FIG. 3 will be described in more detail. When measuring the cells C1, C2, C3 in the first stage, the switches S1, S2, S3, S4 and the switch S11 are turned on. As a result, forward measurement of cell C1 → differential amplifier D1, cell C2 → differential amplifier D2, cell C3 → differential amplifier D3 is performed, and the ground potential (reference potential) is- Since it is regulated by the input terminal, all the differential amplifiers D1, D2 and D3 can be operated with a single power supply having the same direction potential.

  Next, when the voltage measurement of the cells C1, C2, and C3 in the first stage is finished and the voltage measurement of the cells C4, C5, and C6 in the second stage is started, first, the switch S11 is turned off and the switch S12 is turned on. Is turned on. As a result, the signal line of the ground potential (reference potential) connected to the ground GND is switched to the signal line connected to the + input terminal of the differential amplifier D3. Further, the switch S4 is kept ON, the switches S1 to S3 are simultaneously turned OFF, the switches S5 to S7 are simultaneously turned ON, and the measurement of the second stage cell group is started.

  At this time, the reverse measurement of cell C4 → differential amplifier D3, cell C5 → differential amplifier D2, cell C6 → differential amplifier D1 is performed, but the ground potential (reference potential) is changed by the switch S12 to the differential amplifier D3. Therefore, all the differential amplifiers D1, D2, and D3 can be operated with a single power source having the same direction potential. In this way, even if the polarities of the cell voltages input to the differential amplifiers D1, D2, and D3 change depending on the measurement stage, the differential amplifiers D1, D2, and D3 have one of the predetermined reference potential levels. Since it operates in the direction of the potential, each differential amplifier D1, D2, D3 can sufficiently realize the operation function with a single power source.

  FIG. 4 is a circuit diagram showing a specific example of the input circuit according to the present invention when the number of cells in each stage is four. In the example of the input circuit 10b (battery voltage measuring circuit) shown in FIG. 4, the cell voltage measuring switches S1 to S9 and the ground switching switches S11 and S12 are provided with a withstand voltage photoMOS capable of withstanding all the cell voltages of the fuel cell. An example of a switch is shown.

  As shown in FIG. 4, cell voltages are acquired for each stage by four cells. At that time, since the common switch (photo MOS switch) S5 is connected to the signal lines of the first stage and the second stage that draw the signal lines in common, the fuel cell is configured as compared with the conventional input circuit. As many photo MOS switches as the number of stages can be reduced. However, in that case, the cell voltage input to the differential amplifiers D1, D2, D3, and D4 is inverted every time the measurement stage is switched. That is, every time the odd-numbered stage and the even-numbered stage are switched, the cell voltages input to the differential amplifiers D1, D2, D3, and D4 are reversed in positive / negative potential.

  Therefore, normally, the power sources of the differential amplifiers D1, D2, D3, and D4 require both power sources in both positive and negative directions to cope with the reversal. However, in the circuit configuration of FIG. 4, the measurement stage is switched. Each time the switch (photo MOS switch) S11, S12 is switched, the signal line at the boundary of the stage is alternately connected to the ground potential (reference potential). That is, every time the measurement stage is switched, the first signal line of each stage is alternately dropped to the ground GND by the switches (photo MOS switches) S11 and S12.

  More specifically, in FIG. 4, a switch (photo MOS switch) S11 is provided on the negative signal line of the first-stage cell C1 and dropped to the ground GND, and the switch is connected to the negative signal line of the second-stage cell C5. (Photo MOS switch) S12 is provided and dropped to the ground GND. By switching ON / OFF of these switches (photo MOS switches) S11 and S12 according to the odd / even number of the measurement stage, that is, when measuring the first stage cell group, the switch (photo MOS switch) When S11 is turned on and the second stage cell group is being measured, the switch (photo MOS switch) S12 is turned on, so that each differential amplifier D1, D2, D3, and D4 has each time the stage is switched. Even if a cell voltage of a different polarity is input, the ground potential (reference potential) is regulated by the reference input terminal of the differential amplifier serving as a reference.

  In this way, by alternately switching the ground GND by the switches (photo MOS switches) S11 and S12, the reference potential (ground potential) of the cell voltage that is alternately input every time the stage is switched moves to − / +. Therefore, the power sources input to the differential amplifiers D1, D2, D3, and D4 are in time with a single power source in a single direction. Therefore, the device power supply of each differential amplifier D1, D2, D3, D4 may be a single power supply instead of a dual power supply.

  As a result, the number of cells that can be scanned at a time can be increased by a factor of two compared to when the ground is not switched. For example, as described above, when the ground switching as shown in FIG. 1 is not performed, if the rated voltage of the differential amplifier is 20 Vmax and the cell voltage is 3 V for one set of two cells, scanning can be performed at one time. The number of cells is 20V ÷ 2 ÷ 3V≈3 cells. In other words, since the differential amplifier requires both power sources, the number of cells that can be scanned at one time is three.

  On the other hand, when the ground is switched as shown in FIG. 3, if the rated voltage of the differential amplifier under the same conditions as described above is 20 Vmax and the cell voltage is 3 V for one set of two cells, the number of cells that can be scanned at one time is 20V ÷ 3V≈6 cells. In other words, when the ground is switched, the number of cells that can be scanned at a time can be doubled compared to when the ground is not switched. As a result, the fuel cell is scanned by scanning multiple channels at a higher speed. Cell voltage can be achieved.

Further, referring to FIG. 4, when the ground is not switched, when the signal line of the switch (photo MOS switch) S5 is disconnected, the first stage cells C1, C2, C3, C4 and the second stage Measurement of eight cells C5, C6, C7, and C8 becomes impossible. However, by alternately switching the ground GND by the switches (photo MOS switches) S11 and S12, only the five cells C4, C5, C6, C7, and C8 in the second stage cannot be measured. Thus, by switching the ground, the number of cells that cannot be measured when the signal line is disconnected can be reduced by half.

As described above, according to the input circuit (battery voltage measurement circuit) according to the present invention, the voltage polarity of adjacent cells is inverted for each cell group for measuring the cell voltage. The number of parts can be reduced, and even if the polarity of the cell voltage is reversed, the cell voltage with the same polarity can be detected by switching the signal line to be grounded. It becomes possible to perform voltage measurement using. As a result, it is possible to use a differential amplifier that operates with a single power supply, so that the material cost of the input circuit can be greatly reduced. In addition, every time the polarity of the cell group to be measured is inverted, the signal lines on both sides of the cell group are alternately switched and connected to the ground, so that scanning can be performed at a time compared to when the signal lines are not switched to the ground. The number of cells can be doubled. As a result, since multiple channels can be scanned at a higher speed, the cell voltage measurement of a cell group in which a large number of cells are connected in series like a fuel cell can be performed at a higher speed.
In the embodiment described above, the case where the cell voltage is measured while scanning each cell of the fuel cell has been described. However, the input circuit according to the present invention is not limited to the cell voltage measurement of the fuel cell, The present invention can also be applied to cell voltage measurement of any secondary battery connected in series, or cell voltage measurement of dry batteries connected in series.

  Since the input circuit of the present invention can detect and measure the electromotive force of an electromotive force element in which a plurality of cells such as fuel cell cells are connected in series with a smaller number of parts than conventional ones, a fuel cell system is used. It can be widely used in fields where voltage monitoring of various batteries is required, mainly in a wide range of industrial fields.

FIG. 2 is a circuit diagram showing a main part of an input circuit sharing a switch provided in a signal line of a cell at a boundary position of each stage, which is a precondition for the present invention. It is explanatory drawing which shows the polarity of the measurement voltage for every cell in the input circuit shown in FIG. It is a circuit diagram which shows the principal part of the input circuit which concerns on this invention. It is a circuit diagram which shows one specific Example of the input circuit which concerns on this invention when the number of cells of each stage is 4 cells. It is a circuit diagram which shows the principal part of the conventional input circuit. It is explanatory drawing which shows the polarity of the measurement voltage for every cell in the input circuit shown in FIG.

Explanation of symbols

10, 10a, 10b Input circuit B1-B5 Buffer C1-C9 Cell D1-D4 Differential amplifier (voltage detection means)
F1 to F3 filter R, r resistance S1 to S10 switch (open / close means)
S11 to S12 switches (switching means)

Claims (4)

A battery voltage measuring circuit that measures the voltage of each cell for each cell group while scanning a group of cells of an assembled battery in which a plurality of cells are connected in series,
A plurality of opening / closing means connected in series to each signal line for outputting the voltage of each cell, and opening and closing for each cell group ;
Switching means for grounding one of the two signal lines on both sides existing at the boundary positions on both sides of the cell group;
A plurality of voltage detecting means for detecting each cell voltage of the cell group in which the opening / closing means is closed ;
Equipped with a,
The switching means alternately grounds the both-side signal lines depending on whether the detection cell group detected by the voltage detection means is odd or even.
The battery voltage measuring circuit , wherein the voltage detecting means detects each cell voltage when any one of the both-side signal lines is grounded . Battery voltage measurement circuit according to claim 1 before Symbol voltage detection means and detects a cell voltage of the same polarity. The switching means and the switching means, the battery voltage measurement circuit according to claim 1 or claim 2, characterized in that a photo-MOS switch having a breakdown voltage higher than the voltage of the battery pack. The battery voltage measuring circuit according to any one of claims 1 to 3 , wherein the assembled battery is a fuel cell.

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