Module balancing method and battery management system using same

Abstract

Disclosed are a module balancing method and a battery management system, the system including: a charge balancing circuit, among a plurality of battery cells connected in series with each other, module balancing is performed between a first module comprising a plurality of central cells having a potential falling within a central potential range, a second module comprising at least one lower cell having a potential falling within a lower potential range, and a third module comprising at least one upper cell having a potential falling within a central potential range. And at least one upper cell has a potential falling within an upper potential range; and a control unit that calculates each module voltage of the first module, the second module, and the third module based on each cell voltage of the plurality of battery cells, determines an energy transfer direction based on the calculated module voltages, and controls module balancing based on the determined energy transfer direction.

Description

Technical Field

[0001] Cross - Reference to Related Applications

[0002] This application claims the priority and benefit of Korean Patent Application No. 10-2022-0184461, filed with the Korean Intellectual Property Office on December 26, 2022, and Korean Patent Application No. 10-2023-0190074, filed with the Korean Intellectual Property Office on December 22, 2023, the entire contents of which are incorporated herein by reference.

[0003] The present disclosure relates to a module balancing method and a battery management system. Background Art

[0004] Cell balancing may be a method of reducing the voltage difference between multiple cells that occurs during the charge / discharge voltage behavior of the multiple cells connected in series with each other. For example, among a first cell and a second cell, when the cell voltage of the first cell reaches a reference voltage (e.g., 4.2 V) during the charging process, the cell voltage of the second cell may reach 4.0. In this case, it is necessary to stop charging to prevent overcharging of the first cell. However, in this case, since the second cell is not fully charged, the overall charging capacity of the battery may be reduced. When multiple cells have different voltages as described above, cell balancing may be performed. A circuit (hereinafter referred to as a "cell balancing circuit") that can discharge multiple cells may be implemented in a battery management system (hereinafter referred to as a "BMS") to reduce the voltage difference between the multiple cells.

[0005] Cell balancing includes passive cell balancing and active cell balancing. Passive cell balancing is a method of selecting a cell having a higher voltage and dissipating the charging energy of the selected cell by using a discharge resistor. Active cell balancing is a method of transferring charging energy from a cell having a higher voltage to a cell having a lower voltage.

[0006] Meanwhile, since the discharge resistor loses energy as heat, passive cell balancing may have low efficiency. On the other hand, active cell balancing may have better energy efficiency than passive cell balancing. However, the cell balancing circuit for implementing active cell balancing may be very complex, occupy a large amount of space in the battery system, and require more components, resulting in a high cost burden. Summary of the Invention

[0007] Technical Problem

[0008] The present disclosure attempts to provide a method and a battery management system for performing active module balancing between battery modules by using a simple charging equalization circuit.

[0009] Technical solution

[0010] According to an embodiment, a battery management system includes: a charging equalization circuit that performs module balancing among a plurality of battery cells connected in series with each other, between a first module including a plurality of central cells, a second module including at least one lower cell, and a third module including at least one upper cell, wherein each of the plurality of central cells has a potential falling within a central potential range, at least one lower cell has a potential falling within a lower potential range, and at least one upper cell has a potential falling within an upper potential range; and a control unit that calculates a module voltage of each of the first module, the second module, and the third module based on a cell voltage of each of the plurality of battery cells, determines an energy transfer direction based on the calculated module voltages, and controls the module balancing based on the determined energy transfer direction.

[0011] The central potential range may include a central potential set at the center of a plurality of potential magnitudes of the plurality of battery cells and a potential falling within an upper range or a lower range of a predetermined magnitude from the central potential. The lower potential range may include a minimum potential among the plurality of potential magnitudes of the plurality of battery cells and a potential falling within a range of a predetermined magnitude from the minimum potential. And the upper potential range may include a maximum potential among the plurality of potential magnitudes of the plurality of battery cells and a potential falling within a range of a predetermined magnitude from the maximum potential.

[0012] The first module may include a plurality of central cells corresponding to an integer multiple of an even number.

[0013] The charging equalization circuit may include a first equalization circuit. The first equalization circuit includes a central balance switch, a first upper inductor connected between the positive electrode of the first module and one end of the central balance switch, a first lower inductor connected between the negative electrode of the first module and the other end of the central balance switch, a first central diode and a second central diode connected in series with each other between a first node and a second node, and a balance path connecting the center of the plurality of central cells included in the first module to the center of the first central diode and the second central diode. The first node may be set between the first upper inductor and one end of the central balance switch, and the second node may be set between the first lower inductor and the other end of the central balance switch.

[0014] The charging equalization circuit may include a second equalization circuit. The second equalization circuit includes a lower balance switch, a second lower inductor connected between the positive electrode of the second module and one end of the lower balance switch, and a lower diode connected between both ends of the lower balance switch.

[0015] The charge equalization circuit may include a third equalization circuit, and the third equalization circuit includes an upper balance switch, a second upper inductor connected between the negative electrode of the third module and the other end of the upper balance switch, and an upper diode connected between both ends of the upper balance switch.

[0016] When the module voltage of the first module is greater than the module voltages of each of the second module and the third module, the control unit may control the central balance switch to be turned off after a predetermined time after turning on the central balance switch.

[0017] When the module voltage of each of the second module and the third module is greater than the module voltage of the first module, the control unit may control the lower balance switch and the upper balance switch to be turned off after a predetermined time after turning on the lower balance switch and the upper balance switch.

[0018] According to another embodiment, a module balancing method, which is a method for performing module balancing among multiple battery modules, includes: monitoring the cell voltages of multiple battery cells connected in series with each other to determine the module voltages of each of a first module including multiple central cells, a second module including at least one lower cell, and a third module including at least one upper cell among the multiple battery cells connected in series with each other, each of the multiple central cells having a potential falling within a central potential range, at least one lower cell having a potential falling within a lower potential range, and at least one upper cell having a potential falling within an upper potential range; determining the energy transfer direction by comparing the module voltage of the first module with the module voltages of each of the second module and the third module; and performing module balancing among the first module, the second module, and the third module so that energy is transferred in the determined energy transfer direction.

[0019] Determining the energy transfer direction may include: determining whether the module voltage of the first module is greater than the module voltages of each of the second module and the third module, and as a result of the determination, when the module voltage of the first module is not greater than the module voltages of each of the second module and the third module, determining whether the module voltage of each of the second module and the third module is greater than the module voltage of the first module.

[0020] Performing module balancing may include: when the module voltage of the first module is greater than the module voltages of each of the second module and the third module, performing module balancing so that energy is transferred from the first module to the second module and the third module, and when the module voltage of each of the second module and the third module is greater than the module voltage of the first module, performing module balancing so that energy is transferred from the second module and the third module to the first module.

[0021] Beneficial effects

[0022] The present disclosure can have fewer components in the charge equalization circuit to thus reduce costs and have less space occupied by the charge equalization circuit in the BMS.

[0023] The present disclosure can extend the life of the entire battery by slowing down the degradation rate of the battery cell that is set in the center and has the maximum degradation level among a plurality of battery cells connected in series with each other.

[0024] The present disclosure can ensure higher energy efficiency of the battery by performing active balancing. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a block diagram showing a battery system according to an embodiment.

[0026] Figures 2 to 6 are example views each showing in detail Figure 1 the battery and the charge equalization circuit.

[0027] Figure 7 and Figure 8 are example views each showing a charge equalization circuit that transfers energy from a central module to an external module.

[0028] Figure 9 is a view showing the current flowing through Figure 7 and Figure 8 in the central module and the external module.

[0029] Figure 10 is a view showing the current flowing through Figure 7 and Figure 8 in the central module and the external module.

[0030] Figure 11 and Figure 12 are example views each showing a charge equalization circuit that transfers energy from an external module to a central module.

[0031] Figure 13 is a view showing the current flowing through Figure 11 and Figure 12 in the central module and the external module.

[0032] Figure 14 is a flowchart showing a module balancing method according to another embodiment. DETAILED DESCRIPTION

[0033] In the following, embodiments disclosed in the specification will be described in detail with reference to the accompanying drawings, where the same or similar components are denoted by the same or similar reference numerals, and overlapping descriptions thereof are omitted. In the following description, the terms "module" and / or "unit" used for components are only for making the specification easy to understand. Therefore, these terms do not have meanings or functions that distinguish them from each other. In addition, when describing the embodiments disclosed in the specification, detailed descriptions of known technologies related to the present disclosure may obscure the key points, and thus the detailed descriptions will be omitted. In addition, it will be understood that the accompanying drawings are provided only to allow the embodiments of the present disclosure to be easily understood, and the spirit of the present disclosure is not limited by the drawings, and includes all modifications, equivalents, and substitutions included in the spirit and scope of the present disclosure.

[0034] Terms including ordinal numbers such as "first", "second", etc. may be used to describe various components. However, these components are not limited by these terms. These terms are only used to distinguish one component from another.

[0035] It should be understood that when a component is referred to as being "connected to" or "coupled to" another component, one component may be directly connected or coupled to another component, or may be connected or coupled to another component while having a third component inserted therebetween. On the other hand, it will be understood that if a component is referred to as being "directly connected to" or "directly coupled to" another component, one component may be connected to or coupled to another component without a third component inserted therebetween.

[0036] It should be understood that the terms "comprising", "having", etc. used in the present application specify the presence of features, numbers, steps, operations, components, parts, or combinations thereof mentioned in the specification, and do not exclude the presence or possible addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0037] Figure 1 is a block diagram showing a battery system according to an embodiment; and Figures 2 to 6 are respective exemplary views showing in detail Figure 1 the battery and the charge equalization circuit.

[0038] Referring to Figure 1 , the battery system 1 may include a battery 10, a current sensor 20, a relay 30, and a battery management system (hereinafter referred to as "BMS") 40.

[0039] As Figure 1 shown, the battery 10 may be connected between two output terminals OUT1 and OUT2 of the battery system 1, the relay 30 may be connected between the positive electrode of the battery system 1 and the first output terminal OUT1, and the current sensor 20 may be connected between the negative electrode of the battery system 1 and the second output terminal OUT2.Figure 1 The components and the connection relationships between the components shown are examples, and the present disclosure is not limited thereto.

[0040] The battery 10 may include a plurality of battery cells Cell1 to Celln that are electrically connected in series with each other. In some embodiments, the battery cells may be rechargeable secondary batteries. Figure 1 It is shown that the battery 10 includes six battery cells Cell1 to Cell6 that are connected in series with each other, and is not limited thereto, and the battery 10 may include various numbers of battery cells. In addition, among Figure 1 the six battery cells Cell1 to Cell6 shown, the first battery cell Cell1 may have the minimum electric potential, and the sixth battery cell Cell6 may have the maximum electric potential, and the second battery cell Cell2 to the fifth battery cell Cell5 may have gradually increasing electric potentials in sequence.

[0041] In some embodiments, a plurality of battery cells Cell1 to Celln that are connected in series with each other may be grouped into a first module, a second module, and a third module. The first module includes a plurality of central cells disposed within a central electric potential range based on a predetermined criterion, the second module includes at least one lower cell disposed within a lower electric potential range, and the third module includes at least one upper cell disposed within an upper electric potential range.

[0042] When the respective electric potentials of the plurality of battery cells Cell1 to Celln are listed in order of magnitude, the central electric potential range may include the central electric potential and electric potentials that fall within an upper range or a lower range of a predetermined magnitude from the central electric potential. When the respective electric potentials of the plurality of battery cells Cell1 to Celln are listed in order of magnitude, the lower electric potential range may include the minimum electric potential and electric potentials that fall within a range of a predetermined magnitude from the minimum electric potential. When the respective electric potentials of the plurality of battery cells Cell1 to Celln are listed in order of magnitude, the upper electric potential range may include the maximum electric potential and electric potentials that fall within a range of a predetermined magnitude from the maximum electric potential.

[0043] In some embodiments, referring to Figure 2 , it is assumed that the battery 10 includes six battery cells Cell1 to Cell6 that are connected in series with each other. Additionally, it is assumed that the first module includes two battery cells, and each of the second module and the third module includes one battery cell.

[0044] For example, referring to Figure 2, the potential of each of the third battery cell Cell3 and the fourth battery cell Cell4 belongs to the central potential, and each of the third battery cell Cell3 and the fourth battery cell Cell4 can thus correspond to the central cell. The potential of the first battery cell Cell1 can belong to the lower potential, and the first battery cell Cell1 can thus correspond to the lower cell. The potential of the sixth battery cell Cell6 can belong to the upper potential, and the sixth battery cell Cell6 can thus correspond to the upper cell. That is to say, the first module can include the third battery cell Cell3 and the fourth battery cell Cell4 each corresponding to the central cell. The second module can include the first battery cell Cell1 corresponding to the lower cell. The third module can include the sixth battery cell Cell6 corresponding to the upper cell.

[0045] In another embodiment, referring to Figure 3 , it is assumed that the battery 10 includes eight battery cells Cell1 to Cell8 connected in series with each other. In addition, it is assumed that the first module includes two battery cells, and each of the second module and the third module includes one battery cell.

[0046] Referring to Figure 3 , the potential of each of the fourth battery cell Cell4 and the fifth battery cell Cell5 belongs to the central potential, and each of the fourth battery cell Cell4 and the fifth battery cell Cell5 can thus correspond to the central cell. The potential of the first battery cell Cell1 can belong to the lower potential, and the first battery cell Cell1 can thus correspond to the lower cell. The potential of the eighth battery cell Cell8 can belong to the upper potential, and the eighth battery cell Cell8 can thus correspond to the upper cell. That is to say, the first module can include the fourth battery cell Cell4 and the fifth battery cell Cell5 each corresponding to the central cell. The second module can include the first battery cell Cell1 corresponding to the lower cell. The third module can include the eighth battery cell Cell8 corresponding to the upper cell.

[0047] In yet another embodiment, referring to Figure 4 , it is assumed that the battery 10 includes eight battery cells Cell1 to Cell8 connected in series with each other. Additionally, it is assumed that the first module includes four battery cells, and each of the second module and the third module includes one battery cell.

[0048] Referring to Figure 4, the potential of each of the fourth battery cell Cell4 and the fifth battery cell Cell5 belongs to the central potential, and each of the fourth battery cell Cell4 and the fifth battery cell Cell5 can thus correspond to the central cell. The potential of the first battery cell Cell1 can belong to the lower potential, and the first battery cell Cell1 can thus correspond to the lower cell. The potential of the eighth battery cell Cell8 can belong to the upper potential, and the eighth battery cell Cell8 can thus correspond to the upper cell. That is to say, the first module can include the fourth battery cell Cell4 and the fifth battery cell Cell5, each of which belongs to the central potential. In addition, the first module can include a total of four central cells, and thus also includes the third battery cell Cell3 and the sixth battery cell Cell6, each of which is arranged adjacent to the central potential. That is to say, the first module can include the third battery cell Cell3, the fourth battery cell Cell4, the fifth battery cell Cell5, and the sixth battery cell Cell6, each of which corresponds to the central cell. The second module can include the first battery cell Cell1 corresponding to the lower cell. The third module can include the eighth battery cell Cell8 corresponding to the upper cell.

[0049] In addition, in yet another embodiment, referring to Figure 5 , it is assumed that the battery 10 includes eight battery cells Cell1 to Cell8 connected in series with each other. In addition, it is assumed that each of the first module, the second module, and the third module includes two battery cells.

[0050] Referring to Figure 5, the potential of each of the fourth battery cell Cell4 and the fifth battery cell Cell5 belongs to the central potential, and each of the fourth battery cell Cell4 and the fifth battery cell Cell5 can thus correspond to the central cell. The potential of the first battery cell Cell1 can belong to the lower potential, and the first battery cell Cell1 can thus correspond to the lower cell. The potential of the eighth battery cell Cell8 can belong to the upper potential, and the eighth battery cell Cell8 can thus correspond to the upper cell. That is to say, the first module can include the fourth battery cell Cell4 and the fifth battery cell Cell5 that respectively correspond to the central cell. The second module can include the first battery cell Cell1 belonging to the lower potential. Additionally, the second module can include two battery cells, and thus also includes the second battery cell Cell2 arranged adjacent to the lower potential. That is to say, the second module can include the first battery cell Cell1 and the second battery cell Cell2. The third module can include the eighth battery cell Cell8 belonging to the upper potential. Additionally, the third module can include two battery cells, and thus also includes the seventh battery cell Cell7 arranged adjacent to the upper potential. That is to say, the third module can include the seventh battery cell Cell7 and the eighth battery cell Cell8.

[0051] In another embodiment, referring to Figure 6 , it is assumed that the battery 10 includes eight battery cells Cell1 to Cell8 connected in series with each other. Additionally, it is assumed that each of the first module and the second module includes two battery cells, and the third module includes one battery cell.

[0052] Referring to Figure 6 , the potential of each of the fourth battery cell Cell4 and the fifth battery cell Cell5 belongs to the central potential, and each of the fourth battery cell Cell4 and the fifth battery cell Cell5 can thus correspond to the central cell. The potential of the first battery cell Cell1 can belong to the lower potential, and the first battery cell Cell1 can thus correspond to the lower cell. The potential of the eighth battery cell Cell8 can belong to the upper potential, and the eighth battery cell Cell8 can thus correspond to the upper cell. That is to say, the first module can include the fourth battery cell Cell4 and the fifth battery cell Cell5 that respectively correspond to the central cell. The second module can include the first battery cell Cell1 belonging to the lower potential. Additionally, the second module can include two battery cells, and thus also includes the second battery cell Cell2 arranged adjacent to the lower potential. That is to say, the second module can include the first battery cell Cell1 and the second battery cell Cell2. The third module can include the eighth battery cell Cell8 corresponding to the upper cell.

[0053] In some embodiments, referring to Figures 2 to 6 , the first module may include a plurality of central monomers corresponding to integer multiples of even numbers. The second module may include at least one lower monomer. The third module may include at least one upper monomer.

[0054] The current sensor 20 may be connected in series to the current path between the battery 10 and the external device. The current sensor 20 may measure the battery current flowing through the battery 10, i.e., the charging current or the discharging current, and transmit the measurement result to the BMS 40.

[0055] The relay 30 may control 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 may be electrically connected to each other to perform charging or discharging of the battery, and when the relay 30 is turned off, the battery system 1 and the external device may be electrically disconnected from each other. Here, the external device may be a charger in the charging cycle in which the battery 10 receives power and is thus charged, and may be a load in the discharging cycle in which the battery 10 discharges to the external device.

[0056] The BMS 40 may include a charge equalization circuit 41, a monitoring integrated circuit (IC) 43, and a control unit 45.

[0057] The charge equalization circuit 41 may perform module balancing among the first module, the second module, and the third module. Hereinafter, referring to Figure 2 , it is assumed that the first module M1 includes the third battery cell Cell3 and the fourth battery cell Cell4, the second module M2 includes the first battery cell Cell1, and the third module M3 includes the sixth battery cell Cell6 for description. However, the present disclosure is not limited thereto, and the content described below may be equivalently applied to various embodiments, such as the embodiments described with reference to Figures 3 to 6 .

[0058] Referring to Figure 1 and Figure 2 , the charge equalization circuit 41 may include a plurality of balancing switches SW_mid, SW_bott, and SW_top, a plurality of inductors TR_top1, TR_bott1, TR_top2, and TR_bott2, and a plurality of diodes D_mid1, D_mid2, D_bott, and D_top.

[0059] The plurality of inductors TR_top1, TR_bott1, TR_top2, and TR_bott2 may constitute an upper transformer and a lower transformer. As Figure 2As shown, the upper transformer may include a first upper inductor TR_top1 and a second upper inductor TR_top2, and the lower transformer may include a first lower inductor TR_bott1 and a second lower inductor TR_bott2.

[0060] Each of the plurality of balance switches SW_mid, SW_bott, and SW_top may perform a switching operation based on a corresponding switching signal among the plurality of switching signals SC[1] to SC[3] supplied from the monitoring IC 43. The balance switch SW_i corresponding to each of the first module M1, the second module M2, and the third module M3 may be connected between the positive electrode and the negative electrode of the corresponding module Mi.

[0061] The balance switch SW_i in each of the first module M1, the second module M2, and the third module M3 may be an electronic relay including a semiconductor switching element. The semiconductor switching element may use a metal oxide field effect transistor (MOSFET), and is not limited thereto. For example, the balance switch SW_i may be turned on by an on-level gate voltage and turned off by an off-level gate voltage.

[0062] In some embodiments, the charge equalization circuit 41 may include a first equalization circuit 411, a second equalization circuit 412, and a third equalization circuit 413.

[0063] The first equalization circuit 411 may include a central balance switch SW_mid, a first upper inductor TR_top1 connected between the positive electrode of the first module M1 and one end of the central balance switch SW_mid, a first lower inductor TR_bott1 connected between the negative electrode of the first module M1 and the other end of the central balance switch SW_mid, a first central diode D_mid1 and a second central diode D_mid2 connected in series with each other between the first node N1 and the second node N2, and a balance path BL connecting the center of the plurality of central monomers Cell3 and Cell4 included in the first module M1 to the center of the first central diode D_mid1 and the second central diode D_mid2. Here, the first node N1 may be provided between the first upper inductor TR_top1 and one end of the central balance switch SW_mid, and the second node N2 may be provided between the first lower inductor TR_bott1 and the other end of the central balance switch SW_mid.

[0064] The second balancing circuit 412 may include a lower balancing switch SW_bott, a second lower inductor TR_bott connected between the positive electrode of the second module M2 and one end of the lower balancing switch SW_bott, and a lower diode D_bott connected between both ends of the lower balancing switch SW_bott. Here, one end of the lower diode D_bott may be connected between the second lower inductor TR_bott and one end of the lower balancing switch SW_bott, and the other end of the lower diode D_bott may be connected between the negative electrode of the second module M2 and the other end of the lower balancing switch SW_bott.

[0065] The third balancing circuit 413 may include an upper balancing switch SW_top, a second upper inductor TR_top2 connected between the negative electrode of the third module M3 and the other end of the upper balancing switch SW_top, and an upper diode D_top connected between both ends of the upper balancing switch SW_top. Here, one end of the upper diode D_top may be connected between the positive electrode 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 may be connected between the second upper inductor TR_top2 and the other end of the upper balancing switch SW_top.

[0066] The monitoring IC 43 may be electrically connected to the positive and negative electrodes of each of the plurality of battery cells Cell1 to Cell6, and measure the cell voltage of each of the plurality of battery cells Cell1 to Cell6. The battery current value measured by the current sensor 20 may be transmitted to the monitoring IC 43. The monitoring IC 43 may transmit information about the measured cell voltage and battery current to the control unit 45.

[0067] The monitoring IC 43 may transmit a plurality of switch signals SC[1] to SC[3] to the plurality of balancing switches SW_mid, SW_bott, and SW_top under the control of the control unit 45. Then, each of the plurality of balancing switches SW_mid, SW_bott, and SW_top may perform a switching operation based on the corresponding switch signal among the plurality of switch signals SC[1] to SC[3] supplied from the monitoring IC 43. However, the present disclosure is not limited thereto, and the control unit 45 may directly control the plurality of balancing switches SW_mid, SW_bott, and SW_top by transmitting the plurality of switch signals SC[1] to SC[3] to the plurality of balancing switches SW_mid, SW_bott, and SW_top. Hereinafter, for ease of explanation, the specification describes that the control unit 45 directly controls the plurality of balancing switches SW_mid, SW_bott, and SW_top, and with reference to Figures 7 to 13Describes a specific method for controlling multiple balancing switches SW_mid, SW_bott, and SW_top.

[0068] The control unit 45 can determine the energy transfer direction based on the module voltage of each of the first module M1, the second module M2, and the third module M3, and control the switching between the multiple balancing switches SW_mid, SW_bott, and SW_top based on the determined energy transfer direction. Therefore, the control unit 45 can perform module balancing according to the embodiment.

[0069] The control unit 45 can determine the module voltage of each of the first module M1, the second module M2, and the third module M3 based on the battery voltage transmitted by the monitoring IC 43. For example, referring to Figure 2 , the control unit 45 can determine the module voltage of the first module M1 by adding the respective cell voltages of the third battery cell Cell3 and the fourth battery cell Cell4 connected in series with each other. In addition, the control unit 45 can determine the cell voltage of the first battery cell Cell1 as the module voltage of the second module M2, and determine the cell voltage of the sixth battery cell Cell6 as the module voltage of the third module M3.

[0070] In some embodiments, the control unit 45 can determine the energy transfer direction for transferring energy from a module with a higher module voltage to a module with a lower module voltage. For example, the module voltage of the first module M1 can be greater than the module voltage of each of the second module M2 and the third module M3. In this case, the control unit 45 can determine the energy transfer direction for transferring energy from the first module M1 to the second module M2 and the third module M3 - that is, from the center to the outside of the battery 10. For another example, the module voltage of each of the second module M2 and the third module M3 can be greater than the module voltage of the module M1. In this case, the control unit 45 can determine the energy transfer direction for transferring energy from the second module M2 and the third module M3 to the first module M1 - that is, from the outside to the center of the battery 10.

[0071] Hereinafter, the specification refers to Figures 7 to 13 to describe in detail a specific method for performing module balancing. Based on the circuit diagram shown in Figure 2 , the module balancing method is described, and the module balancing method is not limited thereto, and the module balancing method described below can be equivalently applied to circuit diagrams of various embodiments such as the embodiments described with reference to Figures 7 to 13 . Figures 3 to 6 Described embodiments.

[0072] Figure 7 And Figure 8 are exemplary views of a charge equalization circuit that each shows transferring energy from a central module to an external module;Figure 9 is an example view showing waveforms of currents flowing through Figure 7 and Figure 8 the central module and the external module in Figure 10 is an example view showing waveforms of currents flowing through Figure 7 and Figure 8 the central module and the external module in

[0073] The central cell included in the battery 10 may have a higher degradation level because its temperature is higher than that of the lower cells and the upper cells arranged outside. Therefore, in a charging cycle in which the battery 10 is charged using power from an external device, the voltage of the first module M1 including the central cell may reach the charging upper limit voltage before the voltage of the second module M2 including the lower cells or the third module M3 including the upper cells. Further, in a discharging cycle in which the battery 10 supplies power to an external device, the voltage of the first module M1 including the central cell may reach the discharging lower limit voltage before the voltage of the second module M2 including the lower cells or the third module M3 including the upper cells. Here, the charging upper limit voltage is the maximum voltage for allowing charging within a non - dangerous range, and the discharging lower limit voltage is the minimum voltage for allowing discharging within a non - dangerous range.

[0074] Referring to Figure 7 and Figure 8 , for example, assume that the module voltage of the first module M1 is greater than the module voltage of each of the second module M2 and the third module M3. In this case, the control unit 45 may determine the energy transfer direction from the central module to the external module so that energy is transferred from the first module M1 having a larger module voltage to the second module M2 and the third module M3 each having a smaller module voltage.

[0075] First, referring to Figure 7 , the control unit 45 may control the central balance switch SW_mid to be turned on. Then, the first module M1 including the third battery cell Cell3 and the fourth battery cell Cell4 may be discharged, and the central module current I_mid may flow through the central balance switch SW_mid. Energy may be stored in the first upper inductor TR_top1 and the first lower inductor TR_bott1 through the central module current I_mid. That is, the third battery cell Cell3 and the fourth battery cell Cell4 may each be discharged.

[0076] Next, referring to Figure 8, the control unit 45 can control the central balance switch SW_mid to be turned off after a predetermined time when the central balance switch SW_mid is turned on. Due to the general electrical characteristics of the transformer, during the process of the energy stored in the first lower inductor TR_bott1 being transferred to the second lower inductor TR_bott2, the lower module current I_bott can then flow through the lower diode D_bott. Additionally, due to the general electrical characteristics of the transformer, during the process of the energy stored in the first upper inductor TR_top1 being transferred to the second upper inductor TR_top2, the upper module current I_top can flow through the upper diode D_top. That is to say, the first battery cell Cell1 can be charged through the lower module current I_bott, and the sixth battery cell Cell6 can be charged through the upper module current I_top. Here, the principle of energy transfer in each of the upper transformer and the lower transformer is the well-known transformer principle, and thus its detailed description is omitted.

[0077] Reference Figure 7 and Figure 8 , when the central balance switch SW_mid is turned on, the first module M1 including the third battery cell Cell3 and the fourth battery cell Cell4 can be discharged. When the central balance 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 can be charged respectively. That is to say, energy can be transferred from the first module M1 to the second module M2 and the third module M3.

[0078] Reference Figure 9 , when the central balance switch SW_mid is turned on, the first module M1 and the central balance switch SW_mid can be electrically connected to each other, thus forming a current path in the first equalization circuit 411. Here, due to the electrical interference of the first upper inductor TR_top1 and the first lower inductor TR_bott1, the magnitude of the central module current I_mid can gradually increase. When the central balance switch SW_mid is turned off, the first module M1 and the central balance switch SW_mid can be electrically disconnected from each other, and the magnitude of the central module current I_mid can be zero. Here, due to the electrical interference of the second upper inductor TR_top2 and the second lower inductor TR_bott2, the magnitude of each of the lower module current I_bott and the upper module current I_top can instantaneously increase and then gradually decrease. Here, based on the magnitude of energy transfer, a time difference can occur between the time point when the magnitude of each of the lower module current I_bott and the upper module current I_top is zero and the time point when the next central balance switch SW_mid is turned on. or .

[0079] Reference Figure 10 ,The current of the lower module current I_bott and the current of the upper module current I_top may have different waveforms based on various reasons such as the magnitude of the central module current I_mid or the on / off switching time of the central balance switch SW_mid. The control unit 45 may control the on / off switching time of the central balance switch SW_mid based on the voltage difference between the first module M1, the second module M2, and the third module M3.

[0080] Figure 11 and Figure 12 are exemplary views each showing a charge equalization circuit for transferring energy from an external module to a central module; and Figure 13 is a view showing the flow through Figure 11 and Figure 12 An exemplary view of the waveforms of the currents of the central module and the external module in.

[0081] Reference Figure 11 and Figure 12 ,For example, assume that the module voltages of the second module M2 and the third module M3 are greater than the module voltage of the first module M1. In this case, the control unit 45 may determine the energy transfer direction from the external module to the central module so that energy is transferred from the second module M2 and the third module M3, each having a larger module voltage, to the first module M1 having a smaller module voltage.

[0082] First, referring to Figure 11 ,the control unit 45 may control the lower balance switch SW_bott and the upper balance switch SW_top to be turned on. The second module M2 including the first battery cell Cell1 may then be discharged, and the lower module current I_bott may flow through the lower balance switch SW_bott. In addition, the third module M3 including the sixth battery cell Cell6 may be discharged, and the upper module current I_top may flow through the upper balance switch SW_top. Energy may be stored in the second lower inductor TR_bott2 and the second upper inductor TR_top2 through 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 may each be discharged.

[0083] Next, referring to Figure 12, after a predetermined time has elapsed after the control unit 45 turns on the lower balance switch SW_bott and the upper balance switch SW_top, the control unit 45 can turn off the lower balance switch SW_bott and the upper balance switch SW_top. Due to the general electrical characteristics of the transformer, during the process of the energy stored in the second lower inductor TR_bott2 being transferred to the first lower inductor TR_bottl, the first central module current I_mid1 can thus flow through the first central diode D_mid1. Additionally, due to the general electrical characteristics of the transformer, during the process of the energy stored in the second upper inductor TR_top2 being transferred to the first upper inductor TR_top1, the second central module current I_mid2 can flow through the second central diode D_mid2.

[0084] Reference Figure 2 and Figure 12 , in the balance path BL, the directions of the first central module current I_mid1 and the second central module current I_mid2 can be opposite to each other. For example, no current may flow in the balance path BL because when the first central module current I_mid1 and the second central module current I_mid2 have the same magnitude as each other, the currents cancel each other out. For another example, a minute current may flow in the balance path BL because when the first central module current I_mid1 and the second central module current I_mid2 have the same magnitude as each other, the currents cancel each other out. Figure 12 Both the first central module current I_mid1 and the second central module current I_mid2 flowing in the balance path BL are shown, but the present disclosure is not limited thereto, and no current may flow in the balance path BL.

[0085] Reference Figure 12 , assuming that the first central module current I_mid1 and the second central module current I_mid2 are included in the central module current I_mid. That is, the third battery cell Cell3 and the fourth battery cell Cell4 can be charged through the central module current I_mid. Here, the principle of energy transfer in each of the upper transformer and the lower transformer is the well-known transformer principle, and thus its detailed description is omitted.

[0086] Reference Figure 11 and Figure 12, when the lower balance switch SW_bott and the upper balance 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 balance switch SW_bott and the upper balance 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.

[0087] Reference Figure 2 、 Figure 11 and Figure 13 , when the lower balance switch SW_bott is turned on, the second module M2 and the lower balance switch SW_bott can be electrically connected to each other to thus form a current path in the second equalization circuit 412. When the upper balance switch SW_top is turned on, the third module M3 and the upper balance switch SW_top can be electrically connected to each other to thus form a current path in the third equalization circuit 413. Here, due to the electrical interference of the second lower inductor TR_bott2 and the second upper inductor TR_top2, the magnitude of each of the lower module current I_bott and the upper module current I_top can gradually increase. When the lower balance switch SW_bott and the upper balance switch SW_top are turned off, the current path can disappear in each of the second equalization circuit 412 and the third equalization circuit 413, and the magnitude of each of the lower module current I_bott and the upper module current I_top can be zero. Here, due to the electrical interference of the first lower inductor TR_bott1 and the first upper inductor TR_top1, the magnitude of the central module current I_mid can instantaneously increase and then gradually decrease. Here, based on the magnitude of the energy transfer, a time difference can occur between the time point when the magnitude of the central module current I_mid is zero and the time point when the next lower balance switch SW_bott and upper balance switch SW_top are turned on or 。

[0088] Figure 14 is a flowchart showing a module balancing method according to another embodiment.

[0089] This specification refers to Figures 1 to 14 to describe in detail the module balancing method and the battery management system.

[0090] Reference Figure 14 , the BMS 40 can monitor the individual voltages of each of the multiple battery cells Cell1 to Cell6 (S100).

[0091] The BMS 40 can determine the module voltage of each of the first module M1, the second module M2, and the third module M3 based on the battery cell voltages of a plurality of battery cells Cell1 to Cell6. For example, referring to Figure 2 , the BMS 40 can determine the module voltage of the first module M1 by adding the respective cell voltages of the third battery cell Cell3 and the fourth battery cell Cell4 connected in series with each other. Additionally, the BMS 40 can determine the cell voltage of the first battery cell Cell1 as the module voltage of the second module M2, and determine 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 external modules.

[0092] Next, the BMS 40 can determine the energy transfer direction (S200) by comparing the voltage of the central module with the voltage of the external module.

[0093] In step S200, the BMS 40 can determine whether the voltage of the central module is greater than the voltage of the external module (S210).

[0094] For example, referring to Figure 7 , assume that the module voltage of the first module M1 is greater than the module voltage of each of the second module M2 and the third module M3. In this case, the BMS 40 can determine the energy transfer direction from the central module to the external module so that energy is transferred from the first module M1 with a larger module voltage to the second module M2 and the third module M3 each with a smaller module voltage.

[0095] In step S200, when the voltage of the central module is less than the voltage of the external module (No in S210), the BMS 40 can determine whether the voltage of the external module is greater than the voltage of the central module (S220).

[0096] For example, referring to Figure 12 , assume that the module voltage of each of the second module M2 and the third module M3 is greater than the module voltage of the first module M1. In this case, the BMS 40 can determine the energy transfer direction from the external module to the central module so that energy is transferred from the second module M2 and the third module M3 each with a larger module voltage to the first module M1 with a smaller module voltage.

[0097] In step S200, when the voltage of the central module and the voltage of the external module have the same magnitude (No in S220), the BMS 40 can not perform module balancing.

[0098] Next, the BMS 40 can perform module balancing so that energy is transferred in the determined energy transfer direction (S300).

[0099] In step S300, when the voltage of the central module is greater than the voltage of the external module (Yes in S210), the BMS 40 may perform module balancing to transfer energy from the central module to the external module (S310).

[0100] For example, referring to Figure 7 , the BMS 40 may control the central balance switch SW_mid to be turned on. The first module M1 as the central module may then be discharged, and the central module current I_mid may flow through the central balance switch SW_mid. Energy may be stored in the first upper inductor TR_top1 and the first lower inductor TR_bott1 through the central module current I_mid. That is, the first module M1 as the central module may be discharged.

[0101] Referring to Figure 8 , the BMS 40 may control the central balance switch SW_mid to be turned off when a predetermined time has elapsed after controlling the central balance switch SW_mid to be turned on. Due to the general electrical characteristics of the transformer, during the process of the energy stored in the first lower inductor TR_bott1 being transferred to the second lower inductor TR_bott2, the lower module current I_bott may then flow through the lower diode D_bott. Additionally, due to the general electrical characteristics of the transformer, during the process of the energy stored in the first upper inductor TR_top1 being transferred to the second upper inductor TR_top2, the upper module current I_top may flow through the upper diode D_top. That is, the first battery cell Cell1 may be charged through the lower module current I_bott, and the sixth battery cell Cell6 may be charged through the upper module current I_top. Here, the principle of transferring energy in each of the upper transformer and the lower transformer is the well-known transformer principle, and thus its detailed description is omitted.

[0102] In summary, the BMS 40 may control the central balance switch SW_mid to be turned off when a predetermined time has elapsed after controlling the central balance switch SW_mid to be turned on. Then, energy may be transferred from the first module M1 as the central module to the second module M2 and the third module M3 as the external modules. In some embodiments, the BMS 40 may repeat the on / off switching control of the central balance switch SW_mid until the voltage of each of the first module M1, the second module M2, and the third module M3 falls within a predetermined error range.

[0103] In step S300, when the voltage of the external module is greater than the voltage of the central module (Yes in S220), the BMS 40 may perform module balancing to transfer energy from the external module to the central module (S320).

[0104] For example, referring to Figure 11 , the BMS 40 can control the lower balancing switch SW_bott and the upper balancing switch SW_top to be turned on. The second module M2 as an external module can then be discharged, and the lower module current I_bott can flow through the lower balancing switch SW_bott. Additionally, the third module M3 as another external module can be discharged, and the 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 through the lower module current I_bott and the upper module current I_top. That is to say, the second module M2 and the third module M3 can be discharged.

[0105] Referring to Figure 12 , the BMS 40 can control the lower balancing switch SW_bott and the upper balancing switch SW_top to be turned off after a predetermined time has elapsed after controlling the lower balancing switch SW_bott and the upper balancing switch SW_top to be turned on. Due to the general electrical characteristics of the transformer, during the process of the energy stored in the second lower inductor TR_bott2 being transferred to the first lower inductor TR_bottl, the first central module current I_mid1 can thus flow through the first central diode D_mid1. Additionally, due to the general electrical characteristics of the transformer, during the process of the energy stored in the second upper inductor TR_top2 being transferred to the first upper inductor TR_top1, the second central module current I_mid2 can flow through the second central diode D_mid2.

[0106] In summary, the BMS 40 can control the lower balancing switch SW_bott and the upper balancing switch SW_top to be turned off after a predetermined time has elapsed after controlling the lower balancing switch SW_bott and the upper balancing switch SW_top to be turned on. Then, the energy in the second module M2 and the third module M3 as external modules can be transferred to the first module M1 as the central module. In some embodiments, the BMS 40 can repeat the on / off switching control of the lower balancing switch SW_bott and the upper balancing switch SW_top until the voltage of each of the first module M1, the second module M2, and the third module M3 falls within a predetermined error range.

[0107] Although the embodiments of the present disclosure have been described in detail above, the scope of the present disclosure is not limited thereto. Various modifications and improvements made by those skilled in the art to which the present disclosure pertains also fall within the scope of the present disclosure.

Claims

1. A battery management system, comprising: a charge equalization circuit that performs module balancing among a plurality of battery cells connected in series with each other, between a first module including a plurality of central cells, a second module including at least one lower cell, and a third module including at least one upper cell, wherein each of the plurality of central cells has a potential falling within a central potential range, the at least one lower cell has a potential falling within a lower potential range, and the at least one upper cell has a potential falling within an upper potential range; and a control unit that calculates a module voltage for each of the first module, the second module, and the third module based on a cell voltage of each of the plurality of battery cells, determines an energy transfer direction based on the calculated module voltages, and controls the module balancing based on the determined energy transfer direction.

2. The system according to claim 1, wherein the central potential range includes: a central potential set at the center of a plurality of potential magnitudes of the plurality of battery cells and a potential falling within an upper range or a lower range of a predetermined magnitude from the central potential, the lower potential range includes: the minimum potential among the plurality of potential magnitudes of the plurality of battery cells and a potential falling within a range of a predetermined magnitude from the minimum potential, and the upper potential range includes: the maximum potential among the plurality of potential magnitudes of the plurality of battery cells and a potential falling within a range of a predetermined magnitude from the maximum potential.

3. The system according to claim 1, wherein the first module includes: the plurality of central cells corresponding to an even integer multiple.

4. The system according to claim 1, wherein the charge equalization circuit includes: a first equalization circuit including a central balance switch, a first upper inductor connected between a positive electrode of the first module and one end of the central balance switch, a first lower inductor connected between a negative electrode of the first module and the other end of the central balance switch, a first central diode and a second central diode connected in series with each other between a first node and a second node, and a balance path connecting a center of the plurality of central cells included in the first module to a center of the first central diode and the second central diode, the first node is provided between the first upper inductor and one end of the central balance switch, and the second node is provided between the first lower inductor and the other end of the central balance switch.

5. The system according to claim 4, wherein the charge equalization circuit includes: a second equalization circuit including a lower balance switch, a second lower inductor connected between a positive electrode of the second module and one end of the lower balance switch, and a lower diode connected between both ends of the lower balance switch.

6. The system according to claim 5, wherein the charge equalization circuit includes: A third balancing circuit, the third balancing 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.

7. The system according to claim 4, wherein, the control unit controls the central balancing switch to be turned off after a predetermined time when the module voltage of the first module is greater than the module voltage of each of the second module and the third module after turning on the central balancing switch.

8. The system according to claim 6, wherein, the control unit controls the lower balancing switch and the upper balancing switch to be turned off after a predetermined time when the module voltage of each of the second module and the third module is greater than the module voltage of the first module after turning on the lower balancing switch and the upper balancing switch.

9. A module balancing method, the module balancing method being a method for performing module balancing between a plurality of battery modules, including: monitoring the cell voltages of the plurality of battery cells connected in series with each other to determine the module voltage of each of a first module including a plurality of central cells, a second module including at least one lower cell, and a third module including at least one upper cell among the plurality of battery cells connected in series with each other, each of the plurality of central cells having a potential falling within a central potential range, the at least one lower cell having a potential falling within a lower potential range, and the at least one upper cell having a potential falling within an upper potential range; determining the energy transfer direction by comparing the module voltage of the first module with the module voltage of each of the second module and the third module; and performing the module balancing between the first module, the second module, and the third module so that energy is transferred in the determined energy transfer direction.

10. The method according to claim 9, wherein, determining the energy transfer direction includes: determining whether the module voltage of the first module is greater than the module voltage of each of the second module and the third module, and as a result of the determination, when the module voltage of the first module is not greater than the module voltage of each of the second module and the third module, determining whether the module voltage of each of the second module and the third module is greater than the module voltage of the first module.

11. The method according to claim 10, wherein, performing the module balancing includes: when the module voltage of the first module is greater than the module voltage of each of the second module and the third module, performing the module balancing so that energy is transferred from the first module to the second module and the third module, and when the module voltage of each of the second module and the third module is greater than the module voltage of the first module, performing the module balancing so that energy is transferred from the second module and the third module to the first module.

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