JP2013055836A - Voltage-balance correction device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately detect a voltage difference between a plurality of secondary batteries connected in series and accurately correct a voltage balance of the batteries without being affected, in particular, by noise, in a balance correction device that corrects the voltage balance of the batteries connected in series.SOLUTION: A voltage-balance correction circuit includes: first and second batteries that are connected in series; first to fourth resistive elements that are connected in parallel to the series circuit of the first and second batteries; control means that is disposed between the connection portion of the first and second batteries and the connection portion of the second and third resistive elements, detects the potential difference between both the connection portions, and performs balance correction of output voltages of the first and second batteries according to the potential difference; and a capacitive element that is disposed between the connection portion of the first and second resistive elements and the connection portion of the third and fourth resistive elements.

Description

  The present invention relates to a voltage balance correction device that corrects the voltage balance of a plurality of secondary batteries connected in series.

  Nowadays, secondary batteries such as lithium ion batteries and nickel metal hydride storage batteries are widely used not only for so-called hybrid cars and electric vehicles, but also as backup power sources for forklifts and various industrial machines. Therefore, a large output is required for a secondary battery used for such an application, and a large number of batteries are connected in series. In this case, it is particularly important that the output voltages of the batteries connected in series match, and therefore a voltage balance correction circuit is incorporated.

  FIG. 5 is a diagram showing a part of a circuit used in a voltage balance correction apparatus for two secondary batteries connected in series. The voltage dividing resistors R1 and R2 are connected in parallel to the batteries B1 and B2 connected in series, and the connection m of the negative terminal of the battery B1 and the positive terminal of the battery B2 and the connection n of the voltage dividing resistors R1 and R2 are connected. A voltage difference detection circuit (not shown) for detecting a voltage difference is disposed between them. Based on the detection result of the detection circuit, charging from the battery B1 to the battery B2 or charging from the battery B2 to the battery B1 is performed.

  Patent Document 1 discloses a voltage balance correction circuit that performs voltage balance correction by charging from the battery B1 to the battery B2 or charging from the battery B2 to the battery B1 based on the detection result of the voltage difference. FIG. 6 shows an example of the circuit disclosed in Patent Document 1. The comparator 21 compares the potential Vm of the connection portion m with the potential Vn of the connection portion n, supplies a voltage Vx as a result of the comparison to the variable pulse generation circuit 12, and supplies control signals φ1 and φ2 according to the voltage Vx. It outputs to corresponding switching element S1, S2. By this processing, electromagnetic energy is accumulated in the inductor L, charging is performed from the battery B1 to the battery B2, or from the battery B2 to the battery B1, and the output voltages of the batteries B1 and B2 are made to coincide.

JP 2008-17605 A

  In the conventional voltage balance correction circuit, voltage dividing resistors R1 and R2 having high resistance (for example, several MΩ) are used in order to reduce power consumption. For this reason, it is easily affected by noise. For example, in the case of a voltage balance correction device mounted on an electric vehicle, an inverter circuit is used to drive a motor nearby, and the potential of Vn fluctuates due to noise including harmonics generated when driving the circuit. An accurate potential difference cannot be detected. In addition to the inverter circuit, it is also affected by noise from other circuits and electronic devices arranged around the device, and the potential difference cannot be accurately detected.

  Therefore, the present invention provides a voltage balance correction device capable of accurately detecting a voltage difference between two batteries connected in series without being affected by noise and accurately correcting the voltage balance of the batteries. The purpose is to do.

  According to the present invention, the above-described problem is achieved by the first and second batteries connected in series, the first to fourth resistance elements connected in parallel to the series circuit of the first and second batteries, It is arranged between the connection part of the first and second batteries and the connection part of the second and third resistance elements, detects the potential difference between the two connection parts, and detects the first and second according to the potential difference. A voltage having control means for correcting the balance of the output voltage of the battery, and a capacitive element disposed between the connection portion of the first and second resistance elements and the connection portion of the third and fourth resistance elements This can be achieved by providing a balance correction device. That is, a noise filter is formed by the first to fourth resistor elements and the capacitor element, and the influence of noise from various electronic devices such as inverter circuits arranged around the first and second batteries is eliminated. The voltage fluctuation at the connection portion of the second and third resistance elements, which becomes the reference voltage, is reduced.

  According to the present invention, the first and third resistance elements are arranged along the first battery, and the second and fourth resistance elements are the second battery. It is the structure arrange | positioned along. With this configuration, the heat generated by the internal resistance of the first and second batteries is evenly applied between the first and second resistance elements and the third and fourth resistance elements, and the temperature increases. The variation of the changing resistance value is equalized, and the voltage dividing accuracy between the first and second resistance elements and the third and fourth resistance elements is improved.

  Further, the control means outputs a control signal based on the detected potential difference between the two connection portions, and corrects the voltage balance between the first and second batteries according to the control signal.

  According to the present invention, when detecting the output voltage difference between the first and second batteries, the influence of noise can be eliminated and the voltage difference can be detected based on an accurate reference voltage. The voltage balance correction of the second battery can be performed. In addition, the effect of heat generation due to the internal resistance of the first and second batteries is equally applied to the first and second resistance elements and the third and fourth resistance elements to improve the voltage dividing accuracy between the resistance elements. Thus, more accurate voltage balance correction can be performed.

It is a figure which shows the voltage difference detection circuit used for the voltage balance correction apparatus of this embodiment. It is a circuit diagram which shows the structure which has arrange | positioned the capacitor | condenser to the voltage dividing resistor. It is the schematic diagram which arrange | positioned the voltage dividing resistor and the capacitor | condenser in the battery. It is a figure which shows the characteristic of the noise filter formed with a voltage dividing resistor and a capacitor | condenser. It is a figure which shows the structure of a part of detection circuit of the voltage difference used for a voltage balance correction apparatus. It is a figure which shows an example of the voltage balance correction circuit disclosed by patent document.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a circuit diagram of a potential difference detection circuit used in the voltage balance correction apparatus of this embodiment. Batteries E1 and E2 represent any two of a number of batteries connected in series, and a negative terminal of a battery (not shown) having the same configuration is connected to the positive terminal of the battery E1, and the negative electrode of the battery E2 The positive terminal of a battery (not shown) having the same configuration is also connected to the terminal. In the present embodiment, for example, lithium ion batteries are used as the batteries E1 and E2.

  In the voltage balance correction apparatus of the present embodiment, the resistor R11 (first resistor element), the resistor R12 (second resistor element), and the resistor R21 (third resistor) are connected in parallel to the series circuit of the battery E1 and the battery E2. Element) and a series circuit of a resistor R22 (fourth resistor element) are connected, and the resistors R11, R12, R21, and R22 divide the voltage between the series circuit of the battery E1 and the battery E2. Further, a capacitor (capacitance element) C is connected between the connection portion of the resistors R11 and R12 and the connection portion of the resistors R21 and R22. Note that the resistance values of the resistors R1, R12, R21, and R22 used in the present embodiment are, for example, high resistances of several MΩ in order to reduce power consumption.

  Further, the potential difference between the potential Va of the connection portion a and the potential Vb of the connection portion b is compared between the connection portion a of the negative electrode terminal of the battery E1 and the positive electrode terminal of the battery E2 and the connection portion b of the resistors R12 and R21. A control circuit 2 that outputs a control signal based on this potential difference is connected. The control circuit 2 outputs a control signal based on the potential difference between the two connection portions a and b, drives a switching element (not shown) according to the control signal, accumulates electromagnetic energy in the inductor, and from the battery E1 to the battery The battery E1 is charged from E2 or the battery E2.

  FIG. 2 is a diagram showing the connection relationship between the series circuit of the resistors R11, R12, R21, and R22 shown in FIG. As described above, the capacitor C is disposed between the connection portion of the resistors R11 and R12 and the connection portion of the resistors R21 and R22, and has a function of a noise filter. In FIG. 2, b is the connection portion b in FIG. 1, and is compared with the voltage Va of the connection portion a by using the voltage Vb generated at the connection portion b as a reference voltage.

  FIG. 3 is a schematic external view in which the circuit of the present embodiment having the above-described configuration is disposed in actual batteries E1 and E2. As described above, the batteries E1 and E2 are any two of the many batteries connected in series, and as shown in the figure, a large number of batteries E are arranged before and after the batteries E1 and E2. It is installed.

  The circuit board 1 is disposed across the batteries E1 and E2, and the circuit board 1 is attached to the batteries E1 and E2 by screws or the like (not shown). The circuit board 1 is provided with the resistors R11, R12, R21, and R22, and the capacitor C. The resistors R11 and R21 are provided on the circuit board 1 in contact with the battery E1, and the resistors R12 and R22 are provided with the battery E2. It is disposed on the circuit board 1 in contact therewith. Accordingly, the resistors R11 (first resistor element) and R21 (third resistor element) are disposed at positions on the circuit board 1 that are affected by the heat generated when the battery E1 is driven, and the resistor R12 (second resistor element). ) And R22 (fourth resistance element) are disposed at positions on the circuit board 1 that are affected by the heat generated when the battery E2 is driven.

  The resistors R11, R12, R21, R22, and the capacitor C are connected to each other as shown in FIGS. Although not shown in FIG. 3, a circuit board having the same configuration is disposed between the battery E1 and the battery E disposed next to the battery E1, and is disposed next to the battery E2 and the battery E2. A circuit board having the same configuration is also disposed between the installed battery E and the battery E.

The circuit of this embodiment has the configuration shown in FIGS. 1 and 2 and has the following differences when compared with the circuit shown in FIG. 5 shown in the conventional example. First, in the conventional circuit shown in FIG. 5, a series circuit of resistors R1 and R2 is used, and the characteristic impedance of the voltage dividing resistor is only the resistance component, and Z = R
R = R1 + R2
It is.
On the other hand, the circuit of this embodiment is a circuit including a capacitor C as shown in FIGS. 1 and 2, and the characteristic impedance is Z = Ra + Rb / (1 + jωCRb).
Ra = R11 + R22
Rb = R12 + R21
It is.

  Therefore, in the present embodiment, as described above, the capacitor C is disposed between the connection portion of the resistors R11 and R12 and the connection portion of the resistors R21 and R22 to form a noise filter, and various electronic devices around the device. It is possible to eliminate the influence of noise generated.

  FIG. 4 is a diagram showing filter characteristics of the circuit shown in FIG. This characteristic F is a characteristic of a low-pass filter that cuts off a frequency above a predetermined frequency based on the CR time constant. Here, the cut-off frequency in this example is set according to the use of the battery in which the voltage balance correction device is used. For example, when used in an electric vehicle, noise removal from an inverter circuit or the like generated to drive the motor is removed. Frequency.

  FIG. 4 shows an example of noise caused by the motor as noise, and A shown in FIG. 4 indicates the frequency of noise corresponding to the rotational speed of the motor during idling. Actually, a frequency group of noises A1 and A2 based on harmonics is included on the left and right with the frequency A as the center. For example, when the number of rotations of the motor at idling is 2,000 rpm, the corresponding noise frequency A is 30 Hz, and the noise includes left and right harmonics centering on this frequency A (30 Hz).

  In the case of an automobile, the rotational speed of the motor is the lowest during idling, and the rotational speed of the motor increases as the speed increases. Therefore, in the case of noise caused by the motor, the noise frequency A corresponding to the number of revolutions during idling is used as a reference for setting the cutoff frequency. The description of “noise due to the motor” surrounded by the halftone dots shown in the figure indicates a range of frequencies higher than the frequency A, and the frequency of noise due to the motor (the center of the frequency) is the frequency A. It is in the above range.

  Therefore, the filter characteristics shown in FIG. 4 are determined by setting circuit constants, and noise removal of the voltage balance correction apparatus is performed. That is, the resistance values Ra (R11 + R22) and Rb (R12 + R21) and the capacitance of the capacitor C are set so that the cut-off frequency is lower than the frequency A, and noise caused by the motor is removed.

  In the description of FIG. 4, the case of noise caused by the motor has been described. However, when removing noise from other electronic devices, the cutoff frequency is set corresponding to the frequency of the noise in the same manner. A similar implementation can be made by determining the circuit constants for Ra, Rb, and C.

  Therefore, by including the potential difference detection circuit shown in FIG. 1 in the voltage balance correction apparatus of this example, the output voltage difference between two batteries connected in series can be accurately detected without being affected by noise, The battery voltage balance can be accurately corrected.

  In the case of the present embodiment, the resistors R11 (first resistor element) and R21 (third resistor element) are disposed at positions on the circuit board 1 that are affected by heat generated when the battery E1 is driven. The resistors R12 (second resistor element) and R22 (fourth resistor element) are disposed at positions on the circuit board 1 that are affected by heat generated when the battery E2 is driven. Therefore, the influence of heat generated by the internal resistances of the batteries E1 and E2 is equalized, and the variation in resistance value that varies with temperature can be equalized to improve the voltage dividing accuracy between the resistive elements.

  In the above description of the embodiment, the voltage balance correction device for the batteries E1 and E2 connected in series has been described. The voltage balance correction of the other two consecutive batteries can be similarly performed.

  Furthermore, in the description of the above embodiment, the example of the lithium ion battery has been described as the batteries E1 and E2, but a nickel hydride storage battery, a nickel cadmium storage battery, or the like may be used.

1. Circuit board 2. Control circuit E1, E2. Battery R11, R12, R21, R22. Resistance C. Capacitor F. Filter characteristics A. Frequency

Claims (3)

First and second batteries connected in series;
First to fourth resistance elements connected in parallel to a series circuit of the first and second batteries;
It is arranged between the connection part of the first and second batteries and the connection part of the second and third resistance elements, detects a potential difference between the connection parts, and the first and second according to the potential difference. Control means for correcting the balance of the output voltage of the battery;
A voltage balance correction apparatus comprising: a connection portion between the first and second resistance elements; and a capacitance element disposed between the connection portions between the third and fourth resistance elements.   The first and third resistance elements are disposed along the first battery, and the second and fourth resistance elements are disposed along the second battery. The voltage balance correction apparatus according to claim 1.   The control means outputs a control signal based on the detected potential difference between the two connection portions, and corrects the voltage balance between the first and second batteries according to the control signal. Or the voltage balance correction apparatus according to 2.