JP4566964B2 - Total battery voltage detector - Google Patents

Description

  The present invention relates to a total battery voltage detection device, and more particularly to a total battery voltage detection device that detects a total voltage of an assembled battery in which a plurality of single cells are connected in series.

  For example, as a power source for an electric vehicle (PEV) or a hybrid electric vehicle (HEV), an assembled battery or a battery group in which a plurality of single cells such as lithium ion batteries are connected in series is used. Conventionally, in these batteries for electric vehicles and hybrid vehicles, when detecting the voltage of the total battery, a total voltage detection circuit in which the input side and the output side are insulated has been used (for example, Patent Documents 1 and 2). reference). The reason why insulation is required is that if a high voltage is short-circuited to the chassis ground of the vehicle, there is a risk of occupants being struck by electric shock. Insulated. As a configuration example, the total voltage of the assembled battery is divided, the voltage is measured by an AD converter, the signal is transmitted by being insulated by a photocoupler, the total voltage of the assembled battery is converted into a current through a resistor, and the Hall element is A circuit that measures current as a voltage by performing current-current conversion while insulating it is known.

  FIG. 2 specifically shows an example of such a total battery voltage detection circuit. The total voltage of the assembled battery 1 is divided to a low voltage by the resistors 2 and 3 and becomes an input voltage of the AD converter 4. The AD converter 4 using the reference voltage source 5 as a reference voltage is operated by an insulated power source 6. The AD converter 4 is insulated through a photocoupler unit 7 and is operated by a microcomputer 8 that is operated by a power source insulated from a high voltage system, and performs operation control, data communication with a host control circuit, and the like.

JP 2006-003156 A Japanese Patent Laid-Open No. 2005-198251

  However, the conventional total battery voltage detection circuit has the problem that an insulated power supply is required and the cost is high. In addition, for accurate total voltage measurement, the accuracy of the reference voltage of the AD converter must be increased, and the cost of the reference voltage source is also increased. Furthermore, since a voltage dividing resistor is used, if current consumption when not in use becomes a problem, a switching element for interrupting current is also necessary.

  An object of the present invention is to provide a total battery voltage detection circuit that detects the total voltage of an assembled battery without using an AD converter or an insulated power source, which is expensive.

In order to solve the above-described problems, the present invention provides a total battery voltage detecting device for detecting a total voltage of an assembled battery in which a plurality of single cells are connected in series, and one end of the uppermost unit constituting the assembled battery. A first switching element connected to the positive terminal of the battery, a first voltage-dividing resistor having one end connected to the other end of the first switching element and dividing the total voltage of the assembled battery; A second voltage divider that is connected to the other end of the first voltage dividing resistor, the other end is connected to a negative terminal of the lowest cell constituting the assembled battery, and divides the total voltage of the assembled battery. A resistor, a first capacitor having one end connected to the connection point of the first and second voltage dividing resistors, and a second capacitor having one end connected to the negative terminal of the lowest cell constituting the assembled battery. And a positive phase input terminal connected to the other end of the first capacitor, Comprising a differential amplifier circuit which forces terminal connected to the other end of said second capacitor, and measuring the output voltage of the differential amplifier circuit while turning on and off the first switching element a rectangular wave To detect the total voltage of the assembled battery.

  In the present invention, the total voltage of the assembled battery is divided while the switching element is controlled to be turned on and off by a rectangular wave, and is input to the input terminal of a differential amplifier circuit that is insulated from the assembled battery by capacitor coupling. When the switching element is controlled by a rectangular wave, a rectangular wave with an amplitude proportional to the voltage of the assembled battery is output through the capacitor. Therefore, connect the capacitor output to the input terminal of the differential amplifier circuit and measure the amplitude of the rectangular wave. Thus, the total voltage of the assembled battery can be detected. For this reason, the total voltage detection device of the present invention can detect the total voltage of the assembled battery without using an AD converter or an insulated power source, which is expensive, and the number of photocouplers can be reduced compared to the conventional one. it can.

In the present invention, the voltage dividing resistors is increased in order to reduce the current consumption of the total battery voltage detecting circuit, it takes time to charge and discharge the capacitor, but the voltage dividing resistors can not be increased, the first and second frequency further comprising a buffer circuit for receiving the divided voltage of the resistors, the buffer circuit, an inverting input terminal connected to an output terminal, the connection point of the positive-phase input terminal first and second voltage dividing resistors By connecting one end of the first capacitor to the output terminal of the buffer circuit, and reducing the output impedance using the OP amplifier , the value of the voltage dividing resistor can be increased. Current consumption can be suppressed.

In addition, one end is connected to the + terminal of the uppermost unit cell constituting the assembled battery, one end is connected to the other end of the second switching element, and the other end constitutes the assembled battery. A load resistor connected to the + terminal of the higher cell than the lowest cell, and a third connected to the + terminal of the upper cell and the other end connected to the power supply + terminal of the buffer circuit A switching element, and the power supply-terminal of the buffer circuit is connected to the -terminal of the lowest cell constituting the assembled battery , and the second and third switching elements are turned on when the buffer circuit is in operation. is controlled to the load resistance is not supplying hydraulic power to the buffer circuit of the battery pack, urchin by you energizing current consumption and substantially the same current of the buffer circuit further unit cell higher than the unit cell of the upper The total battery voltage detection The operating power can be supplied from the assembled battery only when the circuit is operating, the current consumption of the assembled battery cells can be made the same, and the voltage variation among the individual cells constituting the assembled battery can be reduced. .

According to the present invention, the total voltage of the assembled battery is divided while the first switching element is controlled to be turned on and off by a rectangular wave, and is input to the input terminal of the differential amplifier circuit that is insulated from the assembled battery by capacitor coupling. Since the total voltage of the assembled battery is detected by measuring the output voltage of the dynamic amplifier circuit, an effect is obtained that the total voltage of the assembled battery can be detected without using an AD converter or an insulated power source, which is expensive be able to.

  Embodiments of a total battery voltage detection circuit according to the present invention will be described below with reference to the drawings.

(Constitution)
As shown in FIG. 1, the total battery voltage detection circuit 20 of the present embodiment includes a battery pack 1 in which a voltage dividing resistor 2 and a voltage dividing resistor 3 are connected via the output side of one photocoupler A in the photocoupler unit 7. It is connected to the. That is, the photocoupler A as a switching element and the voltage dividing resistors 2 and 3 are connected between the + terminal of the uppermost unit cell constituting the assembled battery 1 and the − terminal of the lowermost unit cell. In the assembled battery 1, a plurality of lithium ion batteries as unit cells are connected in series.

  One end of the voltage dividing resistor 3 is connected to the + input terminal (positive phase input terminal) of the OP amplifier 10 as a buffer circuit in which the − input terminal (reverse phase input terminal) is connected to the output terminal. The other end of 3 is connected to the minus terminal of the lowest unit cell constituting the assembled battery 1. Therefore, the low voltage side of the assembled battery 1 divided by the voltage dividing resistors 2 and 3 is input to the OP amplifier 10. The OP amplifier 10 is supplied with operating power from some terminals of the assembled battery 1 via the output side of one photocoupler C of the photocoupler unit 7.

  The output terminal of the OP amplifier 10 and the negative terminal of the lowest cell constituting the assembled battery 1 are connected to the positive input terminal and negative input of the differential amplifier 13 as a differential amplifier circuit through the capacitor 11 and the capacitor 12. Connected to each terminal. The output of the differential amplifier 13 is connected to an input terminal (abbreviated as AD input in FIG. 1) of an AD converter of a microcomputer (hereinafter referred to as a microcomputer) 8. A reference voltage source 5 for AD conversion is connected to the microcomputer 8, and an output port is connected to the photocoupler unit 7. FIG. 1 shows an example in which the differential amplifying unit 13 includes an OP amplifier and a resistor.

  The microcomputer 8 is galvanically isolated from the assembled battery 1 via the capacitor 11, the capacitor 12, and the photocoupler unit 7. The resistor 9 is connected to the terminal of the assembled battery 1 for operating power of the OP amplifier 10, and is connected to the + terminal of the assembled battery 1 via the output side of one photocoupler C of the photocoupler unit 7. Yes. That is, when the OP amplifier 10 is operated, the total battery voltage detection circuit 20 supplies a current substantially the same as the current consumed by the OP amplifier 10 to the single battery of the assembled battery 1 that does not supply operating power to the OP amplifier 10. It has a resistor 9 as a load and a photocoupler C as a switching element.

(Operation)
Next, the operation of the total battery voltage detection circuit 20 of this embodiment will be described.

  First, when the operation is stopped, since the operation power of the microcomputer 8 and the photocoupler unit 7 is not supplied, all the photocouplers of the photocoupler unit 7 are in the OFF state. Therefore, no current flows through the voltage dividing resistor portion constituted by the resistors 2 and 3. In addition, since no current is passed through the resistor 9 and the OP amplifier 10, no current consumption flows when the operation is stopped.

  Next, after starting the operation, the microcomputer 8 turns on the photocoupler B and the photocoupler C of the photocoupler unit 7. By this operation, a current is supplied from a part of the assembled battery 1 serving as an operation power source to the buffer circuit constituted by the OP amplifier 10, and a current is supplied from the remaining single cells of the assembled battery 1 through the resistor 9. By selecting a value so that the current flowing through the resistor 9 is the same as the operating current of the buffer circuit, the current supplied from each single cell constituting the assembled battery 1 is made uniform during operation, and consumption during operation It is possible to prevent a voltage difference (variation) between the single cells due to the current.

  Next, regarding the operation at the time of voltage measurement, the microcomputer 8 controls the photocoupler A of the photocoupler unit 7 on and off at high speed. Then, a rectangular wave waveform having an amplitude of the assembled battery 1 is generated in the voltage dividing resistor portion formed by the resistor 2 and the resistor 3, and the waveform is generated by the buffer circuit including the OP amplifier 10 by the capacitor 11, 12 is output to the input terminal of the differential amplifier 13 and a rectangular waveform is applied to the AD input terminal of the microcomputer 8. Since this rectangular wave waveform is generated by the microcomputer 8, if AD conversion is performed in accordance with the on / off control timing of the photocoupler A by the microcomputer 8, the amplitude of the rectangular wave, that is, the total voltage of the assembled battery 1 is measured (detected). can do.

(Effects etc.)
Next, effects and the like of the total battery voltage detection circuit 20 of the present embodiment will be described.

  In the total battery voltage detection circuit 20 of the present embodiment, the total voltage of the single cells constituting the assembled battery 1 is dc-insulated as a rectangular wave amplitude using capacitor coupling, and is measured by the AD converter of the microcomputer. A dedicated AD converter and insulated power supply are no longer required. For this reason, the cost of the total battery voltage detection circuit can be reduced.

  Further, the total battery voltage detection circuit 20 of the present embodiment includes an OP amplifier 10 that receives the divided voltage of the voltage dividing resistor unit, and an output terminal of the OP amplifier 10 and an input terminal of the differential amplifier unit 13. Since the output impedance is reduced by coupling the capacitors 11 and 12 between them, the values of the resistors 2 and 3 can be increased, and current consumption can be suppressed.

  Further, in the total battery voltage detection circuit 20 of the present embodiment, the operating power of the OP amplifier 10 is supplied from some single cells constituting the assembled battery 1, and the OP amplifier 10 of the assembled battery is operated when the OP amplifier 10 is operated. Since the unit cell that is not supplied with the operating power supply has the resistor 9 and the photocoupler C for supplying substantially the same current as the consumption current of the OP amplifier 10, the assembled battery is operated only when the total battery voltage detection circuit 20 is in operation. 1 can supply operation power and the consumption current of the cells of the assembled battery 1 can be made the same. Therefore, the voltage variation of each of the cells constituting the assembled battery 1 can be reduced.

  Further, in the total battery voltage detection circuit 20 of the present embodiment, since the reference power source of the AD converter can be shared with the AD reference power source of the microcomputer, there is no need for a dedicated reference voltage source as the total voltage measuring circuit, and for the AD conversion of the microcomputer Since it can be shared with the reference power supply, the number of parts and the cost can be greatly reduced as compared with the conventional total battery voltage detection circuit.

  In this embodiment, a high voltage power source is connected instead of the assembled battery 1, and the result of measuring the waveform of the AD input terminal while superimposing a sine wave on the voltage of the high voltage power source is shown in FIG. As shown in FIG. 3, a sine wave is superimposed on the AD input terminal, and it can be seen that the input voltage of the assembled battery is accurately transmitted. In actual measurement, since it takes time until the amplitude of the AD input waveform is stabilized, AD conversion is performed when the amplitude is stabilized, and the on / off control is performed immediately thereafter, whereby the amplitude can be measured accurately. FIG. 4 shows the relationship between the total voltage of the assembled battery and the amplitude obtained by AD conversion when the voltage of the assembled battery is actually changed. As shown in FIG. 4, since the relationship between the assembled battery voltage and the amplitude obtained by AD conversion is a straight line, the total battery voltage detection circuit 20 to which the present invention is applied accurately measures (detects) the total voltage of the assembled battery. I understand that it is possible.

  In the present embodiment, an example in which the assembled battery 1 is configured by a plurality of lithium ion batteries has been described. However, the present invention is not limited thereto, and may be configured by, for example, a nickel metal hydride battery. Further, in the present embodiment, the assembled battery is illustrated, but the present invention is not limited to this, and it is needless to say that the present invention can be applied to a battery group in which unit cells are connected in series. Furthermore, in the present embodiment, a photocoupler has been exemplified as the switching element. However, other known elements such as FETs or other elements developed in the future may be used.

  As described above, the present invention provides a total battery voltage detection circuit that detects the total voltage of an assembled battery without using an AD converter or an insulated power source, which increases the cost. Since it contributes to sales, it has industrial applicability.

It is a circuit diagram of the total battery voltage detection apparatus of embodiment which can apply this invention. It is a circuit diagram of the conventional total battery voltage detection apparatus. It is a characteristic diagram which shows the waveform of the input terminal of AD converter at the time of using high power supply voltage instead of an assembled battery in the total battery voltage detection apparatus of embodiment. It is a characteristic diagram which shows the correlation of an assembled battery voltage and a measurement voltage with the total voltage detection apparatus of embodiment.

Explanation of symbols

1 assembled battery 2 resistance (first voltage dividing resistance)
3 resistor (second resistor divider)
7 Photocoupler
7A Photocoupler (first switching element)
7B Photocoupler (second switching element)
7C Photocoupler (third switching element)
8 Microcomputer 9 Resistance (Load resistance )
10 OP amplifier (buffer circuit)
11 Capacitor (first capacitor)
12 Capacitor (second capacitor)
13 Differential amplifier (differential amplifier circuit)
20 Total battery voltage detector

Claims (3)

In the total battery voltage detecting device for detecting the total voltage of the assembled battery in which a plurality of single cells are connected in series,
A first switching element having one end connected to the + terminal of the uppermost unit cell constituting the assembled battery;
A first voltage dividing resistor having one end connected to the other end of the first switching element and dividing the total voltage of the assembled battery;
One end is connected to the other end of the first voltage dividing resistor, the other end is connected to the negative terminal of the lowest cell constituting the assembled battery, and a second voltage is divided to the total voltage of the assembled battery. And the partial pressure resistance of
A first capacitor having one end connected to a connection point of the first and second voltage dividing resistors;
A second capacitor having one end connected to the negative terminal of the lowest unit cell constituting the assembled battery;
A differential amplifier circuit having a positive phase input terminal connected to the other end of the first capacitor and a negative phase input terminal connected to the other end of the second capacitor ;
With
A total battery voltage detecting device for detecting a total voltage of the assembled battery by measuring an output voltage of the differential amplifier circuit while controlling on / off of the first switching element with a rectangular wave.   The buffer circuit further includes a buffer circuit that receives the divided voltage of the first and second voltage dividing resistors. The buffer circuit has a negative-phase input terminal connected to the output terminal, and a positive-phase input terminal connected to the first and second phase terminals. 2. The total battery voltage detection according to claim 1, wherein an OP amplifier is connected to a connection point of two voltage dividing resistors, and one end of the first capacitor is connected to an output terminal of the buffer circuit. apparatus.   A second switching element having one end connected to the positive terminal of the uppermost unit cell constituting the assembled battery, one end connected to the other end of the second switching element, and the other end constituting the assembled battery A load resistor connected to the + terminal of the upper cell, and one end connected to the + terminal of the upper cell, and the other end connected to the power supply + terminal of the buffer circuit. A third switching element, and the power supply-terminal of the buffer circuit is connected to the -terminal of the lowest cell constituting the assembled battery, and when the buffer circuit is activated, the second and second switching elements are connected. The switching element 3 is controlled to be in an on state, and the load resistor does not supply operating power to the buffer circuit in the assembled battery, and the consumption of the buffer circuit is higher than the upper unit cell. Current The total battery voltage detection device according to claim 2, characterized in that energizing the substantially same current.

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