Battery pack

Abstract

To provide a battery pack.SOLUTION: A battery pack according to the present invention includes a first battery rack coupled between a first pack terminal and a second pack terminal, a first power conversion circuit having a first terminal, a second terminal, a third terminal, and a fourth terminal coupled to the second pack terminal and configured to convert bidirectionally a first conversion voltage between the first terminal and the second terminal and a second conversion voltage between the third terminal and the fourth terminal, a second battery rack coupled between the first pack terminal and the third terminal of the first power conversion circuit, and a battery controller that controls the first power conversion circuit in order to regulate the level of the second conversion voltage.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a battery pack, and more particularly to a battery pack in which a plurality of battery racks are connected in parallel using a power conversion circuit. [Background technology]

[0002] Unlike primary batteries, which cannot be recharged, secondary batteries are batteries that can be charged and discharged. Small batteries are used in small portable electronic devices such as smartphones, feature phones, laptops, digital cameras, and camcorders, while large batteries are widely used in hybrid vehicles, electric vehicles, and energy storage systems. Large batteries generally consist of battery cells, battery modules, battery racks, and battery packs.

[0003] A battery cell is the basic unit of a secondary battery and includes an electrode assembly consisting of a positive electrode, a separator, and a negative electrode, electrode terminals connected to the positive and negative electrodes, and a case containing the electrode assembly and electrolyte. A battery module is an assembly in which a predetermined number of battery cells are combined and placed in a frame to increase battery output and protect the battery from external impact, heat, vibration, etc. A battery rack is completed by connecting multiple battery modules and adding a battery management system for thermal management and electrical control. The battery management system includes a microcontroller unit (MCU), an analog front end (AFE), protection elements, sensors, etc. A battery pack includes battery racks connected in parallel and a controller that communicates with the battery management system of the battery rack to manage and control the operation of the entire battery pack.

[0004] When a battery pack is used for a long period of time, a battery rack that has deteriorated over time may be replaced with a new battery rack, a new battery rack may be added, or some battery modules may be replaced or added. In this case, the deteriorated battery rack and the new battery rack are connected in parallel, which can cause an impedance imbalance problem. For example, even if the deteriorated battery rack is completely discharged and energy remains in the new battery rack, the energy stored in the new battery module may become unusable.

[0005] To solve this problem, the deteriorated battery rack was connected in parallel to a power conversion circuit and used together with the new battery rack. However, since a power conversion circuit with a large capacity that can accommodate the battery rack must be used, the cost of the power conversion circuit itself increases, and various problems arise, such as power consumption due to power conversion efficiency, heat generation, and space issues.

[0006] The information disclosed above in such background of the invention is intended solely to enhance understanding of the background of the invention and may therefore include information that does not constitute prior art. Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a battery pack that can connect a plurality of battery racks in parallel and use the same, using a small-capacity power conversion circuit.

[0008] However, the technical problems that the present invention aims to solve are not limited to the above-mentioned problems, and other problems not mentioned will be clearly understood by those skilled in the art from the following description of the invention. [Means for solving the problem]

[0009] According to one aspect of the present invention, a battery pack includes: a first battery rack connected between a first pack terminal and a second pack terminal; a first power conversion circuit having the first terminal, a second terminal, a third terminal, and a fourth terminal connected to the second pack terminal, and bidirectionally converting a first converted voltage between the first terminal and the second terminal and a second converted voltage between the third terminal and the fourth terminal; a second battery rack connected between the first pack terminal and the third terminal of the first power conversion circuit; and a battery controller that controls the first power conversion circuit to adjust the level of the second converted voltage.

[0010] According to one example, the second battery rack may be coupled between the first and second terminals of the first power conversion circuit, the first terminal of the first power conversion circuit may be coupled to the first pack terminal, and the second and third terminals of the first power conversion circuit may be coupled to each other.

[0011] According to another example, the first power conversion circuit may include a first switch between the first terminal and a first intermediate node, a second switch between the first intermediate node and a fourth terminal, and an inductor between a second intermediate node commonly coupled to the second terminal and the third terminal and the first intermediate node.

[0012] According to yet another example, the first power conversion circuit may include an additive polarity transformer having a primary winding coupled between a first terminal and a second terminal and a secondary winding coupled between a third terminal and a fourth terminal, a first switch coupled in series with the primary winding between the first terminal and the second terminal, and a second switch coupled in series with the secondary winding between the third terminal and the fourth terminal.

[0013] According to yet another example, the first battery rack may be coupled between the first and second terminals of the first power conversion circuit, the first terminal of the first power conversion circuit may be coupled to the first pack terminal, and the second and fourth terminals of the first power conversion circuit may be commonly coupled to the second pack terminal.

[0014] According to yet another example, the first power conversion circuit may include a first switch between the first terminal and a first intermediate node, an inductor between the first intermediate node and a third terminal, and a second switch between a second intermediate node commonly coupled to the second terminal and a fourth terminal and the first intermediate node.

[0015] According to yet another example, the battery pack may further include a battery module connected between the first terminal and the second terminal of the first power conversion circuit, and a second power conversion circuit having a fifth terminal connected to the first pack terminal and a sixth terminal, a seventh terminal, and an eighth terminal connected to the second pack terminal, and converting in both directions between the first battery voltage of the first battery rack connected between the fifth terminal and the sixth terminal and the third battery voltage of the battery module connected between the seventh terminal and the eighth terminal.

[0016] According to yet another example, the first power conversion circuit may include a first switch between the first terminal and a first intermediate node, a second switch between the first intermediate node and a fourth terminal, and an inductor between a second intermediate node commonly coupled to the second terminal and the third terminal and the first intermediate node.

[0017] According to yet another example, the second power conversion circuit may include an additive polarity transformer having a primary winding coupled between a fifth terminal and a sixth terminal and a secondary winding coupled between a seventh terminal and an eighth terminal, a third switch coupled in series with the primary winding between the fifth terminal and the sixth terminal, and a fourth switch coupled in series with the secondary winding between the seventh terminal and the eighth terminal.

[0018] According to yet another example, the first power conversion circuit may include an inductor between the first terminal and a first intermediate node, a first switch between the first intermediate node and a third terminal, and a second switch between a second intermediate node commonly coupled to the second terminal and a fourth terminal and the first intermediate node.

[0019] According to yet another example, the second power conversion circuit may include an additive polarity transformer having a primary winding coupled between a fifth terminal and a sixth terminal and a secondary winding coupled between a seventh terminal and an eighth terminal, a third switch coupled in series with the primary winding between the fifth terminal and the sixth terminal, and a diode coupled in reverse direction in series with the secondary winding between the seventh terminal and the eighth terminal.

[0020] According to yet another example, the battery controller can sense a third state of charge of the battery module and control the second power conversion circuit based on the third state of charge.

[0021] According to yet another example, the battery controller may sense a first state of charge of the first battery rack and a second state of charge of the second battery rack, and adjust the level of the second conversion voltage based on the difference between the first state of charge and the second state of charge.

[0022] According to yet another example, the battery controller may decrease the level of the second conversion voltage to increase the charging current of the second battery rack when the second state of charge is lower than the first state of charge in the charging mode, and may decrease the level of the second conversion voltage to decrease the discharging current of the second battery rack when the second state of charge is lower than the first state of charge in the discharging mode.

[0023] According to yet another example, the battery controller may sense the first battery current capacity of the first battery rack and the second battery current capacity of the second battery rack, sense the first battery current flowing through the first battery rack and the second battery current flowing through the second battery rack, and adjust the level of the second conversion voltage so that the ratio of the second battery current to the first battery current is the same as the ratio of the second battery current capacity to the first battery current capacity.

[0024] According to another aspect of the present invention, a battery pack includes: a first battery rack connected between a first pack terminal and a second pack terminal and having a first battery voltage; a first power conversion circuit including first through fourth terminals and a capacitor between the third and fourth terminals, for bidirectionally converting a first converted voltage between the first and second terminals and a second converted voltage across the capacitor; a second battery rack connected between the first pack terminal and the third terminal of the first power conversion circuit and having a second battery voltage; and a battery controller controlling the first power conversion circuit to adjust the level of the second converted voltage of the first power conversion circuit. The second battery rack and the capacitor of the first power conversion circuit are connected in series between the first pack terminal and the second pack terminal.

[0025] According to one example, the second battery rack may be coupled between the first terminal and the second terminal of the first power conversion circuit.

[0026] According to another example, the first battery rack may be coupled between the first terminal and the second terminal of the first power conversion circuit.

[0027] According to yet another example, the battery pack may further include a battery module coupled between the first terminal and the second terminal of the first power conversion circuit and having a third battery voltage; and a second power conversion circuit having a fifth terminal coupled to the first pack terminal, a sixth terminal coupled to the second pack terminal, a seventh terminal coupled to the first terminal, and an eighth terminal coupled to the second terminal, and bidirectionally converting the first battery voltage between the fifth terminal and the sixth terminal and the third battery voltage between the seventh terminal and the eighth terminal.

[0028] According to yet another example, the battery controller may sense a first battery current flowing through the first battery rack and a second battery current flowing through the second battery rack, and adjust the level of the second conversion voltage based on the ratio of the second battery current to the first battery current and the ratio of the second battery capacity of the second battery rack to the first battery capacity of the first battery rack. [Effects of the Invention]

[0029] According to the present invention, a battery pack can be provided in which multiple battery racks are connected in parallel using a small-capacity power conversion circuit. By minimizing the capacity of the power conversion circuit, the value of the power conversion circuit itself can be reduced and the heat generated during the power conversion process can also be reduced. Because the impact of heat generated by the power conversion circuit on the battery cells is reduced, the power conversion circuit and the battery cells can be arranged in the same space.

[0030] The capacity and output voltage range of the battery rack connected in series with the power conversion circuit can be freely varied, which can provide higher usability, for example, there is no limit to the number of battery modules that must be included in the battery rack.

[0031] However, the effects obtained through the present invention are not limited to the above-mentioned effects, and other technical effects not mentioned will be clearly understood by those skilled in the art from the following description of the invention. [Brief explanation of the drawings]

[0032] The following drawings attached to this specification illustrate preferred embodiments of the present invention and, together with the detailed description of the invention described below, serve to further understand the technical concept of the present invention, and the present invention should not be interpreted as being limited solely to the matters shown in such drawings. [Figure 1] 1 is a block diagram illustrating a battery pack according to one embodiment of the present invention. [Figure 2] FIG. 2 is a circuit diagram showing an example of the battery pack shown in FIG. [Figure 3] 1. FIG. 4 is a circuit diagram showing another example of the battery pack shown in FIG. [Figure 4] FIG. 10 is a block diagram illustrating a battery pack according to another embodiment of the present invention. [Figure 5] FIG. 5 is a circuit diagram showing an example of the battery pack shown in FIG. 4. [Figure 6] FIG. 10 is a block diagram illustrating a battery pack according to yet another embodiment of the present invention. [Figure 7] FIG. 7 is a circuit diagram showing an example of the battery pack shown in FIG. 6. [Figure 8] FIG. 7 is a circuit diagram showing another example of the battery pack shown in FIG. 6. DETAILED DESCRIPTION OF THE INVENTION

[0033] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. Prior to this, the terms and phrases used in the specification and claims should not be construed as being limited to their ordinary or dictionary meanings, but should be construed in terms of meanings and concepts that correspond to the technical ideas of the present invention, based on the principle that the inventor can appropriately define the concepts of terms in order to best describe his or her invention. Therefore, it should be understood that the embodiments and illustrated configurations described in this specification are merely some of the most preferred embodiments of the present invention and do not represent the technical ideas of the present invention, and that various equivalents and modifications may exist that can replace them at the time of filing this application.

[0034] As used herein, "comprise" and / or "comprising" specify the presence of a stated feature, number, step, operation, member, element, and / or group thereof, but do not exclude the presence or addition of one or more other features, numbers, operations, members, elements, and / or groups. When describing embodiments of the present invention, "may" and "also" can include "one or more embodiments of the present invention."

[0035] To facilitate understanding of the invention, the accompanying drawings may not be drawn to scale, and the dimensions of some components may be exaggerated. Furthermore, the same reference numerals may be used to refer to the same components in different embodiments.

[0036] A statement that two comparison objects are "identical" means that they are "substantially identical." Therefore, "substantially identical" may include deviations that are considered low in the art, for example, deviations within 5%. A certain parameter being uniform in a given region may mean that the parameters are uniform on average.

[0037] Even if terms such as "first," "second," etc. are used to describe various elements, it goes without saying that these elements are not limited by these terms. These terms are used only to distinguish one element from another, and it goes without saying that a first element is also a second element unless otherwise specified.

[0038] Throughout the specification, unless specifically stated to the contrary, each element may be singular or plural.

[0039] When a structure is placed "on top (or bottom)" of a component or "on (or under)" a component, it means that the structure is placed in contact with the upper surface (or lower surface) of the component, and that other structures may be interposed between the component and the structure placed on (or under) the component.

[0040] Furthermore, when a component is described as being "coupled," "coupled," or "connected" to another component, it should be understood that the components may be directly coupled or connected to each other, but that other components may be "interposed" between the components, or that each component may be "coupled," "coupled," or "connected" via other components. Furthermore, when a part is said to be electrically coupled to another part, this includes not only the case where they are directly coupled, but also the case where they are coupled via another element between them.

[0041] Throughout the specification, "A and / or B" means A, or B, or A and B, unless specifically stated to the contrary. That is, "and / or" includes all or any combination of the listed items. "C through D" means at least C and at most D, unless specifically stated to the contrary.

[0042] FIG. 1 illustrates a block diagram of a battery pack according to one embodiment of the present invention.

[0043] Referring to FIG. 1, the battery pack 100 includes first and second pack terminals 101 and 102, a first battery rack 110, a second battery rack 120, a power conversion circuit 130, and a battery controller 140. The first battery rack 110 is connected between the first and second pack terminals 101 and 102. The power conversion circuit 130 has first through fourth terminals P1, P2, P3, and P4. The fourth terminal P4 of the power conversion circuit 130 is connected to the second pack terminal 102. The power conversion circuit 130 bidirectionally converts a first converted voltage V2 between the first and second terminals P1 and P2 and a second converted voltage V3 between the third and fourth terminals P3 and P4. The second battery pack 120 is connected between the first pack terminal 101 and the third terminal P3 of the power conversion circuit 130. The battery controller 140 can control the power conversion circuit 130 to adjust the level of the second converted voltage V3.

[0044] The first and second pack terminals 101, 102 may be connected to a charging device for charging the battery pack 100 or to an electrical load that receives power from the battery pack 100. The voltage between the first pack terminal 101 and the second pack terminal 102 is referred to as a pack voltage, and it is assumed that the first pack terminal 101 has a higher potential than the second pack terminal 102.

[0045] The first battery rack 110 may include a plurality of first battery modules connected in series. The first battery rack 110 may include, for example, 12 or 16 first battery modules connected in series. The first battery module may have, for example, a battery capacity of 7.6 kWh and a module voltage of, for example, 68.2 V to 91.3 V depending on the state of charge. The voltage between the positive and negative terminals of the first battery rack 110 is referred to as the first battery voltage V1 or first rack voltage.

[0046] Each of the first battery modules may include a plurality of first battery cells. For example, each of the first battery modules may include 22 first battery cells connected in series, each having a cell capacity of 94 Ah. The first battery cells are components that store power and are also rechargeable secondary batteries. For example, the first battery cells may include at least one selected from the group consisting of a lithium ion battery, a lithium polymer battery, a nickel cadmium battery, a nickel metal hydride battery (Ni-MH), a nickel-zinc battery (Ni-Zn), a lead-acid battery, etc.

[0047] The first battery modules may each include a first module manager for managing the first battery cells. The first battery rack 110 may further include a first rack manager communicatively coupled to the first module manager.

[0048] The present invention is not limited by the number of first battery modules constituting the first battery rack 110 and the connection relationship of the first battery modules, nor by the number of first battery cells constituting the first battery module and the connection relationship of the first battery cells.

[0049] The second battery rack 120 may include a plurality of second battery modules connected in series. The second battery rack 120 may include, for example, four, six, or eight second battery modules connected in series. The second battery module may have, for example, a battery capacity of 24.3 kWh and a module voltage of, for example, 68.2 V to 91.3 V depending on the state of charge. The voltage between the positive and negative terminals of the second battery rack 120 is referred to as the second battery voltage V2 or second rack voltage.

[0050] Each second battery module may include a plurality of second battery cells. For example, each second battery module may have a cell capacity of 150 Ah and may include a total of 44 second battery cells connected in series and parallel. For example, two battery strings, each of which includes 22 second battery cells connected in series, may be connected in parallel to form a second battery module. The second battery cells are components that store power and may also be rechargeable secondary batteries. For example, the second battery cells may be lithium-ion batteries, lithium polymer batteries, nickel-cadmium batteries, nickel-metal hydride batteries, nickel-zinc batteries, or lead-acid batteries.

[0051] The second battery modules may each include a second module manager for managing the second battery cells. The second battery rack 120 may further include a second rack manager communicatively coupled to the second module manager.

[0052] The number of second battery modules constituting the second battery rack 120, the connection relationship of the second battery modules, and the number of second battery cells constituting the second battery module and the connection relationship thereof do not limit the present invention.

[0053] The first battery rack 110 and the second battery rack 120 may have different configurations. The number and connection relationship of the battery modules constituting the first and second battery racks 110, 120 may differ from each other. For example, the first battery rack 110 may be composed of 12 battery modules, and the second battery rack 120 may be composed of 4 battery modules. The first and second battery racks 110, 120 may be composed of different numbers and connection relationships of battery cells constituting their respective battery modules. For example, the battery modules of the first battery rack 110 may be composed of battery cells with a cell capacity of 94 Ah, and the battery modules of the second battery rack 120 may be composed of battery cells with a cell capacity of 150 Ah. Even if the first battery rack 110 and the second battery rack 120 are composed of the same battery cells, their states of health may differ from each other. For example, the first battery rack 110 may be composed of new first battery cells, and the second battery rack 120 may be composed of degraded second battery cells.

[0054] The first battery rack 110 is connected between the first and second pack terminals 101, 102. The positive terminal of the first battery rack 110 is substantially directly connected to the first pack terminal 101, and the negative terminal of the first battery rack 110 is substantially directly connected to the second pack terminal 102. A contactor or a circuit breaker may be disposed between the positive terminal of the first battery rack 110 and the first pack terminal 101 and / or between the negative terminal of the first battery rack 110 and the second pack terminal 102.

[0055] The battery pack 100 may further include a first current sensor 111 for sensing a first battery current i1 flowing through the first battery rack 110. The battery pack 100 may further include a second current sensor 121 for sensing a second battery current i2 flowing through the second battery rack 120. The battery controller 140 may sense the first battery current i1 flowing through the first battery rack 110 via the first current sensor 111 and may sense the second battery current i2 flowing through the second battery rack 120 via the second current sensor 121.

[0056] According to another example, the first current sensor 111 may be included in the first battery rack 110. The first rack management unit of the first battery rack 110 may sense a first battery current i1 flowing through the first battery rack 110 using the first current sensor 111 and provide the magnitude of the first battery current i1 to the battery controller 140.

[0057] The second current sensor 121 may be included in the second battery rack 120. The second rack management unit of the second battery rack 120 may sense the second battery current i2 of the second battery rack 120 and provide the magnitude of the second battery current i2 to the battery controller 140. The first rack management unit of the first battery rack 110, the second rack management unit of the second battery rack 120, and the battery controller 140 may transmit and receive data via communication.

[0058] According to yet another example, the total pack current flowing through the battery pack 100 may be sensed via the first and second pack terminals 101 and 102. A main current sensor may be disposed on a high-current path between the first and second pack terminals 101. The battery controller 140 may sense the pack current through the main current sensor. According to another example, the first and second pack terminals 101 and 102 may be connected to an integrated controller, such as a power converter, which may sense the pack current of the battery pack 100 and provide the magnitude of the pack current to the battery controller 140. The battery controller 140 may calculate or predict the magnitude of the first battery current i1 based on the result of subtracting the magnitude of the second battery current i2 from the magnitude of the pack current.

[0059] The power conversion circuit 130 is also a bidirectional DC / DC converter having first to fourth terminals P1, P2, P3, and P4. The power conversion circuit 130 may convert a first converted voltage V2 (i.e., a second battery voltage V2) between the first and second terminals P1 and P2 into a second converted voltage V3 and output it between the third and fourth terminals P3 and P4, or may convert the second converted voltage V3 between the third and fourth terminals P3 and P4 into the first converted voltage V2 and output it between the first and second terminals P1 and P2.

[0060] The first terminal P1 and the second terminal P2 are connected to the second battery rack 120 and may receive a second battery voltage V2 from the second battery rack 120. The first converted voltage V2 between the first and second terminals P1 and P2 is substantially the same as the second battery voltage V2 from the second battery rack 120. The first terminal P1 is connected to the first pack terminal 101, and the fourth terminal P4 is connected to the second pack terminal 102. The second terminal P2 and the third terminal P3 are connected to each other.

[0061] As a result, as shown in FIG. 1, the second battery rack 120 and the third and fourth terminals P3, P4 of the power conversion circuit 130 are connected in series between the first and second pack terminals 101, 102, and the first battery voltage V1 of the first battery rack 110 is substantially equal to the sum of the second battery voltage V2 of the second battery rack 120 and the second conversion voltage V3.

[0062] The power conversion circuit 130 is controlled by the battery controller 140. The battery controller 140 may adjust the level of the second conversion voltage V3 based on the second battery current i2. For example, the battery controller 140 may adjust the level of the second conversion voltage V3 so that the ratio between the first battery current i1 and the second battery current i2 is equal to a ratio setting value. Here, the ratio setting value may be set according to the ratio between the first battery current capacity of the first battery rack 110 and the second battery current capacity of the second battery rack 120.

[0063] As the first battery rack 110 and the second battery rack 120 deteriorate, the battery capacities of the first battery rack 110 and the second battery rack 120 decrease. Therefore, the battery controller 140 may periodically monitor the first battery current capacity of the first battery rack 110 and the second battery current capacity of the second battery rack 120. The battery controller 140 may update or reset the ratio setting value based on the ratio between the first battery current capacity of the first battery rack 110 and the second battery current capacity of the second battery rack 120. Herein, the battery current capacity refers to the total amount of current that can be discharged until the state of charge decreases from 100% to 0%, and is measured in Ah. In this specification, cell capacity is also measured in Ah, and battery capacity is measured in Wh.

[0064] Since the battery controller 140 controls the power conversion circuit 130 so that the ratio between the first battery current i1 and the second battery current i2 is the same as the ratio between the first battery current capacity and the second battery current capacity, the first state of charge SOC1 of the first battery rack 110 and the second state of charge SOC2 of the second battery rack 120 increase or decrease correspondingly.

[0065] For example, if the first battery rack 110 is configured with 12 first battery modules, each with a battery capacity of 7.6 kWh, the first battery capacity of the first battery rack 110 is approximately 91.3 kWh. For example, if the second battery rack 120 is configured with 6 second battery modules, each with a battery capacity of 24.3 kWh, the battery capacity of the second battery rack 120 is approximately 145.7 kWh. The first battery voltage V1 of the first battery rack 110, which is configured with 12 first battery modules, is approximately twice the second battery voltage V2 of the second battery rack 120, which is configured with 6 second battery modules.

[0066] The first battery current capacity of the first battery rack 110 and the second battery current capacity of the second battery rack 120 are approximately 91.3 / 2:145.7. In this case, the battery controller 140 sets the ratio setting value to 1:3.2, and the battery controller 140 can adjust the level of the second conversion voltage V3 so that the ratio between the first battery current i1 and the second battery current i2 becomes 1:3.2.

[0067] For example, when the battery pack 100 is being charged, if the ratio between the first battery current i1 and the second battery current i2 is, for example, 1:3.0, the battery controller 140 may decrease the level of the second conversion voltage V3 to increase the second battery current i2. The battery controller 140 may decrease the level of the second conversion voltage V3 so that the ratio between the first battery current i1 and the second battery current i2 increases to a set ratio value.

[0068] When the battery pack 100 is discharging, if the ratio between the first battery current i1 and the second battery current i2 is, for example, 1:3.0, the battery controller 140 may increase the level of the second conversion voltage V3 to increase the second battery current i2. The battery controller 140 may increase the level of the second conversion voltage V3 so that the ratio between the first battery current i1 and the second battery current i2 increases to a ratio setting value.

[0069] According to another embodiment, the battery controller 140 may monitor a first state of charge (SOC1) of the first battery rack 110 and a second state of charge (SOC2) of the second battery rack 120. For example, the battery controller 140 may monitor the first state of charge (SOC1) based on the first battery current (i1) and monitor the second state of charge (SOC2) based on the second battery current (i2) using a coulomb counting method. According to another example, the battery controller 140 may estimate the first state of charge (SOC1) based on the open-circuit voltage of the first battery rack 110 and estimate the second state of charge (SOC2) based on the open-circuit voltage of the second battery rack 120. According to another example, the battery controller 140 may receive information regarding the first state of charge (SOC1) from a first rack management unit of the first battery rack 110 and receive information regarding the second state of charge (SOC2) from a second rack management unit of the second battery rack 120.

[0070] The battery controller 140 may adjust the level of the second conversion voltage V3 based on the first and second state of charge SOC1 and SOC2. According to one example, the battery controller 140 may adjust the level of the second conversion voltage V3 so that the first and second state of charge SOC1 and SOC2 are the same.

[0071] For example, when the battery pack 100 is being charged, if the first state of charge SOC1 is higher than the second state of charge SOC2, the battery controller 140 may increase the second battery current i2 charged to the second battery rack 120 so that the second state of charge SOC2 increases faster than the first state of charge SOC1. To this end, the battery controller 140 may reduce the level of the second conversion voltage V3.

[0072] Conversely, when the battery pack 100 is discharging, if the first state of charge SOC1 is higher than the second state of charge SOC2, the battery controller 140 may reduce the second battery current i2 discharged from the second battery rack 120 to decrease the second state of charge SOC2 more slowly than the first state of charge SOC1. To achieve this, the battery controller 140 may lower the level of the second conversion voltage V3.

[0073] In the past, when connecting a second battery rack of a different type to a first battery rack, a power conversion circuit was used to convert the second rack voltage of the second battery rack to the first rack voltage of the first battery rack. Since the power conversion circuit must convert all of the power output from the second battery rack, it must have a power conversion capacity large enough to accommodate the entire second battery rack. This increases the size and cost of the power conversion circuit and requires a separate heat dissipation means to dispose of the heat generated during the power conversion process.

[0074] In the present invention, because the power conversion circuit 130 and the second battery rack 120 are connected in series, the power conversion circuit 130 can convert only the power required to maintain the second converted voltage V3. Therefore, a power conversion circuit 130 having a smaller power conversion capacity than conventional power conversion circuits can be used. That is, the size and cost of the power conversion circuit 130 are reduced, and the heat generated thereby is also reduced, so a separate heat dissipation unit can be omitted. Furthermore, because the power conversion circuit 130 does not emit much heat, the power conversion circuit 130 can be positioned adjacent to the first and second battery racks 110 and 120, thereby reducing the overall area occupied by the battery pack 100.

[0075] FIG. 2 illustrates a circuit diagram according to an example of the battery pack illustrated in FIG.

[0076] 2, the battery pack 100a is connected between a first pack terminal 101 and a second pack terminal 102 and includes a first battery rack 110 having a first battery voltage V1, a second battery rack 120 having a second battery voltage V2, and a power conversion circuit 130a. Although not shown in FIG. 2, the battery pack 100a further includes a battery controller (140 in FIG. 1) that controls the power conversion circuit 130a. The battery pack 100a may further include a first current sensor (211 in FIG. 4) for sensing a first battery current i1 of the first battery rack 110 and / or a second current sensor (221 in FIG. 4) for sensing a second battery current i2 of the second battery rack 120.

[0077] The power conversion circuit 130a is also a bidirectional DC / DC converter having first through fourth terminals P1, P2, P3, and P4. The first terminal P1 is commonly connected to the first pack terminal 101 and the positive terminal of the second battery rack 120, the second terminal P2 and the third terminal P3 are commonly connected to the negative terminal of the second battery rack 120, and the fourth terminal P4 is connected to the second pack terminal 102.

[0078] The power conversion circuit 130a includes a first switch Q1 between the first terminal P1 and a first intermediate node N1, a second switch Q2 between the first intermediate node N1 and a fourth terminal P4, and an inductor L between the first intermediate node N1 and a second intermediate node N2. The second intermediate node N2 may be commonly connected to the second terminal P2 and the third terminal P3.

[0079] The first switch Q1 may include a first diode D1, and the second switch Q2 may include a second diode D2. For example, the first switch Q1 and the second switch Q2 may be insulated gate bipolar transistors (IGBTs) with the first diode D1 and the second diode D2 in the form of a body diode, respectively. In another example, the first switch Q1 and the second switch Q2 may be bipolar junction transistors (BJTs), field effect transistors (FETs), or metal oxide semiconductor FETs (MOSFETs).

[0080] The power conversion circuit 130a may further include a first capacitor C1 between the first terminal P1 and the second terminal P2. The power conversion circuit 130a may further include a second capacitor C2 between the third terminal P3 and the fourth terminal P4. The first capacitor C1 may be omitted.

[0081] The power conversion circuit 130a may convert the first converted voltage V2 between the first and second terminals P1 and P2 into a second converted voltage V3 and output it between the third and fourth terminals P3 and P4, or may convert the second converted voltage V3 between the third and fourth terminals P3 and P4 into the first converted voltage V2 and output it between the first and second terminals P1 and P2.

[0082] For example, when the first switch Q1 is turned on, a current flows from the first terminal P1 to the second terminal P2 via the first switch Q1 and inductor L, and energy is stored in the inductor L. When the first switch Q1 is turned off, the energy stored in the inductor L is transferred to the second capacitor C2 via the second diode D2. As a result, the first converted voltage V2 between the first and second terminals P1 and P2 is converted into the second converted voltage V3 between the third and fourth terminals P3 and P4. The level of the second converted voltage V3 is adjusted by the duty ratio of the first switch Q1. The battery controller 140 can adjust the level of the second converted voltage V3 by controlling the duty ratio of the first switch Q1.

[0083] When the second switch Q2 is turned on, current flows from the third terminal P3 to the fourth terminal P4 via the inductor L and the second switch Q2, and the energy stored in the second capacitor C2 is accumulated in the inductor L. When the second switch Q2 is turned off, the energy stored in the inductor L is transferred to the first capacitor C1 and the second battery rack 120 via the first diode D1. As a result, the second conversion voltage V3 between the third and fourth terminals P3 and P4 is converted into the first conversion voltage V2 between the first and second terminals P1 and P2. The levels of the first conversion voltage V2 and the second conversion voltage V3 are adjusted by the duty ratio of the second switch Q2. The battery controller 140 can adjust the level of the second conversion voltage V3 by controlling the duty ratio of the second switch Q2.

[0084] For example, the first battery rack 110 may include 12 first battery modules connected in series, and each first battery module may include 22 first battery cells connected in series. Each first battery cell may have a cell capacity of 94 Ah. The battery capacity of the first battery rack 110 may be 91.3 kWh. The first battery voltage V1 of the first battery rack 110 may be, for example, 818.4 V to 1095.6 V depending on the state of charge.

[0085] The second battery rack 120 includes four second battery modules connected in series, and each second battery module may include 44 second battery cells connected in series and parallel. Each second battery cell has a cell capacity of 150 Ah. The battery capacity of the second battery rack 120 is 97.7 kWh. The second battery voltage V2 of the second battery rack 120 is, for example, 272.8 V to 365.2 V depending on the state of charge.

[0086] The second conversion voltage V3 of the power conversion circuit 130a is 545.6V to 730.4V depending on the first battery voltage V1 and the second battery voltage V2. The power conversion circuit 130a may output the second conversion voltage V3 by boosting the first conversion voltage V2 by approximately two times. The boost ratio of the power conversion circuit 130a is approximately 2. The buck ratio of the power conversion circuit 130a may be adjusted by the battery controller 140 depending on the first battery current i1 and the second battery current i2. In this case, the power conversion circuit 130a may have a power conversion capacity of approximately 50 kW.

[0087] FIG. 3 illustrates another example circuit diagram of the battery pack illustrated in FIG.

[0088] 3, the battery pack 100b includes a first battery rack 110 having a first battery voltage V1, a second battery rack 120 having a second battery voltage V2, and a power conversion circuit 130b, which are connected between a first pack terminal 101 and a second pack terminal 102. Although not shown in FIG. 3, the battery pack 100b may further include at least one of a battery controller (140 in FIG. 1) that controls the power conversion circuit 130b, a first current sensor (111 in FIG. 1), and a second current sensor (121 in FIG. 1).

[0089] The power conversion circuit 130b is also a bidirectional DC / DC converter having first through fourth terminals P1, P2, P3, and P4. The power conversion circuit 130b is also a flyback converter. The first terminal P1 is commonly connected to the first pack terminal 101 and the positive terminal of the second battery rack 120, the second terminal P2 is commonly connected to the negative terminal of the second battery rack 120 and the third terminal P3, and the fourth terminal P4 is connected to the second pack terminal 102.

[0090] The power conversion circuit 130b includes an additive polarity transformer TR having a primary winding L1 coupled between a first terminal P1 and a second terminal P2 and a secondary winding L2 coupled between a third terminal P3 and a fourth terminal P4. The turns ratio between the primary winding L1 and the secondary winding L2 can be set according to a desired voltage conversion ratio of the power conversion circuit 130b.

[0091] The power conversion circuit 130b includes a first switch Q1 connected in series with the primary winding L1 between the first terminal P1 and the second terminal P2, and a second switch Q2 connected in series with the secondary winding L2 between the third terminal P3 and the fourth terminal P4. The first switch Q1 may include a first diode D1, and the second switch Q2 may include a second diode D2. For example, the first switch Q1 and the second switch Q2 may be insulated gate bipolar transistors (IGBTs) having the first diode D1 and the second diode D2 in the form of a body diode, respectively. According to another example, the first switch Q1 and the second switch Q2 may be bipolar junction transistors (BJTs), field effect transistors (FETs), or metal oxide semiconductor FETs (MOSFETs).

[0092] The power conversion circuit 130b may further include a second capacitor C2 between the third terminal P3 and the fourth terminal P4. The power conversion circuit 130b may further include a first capacitor C1 between the first terminal P1 and the second terminal P2. The first capacitor C1 may be omitted.

[0093] The power conversion circuit 130b may convert the first converted voltage V2 between the first and second terminals P1 and P2 into a second converted voltage V3 and output the second converted voltage V3 between the third and fourth terminals P3 and P4. In this case, the battery controller 140 may adjust the level of the second converted voltage V3 by controlling the duty ratio of the first switch Q1.

[0094] The power conversion circuit 130b may convert the second converted voltage V3 between the third and fourth terminals P3 and P4 into a first converted voltage V2 and output the first converted voltage V2 between the first and second terminals P1 and P2. In this case, the battery controller 140 may adjust the levels of the first converted voltage V2 and the second converted voltage V3 by controlling the duty ratio of the second switch Q2.

[0095] For example, the first battery rack 110 may include 12 first battery modules connected in series, and each first battery module may include 22 first battery cells connected in series. Each first battery cell may have a cell capacity of 94 Ah. The battery capacity of the first battery rack 110 may be 91.3 kWh. The first battery voltage V1 of the first battery rack 110 may be, for example, 818.4 V to 1095.6 V depending on the state of charge.

[0096] The second battery rack 120 includes six second battery modules connected in series, and each second battery module may include 44 second battery cells connected in series and parallel. Each second battery cell has a cell capacity of 150 Ah. The battery capacity of the second battery rack 120 is 145.7 kWh. The second battery voltage V2 of the second battery rack 120 is, for example, 409.2 V to 547.8 V depending on the state of charge.

[0097] The second converted voltage V3 of the power conversion circuit 130b may be 409.2V to 547.8V depending on the first battery voltage V1 and the second battery voltage V2. The power conversion circuit 130b may output the second converted voltage V3 such that the ratio between the magnitude of the first converted voltage V2 and the magnitude of the second converted voltage V3 is approximately 1:1. As described above, the voltage conversion ratio of the power conversion circuit 130b may be adjusted by the battery controller 140 depending on the first battery current i1 of the first battery rack 110 and the second battery current i2 of the second battery rack 120. In this case, the power conversion circuit 130b may have a power conversion capacity of approximately 69 kW.

[0098] FIG. 4 illustrates a block diagram of a battery pack according to another embodiment of the present invention.

[0099] Referring to FIG. 4, the battery pack 200 includes first and second pack terminals 201, 202, a first battery rack 210 having a first battery voltage V1, a second battery rack 220 having a second battery voltage V2, a power conversion circuit 230, and a battery controller 240.

[0100] The power conversion circuit 230 has first to fourth terminals P1, P2, P3, and P4. The first terminal P1 is connected to the first pack terminal 201, and the second terminal P2 and the fourth terminal P4 are connected to the second pack terminal 202. The power conversion circuit 230 bidirectionally converts a first converted voltage V2 between the first and second terminals P1 and P2 and a second converted voltage V3 between the third and fourth terminals P3 and P4.

[0101] The first battery rack 210 is connected between the first and second pack terminals 201, 202. The first battery rack 210 is connected between the first terminal P1 and the second terminal P2 of the power conversion circuit 230. The second battery pack 220 is connected between the first pack terminal 201 and the third terminal P3 of the power conversion circuit 230. The battery controller 240 may control the power conversion circuit 230 to adjust the level of the second conversion voltage V3.

[0102] The first battery rack 210 may include a plurality of first battery modules connected in series. Each of the first battery modules of the first battery rack 210 may include a plurality of first battery cells. The second battery rack 220 may include a plurality of second battery modules connected in series. Each of the second battery modules of the second battery rack 220 may include a plurality of second battery cells. The first battery rack 210 and the second battery rack 220 may have different configurations.

[0103] The positive and negative terminals of the first battery rack 210 are substantially directly connected to the first pack terminal 201 and the second pack terminal 202, respectively. The first battery rack 210 may be connected between the first pack terminal 201 and the second pack terminal 202 via a contactor or a circuit breaker.

[0104] The battery pack 200 may further include a first current sensor 211 and a second current sensor 221. The battery controller 240 may sense a first battery current i1 flowing through the first battery rack 210 via the first current sensor 211 and may sense a second battery current i2 flowing through the second battery rack 220 via the second current sensor 221.

[0105] The power conversion circuit 230 is also a bidirectional DC / DC converter having first to fourth terminals P1, P2, P3, and P4. The power conversion circuit 230 may convert a first converted voltage V1 between the first and second terminals P1 and P2 into a second converted voltage V3 and output the second converted voltage V3 between the third and fourth terminals P3 and P4, or may convert the second converted voltage V3 between the third and fourth terminals P3 and P4 into the first converted voltage V1 and output the first converted voltage V1 between the first and second terminals P1 and P2.

[0106] The first terminal P1 and the second terminal P2 are connected to the first battery rack 210 and may receive the first battery voltage V1 of the first battery rack 210. The first converted voltage V1 between the first and second terminals P1 and P2 is substantially equal to the first battery voltage V1 of the first battery rack 210. The first terminal P1 is connected to the first pack terminal 201, and the second terminal P2 and the fourth terminal P4 are connected to the second pack terminal 202. The third terminal P3 is connected to the negative terminal of the second battery rack 220. Thus, as shown in FIG. 4 , the second battery rack 220 and the third and fourth terminals P3 and P4 of the power conversion circuit 230 are connected in series between the first and second pack terminals 201 and 202, and the first battery voltage V1 of the first battery rack 210 is substantially equal to the sum of the second battery voltage V2 of the second battery rack 220 and the second converted voltage V3.

[0107] The power conversion circuit 230 is controlled by the battery controller 240. The battery controller 240 may adjust the level of the second conversion voltage V3 based on the second battery current i2. For example, the battery controller 240 may adjust the level of the second conversion voltage V3 so that the ratio between the first battery current i1 and the second battery current i2 is equal to a predetermined ratio setting value. Here, the ratio setting value may be set based on the ratio between the first battery current capacity of the first battery rack 210 and the second battery current capacity of the second battery rack 220.

[0108] Since the battery controller 240 controls the power conversion circuit 230 so that the ratio between the first battery current i1 and the second battery current i2 is the same as the ratio between the first battery current capacity of the first battery rack 210 and the second battery current capacity of the second battery rack 220, the first state of charge SOC1 of the first battery rack 210 and the second state of charge SOC2 of the second battery rack 220 may increase or decrease correspondingly.

[0109] For example, if the ratio between the first battery current capacity of the first battery rack 210 and the second battery current capacity of the second battery rack 220 is 1:3.2, the battery controller 240 may set the ratio setting value to 1:3.2, and the battery controller 240 may adjust the level of the second conversion voltage V3 so that the ratio between the first battery current i1 and the second battery current i2 becomes 1:3.2.

[0110] For example, when the battery pack 200 is being charged, if the ratio between the first battery current i1 and the second battery current i2 is, for example, 1:3.4, the battery controller 240 may increase the level of the second conversion voltage V3 to decrease the second battery current i2. The battery controller 240 may increase the level of the second conversion voltage V3 so that the ratio between the first battery current i1 and the second battery current i2 decreases to a set ratio value.

[0111] When the battery pack 200 is discharging, if the ratio between the first battery current i1 and the second battery current i2 is, for example, 1:3.4, the battery controller 240 may reduce the level of the second conversion voltage V3 to reduce the second battery current i2. The battery controller 240 may reduce the level of the second conversion voltage V3 so that the ratio between the first battery current i1 and the second battery current i2 decreases to a set ratio value.

[0112] According to another embodiment, the battery controller 240 may monitor a first state of charge SOC1 of the first battery rack 210 and a second state of charge SOC2 of the second battery rack 220. The battery controller 240 may adjust the level of the second conversion voltage V3 based on the first state of charge SOC1 and the second state of charge SOC2.

[0113] According to one example, the battery controller 240 may adjust the level of the second conversion voltage V3 so that the first state of charge SOC1 and the second state of charge SOC2 are the same. For example, if the first state of charge SOC1 is lower than the second state of charge SOC2 while the battery pack 200 is being charged, the battery controller 240 may reduce the second battery current i2 of the second battery rack 220 to increase the second state of charge SOC2 more slowly than the first state of charge SOC1. Therefore, the battery controller 240 may increase the level of the second conversion voltage V3.

[0114] Conversely, when the battery pack 200 is discharging, assuming that the first state of charge SOC1 is lower than the second state of charge SOC2, the battery controller 240 may increase the second battery current i2 of the second battery rack 220 to decrease the second state of charge SOC2 faster than the first state of charge SOC1. Therefore, the battery controller 240 may increase the level of the second conversion voltage V3.

[0115] In the present invention, because the power conversion circuit 230 and the second battery rack 220 are connected in series, the power conversion circuit 230 can convert only the power required to maintain the second converted voltage V3. Therefore, a power conversion circuit 230 having a smaller power conversion capacity than conventional power conversion circuits can be used. That is, the size and cost of the power conversion circuit 230 are reduced, and the heat generated thereby is also reduced, so a separate heat dissipation unit can be omitted. Furthermore, because the power conversion circuit 230 does not emit much heat, the power conversion circuit 230 can be positioned adjacent to the first and second battery racks 210 and 220, thereby reducing the overall area occupied by the battery pack 200.

[0116] FIG. 5 illustrates a circuit diagram according to an example of the battery pack illustrated in FIG.

[0117] 5, battery pack 200a is connected between first pack terminal 201 and second pack terminal 202 and includes a first battery rack 210 having a first battery voltage V1, a second battery rack 220 having a second battery voltage V2, and a power conversion circuit 230a. Although not shown in FIG. 5, battery pack 200a further includes a battery controller (240 in FIG. 4) that controls power conversion circuit 230a. Battery pack 200a may further include a first current sensor (211 in FIG. 4) for sensing a first battery current i1 of first battery rack 210 and / or a second current sensor (221 in FIG. 4) for sensing a second battery current i2 of second battery rack 220.

[0118] The power conversion circuit 230a is also a DC / DC converter having first through fourth terminals P1, P2, P3, and P4. The power conversion circuit 230a is also a buck converter. The first terminal P1 is commonly connected to the first pack terminal 201 and the positive terminal of the first battery rack 210, the second terminal P2 and the fourth terminal P4 are commonly connected to the second pack terminal 202, and the third terminal P3 is connected to the negative terminal of the second battery rack 220.

[0119] The power conversion circuit 230a includes a first switch Q1 between the first terminal P1 and a first intermediate node N1, an inductor between the first intermediate node N1 and a third terminal P3, and a second switch Q2 between the first intermediate node N1 and a second intermediate node N2. The second intermediate node N2 may be commonly connected to the second terminal P2 and the fourth terminal P4.

[0120] The first switch Q1 may include a first diode D1, and the second switch Q2 may include a second diode D2. For example, the first switch Q1 and the second switch Q2 may be insulated gate bipolar transistors (IGBTs) with the first diode D1 and the second diode D2 in the body diode configuration, respectively. In other examples, the first switch Q1 and the second switch Q2 may be bipolar junction transistors (BJTs), field effect transistors (FETs), or metal oxide semiconductor FETs (MOSFETs).

[0121] The power conversion circuit 230a may further include a second capacitor C2 between the third terminal P3 and the fourth terminal P4. The power conversion circuit 230a may further include a first capacitor C1 between the first terminal P1 and the second terminal P2. The first capacitor C1 may be omitted.

[0122] The power conversion circuit 230a may convert the first converted voltage V1 between the first and second terminals P1 and P2 into a second converted voltage V3 and output it between the third and fourth terminals P3 and P4, or may convert the second converted voltage V3 between the third and fourth terminals P3 and P4 into the first converted voltage V1 and output it between the first and second terminals P1 and P2.

[0123] For example, when the first switch Q1 is turned on and the second switch Q2 is turned off, current flows from the first terminal P1 to the third terminal P3 via the first switch Q1 and inductor L, and energy from the first capacitor C1 is stored in the inductor L. When the first switch Q1 is turned off and the second switch Q2 is turned on, the energy stored in the inductor L is transferred to the second capacitor C2. As a result, the first converted voltage V1 between the first and second terminals P1 and P2 is converted into the second converted voltage V3 between the third and fourth terminals P3 and P4. The level of the second converted voltage V3 is adjusted by the duty ratio of the first switch Q1 and the second switch Q2. The battery controller 140 can adjust the level of the second converted voltage V3 by controlling the duty ratio of the first switch Q1 and the second switch Q2.

[0124] When the second switch Q2 is turned on and the first switch Q1 is turned off, the second capacitor C2, the inductor L, and the second switch Q2 form a closed circuit. Current flows from the first intermediate node N1 to the second intermediate node N2 via the inductor L, and the energy stored in the second capacitor C2 is accumulated in the inductor L. When the second switch Q2 is turned off, the energy stored in the inductor L is transferred to the first capacitor C1 via the first diode D1. As a result, the second conversion voltage V3 between the third and fourth terminals P3 and P4 is converted into the first conversion voltage V1 between the first and second terminals P1 and P2. Because the first conversion voltage V1 is the same as the first battery voltage V1 of the first battery rack 210, the level of the second conversion voltage V3 is adjusted by the duty ratio of the second switch Q2. The battery controller 140 can adjust the level of the second conversion voltage V3 by controlling the duty ratio of the second switch Q2.

[0125] For example, the first battery rack 210 may include 12 first battery modules connected in series, and each first battery module may include 22 first battery cells connected in series. Each first battery cell may have a cell capacity of 94 Ah. The battery capacity of the first battery rack 210 may be 91.3 kWh. The first battery voltage V1 of the first battery rack 210 may be, for example, 818.4 V to 1095.6 V depending on the state of charge.

[0126] The second battery rack 220 includes four second battery modules connected in series, and each second battery module may include 44 second battery cells connected in series and parallel. Each second battery cell has a cell capacity of 150 Ah. The battery capacity of the second battery rack 220 is 97.7 kWh. The second battery voltage V2 of the second battery rack 220 is, for example, 272.8 V to 365.2 V depending on the state of charge.

[0127] The second conversion voltage V3 of the power conversion circuit 230a is 545.6V to 730.4V depending on the first battery voltage V1 and the second battery voltage V2. The power conversion circuit 230a may output the second conversion voltage V3, which is approximately two-thirds the first conversion voltage V1. The buck ratio of the power conversion circuit 230a is approximately 0.67, and the buck ratio of the power conversion circuit 230a may be adjusted by the battery controller 240 depending on the first battery current i1 and the second battery current i2. In this case, the power conversion circuit 230a may have a capacity of approximately 110 kW.

[0128] FIG. 6 illustrates a block diagram of a battery pack according to yet another embodiment of the present invention.

[0129] 6, the battery pack 300 includes first and second pack terminals 301, 302, a first battery rack 310 having a first battery voltage V1, a second battery rack 320 having a second battery voltage V2, a first power conversion circuit 330, and a battery controller 360. The battery pack 300 further includes a battery module 340 having a third battery voltage V3 and a second power conversion circuit 350.

[0130] The first power conversion circuit 330 has first to fourth terminals P1, P2, P3, and P4. The first terminal P1 is connected to the positive terminal of the battery module 340, the second terminal P2 is connected to the negative terminal of the battery module 340, the third terminal P3 is connected to the negative terminal of the second battery rack 320, and the fourth terminal P4 is connected to the second pack terminal 302. The first power conversion circuit 330 bidirectionally converts a first converted voltage V3 between the first and second terminals P1 and P2 and a second converted voltage V4 between the third and fourth terminals P3 and P4.

[0131] The second power conversion circuit 350 has fifth to eighth terminals P5, P6, P7, and P8. The fifth terminal P5 is connected to the positive terminal of the first battery rack 310 and the first pack terminal 301, the sixth terminal P6 is connected to the negative terminal of the first battery rack 310 and the second pack terminal 302, the seventh terminal P7 is connected to the positive terminal of the battery module 340 and the first terminal P1 of the first power conversion circuit 330, and the eighth terminal P8 is connected to the negative terminal of the battery module 340 and the second terminal P2 of the first power conversion circuit 330.

[0132] The second power conversion circuit 350 converts the first battery voltage V1 between the fifth terminal P5 and the sixth terminal P6 and the third battery voltage V3 between the seventh terminal P7 and the eighth terminal P8 in both directions.

[0133] The first battery rack 310 is connected between the first and second pack terminals 301, 302. The first battery rack 310 is connected between the fifth terminal P5 and the sixth terminal P6 of the second power conversion circuit 350. The second battery pack 320 is connected between the first pack terminal 301 and the third terminal P3 of the first power conversion circuit 330. The battery module 340 is commonly connected between the first and second terminals P1, P2 of the first power conversion circuit 330 and between the seventh and eighth terminals P7, P8 of the second power conversion circuit 350.

[0134] The battery controller 360 may control the first power conversion circuit 330 to adjust the level of the second converted voltage V4. The battery controller 360 may control the second power conversion circuit 350 to maintain the state of charge of the battery module 340 within a predetermined range.

[0135] The first battery rack 310 may include a plurality of first battery modules connected in series. Each of the first battery modules of the first battery rack 310 may include a plurality of first battery cells. The second battery rack 320 may include a plurality of second battery modules connected in series. Each of the second battery modules of the second battery rack 320 may include a plurality of second battery cells. The first battery rack 310 and the second battery rack 320 may have different configurations.

[0136] The positive and negative terminals of the first battery rack 310 are substantially directly connected to the first pack terminal 301 and the second pack terminal 302, respectively. The first battery rack 310 may be connected between the first pack terminal 301 and the second pack terminal 302 via a contactor or a circuit breaker.

[0137] The battery pack 300 may further include a first current sensor 311 and a second current sensor 321. The battery controller 360 may sense a first battery current i1 flowing through the first battery rack 310 via the first current sensor 311 and may sense a second battery current i2 flowing through the second battery rack 320 via the second current sensor 321. The battery pack 300 may further include a current sensor (not shown) for sensing a third battery current flowing through the battery module 340.

[0138] The first power conversion circuit 330 is also a bidirectional DC / DC converter. The first power conversion circuit 330 may convert a first converted voltage V3 between the first and second terminals P1 and P2 into a second converted voltage V4 and output the second converted voltage V4 between the third and fourth terminals P3 and P4, or may convert the second converted voltage V4 between the third and fourth terminals P3 and P4 into the first converted voltage V3 and output the first converted voltage V3 between the first and second terminals P1 and P2.

[0139] The first terminal P1 and the second terminal P2 are respectively connected to the positive and negative terminals of the battery module 340 and may receive the third battery voltage V3 of the battery module 340. The first converted voltage V3 between the first and second terminals P1 and P2 is substantially equal to the third battery voltage V3 of the battery module 340. The third terminal P3 is connected to the negative terminal of the second battery rack 320, and the fourth terminal P4 is connected to the second pack terminal 302. Thus, as shown in FIG. 6 , the second battery rack 320 and the third and fourth terminals P3 and P4 of the first power conversion circuit 330 are connected in series between the first and second pack terminals 301 and 302, and the first battery voltage V1 of the first battery rack 310 is substantially equal to the sum of the second battery voltage V2 of the second battery rack 320 and the second converted voltage V4.

[0140] The second power conversion circuit 350 is also a bidirectional DC / DC converter. The second power conversion circuit 350 can convert the first battery voltage V1 between the fifth and sixth terminals P5 and P6 into a third battery voltage V3 and output it between the seventh and eighth terminals P7 and P8, or can convert the third battery voltage V3 between the seventh and eighth terminals P7 and P8 into the first battery voltage V1 and output it between the fifth and sixth terminals P5 and P6.

[0141] The fifth terminal P5 and the sixth terminal P6 are respectively connected to the positive and negative terminals of the first battery rack 310 and may receive the first battery voltage V1 of the first battery rack 310. The seventh terminal P7 and the eighth terminal P8 are respectively connected to the positive and negative terminals of the battery module 340 and may receive the third battery voltage V3 of the battery module 340.

[0142] The first power conversion circuit 330 and the second power conversion circuit 350 are controlled by a battery controller 360. The battery controller 360 may adjust the level of the second conversion voltage V4 based on the second battery current i2. For example, the battery controller 360 may adjust the level of the second conversion voltage V4 so that the ratio between the first battery current i1 and the second battery current i2 is equal to a ratio setting value. Here, the ratio setting value may be set based on the ratio between the first battery current capacity of the first battery rack 310 and the second battery current capacity of the second battery rack 320.

[0143] Since the first power conversion circuit 330 is controlled so that the ratio between the first battery current i1 and the second battery current i2 is the same as the ratio between the first battery current capacity of the first battery rack 310 and the second battery current capacity of the second battery rack 320, the first state of charge SOC1 of the first battery rack 310 and the second state of charge SOC2 of the second battery rack 320 may increase or decrease correspondingly.

[0144] According to another embodiment, the battery controller 360 may monitor a first state of charge SOC1 of the first battery rack 310 and a second state of charge SOC2 of the second battery rack 320. The battery controller 360 may adjust the level of the second conversion voltage V4 so that the first state of charge SOC1 and the second state of charge SOC2 are the same.

[0145] The battery controller 360 may sense a third state of charge SOC3 of the battery module 340. For example, the battery controller 360 may estimate the third state of charge SOC3 based on an open-circuit voltage of the battery module 340. The battery controller 360 may control the second power conversion circuit 350 based on the third state of charge SOC3. For example, the battery controller 360 may manage the third state of charge SOC3 of the battery module 340 so that the third state of charge SOC3 does not fall outside a predetermined range.

[0146] For example, the third state of charge SOC3 may be controlled to maintain a state of charge of 20% to 80%. If the third state of charge SOC3 is lower than a reference value, the second power conversion circuit 350 may be controlled to charge the battery module 340 with the energy stored in the first battery rack 310. Conversely, if the third state of charge SOC3 is higher than the reference value, the second power conversion circuit 350 may be controlled to charge the first battery rack 310 with the energy stored in the battery module 340.

[0147] According to one embodiment, the battery controller 360 may control the first power conversion circuit 330 so that the first state of charge SOC1 of the first battery rack 310 and the second state of charge SOC2 of the second battery rack 320 are the same. Power consumed during the power conversion process of the first power conversion circuit 330 may be understood to be supplied from the battery module 340. Energy used by the battery module 340 to operate the first power conversion circuit 330 may be understood to be supplied from the first battery rack 310 via the second power conversion circuit 350.

[0148] In the present invention, because the first power conversion circuit 330 and the second battery rack 320 are connected in series, the first power conversion circuit 330 can convert only the power required to maintain the second conversion voltage V4. Therefore, a first power conversion circuit 330 having a smaller power conversion capacity than conventional power conversion circuits can be used. That is, the size and cost of the first power conversion circuit 330 can be reduced, and the heat generated therefrom can also be reduced, making it possible to omit a separate heat dissipation unit. Furthermore, because the first power conversion circuit 330 does not emit much heat, the first power conversion circuit 330 can be positioned adjacent to the first and second battery racks 310 and 320, thereby reducing the overall area occupied by the battery pack 300.

[0149] FIG. 7 illustrates a circuit diagram according to an example of the battery pack illustrated in FIG.

[0150] 7, battery pack 300a is connected between first pack terminal 301 and second pack terminal 302 and includes a first battery rack 310 having a first battery voltage V1, a second battery rack 320 having a second battery voltage V2, a first power conversion circuit 330a having first through fourth terminals P1, P2, P3, and P4, a battery module 340 having a third battery voltage V3, and a second power conversion circuit 350a having fifth through eighth terminals P5, P6, P7, and P8. Although not shown in FIG. 5, battery pack 300a further includes a battery controller (360 in FIG. 6) that controls first power conversion circuit 330a and second power conversion circuit 350a. Battery pack 300a may further include a first current sensor (311 in FIG. 6) and a second current sensor (321 in FIG. 6).

[0151] The first power conversion circuit 330a is also a DC / DC converter. The first terminal P1 and the second terminal P2 are respectively connected to the positive and negative terminals of the battery module 340, the third terminal P3 is connected to the negative terminal of the second battery rack 320, and the fourth terminal P4 is connected to the second pack terminal 302.

[0152] The second power conversion circuit 350a is also an isolated DC / DC converter. The fifth terminal P5 and the sixth terminal P6 are respectively connected to the positive and negative terminals of the first battery rack 310, and the seventh terminal P7 and the eighth terminal P8 are respectively connected to the positive and negative terminals of the battery module 340.

[0153] The first power conversion circuit 330a includes a first switch Q1 between the first terminal P1 and a first intermediate node N1, a second switch Q2 between the first intermediate node N1 and a fourth terminal P4, and an inductor L between the first intermediate node N1 and a second intermediate node N2. The second intermediate node N2 may be commonly connected to the second terminal P2 and the third terminal P3.

[0154] The first switch Q1 may include a first diode D1, and the second switch Q2 may include a second diode D2. For example, the first switch Q1 and the second switch Q2 may be insulated gate bipolar transistors (IGBTs) with the first diode D1 and the second diode D2 in the body diode configuration, respectively. In other examples, the first switch Q1 and the second switch Q2 may be bipolar junction transistors (BJTs), field effect transistors (FETs), or metal oxide semiconductor FETs (MOSFETs).

[0155] The first power conversion circuit 330a may further include a second capacitor C2 between the third terminal P3 and the fourth terminal P4. The first power conversion circuit 330a may further include a first capacitor C1 between the first terminal P1 and the second terminal P2. The first capacitor C1 may be omitted.

[0156] The first power conversion circuit 330a may convert the first converted voltage V3 between the first and second terminals P1 and P2 into a second converted voltage V4 and output it between the third and fourth terminals P3 and P4, or may convert the second converted voltage V4 between the third and fourth terminals P3 and P4 into the first converted voltage V3 and output it between the first and second terminals P1 and P2.

[0157] For example, when the first switch Q1 is turned on, a current flows from the first terminal P1 to the second terminal P2 via the first switch Q1 and inductor L, and the energy stored in the first capacitor C1 and the battery module 340 is accumulated in the inductor L. When the first switch Q1 is turned off, the energy accumulated in the inductor L is transferred to the second capacitor C2 via the second diode D2. As a result, the first converted voltage V3 between the first and second terminals P1 and P2 is converted into the second converted voltage V4 between the third and fourth terminals P3 and P4. The level of the second converted voltage V4 is adjusted by the duty ratio of the first switch Q1. The battery controller 140 can adjust the level of the second converted voltage V4 by controlling the duty ratio of the first switch Q1.

[0158] When the second switch Q2 is turned on, current flows from the third terminal P3 to the fourth terminal P4 via the inductor L and the second switch Q2, and energy in the second capacitor C2 is stored in the inductor L. When the second switch Q2 is turned off, the energy stored in the inductor L is transferred to the first capacitor C1 and the battery module 340 via the first diode D1. As a result, the second converted voltage V4 between the third and fourth terminals P3 and P4 is converted into the first converted voltage V3 between the first and second terminals P1 and P2. The levels of the first converted voltage V3 and the second converted voltage V4 are adjusted by the duty ratio of the second switch Q2. The battery controller 140 can adjust the level of the second converted voltage V4 by controlling the duty ratio of the second switch Q2.

[0159] The second power conversion circuit 350a is also a flyback converter. The second power conversion circuit 350a includes an additive polarity transformer TR having a primary winding L1 coupled between a fifth terminal P5 and a sixth terminal P6 and a secondary winding L2 coupled between a seventh terminal P7 and an eighth terminal P8. The turns ratio between the primary winding L1 and the secondary winding L2 can be set according to a desired voltage conversion ratio of the second power conversion circuit 350a.

[0160] The second power conversion circuit 350a includes a third switch Q3 connected in series with the primary winding L1 between the fifth terminal P5 and the sixth terminal P6, and a fourth switch Q4 connected in series with the secondary winding L2 between the seventh terminal P7 and the eighth terminal P8. The third switch Q3 may include a third diode D3, and the fourth switch Q4 may include a second diode D4. For example, the third switch Q3 and the fourth switch Q4 may be field-effect transistors (FETs) having the third diode D3 and the fourth diode D4 in the form of a body diode, respectively. According to another example, the third switch Q3 and the fourth switch Q4 may be bipolar junction transistors (BJTs), insulated gate bipolar transistors (IGBTs), or metal-oxide semiconductor FETs (MOSFETs).

[0161] The second power conversion circuit 350a may further include a third capacitor C3 between the fifth terminal P5 and the sixth terminal P6. The second power conversion circuit 350a may further include a fourth capacitor C4 between the seventh terminal P7 and the eighth terminal P8. The third capacitor C3 and / or the fourth capacitor C4 may be omitted.

[0162] The second power conversion circuit 350a converts the first battery voltage V1 between the fifth and sixth terminals P5 and P6 into a third battery voltage V3 and outputs it between the seventh and eighth terminals P7 and P8. In this case, the battery controller 140 can adjust the level of the third battery voltage V3 by controlling the duty ratio of the first switch Q1.

[0163] The second power conversion circuit 350a may convert the third battery voltage V3 between the seventh and eighth terminals P7 and P8 into the first battery voltage V1 and output it between the fifth and sixth terminals P5 and P6. In this case, the battery controller 140 may adjust the levels of the first battery voltage V1 and the third battery voltage V3 by controlling the duty ratio of the second switch Q2.

[0164] For example, the first battery rack 310 may include 12 first battery modules connected in series, and each first battery module may include 22 first battery cells connected in series. Each first battery cell may have a cell capacity of 94 Ah. The battery capacity of the first battery rack 310 may be 91.3 kWh. The first battery voltage V1 of the first battery rack 310 may be, for example, 818.4 V to 1095.6 V depending on the state of charge.

[0165] The second battery rack 320 includes 11 second battery modules connected in series, and each second battery module may include 44 second battery cells connected in series and parallel. Each second battery cell has a cell capacity of 150 Ah. The battery capacity of the second battery rack 320 is 267.2 kWh. The second battery voltage V2 of the second battery rack 320 is, for example, 750.2 V to 1004.3 V depending on the state of charge.

[0166] The battery module 340 may include 44 third battery cells connected in series and parallel. Each of the third battery cells may have a cell capacity of 150 Ah. The battery module 340 may have a battery capacity of 24.3 kWh. The third battery voltage V3 of the battery module 340 may be, for example, 68.2 V to 91.3 V depending on the state of charge. The third battery cells may be of the same type as the second battery cells. The battery module 340 may be composed of a plurality of battery modules connected in series and / or parallel.

[0167] The second converted voltage V4 of the first power conversion circuit 330a is 68.2V to 91.3V depending on the first battery voltage V1 and the second battery voltage V2. The first power conversion circuit 330a may output the second converted voltage V4 such that the ratio of the first converted voltage V3 to the second converted voltage V4 is 1:1. The boost ratio of the first power conversion circuit 330a is approximately 1:1, and may be adjusted by the battery controller 360 depending on the first battery current i1 and the second battery current i2. In this case, the first power conversion circuit 330a may have a power conversion capacity of approximately 15 kW.

[0168] The second power conversion circuit 350a may convert the first battery voltage V1 to a third battery voltage V3. The first power conversion circuit 330a has a buck ratio of approximately 12:1, and the buck ratio of the second power conversion circuit 350a may be adjusted by the battery controller 360 according to the third state of charge of the battery module 350. In this case, the second power conversion circuit 350a may have a power conversion capacity of approximately 550 W.

[0169] FIG. 8 illustrates another example circuit diagram of the battery pack illustrated in FIG.

[0170] 8, battery pack 300b is connected between first pack terminal 301 and second pack terminal 302 and includes a first battery rack 310 having a first battery voltage V1, a second battery rack 320 having a second battery voltage V2, a first power conversion circuit 330b having first through fourth terminals P1, P2, P3, and P4, a battery module 340 having a third battery voltage V3, and a second power conversion circuit 350b having fifth through eighth terminals P5, P6, P7, and P8. Although not shown in FIG. 5, battery pack 300b further includes a battery controller (360 in FIG. 6) that controls first power conversion circuit 330b and second power conversion circuit 350b. Battery pack 300b may further include a first current sensor (311 in FIG. 6) and a second current sensor (321 in FIG. 6).

[0171] The first power conversion circuit 330b is also a DC / DC converter. The first terminal P1 and the second terminal P2 are respectively connected to the positive and negative terminals of the battery module 340, the third terminal P3 is connected to the negative terminal of the second battery rack 320, and the fourth terminal P4 is connected to the second pack terminal 302.

[0172] The second power conversion circuit 350b is also an isolated DC / DC converter. The second power conversion circuit 350b is also a flyback converter. The fifth terminal P5 and the sixth terminal P6 are respectively connected to the positive and negative terminals of the first battery rack 310, and the seventh terminal P7 and the eighth terminal P8 are respectively connected to the positive and negative terminals of the battery module 340.

[0173] The first power conversion circuit 330b includes an inductor L between the first terminal P1 and a first intermediate node N1, a first switch Q1 between the first intermediate node N1 and a third terminal P3, and a second switch Q2 between the first intermediate node N1 and a second intermediate node N2. The second intermediate node N2 may be commonly connected to the second terminal P2 and the fourth terminal P4.

[0174] The first switch Q1 may include a first diode D1, and the second switch Q2 may include a second diode D2. For example, the first switch Q1 and the second switch Q2 may be insulated gate bipolar transistors (IGBTs) with the first diode D1 and the second diode D2 in the body diode configuration, respectively. In other examples, the first switch Q1 and the second switch Q2 may be bipolar junction transistors (BJTs), field effect transistors (FETs), or metal oxide semiconductor FETs (MOSFETs).

[0175] The first power conversion circuit 330b may further include a second capacitor C2 between the third terminal P3 and the fourth terminal P4. The first power conversion circuit 330b may further include a first capacitor C1 between the first terminal P1 and the second terminal P2. The first capacitor C1 may be omitted.

[0176] The first power conversion circuit 330b may convert the first converted voltage V3 between the first and second terminals P1 and P2 into a second converted voltage V4 and output it between the third and fourth terminals P3 and P4, or may convert the second converted voltage V4 between the third and fourth terminals P3 and P4 into the first converted voltage V3 and output it between the first and second terminals P1 and P2.

[0177] For example, when the second switch Q2 is turned on, current flows from the first terminal P1 to the second terminal P2 via the inductor L and the second switch Q2, and the energy stored in the first capacitor C1 and the battery module 340 is accumulated in the inductor L. When the second switch Q2 is turned off, the energy accumulated in the inductor L is transferred to the second capacitor C2 via the first diode D1. As a result, the first converted voltage V3 between the first and second terminals P1 and P2 is converted into the second converted voltage V4 between the third and fourth terminals P3 and P4. The level of the second converted voltage V4 is adjusted by the duty ratio of the second switch Q2. The battery controller 140 can adjust the level of the second converted voltage V4 by controlling the duty ratio of the second switch Q2.

[0178] The second power conversion circuit 350b includes an additive polarity transformer TR having a primary winding L1 coupled between a fifth terminal P5 and a sixth terminal P6 and a secondary winding L2 coupled between a seventh terminal P7 and an eighth terminal P8. The turns ratio between the primary winding L1 and the secondary winding L2 can be set according to a desired voltage conversion ratio of the second power conversion circuit 350b.

[0179] The second power conversion circuit 350b includes a third switch Q3 connected in series with the primary winding L1 between the fifth terminal P5 and the sixth terminal P6, and a fourth diode D4 connected in series with the secondary winding L2 between the seventh terminal P7 and the eighth terminal P8. The third switch Q3 may include the third diode D3. For example, the third switch Q3 may be a field-effect transistor (FET) having the third diode D3 in a body diode configuration. According to another example, the third switch Q3 may be another type of transistor.

[0180] The second power conversion circuit 350b may further include a third capacitor C3 between the fifth terminal P5 and the sixth terminal P6. The second power conversion circuit 350b may further include a fourth capacitor C4 between the seventh terminal P7 and the eighth terminal P8. The third capacitor C3 and / or the fourth capacitor C4 may be omitted.

[0181] The second power conversion circuit 350b may convert the first battery voltage V1 between the fifth and sixth terminals P5 and P6 into a third battery voltage V3 and output the third battery voltage V3 between the seventh and eighth terminals P7 and P8. In this case, the battery controller 140 may adjust the level of the third battery voltage V3 by controlling the duty ratio of the first switch Q1.

[0182] The second power conversion circuit 350b may convert the third battery voltage V3 between the seventh and eighth terminals P7 and P8 into the first battery voltage V1 and output it between the fifth and sixth terminals P5 and P6. In this case, the battery controller 140 may adjust the levels of the first battery voltage V1 and the third battery voltage V3 by controlling the duty ratio of the second switch Q2.

[0183] For example, the first battery rack 310 may include 12 first battery modules connected in series, and each first battery module may include 22 first battery cells connected in series. Each first battery cell may have a cell capacity of 94 Ah. The battery capacity of the first battery rack 310 may be 91.3 kWh. The first battery voltage V1 of the first battery rack 310 may be, for example, 818.4 V to 1095.6 V depending on the state of charge.

[0184] The second battery rack 320 includes 10 second battery modules connected in series, and each second battery module may include 44 second battery cells connected in series and parallel. Each second battery cell has a cell capacity of 150 Ah. The battery capacity of the second battery rack 320 is 242.9 kWh. The second battery voltage V2 of the second battery rack 320 is, for example, 682 V to 913 V depending on the state of charge.

[0185] The battery module 340 may include 44 third battery cells connected in series and parallel. Each of the third battery cells may have a cell capacity of 150 Ah. The battery module 340 may have a battery capacity of 24.3 kWh. The third battery voltage V3 of the battery module 340 may be, for example, 68.2 V to 91.3 V depending on the state of charge. The third battery cells may be of the same type as the second battery cells. The battery module 340 may be composed of a plurality of battery modules connected in series and / or parallel.

[0186] The second converted voltage V4 of the first power conversion circuit 330b is 136.4V to 182.6V depending on the first battery voltage V1 and the second battery voltage V2. The first power conversion circuit 330b may output the second converted voltage V4 such that the ratio of the first converted voltage V3 to the second converted voltage V4 is 1:2. The boost ratio of the first power conversion circuit 330b is approximately 1:2, and may be adjusted by the battery controller 360 depending on the first battery current i1 and the second battery current i2. In this case, the first power conversion circuit 330b may have a power conversion capacity of approximately 14 kW.

[0187] The second power conversion circuit 350b may convert the first battery voltage V1 to a third battery voltage V3. The first power conversion circuit 330b has a buck ratio of approximately 12:1, and the buck ratio of the second power conversion circuit 350b may be adjusted by the battery controller 360 according to the third state of charge of the battery module 350. In this case, the second power conversion circuit 350b may have a power conversion capacity of approximately 550 W.

[0188] The specific embodiments shown and described herein are illustrative examples and are not intended to limit the scope of the embodiments in any way. For convenience of explanation, descriptions of conventional electronic configurations, control systems, software, and other functional aspects of the systems may be omitted. Furthermore, wire connections or connecting members between illustrated components are illustrative of functional connections and / or physical or circuit connections, and an actual device may be embodied by various alternative or additional functional connections, physical connections, or circuit connections.

[0189] When describing the embodiments (particularly the claims), the use of the term "said" and similar indicators applies to both the singular and the plural. Furthermore, when a range is described in the embodiments, it includes the invention to which each individual value within that range is applied (unless otherwise specified), and is equivalent to describing each individual value comprising that range in the detailed description of the invention. Unless otherwise specified, the steps constituting the method according to the present invention may be performed in any suitable order. The order in which the steps are described is not necessarily intended to limit the present invention.

[0190] The use of all examples or exemplary terms (such as, for example, etc.) in the present invention is merely for the purpose of describing the present invention in detail, and the scope of the embodiments is not limited by the examples or exemplary terms unless limited by the scope of the claims. In addition, those skilled in the art will recognize that various modifications, combinations, and variations can be made depending on design conditions and factors within the scope of the appended claims or their equivalents.

[0191] Although exemplary embodiments are presented herein, and specific terms are used, they should be construed as generic and descriptive rather than for purposes of limitation. In some instances, as would be apparent to one of ordinary skill in the art at the time of filing of this application, features and / or components described in connection with a particular embodiment may be used alone or in combination with features and / or components described in connection with other embodiments, unless specifically stated otherwise. Therefore, the scope of the present invention should not be limited to the above-described embodiments, and all scopes equivalent to or modified equivalently from the following claims are deemed to fall within the scope of the present invention. [Explanation of symbols]

[0192] 100 Battery Pack 101 1st pack terminal 102 2nd pack terminal 110 Battery Rack No. 1 120 Second Battery Rack 130 Power Conversion Circuit 140 Battery Controller P1, P2, P3, P4 1st to 4th terminals

Claims

1. a first battery rack connected between the first pack terminal and the second pack terminal; a first power conversion circuit having a first terminal, a second terminal, a third terminal, and a fourth terminal connected to the second pack terminal, and bidirectionally converting a first converted voltage between the first terminal and the second terminal and a second converted voltage between the third terminal and the fourth terminal; a second battery rack connected between the first pack terminal and the third terminal of the first power conversion circuit; a battery controller that controls the first power conversion circuit to adjust the level of the second converted voltage.

2. the second battery rack is connected between the first terminal and the second terminal of the first power conversion circuit; the first terminal of the first power conversion circuit is coupled to the first pack terminal; The battery pack according to claim 1 , wherein the second terminal and the third terminal of the first power conversion circuit are connected to each other.

3. The first power conversion circuit a first switch between the first terminal and a first intermediate node; a second switch between the first intermediate node and the fourth terminal; The battery pack of claim 2 , further comprising: an inductor between a second intermediate node commonly coupled to the second terminal and the third terminal and the first intermediate node.

4. The first power conversion circuit an additive polarity transformer having a primary winding connected between the first terminal and the second terminal and a secondary winding connected between the third terminal and the fourth terminal; a first switch connected in series with the primary winding between the first terminal and the second terminal; 3. The battery pack of claim 2, further comprising: a second switch coupled in series with the secondary winding between the third terminal and the fourth terminal.

5. the first battery rack is connected between the first terminal and the second terminal of the first power conversion circuit; the first terminal of the first power conversion circuit is coupled to the first pack terminal; The battery pack according to claim 1 , wherein the second terminal and the fourth terminal of the first power conversion circuit are commonly connected to the second pack terminal.

6. The first power conversion circuit a first switch between the first terminal and a first intermediate node; an inductor between the first intermediate node and the third terminal; The battery pack of claim 5 , further comprising: a second switch between a second intermediate node and the first intermediate node, the second switch being commonly coupled to the second terminal and the fourth terminal.

7. a battery module connected between the first terminal and the second terminal of the first power conversion circuit; 2. The battery pack of claim 1, further comprising: a second power conversion circuit having a fifth terminal connected to the first pack terminal and a sixth terminal, a seventh terminal, and an eighth terminal connected to the second pack terminal, the second power conversion circuit bidirectionally converting a first battery voltage of the first battery rack connected between the fifth terminal and the sixth terminal and a third battery voltage of the battery module connected between the seventh terminal and the eighth terminal.

8. The first power conversion circuit a first switch between the first terminal and a first intermediate node; a second switch between the first intermediate node and the fourth terminal; The battery pack of claim 7 , further comprising: an inductor between a second intermediate node and the first intermediate node, the inductor being commonly coupled to the second terminal and the third terminal.

9. The second power conversion circuit an additive polarity transformer having a primary winding connected between the fifth terminal and the sixth terminal and a secondary winding connected between the seventh terminal and the eighth terminal; a third switch connected in series with the primary winding between the fifth terminal and the sixth terminal; 8. The battery pack of claim 7, further comprising: a fourth switch coupled in series with the secondary winding between the seventh terminal and the eighth terminal.

10. The first power conversion circuit an inductor between the first terminal and a first intermediate node; a first switch between the first intermediate node and the third terminal; The battery pack of claim 7 , further comprising: a second switch between the first intermediate node and a second intermediate node commonly connected to the second terminal and the fourth terminal.

11. The second power conversion circuit an additive polarity transformer having a primary winding connected between the fifth terminal and the sixth terminal and a secondary winding connected between the seventh terminal and the eighth terminal; a third switch connected in series with the primary winding between the fifth terminal and the sixth terminal; 8. The battery pack according to claim 7, further comprising: a diode connected in series with the secondary winding in a reverse direction between the seventh terminal and the eighth terminal.

12. The battery pack according to claim 7 , wherein the battery controller senses a third state of charge of the battery module and controls the second power conversion circuit based on the third state of charge.

13. 2. The battery pack of claim 1, wherein the battery controller senses a first state of charge of the first battery rack and a second state of charge of the second battery rack, and adjusts the level of the second conversion voltage based on a difference between the first state of charge and the second state of charge.

14. The battery controller When the second state of charge is lower than the first state of charge in a charging mode, the level of the second converted voltage is decreased to increase the charging current of the second battery rack; 14. The battery pack of claim 13, wherein when the second state of charge is lower than the first state of charge in a discharge mode, the level of the second converted voltage is reduced to reduce a discharge current of the second battery rack.

15. 2. The battery pack of claim 1, wherein the battery controller senses a first battery current capacity of the first battery rack and a second battery current capacity of the second battery rack, senses a first battery current flowing through the first battery rack and a second battery current flowing through the second battery rack, and adjusts a level of the second conversion voltage so that a ratio of the second battery current to the first battery current is equal to a ratio of the second battery current capacity to the first battery current capacity.

16. a first battery rack coupled between the first pack terminal and the second pack terminal and having a first battery voltage; a first power conversion circuit including first to fourth terminals and a capacitor between the third terminal and the fourth terminal, and bidirectionally converting a first converted voltage between the first terminal and the second terminal and a second converted voltage across the capacitor; a second battery rack connected between the first pack terminal and the third terminal of the first power conversion circuit, the second battery rack having a second battery voltage; a battery controller that controls the first power conversion circuit to adjust the level of the second conversion voltage of the first power conversion circuit; The second battery rack and the capacitor of the first power conversion circuit are connected in series between the first pack terminal and the second pack terminal.

17. The battery pack of claim 16, wherein the second battery rack is connected between the first terminal and the second terminal of the first power conversion circuit.

18. The battery pack of claim 16, wherein the first battery rack is connected between the first terminal and the second terminal of the first power conversion circuit.

19. a battery module having a third battery voltage, the battery module being connected between the first terminal and the second terminal of the first power conversion circuit; 17. The battery pack of claim 16, further comprising: a second power conversion circuit having a fifth terminal coupled to the first pack terminal, a sixth terminal coupled to the second pack terminal, a seventh terminal coupled to the first terminal, and an eighth terminal coupled to the second terminal, the second power conversion circuit bidirectionally converting the first battery voltage between the fifth and sixth terminals and the third battery voltage between the seventh and eighth terminals.

20. 17. The battery pack of claim 16, wherein the battery controller senses a first battery current flowing through the first battery rack and a second battery current flowing through the second battery rack, and adjusts a level of the second conversion voltage based on a ratio of the second battery current to the first battery current and a ratio of a second battery capacity of the second battery rack to a first battery capacity of the first battery rack.

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