JP2013013292A - Cell balancing circuit based on energy transfer via inductor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To equalize cell voltages in a battery module in a short time without wasting energy stored in cells by transferring energy between arbitrary cells.SOLUTION: A cell balancing circuit includes: a voltage detection section 2 for detecting each cell voltage of a battery module 1; an inductor L for energy transfer; a single cell connection switch group 4 capable of connecting the inductor between positive and negative electrodes of a selected single cell of the battery module; and a switch control section 3 for controlling the single cell connection switch group so as to connect the inductor between positive and negative electrodes of a predetermined single cell on the basis of each cell voltage detected by the voltage detection section. The switch control section controls the single cell connection switch group so as to make a charging path for a flow of current from a high voltage cell to the inductor, break the charging path in a predetermined time, make a discharging path for a flow of current from the inductor to a low voltage cell in parallel to breaking the charging path, and then break the discharging path in the predetermined time.

Description

  The present invention relates to a cell balance circuit for controlling the cell balance of a battery pack in which a plurality of secondary batteries are connected in series, that is, to control the equalization between cell voltages, and in particular, to each cell with high efficiency and in a short time. It is related with the improvement for eliminating the voltage difference between.

  In general, a battery pack using an assembled battery in which a plurality of secondary batteries are connected in series is configured to maintain the voltage of each cell uniformly by monitoring the cell voltage and adjusting the cell balance. ing. The reason why the cell balance needs to be adjusted is as follows.

  That is, there is a possibility that one cell in the assembled battery has a higher degree of deterioration than other cells due to cycle deterioration or aging deterioration. Such a deteriorated cell may have a smaller battery capacity than other cells. Therefore, compared with other cells, the degraded cell has a faster voltage rise during charging and a faster voltage drop during discharge. As a result, each cell voltage of the assembled battery is not uniform, the voltage of the deteriorated cell works dominantly on the charge / discharge control, and the battery capacity of the battery pack is apparently reduced. In addition, if charging / discharging is continued in this situation, the load concentrates on the deteriorated cell, so that the deterioration progresses at an accelerated rate, and the life of the battery pack may be shortened.

In order to solve this problem, the cell voltage is made uniform by discharging the energy of the high voltage cell through the resistor and making the voltage value of the high voltage cell approximately match the voltage value of the low voltage cell. Techniques are known. (Patent Document 1)
Non-Patent Document 1 discloses a technique for adjusting cell balance using energy storage and discharge by an inductance as energy transfer means.

JP-A-9-28042

11-12. Datasheet. [Online]. Texas Instruments Incorporated. SLUS887A-DECEMBER 2008-REVISED OCTOBER 2009. Search from the Internet: <URL: http: // focus.ti.com/docs/prod/folders/print/bq76pl102.html>

  However, in the method of controlling the cell balance by discharging through the resistor of Patent Document 1, energy stored in the cell is wasted.

  In the technique using the inductance of Non-Patent Document 1, the energy transfer destination is limited to adjacent cells. Therefore, in order to eliminate the voltage imbalance between cells not adjacent to each other, the circuit is repeatedly circulated. Therefore, there is a problem that adjustment takes a long time.

  The present invention solves the above problems and transfers energy between arbitrary cells, so that the energy stored in the cells is not wasted and each cell voltage in the assembled battery is made uniform in a short time. An object of the present invention is to provide a cell balance circuit.

  In order to achieve the above object, a cell balance circuit of the present invention is a circuit for adjusting cell balance in an assembled battery in which a plurality of secondary batteries are connected in series, and a voltage for detecting each cell voltage of the assembled battery. A detection unit, an energy transfer inductor, a single cell connection switch group including a plurality of switches capable of selecting a single cell of the assembled battery and connecting the inductor between positive and negative electrodes; A switch control unit that controls the single cell connection switch group so as to connect the inductor between positive and negative electrodes of a predetermined single cell of the assembled battery based on data of each cell voltage detected by the voltage detection unit. The switch control unit configures a charging path through which a current flows from a high voltage cell to the inductor, then disconnects the charging path after a predetermined time has elapsed, and disconnects the charging path. At the same time, after forming a discharge path through which current flows from the inductor to a low voltage cell having a lower voltage than the high voltage cell, the single cell connection switch group is controlled so that the discharge path is disconnected after a predetermined time has elapsed. To do.

  According to the above configuration, an arbitrary single cell is selectively connected to the inductor by the single cell connection switch group based on each cell voltage detected by the voltage detection unit, and the energy of the high voltage cell is stored in the inductor. By transferring the energy stored in the inductor to a low voltage cell, it is possible to make each cell voltage uniform efficiently without wasting energy stored in the cell.

Block diagram of a cell balance circuit in the first embodiment Flow chart showing operation of the cell balance circuit Operation timing diagram showing operation of the cell balance circuit Block diagram of a cell balance circuit in the first embodiment Operation timing diagram showing operation of the cell balance circuit

  The cell balance circuit of the present invention can take the following modes based on the above configuration.

  That is, the single cell connection switch group selects the single cell selection switch group for selecting the positive electrode and the negative electrode of the selected cell, and the terminal of the inductor that connects the selected positive electrode and the negative electrode. And a polarity selection switch group to be configured.

  Further, the switch control unit compares each cell voltage detected by the voltage detection unit to determine whether the voltage between the cells is uniform, and when the voltage between the cells is not uniform, The high voltage cell and the low voltage cell are extracted, and the charge path configuration and the subsequent discharge path configuration are defined as one charge / discharge cycle, and a voltage difference between the high voltage cell and the low voltage cell is predetermined. It can be set as the structure which repeats the said charging / discharging cycle until it becomes in the range.

  The voltage detection unit is configured in a general charge / discharge control unit that controls charging / discharging of the assembled battery, and the detected cell voltage is output from the charge / discharge control unit to the switch control unit. Can do. Alternatively, the charge / discharge control unit may include a voltage detection unit and a switch control unit.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<Embodiment 1>
FIG. 1 is a block diagram showing the configuration of the cell balance circuit according to the first embodiment. FIG. 2 is a flowchart showing the operation of the cell balance circuit, and FIG. 3 is an operation waveform diagram.

  In FIG. 1, the assembled battery 1 is configured by connecting a plurality of cells B1 to B4 in series. Each of the cells B1 to B4 is connected to the voltage detection unit 2, and the voltage of each cell is detected. The cell voltage data detected by the voltage detection unit 2 is supplied to the switch control unit 3. The switch control unit 3 is constituted by a microcomputer or the like and is connected so as to drive and control the single cell connection switch group 4. That is, the single cell connection switch group 4 includes switches SW <b> 1 to SW <b> 10 including semiconductor switch elements such as FETs, and ON / OFF of these switches is controlled by the switch control unit 3.

  The single cell connection switch group 4 selects one of the cells B1 to B4 and connects the positive and negative electrodes to the terminal Na or Nb of the inductor L, respectively. Therefore, one end of the switches SW1 to SW10 is connected to the plus electrode or the minus electrode of the cells B1 to B4. On the other hand, the other ends of the switches SW1, SW3, SW5, SW7, and SW9 are connected to the terminal Na, and the other ends of the switches SW2, SW4, SW6, SW8, and SW10 are connected to the terminal Nb. The on / off operation of these switches is controlled by the switch control unit 3 in accordance with the charge / discharge timing.

  An example of the operation of the cell balance circuit having the above configuration will be described with reference to FIGS. 1 to 3 by taking as an example the case where the voltage of the cell B1 of the assembled battery 1 is high and the voltage of the cell B4 is low. 3A shows the ON / OFF timing of the switches SW7 and SW10, and FIG. 3B shows the waveform of the charging current from the cell B1 to the inductor L. FIG. (C) shows the ON / OFF timing of the switches SW2 and SW3, and (d) shows the waveform of the discharge current from the inductor L to the cell B4. (E) shows the waveform of the current flowing through the inductor L.

  In the flowchart of FIG. 2, when the operation starts, the switch control unit 3 compares the voltages of the cells B1 to B4 of the assembled battery 1 transmitted from the voltage detection unit 2 (step S1). Based on the result, it is determined whether or not the voltages of all the cells are uniform (step S2). Any method can be used as the determination method. In other words, the condition for determining that the cell voltage is uniform may be set as appropriate. For example, it is determined that the difference between the cell voltages with respect to the average voltage of all the cells is within a predetermined allowable range. Can do.

  If the voltages of all the cells are uniform in the determination result (Yes), the operation is terminated (step S8). When the cell voltages are not uniform (No), the high voltage cell BH and the low voltage cell BL are extracted (step S3). The extraction method of the cell BH and the cell BL can be set as appropriate. For example, the cell BH may be a cell having the highest voltage in the assembled battery 1, and the cell BL may be the cell having the lowest voltage. In this description, BH is the cell B1, and BL is the cell B4.

  In the following flow, the switch control unit 3 controls the ON / OFF of SW1 to SW10 of the single cell connection switch group 4, thereby configuring a path for charging the energy of the cell B1 to the inductor L (step S4). Next, a path for discharging the energy charged in the inductor L to the cell B4 is formed (step S5).

  The path for charging the energy of the cell B1 to the inductor L is configured when the switches SW7 and SW10 of the single cell connection switch group 4 are turned on in FIG. The current path at this time is <positive electrode of cell B1> → <terminal Na of inductor L> → <inductor L terminal Nb> → <negative electrode of cell B1>. As a result, the energy of cell B1 is charged in inductor L. The In FIG. 3, it corresponds to the ON period in (a), the charging current Ic shown in (b) flows from the cell B1, and the current in the first half (period t) shown in (e) flows in the inductor L.

  The path for discharging the energy charged in the inductor L to the cell B4 is configured when the switches SW2 and SW3 are turned on from the single cell connection switch group 4 in FIG. The current path at this time is <terminal Nb of the inductor L> → <positive electrode of the cell B4> → <negative electrode of the cell B4> → <terminal Na of the inductor L>. As a result, the energy charged in the inductor L is the cell B4. Discharged. In FIG. 3, it corresponds to the ON period in (c), the charging current Id shown in (d) flows in the cell B4, and in the inductor L, the latter half current shown in (e) flows.

  As described above, in order to form a path through which the energy of the cell B1 is charged to the inductor L, the switch control unit 3 turns on SW7 and SW10 simultaneously for a certain time, and charges the inductor L with the energy of the cell B1. It is necessary to set the inductance of the inductor L according to the settings of the transfer energy between the target cells at the time of energy transfer, the energy transfer time, the current value flowing from the target cell to the inductor L, and the like.

  After a certain time (period t), the switch control unit 3 disconnects SW7 and SW10, and at the same time turns SW2 and SW3 ON for a certain time to form a path for discharging the energy charged in the inductor L to the cell B4. The energy stored in the inductor L is discharged to the cell B4. Further, after a predetermined time, the switch control unit 3 turns off SW2 and SW3.

  Each time the above charge / discharge cycle is completed, the voltage of the cell B1 (BH) is compared with the voltage of the cell B4 (BL) (step S6). If the voltage of the cell B1 is not equal to the voltage of the cell B4 (No in step S7), the process returns to step S4 and the above operation is repeated. As a result, energy is transferred again from the high voltage cell B1 toward the low voltage cell B4. Note that two cell voltages are equivalent, for example, can be set as the voltage difference is within a predetermined tolerance, but according to the definition of the state in which all the battery voltages are equal, as described above. It is desirable to set.

  By repeating this operation, the energy of the cell B1 connected at the time of charging continues to decrease, and the energy of the cell B4 connected at the time of discharging continues to increase. Accordingly, the cell voltage is monitored, and the operation is stopped when the voltages of the two cells become equal. That is, if Yes in step S7, the process returns to step S1.

  In step S1, the voltages of all the cells are compared again, and the process proceeds to step S2, where it is determined whether or not the voltages of all the cells are uniform. If the voltages of all the cells are uniform (Yes), the operation is terminated (step S8). If it is not uniform (No), the highest voltage cell BH and the lowest voltage cell BL are extracted again (step S3). Then, the process proceeds to step S4, and the operations up to step S7 are repeated as described above.

  As described above, the cell balance circuit in the present embodiment transfers energy from a cell having a high voltage to a cell having a low voltage via an inductor between arbitrary cells, so that energy is not efficiently wasted. It is possible to make the cell voltage uniform.

<Embodiment 2>
FIG. 4 is a block circuit diagram showing a configuration of the cell balance circuit according to the second embodiment. FIG. 5 is an operation waveform diagram representing the operation of this cell balance circuit. The present embodiment has a configuration in which the single cell connection switch group 4 in FIG. 1 is replaced with a combination of a single cell selection switch group 5 and a polarity selection switch group 6. The overall flow of the switch switching operation is the same as that of the first embodiment described with reference to FIG.

  The single cell selection switch group 5 and the polarity selection switch group 6 are composed of semiconductor switch elements such as FETs, and are driven and controlled by a switch control unit 7 including a microcomputer based on the output of the voltage detection unit 2. In this configuration, the positive electrode or the negative electrode of any cell in the assembled battery 1 is selected by the switches SW11 to SW15 of the single cell selection switch group 5, and is selected by the switches SW16 to SW19 of the polarity selection switch group 6 The electrode is connected to the terminal Na or Nb.

  An example of the operation of the cell balance adjustment with this configuration will be described with reference to FIG. 5, taking as an example the case where the voltage of the cell B1 is high and the voltage of the cell B4 is low. In FIG. 5, (a) shows the ON / OFF timing of the switches SW14, SW15, SW16, and SW19, and (b) shows the waveform of the charging current from the cell B1 to the inductor L. (C) shows the ON / OFF timing of the switches SW11, SW12, SW19, and SW16, and (d) shows the waveform of the discharge current from the inductor L to the cell B4. (E) shows the waveform of the current flowing through the inductor L.

  The switch control unit 7 determines whether the cell voltage is uniform based on each cell voltage of the assembled battery 1 transmitted from the voltage detection unit 2. Any method may be used as the determination method. When the cell voltage is not uniform in the determination result, a cell having a high voltage and a cell having a low voltage are selected. In the present embodiment, it is assumed that the cell B1 of the assembled battery 1 is selected as a high voltage cell, and the cell B4 is selected as a low voltage cell.

  Next, the switch control unit 7 selectively turns on the switches of the single cell selection switch group 5 and the polarity selection switch group 6 to form a path for charging the energy of the cell B1 to the inductor L. A path for discharging the energy charged in the inductor L to the cell B4 is formed.

  In FIG. 4, the path for charging the energy of the cell B1 to the inductor L is configured when the switches SW14 and SW15 of the single cell selection switch group 5 and the SW16 and SW19 of the polarity selection switch group 6 are selectively turned on. . The current path at this time is <positive electrode of cell B1> → <terminal Na of inductor L> → <inductor L terminal Nb> → <negative electrode of cell B1>. As a result, the energy of cell B1 is charged in inductor L. The In FIG. 5, it corresponds to the ON period in (a), the charging current Ic shown in (b) flows from the cell B1, and in the inductor L, the current in the first half (period t) shown in (e) flows.

  The path for discharging the energy charged in the inductor L to the cell B4 is configured when the SW11 and SW12 of the single cell selection switch group 5 and the SW16 and SW19 of the polarity selection switch group 6 are selectively turned on in FIG. Is done. The current path at this time is <terminal Nb of the inductor L> → <positive electrode of the cell B4> → <negative electrode of the cell B4> → <terminal Na of the inductor L>. As a result, the energy charged in the inductor L is the cell B4. Discharged. In FIG. 5, it corresponds to the ON period in (c), the charging current Id shown in (d) flows to the cell B4, and in the inductor L, the latter half current shown in (e) flows.

  As described above, in order to form a path through which the energy of the cell B1 is charged in the inductor L, the switch control unit 7 simultaneously turns on SW14, SW15, SW16, and SW19 for a certain period of time and turns the energy of the cell B1 into the inductor L. Charge. It is necessary to set the inductance of the inductor L according to the settings of the transfer energy between the target cells at the time of energy transfer, the energy transfer time, the current value flowing from the target cell to the inductor L, and the like.

  After a certain time (period t), the switch control unit 7 disconnects SW14, SW15, SW16, and SW19, and at the same time, forms a path for discharging the energy charged in the inductor L to the cell B4, SW11, SW12, SW16. , SW19 is turned on for a certain time, and the energy stored in the inductor L is discharged to the cell B4. Further, after a predetermined time, the switch control unit 7 turns off SW11, SW12, SW16, and SW19.

  Every time the above charge / discharge of one cycle is completed, the voltage of the cell B1 is compared with the voltage of the cell B4. If the voltage of the cell B1 is not equal to the voltage of the cell B4, the above charge / discharge operation is repeated. As a result, energy is transferred again from the high voltage cell B1 toward the low voltage cell B4.

  By repeating this operation, the energy of the cell B1 connected at the time of charging continues to decrease, and the energy of the cell B4 connected at the time of discharging continues to increase. Accordingly, the cell voltage is monitored, and the operation is stopped when the voltages of the two cells become equal. In the next operation, a cell having a high voltage and a cell having a low voltage are selected again from the remaining cells, and the operation of transferring charges from the cell having a high voltage to the cell having a low voltage is repeated. The operation is stopped based on the voltage monitoring result as in the flow shown in FIG.

  As described above, the cell balance circuit in the present embodiment transfers energy from a cell having a high voltage to a cell having a low voltage via an inductor between arbitrary cells, so that energy is not efficiently wasted. It is possible to make the cell voltage uniform.

  The cell balance circuit of the present invention can efficiently equalize cell voltages without wasting energy, and uses secondary batteries such as consumer secondary battery packs and commercial secondary battery packs. This is useful for charging and discharging systems.

DESCRIPTION OF SYMBOLS 1 assembled battery 2 voltage detection part 3, 7 switch control part 4 single cell connection switch group 5 single cell selection switch group 6 polarity selection switch group B1-B4 cell SW1-SW19 switch L inductor

Claims (3)

A cell balance circuit for adjusting cell balance in an assembled battery in which a plurality of secondary batteries are connected in series,
A voltage detector for detecting each cell voltage of the assembled battery;
An inductor for energy transfer;
A single cell connection switch group composed of a plurality of switches capable of selecting a single cell of the assembled battery and connecting the inductor between positive and negative electrodes;
A switch control unit that controls the single cell connection switch group to connect the inductor between positive and negative electrodes of a predetermined single cell of the assembled battery based on data of each cell voltage detected by the voltage detection unit; Prepared,
The switch control unit
After configuring a charging path through which current flows from the high voltage cell to the inductor, the charging path is disconnected after a predetermined time has elapsed,
The single cell is configured to disconnect the discharge path after a predetermined time has elapsed after forming a discharge path through which current flows from the inductor to a low voltage cell having a voltage lower than that of the high voltage cell at the same time as disconnecting the charging path. A cell balance circuit for controlling a connection switch group.   The single cell connection switch group includes a single cell selection switch group for selecting a positive electrode and a negative electrode of the selected cell, and a polarity for selecting a terminal of the inductor that connects the selected positive electrode and the negative electrode. The cell balance circuit according to claim 1, wherein the cell balance circuit is configured in combination with a selection switch group.   The switch control unit compares each cell voltage detected by the voltage detection unit to determine whether the voltage between the cells is uniform. When the voltage between the cells is not uniform, The voltage cell and the low voltage cell are extracted, and the voltage path difference between the high voltage cell and the low voltage cell is within a predetermined range, with the configuration of the charging path and the configuration of the subsequent discharging path as one charge / discharge cycle. The cell balance circuit according to claim 1, wherein the charge and discharge cycle is repeated until

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