Abstract:
A feeding apparatus includes a feeding unit configured to feed power in a non-contact manner to the charging apparatus mounted on a vehicle and a feeding control unit that receives vehicle detection information from a sensor configured to transmit vehicle detection information when a vehicle is detected. The apparatus executes control so that the feeding unit provided in the feeding apparatus feeds first power determined for each feeding apparatus so as to specify the feeding apparatus, transmits charging start information indicating a start of charging when feeding unit specifying information containing information to indicate the power level at which power is received from the feeding unit is received from the charging apparatus, and the received power level is determined to be within a specific power range, and executes control so that the feeding unit feeds second power in order to charge a battery unit of the charging apparatus.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a cell balance apparatus and cell balance method for equalizing voltages of a plurality of serially connected accumulator elements (hereinafter referred to as cells). 
       BACKGROUND ART 
       [0002]    In a battery having a plurality of serially connected cells, cell balancing is performed to equalize voltages of the cells for effective utilization of power and long service life. In one technique, in order to perform cell balancing, each cell is connected in parallel to a resistor so that electricity can be discharged from cells in a high-voltage state through resistors, but such a technique has a problem of large current loss due to consumption of discharged current at the resistors. 
         [0003]    A known cell balance circuit that equalizes voltages of a plurality of cells with a low loss is a circuit that uses switch elements and inductors but does not use a resistor (see for example patent literature 1). 
         [0004]      FIG. 5  illustrates an exemplary circuit that performs cell balancing using switch elements and inductors. In  FIG. 5 , Ce 1 , Ce 2 , Ce 3 , Ce 4 , and Ce 5  indicate cells, L 12 , L 23 , L 34 , and L 45  indicate inductors, and Sw 12 , Sw 21 , Sw 23 , Sw 32 , Sw 34 , Sw 43 , Sw 45 , and Sw 54  indicate switch elements. 
         [0005]    As illustrated in  FIG. 5 , five cells Ce 1 -Ce 5  with the same capacity are serially connected, and switch elements Sw 12 -Sw 54  are connected in parallel to the serially connected cells Ce 1 -Ce 5 . In particular, the switch element Sw 12  is connected in parallel to the cell Ce 1 ; the switch elements Sw 21  and Sw 23  are connected in parallel to the cell Ce 2 ; the switch elements Sw 32  and Sw 34  are connected in parallel to the cell Ce 3 ; the switch elements Sw 43  and Sw 45  are connected in parallel to the cell Ce 4 ; the switch element Sw 54  is connected in parallel to the cell Ce 5 . 
         [0006]    The inductor L 12  has an end connected to a connecting point between the cells Ce 1  and Ce 2 , and another end connected to a connecting point between the switch elements Sw 12  and Sw 21 . The inductor L 23  has an end connected to a connecting point between the cells Ce 2  and Ce 3 , and another end connected to a connecting point between the switch elements Sw 23  and Sw 32 . The inductor L 34  has an end connected to a connecting point between the cells Ce 3  and Ce 4 , and another end connected to a connecting point between the switch elements Sw 34  and Sw 43 . The inductor L 45  has an end connected to a connecting point between the cells Ce 4  and Ce 5 , and another end connected to a connecting point between the switch elements Sw 45  and Sw 54 . 
         [0007]    In such a cell balance circuit, two adjacent cells Ce 1  and Ce 2  are paired with each other; two adjacent cells Ce 2  and Ce 3  are paired with each other; two adjacent cells Ce 3  and Ce 4  are paired with each other; two adjacent cells Ce 4  and Ce 5  are paired with each other; and four switching converters SC 12 , SC 23 , SC 34 , and SC 45  are configured to transfer charges between the cells of each pair. For each of the four switching converters SC 12 , SC 23 , SC 34 , and SC 45 , the voltages of the two cells of the pair are compared with each other; a switch element connected in parallel to the cell with the higher voltage is put in a conduction (on) state, and a switch element connected in parallel to the cell with the lower voltage is put in a cut-off (off) state, thereby equalizing the voltages of the cells of each pair. 
         [0008]    Referring to, for example, the pair of cells Ce 1  and Ce 2 , when the cell Ce 1  has a higher voltage than the cell Ce 2 , the switch element Sw 12  is put in an on state, and the switch element Sw 21  is put in an off state. Putting the switch element Sw 12  in the on state forms a closed loop of “cell Ce 1 →switch element Sw 12 →inductor L 12 →cell Ce 1 ”, thereby causing electric energy to migrate from the cell Ce 1  to the inductor L 12 . 
         [0009]    Subsequently, putting the switch element Sw 12  in the off state and the switch element Sw 21  in the on state causes the electric energy that has migrated to the inductor L 12  to migrate to the cell Ce 2  through a closed circuit that passes through the switch Sw 21 . In such an operation, charges are transferred from the cell Ce 1 , i.e., a high-voltage cell, to the cell Ce 2 , i.e., a low-voltage cell, so that the voltages of the cells Ce 1  and Ce 2  can be equalized. 
         [0010]    Referring again to the pair of cells Ce 1  and Ce 2 , when the cell Ce 2  and the cell Ce 1  respectively have a high voltage and a low voltage, the switch element Sw 21  is put in the on state, and the switch element Sw 12  is put in the off state. This forms a closed loop of “cell Ce 2 →inductor L 12 →switch element Sw 21 →cell Ce 2 ”, thereby causing electric energy to migrate from the cell Ce 2  to the inductor L 12 . 
         [0011]    Subsequently, putting the switch element Sw 21  in the off state and the switch element Sw 12  in the on state causes the electric energy that has migrated to the inductor L 12  to migrate to the cell Ce 1  through a closed circuit that passes through the switch Sw 12 , and charges are transferred from the cell Ce 2  to the cell Ce 1 , so that the voltages of the cells Ce 1  and Ce 2  can be equalized. 
         [0012]    As in the operation above, for the pair of adjacent cells Ce 2  and Ce 3 , the pair of adjacent cells Ce 3  and Ce 4 , and the pair of adjacent cells Ce 4  and Ce 5 , the voltages of the two cells of each of the pairs are equalized to enable cell balancing such that the voltages of serially connected cells are equalized without a current being consumed by a resistor. 
       CITATION LIST 
     Patent Literature 
       [0000]    
       
         Patent literature 1: Japanese Laid-open Patent Publication No. 2010-220373 
       
     
       SUMMARY OF INVENTION 
     Technical Problem 
       [0014]    For a battery having many (more than two) serially connected cells, switching-converter-based conventional cell balancing is performed such that the voltages of two adjacent cells are compared, and the direction of a charge transfer is determined in accordance with the comparison result, thereby driving or stopping a switching converter. Hence, due to, for example, the consecutively exerted influence of a variation in the voltage of surrounding cells, a repetitive change in the voltages of an adjacent cell from high to low or vice versa, or a useless repetitive-reciprocating-motion of charges, charge transfers as a whole are not performed efficiently, leading to cell balancing requiring a long time. In view of such a problem, the present invention provides a cell balance apparatus and cell balance method for improving the operation efficiency of cell balancing so as to shorten the time required for cell balancing. 
       Solution to Problem 
       [0015]    A cell balance apparatus in accordance with the invention is a cell balance apparatus wherein, for at least three serially connected accumulator elements (cells), one end of an inductor is connected to a connecting point between adjacent cells, another end of the inductor is connected to another end of each of the adjacent cells via a switch element, and a charge is transferred between the adjacent cells via on/off control of the switch elements so as to equalize the voltages of the cells, the cell balance apparatus including: average-voltage calculating unit to divide the plurality of serially connected cells into two groups while maintaining the sequential order of the serial connection, and to calculate the average voltage of cells within each group; average-voltage comparing unit to compare the average voltages of the two groups calculated by the average-voltage calculating means; and on/off control unit to perform on/off control of the switch elements in accordance with the comparison result provided by the average-voltage comparing means in a manner such that a charge is transferred from a cell located at a border of the group with the higher average voltage to an adjacent cell located at a border of the group with the lower average voltage. 
         [0016]    In such a configuration, all of the cells are divided into two groups, with an inductor of a driven switching converter serving as a border between these groups, and the direction of a charge transfer is determined by comparing the average voltages of the two groups, so that the direction of a charge transfer for cell balancing can be uniquely determined in accordance with non-uniformity of cell voltages over the entirety of a battery, thereby minimizing the amount of a charge transfer for cell balancing. 
       Advantageous Effects of Invention 
       [0017]    In the present invention, the direction of a charge transfer for cell balancing is uniquely determined without being affected by a variation in the voltage of surrounding cells. This prevents a useless repetitive-reciprocating-motion of charges between adjacent cells and thus minimizes the amount of a charge transfer. Hence, cell balancing can be performed efficiently, thereby improving the efficiency in equalizing cell voltages and shortening the time required to perform cell balancing. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0018]      FIG. 1  illustrates an exemplary configuration of a cell balance apparatus in accordance with the present invention; 
           [0019]      FIG. 2  illustrates examples of the individual average voltages of two groups of cells; 
           [0020]      FIG. 3  illustrates a first example of a cell balance method in accordance with the invention; 
           [0021]      FIG. 4  illustrates a second example of a cell balance method in accordance with the invention; and 
           [0022]      FIG. 5  illustrates an exemplary circuit that performs cell balancing. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0023]    Embodiments will be described in detail below with reference to the drawings. Descriptions will be given of the embodiments with reference to exemplary operations of cell balancing for five serially connected cells, but the present invention is not limited to this but is applicable to cell balancing for three or more serially connected cells. 
         [0024]      FIG. 1  illustrates an exemplary configuration of a cell balance apparatus. In  FIG. 1 , the configurations and operations of individual switching converters SC 12 , SC 23 , SC 34 , and SC 45  are similar to those described above with reference to  FIG. 5 , and overlapping descriptions are omitted herein. 
         [0025]    A cell balance apparatus in accordance with the invention includes a two-group average voltage calculating unit  1 - 1 , a two-group average voltage comparing unit  1 - 2 , a switch-element on/off controlling unit  1 - 3 , and a controlling unit  1 - 4 , such that all cells can be divided into two groups with an inductor of a driven switching converter serving as a border between these groups, such that the direction of a charge transfer can be determined by comparing the average voltages of the two groups, and such that charges can be transferred in that direction. 
         [0026]    The two-group average voltage calculating unit  1 - 1  receives the cell voltages of individual cells Ce 1 , Ce 2 , Ce 3 , Ce 4 , and Ce 5  from voltage measuring means (not illustrated) for these cells. The two-group average voltage calculating unit  1 - 1  divides at least three serially connected cells sequentially into two groups while maintaining the sequential order of the serial connection, and calculates the average voltage of cells within each group. 
         [0027]    The two-group average voltage comparing unit  1 - 2  compares the average voltages of two groups calculated by the two-group average voltage calculating unit  1 - 1 . The switch-element on/off controlling unit  1 - 3  performs on/off control of switch elements in accordance with the comparison result provided by the two-group average voltage comparing unit  1 - 2  in a manner such that a charge is transferred from a cell located at a border of the group with the higher average voltage to an adjacent cell located at a border of the group with the lower average voltage. 
         [0028]    The two-group average voltage calculating unit  1 - 1  may be configured to divide at least three serially connected cells sequentially into two groups while maintaining the sequential order of the serial connection, and to calculate the average voltage of cells of one of the groups and the average voltage of all of the cells. The two-group average voltage comparing unit  1 - 2  may be configured to compare the average voltage of one of the groups with the average voltage of all of the cells. 
         [0029]    In this case, the switch-element on/off controlling unit  1 - 3  performs on/off control of switch elements in a manner such that, when the average voltage of one of the groups is higher than the average voltage of all of the cells, a charge is transferred from a cell located at a border of the one group to an adjacent cell located at a border of the other group, and such that, when the average voltage of the one group is lower than the average voltage of all of the cells, a charge is transferred to the cell located at the border of the one group from the adjacent cell located at the border of the other group. 
         [0030]    The controlling unit  1 - 4  controls operations of the aforementioned function units  1 - 1  to  1 - 3  and, for the switch-element on/off controlling unit  1 - 3 , controls the timing of on/off control of switch elements performed for a charge transfer between adjacent cells located at the borders of groups. 
         [0031]      FIG. 2  illustrates exemplary average voltages of two individual groups, the groups being obtained by dividing cells Ce 1 -Ce 5  into two groups. The grouping manner is such that five serially connected cells Ce 1 -Ce 5  are divided successively into two groups while maintaining the sequential order of the serial connection. Then, the average voltage of cells within each group is calculated. Assume that the average voltage of all of the cells is a reference voltage of 0V and that the cell Ce 1  has a voltage of −1V; the cell Ce 2 , −2V; the cell Ce 3 , +1V; the cell Ce 4 , +3V; and the cell Ce 5 , −1V. 
         [0032]    (a) in  FIG. 2  depicts an example in which a group consisting of only the cell Ce 1  has an average voltage of −1V, and a group consisting of the cells Ce 2 -Ce 5  has an average voltage of +0.25V. (In this case, a border between the groups is located between the cells Ce 1  and Ce 2 . The cells Ce 1  and Ce 2  are cells located at the borders of the groups and are also adjacent cells located at the border between the two groups.) 
         [0033]    (b) in  FIG. 2  depicts an example in which a group consisting of the cells Ce 1 -Ce 2  has an average voltage of −1.5V, and a group consisting of the cells Ce 3 -Ce 5  has an average voltage of +1V. (In this case, a border between the groups is located between the cells Ce 2  and Ce 3 . The cells Ce 2  and Ce 3  are cells located at the borders of the groups and are also adjacent cells located at the border between the two groups.) 
         [0034]    (c) in  FIG. 2  depicts an example in which a group consisting of the cells Ce 1 -Ce 3  has an average voltage of −0.67V, and a group consisting of the cells Ce 4 -Ce 5  has an average voltage of +1V. 
         [0035]    (d) in  FIG. 2  depicts an example in which a group consisting of the cells Ce 1 -Ce 4  has an average voltage of +0.25V, and a group consisting of only the cell Ce 5  has an average voltage of −1V. 
         [0036]    The switching converter SC 12  lies between the cells Ce 1  and Ce 2 . The switching converter SC 23  lies between the cells Ce 2  and Ce 3 . The switching converter SC 34  lies between the cells Ce 3  and Ce 4 . The switching converter SC 45  lies between the cells Ce 4  and Ce 5 . 
         [0037]    Referring to the switching converter SC 23 , as indicated by (b) in  FIG. 2 , the average voltage of the cells Ce 1  and Ce 2 , −1.5V, is compared with the average voltage of the cells Ce 3 -Ce 5 , +1V, and the switching converter SC 2  causes a current to flow from the cell Ce 3  belonging to the group with the higher average voltage (a cell located at the border of the higher-average-voltage group) to the cell Ce 2  belonging to the group with the lower average voltage (an adjacent cell located at the border of the lower-average-voltage group). 
         [0038]    Outflow/inflow of a current caused by the switching converter SC 23  stops when the average voltage of the cells Ce 1  and Ce 2  becomes equal to or greater than the average voltage of the cells Ce 3 -Ce 5 . Alternatively, outflow/inflow of a current may stop when a difference between the average voltage of all of the cells and either of the average voltage of the cells Ce 1  and Ce 2  or the average voltage of the cells Ce 3 -Ce 5  becomes equal to or less than a predetermined threshold. 
         [0039]    Similarly, the other switching converters, i.e., the switching converters SC 12 , SC 34 , and SC 45 , each determine the direction of a charge transfer according to the average voltages of the cells of the groups sandwiching the switching converter. The switching converters SC 12 , SC 23 , SC 34 , and SC 45  may each be configured to drive switch elements simultaneously or in parallel. 
         [0040]    In this case, operations of each of the switching converters are not affected by operations of the other switching converters. This is because, referring to, for example, the switching converter SC 23 , operations of the switching converter SC 23  relate to only a charge transfer between the cells Ce 2  and Ce 3 , and this charge transfer does not change the average voltages of the groups of the other grouping manners. 
         [0041]    That is, for the group consisting of the cells Ce 2 -Ce 5  of the grouping manner of (a) in  FIG. 2 , the charge transfer between the cells Ce 2  and Ce 3  corresponds to a charge transfer between cells within the same group, and hence a change is not made to the average voltage of the group consisting of the cells Ce 2 -Ce 5 . Similarly, for the group consisting of the cells Ce 1 -Ce 3  of the grouping manner of (c) in  FIG. 2 , the charge transfer between the cells Ce 2  and Ce 3  corresponds to a charge transfer between cells within the same group, and hence a change is not made to the average voltage of the group consisting of the cells Ce 1 -Ce 3 . For the group consisting of the cells Ce 1 -Ce 4  of the grouping manner of (d) in  FIG. 2 , the charge transfer between the cells Ce 2  and Ce 3  corresponds to a charge transfer between cells within the same group, and hence a change is not made to the average voltage of the group consisting of the cells Ce 1 -Ce 4 . 
         [0042]    Charge transfers caused by the switching converters SC 12 , SC 34 , and SC 45  also do not affect operations of the switching converter SC 23 . That is, the switching converter  12  causes only the charge transfer between the cells Ce 1  and Ce 2 , the switching converter SC 34  causes only the charge transfer between the cells Ce 3  and Ce 4 , and the switching converter SC 45  causes only the charge transfer between the cells Ce 4  and Ce 5 , with the result that the average voltages of the group consisting of the cells Ce 1  and Ce 2  and the group consisting of the cells Ce 3 -Ce 5  are not affected. 
         [0043]    Hence, the switching converters SC 12 , SC 23 , SC 34 , and SC 45  can be driven independently from each other, and the controlling unit  1 - 4  can drive the switching converters SC 12 , SC 23 , SC 34 , and SC 45  simultaneously or in parallel, thereby shortening the time for the operations of cell balancing. 
       Example 1 
       [0044]      FIG. 3  illustrates a first example of the flow of a cell balance method in accordance with the invention.  FIG. 3  depicts exemplary operations of a charge transfer for m-th and (m+1)-th cells of serially connected cells, the m-th and (m+1)-th cells being adjacent to each other. Assume that n cells are present. In the first example, first, an average voltage Avm of a group consisting of first to m-th cells and an average voltage Avm+1 of a group consisting of (m+1)-th to n-th cells are calculated, and Avm and Avm+1 are compared with each other (S 3 - 1 ). 
         [0045]    After the comparing, when Avm is greater than Avm+1, ON/OFF control of a switch element is performed to transfer a charge from the m-th cell to the (m+1)-th cell (S 3 - 2 ). After the charge is transferred, Avm and Avm+1 are calculated and compared with each other (S 3 - 3 ). When Avm is greater than Avm+1 again (YES in S 3 - 4 ), ON/OFF control of a switch element is performed again to transfer a charge from the m-th cell to the (m+1)-th cell (S 3 - 2 ). When Avm becomes equal to or less than Avm+1 (NO in S 3 - 4 ), the operations end. 
         [0046]    After the comparing, when Avm is less than Avm+1, ON/OFF control of a switch element is performed to transfer a charge from the (m+1)-th cell to the m-th cell (S 3 - 5 ). After the charge is transferred, Avm and Avm+1 are calculated and compared with each other (S 3 - 6 ). When Avm is less than Avm+1 again (YES in S 3 - 7 ), ON/OFF control of a switch element is performed again to transfer a charge from the (m+1)-th cell to the m-th cell (S 3 - 6 ). When Avm becomes equal to or greater than Avm+1 (NO in S 3 - 7 ), the operations end. 
       Example 2 
       [0047]      FIG. 4  illustrates a second example of the flow of a cell balance method in accordance with the invention.  FIG. 4  also depicts exemplary operations of a charge transfer for m-th and (m+1)-th cells of serially connected cells, the m-th and (m+1)-th cells being adjacent to each other. Assume that n cells are present. In the second example, the average voltage of cells of only one of two groups and the average voltage of all of the cells are calculated and compared with each other to determine the direction of a charge transfer. 
         [0048]    When the average voltage of one of the two groups is less than the average voltage of the other group, the average voltage of the one group is necessarily less than the average voltage of all of the cells, and the average voltage of the other group is necessarily greater than the average voltage of all of the cells. 
         [0049]    Hence, unlike the case in the first example, in which the average voltages of two groups are compared, the average voltage of one group and the average voltage of all of the cells may be compared to determine the direction of a charge transfer. The second example is based on such a principle of operation. 
         [0050]    The following will describe the operation flow of the second example with reference to  FIG. 4 . An average voltage Avn of n cells is calculated (S 4 - 1 ). An average voltage Avm of a group consisting of first to m-th cells is calculated, and Avm and Avn are compared with each other (S 4 - 2 ). 
         [0051]    After the comparing, when Avm is greater than Avn, ON/OFF control of a switch element is performed to transfer a charge from the m-th cell to the (m+1)-th cell (S 4 - 3 ). After the charge is transferred, Avm is calculated and compared with Avn (S 4 - 4 ). When Avm is greater than Avn again (YES in S 4 - 5 ), ON/OFF control of a switch element is performed again to transfer a charge from the m-th cell to the (m+1)-th cell (S 4 - 3 ). When Avm becomes equal to or less than Avn (NO in S 4 - 5 ), the operations end. 
         [0052]    After the comparing, when Avm is less than Avn, ON/OFF control of a switch element is performed to transfer a charge from the (m+1)-th cell to the m-th cell (S 4 - 6 ). After the charge is transferred, Avm is calculated and compared with Avn (S 4 - 7 ). When Avm is less than Avn again (YES in S 4 - 8 ), ON/OFF control of a switch element is performed again to transfer a charge from the (m+1)-th cell to the m-th cell (S 4 - 6 ). When Avm becomes equal to or greater than Avn (NO in S 4 - 8 ), the operations end. 
         [0053]    The cell balancing according to each of the aforementioned two ways of grouping based on a charge transfer between adjacent cells at the borders of groups may be simultaneously performed or may be performed in chronological order between adjacent cells located at the group border of each of the ways of grouping. It should be noted that the invention is not limited to the embodiments above, and various configurations or embodiments can be applied without departing from the spirit of the invention.