JP2009072038A - Battery voltage detection apparatus and control method thereof - Google Patents

Abstract

In a voltage measuring device for an assembled battery in which a plurality of secondary batteries are connected in series, a voltage converter and a bypass circuit are required independently, so that the number of parts increases, and the voltage converter is added to a battery cell. Since the battery is connected, the battery cell is discharged due to the input impedance, and the cell voltage varies due to variations in the input impedance.
By passing a bypass current according to the input impedance of the voltage converter and changing the connection time of the voltage converter, it is not necessary to simplify the cell voltage equalization circuit, increase the impedance of the voltage converter, and suppress variations. Thus, the above problem can be solved.
[Selection] Figure 1

Description

  The present invention relates to a cell voltage detection device for an assembled battery in which a plurality of secondary batteries are combined, and a control method therefor.

  Secondary batteries used in power supply devices, especially devices with a power failure compensation function that can supply power to a main load for a fixed time during a power failure, usually require a high voltage, so a large number of battery cells are connected in series. ,used. Further, due to variations in the self-discharge amount and charge acceptance rate of the secondary battery, variations occur in the discharge capacity and cell voltage of each battery cell. In order to solve this problem, a method for providing a voltage detection unit and a bypass circuit for each battery cell and making the bypass circuit conductive when the voltage difference between the cell voltages exceeds a predetermined value is known (for example, Patent Document 1). FIG. 3 shows a conventional charging device described in Patent Document 1. In FIG.

In FIG. 3, the value of the cell voltage detected by the voltage converters 21 to 23 connected in parallel to the battery cells 101 to 103 is input to the cell voltage comparison / bypass time arithmetic circuit 4 to compare each cell voltage. Thus, the ON time of the bypass switches 51 to 53 connected in series to the bypass resistors 61 to 63 is changed, and the cell voltages of the battery cells 101 to 103 can be equalized.
JP-A-8-19188

  However, in the conventional configuration, since the voltage converter and the bypass circuit are required independently, the number of parts is increased, and the voltage converter remains connected to the battery cell. There is a problem that discharge occurs, and further, the cell impedance varies due to variations in input impedance.

  In order to solve the problem of Patent Document 1, the present invention simplifies the cell voltage equalization circuit and converts the voltage by flowing a bypass current according to the input impedance of the voltage converter and changing the connection time of the voltage converter. It is an object of the present invention to provide an assembled battery voltage detection device that does not require high impedance and suppression of variation in the instrument impedance.

  In order to solve the above-mentioned conventional problems, in the present invention, in a voltage detection device for a battery pack in which a plurality of battery cells are connected in series, a voltage converter is connected in parallel to each battery cell of the battery pack via a connection switch. A cell voltage comparison / connection time calculation circuit is provided for connecting and controlling the connection time of the connection switch by the output of the voltage converter. Furthermore, when the cell voltage of the assembled battery is detected, the voltage measurement time of all the battery cells is initialized, the cell voltage of each battery cell is measured at the set measurement time, and the measured cell voltage of each battery cell is compared. When the next measurement time of the battery cell with the minimum cell voltage is set to Tmin, it is determined whether or not the difference between the cell voltage of the other battery cell and the cell voltage of the minimum battery cell of the cell voltage is less than the threshold value. Is configured such that the next measurement time of the battery cell is set to Tmin, and if it is not less than the threshold, the next measurement time of the battery cell is increased by ΔT.

According to the present invention, the cell voltage variation can be equalized simultaneously with the cell voltage measurement, and in addition, highly accurate parts and adjustments for increasing the impedance of the voltage converter and suppressing the variation are not required. Therefore, it is possible to realize a voltage detection device having a low-cost cell voltage equalizing function with a reduced number of parts.

  According to the assembled battery voltage detection device of the present invention, the cell voltage detection voltage converter can also serve as a bypass circuit for equalizing the cell voltage, so that independent circuits are not required, and the circuit can be simplified. It becomes. In addition, since the voltage converter is connected to the battery cell via the connection switch, it is possible to increase the impedance of the voltage converter to suppress the self-discharge of the battery by reducing the on-time of the connection switch. Become. Furthermore, the variation in the input impedance of the voltage converter is canceled as a result of the cell voltage equalization by changing the connection switch on time. Therefore, according to the present invention, it is not necessary to reduce the number of dedicated bypass circuits, to increase the input impedance of the voltage converter, and to eliminate the need for highly accurate parts and adjustments for suppressing variations, so that low-cost cell voltage equalization is possible. A voltage detecting device having a function can be realized.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

(Embodiment 1)
FIG. 1 is an example of a block diagram of an assembled battery voltage detection apparatus according to Embodiment 1 of the present invention. In FIG. 1, the same components as those in FIG.

  Voltage converters 21 to 23 are connected in parallel to secondary batteries 101 to 103 connected in series in FIG. 1 via connection switches 11 to 14. The cell voltage measurement values detected by the voltage converters 21 to 23 are input to the cell voltage comparison / connection time calculation circuit 3, and the cell voltage comparison / connection time calculation circuit 3 switches the connection switches 11 to 14 based on the calculation result. It is configured to control.

  The assembled battery voltage detection device having such a configuration will be described below.

  When the connection switches 11 to 14 are turned on, the voltage converters 21 to 23 respectively corresponding to the secondary batteries 101 to 103 are connected. The input impedance of the voltage converters 21 to 23 is low enough to eliminate the cause of cell voltage variation such as the self-discharge amount of the secondary batteries 101 to 103, and while the voltage converters 21 to 23 are connected, A bypass current flows through each cell of the secondary batteries 101 to 103 due to the impedance. Each cell voltage detected by the voltage converters 21 to 23 is input to the cell voltage comparison / connection time calculation circuit 3. The cell voltage comparison / connection time calculation circuit 3 compares the cell voltages, sets the connection switch ON time corresponding to the battery cell having a large value to be long, and turns ON the connection switch corresponding to the battery cell having a small cell voltage value. By setting the time short, cell voltage detection and cell voltage variation can be performed simultaneously.

  Thus, according to the present invention, the voltage converter for cell voltage detection can also serve as a bypass circuit for equalizing the cell voltage, so that independent circuits are not required, and the circuit can be simplified. In addition, since the voltage converter is connected to the battery cell via the connection switch, it is possible to increase the impedance of the voltage converter to suppress the self-discharge of the battery by reducing the on-time of the connection switch. Become. Furthermore, the variation in the input impedance of the voltage converter is canceled as a result of the cell voltage equalization by changing the connection switch on time.

(Embodiment 2)
FIG. 2 is an example of a control flowchart of the assembled battery voltage detection device according to Embodiment 2 of the present invention.

  Generally, a finite time is required to complete an accurate measurement based on the conversion time of the voltage converters 21 to 23 and the input circuit time constant of the cell voltage comparison / connection time calculation circuit 3. Therefore, the minimum connection switch on time at which accurate measurement of the cell voltage can be completed is Tmin, and at the start of measurement, the all connection switch on time is set to Tmin, and the cell voltage measurement is performed. Next, the measured cell voltages are compared, the battery cell having the smallest cell voltage is set as Smin, and the next connection switch on time of Smin is set to Tmin. Next, the cell voltage of another battery cell is compared with the cell voltage of Smin, and if the difference is less than (or less than) the threshold, the connection switch on time of the corresponding battery cell is set to Tmin, and the difference is greater than the threshold ( In the case of (or above), the connection switch ON time of the corresponding battery cell is increased by ΔT and set. When the connection switch-on times of all the battery cells are thus set, the cell voltages of all the cells are measured with the respective connection switch-on times. By repeating these operations, the connection switch on time is changed.

  According to such a configuration, as long as the cell voltage measurement interval time allows, the connection switch on time can be changed until the difference in cell voltages of all the battery cells is equal to or less than a threshold value (or less). When the voltage difference is equal to or less than the threshold value (or less than), each connection switch on time becomes the minimum Tmin, and the discharge current measured can be minimized.

  The assembled battery voltage detection device of the present invention can also serve as a bypass circuit that equalizes the cell voltage to the cell voltage detection voltage converter, so that independent circuits are not required, and the circuit can be simplified. . In addition, since the voltage converter is connected to the battery cell via the connection switch, it is possible to increase the impedance of the voltage converter to suppress the self-discharge of the battery by reducing the on-time of the connection switch. Become. Furthermore, the variation in the input impedance of the voltage converter is canceled as a result of the cell voltage equalization by changing the connection switch on time. Therefore, according to the present invention, it is not necessary to reduce the number of dedicated bypass circuits, to increase the input impedance of the voltage converter, and to eliminate the need for highly accurate parts and adjustments for suppressing variations, so that low-cost cell voltage equalization is possible. Since the voltage detection apparatus which has a function is realizable, it is useful as a voltage detection apparatus of the assembled battery which connected the some secondary battery in series.

The block diagram which shows an example of a structure in Embodiment 1 of this invention Flowchart of configuration in Embodiment 2 of the present invention The block diagram which shows an example of a structure of the conventional assembled battery voltage detection apparatus

Explanation of symbols

11-14 Connection Switch 21-23 Voltage Converter 3 Cell Voltage Comparison / Connection Time Calculation Circuit 4 Cell Voltage Comparison / Bypass Time Calculation Circuit 51-53 Bypass Switch 61-63 Bypass Resistance 101-103 Battery Cell

Claims (2)

  In an assembled battery voltage detection device in which a plurality of battery cells are connected in series, a voltage converter is connected in parallel to each battery cell of the assembled battery via a connection switch, and an output of the voltage converter is compared. An assembled battery voltage detection device comprising a cell voltage comparison / connection time calculation circuit for controlling a connection time of the connection switch.   Initialize the voltage measurement time of all battery cells of the assembled battery, measure the cell voltage of each battery cell at the set measurement time, compare the measured cell voltage of each battery cell, and check the battery cell with the lowest cell voltage The next measurement time is set to Tmin, and it is determined whether or not the difference between the cell voltage of the other battery cell and the cell voltage of the minimum battery cell is less than the threshold value. A method for controlling a voltage detection apparatus for an assembled battery, characterized in that the time is set to Tmin and if the time is not less than or equal to the threshold value, the next measurement time of the battery cell is increased by ΔT.

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