Equalization circuit and method

Abstract

An equalization circuit (200) and method for a power pack. A power pack consisting of a plurality of power supplies connected in series is split into a plurality of sub-power packs (201), and each sub-power pack comprises at least one power supply. Then, a plurality of equalization units (202) and energy storage elements are provided; each equalization unit and energy storage element are connected to a corresponding sub-power pack; the energy transmission path between the corresponding sub-power pack and energy storage element is changed by means of the equalization unit, and energy is transferred between the plurality of sub-power packs by means of the charging and discharging processes of the plurality of energy storage elements, so that a sub-power pack having a high voltage charges a sub-power pack having a low voltage, thereby achieving energy balance among the plurality of sub-power packs. Compared with a conventional equalization circuit, the measurement and equalization circuit can be split to be implemented in each sub-power pack, thereby facilitating repair and maintenance. In addition, splitting a high-voltage series power pack into a plurality of sub-power packs is also beneficial to wiring design and EMC design.

Description

Equalization circuit and method

[0001] This application claims priority to a Chinese invention application filed on September 11, 2023, with application number 202311167943.9 and titled “Equalizing Circuit and Method,” and incorporates the entire specification, claims, drawings, and abstract of the aforementioned Chinese invention application into this application by reference. Technical Field

[0002] The present invention relates to the technical field of power supply balancing, and more particularly to a balancing circuit and method. Background Art

[0003] With the development of the new energy industry, battery systems are gaining wider application in automotive and energy storage applications. To increase battery capacity, the number of batteries connected in series and parallel continues to increase. However, cell voltage inconsistency in a battery system can severely impact both capacity and the lifespan of the battery pack. Due to the "barrel effect," battery packs significantly underperform their individual cell performance in terms of cycle life and capacity utilization. As battery packs are recycled, cell inconsistency exacerbates, further deteriorating the packing characteristics of lithium-ion batteries. Overcharge and over-discharge of a few cells can occur, leading to significant degradation of battery pack performance. In extreme cases, combustion, explosion, and other serious accidents can occur, significantly hindering the widespread application of lithium-ion batteries.

[0004] Balancing control of the battery pack involves timely balancing the energy of the cells within the pack during cycling, either through energy consumption or transfer. This reduces the probability of overcharge or over-discharge, and eliminates the adverse effects of varying depths of discharge on the battery pack. Specifically, when a cell's voltage is too low, energy from the connected power source is transferred to that cell. Conversely, when the cell's voltage is too high, energy from the battery's excessively high voltage is transferred to the power source. This ensures real-time balancing during charging and discharging, unleashing the full potential of each cell. This ensures that each cell is fully charged and discharged to its lowest possible level, maximizing the capacity of each cell in the pack. This improves the overall energy utilization of the battery pack and extends the battery's cycle life.

[0005] However, traditional balancing circuits typically require a large number of electronic components, such as capacitors, resistors, and switches, resulting in relatively high costs. This limits the application scope of battery balancing technology. Therefore, finding a low-cost battery balancing circuit technology has become a hot topic in the battery field. Summary of the Invention

[0006] In view of the above problems, the purpose of the present invention is to provide a balancing circuit and method, which can decompose the power supply group into multiple sub-power supply groups, and achieve voltage balancing of the power supply group by transferring energy between multiple sub-power supply groups, which can improve the problems of the existing technology of the series power supply group balancing topology with many balancing devices and high cost.

[0007] According to one aspect of the present invention, there is provided a balancing circuit for a power supply group, wherein the power supply group includes a plurality of sub-power supply groups connected in series, each of the sub-power supply group includes at least one power supply, and the balancing circuit includes: a plurality of balancing units, each balancing unit being connected to a corresponding one of the plurality of sub-power supply groups; and a plurality of energy storage elements, the first ends of the plurality of energy storage elements being respectively connected to the corresponding balancing units, and the second ends of the plurality of energy storage elements being connected to a common node, wherein each of the balancing units includes: a first switch connected between the positive end of the corresponding sub-power supply group and the first end of the energy storage element; and a second switch connected between the negative end of the corresponding sub-power supply group and the first end of the energy storage element, wherein each balancing unit is configured to change the energy transmission path between the corresponding sub-power supply group and the energy storage element by alternately turning on the first switch and the second switch, so as to transfer energy between the plurality of sub-power supply groups using the charging and discharging process of the plurality of energy storage elements.

[0008] Optionally, the multiple balancing units include a first balancing unit and multiple second balancing units, wherein the first balancing unit is configured to turn on the first switch or the second switch according to the start signal, and the second balancing unit is configured to turn on the first switch or the second switch according to the voltage change on the energy storage element connected thereto.

[0009] Optionally, the multiple second balancing units are configured to turn on the first switch and turn off the second switch if a positive voltage change is detected on the energy storage element connected thereto; and to turn on the second switch and turn off the first switch if a negative voltage change is detected on the energy storage element connected thereto.

[0010] Optionally, each of the second balancing units further includes: a voltage detection module configured to turn on the first switch or the second switch according to a voltage change on the corresponding energy storage element.

[0011] Optionally, each of the balancing units further includes: a current zero-crossing detection module configured to obtain a current polarity of a conductive switch in the balancing unit, and switch the conductive switch to off when the current crosses zero according to the current polarity.

[0012] Optionally, each of the energy storage elements includes: at least one flying capacitor; or a structure in which at least one flying capacitor and an inductor are connected in series.

[0013] According to another aspect of the present invention, a balancing method for a power supply group is provided, comprising: splitting the power supply group into multiple sub-power supply groups, each sub-power supply group including at least one power supply; providing multiple balancing units, each balancing unit being connected to a corresponding one of the multiple sub-power supply groups; providing multiple energy storage elements, the first ends of the multiple energy storage elements being respectively connected to the corresponding balancing units, and the second ends of the multiple energy storage elements being connected to a common node; and providing in each of the balancing units a first switch connected between the positive end of the corresponding sub-power supply group and the first end of the corresponding energy storage element, and a second switch connected between the negative end of the corresponding sub-power supply group and the first end of the corresponding energy storage element; and changing the energy transmission path between the corresponding sub-power supply group and the energy storage element by alternately turning on the first switch and the second switch, so as to transfer energy between the multiple sub-power supply groups through the charging and discharging process of the multiple energy storage elements.

[0014] Optionally, the step of using the balancing unit to change the energy transmission path between the corresponding sub-power group and the energy storage element also includes: selecting a balancing unit from a plurality of balancing units as a first balancing unit, and using the remaining balancing units from the plurality of balancing units as second balancing units; providing a start signal to the first balancing unit to control the switch switching in the first balancing unit; transmitting the step wave of the DC voltage of the sub-power group corresponding to the first balancing unit to the energy storage elements corresponding to the plurality of second balancing units through the common node; and controlling the switch switching in the second balancing unit according to the voltage change on the energy storage element connected to each second balancing unit.

[0015] Optionally, the step of controlling the switch switching in each second balancing unit according to the voltage change on the energy storage element connected to the second balancing unit includes: if a positive voltage change is detected on the energy storage element, turning on the first switch in the corresponding second balancing unit and turning off the second switch in the corresponding second balancing unit; if a negative voltage change is detected on the energy storage element, turning on the second switch in the corresponding second balancing unit and turning off the first switch in the corresponding second balancing unit.

[0016] Optionally, the method further includes: acquiring a current polarity of a switch that is turned on in the balancing unit, and switching the switch that is turned on to off when the current passes through zero according to the current polarity.

[0017] Optionally, each of the energy storage elements includes: at least one flying capacitor; or a structure in which at least one flying capacitor and an inductor are connected in series.

[0018] In summary, the balancing circuit and method provided in the embodiment of the present invention splits a power supply group consisting of multiple power supplies connected in series into multiple sub-power supply groups, each sub-power supply group including at least one power supply. Then, multiple balancing units and energy storage elements are provided, each balancing unit and energy storage element is connected to the corresponding sub-power supply group, and the energy transmission path between the corresponding sub-power supply group and the energy storage element is changed by the balancing unit, and the charging and discharging process of multiple energy storage elements is used to transfer energy between the multiple sub-power supply groups, so that the sub-power supply group with higher voltage is charged by the sub-power supply group with lower voltage, thereby achieving energy balance between the multiple sub-power supply groups. Compared with the traditional balancing circuit, the balancing circuit provided by the present invention can split the measurement and balancing circuit into each sub-power supply group for implementation, which is convenient for repair and maintenance. In addition, decomposing the high-voltage series power supply group into multiple sub-power supply groups is also beneficial to wiring design and EMC design. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The above and other objects, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

[0020] FIG1 is a schematic structural diagram of a series battery pack balancing system according to the prior art in a specific application.

[0021] FIG2 is a diagram showing the working principle of a series battery pack balancing system provided according to the prior art.

[0022] FIG3 is a schematic structural diagram of an equalization circuit according to a first embodiment of the present invention.

[0023] FIG4 is a schematic structural diagram of a minimum balancing unit in the balancing circuit in FIG3 .

[0024] FIG5 is a schematic structural diagram of another equalization circuit according to a second embodiment of the present invention.

[0025] 6a and 6b are respectively a schematic diagram and a waveform diagram of the resonant charge transfer principle of the equalization circuit according to the second embodiment of the present invention.

[0026] FIG. 7 is a schematic structural diagram of a minimum balancing unit in the balancing circuit in FIG. 5 . DETAILED DESCRIPTION

[0027] Various embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. In each of the accompanying drawings, identical elements are represented by identical or similar reference numerals. For clarity, the various parts in the accompanying drawings are not drawn to scale. In addition, some well-known parts may not be shown.

[0028] It should be understood that in the following description, a "circuit" refers to a conductive loop formed by at least one element or subcircuit connected electrically or electromagnetically. When an element or circuit is said to be "connected to" another element or an element / circuit is said to be "connected" between two nodes, it can be directly coupled or connected to the other element or there can be intermediate elements. The connection between the elements can be physical, logical, or a combination thereof. Conversely, when an element is said to be "directly coupled to" or "directly connected to" another element, it means that there are no intermediate elements between the two elements.

[0029] The present invention may be embodied in various forms, some examples of which are described below.

[0030] In order to improve the inconsistency problem of battery packs in the existing technology and improve the overall performance of the battery pack, it is necessary to adopt balancing control. The current lithium-ion battery pack balancing circuit is mainly divided into passive balancing circuits and active balancing circuits according to the energy consumption of the circuit during the balancing process. The passive balancing circuit uses energy-consuming components such as resistors to consume the extra energy in the high-voltage battery in the form of heat energy to achieve battery voltage balancing within the battery pack. Although the passive balancing circuit has the advantages of low cost and small size, it also has limitations such as serious energy waste and difficulty in heat dissipation. The active balancing circuit mainly uses non-energy components such as capacitors, inductors, and transformers as intermediate energy transmission elements to transfer energy from the high-voltage battery to the low-voltage battery to achieve voltage balancing between batteries. It has the advantages of high efficiency and strong balancing ability.

[0031] Based on the balancing function, it can be divided into charge balancing, discharge balancing, and dynamic balancing. Charge balancing refers to balancing during the charging process. It generally begins when the battery cell voltage reaches the set value, reducing the charging current to prevent overcharging. Discharge balancing refers to balancing during the discharge process. It replenishes energy to battery cells with low residual energy to prevent overdischarge. Dynamic balancing combines the advantages of charge and discharge balancing and refers to balancing the battery pack throughout the entire charge and discharge process. Based on the different balancing devices, it can be divided into switched capacitor type, switched inductor type, transformer type, DC-DC converter type and other topologies.

[0032] FIG1 is a schematic diagram of the structure of a series battery pack balancing circuit according to the prior art in a specific application. As shown in FIG1 , the series battery pack balancing circuit 100 provided by the prior art includes a balancing switch array 102, a controller 103, a voltage sampling module 104, and an energy storage module 105. The voltage sampling module 104 is configured to collect the voltage value of each single cell in the battery pack 101 and provide the collected voltage value to the controller 103. The controller 103 compares the voltage value of each single cell and, based on the comparison result, controls the balancing switch array 102 to connect the single cell with the maximum voltage value to the energy storage module 105. When the charge in the single cell with the maximum voltage value and the charge in the energy storage module 105 reach equilibrium, the balancing switch array 102 is controlled to disconnect the electrical connection between the single cell with the maximum voltage value and the energy storage module 105. At the same time, the balancing switch array 102 is controlled to connect the single cell with the minimum voltage value to the energy storage module 105. When the power in the single cell with the minimum voltage value and the energy storage module 105 reaches equilibrium, the isolation switch array 102 is controlled to disconnect the electrical connection between the single cell with the minimum voltage value and the energy storage module 105, and the voltage value of each single cell collected by the voltage sampling module 104 is compared again until the power in all single cells in the series battery group 101 reaches equilibrium.

[0033] Figure 2 illustrates the operating principle of a series battery pack balancing circuit according to prior art. As shown in Figure 2, a series battery pack 101 comprises battery cells BT1, BT2, BT3, BTn-1, and BTn connected in series. The resulting output differential voltage points are, in order, BIT0, BIT1, BIT2, BIT3, BITn-1, and BIT1n. The voltages across voltage nodes BIT0 and BIT1 represent the voltage of battery cell BT1; the voltages across voltage nodes BIT1 and BIT2 represent the voltage of battery cell BT2; and the voltages across voltage nodes BITn-1 and BITn represent the voltage of battery cell BTn. The connection nodes between the series battery pack 101 and the balancing switch array 102 are BIT0, BIT1, BIT2, BIT3, BITn-1, and BIT1n. Furthermore, the energy storage module 105 is a capacitor Cfly, and the balancing switch array 102 includes multiple balancing switches S1, S2, S3···Sn-1, Sn, wherein the first voltage ends of the balancing switches S1, S2, S3···Sn-1, Sn are electrically connected to the voltage nodes BIT0, BIT1, BIT2, BIT3···BITn-1, BIT1n in the series battery group 101, respectively, and the second voltage ends of the balancing switches S1, S2, S3···Sn-1, Sn are electrically connected to the capacitor Cfly, wherein the second voltage ends of the balancing switches S1, S3, S5···Sn-1 are electrically connected to the second end of the capacitor Cfly, and the second voltage ends of the balancing switches S2, S4, S6···Sn are electrically connected to the first end of the capacitor Cfly.

[0034] Traditional switched-capacitor balancing circuits require balancing for each battery cell, requiring a large number of electronic components such as capacitors, resistors, and switches. This results in large size, high cost, and high power consumption. Furthermore, when a balancing circuit manages a large number of cells, balancing efficiency per unit time decreases significantly. The corresponding switching transistors have high withstand voltage requirements, resulting in a limited number of available solutions within a limited product size, limiting the application of balancing circuits.

[0035] Based on this, the embodiment of the present invention provides a balancing circuit and method, which splits the high-voltage series battery pack into a maximum voltage of 60V based on the structural, electrical safety requirements, and the voltage adaptability requirements of different integrated circuit processes. DC The following multiple sub-battery groups, and the measurement and balancing circuits are split into sub-group strings for easy repair and maintenance, and there is a wider range of semiconductor process options. DC The corresponding 36V ACThe DC voltage, which is generally recognized as the upper limit of the safe voltage, is also the withstand voltage value that can be covered by common integrated circuit processes. In addition, decomposing a high-voltage series battery pack into multiple sub-strings also facilitates wiring design and EMC design. When the measurement and balancing circuits are split into multiple sub-battery packs, it is necessary to ensure voltage balance between the multiple sub-battery packs. Therefore, the balancing circuit and method of the present invention further provide a method for charge transfer between multiple sub-battery packs to improve the existing problems of high power loss, multiple balancing devices, low balancing efficiency, and high cost in the series battery pack balancing topology.

[0036] Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

[0037] FIG3 is a schematic diagram of the structure of an equalizing circuit according to the first embodiment of the present invention, and FIG4 is a schematic diagram of the structure of a minimum equalizing unit in the equalizing circuit in FIG3 .

[0038] 3 , the balancing circuit 200 of this embodiment includes or is connected to a plurality of sub-power groups 201, each of which includes at least one power source. It should be noted that the term "power source" herein may refer to substantially any type of component or circuit location that can generate a voltage at both ends. In an exemplary embodiment, a battery cell may be used as a power source. For example, the battery cell includes a rechargeable battery such as a lithium-ion battery, a nickel-cadmium battery, a nickel metal cyanide battery, a lead-acid battery, a nickel-zinc battery, or other rechargeable battery. In another exemplary embodiment, a single or multiple capacitor circuits, diode circuits, transistor circuits, etc. may also be used as a power source. Of course, the power source may also include a circuit combination such as a resistor / capacitor network or a semiconductor network that can generate a voltage and can be balanced according to the systems and methods described herein.

[0039] Furthermore, when there are multiple power sources in the sub-power group 201, the multiple power sources are connected in series. For example, in a specific embodiment shown in Figure 3, each sub-power group 201 includes multiple single battery cells BAT1~BAT3 with rated voltages connected in series. In addition, any other type of power source, such as supercapacitors, fuel cells, and solar cells, can also be used in each sub-power group 201. It should also be noted that this embodiment does not limit the number of power sources in the sub-power group 201, and any number of power sources can be used here. In one embodiment, multiple sub-power groups 201 can each include one power source. In another embodiment, multiple sub-power groups 201 can include multiple power sources of the same number. For ease of explanation, each sub-power group 201 in Figure 3 includes battery cells BAT1~BAT3 connected sequentially from bottom to top.

[0040] Similarly, this embodiment does not limit the number of sub-power groups 201 in the series power group, and any number of sub-power groups can be used. In a specific embodiment shown in Figure 3, the series power group includes four sub-power groups 201a-201d connected sequentially from bottom to top.

[0041] As known to those skilled in the art, each power source in sub-power group 201 (i.e., battery cells BAT1-BAT3) includes a positive terminal (indicated by "+") and a negative terminal (indicated by "-"). Multiple battery cells BAT are electrically connected in series. Connecting multiple battery cells BAT in series means that the battery cells BAT are arranged sequentially, with the negative terminal of the preceding battery cell being electrically connected to the positive terminal of the succeeding battery cell. That is, the positive terminal of battery cell BAT1 is electrically connected to the negative terminal of battery cell BAT2, the positive terminal of battery cell BAT2 is electrically connected to the negative terminal of battery cell BAT3, and so on. Typically, the negative terminal of the first battery cell BAT1 serves as the negative terminal 212 of sub-power group 201a, and the positive terminal 413 of the last battery cell BAT3 serves as the positive terminal 211 of sub-power group 201a, providing the DC voltage potential of sub-power group 201a. In addition, since the sub-power groups 201a-201d are connected in series, the positive terminal of the last sub-power group 201d is used to provide the total DC voltage potential of the series-connected power groups (or also called series-connected battery groups).

[0042] The balancing circuit 200 includes multiple balancing units 202 and multiple energy storage elements. Each balancing unit 202 is used to connect to a corresponding one of the multiple sub-power groups 201, and each energy storage element is used to store or release energy. For example, each energy storage element includes at least one fly capacitor Cfly. Figure 3 uses the example of an energy storage element including one fly capacitor Cfly for illustration. The first ends of the multiple fly capacitors Cfly are respectively connected to the corresponding balancing unit 202, and the second ends of the multiple fly capacitors Cfly are connected to a common node 224. The balancing unit 202 is used to transfer energy between the multiple sub-power groups 201 by changing the energy transmission path between the corresponding sub-power group 201 and the fly capacitor Cfly, so as to utilize the charging and discharging process of the multiple fly capacitors Cfly to transfer energy between the multiple sub-power groups 201, thereby allowing the sub-power group with a higher voltage to charge the sub-power group with a lower voltage, thereby achieving energy balancing between the multiple sub-power groups 201.

[0043] Furthermore, in this embodiment, the number of balancing units 202 and flying capacitors Cfly equals the number of sub-power groups in the series-connected power group. For example, in the illustrated embodiment, since there are four sub-power groups 201 electrically connected in series, four balancing units 202 and four flying capacitors Cfly are used. For clarity, the four balancing switches 202 are sequentially labeled 202a through 202d, and the four flying capacitors Cfly are sequentially labeled Cfly1 through Cfly4.

[0044] The first connection terminal 221 of each balancing unit 202 can be electrically connected to the positive terminal of the corresponding sub-power group 201, the second connection terminal 222 of each balancing unit 202 can be electrically connected to the negative terminal of the corresponding sub-power group 201, and the third connection terminal 223 of each balancing unit 202 can be electrically connected to the first terminal of the corresponding flying capacitor Cfly. For example, the first connection terminal 221 of balancing unit 202a is electrically connected to the positive terminal 211 of sub-power group 201a, the second connection terminal 222 of balancing unit 202a is electrically connected to the negative terminal 212 of sub-power group 201a, and the third connection terminal 223 of balancing unit 202a is electrically connected to the first terminal of flying capacitor Cfly1, and so on.

[0045] Furthermore, each balancing unit 202 includes switches S1 and S2. The first end of switch S1 serves as the first connection terminal 221 of the balancing unit 202, the first end of switch S2 serves as the second connection terminal 222 of the balancing unit 202, and the second ends of switches S1 and S2 serve as the third connection terminal 223 of the balancing unit 202. For example, balancing unit 202a includes switches S1a and S2a. The first end of switch S1a is electrically connected to the positive terminal 211 of the corresponding sub-power group 201a, the first end of switch S2a is electrically connected to the negative terminal 212 of the sub-power group 201a, and the second ends of switches S1a and S2a are connected and electrically connected to the first end of the fly capacitor Cfly1. In some embodiments, switches S1 and S2 can be implemented as transistors (e.g., metal oxide semiconductor (MOS) transistors), relays, other electrically controllable switches, or combinations thereof. Among them, the switch S1 is configured to selectively connect the positive terminal of the corresponding sub-power group 201 to the first terminal of the corresponding fly capacitor Cfly, and the switch S2 is configured to selectively connect the negative terminal of the corresponding sub-power group 201 to the first terminal of the corresponding fly capacitor Cfly. During the balancing process between the sub-power groups, the energy transmission path between the corresponding sub-power group 201 and the fly capacitor Cfly can be changed by alternating conduction of the switches S1 and S2.

[0046] Furthermore, in this embodiment, the switching of the multiple balancing units 202 is achieved through a combination of passive switching and active control. During the balancing process, only some of the balancing units 202 need to be controlled for switching; the remaining balancing units 202 can automatically switch, eliminating the need for coordinated control of a large number of switches at the system level. This simplifies the control approach and facilitates wiring design. For example, in the following description, the balancing unit 202 that requires external signal control during the balancing process is referred to as the first balancing unit (generally, there is one first balancing unit; in practice, the physical location of the first balancing unit can be a location that is more easily accessible to external control). The balancing unit 202 that does not require external signal control during the balancing process is referred to as the second balancing unit.

[0047] The following example uses balancing unit 202a as the first balancing unit and balancing units 202b-202d as the second balancing unit for further explanation. When the balancing function between sub-power groups is enabled, an external control unit provides a start signal to a driver (not shown) of balancing unit 202a. This driver controls switches S1a and S2a in balancing unit 202a to conduct, alternately connecting the first end of flying capacitor Cfly1 to the positive and negative terminals of sub-power group 201a. Flying capacitor Cfly1 transmits a DC voltage step wave with an amplitude corresponding to sub-power group 201a through the common node 224 of the flying capacitors to the remaining sub-power groups 201b-201d. The balancing units 202b-202d corresponding to the remaining sub-power supply groups 201b-201d respectively determine whether to connect the first end of their corresponding fly capacitors Cfly2-Cfly4 to the positive or negative terminal of the corresponding sub-power supply group 201b-201d based on the voltage change trends on their connected fly capacitors Cfly2-Cfly4. Taking balancing unit 202b as an example, if balancing unit 202b detects a positive voltage change on fly capacitor Cfly2, it controls switch S1b to conduct, connecting the first end of fly capacitor Cfly2 to the positive terminal of sub-power supply group 201b. If balancing unit 202b detects a negative voltage change on fly capacitor Cfly, it controls switch S2b to conduct, connecting the first end of fly capacitor Cfly2 to the negative terminal of sub-power supply group 201b. The voltage change trend on the flying capacitor may refer to the direction of change in the value of the voltage signal over time. For example, a positive voltage change refers to a change in the value of the voltage signal increasing in a positive direction over time, which indicates that the waveform or amplitude of the voltage signal moves upward on the time axis. A negative voltage change refers to a change in the value of the voltage signal decreasing in a negative direction over time, which indicates that the waveform or amplitude of the voltage signal moves downward on the time axis.

[0048] In a further embodiment, as shown in FIG4 , each balancing unit 202 includes a voltage detection module 225 . When the balancing unit 202 is used as the second balancing unit described above, the voltage detection module 225 is configured to obtain a voltage change on the corresponding flying capacitor Cfly and turn on the switch S1 or S2 in the balancing unit 202 according to the voltage change.

[0049] Through the above process, each sub-power group 201 chops its own DC voltage and connects it together through the fly capacitor Cfly connected to it. If the voltage of a sub-power group itself is too high, it will output energy to the sub-power group with a lower voltage; if the voltage of a sub-power group itself is too low, it will obtain energy from the remaining sub-power groups, ultimately realizing energy transfer between multiple sub-power groups 201.

[0050] Taking adjacent sub-power groups 201a and 201b as an example, when switches S2a and S2b in balancing units 202a and 202b are turned on, the series connection of flying capacitors Cfly1 and Cfly2 is connected in parallel with sub-power group 201a. When switches S1a and S1b in balancing units 202a and 202b are turned on, the series connection of flying capacitors Cfly1 and Cfly2 is connected in parallel with sub-power group 201b. During the process of connecting flying capacitors Cfly1 and Cfly2 to the two sub-power groups 201a and 201b, respectively, energy from the sub-power group with a higher voltage can be transferred to the sub-power group with a lower voltage. It should be noted that the alternation in this embodiment occurs between all adjacent sub-power groups, and the same voltage swing occurs on the capacitors connected together across all flying capacitors. Therefore, energy transfer between any two sub-power groups is accomplished through the same number of flying capacitors, regardless of the sub-power group's physical location within the entire power group. Therefore, energy transfer in this embodiment is not limited to two adjacent sub-power groups.

[0051] In a further embodiment, the balancing circuit 200 of the present invention further includes a controller configured to execute the balancing strategy and generate the start signal when the voltage difference between the multiple sub-power groups 201 is greater than a set value. For example, the controller can be a general-purpose central processing unit (CPU), a general-purpose processor, a digital signal processing unit (DSP), an application-specific integrated circuit (ASIC), a field programmable gate array (FPGA), or other programmable logic devices, transistor logic devices, hardware components, or any combination thereof. It can implement or execute the various exemplary logic blocks, modules, and circuits described in conjunction with the disclosure of this application. The aforementioned processors can also be a combination that implements computing functions, such as a combination of one or more microprocessors, a combination of a DSP and a microprocessor, and so on. The controller can be independent of the balancing circuit 200 or integrated into other units, without specific limitation herein.

[0052] In this embodiment, the switches S1 and S2 in each balancing unit 202 only need to withstand the voltage on its corresponding sub-power group. Therefore, by keeping the voltage of each sub-power group below the safe voltage, the switches S1 and S2 can be manufactured using a withstand voltage value covered by conventional semiconductor processes, without the need to use switches with higher withstand voltage values. This allows the balancing design of higher voltage power groups to be achieved at a lower cost.

[0053] Furthermore, the maximum voltage that the fly capacitor Cfly in this embodiment can withstand is related to the voltage at the common node 224, which may be close to the total voltage of the entire series power supply group. When the total voltage of the series power supply group is too high, multiple fly capacitors can be divided into several common nodes for connection, so that each fly capacitor can withstand a very low voltage, without using a fly capacitor with a larger area.

[0054] Furthermore, the energy transfer capability of the balancing circuit 200 in this embodiment is related to the voltage difference across the sub-power groups 201. When the voltage difference across the sub-power groups 201 is large, the balancing circuit 200 can transfer more energy during each alternating cycle. However, when the voltage difference across the sub-power groups 201 is small or even non-existent, the balancing circuit 200 cannot effectively transfer energy during each alternating cycle. Furthermore, the energy transfer efficiency of the balancing circuit 200 is related to the ratio of the voltage drop across the path resistance to the sub-power group voltage during the transfer process, as well as switching losses. As the voltage difference across the sub-power groups decreases, the proportion of switching losses in each alternating cycle increases, which in turn reduces the energy transfer efficiency of the balancing circuit. As a result, a certain voltage difference still exists between the different sub-power groups at the end of the balancing operation, resulting in unsatisfactory balancing results.

[0055] Figure 5 is a schematic diagram of the structure of another balancing circuit according to a second embodiment of the present invention. As shown in Figure 5 , in a further embodiment, balancing circuit 300 differs from balancing circuit 200 in that the multiple energy storage elements in balancing circuit 300 each include at least one flying capacitor Cfly and an inductor Lx. The at least one flying capacitor Cfly and the inductor Lx are connected in series between the third connection terminal of the corresponding balancing unit 302 and a common node 324. By introducing an LC resonant structure into the energy storage element and switching on switches S1 and S2 in balancing unit 302 according to a half-resonant cycle during each alternating cycle (i.e., switches S1 and S2 are only turned on for half of the resonant cycle at a time), a larger voltage difference can be generated across the flying capacitor Cfly through the LC resonance process, effectively improving the energy transfer capability and efficiency of balancing circuit 300.

[0056] 6a and 6b are respectively a schematic diagram and a waveform diagram of the resonant charge transfer principle of the equalization circuit according to the second embodiment of the present invention.

[0057] In Figure 6a, the waveforms when the flying capacitor Cfly, maintained at voltage Vf, is connected to the left-hand battery cell BAT1 (higher voltage, V0) and the right-hand battery cell BAT2 (lower voltage, V1) are shown in the upper and lower right corners of Figure 6b. As shown in Figure 6b, the energy transfer during the LC resonance process causes a contact surge, resulting in a voltage difference nearly twice the pre-contact voltage during contact. If the switch is disconnected during the half-resonant period, the resonance-induced voltage boost can be maintained on the flying capacitor Cfly. During the charge transfer process, the flying capacitor Cfly is alternately connected between the two battery cells with a voltage difference. This process continuously increases the amplitude of the contact surge, ultimately stabilizing at a level determined by the equivalent total path impedance Rloss (i.e., the resonant tank Q).

[0058] Figure 7 is a schematic diagram of the structure of the minimum balancing unit in the balancing circuit of Figure 5. In this embodiment, the conduction of switches S1 and S2 in the balancing unit 302 is determined by the operating frequency or external triggering, and the conduction time is determined by the switches themselves.

[0059] As shown in Figure 7, each balancing unit 302 of this embodiment includes switches S1 and S2, a voltage detection module 325, and a current zero-crossing detection module 326. The voltage detection module 325 is used to obtain the voltage change on the flying capacitor Cfly corresponding to the balancing unit 302 in which it is located, and turn on the corresponding switch S1 or S2 according to the voltage change.

[0060] The current zero-crossing detection module 326 is used to determine the current polarity when switch S1 or S2 is turned on, and based on this current polarity, disconnect switch S1 or S2 when the current drops to zero. By ensuring that switches S1 and S2 in the balancing unit 302 are turned on for half the resonant cycle, the current in the series circuit of the inductor and capacitor is zero each time the switch is turned on or off, achieving zero-current switching and significantly reducing switching losses in the balancing circuit.

[0061] For the circuit shown in Figure 5, resonance occurs not only between the two sub-power supply groups. The corresponding switches need to detect the current polarity when they are conducting and disconnect the switches based on this current polarity when the current drops to zero. The process of the contact surge from the current rising to the current falling back to zero corresponds to half a resonance cycle. Using zero-crossing current detection to trigger the disconnection of the switches can prevent the switches in one balancing unit from being affected by the resonance of the switches in other balancing units, thereby improving circuit stability and efficiency.

[0062] It should be understood that the balancing circuits 200 and 300 in the above embodiments may also have other module structures, such as a detection circuit for detecting the battery voltage of each power supply in the power supply group, a control circuit for generating a start signal with a logical timing based on the MCU chip control instruction, and an isolation transformer connected between the high-voltage area and the low-voltage area, etc. Because their module structures and circuit principles are well known in the existing public technology, they are not shown here and will not be described in detail, but they are not intended to limit the present disclosure.

[0063] According to another embodiment of the present invention, a balancing method is provided, which can be implemented by the balancing circuit in the above embodiment, including: splitting a power supply group consisting of multiple power supplies connected in series into multiple sub-power supply groups, each sub-power supply group including at least one power supply. For example, the power supply can be a battery cell such as a lithium-ion battery, a nickel-cadmium battery, a nickel metal cyanide battery, a lead-acid battery, a nickel-zinc battery, or other rechargeable battery. Then, multiple balancing units and energy storage elements are provided, each balancing unit and energy storage element is connected to a corresponding sub-power supply group, the energy transmission path between the corresponding sub-power supply group and the energy storage element is changed by the balancing unit, and energy is transferred between the multiple sub-power supply groups using the charging and discharging process of the multiple energy storage elements, so that the sub-power supply group with a higher voltage is charged by the sub-power supply group with a lower voltage, thereby achieving energy balancing between the multiple sub-power supply groups.

[0064] Furthermore, the balancing method also includes controlling the switching of switches in multiple balancing units using a combination of passive switching and active control during the balancing process between sub-power groups. For example, one balancing unit is selected from the multiple balancing units as a first balancing unit, and the remaining balancing units are used as second balancing units. When the balancing function between sub-power groups is enabled, a start signal is applied to the first balancing unit to control the switching of switches in the first balancing unit, so that the first end of the energy storage element corresponding to the first balancing unit is alternately connected to the positive and negative ends of the sub-power group corresponding to the first balancing unit. The energy storage element transmits a step wave with an amplitude equal to the DC voltage of the sub-power group corresponding to the first balancing unit to the remaining sub-power groups through the common node of the multiple energy storage elements. The remaining second balancing units decide to connect the first end of their corresponding energy storage elements to the positive and negative ends of the corresponding sub-power groups based on the voltage change trend of the energy storage elements connected to them. For example, if a second balancing unit detects a positive voltage change on its corresponding energy storage element, the first end of the corresponding energy storage element is connected to the positive end of the corresponding sub-power supply group; if a negative voltage change is detected on its corresponding energy storage element, the first end of the energy storage element is connected to the negative end of the corresponding sub-power supply group.

[0065] Through the above process, each sub-power supply group chops its own DC voltage and connects it together through the energy storage element connected to it. If the voltage of a sub-power supply group itself is too high, it will output energy to the sub-power supply group with a lower voltage; if the voltage of a sub-power supply group itself is too low, it will obtain energy from the remaining sub-power supply groups, ultimately realizing energy transfer between multiple sub-power supply groups.

[0066] In one embodiment, the energy storage element may include at least one flying capacitor to achieve the function of storing and releasing energy. In another embodiment, the energy storage element may include at least one flying capacitor in series with an inductor. By introducing an LC resonant structure into the energy storage element and switching on the switch in the balancing unit in a semi-resonant cycle during each alternating cycle, the LC resonance process can be used to generate a larger voltage difference on the flying capacitor, effectively improving energy transfer capacity and efficiency.

[0067] In summary, the balancing circuit and method provided in the embodiment of the present invention splits a power supply group consisting of multiple power supplies connected in series into multiple sub-power supply groups, each sub-power supply group including at least one power supply. Then, multiple balancing units and energy storage elements are provided, each balancing unit and energy storage element is connected to the corresponding sub-power supply group, and the energy transmission path between the corresponding sub-power supply group and the energy storage element is changed by the balancing unit, and the charging and discharging process of multiple energy storage elements is used to transfer energy between the multiple sub-power supply groups, so that the sub-power supply group with higher voltage is charged by the sub-power supply group with lower voltage, thereby achieving energy balance between the multiple sub-power supply groups. Compared with the traditional balancing circuit, the balancing circuit provided by the present invention can split the measurement and balancing circuit into each sub-power supply group for implementation, which is convenient for repair and maintenance. In addition, decomposing the high-voltage series power supply group into multiple sub-power supply groups is also beneficial to wiring design and EMC design.

[0068] In addition, the balancing circuit of the embodiment of the present invention can achieve balancing between adjacent sub-power groups / non-adjacent sub-power groups, and can also exchange energy with sub-power groups that are "far away". The balancing time is significantly shortened, and its topology structure is simple, the number of modules working is small, and the balancing efficiency can be significantly improved.

[0069] In addition, the switches in each balancing unit in the balancing circuit of the embodiment of the present invention only need to withstand the voltage on its corresponding sub-power group. Therefore, by keeping the voltage of each sub-power group itself below the safe voltage, the switches in the balancing unit can be manufactured using a withstand voltage value covered by conventional semiconductor processes, without the need to use switches with higher withstand voltage values, thereby enabling the balancing design of higher voltage power groups to be achieved at a lower cost.

[0070] In addition, the energy storage element in the balancing circuit of the embodiment of the present invention may include a structure in which at least one flying capacitor is connected in series with an inductor. By introducing an LC resonant structure in the energy storage element and turning on the switch in the balancing unit in a half-resonant cycle in each alternating cycle, a larger voltage difference can be generated on the flying capacitor by utilizing the LC resonance process, thereby effectively improving the energy transfer capability and efficiency.

[0071] Furthermore, the balancing circuit of the present invention can achieve better results when the number of power supplies is small. When this is the case, the charge and discharge measurement of each sub-power group is equivalent to that of a single power supply. The voltage at any tap can reflect the status of the entire power group, such as battery life, effective capacity, and unit voltage. This allows for more precise control and improves circuit efficiency.

[0072] In the above description, the well-known structural elements and steps are not described in detail. However, it should be understood by those skilled in the art that the corresponding structural elements and steps can be implemented by various technical means. In addition, in order to form the same structural elements, those skilled in the art can also design methods that are not completely the same as the methods described above. In addition, although each embodiment is described separately above, this does not mean that the measures in each embodiment cannot be advantageously used in combination.

[0073] The embodiments of the present invention are described above, but these embodiments do not describe all details in detail, nor do they limit the invention to specific embodiments. Obviously, many modifications and variations can be made based on the above description. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can make good use of the present invention and modify and use it based on the present invention. The scope of protection of the present invention shall be based on the scope defined by the claims of the present invention.

Claims

1. A balancing circuit for a power supply group, the power supply group comprising a plurality of sub-power supply groups connected in series, each of the sub-power supply groups comprising at least one power supply, the balancing circuit comprising: A plurality of balancing units, each balancing unit being connected to a corresponding one of the plurality of sub-power supply groups; as well as A plurality of energy storage elements, wherein the first ends of the plurality of energy storage elements are respectively connected to the corresponding balancing units, and the second ends of the plurality of energy storage elements are connected to a common node, Wherein, each of the balancing units comprises: a first switch connected between the positive terminal of the corresponding sub-power source group and the first terminal of the energy storage element; and a second switch connected between the negative terminal of the corresponding sub-power supply group and the first terminal of the energy storage element, Wherein, each balancing unit is configured to change the energy transmission path between the corresponding sub-power supply group and the energy storage element by alternately turning on the first switch and the second switch, so as to transfer energy between the multiple sub-power supply groups by adopting the charging and discharging process of the multiple energy storage elements.

2. The equalizing circuit according to claim 1, wherein: The plurality of balancing units include a first balancing unit and a plurality of second balancing units, The first balancing unit is configured to turn on the first switch or the second switch according to the start signal. The second balancing unit is configured to turn on the first switch or the second switch according to a voltage change on an energy storage element connected thereto.

3. The equalizing circuit according to claim 2, wherein: The plurality of second equalizing units are configured to: If a positive voltage change is detected on the energy storage element connected thereto, the first switch is turned on and the second switch is turned off; If a negative voltage change is detected on the energy storage element connected thereto, the second switch is turned on and the first switch is turned off.

4. The equalizing circuit according to claim 3, wherein: Each of the second balancing units further comprises: The voltage detection module is configured to turn on the first switch or the second switch according to a voltage change on the corresponding energy storage element.

5. The equalizing circuit according to claim 3 or 4, wherein: Each of the equalizing units further comprises: The current zero-crossing detection module is configured to obtain the current polarity of the switch turned on in the equalization unit, and switch the switch turned on to off when the current crosses zero according to the current polarity.

6. The equalizing circuit according to claim 1, wherein: Each of the energy storage elements comprises: at least one flying capacitor; or A structure in which at least one flying capacitor is connected in series with an inductor.

7. A method for balancing a power pack, comprising: Splitting the power supply group into a plurality of sub-power supply groups, each sub-power supply group comprising at least one power supply; A plurality of balancing units are provided, each balancing unit being connected to a corresponding one of the plurality of sub-power supply groups; Arrange a plurality of energy storage elements, wherein the first ends of the plurality of energy storage elements are respectively connected to the corresponding balancing units, and the second ends of the plurality of energy storage elements are connected to a common node; as well as In each of the balancing units, a first switch connected between the positive terminal of the corresponding sub-power supply group and the first terminal of the corresponding energy storage element, and a second switch connected between the negative terminal of the corresponding sub-power supply group and the first terminal of the corresponding energy storage element are provided; as well as The energy transmission path between the corresponding sub-power source groups and the energy storage elements is changed by alternately turning on the first switch and the second switch, so that energy is transferred between the multiple sub-power source groups through the charging and discharging process of the multiple energy storage elements.

8. The equalization method according to claim 7, wherein: The step of using the balancing unit to change the energy transmission path between the corresponding sub-power source group and the energy storage element also includes: Selecting one balancing unit from a plurality of balancing units as a first balancing unit, and selecting the remaining balancing units from the plurality of balancing units as second balancing units; Providing a start signal to the first balancing unit to control the switching of the switch in the first balancing unit; transmitting the step wave of the DC voltage of the sub-power supply group corresponding to the first balancing unit to the energy storage elements corresponding to the plurality of second balancing units through the common node; and The switching of the switches in each second balancing unit is controlled according to the voltage change on the energy storage element connected to the second balancing unit.

9. The equalization method according to claim 8, wherein: The step of controlling the switching of the switches in each second balancing unit according to the voltage change on the energy storage element connected to each second balancing unit comprises: If a positive voltage change is detected on the energy storage element, the first switch in the corresponding second balancing unit is turned on, and the second switch in the corresponding second balancing unit is turned off; If a negative voltage change is detected on the energy storage element, the second switch in the corresponding second balancing unit is turned on, and the first switch in the corresponding second balancing unit is turned off.

10. The equalization method according to claim 9, further comprising: The current polarity of the switch turned on in the balancing unit is obtained, and the switch turned on is switched off when the current passes through zero according to the current polarity.

11. The equalization method according to claim 7, wherein: Each of the energy storage elements comprises: at least one flying capacitor; or A structure in which at least one flying capacitor is connected in series with an inductor.

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