Module balancing method and battery management system using the same

Abstract

The present invention relates to a module balancing method and a battery management system to which the same is applied. The battery management system of the present invention includes a first module including a plurality of center cells having a potential belonging to a center potential range among a plurality of battery cells connected in series, a second module including at least one lower cell having a potential belonging to a lower potential range, and a third module including at least one upper cell having a potential belonging to an upper potential range, and a control unit that calculates module voltages of the first module, the second module, and the third module based on the cell voltages of each of the plurality of battery cells, determines an energy transfer direction based on the calculated module voltages, and controls the module balancing in accordance with the determined energy transfer direction.

Description

[Technical Field]

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0184461 dated December 26, 2022 and Korean Patent Application No. 10-2023-0190074 dated December 22, 2023, and all contents disclosed in the documents of said Korean patent applications are incorporated herein by reference.

[0002] The present invention relates to a module balancing method and a battery management system to which the same is applied. [Background technology]

[0003] Battery cell balancing (hereinafter referred to as "cell balancing") is a method for reducing voltage differences between multiple battery cells that occur during the charge / discharge voltage dynamics of multiple series-connected cells. For example, during charging, if the cell voltage of the first battery cell reaches a reference voltage (e.g., 4.2V) and the cell voltage of the second battery cell is 4.0V, charging must be stopped to prevent overcharging of the first battery cell. However, in this case, the second battery cell is not fully charged, resulting in a decrease in the overall battery charge capacity. When voltage differences between multiple battery cells occur, cell balancing is performed. A circuit capable of discharging multiple cells (hereinafter referred to as "cell balancing circuit") can be implemented in a Battery Management System (hereinafter referred to as "BMS") to reduce voltage differences between multiple battery cells.

[0004] There are two types of cell balancing: passive cell balancing and active cell balancing. Passive cell balancing is a method of selecting battery cells with relatively high voltages and dissipating the charge energy of the selected battery cells through a discharge resistor. Active cell balancing is a method of transferring the charge energy of battery cells with relatively high voltages to battery cells with low voltages.

[0005] On the other hand, passive cell balancing has the disadvantage of low efficiency because energy is lost as heat in the discharge resistor. Active cell balancing is superior to passive cell balancing in terms of energy efficiency, but has the disadvantage of being very complex, taking up a lot of space in the battery system, increasing the number of components and resulting in high costs. Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention provides a method for performing active module balancing between battery modules using a simple charge equalization circuit, and a battery management system using the same. [Means for solving the problem]

[0007] A battery management system according to one aspect of the present invention includes a first module including a plurality of center cells having a potential belonging to a center potential range among a plurality of battery cells connected in series, a second module including at least one lower cell having a potential belonging to a lower potential range, and a third module including at least one upper cell having a potential belonging to an upper potential range, and a control unit that calculates module voltages of the first module, the second module, and the third module based on the cell voltages of each of the plurality of battery cells, determines an energy transfer direction based on the calculated module voltages, and controls the module balancing in accordance with the determined energy transfer direction.

[0008] The central potential range includes a central potential located in the middle of the multiple potential magnitudes of the multiple battery cells and a potential that falls within a predetermined range above and below the central potential, the lower potential range includes a minimum potential among the multiple potential magnitudes of the multiple battery cells and a potential that falls within a predetermined range above and below the minimum potential, and the upper potential range includes a maximum potential among the multiple potential magnitudes of the multiple battery cells and a potential that falls within a predetermined range above and below the maximum potential.

[0009] The first module may include a plurality of the central cells corresponding to an integer multiple of an even number.

[0010] The charge equalization circuit may include a first equalization circuit including a central balancing switch, a first upper inductor connected between the positive electrode of the first module and one end of the central balancing switch, a first lower inductor connected between the negative electrode of the first module and the other end of the central balancing switch, first and second central diodes connected in series between a first node and a second node, and a balancing path connecting centers of a plurality of central cells included in the first module to centers of the first and second central diodes, wherein the first node may be located between the first upper inductor and one end of the central balancing switch, and the second node may be located between the first lower inductor and the other end of the central balancing switch.

[0011] The charge equalization circuit may include a second equalization circuit including a lower balancing switch, a second lower inductor connected between the positive electrode of the second module and one end of the lower balancing switch, and a lower diode connected between both ends of the lower balancing switch.

[0012] The charge equalization circuit may include a third equalization circuit including an upper balancing switch, a second upper inductor connected between the negative electrode of the third module and the other end of the upper balancing switch, and an upper diode connected between both ends of the upper balancing switch.

[0013] The control unit may turn on the central balancing switch when a module voltage of the first module is higher than each of the module voltages of the second module and the third module, and then turn off the central balancing switch after a predetermined time has elapsed.

[0014] When the module voltages of the second module and the third module are higher than the module voltage of the first module, the control unit may turn on the lower balancing switch and the upper balancing switch, and then turn off the lower balancing switch and the upper balancing switch after a predetermined time has elapsed.

[0015] A module balancing method according to another aspect of the present invention is a method for performing module balancing among a plurality of battery modules, the method including the steps of monitoring cell voltages of a plurality of battery cells connected in series to determine respective module voltages of a first module including a plurality of center cells among the plurality of series-connected battery cells, the center cells having a potential belonging to a center potential range, a second module including at least one lower cell having a potential belonging to a lower potential range, and a third module including at least one upper cell having a potential belonging to an upper potential range; comparing the module voltage of the first module with the module voltages of the second module and the third module to determine an energy transfer direction; and performing the module balancing among the first module, the second module, and the third module so that energy is transferred in the determined energy transfer direction.

[0016] The step of determining the energy transfer direction may include a step of determining whether a module voltage of the first module is greater than each of the module voltages of the second module and the third module, and, if the determination result shows that the module voltage of the first module is not greater than each of the module voltages of the second module and the third module, a step of determining whether each of the module voltages of the second module and the third module is greater than the module voltage of the first module.

[0017] The step of performing module balancing may include a step of performing module balancing such that energy is transferred from the first module to the second module and the third module when the module voltage of the first module is greater than the module voltages of the second module and the third module, and a step of performing module balancing such that energy is transferred from the second module and the third module to the first module when the module voltages of the second module and the third module are greater than the module voltage of the first module. [Effects of the Invention]

[0018] The embodiments of the present invention have the advantage that the number of components in the charge equalization circuit can be reduced, thereby saving costs, and the space occupied by the charge equalization circuit in the BMS can be reduced.

[0019] The embodiment of the present invention can extend the life of the entire battery by slowing down the degradation rate of the battery cell located in the center, which has a higher degree of degradation, among a plurality of battery cells connected in series.

[0020] Embodiments of the present invention can perform active balancing to increase the energy efficiency of the battery. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a block diagram illustrating a battery system according to an embodiment. [Figure 2] 2 is a detailed exemplary diagram of the battery and charge equalization circuit of FIG. 1. FIG. [Figure 3] 2 is a detailed exemplary diagram of the battery and charge equalization circuit of FIG. 1. FIG. [Figure 4] 2 is a detailed exemplary diagram of the battery and charge equalization circuit of FIG. 1. FIG. [Figure 5] 2 is a detailed exemplary diagram of the battery and charge equalization circuit of FIG. 1. FIG. [Figure 6] 2 is a detailed exemplary diagram of the battery and charge equalization circuit of FIG. 1. FIG. [Figure 7] 10 is an exemplary diagram of a charge equalization circuit that transfers energy from a central module to an outer shell module. FIG. [Figure 8] 10 is an exemplary diagram of a charge equalization circuit that transfers energy from a central module to an outer shell module. FIG. [Figure 9] 9 is an example of a waveform diagram of current flowing through the central module and the outer module in FIGS. 7 and 8. FIG. [Figure 10] 9 is another example of the waveform diagram of the current flowing through the central module and the outer module in FIGS. 7 and 8. FIG. [Figure 11] 10 is an exemplary diagram of a charge equalization circuit that transfers energy from an outer module to a central module. FIG. [Figure 12] 10 is an exemplary diagram of a charge equalization circuit that transfers energy from an outer module to a central module. FIG. [Figure 13] 13 is an example of a waveform diagram of current flowing through the central module and the outer module in FIGS. 11 and 12. FIG. [Figure 14] 1 is a flowchart illustrating a module balancing method according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, the embodiments disclosed herein will be described in detail with reference to the accompanying drawings. Identical or similar components will be assigned identical or similar drawing numbers, and redundant descriptions thereof will be omitted. The suffixes "module" and / or "section" used in the following description for components are assigned or used interchangeably solely for ease of description and do not have any distinct meanings or functions. Furthermore, when describing the embodiments disclosed herein, if a detailed description of related publicly known technology is deemed to obscure the gist of the embodiments disclosed herein, such a detailed description will be omitted. Furthermore, the accompanying drawings are intended to facilitate understanding of the embodiments disclosed herein, and should not be construed as limiting the technical concepts disclosed herein, but should be understood to include all modifications, equivalents, or alternatives within the concept and technical scope of the present invention.

[0023] Terms including ordinal numbers such as first, second, etc. may be used to describe various components, but the components are not limited by the terms. The terms are used only to distinguish one component from another.

[0024] When a component is described as being "coupled" or "connected" to another component, it should be understood that the component may be directly coupled or connected to the other component, but that there may be another component in between. On the other hand, when a component is described as being "directly coupled" or "directly connected" to another component, it should be understood that there is no other component in between.

[0025] In this application, the use of terms such as "comprise" or "have" is intended to specify the presence of a feature, numeral, step, operation, component, part, or combination thereof described in the specification, but is not to be understood as precluding the possible presence or addition of one or more other features, numerals, steps, operations, components, parts, or combinations thereof.

[0026] FIG. 1 is a block diagram illustrating a battery system according to an embodiment, and FIGS. 2 to 6 are detailed diagrams illustrating the battery and charge equalization circuit of FIG.

[0027] Referring to FIG. 1, a battery system 1 includes a battery 10, a current sensor 20, a relay 30, and a battery management system (BMS) 40.

[0028] 1, a battery 10 is connected between two output terminals (OUT1, OUT2) of a battery system 1, a relay 30 is connected between the positive terminal of the battery system 1 and the first output terminal (OUT1), and a current sensor 20 is connected between the negative terminal of the battery system 1 and the second output terminal (OUT2). The connection relationship between the components shown in FIG. 1 is an example, and the present invention is not limited thereto.

[0029] Battery 10 may include a plurality of battery cells (Cell1-Celln) electrically connected in series. In some embodiments, the battery cells may be rechargeable secondary batteries. In FIG. 1, battery 10 is illustrated as including six battery cells (Cell1-Cell6) connected in series, but is not limited thereto, and battery 10 may include any number of battery cells. Also, in FIG. 1, among the six battery cells (Cell1-Cell6), the first battery cell (Cell1) has the lowest potential, the sixth battery cell (Cell6) has the highest potential, and the potentials of the second battery cell (Cell2) through the fifth battery cell (Cell5) may gradually increase in order.

[0030] According to an embodiment, a plurality of battery cells (Cell1-Celln) connected in series can be grouped into a first module including a plurality of center cells located in a central potential range according to a predetermined criterion, a second module including at least one lower cell located in a lower potential range, and a third module including at least one upper cell located in an upper potential range.

[0031] The central potential range may include a central potential and a potential within a predetermined range above and below the central potential when the potentials of the plurality of battery cells (Cell1-Celln) are arranged in order of magnitude. The lower potential range may include a minimum potential and a potential within a predetermined range above and below the minimum potential when the potentials of the plurality of battery cells (Cell1-Celln) are arranged in order of magnitude. The upper potential range may include a maximum potential and a potential within a predetermined range above and below the maximum potential when the potentials of the plurality of battery cells (Cell1-Celln) are arranged in order of magnitude.

[0032] 2, the battery 10 includes six battery cells (Cell 1-Cell 6) connected in series, with the first module including two battery cells, and the second and third modules including one battery cell each.

[0033] For example, referring to FIG. 2 , the potentials of the third battery cell (Cell3) and the fourth battery cell (Cell4) belong to the center potential, so the third battery cell (Cell3) and the fourth battery cell (Cell4) may correspond to the center cells. The potential of the first battery cell (Cell1) belongs to the lower potential, so the first battery cell (Cell1) may correspond to the lower cell. The potential of the sixth battery cell (Cell6) belongs to the upper potential, so the sixth battery cell (Cell6) may correspond to the lower cell. Thus, the first module may include the third battery cell (Cell3) and the fourth battery cell (Cell4) corresponding to the center cells. The second module may include the first battery cell (Cell1) corresponding to the lower cell. The third module may include the sixth battery cell (Cell6) corresponding to the upper cell.

[0034] 3, the battery 10 includes eight battery cells (Cell 1-Cell 8) connected in series, with the first module including two battery cells, and the second and third modules each including one battery cell.

[0035] Referring to FIG. 3 , the potentials of the fourth battery cell (Cell4) and the fifth battery cell (Cell5) belong to the center potential, so the fourth battery cell (Cell4) and the fifth battery cell (Cell5) may correspond to the center cells. The potential of the first battery cell (Cell1) belongs to the lower potential, so the first battery cell (Cell1) may correspond to the lower cell. The potential of the eighth battery cell (Cell8) belongs to the upper potential, so the eighth battery cell (Cell8) may correspond to the upper cell. Thus, the first module may include the fourth battery cell (Cell4) and the fifth battery cell (Cell5) corresponding to the center cells. The second module may include the first battery cell (Cell1) corresponding to the lower cell. The third module may include the eighth battery cell (Cell8) corresponding to the upper cell.

[0036] 4, the battery 10 includes eight battery cells (Cell 1-Cell 8) connected in series, with the first module including four battery cells, and the second and third modules each including one battery cell.

[0037] Referring to FIG. 4, the potentials of the fourth battery cell (Cell4) and the fifth battery cell (Cell5) belong to the central potential, so the fourth battery cell (Cell4) and the fifth battery cell (Cell5) may correspond to the central cells. The potential of the first battery cell (Cell1) belongs to the lower potential, so the first battery cell (Cell1) may correspond to the lower cell. The potential of the eighth battery cell (Cell8) belongs to the upper potential, so the eighth battery cell (Cell8) may correspond to the upper cell. In addition, the first module may include the fourth battery cell (Cell4) and the fifth battery cell (Cell5) located at the central potential. In addition, since the first module includes a total of four central cells, it may further include the third battery cell (Cell3) and the sixth battery cell (Cell6) located adjacent to the central potential. That is, the first module may include the third, fourth, fifth, and sixth battery cells (Cell3, Cell4, Cell5, and Cell6) corresponding to the central cells. The second module may include a first battery cell (Cell1) corresponding to a lower cell, and the third module may include an eighth battery cell (Cell8) corresponding to an upper cell.

[0038] 5, the battery 10 includes eight battery cells (Cell1-Cell8) connected in series, and the first, second, and third modules each include two battery cells.

[0039] Referring to FIG. 5, the potentials of the fourth battery cell (Cell4) and the fifth battery cell (Cell5) belong to the center potential, so the fourth battery cell (Cell4) and the fifth battery cell (Cell5) may correspond to the center cells. The potential of the first battery cell (Cell1) belongs to the lower potential, so the first battery cell (Cell1) may correspond to the lower cell. The potential of the eighth battery cell (Cell8) belongs to the upper potential, so the eighth battery cell (Cell8) may correspond to the upper cell. Thus, the first module may include the fourth battery cell (Cell4) and the fifth battery cell (Cell5) corresponding to the center cells. The second module may include the first battery cell (Cell1) located at the lower potential. Furthermore, since the second module includes two battery cells, it may further include a second battery cell (Cell2) located adjacent to the lower potential. That is, the second module may include the first battery cell (Cell1) and the second battery cell (Cell2). The third module may include an eighth battery cell (Cell 8) located at a higher potential. In addition, since the third module includes two battery cells, it may further include a seventh battery cell (Cell 7) located adjacent to the higher potential. That is, the third module may include the seventh battery cell (Cell 7) and the eighth battery cell (Cell 8).

[0040] 6, a battery 10 includes eight battery cells (Cell 1-Cell 8) connected in series, with the first and second modules each including two battery cells, and the third module including one battery cell.

[0041] Referring to FIG. 6, the potentials of the fourth battery cell (Cell4) and the fifth battery cell (Cell5) belong to the center potential, so the fourth battery cell (Cell4) and the fifth battery cell (Cell5) may correspond to the center cells. The potential of the first battery cell (Cell1) belongs to the lower potential, so the first battery cell (Cell1) may correspond to the lower cell. The potential of the eighth battery cell (Cell8) belongs to the upper potential, so the eighth battery cell (Cell8) may correspond to the upper cell. Thus, the first module may include the fourth battery cell (Cell4) and the fifth battery cell (Cell5) corresponding to the center cells. The second module may include the first battery cell (Cell1) located at the lower potential. Furthermore, since the second module includes two battery cells, it may further include a second battery cell (Cell2) located adjacent to the lower potential. That is, the second module may include the first battery cell (Cell1) and the second battery cell (Cell2). The third module may include an eighth battery cell (Cell8) corresponding to the upper cell.

[0042] 2 to 6, the first module may include a plurality of center cells corresponding to an integer multiple of an even number, the second module may include at least one sub-cell, and the third module may include at least one sub-cell.

[0043] The current sensor 20 is connected in series to a current path between the battery 10 and an external device. The current sensor 20 can measure the battery current, i.e., the charging current and discharging current, flowing through the battery 10 and transmit the measurement result to the BMS 40.

[0044] The relay 30 controls the electrical connection between the battery system 1 and the external device. When the relay 30 is turned on, the battery system 1 and the external device are electrically connected to perform charging or discharging, and when the relay 30 is turned off, the battery system 1 and the external device are electrically separated. In this case, the external device is a charger in a charging cycle that supplies power to the battery 10 to charge it, and is a load in a discharging cycle that the battery 10 discharges power to the external device.

[0045] The BMS 40 includes a charge equalization circuit 41 , a monitoring IC 43 , and a control unit 45 .

[0046] The charge equalization circuit 41 can perform module balancing among the first, second, and third modules. Hereinafter, referring to FIG. 2, the first module (M1) includes a third battery cell (Cell3) and a fourth battery cell (Cell4), the second module (M2) includes a first battery cell (Cell1), and the third module (M3) includes a sixth battery cell (Cell6). However, this is not a limitation, and the following description can be similarly applied to various embodiments such as those shown in FIGS. 3 to 6.

[0047] Referring to Figures 1 and 2, the charge equalization circuit 41 may include multiple balancing switches (SW_mid, SW_bott, SW_top), multiple inductors (TR_top1, TR_bott1, TR_top2, TR_bott2), and multiple diodes (D_mid1, D_mid2, D_bott, D_top).

[0048] The multiple inductors (TR_top1, TR_bott1, TR_top2, TR_bott2) can configure an upper transformer and a lower transformer. In FIG. 2, the upper transformer can include a first upper inductor (TR_top1) and a second upper inductor (TR_top2), and the lower transformer can include a first lower inductor (TR_bott1) and a second lower inductor (TR_bott2).

[0049] Each of the multiple balancing switches (SW_mid, SW_bott, SW_top) performs a switching operation in response to a corresponding one of multiple switching signals (SC[1]-SC[3]) supplied from the monitoring IC 43. For each of the first module (M1), second module (M2), and third module (M3), the corresponding balancing switch (SW_i) is connected between the positive and negative poles of the corresponding module (Mi).

[0050] In each of the balancing switches (SW_mid, SW_bott, SW_top), the balancing switch (SW_i) may be configured as an electronic relay including a semiconductor switching element. The semiconductor switching element may be, but is not limited to, a metal-oxide field effect transistor (MOSFET). For example, the balancing switch (SW_i) may be turned on by an on-level gate voltage and turned off by an off-level gate voltage.

[0051] According to an embodiment, the charge equalization circuit 41 may include a first equalization circuit 411 , a second equalization circuit 412 , and a third equalization circuit 413 .

[0052] The first equalization circuit 411 may include a central balancing switch (SW_mid), a first upper inductor (TR_top1) connected between the positive terminal of the first module (M1) and one end of the central balancing switch (SW_mid), a first lower inductor (TR_bott1) connected between the negative terminal of the first module (M1) and the other end of the central balancing switch (SW_mid), a first central diode (D_mid1) and a second central diode (D_mid2) connected in series between a first node (N1) and a second node (N2), and a balancing path (BL) connecting the centers of multiple central cells (Cell3, Cell4) included in the first module (M1) to the centers of the first central diode (D_mid1) and the second central diode (D_mid2). At this time, the first node (N1) is located between the first upper inductor (TR_top1) and one end of the central balancing switch (SW_mid), and the second node (N2) is located between the first lower inductor (TR_bott1) and the other end of the central balancing switch (SW_mid).

[0053] The second equalization circuit 412 may include a lower balancing switch (SW_bott), a second lower inductor (TR_bott2) connected between the positive terminal of the second module (M2) and one end of the lower balancing switch (SW_bott), and a lower diode (D_top) connected between both ends of the lower balancing switch (SW_bott). At this time, one end of the lower diode (D_top) is connected between the second lower inductor (TR_bott2) and one end of the lower balancing switch (SW_bott), and the other end of the lower diode (D_top) is connected between the negative terminal of the second module (M2) and the other end of the lower balancing switch (SW_bott).

[0054] The third equalization circuit 413 may include an upper balancing switch (SW_top), a second upper inductor (TR_top2) connected between the negative terminal of the third module (M3) and the other terminal of the upper balancing switch (SW_top), and an upper diode (D_top) connected between both ends of the upper balancing switch (SW_top). At this time, one end of the upper diode (D_top) is connected between the positive terminal of the third module (M3) and one end of the upper balancing switch (SW_top), and the other end of the upper diode (D_top) is connected between the second upper inductor (TR_top2) and the other terminal of the upper balancing switch (SW_top).

[0055] The monitoring IC 43 is electrically connected to the positive and negative electrodes of each of the battery cells (Cell1-Cell6) and measures the cell voltage of each of the battery cells (Cell1-Celln). The battery current value measured by the current sensor 20 can be transmitted to the monitoring IC 43. The monitoring IC 43 transmits information about the measured cell voltage and battery current to the control unit 45.

[0056] The monitoring IC 43 can transmit multiple switching signals (SC[1]-SC[3]) to the multiple balancing switches (SW_mid, SW_bott, SW_top) under the control of the control unit 45. Then, each of the multiple balancing switches (SW_mid, SW_bott, SW_top) performs a switching operation according to a corresponding one of the multiple switching signals (SC[1]-SC[3]) supplied from the monitoring IC 43. However, this is not limited thereto, and the control unit 45 can transmit the multiple switching signals (SC[1]-SC[3]) to the multiple balancing switches (SW_mid, SW_bott, SW_top) to directly control the multiple balancing switches (SW_mid, SW_bott, SW_top). For convenience of explanation, the following description will be given assuming that the control unit 45 directly controls the multiple balancing switches (SW_mid, SW_bott, SW_top). A specific method of controlling the multiple balancing switches (SW_mid, SW_bott, SW_top) will be described below with reference to FIGS. 7 to 13.

[0057] The control unit 45 determines the energy transfer direction based on the module voltages of the first module (M1), the second module (M2), and the third module (M3), and controls the switching of the balancing switches (SW_mid, SW_bott, and SW_top) based on the determined energy transfer direction, thereby performing module balancing according to the embodiment.

[0058] The control unit 45 can determine the module voltages of the first module (M1), the second module (M2), and the third module (M3) based on the cell voltages transmitted from the monitoring IC 43. For example, referring to FIG. 2, the control unit 45 can determine the module voltage of the first module (M1) by summing the cell voltages of the third battery cell (Cell3) and the fourth battery cell (Cell4) connected in series. The control unit 45 can also determine the cell voltage of the first battery cell (Cell1) as the module voltage of the second module (M2) and the cell voltage of the sixth battery cell (Cell6) as the module voltage of the third module (M3).

[0059] According to the embodiment, the control unit 45 may determine the energy transmission direction so that energy is transmitted from a module with a higher module voltage to a module with a lower module voltage. For example, if the module voltage of the first module M1 is higher than the module voltages of the second module M2 and the third module M3, the control unit 45 may determine the energy transmission direction so that energy is transmitted from the first module M1 to the second module M2 and the third module M3, i.e., from the center to the outer casing of the battery 10. As another example, if the module voltages of the second module M2 and the third module M3 are higher than the module voltage of the module M1, the control unit 45 may determine the energy transmission direction so that energy is transmitted from the second module M2 and the third module M3 to the first module M1, i.e., from the outer casing to the center of the battery 10.

[0060] A specific method for performing module balancing will be described in detail below with reference to Figures 7 to 13. Figures 7 to 13 will be described based on the circuit diagram shown in Figure 2, but the present invention is not limited thereto, and the module balancing method described below can be similarly applied to various circuit diagrams such as those shown in Figures 3 to 6.

[0061] 7 and 8 are illustrative diagrams of a charge equalization circuit that transfers energy from the central module to the outer module, FIG. 9 is an illustrative diagram of a current waveform flowing through the central module and the outer module in FIGS. 7 and 8, and FIG. 10 is another illustrative diagram of a current waveform flowing through the central module and the outer module in FIGS. 7 and 8.

[0062] The center cell included in battery 10 may deteriorate to a greater extent due to a relatively higher temperature than the lower and upper cells located on the periphery. Therefore, during a charge cycle in which battery 10 is charged with power from an external device, the voltage of the first module (M1) including the center cell may reach the upper limit of charge voltage before the voltages of the second module (M2) including the lower cell and the third module (M3) including the upper cell. Also, during a discharge cycle in which battery 10 supplies power to an external device, the voltage of the first module (M1) including the center cell may reach the lower limit of discharge voltage before the voltages of the second module (M2) including the lower cell and the third module (M3) including the upper cell. Here, the upper limit of charge voltage is the maximum voltage at which charging can be performed without danger, and the lower limit of discharge voltage is the minimum voltage at which discharging can be performed without danger.

[0063] 7 and 8, for example, it is assumed that the module voltage of the first module (M1) is higher than the module voltages of the second module (M2) and the third module (M3). Then, the control unit 45 can determine the energy transmission direction from the central module to the outer module so that energy is transmitted from the first module (M1) with the higher module voltage to the second module (M2) and the third module (M3) with the lower module voltage.

[0064] 7, the control unit 45 turns on the central balancing switch SW_mid. Then, the first module M1, which includes the third battery cell Cell3 and the fourth battery cell Cell4, is discharged, and a central module current I_mid flows through the central balancing switch SW_mid. Energy is stored in the first upper inductor TR_top1 and the first lower inductor TR_bott1 by the central module current I_mid. That is, the third battery cell Cell3 and the fourth battery cell Cell4 are discharged.

[0065] 8, when a predetermined time has elapsed since the center balancing switch (SW_mid) was turned on, the control unit 45 turns off the center balancing switch (SW_mid). Then, due to the general electrical properties of a transformer, a lower module current (I_bott) can flow through the lower diode (D_top) as the energy stored in the first lower inductor (TR_bott1) is transferred to the second lower inductor (TR_bott2). Also, due to the general electrical properties of a transformer, an upper module current (I_top) can flow through the upper diode (D_top) as the energy stored in the first upper inductor (TR_top1) is transferred to the second upper inductor (TR_top2). That is, the first battery cell (Cell1) is charged by the lower module current (I_bott), and the sixth battery cell (Cell6) is charged by the upper module current (I_top). At this time, the principle of energy transmission between the upper and lower transformers is a well-known principle of transformers, and therefore a detailed description thereof will be omitted.

[0066] 7 and 8, when the central balancing switch (SW_mid) is turned on, the first module (M1) including the third battery cell (Cell3) and the fourth battery cell (Cell4) is discharged. When the central balancing switch (SW_mid) is turned off, the second module (M2) including the first battery cell (Cell1) and the third module (M3) including the sixth battery cell (Cell6) are charged. That is, energy is transferred from the first module (M1) to the second module (M2) and the third module (M3).

[0067] 9, when the central balancing switch (SW_mid) is turned on, the first module (M1) and the central balancing switch (SW_mid) are electrically connected, forming a current path within the first equalization circuit 411. At this time, the magnitude of the central module current (I_mid) may gradually increase due to the electrical interference of the first upper inductor (TR_top1) and the first lower inductor (TR_bott1). When the central balancing switch (SW_mid) is turned off, the electrical connection between the first module (M1) and the central balancing switch (SW_mid) is separated, and the magnitude of the central module current (I_mid) is zero. At this time, the magnitude of the lower module current (I_bott) and the upper module current (I_top) may momentarily increase and then gradually decrease due to the electrical interference of the second upper inductor (TR_top2) and the second lower inductor (TR_bott2). At this time, depending on the magnitude of the transferred energy, a time difference (△t1, △t2) may occur between the point at which the magnitude of the lower module current (I_bott) and the upper module current (I_top) is zero and the point at which the next central balancing switch (SW_mid) is turned on.

[0068] 10, the current waveforms of the lower module current (I_bott) and the upper module current (I_top) vary depending on various factors such as the magnitude of the central module current (I_mid), the on / off switching time of the central balancing switch (SW_mid), etc. The control unit 45 can control the on / off switching time of the central balancing switch (SW_mid) according to the voltage difference between the first module (M1), the second module (M2), and the third module (M3).

[0069] 11 and 12 are diagrams illustrating an example of a charge equalization circuit that transfers energy from the outer module to the central module, and FIG. 13 is a diagram illustrating an example of a current waveform diagram flowing through the central module and outer module in FIGS. 11 and 12.

[0070] 11 and 12, for example, it is assumed that the module voltages of the second module (M2) and the third module (M3) are higher than the module voltage of the first module (M1). Then, the control unit 45 can determine the energy transmission direction from the outer module to the central module so that energy is transmitted from the second module (M2) and the third module (M3) having higher module voltages to the first module (M1) having lower module voltage.

[0071] 11, the control unit 45 turns on the lower balancing switch (SW_bott) and the upper balancing switch (SW_top). Then, the second module (M2) including the first battery cell (Cell1) is discharged, and a lower module current (I_bott) flows through the lower balancing switch (SW_bott). Also, the third module (M3) including the sixth battery cell (Cell6) is discharged, and an upper module current (I_top) flows through the upper balancing switch (SW_top). Energy is stored in the second lower inductor (TR_bott2) and the second upper inductor (TR_top2) due to the lower module current (I_bott) and the upper module current (I_top). That is, the first battery cell (Cell1) and the sixth battery cell (Cell6) are discharged.

[0072] 12, when a predetermined time has elapsed after the lower balancing switch (SW_bott) and the upper balancing switch (SW_top) are turned on, the control unit 45 turns off the lower balancing switch (SW_bott) and the upper balancing switch (SW_top). Then, due to the general electrical properties of a transformer, a first central module current (I_mid1) can flow through the first central diode (D_mid1) while the energy stored in the second lower inductor (TR_bott2) is being transferred to the first lower inductor (TR_bott1). Also, due to the general electrical properties of a transformer, a second central module current (I_mid2) can flow through the second central diode (D_mid2) while the energy stored in the second upper inductor (TR_top2) is being transferred to the first upper inductor (TR_top1).

[0073] 2 and 12, the first center module current (I_mid1) and the second center module current (I_mid2) are opposite in direction in the balancing path (BL). For example, if the magnitudes of the first center module current (I_mid1) and the second center module current (I_mid2) are the same, the currents cancel each other out and no current flows through the balancing path (BL). As another example, if the magnitudes of the first center module current (I_mid1) and the second center module current (I_mid2) are the same, a small amount of current may flow through the balancing path (BL). While FIG. 12 shows both the first center module current (I_mid1) and the second center module current (I_mid2) in the balancing path (BL), this is not limiting and no current may flow through the balancing path (BL).

[0074] 12, it is assumed that the first central module current (I_mid1) and the second central module current (I_mid2) constitute the central module current (I_mid). That is, the third battery cell (Cell3) and the fourth battery cell (Cell4) can be charged by the central module current (I_mid). At this time, the principle of energy transfer between the upper and lower transformers is a well-known principle of transformers, so a detailed description will be omitted.

[0075] 11 and 12, when the lower balancing switch (SW_bott) and the upper balancing switch (SW_top) are turned on, the second module (M2) including the first battery cell (Cell1) and the third module (M3) including the sixth battery cell (Cell6) can be discharged. When the lower balancing switch (SW_bott) and the upper balancing switch (SW_top) are turned off, the first module (M1) including the third battery cell (Cell3) and the fourth battery cell (Cell4) can be charged. That is, energy can be transferred from the second module (M2) and the third module (M3) to the first module (M1).

[0076] 2, 11, and 13, when the lower balancing switch (SW_bott) is turned on, the second module (M2) and the lower balancing switch (SW_bott) are electrically connected, forming a current path in the second equalization circuit 412. When the upper balancing switch (SW_top) is turned on, the third module (M3) and the upper balancing switch (SW_top) are electrically connected, forming a current path in the third equalization circuit 413. At this time, the magnitudes of the lower module current (I_bott) and the upper module current (I_top) may show a gradually increasing pattern due to electrical interference between the second lower inductor (TR_bott2) and the second upper inductor (TR_top2). When the lower balancing switch (SW_bott) and upper balancing switch (SW_top) are turned off, the current path disappears in the second equalization circuit 412 and the third equalization circuit 413, and the magnitude of the lower module current (I_bott) and upper module current (I_top) becomes zero. At this time, the magnitude of the center module current (I_mid) may momentarily increase and then gradually decrease due to electrical interference from the first lower inductor (TR_bott1) and the first upper inductor (TR_top1). At this time, depending on the amount of transferred energy, a time difference (Δt3, Δt4) may occur between the time when the magnitude of the center module current (I_mid) becomes zero and the time when the next lower balancing switch (SW_bott) and upper balancing switch (SW_top) are turned on.

[0077] FIG. 14 is a flowchart illustrating a module balancing method according to an embodiment.

[0078] A module balancing method and a battery management system that implements the method will now be described in detail with reference to FIGS.

[0079] Referring to FIG. 14, the BMS 40 monitors the cell voltage of each of the plurality of battery cells (Cell1-Cell6) (S100).

[0080] The BMS 40 can determine the module voltages of the first module (M1), the second module (M2), and the third module (M3) based on the cell voltages of the battery cells (Cell1-Cell6). For example, referring to FIG. 2, the BMS 40 can determine the module voltage of the first module (M1) by summing the cell voltages of the third battery cell (Cell3) and the fourth battery cell (Cell4), which are connected in series. The BMS 40 can also determine the cell voltage of the first battery cell (Cell1) as the module voltage of the second module (M2) and the cell voltage of the sixth battery cell (Cell6) as the module voltage of the third module (M3). Hereinafter, the first module (M1) can correspond to the central module, and the second module (M2) and the third module (M3) can correspond to the outer modules.

[0081] Next, the BMS 40 compares the voltage of the central module with the voltage of the outer module to determine the direction of energy transfer (S200).

[0082] In step S200, the BMS 40 determines whether the voltage of the central module is greater than the voltage of the outer module (S210).

[0083] For example, referring to Figure 7, if the module voltage of the first module (M1) is greater than the module voltages of the second module (M2) and the third module (M3), the BMS 40 can determine the energy transfer direction from the central module to the outer module so that energy is transferred from the first module (M1) with the greater module voltage to the second module (M2) and the third module (M3) with the smaller module voltage.

[0084] In step S200, if the voltage of the central module is lower than the voltage of the outer module (S210, NO), the BMS 40 determines whether the voltage of the outer module is higher than the voltage of the central module (S220).

[0085] For example, referring to Figure 12, if the module voltages of the second module (M2) and the third module (M3) are each greater than the module voltage of the first module (M1), the BMS 40 can determine the energy transfer direction from the outer module to the central module so that energy is transferred from the second module (M2) and the third module (M3) with the greater module voltage to the first module (M1) with the smaller module voltage.

[0086] In step S200, if the voltage of the central module and the voltage of the outer module are equal in magnitude (S220, NO), the BMS 40 does not perform module balancing.

[0087] Next, the BMS 40 performs module balancing so that energy is transmitted in the determined energy transmission direction (S300).

[0088] In step S300, if the voltage of the central module is greater than the voltage of the outer module (S210, Yes), the BMS 40 performs module balancing so that energy is transferred from the central module to the outer module (S310).

[0089] For example, referring to FIG. 7, the BMS 40 controls the central balancing switch (SW_mid) to turn on. Then, the first module (M1), which is the central module, is discharged, and a central module current (I_mid) can flow through the central balancing switch (SW_mid). The central module current (I_mid) can store energy in the first upper inductor (TR_top1) and the first lower inductor (TR_bott1). That is, the first module (M1), which is the central module, can be discharged.

[0090] 8, when a predetermined time has elapsed since the central balancing switch (SW_mid) was turned on, the BMS 40 turns off the central balancing switch (SW_mid). Then, due to the general electrical properties of a transformer, a lower module current (I_bott) can flow through the lower diode (D_top) as the energy stored in the first lower inductor (TR_bott1) is transferred to the second lower inductor (TR_bott2). Also, due to the general electrical properties of a transformer, an upper module current (I_top) can flow through the upper diode (D_top) as the energy stored in the first upper inductor (TR_top1) is transferred to the second upper inductor (TR_top2). That is, the first battery cell (Cell1) can be charged by the lower module current (I_bott), and the sixth battery cell (Cell6) can be charged by the upper module current (I_top). At this time, the principle of energy transmission between the upper and lower transformers is a well-known principle of transformers, and therefore a detailed description thereof will be omitted.

[0091] In summary, the BMS 40 turns on the central balancing switch (SW_mid) and then turns off the central balancing switch (SW_mid) after a predetermined time has elapsed. Energy from the first module (M1), which is the central module, is then transferred to the second module (M2) and the third module (M3), which are the outer modules. In some embodiments, the BMS 40 may repeat the turn-on / turn-off switching control of the central balancing switch (SW_mid) until the module voltages of the first module (M1), the second module (M2), and the third module (M3) fall within a predetermined error range.

[0092] In step S300, if the voltage of the outer module is higher than that of the central module (S220, Yes), the BMS 40 performs module balancing so that energy is transferred from the outer module to the central module (S320).

[0093] For example, referring to FIG. 11, the BMS 40 turns on the lower balancing switch (SW_bott) and the upper balancing switch (SW_top). Then, the second module (M2), which is an outer module, is discharged, and a lower module current (I_bott) can flow through the lower balancing switch (SW_bott). Also, the third module (M3), which is another outer module, is discharged, and an upper module current (I_top) can flow through the upper balancing switch (SW_top). Energy can be stored in the second lower inductor (TR_bott2) and the second upper inductor (TR_top2) due to the lower module current (I_bott) and the upper module current (I_top). That is, the second module (M2) and the third module (M3) can be discharged.

[0094] 12, when a predetermined time has elapsed after the lower balancing switch (SW_bott) and the upper balancing switch (SW_top) are turned on, the BMS 40 turns off the lower balancing switch (SW_bott) and the upper balancing switch (SW_top). Then, due to the general electrical properties of a transformer, a first central module current (I_mid1) can flow through the first central diode (D_mid1) while the energy stored in the second lower inductor (TR_bott2) is transferred to the first lower inductor (TR_bott1). Also, due to the general electrical properties of a transformer, a second central module current (I_mid2) can flow through the second central diode (D_mid2) while the energy stored in the second upper inductor (TR_top2) is transferred to the first upper inductor (TR_top1).

[0095] In summary, the BMS 40 turns on the lower balancing switch (SW_bott) and the upper balancing switch (SW_top) and then turns off the lower balancing switch (SW_bott) and the upper balancing switch (SW_top) after a predetermined time has elapsed. Energy from the second module (M2) and the third module (M3), which are outer modules, is then transferred to the first module (M1), which is the central module. According to an embodiment, the BMS 40 can repeat the turn-on / turn-off switching control of the lower balancing switch (SW_bott) and the upper balancing switch (SW_top) until the module voltages of the first module (M1), the second module (M2), and the third module (M3) fall within a predetermined error range.

[0096] Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited to these examples, and various modifications and improvements made by those skilled in the art to which the present invention pertains also fall within the scope of the present invention.

Claims

1. a charge equalization circuit that performs module balancing among a first module including a plurality of center cells having a potential in a center potential range among a plurality of battery cells connected in series, a second module including at least one lower cell having a potential in a lower potential range, and a third module including at least one upper cell having a potential in an upper potential range; a control unit that calculates a module voltage of each of the first module, the second module, and the third module based on the cell voltages of each of the plurality of battery cells, determines an energy transfer direction based on the calculated module voltages, and controls the module balancing in accordance with the determined energy transfer direction.

2. The central potential range is a central potential located at a center among a plurality of potential magnitudes of the plurality of battery cells, and a potential within a predetermined range above and below the central potential; The lower potential range is a minimum potential among a plurality of potential magnitudes of the plurality of battery cells and a potential that falls within a predetermined range based on the minimum potential; The upper potential range is The battery management system according to claim 1 , wherein the magnitudes of the plurality of potentials of the plurality of battery cells include a maximum potential and a potential that falls within a predetermined range of magnitude based on the maximum potential.

3. The first module is The battery management system of claim 1 , comprising the plurality of center cells corresponding to integer multiples of even numbers.

4. The charge equalization circuit includes: a first equalization circuit including a central balancing switch, a first upper inductor connected between the positive electrode of the first module and one end of the central balancing switch, a first lower inductor connected between the negative electrode of the first module and the other end of the central balancing switch, a first central diode and a second central diode connected in series between a first node and a second node, and a balancing path connecting the centers of a plurality of central cells included in the first module to the centers of the first central diode and the second central diode; the first node is located between the first upper inductor and one end of the central balancing switch; The battery management system of claim 1 , wherein the second node is located between the first lower inductor and the other end of the central balancing switch.

5. The charge equalization circuit includes:

5. The battery management system of claim 4, further comprising a second equalization circuit including a lower balancing switch, a second lower inductor connected between the positive electrode of the second module and one end of the lower balancing switch, and a lower diode connected across the lower balancing switch.

6. The charge equalization circuit includes:

6. The battery management system of claim 5, further comprising a third equalization circuit including an upper balancing switch, a second upper inductor connected between the negative electrode of the third module and the other end of the upper balancing switch, and an upper diode connected across the upper balancing switch.

7. The control unit 5. The battery management system according to claim 4, wherein when the module voltage of the first module is greater than the module voltages of the second module and the third module, the central balancing switch is turned on and then turned off after a predetermined time has elapsed.

8. The control unit 7. The battery management system of claim 6, wherein when the module voltages of the second module and the third module are higher than the module voltage of the first module, the lower balancing switch and the upper balancing switch are turned on and then turned off after a predetermined time has elapsed.

9. A method for module balancing among a plurality of battery modules, comprising: Monitoring cell voltages of a plurality of battery cells connected in series, and determining module voltages of a first module including a plurality of center cells whose potentials belong to a center potential range, a second module including at least one lower cell whose potentials belong to a lower potential range, and a third module including at least one upper cell whose potentials belong to an upper potential range, among the plurality of battery cells connected in series; comparing a module voltage of the first module with a module voltage of each of the second and third modules to determine an energy transfer direction; performing the module balancing among the first module, the second module, and the third module so that energy is transferred in the determined energy transfer direction.

10. The step of determining a direction of energy transfer comprises: determining whether a module voltage of the first module is greater than a module voltage of each of the second module and the third module; 10. The module balancing method of claim 9, further comprising: if the result of the determination is that the module voltage of the first module is not greater than the module voltages of the second module and the third module, determining whether the module voltages of the second module and the third module are greater than the module voltage of the first module.

11. The step of performing module balancing includes: performing module balancing such that, when a module voltage of the first module is greater than the module voltages of the second module and the third module, energy is transferred from the first module to the second module and the third module; 11. The module balancing method of claim 10, further comprising: if the module voltages of the second module and the third module are greater than the module voltage of the first module, performing module balancing such that energy is transferred from the second module and the third module to the first module.

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