Control circuit for performing active equalization on battery

Abstract

The utility model discloses a control circuit for performing active equalization on a battery, which is characterized in that N battery cells are respectively connected in series with a low-voltage secondary winding through a first switch, the N battery cells are divided into i battery packs, and the i battery packs are respectively connected with a high-voltage primary winding through different second switches; the main control unit controls the on-off states of the first switch and the second switch, when top equalization is achieved, the battery cell with the highest voltage is controlled to be conducted and serves as a top equalization battery cell to magnetize the magnetic core, and then the battery pack with the lowest voltage is controlled to discharge magnetism. Therefore, the over-high voltage of the battery is prevented from being controlled to be charged to be higher in the top active equalization process. And when the bottom equalization is realized, the main control unit controls the battery pack with the highest voltage to be conducted so as to magnetize the magnetic core, so that the battery core with the lowest voltage is used as a bottom equalization battery core to discharge magnetism, and the situation that the voltage of the battery with the too low voltage becomes lower after active equalization is avoided.

Description

Technical Field

[0001] The utility model relates to the technical field of battery balancing control, and in particular to a control circuit for actively balancing batteries. Background Art

[0002] With the development of modern science and technology, batteries as an energy storage device have been widely used in electric motorcycles, electric scooters and home storage systems. The main technical implementation of battery energy storage devices is to connect multiple storage cells in series to obtain a cell string to meet the system voltage requirements, and then connect multiple cell strings in parallel to achieve the required ampere-hour power.

[0003] Due to the limitation of production process, there are individual differences between battery cells, which are specifically manifested in the incomplete consistency of capacity and voltage. If the voltage exceeds the allowable range, the battery cell will be easily damaged. Furthermore, if the voltage exceeds the upper and lower limits (taking nanophosphate lithium-ion batteries as an example, the lower limit voltage is 2V and the upper limit voltage is 3.6V), the battery may be irreversibly damaged. At least one consequence is that the battery self-discharge rate is accelerated. In addition, as the number of charge and discharge times of multiple battery cells connected in series increases, the voltage difference between them will become more obvious. If effective measures are not taken to solve the problem of consistency, the storage capacity of the battery energy storage device will be affected at the least, and the damage to the battery cell will be caused at the worst, and even safety accidents such as explosions will be caused.

[0004] As a result, the "balancing technology" in the battery management system (BMS) has been vigorously developed. Battery balancing technology is divided into two categories: passive balancing and active balancing. In the charging scenario, assuming that the Nth battery cell reaches the upper limit of the operating voltage first, and the remaining battery cells are expected to continue to maintain the current charging current, it is necessary to connect a branch in parallel to the Nth battery cell to divert part of the energy. If the diverted energy is dissipated through resistance heat dissipation, it is defined as passive balancing. If the diverted energy can be stored and utilized again through transfer, it is defined as active balancing. The diversity of active balancing schemes lies in how to control these energy transfers.

[0005] Active balancing technology is divided into many categories. Common energy transfer methods in general circuits include: inductors, capacitors, transformers, converters (Buck / Boost, etc.), and the use of transformers to achieve energy transfer is a common technical route in the current active balancing solution. Among them, the technology that uses a multi-winding transformer and can manage the charge and discharge balance of a single battery cell is commonly used in bottom balancing and top balancing. When the bottom balancing strategy (Bottom balancing) is used in the discharge mode, the BMS identifies the battery cell with lower capacity, controls the primary side of the transformer to conduct, and transfers energy from the outside to the battery cell; when the top balancing strategy (Top balancing) is generally used in the charging mode, the BMS identifies the battery cell with higher capacity, controls the secondary side of the transformer to conduct, and transfers energy from the battery cell to the outside. The reason why different modes are adopted in charging and discharging is that during the system discharge process, if the voltage of a certain battery cell is too low, the entire system will enter the discharge low-voltage cut-off protection early. Therefore, bottom balancing is adopted to continuously charge the battery cell with too low voltage with the energy of the entire system (including all batteries) to increase the voltage of the battery cell with low voltage, so that the balanced system will not terminate the discharge early due to the battery cell with low voltage, wasting the power in other batteries that can continue to discharge, resulting in loss of the endurance of the battery energy storage device; conversely, during the system charging process, if the voltage of a certain battery cell is too high, the entire system will enter the charge overvoltage cut-off protection early. Therefore, top balancing is adopted to continuously extract the energy of the battery cell with high voltage to charge the entire system (including all batteries) to reduce the voltage of the battery cell with high voltage, so that the balanced system will not terminate the charging early due to the battery cell with high voltage, while other batteries are not fully charged at this time, resulting in a reduction in the overall battery capacity. For example, the Chinese patent application (CN20171064064.1) proposes an active balancing circuit for achieving bottom balancing of the battery cell when it is in a discharging or stationary state and top balancing of the battery cell when it is in a charging or stationary state. The active balancing circuit of the application is based on the above-mentioned two different balancing modes, namely the bottom balancing mode and the top balancing mode, to avoid over-discharge and over-charge of the battery cell. A high-efficiency balancing technology is achieved through the clever coordination of two switching units. By adopting a building block design method for multiple balancing function boards, the active balancing circuit can adapt to the requirements of different battery cells being connected in series, thereby greatly improving flexibility.

[0006] When using a transformer to achieve energy transfer, the system must have a multi-winding transformer and many switching circuits to complete this task. Both bottom balancing and top balancing technologies use a multi-winding transformer with a high-voltage primary side (primary side) and a low-voltage secondary side (secondary side). The turn ratio (N:1) of the high-voltage primary winding and the low-voltage secondary winding is the number of cells in series. Using the characteristics of the discontinuous conduction mode (DCM), in bottom balancing, the entire battery energy is first converted into magnetic energy through the primary winding and stored in the magnetic core in the first half of the DCM cycle, and then the current is transferred back to the secondary winding to charge a single cell in the second half of the cycle. In top balancing, the energy of a single cell is first converted into magnetic energy through the secondary winding and stored in the magnetic core, and then the current is transferred back to the primary winding to charge the entire battery.

[0007] When achieving energy transfer, the problems with existing control structures and methods in the industry are:

[0008] (1) Although the energy conversion in the theoretical N:1 transformer is lossless, the real-world transformer will have energy loss. In the N:1 or 1:N voltage conversion, there will be a lot of energy loss in the magnetic core and winding group. Generally, the higher the N:1 ratio, the greater the loss.

[0009] (2) During charging, top balancing is performed to perform a 1:N voltage conversion, transferring the energy of the cell with a higher voltage to the entire system (all cells). In addition to the relatively large loss caused when the low-voltage side is turned on, there is another technical problem: there is more than one cell with a higher voltage in the system. When energy is taken out from a cell with a higher voltage and recharged to the system (all cells), the energy of this cell with a higher voltage will also be recharged to other cells with a higher voltage.

[0010] Taking the commonly used home storage 48V100Ah system as an example, usually 16 iron-lithium batteries are connected in series to form a 51.2V. For ease of understanding, let's take an extreme case. Assume that there are 16 iron-lithium batteries in series, half of the number (i.e. 8) of the batteries are 3.6V, and the other half (i.e. 8) of the batteries are 2.8V. Then when energy is taken out from a 3.6V battery and recharged to the 16 batteries, the voltage of the other 7 3.6V batteries will exceed 3.6V, and then the BMS will find that the voltage of these 7 batteries is too high. Subsequently, the cells with a voltage exceeding 3.6V are top-balanced to extract their energy and then charge the energy back into the system (i.e. 16 cells). Before the 8th cell is top-balanced, the voltage of the 8th cell has been charged to a very high value, much higher than 3.6V, because the voltages of the other 7 cells are also high. This will reduce the service life of the cell string and affect the balancing effect. Therefore, the transformer balancing technology is not widely adopted in the industry.

[0011] In addition, when performing bottom balancing during discharge to perform N:1 voltage conversion, in addition to the loss problem, there is also the same technical problem as top balancing, that is, there is more than one battery cell with low voltage in the system. When energy is taken out from the entire system (all batteries) and charged to a battery cell with low voltage, energy will be taken out from other batteries with low voltage in the process of taking out energy. Similarly, in an extreme case, assuming that there are 16 iron-lithium batteries in series, half of the batteries are 3.6V and half of the batteries are 2.8V, then in the process of taking out energy from the 16 batteries and charging them to a 2.8V battery cell, energy is also taken out from the other 7 2.8V batteries. Then the BMS will find that the voltage of these 7 batteries is lower, and then energy is taken out from the 16 batteries in turn to charge the batteries that are already lower than 2.8V. Then, before charging the 8th battery cell with low voltage, the 7 bottom balancings have taken out the voltage of the 8th battery cell 7 times, making the 8th battery cell much lower than 2.8V at this time.

[0012] Therefore, the top or bottom balancing implemented by the existing transformer is a repetitive useless control method, which controls the voltage of the battery with too low voltage to be lower, and controls the voltage of the battery with too high voltage to be higher, which is an erroneous and harmful balancing control process.

[0013] Therefore, it is necessary to design corresponding technical solutions to solve the problems existing in the above-mentioned active balancing control. Summary of the invention

[0014] The utility model aims to provide a control circuit for actively balancing batteries, so as to solve the problem of repeated useless control when the above-mentioned existing batteries are actively balanced.

[0015] The utility model provides a control circuit for actively balancing a battery, comprising a transformer, wherein the transformer comprises a magnetic core, a high-voltage primary winding wound around the magnetic core, and N low-voltage secondary windings; and

[0016] The control circuit further includes N first switches and N battery cells connected in series, the N battery cells are evenly divided into N battery cells one by one, the N first switches are evenly divided into N battery cells one by one, and the N low-voltage secondary windings are connected to the N battery cells one by one; in each of the battery cells, the battery cell is connected in series with the low-voltage secondary winding corresponding to the battery cell to which the battery cell belongs through the first switch in the battery cell to which the battery cell belongs; and the N battery cells are connected in series through the N battery cells;

[0017] The N battery cells are divided into i battery groups, i is an integer greater than or equal to 2, the high-voltage primary windings are divided into i, and the i battery groups each correspond to a high-voltage primary winding; the control circuit further includes i second switches, and the i battery groups are respectively connected to the i high-voltage primary windings through different second switches; and,

[0018] The control circuit further includes an analog-to-digital conversion module, a driving unit and a main control unit, wherein the analog-to-digital conversion module includes N input terminals, and the N input terminals of the analog-to-digital conversion module are connected to the N battery cells in a one-to-one correspondence;

[0019] The main control unit is connected to the analog-to-digital conversion module to collect the voltage of each of the N battery cells through the analog-to-digital conversion module;

[0020] The driving unit is connected to the i second switches and the N first switches, and the main control unit is connected to the driving unit to control the switching states of the second switch and the first switch through the driving unit, thereby controlling the battery cell with the highest voltage among the N battery cells to be turned on and magnetize the magnetic core as the top balancing battery cell, and then controlling the battery cell with the lowest voltage among the i battery groups to demagnetize; and the main control unit controls the switching states of the second switch and the first switch through the driving unit, thereby controlling the battery cell with the highest voltage among the i battery groups to be turned on and magnetize the magnetic core, and then controlling the battery cell with the lowest voltage among the N battery cells to demagnetize as the bottom balancing battery cell.

[0021] Preferably, the N battery cells are divided into i battery groups, the high-voltage primary winding is divided into i high-voltage primary windings, and the i battery groups are connected to the i high-voltage primary windings one by one through different second switches; or, the number of battery cells in the i-1 battery groups is set to be the same, and the number of battery cells in the i-th battery group is the quotient of N divided by i plus the remainder. The N does not necessarily need to be an integer multiple of the i. When N is an integer multiple of i, the number of battery cells in each battery group is N / i. When N is not an integer multiple of i, the number of battery cells in the 1st to i-1th groups is set to be the same, the i-th group is the quotient of N divided by i plus the remainder, and the number of battery cells in each battery group in the 1st to i-1th groups is the quotient of N divided by i. Regardless of whether N is an integer multiple of i, the ratio of the number of turns of the primary winding to the secondary winding is the number of battery cells in the battery group.

[0022] Preferably, the N battery cells are 16 battery cells, and the i battery packs are 4 battery packs.

[0023] Preferably, the main control unit is further used to control the switch states of the second switch and the first switch through the driving unit, and then when the maximum voltage difference among the N battery cells is greater than or equal to the top balancing start threshold, control the battery cell with the highest voltage among the N battery cells to be turned on and magnetize the magnetic core as the top balancing battery cell, and then control the battery pack with the lowest voltage among the i battery packs to discharge magnetism;

[0024] The main control unit is further used to control the switching states of the second switch and the first switch through the driving unit when the voltage of the top balancing cell is greater than the top balancing end threshold, thereby controlling the top balancing cell to continue magnetizing the magnetic core, and then controlling the battery pack with the lowest voltage among the i battery packs to discharge magnetism.

[0025] Preferably, the main control unit is further configured to control the switch states of the second switch and the first switch through the driving unit when the maximum voltage difference among the N battery cells is greater than or equal to the bottom balancing start threshold, thereby controlling the battery pack with the highest voltage among the i battery packs to be turned on, so as to magnetize the magnetic core, and then control the battery cell with the lowest voltage among the N battery cells to serve as the bottom balancing battery cell for demagnetization;

[0026] The main control unit is further used to control the switching states of the second switch and the first switch through the driving unit when the voltage of the bottom balancing cell is less than the bottom balancing end threshold, thereby controlling the battery pack with the highest voltage among the i battery packs to be turned on to magnetize the magnetic core, and then controlling the battery cell with the lowest voltage among the N battery cells to continue to serve as the bottom balancing cell for demagnetization.

[0027] Preferably, the first switch and the second switch are high-frequency switches respectively.

[0028] Preferably, the main control unit and the driving unit are single chip microcomputers.

[0029] Preferably, the analog-to-digital conversion module includes a high-precision analog-to-digital converter.

[0030] Preferably, the analog-to-digital conversion module includes a MUX multiplexing device, a differential amplifier module and an analog-to-digital converter connected in series.

[0031] Preferably, the first switch and the second switch are metal oxide semiconductor field effect transistors.

[0032] In the control circuit for actively balancing batteries provided by the utility model, the control circuit includes N first switches and N battery cells connected in series, the N battery cells are evenly divided into N battery units one by one, the N first switches are evenly divided into N battery units one by one, and the N low-voltage secondary windings are connected to the N battery units one by one; in each of the battery units, the battery cell is connected in series with the low-voltage secondary winding corresponding to the battery unit to which the battery cell belongs through the first switch in the battery unit to which the battery cell belongs; and the N battery units are connected in series through the N battery cells; the N battery cells are divided into i battery groups, where i is an integer greater than or equal to 2; the control circuit also includes i second switches, and the i battery groups are connected to the high-voltage primary winding through different second switches respectively; the The main control unit is connected to the analog-to-digital conversion module to collect the voltage of each of the N battery cells through the analog-to-digital conversion module; the driving unit is connected to the i second switches and the N first switches, and the main control unit is connected to the driving unit to control the switching states of the second switch and the first switch through the driving unit, thereby controlling the battery cell where the battery cell with the highest voltage among the N battery cells is located to be turned on, and magnetize the magnetic core as the top balancing battery cell, and then control the battery cell with the lowest voltage among the i battery groups to be demagnetized; and the main control unit controls the switching states of the second switch and the first switch through the driving unit, thereby controlling the battery cell with the highest voltage among the i battery groups to be turned on, magnetize the magnetic core, and then control the battery cell with the lowest voltage among the N battery cells to be demagnetized as the bottom balancing battery cell.

[0033] In the control circuit provided by the utility model, when realizing top balancing, the main control unit turns on the first switch connected to the top balancing cell in the upper half cycle of the DCM through the characteristics of the discontinuous conduction mode (DCM), so that it is in the on state, realizes the magnetization of the magnetic core, that is, transfers the energy of the top balancing cell, and then turns off the first switch connected to the top balancing cell in the lower half cycle of the DCM, so that it is in the off state, and controls the second switch connected to the battery pack with the lowest voltage among the i battery packs to turn on, so that it is in the on state, realizes the magnetic core to discharge the magnetism of the battery pack with the lowest voltage among the i battery packs, that is, realizes the transfer of energy from the magnetic core to the battery pack with the lowest voltage among the i battery packs, and avoids a wrong and harmful balancing control process of controlling the voltage of the battery with too high voltage to be higher; and, in the control circuit provided by the utility model, when realizing bottom balancing, the main control unit turns on the first switch connected to the top balancing cell in the upper half cycle of the DCM, so that it is in the off state, and controls the second switch connected to the battery pack with the lowest voltage among the i battery packs to turn on, so that it is in the on state, realizes the magnetic core to discharge the magnetism of the battery pack with the lowest voltage among the i battery packs, that is, realizes the transfer of energy from the magnetic core to the battery pack with the lowest voltage among the i battery packs, and avoids a wrong and harmful balancing control process of controlling the voltage of the battery with too high voltage to be higher; and In the first half of the DCM cycle, the second switch of the battery pack with the highest voltage among the i battery packs is turned on to magnetize the magnetic core, that is, the energy of the battery pack with the highest voltage among the i battery packs is transferred. Then, in the second half of the DCM cycle, the second switch of the battery pack with the highest voltage among the i battery packs is turned off to be in the off state, and the first switch connected to the battery cell with the lowest voltage among the N battery cells is controlled to be turned on to be in the on state, so that the battery cell with the lowest voltage among the N battery cells is used as the bottom balancing battery cell for demagnetization, thereby avoiding an erroneous and harmful balancing control process in which the voltage of the battery that is already too low is controlled to be even lower. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present utility model, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative work, among which:

[0035] Figure 1 A schematic diagram of the circuit connections of N cells in a control circuit for active balancing provided in an embodiment of the utility model;

[0036] Figure 2 A schematic diagram of the circuit connections of i battery packs in a control circuit for active balancing provided in an embodiment of the utility model;

[0037] Figure 3aA schematic diagram of the connection between a battery pack and a transformer in a control circuit for active balancing provided in an embodiment of the utility model;

[0038] Figure 3b A schematic diagram of the connection lines of the combined devices of a battery pack in the control circuit for active balancing provided by an embodiment of the utility model;

[0039] Figure 4 A schematic diagram of the connection lines of a system assembly device using 16 battery cells in a control circuit for active balancing provided by an embodiment of the utility model;

[0040] Figure 5 A schematic diagram of the connection structure between the cells in the first battery pack and the second battery pack and the transformer in a control circuit provided by an embodiment of the utility model;

[0041] Figure 6 A schematic diagram of the connection structure between the battery cells in the first battery pack and the second battery pack and the transformer in another control circuit provided in an embodiment of the utility model. DETAILED DESCRIPTION

[0042] The technical solutions in the embodiments of the present utility model are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present utility model, not all of them. Based on the embodiments of the present utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present utility model.

[0043] The utility model aims to provide a control circuit for actively balancing batteries, so as to solve the problem of repeated useless control when the above-mentioned existing batteries are actively balanced.

[0044] In the control circuit for actively balancing batteries provided by the utility model, the control circuit includes N first switches and N battery cells connected in series, the N battery cells are evenly divided into N battery units one by one, the N first switches are evenly divided into N battery units one by one, and N low-voltage secondary windings are connected to the N battery units one by one; in each battery unit, the battery cell is connected in series with the low-voltage secondary winding corresponding to the battery unit to which the battery cell belongs through the first switch in the battery unit to which the battery cell belongs; and the N battery units are connected in series through the N battery cells; the N battery cells are divided into i battery groups, i is an integer greater than or equal to 2, the high-voltage primary winding is divided into i, and the i battery groups each correspond to a high-voltage primary winding; the control circuit also includes i second switches, and the i battery groups are respectively connected through different The second switch is connected to the i high-voltage primary windings; the main control unit is connected to the analog-to-digital conversion module to collect the voltage of each of the N battery cells through the analog-to-digital conversion module; the driving unit is connected to the i second switches and the N first switches, and the main control unit is connected to the driving unit to control the switching states of the second switch and the first switch through the driving unit, thereby controlling the battery cell where the battery cell with the highest voltage among the N battery cells is located to be turned on, and to magnetize the magnetic core as the top balancing battery cell, and then control the battery cell with the lowest voltage among the i battery packs to discharge magnetism; and the main control unit controls the switching states of the second switch and the first switch through the driving unit, thereby controlling the battery cell with the highest voltage among the i battery packs to be turned on, to magnetize the magnetic core, and then controls the battery cell with the lowest voltage among the N battery cells to be discharged magnetism as the bottom balancing battery cell.In the control circuit provided by the utility model, when implementing top balancing, the main control unit turns on the first switch connected to the top balancing cell in the first half cycle of the DCM through the characteristics of the discontinuous conduction mode (DCM), so that it is in the on state, and realizes the magnetization of the magnetic core, that is, the energy of the top balancing cell is transferred, and then the first switch connected to the top balancing cell is closed in the second half cycle of the DCM, so that it is in the off state, and the second switch connected to the battery pack with the lowest voltage among the i battery packs is controlled to be turned on, so that it is in the on state, and the magnetic core is demagnetized to the battery pack with the lowest voltage among the i battery packs, that is, the energy is transferred from the magnetic core to the battery pack with the lowest voltage among the i battery packs, avoiding an erroneous and harmful balancing control process in which the voltage of the battery with an already high voltage is controlled to be charged to a higher voltage during the top active balancing process; and, in the control circuit provided by the utility model, when implementing bottom balancing, the main control unit turns on the first switch connected to the top balancing cell in the first half cycle of the DCM, so that it is in the off state, and the second switch connected to the battery pack with the lowest voltage among the i battery packs is controlled to be in the on state, so that the magnetic core is demagnetized to the battery pack with the lowest voltage among the i battery packs, that is, the energy is transferred from the magnetic core to the battery pack with the lowest voltage among the i battery packs, and avoids the voltage of the battery with an already high voltage being controlled to be charged to a higher voltage during the top active balancing process; and In the first half of the DCM cycle, the second switch of the battery pack with the highest voltage among the i battery packs is turned on to magnetize the magnetic core, that is, to transfer the energy of the battery pack with the highest voltage among the i battery packs. Then, in the second half of the DCM cycle, the second switch of the battery pack with the highest voltage among the i battery packs is turned off to be disconnected, and the first switch connected to the battery cell with the lowest voltage among the N battery cells is controlled to be turned on to be turned on, so that the battery cell with the lowest voltage among the N battery cells is used as the bottom balancing battery cell for demagnetization, thereby avoiding an erroneous and harmful balancing control process in which the voltage of the battery that is already too low is controlled to be even lower.

[0045] like Figure 1 As shown, a circuit connection diagram of N cells in a control circuit for active battery balancing is provided, wherein the control circuit includes a transformer 110, and the transformer 110 includes a magnetic core, a high-voltage primary winding wound around the magnetic core, and N low-voltage secondary windings ( Figure 1 Only the first low-voltage secondary winding 1 and the Nth low-voltage secondary winding N are shown in FIG. 1 ); the winding method of the magnetic core in the transformer 110 can refer to the common technical means in the technical field. And the control circuit also includes N first switches ( Figure 1 The first first switch 1 and the Nth first switch N) and the N cells connected in series ( Figure 1 The first battery cell 1 and the Nth battery cell N are shown in FIG. 1 ), and the N battery cells are evenly divided into N battery units (eg Figure 1In the battery cell 120 shown in the figure, N first switches are evenly distributed to the N battery cells, and N low-voltage secondary windings are connected to the N battery cells one by one; in each battery cell, the battery cell is connected in series with the low-voltage secondary winding corresponding to the battery cell to which the battery cell belongs through the first switch in the battery cell to which the battery cell belongs; and the N battery cells are connected in series through the N battery cells.

[0046] like Figure 2 As shown, a circuit connection diagram of i battery groups in a control circuit for active battery balancing is provided. In the control circuit, N cells are divided into i battery groups ( Figure 2 The first battery pack 1 and the i-th battery pack i are shown in FIG. 1 , where i is an integer greater than or equal to 2; the control circuit further includes i second switches ( Figure 2 The first second switch 1 and the i-th second switch i are shown in the figure, and the i battery packs are connected to the high-voltage primary winding through different second switches. The N battery cells are divided into i battery packs, the high-voltage primary winding is divided into i high-voltage primary windings, and the i battery packs are connected to the i high-voltage primary windings one by one through different second switches; or, the number of battery cells in the i-1 battery packs is the same, and the number of battery cells in the i-th battery pack is the quotient of N divided by i plus the remainder.

[0047] In other embodiments, the N does not necessarily need to be an integer multiple of the i. When N is an integer multiple of i, the number of battery cells in each battery pack is N / i, that is, the N battery cells are evenly divided into i battery groups. When N is not an integer multiple of i, the number of battery cells in the 1st to i-1th groups is set to be the same, the i-th group is the quotient of N divided by i plus the remainder, and the number of battery cells in the 1st to i-1th groups is the quotient of N divided by i. Regardless of whether N is an integer multiple of i, the ratio of the number of turns of the primary winding and the secondary winding corresponding to each battery pack is the number of battery cells in the battery pack.

[0048] For example, there are 13 battery cells in total, which are divided into 3 groups, N=13, i=3, the first and second groups are 4 battery cells, and the last group is 5 battery cells; for another example, there are 17 battery cells, which are divided into 4 groups, N=17, i=4, the first to third groups are 4 battery cells, and the fourth group is 5 battery cells.

[0049] However, when designing, we often do not decide how many groups there are first, but how many cells are in each group. Therefore, when there are more cells in each group and the remainder is large, the remainder can be formed into a separate group. For example, if each group is decided to have 8 cells, a total of 23 cells can be divided into three groups of 8+8+7.

[0050] Regardless of the number of groups, the ratio of the number of primary winding turns to the number of secondary winding turns corresponding to the group is the number of battery cells in the group.

[0051] In the embodiment provided by the present utility model, the number of high-voltage primary windings is the same as the number of battery packs.

[0052] For example, 16 battery cells are divided into 4 battery groups, and the number of high-voltage primary windings can be formed by combining 4 groups, and the 4 groups are connected to the 4 battery groups one by one through different second switches.

[0053] like Figure 3a As shown, a schematic diagram of connecting components of a battery pack and a transformer 110 in a control circuit for active battery balancing is provided. For example, 16 cells are divided into 4 battery packs, each battery pack includes 4 cells connected in series. Figure 3a The component connection structure of the battery pack 1 (i.e., the first battery pack) and the transformer 110 is shown. In this embodiment, the high-voltage primary winding of the transformer 110 is formed by 4 groups. The battery pack 1 includes 4 battery cells, namely battery cells BAT_1, BAT_2, BAT_3 and BAT_4. Each battery cell is connected in series with a first switch. The 4 battery cells (battery cells BAT_1, BAT_2, BAT_3 and BAT_4) are connected to the 4 first switches (first switches SW_S11, SW_S12, SW_S13 and SW_S14) in a one-to-one correspondence. The two ends of the battery pack are connected to the two ends of a high-voltage primary winding in the 4 groups of the high-voltage primary winding of the transformer 110 through the second switch SW_P1. Figure 3a The filter capacitor connected in parallel with the battery cell shown in FIG. 1 has no effect on the top balance control principle and the bottom balance control principle of the active balance control in the embodiment of the utility model, so it will not be described and explained here. Figure 3a The filter capacitors are shown in FIG.

[0054] like Figure 3b As shown, a schematic diagram of the connection lines of the combined devices of a battery pack in a control circuit for active battery balancing is provided. For example, 16 battery cells are divided into 4 battery packs, each battery pack includes 4 battery cells connected in series. Figure 3b A schematic diagram showing the connection lines of the combined devices of a battery pack is based on Figure 3a, and a first switch corresponding to each battery cell in the battery pack, and a second switch corresponding to the battery pack, the combined device connection line schematic diagram, the combined device is a connection line schematic diagram of the first battery pack 1, the combined device includes all the battery cells (battery cells BAT_1, BAT_2, BAT_3 and BAT_4) divided into the single battery pack, and the first switch (first switch SW_S11, SW_S12, SW_S13 and SW_S14) in the battery unit to which each battery cell in the single battery pack belongs, and the second switch SW_P1 corresponding to the single battery pack. In the embodiment of the present invention, all the first switches and the second switches are high-frequency switches.

[0055] like Figure 3b As shown, in the schematic diagram of the combined device connection line, the control signal connection lines (SW_S11, SW_S12, SW_S13 and SW_S14) of the first switch in the battery unit to which each battery cell in the single battery pack belongs, and the control signal connection line SW_P1 of the second switch correspondingly connected to the single battery pack are identified on the left. In the schematic diagram of the combined device connection line, the positive electrode voltage signals (BAT_1, BAT_2, BAT_3 and BAT_4) of all the batteries in the single battery pack are identified on the right, and the negative electrode signal (BAT_1_negative) of one of the batteries is identified at the bottom on the right.

[0056] like Figure 4 As shown, a schematic diagram of the connection lines of a system combination device using 16 cells in a control circuit for active battery balancing is provided. Figure 4 The system combination device shown is composed of the four above Figure 3b The combined devices of the battery pack shown are connected, and the four combined devices are combined device 411, combined device 412, combined device 413 and combined device 414, each of which is based on Figure 3a A schematic diagram of the connection of a combination of each battery cell in a battery pack, a first switch correspondingly connected to each battery cell in the battery pack, and a second switch correspondingly connected to the battery pack is shown.

[0057] For example, the combination device 411 is a schematic diagram of the connection lines of the first battery pack 1, and the combination device 411 includes all the battery cells (battery cells BAT_1, BAT_2, BAT_3 and BAT_4) divided into the single battery pack, and the first switches (first switches SW_S11, SW_S12, SW_S13 and SW_S14) in the battery cells to which each battery cell in the single battery pack belongs, and the second switch SW_P1 connected to the corresponding single battery pack.

[0058] Furthermore, the combination device 412 is a schematic diagram of the connection lines of the second battery pack 2, and the combination device 412 includes all the battery cells (battery cells BAT_5, BAT_5, BAT_7 and BAT_8) divided into the single battery pack (the second battery pack 2), and the first switches (first switches SW_S21, SW_S22, SW_S23 and SW_S24) in the battery cells to which each battery cell in the single battery pack belongs, and the second switch SW_P2 connected to the corresponding single battery pack.

[0059] Furthermore, the combination device 413 is a schematic diagram of the connection lines of the third battery pack 3, and the combination device 413 includes all the battery cells (battery cells BAT_9, BAT_10, BAT_11 and BAT_12) divided into the single battery pack (the third battery pack 3), and the first switches (first switches SW_S31, SW_S32, SW_S33 and SW_S34) in the battery cells to which each battery cell in the single battery pack belongs, and the second switch SW_P3 corresponding to the single battery pack.

[0060] Furthermore, the combination device 414 is a schematic diagram of the connection lines of the fourth battery pack 4, and the combination device 414 includes all the battery cells (battery cells BAT_13, BAT_14, BAT_15 and BAT_16) divided into the single battery pack (the fourth battery pack 4), and the first switches (first switches SW_S41, SW_S42, SW_S43 and SW_S44) in the battery cells to which each battery cell in the single battery pack belongs, and the second switch SW_P4 corresponding to the single battery pack.

[0061] like Figure 4 As shown, in the embodiment of the utility model, the control circuit further includes an analog-to-digital conversion module 130, a driving unit 140 and a main control unit 150, and the analog-to-digital conversion module 130 includes N input terminals, and the N input terminals of the analog-to-digital conversion module 130 are connected one-to-one with N battery cells (i.e., 16 battery cells, namely BAT_1, BAT_2, BAT_3 and BAT_4, and BAT_5, BAT_7, BAT_8, and BAT_9, BAT_10, BAT_11 and BAT_12, and BAT_13, BAT_14, BAT_15 and BAT_16). Figure 4As shown, the analog-to-digital conversion module 130 can be realized by connecting a MUX multiplexing device and an analog-to-digital converter. The main control unit 150 and the driving unit 140 are single-chip microcomputers. If you want to directly connect 16 battery cells to an analog-to-digital converter through a voltage divider resistor and perform analog-to-digital conversion ADC in a single-ended input (Single Ended) mode, the accuracy of the ADC must be very high. In other embodiments, if an analog-to-digital converter with less accuracy is used, a MUX multiplexing device with double-pole input and output can be used. The double-pole output of the MUX is then connected to a differential amplifier, and the voltage of each battery cell is converted into a single-ended output using the differential amplifier, and then the single-ended output voltage of the differential amplifier is connected to the analog-to-digital converter ADC.

[0062] In other embodiments, the analog-to-digital conversion module 130 is implemented by a high-precision analog-to-digital converter.

[0063] like Figure 4 As shown, the main control unit 150 is connected to the analog-to-digital conversion module 130 to collect the voltage of each of the N battery cells through the analog-to-digital conversion module 130; the driving unit 140 is connected to i second switches (i.e., 4 second switches, namely SW_P1, SW_P2, SW_P3 and SW_P4) and N first switches (i.e., 16 first switches shown in this embodiment, namely SW_S11, SW_S12, SW_S13 and SW_S14, and SW_S21, SW_S22, SW_S 23 and SW_S24, as well as SW_S31, SW_S32, SW_S33 and SW_S34, and SW_S41, SW_S42, SW_S43 and SW_S44), the main control unit 150 is connected to the driving unit 140 to control the switching states of the second switch and the first switch through the driving unit 140, thereby controlling the battery cell where the battery cell with the highest voltage among the N battery cells is located to be turned on, and magnetizing the magnetic core as the top balancing battery cell, and then controlling the battery pack with the lowest voltage among the i battery packs to discharge magnetism. In the embodiment of the utility model, the main control unit 150 can be implemented by a main control chip.

[0064] In the embodiment of the utility model, the transformer 110 is constructed according to the principle of a flyback converter transformer 110. This type of transformer 110 can store energy in a magnetic field. If a low-frequency (e.g., 10kHz or lower) ferrite core is used, the air gap can be increased to increase the magnetic resistance to avoid magnetic saturation of the core material. However, if a toroidal transformer 110 is used, there is no need to increase the air gap for high-frequency switching (e.g., 50kHz).

[0065] In the embodiment of the utility model, the main control unit 150 controls the driving unit 140 to dynamically control different battery packs and different single cells to conduct under different voltage distribution conditions, and to perform flyback energy conversion with different primary and secondary side combinations. The specific process of magnetization and demagnetization is described here. The cell is turned on through the switch and the transformer 110. After the conduction, the current direction flows from the cell to the winding of the transformer 110. The current generated by the cell voltage in the winding of the transformer 110 gradually increases, and the electric energy is gradually converted into the magnetic flux in the magnetic core, that is, the electric energy is converted into magnetic energy. In the embodiment of the utility model, this process of gradually establishing the magnetic flux is called "magnetization". On the contrary, the cell is turned on through the switch and the winding. After the conduction, the current direction flows back to the cell, and the magnetic flux in the magnetic core gradually decreases. We call the process of converting this magnetic energy back to the current through the winding and gradually flowing back to the cell "demagnetization".

[0066] The "magnetization" and "demagnetization" defined herein are different from the commonly used meanings in the industry and are only used to simplify and shorten the length of the text explanation in the description of the embodiments of the utility model. Outside the description of the embodiments of the utility model, the two definitions of "magnetization" and "demagnetization" used in the embodiments of the utility model are not applicable to the commonly used terms in the industry.

[0067] According to the above Figures 1 to 4 The structure of the control circuit shown schematically illustrates the control analysis of top equalization.

[0068] Taking the 48V100Ah, 16 iron-lithium cells in series with a nominal voltage of 51.2V commonly used in home storage systems as an example, after the 16 cells are divided into 4 groups (i.e. 4 battery packs), assuming that the voltage of the 7th cell BAT_7 is too high, and the total voltage of the 4 cells (BAT_1, BAT_2, BAT_3 and BAT_4) in the first battery pack 1 of the 4 battery packs is the lowest, that is, it is the battery pack with the lowest voltage among the 4 battery packs, then top balancing is adopted when the system is charged.

[0069] like Figure 5 As shown, due to limited space, the connection structure between the cells in the first battery pack and the second battery pack and the transformer 110 is illustrated. Figure 5 The left side shows the first half of the DCM cycle. First, SW_S23 corresponding to BAT_7 is turned on to magnetize the core, and then Figure 5 In the second half of the DCM cycle on the right, SW_S23 is disconnected and SW_P1 is turned on to discharge the cells BAT_1 to BAT_4 of the first battery pack 1.

[0070] In the above example, the battery pack with the lowest voltage is used as the basis for judging magnetic discharge. In this example, the number of cells in each battery pack is equal, so there is no difference between the battery pack with the lowest total voltage and the battery pack with the lowest average voltage as the basis for judging magnetic discharge. However, when the number of cells in the battery pack is different, the average value of the battery pack should be used as the basis for judging magnetic discharge.

[0071] In order to illustrate the superiority of the structure in which the high-voltage primary winding groups in the embodiment of the utility model are demagnetized by i second switches connected to i battery groups, compared with the traditional structure in which only one winding on the primary side is used to demagnetize all the battery cells, an example is given. Figure 5 The battery cells BAT_5 to BAT_8 in the second battery pack 2 were originally 3.6V, while the battery cells BAT_1 to BAT_4 in the first battery pack 1 were all 2.8V. If the traditional top balancing is used, that is, BAT7 is turned on first to magnetize the magnetic core, and then all 16 battery cells are discharged together, then the voltages of BAT_5, BAT_6, and BAT_8 will all be higher than 3.6V, becoming an overcharged state, and the top balancing process will continue to be performed on BAT_5, BAT_6, and BAT_8. When it comes to the turn of the last battery cell to be top balanced, it is charged by top balancing at least 3 times after it has exceeded the overcharge cut-off voltage, resulting in a very serious risk of overvoltage charging.

[0072] In the embodiment of the utility model, after being divided into 4 battery groups, the battery cell BAT_7 with the highest voltage is first turned on to magnetize the magnetic core, and then the first battery group 1 with the lowest voltage among the 4 battery groups is discharged, thereby solving the problem of transferring the energy of the battery cell with a relatively high voltage to the battery cell with a relatively high voltage in the traditional structure.

[0073] Although it is possible that the cell with the highest voltage and some cells with too low voltage will be grouped in the same battery pack, making this battery pack the group with the lowest voltage, it is possible that the cell with the highest voltage transfers energy to itself, but in the top balancing of a battery pack with 4 cells, the energy transferred out each time is 4 times the energy transferred back, and the cell with the highest voltage can be quickly turned into a cell with normal voltage through top balancing. Or it is possible that a cell with relatively high energy and some other cells with too low voltage are together to form the battery pack with the lowest voltage. However, in any case, it will never happen that several cells with relatively high voltage are in the same battery pack to form the group with the lowest voltage. Therefore, energy is always transferred from the cell with the highest voltage to each cell in the battery pack with the lowest voltage, avoiding the risk of very serious overvoltage charging, greatly reducing useless balancing operations, and improving the efficiency of active balancing control.

[0074] In the embodiment of the utility model, in the new battery cell series grouping structure, the high-voltage primary winding is divided into 4 windings, and in the top balancing process, high-frequency switching is used to transfer energy from any one of the 16 battery cells through the magnetic core to any group of 4 battery cells. The high-frequency switching control technology is used to realize real-time confirmation and transfer from the battery cell with the highest voltage to the battery pack with the lowest group voltage. This is a technology that adaptively transfers energy according to the battery cell voltage distribution status at all times, further improving the efficiency of active balancing control.

[0075] Compared with the traditional top balancing structure, the grouped structure and adaptive energy transfer from the highest voltage cell to the lowest voltage group can greatly reduce the probability of transferring energy from a high voltage cell to a high voltage cell by several times, avoiding unnecessary waste and the situation where the cell voltage exceeds the overcharge protection cut-off voltage, and can ensure that the energy is effectively transferred from the highest voltage cell to the lower voltage cell with a high probability.

[0076] Following the above analysis of the battery cell with the highest voltage and some battery cells with lower voltage in the same battery pack, after the battery cell with the highest voltage carries energy to the group with lower voltage for a period of time, the voltage of the battery cell with the highest voltage is judged by a top balancing cutoff threshold and becomes normal. Then, it is possible that the voltage of this group becomes the lowest. Later, after other new battery cells with the highest voltage are replaced and magnetized into the magnetic core, the system will demagnetize the new group with the lowest voltage. The battery cell that once had the highest voltage and just dropped to the normal voltage is demagnetized again because the voltage of the battery pack it is in is the lowest, causing the voltage to rise again and may become the battery cell with the highest voltage.

[0077] Therefore, in order to prevent the battery cell with the highest voltage from becoming the battery cell with the highest voltage again, a top balancing cutoff threshold is set. The top balancing cutoff threshold should be a safety margin lower than the general overcharge cutoff voltage. Taking iron-lithium batteries as an example, the overcharge cutoff voltage is generally set to 3.6V, while the nominal value is 3.2V. The top balancing cutoff threshold is set to 3.2V, that is, a 3.6V battery cell must continue to transport energy to the group with the lowest voltage through top balancing until the 3.6V battery cell drops to 3.2V before the top balancing is stopped. Because the cell that once had the highest voltage is no longer the cell with the highest voltage after several top balancing, but top balancing must continue for this cell until the top balancing cutoff threshold is reached. Only then will top balancing begin for the next cell with the highest voltage. Since as before, in the top balancing with 4 cells as a group, the energy carried out each time is 4 times the energy carried back, this can avoid the voltage oscillation phenomenon caused by the voltage of the cell with the highest voltage just dropping to normal after top balancing, and then being charged and rising to above the overcharge cutoff protection voltage because other cells with low voltage in the group become the group with the lowest voltage.

[0078] When the voltages of all cells are greater than the initially set top balancing threshold, the top balancing threshold is set to the average voltage of all cells so that all cells can have the same voltage after top balancing. A "safety margin" can be retained as before for hysteresis control to prevent the voltage from oscillating back and forth during balancing. Since this can be done by following the example above, I will not go into details.

[0079] Preferably, in the embodiment of the utility model, N battery cells are divided into i battery packs, N is an integer multiple of i, the high-voltage primary winding is divided into i high-voltage primary windings, and the i battery packs are connected to the i high-voltage primary windings one by one through different second switches. For example, N battery cells are 16 battery cells, and i battery packs are 4 battery packs. The control circuit and principle can refer to the example of 16 battery cells shown above.

[0080] In the embodiment of the utility model, the main control unit 150 is also used to control the switch states of the second switch and the first switch through the driving unit 140, and then when the maximum voltage difference among the N cells is greater than or equal to the top balancing start threshold, the battery unit where the cell with the highest voltage among the N cells is located is controlled to be turned on, and the magnetic core is magnetized as the top balancing cell, and then the battery pack with the lowest voltage among the i battery packs is controlled to discharge the magnetism. As shown in the example of 16 cells above, the cell BAT_7 is the cell with the highest cell voltage, so in the embodiment of the utility model, the cell BAT_7 is the top balancing cell.

[0081] The main control unit 150 is also used to control the switch states of the second switch and the first switch through the driving unit 140 when the voltage of the top balancing cell is greater than the top balancing end threshold, thereby controlling the top balancing cell to continue to magnetize the magnetic core, and then controlling the battery pack with the lowest voltage among the i battery packs to discharge magnetism. As shown in the example of 16 cells above, when the voltage of the cell BAT_7 is greater than the top balancing end threshold, the switch states of the second switch and the first switch are controlled by the driving unit 140, thereby controlling the top balancing cell to continue to magnetize the magnetic core, and then controlling the battery pack with the lowest voltage among the i battery packs to discharge magnetism. If the voltage of the cell BAT_7 is less than or equal to the top balancing end threshold, the control circuit ends this top balancing control, restarts the next round of top balancing start judgment, and then re-determines a top balancing cell.

[0082] According to the above Figures 1 to 4 The structure of the control circuit provided by the embodiment of the utility model is shown, and the bottom balance control is analyzed.

[0083] In an embodiment of the utility model, the main control unit 150 controls the switching states of the second switch and the first switch through the driving unit 140, thereby controlling the battery pack with the highest voltage among the i battery packs to be turned on to magnetize the magnetic core, and then controls the battery cell with the lowest voltage among the N battery cells to serve as the bottom balancing battery cell for demagnetization.

[0084] Taking the 48V100Ah, 16 iron-lithium battery cells connected in series that are commonly used in home storage as an example, after the 16 battery cells are divided into 4 battery groups, assuming that the voltage of the 7th battery cell is the lowest, and the total voltage of the 4 battery cells in the first battery group 1 among the 4 battery groups is the highest, bottom balancing is adopted during discharge.

[0085] like Figure 6 As shown, due to limited space, the connection structure between the cells in the first battery pack and the second battery pack and the transformer 110 is illustrated. Figure 6 The left side is the first half of the DCM cycle. First, SW_P1 is turned on to magnetize the magnetic core from the cells BAT_1 to BAT_4 of the first battery pack 1. Then, press Figure 6 The middle right side is the second half of the DCM cycle, when SW_P1 is disconnected and SW_S23 corresponding to BAT_7 is turned on to discharge magnetism from the magnetic core to BAT_7.

[0086] In order to illustrate the superiority of the structure in which the high-voltage primary winding grouping in the embodiment of the utility model magnetizes the magnetic core through the battery group connected to the i second switches compared with the traditional structure in which only one winding on the primary side magnetizes the magnetic core through all the battery cores, for example, assuming that BAT_5 to BAT_8 of the second battery group 2 are originally 2.8V, and BAT_1 to BAT_4 of the first battery group 1 are all 3.6V, if the traditional bottom balancing treatment is that all 16 battery cores of the system are turned on to magnetize the magnetic core in the first half of the DCM cycle, and then BAT_7 is discharged in the second half of the DCM cycle, then BAT_5, BAT_6, and BAT_8 are over-discharged, and the bottom balancing will continue to be performed on BAT_5, BAT_6, and BAT_8. When it is the turn of the last battery cell, it is possible that it has been discharged three more times when it is already below the over-discharge cut-off voltage, so that its voltage is already lower than the over-discharge cut-off voltage at that time, causing a very serious over-discharge risk.

[0087] In the embodiment of the utility model, after being divided into 4 battery groups, the high-voltage primary winding is divided into 4 groups of windings, and in an adaptive manner, the battery group with the highest voltage is turned on first in the first half of the DCM cycle to magnetize the magnetic core, and then the battery cell with the lowest voltage is discharged in the second half of the DCM cycle, thereby solving the problem of transferring the energy of the battery cell with low voltage to other battery cells in the traditional structure.

[0088] For example, in the embodiment of the utility model, the bottom balancing process is to extract energy from the first battery pack 1 with the highest group voltage, BAT_1 to BAT_4 are all 3.6V, and use high-frequency switching to pass through the magnetic core, and sequentially transfer the energy to BAT_5 to BAT_8 with a cell voltage of 2.8V. Energy will not be transferred out from the cell with too low voltage at all. This solves the problem of extracting energy from a cell with a low cell voltage and transferring it to a cell with the lowest cell voltage.

[0089] Although it is possible that the battery cell with the lowest voltage and some battery cells with too high voltage will be grouped in the same battery pack, which may make this battery pack the group with the highest voltage, but because the group with the highest voltage in the first half of the cycle is that 4 battery cells magnetize the magnetic core, and the magnetic core demagnetizes a single battery cell (the battery cell with the lowest voltage) in the second half of the cycle, the current flowing into the battery cell when the magnetic core is demagnetized in the second half of the cycle is 4 times the current flowing out of the magnetic core when it is magnetized in the first half of the cycle, so soon the battery cell with the lowest voltage is no longer the battery cell with the lowest voltage.

[0090] Because in order to become the battery pack with the highest voltage in the group, the voltage of other cells together with the cell with the lowest voltage must be relatively high to make this battery pack the battery pack with the highest voltage in the group. Therefore, during the bottom balancing process, it is very likely that energy will not be extracted from other cells with lower voltages, but energy will be extracted from cells with higher voltages. For example, in the example above, the second battery pack is 4 2.8V and the first battery pack is 4 3.6V. All the cells with lower voltages are in the same battery pack. In the traditional bottom balancing operation, the energy of other cells with lower voltages will be extracted and transferred to the battery pack. However, according to the control circuit structure provided in the embodiment of the utility model and adopting an adaptive control method, energy is always transferred from the battery pack with the highest voltage in other groups to the battery cell with the lowest voltage. Therefore, all the battery cells with low voltage are concentrated in one group, and there will be no situation where energy is transferred from the battery cells with low voltage to make their voltage lower. And the battery cell with the lowest voltage and some battery cells with high voltage are divided into the same battery group, which will not affect the operation of transferring energy from the battery pack with the highest voltage in the group to the battery cell with the lowest voltage, and the battery cell with the lowest voltage will soon become a normal voltage.

[0091] The same principle applies to setting the top balancing cutoff threshold for top balancing. In order to prevent the battery cell with the lowest voltage from becoming normal and then immediately dropping below the over-discharge cutoff voltage in the subsequent bottom balancing, the bottom balancing cutoff threshold should be set higher than the general over-discharge cutoff voltage by a safety margin. For example, for lithium-ion batteries, the over-discharge cutoff voltage is generally set to 2.5V, and the nominal value is 3.2V. However, many bottom balancings are required to increase the voltage from 2.5V to 3.2V. Therefore, the bottom balancing cutoff threshold can be set to 2. 8V, only charge the battery cell with the lowest voltage to 2.8V first. When the new battery cell with the lowest voltage is replaced for bottom balancing, energy will not be extracted to charge the new battery cell with the lowest voltage, causing it to drop below the over-discharge cut-off voltage all of a sudden. This can avoid the voltage oscillation phenomenon caused by the voltage of the battery cell with the lowest voltage just rising to normal after bottom balancing and then falling below the over-discharge protection cut-off threshold. Also, other batteries with too low voltage will not be discharged too many times because of the process of constantly processing the battery cell with the lowest voltage to the bottom balancing threshold.

[0092] The control circuit structure provided in the embodiment of the utility model is based on Figure 5 and Figure 6 It explains that 16 battery cells are connected in series, and the primary winding is changed from a single winding group of the traditional structure to a combination of 4 winding groups. In the top balancing of system charging, adaptive judgment and control are used to transfer energy from the battery cell with the highest voltage to the group with the lowest voltage. In the bottom balancing of system discharging, adaptive judgment and control are used to transfer energy from the group with the highest voltage to the battery cell with the lowest voltage.

[0093] In the embodiment of the utility model, the main control unit 150 is also used to control the switch states of the second switch and the first switch through the driving unit 140 when the maximum voltage difference among the N battery cells is greater than or equal to the bottom balancing start threshold, thereby controlling the battery pack with the highest voltage among the i battery packs to be turned on to magnetize the magnetic core, and then controlling the battery cell with the lowest voltage among the N battery cells to be used as the bottom balancing battery cell for demagnetization. As shown in the example of 16 battery cells above, the battery cell BAT_7 is the battery cell with the lowest battery cell voltage, so in the embodiment of the utility model, the battery cell BAT_7 is the bottom balancing battery cell.

[0094] In the embodiment of the utility model, the main control unit 150 is also used to control the switch states of the second switch and the first switch through the driving unit 140 when the voltage of the bottom balancing cell is less than the bottom balancing end threshold, thereby controlling the battery pack with the highest voltage among the i battery packs to be turned on to magnetize the magnetic core, and then controlling the battery pack with the lowest voltage among the N battery packs to continue to discharge magnetism as the bottom balancing cell. As shown in the example of 16 battery cells above, when the voltage of the battery cell BAT_7 is less than the bottom balancing end threshold, the switch states of the second switch and the first switch are controlled by the driving unit 140, thereby controlling the battery pack with the highest voltage among the i battery packs to be turned on to magnetize the magnetic core, and then controlling the bottom balancing cell to continue to discharge magnetism. If the voltage of the battery cell BAT_7 is greater than or equal to the bottom balancing end threshold, the control circuit ends this bottom balancing control, restarts the next round of bottom balancing start judgment, and then re-determines a bottom balancing cell.

[0095] When all the cells are below the initially set bottom balancing threshold, the bottom balancing threshold is set to the average voltage of all the cells so that all the cells can have the same voltage after bottom balancing. A "safety margin" can be retained as before for hysteresis control to avoid voltage oscillation during balancing. Since the above example can be used as an example, I will not go into details.

[0096] The previous section analyzed the methods of system charging and discharging. The following section analyzes the system when it is at rest. This may be the case, for example, when the system is discharging for a while while the vehicle is driving. After the vehicle stops, the battery capacity is still very high and has not yet reached the state where charging is required, or the scheduled charging time has not yet arrived. It may also be that the battery has been placed in the warehouse for a long time. At this time, the voltages of the various cells may not be consistent. When the battery is taken out of rest or restarted, what needs to be ensured is that the system can provide the best discharge endurance when it is immediately discharged. Therefore, the battery in rest can periodically adopt the same bottom balancing method as the system in discharge, so that when the system enters the discharge state at any time from rest, all cells are maintained in the best discharge state with balanced voltage.

[0097] In the control circuit provided by the present invention, when implementing top balancing, the main control unit 150 uses the characteristics of discontinuous conduction mode (DCM) to turn on the first switch connected to the top balancing cell with the highest single cell voltage in the first half of the DCM cycle, so that it is in an on state, to achieve magnetization of the magnetic core, that is, to transfer the energy of the top balancing cell, and then close the first switch connected to the top balancing cell in the second half of the DCM cycle, so that it is in an off state, and control the second switch connected to the battery pack with the lowest voltage among the i battery packs to be turned on, so that it is in an on state, to achieve demagnetization of the magnetic core to the battery pack with the lowest voltage among the i battery packs, that is, to achieve the transfer of energy from the magnetic core to the battery pack with the lowest voltage among the i battery packs, thereby avoiding a wrong and harmful balancing control process of controlling the voltage of the battery with too high voltage to be higher; and, in the control circuit provided by the present invention, when implementing bottom balancing, the main control unit 150 uses the characteristics of discontinuous conduction mode (DCM) to turn on the first switch connected to the top balancing cell with the highest single cell voltage in the first half of the DCM cycle, so that it is in an off state, and control the second switch connected to the battery pack with the lowest voltage among the i battery packs to be turned on, so that it is in an on state, thereby achieving demagnetization of the magnetic core to the battery pack with the lowest voltage among the i battery packs, that is, to achieve the transfer of energy from the magnetic core to the battery pack with the lowest voltage among the i battery packs, thereby avoiding a wrong and harmful balancing control process of controlling the voltage of the battery with too high voltage to be higher; and In the first half of the DCM cycle, the second switch of the battery pack with the highest voltage among the i battery packs is turned on to magnetize the magnetic core, that is, to transfer the energy of the battery pack with the highest voltage among the i battery packs. Then, in the second half of the DCM cycle, the second switch of the battery pack with the highest voltage among the i battery packs is turned off to be disconnected, and the first switch connected to the battery cell with the lowest voltage among the N battery cells is controlled to be turned on to be turned on, so that the battery cell with the lowest voltage among the N battery cells is used as the bottom balancing battery cell for demagnetization, thereby avoiding an erroneous and harmful balancing control process in which the voltage of the battery that is already too low is controlled to be even lower.

[0098] In the description of the present invention, it should be understood that the terms "coaxial", "bottom", "one end", "top", "middle", "the other end", "upper", "one side", "top", "inside", "front", "center", "both ends" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0099] In addition, the terms "first", "second", "third" and "fourth" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first", "second", "third" and "fourth" may explicitly or implicitly include at least one of such features.

[0100] In the present utility model, unless otherwise clearly stipulated and limited, the terms such as "installation", "setting", "connection", "fixation" and "screw-on" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integrated connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. Unless otherwise clearly defined, ordinary technicians in this field can understand the specific meanings of the above terms in the utility model according to the specific circumstances.

[0101] It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element.

[0102] Finally, it should be noted that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can still modify the technical solutions described in the above embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A control circuit for actively balancing a battery, characterized in that: A transformer is provided, wherein the transformer comprises a magnetic core, a high-voltage primary winding and N low-voltage secondary windings wound around the magnetic core; and The control circuit further includes N first switches and N battery cells connected in series, the N battery cells are evenly divided into N battery cells one by one, the N first switches are evenly divided into the N battery cells one by one, and the N low-voltage secondary windings are connected to the N battery cells one by one; In each of the battery cells, the battery cell is connected in series with the low-voltage secondary winding corresponding to the battery cell to which the battery cell belongs through the first switch in the battery cell to which the battery cell belongs; The N battery cells are divided into i battery groups, i is an integer greater than or equal to 2, the high-voltage primary windings are divided into i battery groups, and each of the i battery groups corresponds to one high-voltage primary winding; the control circuit further includes i second switches, and the i battery groups are connected to the i high-voltage primary windings through different second switches; and, The control circuit further includes an analog-to-digital conversion module, a driving unit and a main control unit, wherein the analog-to-digital conversion module includes N input terminals, and the N input terminals of the analog-to-digital conversion module are connected to the N battery cells in a one-to-one correspondence; The main control unit is connected to the analog-to-digital conversion module to collect the voltage of each of the N battery cells through the analog-to-digital conversion module; The driving unit is connected to the i second switches and the N first switches, and the main control unit is connected to the driving unit to control the switching states of the second switch and the first switch through the driving unit, thereby controlling the battery cell with the highest voltage among the N battery cells to be turned on and magnetize the magnetic core as the top balancing battery cell, and then controlling the battery cell with the lowest voltage among the i battery groups to demagnetize; and the main control unit controls the switching states of the second switch and the first switch through the driving unit, thereby controlling the battery cell with the highest voltage among the i battery groups to be turned on and magnetize the magnetic core, and then controlling the battery cell with the lowest voltage among the N battery cells to demagnetize as the bottom balancing battery cell.

2. The control circuit for active battery balancing according to claim 1, characterized in that: The N battery cells are equally divided into i battery groups, the high-voltage primary winding is divided into i high-voltage primary windings, and the i battery groups are respectively connected to the i high-voltage primary windings one-to-one through different second switches; or, the number of battery cells in each of the i-1 battery groups is set to be the same, and the number of battery cells in the i-th battery group is the quotient of N divided by i plus the remainder.

3. The control circuit for active battery balancing according to claim 2, characterized in that: The N battery cells are 16 battery cells, and the i battery packs are 4 battery packs.

4. The control circuit for active battery balancing according to claim 1, characterized in that: The main control unit is further used to control the switch states of the second switch and the first switch through the driving unit, and then when the maximum voltage difference among the N battery cells is greater than or equal to the top balancing start threshold, control the battery cell with the highest voltage among the N battery cells to be turned on and serve as the top balancing battery cell to magnetize the magnetic core, and then control the battery pack with the lowest voltage among the i battery packs to discharge magnetism; The main control unit is further used to control the switching states of the second switch and the first switch through the driving unit when the voltage of the top balancing cell is greater than the top balancing end threshold, thereby controlling the top balancing cell to continue magnetizing the magnetic core, and then controlling the battery pack with the lowest voltage among the i battery packs to discharge magnetism.

5. The control circuit for active battery balancing according to claim 1, characterized in that: The main control unit is further configured to control the switch states of the second switch and the first switch through the driving unit when the maximum voltage difference among the N battery cells is greater than or equal to the bottom balancing start threshold, thereby controlling the battery pack with the highest voltage among the i battery packs to be turned on, so as to magnetize the magnetic core, and then control the battery cell with the lowest voltage among the N battery cells to serve as the bottom balancing battery cell for demagnetization; The main control unit is further used to control the switching states of the second switch and the first switch through the driving unit when the voltage of the bottom balancing cell is less than the bottom balancing end threshold, thereby controlling the battery pack with the highest voltage among the i battery packs to be turned on to magnetize the magnetic core, and then controlling the battery cell with the lowest voltage among the N battery cells to continue to serve as the bottom balancing cell for demagnetization.

6. The control circuit for active battery balancing according to claim 1, characterized in that: The first switch and the second switch are high-frequency switches respectively.

7. The control circuit for active battery balancing according to claim 1, characterized in that: The main control unit and the driving unit are single chip microcomputers.

8. The control circuit for active battery balancing according to claim 1, characterized in that: The analog-to-digital conversion module includes a high-precision analog-to-digital converter.

9. The control circuit for active battery balancing according to claim 1, characterized in that: The analog-to-digital conversion module comprises a MUX multiplexing device, a differential amplifier module and an analog-to-digital converter connected in series.

10. The control circuit for active battery balancing according to claim 1, characterized in that: The first switch and the second switch are metal oxide semiconductor field effect transistors.

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