Reconfigurable charging and discharging circuit with equalization function

Abstract

The invention relates to the technical field of lithium battery equalization, and discloses a reconfigurable charging and discharging circuit with an equalization function, the reconfigurable charging and discharging circuit comprises x battery units which are sequentially connected in series, each battery unit comprises a battery pack, a first switch and an equalization circuit, and the output positive electrode of the battery pack is electrically connected with the input end of the first switch; the equalization circuit is electrically connected with the battery pack and used for performing voltage equalization on the battery pack; the output negative electrode of the battery pack of each battery unit is also electrically connected with the output end of the first switch through a second switch; according to the invention, the battery pack of each battery unit is provided with the equalization circuit, so that the equalization between any batteries in the battery pack can be realized, the equalization path is reduced, and the equalization efficiency is improved; secondly, in the charging and discharging process, when the battery pack in the battery units needs to be equalized, the battery units needing to be equalized are isolated by controlling the on-off of the first switch and the second switch, the battery pack is prevented from being overcharged and overdischarged, and the service life of the battery pack is prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium battery equalization, and in particular to a reconfigurable charging and discharging circuit with an equalization function. Background Art

[0002] During the charging and discharging process of lithium batteries, balanced management of lithium batteries can reduce the inconsistency of single cells, improve lithium battery performance, extend lithium battery life, enhance lithium battery safety, improve lithium battery energy utilization and maintain system stability. It is a key link in lithium battery management.

[0003] According to different equalization methods, existing equalization circuits can be divided into passive equalization circuits and active equalization circuits.

[0004] The passive balancing circuit has the advantages of simple structure, simple control method and low cost, but it also has the problem of energy waste in the form of heat energy dissipation.

[0005] Although the active balancing circuit solves the energy waste problem of the passive balancing circuit, and can realize energy transfer between batteries and has the advantages of higher balancing efficiency, there are problems in the active balancing circuit such as complex balancing circuit structures, complex control methods, and different balancing paths and balancing efficiencies. It needs to be used according to different application scenarios.

[0006] In addition, in the existing active balancing circuit, the energy transfer balancing speed between adjacent single cells is fast, but as the number of batteries increases, the balancing efficiency is low. The energy transfer between any single cells can realize the energy transfer between any single cells, but only the energy transfer between a pair of batteries can be realized at any time. The energy transfer between the single cell to the whole and the whole to the single cell can avoid overcharging and over-discharging, but there is a balancing overlap, and the balancing efficiency is not high. Summary of the invention

[0007] In view of the shortcomings of the background technology, the present invention provides a reconfigurable charge and discharge circuit with a balancing function, and the technical problem to be solved is that the existing lithium batteries have the problems of low efficiency, complex structure and complex control method during balancing.

[0008] To solve the above technical problems, the present invention provides the following technical solutions: a reconfigurable charge and discharge circuit with a balancing function, comprising x battery cells connected in series in sequence, where x is a positive integer greater than 1; Each battery cell includes a battery pack, a first switch and a balancing circuit, wherein the battery pack includes an output positive electrode and an output negative electrode; the output positive electrode of the battery pack is electrically connected to the input end of the first switch; the battery cells are connected in series such that the output end of the first switch of the current-stage battery cell is electrically connected to the output negative electrode of the battery pack of the next-stage battery cell; the balancing circuit is electrically connected to the battery pack for voltage balancing of the battery pack; For each battery unit, the negative output electrode of the battery pack is also electrically connected to the output end of the first switch through the second switch.

[0009] In some embodiments, the output end of the first switch of the terminal battery unit is electrically connected to the output end of the third switch, and the input end of the third switch and the output negative electrode of the battery pack of the first terminal battery unit are used to be electrically connected to the charging device.

[0010] In some embodiments, the output end of the first switch of the terminal battery unit is electrically connected to the output end of the fourth switch, and the input end of the fourth switch and the output negative electrode of the battery pack of the first terminal battery unit are used to supply power to the electrical device.

[0011] In some embodiments, each battery group includes m batteries connected in series, where m is a positive integer greater than 1.

[0012] In a certain embodiment, the balancing circuit includes a capacitor C1 and m+1 first switch branches, and the m+1 node of the battery pack is electrically connected to the output ends of the m+1 first switch branches respectively; Along the series connection direction of the batteries in the battery pack, the input ends of the first switch branches at odd positions on the battery pack are electrically connected to one end of the capacitor C1, and the input ends of the first switch branches at even positions on the battery pack are electrically connected to the other end of the capacitor C1.

[0013] In some implementations, the first switch branch includes two MOS transistors N1 and N2 connected in series, the drain of the MOS transistor N1 is the input end of the first switch branch, and the source of the MOS transistor N2 is the output end of the first switch branch.

[0014] In a certain implementation manner, the balancing circuit includes an inductor L1, M-1 second switch branches, m-1 third switch branches, a MOS transistor N3, a MOS transistor N4, a diode D1, and a diode D2; The negative electrode of the first-end battery is electrically connected to the anode of the diode D1 and the source of the MOS tube N3, and the positive electrode of the terminal battery is electrically connected to the cathode of the diode D2 and the drain of the MOS tube N4; Except for the terminal battery, the positive electrode of each battery is electrically connected to an input end of a second switch branch and an output end of a third switch branch respectively; The output ends of all second switch branches, the cathode of the diode D1 and the source of the MOS tube N4 are electrically connected to one end of the inductor L1; The input ends of all the third switch branches, the anode of the diode D2 and the drain of the MOS transistor N3 are electrically connected to the other end of the inductor L1.

[0015] In a certain embodiment, the second switch branch includes a diode D3 and a MOS transistor N5, the anode of the diode D3 is the input end of the second switch branch, the cathode of the diode D3 is electrically connected to the drain of the MOS transistor N5, and the source of the MOS transistor N5 is the output end of the second switch branch; The third switch branch includes a diode D4 and a MOS transistor N6, the cathode of the diode D4 is the output end of the third switch branch, the anode of the diode D4 is electrically connected to the source of the MOS transistor N6, and the drain of the MOS transistor N6 is the input end of the third switch branch.

[0016] In one embodiment, the process of balancing the cells in a battery pack is as follows: S1: Get the voltage of m batteries; S2: Find the maximum battery voltage and the minimum battery voltage from the voltages of the m batteries; S3: Determine whether the difference between the maximum battery voltage and the minimum battery voltage is greater than a determination threshold. If the difference is greater than the determination threshold, execute step S4. Otherwise, terminate step S3 and stop balancing. S4: The electric energy is transferred from the battery with the highest battery voltage to the battery with the lowest battery voltage through the balancing circuit. After the transfer is completed, step S1 is executed.

[0017] In a certain implementation manner, the equalization process of the charge and discharge circuit during the discharge process is as follows: S11: obtaining the voltages of x battery packs; S12: Find the battery pack corresponding to the lowest voltage among the obtained voltages of the x battery packs; S13: isolating the battery pack found in step S12 by controlling the on and off of the first switch and the second switch; S14: Obtain the voltage of the remaining battery packs to be discharged, and find the maximum battery pack voltage; S15: Determine whether the maximum battery pack voltage found in step 1 is the same as the minimum voltage in step S12. If they are the same, execute step S16; otherwise, execute step S12. S16: Determine whether the balanced discharge needs to be terminated. If the balanced discharge does not need to be terminated, execute step S11. Otherwise, terminate step S16. The balancing process of the charge and discharge circuit during the charging process is as follows: S21: Obtain the voltage of x battery packs; S22: taking the highest voltage among the x battery packs as a reference, charging the battery pack with the lowest voltage among the x battery packs in sequence by controlling the on and off of the first switch and the second switch; S23: Determine whether the highest voltage and the lowest voltage among the voltages of the x battery packs are the same, if they are the same, execute step S24, otherwise continue to execute step S22; S24: Detect the power of the battery pack; S25: Determine whether the power of the battery pack reaches the charging stop threshold, if not, execute step S26, otherwise, end step S25; S26: charging the battery pack; S27: Return to step S24.

[0018] Compared with the prior art, the present invention has the following beneficial effects: for the circuit of the present invention, firstly, each battery unit is provided with a balancing circuit for its own battery pack, so that balancing between any batteries in the battery pack can be achieved, thereby reducing the balancing path and improving the balancing efficiency; Secondly, by setting the first switch and the second switch, during the charging and discharging process, when the battery pack in the battery unit needs to be balanced, the battery unit that needs to be balanced can be isolated by controlling the on and off of the first switch and the second switch, thereby effectively avoiding overcharging and over-discharging of the battery pack and improving the service life of the battery pack. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a circuit diagram of the present invention in an embodiment; Figure 2 is a first circuit diagram of the equalization circuit in the embodiment; Figure 3 FIG. 4 is a second circuit diagram of the equalizing circuit in the embodiment. DETAILED DESCRIPTION

[0020] The present invention will now be described in further detail with reference to the accompanying drawings. These drawings are simplified schematic diagrams, which only illustrate the basic structure of the present invention in a schematic manner, and therefore only show the components related to the present invention.

[0021] like Figure 1 As shown, a reconfigurable charge-discharge circuit with a balancing function provided in this embodiment includes x battery cells 1 connected in series in sequence, where x is a positive integer greater than 1; wherein the number of x is set according to actual needs and is not limited here, and illustratively, x can be 3, 5, 9 or 11; Specifically, in Figure 1 In the embodiment, each battery unit 1 includes a battery pack 11, a first switch and a balancing circuit 12, the battery pack 11 includes an output positive electrode and an output negative electrode, Figure 1In the x battery cells 1, the first switches are switch K 2 , switch K 4 and K 2x ; More specifically, the output positive electrode of the battery pack 11 is electrically connected to the input end of the first switch; the series connection of the battery cells 1 is such that the output end of the first switch of the current-stage battery cell 1 is electrically connected to the output negative electrode of the battery pack 11 of the next-stage battery cell 1; the balancing circuit 12 is electrically connected to the battery pack 11 for voltage balancing of the battery pack 11; For each battery unit 1, the output negative electrode of the battery pack 11 is also electrically connected to the output end of the first switch through the second switch; Figure 1 In the example, all second switches are denoted as switch K. 1 , switch K 3 and switch K 2x-1 .

[0022] In actual use, for the circuit of the present invention, each battery unit 1 is provided with a balancing circuit 12 for its own battery pack 11, so that balancing between any batteries in the battery pack 11 can be achieved, thereby reducing the balancing path and improving the balancing efficiency; Secondly, by setting the first switch and the second switch, during the charging and discharging process, when the battery pack 11 in the battery unit 1 needs to be balanced, the battery unit that needs to be balanced can be isolated by controlling the on and off of the first switch and the second switch, thereby effectively avoiding overcharging and over-discharging of the battery pack and improving the service life of the battery pack.

[0023] Furthermore, in this embodiment, if Figure 1 As shown, the output end of the first switch of the terminal battery unit 1 is electrically connected to the output end of the third switch Kb, and the input end of the third switch Kb and the output negative electrode of the battery pack 11 of the head-end battery unit 1 are used to be electrically connected to the charging device 2.

[0024] In actual use, whether to charge the battery unit 1 is controlled by controlling the on-off of the third switch Kb.

[0025] Furthermore, in this embodiment, if Figure 1 As shown, the output end of the first switch of the terminal battery unit 1 is electrically connected to the output end of the fourth switch Ky, and the input end of the fourth switch Ky and the output negative electrode of the battery pack 11 of the head-end battery unit 1 are used to supply power to the electrical device 3.

[0026] In actual use, whether to charge the battery unit 1 is controlled by controlling the on-off of the third switch Kb.

[0027] In this embodiment, each battery pack 11 includes m batteries connected in series, where m is a positive integer greater than 1, and the number of m is set according to actual needs and is not limited here. For example, m can be 3, 5, 9 or 11.

[0028] The circuit of the first equalization circuit 12 in this embodiment is described as follows: like Figure 2 As shown, the balancing circuit 12 includes a capacitor C1 and m+1 first switch branches 120, and the m+1 node of the battery pack 11 is electrically connected to the output ends of the m+1 first switch branches 120 respectively; Along the series connection direction of the batteries in the battery pack 11, the input ends of the first switch branches 120 at odd positions on the battery pack 11 are electrically connected to one end of the capacitor C1, and the input ends of the first switch branches 120 at even positions on the battery pack are electrically connected to the other end of the capacitor C1.

[0029] In actual use, by controlling the on / off of the corresponding first switch branch 120 , the energy transfer between the high-voltage battery and the low-voltage battery in the battery pack 11 can be controlled to achieve battery balancing in the battery pack 11 .

[0030] More specifically, in Figure 1 In the embodiment, the first switch branch 120 includes two MOS transistors N1 and N2 connected in series, the drain of the MOS transistor N1 is the input end of the first switch branch 120 , and the source of the MOS transistor N2 is the output end of the first switch branch 120 .

[0031] In addition, Figure 3 As shown, this embodiment also provides another structure of the equalization circuit, wherein Figure 3 The balancing circuit includes an inductor L1, M-1 second switch branches 121, m-1 third switch branches 122, a MOS transistor N3, a MOS transistor N4, a diode D1 and a diode D2; First end battery B 1 The negative electrode is electrically connected to the anode of diode D1 and the source of MOS tube N3 respectively, and the terminal battery B m The positive electrode is electrically connected to the cathode of the diode D2 and the drain of the MOS tube N4 respectively; Except for the terminal battery B m , the positive electrode of each battery is electrically connected to an input end of a second switch branch 121 and an output end of a third switch branch 122 respectively; The output ends of all second switch branches 121, the cathode of the diode D1 and the source of the MOS transistor N4 are electrically connected to one end of the inductor L1; The input ends of all the third switch branches 122 , the anode of the diode D2 , and the drain of the MOS transistor N3 are electrically connected to the other end of the inductor L1 .

[0032] In actual use, by controlling the on and off of the second switch branch 121 , the third switch branch 122 , the MOS tube N3 and the MOS tube N4 , the energy transfer between the high-voltage battery and the low-voltage battery in the battery pack 11 can be controlled to achieve battery balancing in the battery pack 11 .

[0033] Furthermore, the second switch branch 121 includes a diode D3 and a MOS transistor N5, the anode of the diode D3 is the input end of the second switch branch 121, the cathode of the diode D3 is electrically connected to the drain of the MOS transistor N5, and the source of the MOS transistor N5 is the output end of the second switch branch 121; The third switch branch 122 includes a diode D4 and a MOS transistor N6 . The cathode of the diode D4 is the output end of the third switch branch 122 . The anode of the diode D4 is electrically connected to the source of the MOS transistor N6 . The drain of the MOS transistor N6 is the input end of the third switch branch 122 .

[0034] In this embodiment, the process of balancing the batteries in the battery pack 11 is as follows: S1: Get the voltage of m batteries; S2: Find the maximum battery voltage and the minimum battery voltage from the voltages of the m batteries; S3: Determine whether the difference between the maximum battery voltage and the minimum battery voltage is greater than a determination threshold. If the difference is greater than the determination threshold, execute step S4. Otherwise, terminate step S3 and stop balancing. S4: The equalization circuit 12 transfers electric energy from the battery with the highest battery voltage to the battery with the lowest battery voltage. After the transfer is completed, step S1 is executed.

[0035] In this embodiment, the equalization process of the charge and discharge circuit during the discharge process is as follows: S11: obtaining the voltages of x battery packs 11; S12: Find the battery pack 11 corresponding to the lowest voltage among the obtained voltages of the x battery packs 11; S13: isolating the battery pack 11 found in step S12 by controlling the on and off of the first switch and the second switch; S14: obtaining the voltage of the remaining battery packs 11 to be discharged, and finding the maximum battery pack voltage; S15: Determine whether the maximum battery pack voltage found in step S14 is the same as the minimum voltage in step S12, if they are the same, execute step S16, otherwise execute step S12; S16: Determine whether the balanced discharge needs to be terminated. If the balanced discharge does not need to be terminated, execute step S11; otherwise, terminate step S16.

[0036] For example, taking the charging and discharging circuit including three battery cells 1 as an example, assuming that the battery groups 11 in the three battery cells 1 are P1, P2 and P3 respectively, and the voltages of the three battery groups 11 are UP1, UP2 and UP3 respectively, and UP3>UP2>UP1; When the electrical device 3 needs electricity, the reconfigurable switches K1, K4, K6, and Ky are turned on, and K2, K3, K5, and Kb are turned off, so as to isolate the battery pack P1 with the lowest voltage in the battery unit 1 from the discharge circuit, and the remaining battery units continue to discharge. When UP2 is consistent with UP1, the reconfigurable switches K1, K3, K6, and Ky are turned on, and K2, K4, K5, and Kb are turned off, so as to isolate the battery packs P1 and P2 from the discharge circuit. Similarly, until the voltages of all battery packs are consistent, the discharge is stopped to avoid over-discharge of the battery pack.

[0037] The balancing process of the charge and discharge circuit during the charging process is as follows: S21: Obtaining the voltages of x battery packs 11; S22: taking the highest voltage among the voltages of the x battery packs 11 as a reference, charging the battery pack with the lowest voltage among the x battery packs 11 in sequence by controlling the on and off of the first switch and the second switch; S23: determining whether the highest voltage and the lowest voltage among the voltages of the x battery packs 11 are the same, if they are the same, executing step S24, otherwise continuing to execute step S22; S24: Detecting the power level of the battery pack 11; S25: Determine whether the power of the battery pack 11 reaches the charging stop threshold, if not, execute step S26, otherwise, end step S25; S26: charging the battery pack; S27: Return to step S24.

[0038] For example, taking the charging and discharging circuit including three battery cells 1 as an example, assuming that the battery groups 11 in the three battery cells 1 are P1, P2 and P3 respectively, and the voltages of the three battery groups 11 are UP1, UP2 and UP3 respectively, and UP3>UP2>UP1; When the electrical appliance is not working, the charging conditions are met, and the reconfigurable switches K2, K3, K5, ..., Kb are turned on, and K1, K4, K6, Ky are turned off. The power supply device 2 charges the battery pack P1 with the lowest voltage until the voltage of the battery pack P1 is consistent with the voltage of the second-to-last battery pack P2. Then the reconfigurable switches K2, K4, K5, Kb are turned on, and K1, K3, K6, Ky are turned off. The power supply device 2 charges the battery packs P1 and P2 at the same time until the voltages of the battery packs P1 and P2 are consistent with the voltage of the battery pack P3. Similarly, until the voltages of all battery packs are consistent, the power supply device 2 charges the entire battery pack through K2, K4, K6, Kb, so that all battery packs can be fully charged at the same time to avoid overcharging of the battery pack.

[0039] The above is based on the present invention as an inspiration. Through the above description, relevant staff can make various changes and modifications without departing from the technical idea of ​​this invention. The technical scope of this invention is not limited to the content in the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A reconfigurable charge and discharge circuit with a balancing function, characterized in that: It includes x battery cells connected in series, where x is a positive integer greater than 1; Each battery cell includes a battery pack, a first switch and a balancing circuit, wherein the battery pack includes an output positive electrode and an output negative electrode; the output positive electrode of the battery pack is electrically connected to the input end of the first switch; the battery cells are connected in series such that the output end of the first switch of the current-stage battery cell is electrically connected to the output negative electrode of the battery pack of the next-stage battery cell; the balancing circuit is electrically connected to the battery pack for voltage balancing of the battery pack; For each battery unit, the output negative electrode of the battery pack is also electrically connected to the output end of the first switch through the second switch.

2. A reconfigurable charge-discharge circuit with balancing function according to claim 1, characterized in that: The output end of the first switch of the terminal battery unit is electrically connected to the output end of the third switch, and the input end of the third switch and the output negative electrode of the battery pack of the first terminal battery unit are used to be electrically connected to the power supplement device.

3. The reconfigurable charge-discharge circuit with equalization function according to claim 1, characterized in that: The output end of the first switch of the terminal battery unit is electrically connected to the output end of the fourth switch, and the input end of the fourth switch and the output negative electrode of the battery pack of the first terminal battery unit are used to supply power to the electrical equipment.

4. A reconfigurable charge-discharge circuit with a balancing function according to any one of claims 1 to 3, characterized in that: Each battery pack includes m batteries connected in series, where m is a positive integer greater than 1.

5. The reconfigurable charge-discharge circuit with balancing function according to claim 4, characterized in that: The balancing circuit includes a capacitor C1 and m+1 first switch branches, and the m+1 nodes of the battery pack are electrically connected to the output ends of the m+1 first switch branches respectively; Along the series connection direction of the batteries in the battery pack, the input ends of the first switch branches at odd positions on the battery pack are electrically connected to one end of the capacitor C1, and the input ends of the first switch branches at even positions on the battery pack are electrically connected to the other end of the capacitor C1.

6. The reconfigurable charge-discharge circuit with balancing function according to claim 5, characterized in that: The first switch branch includes two MOS transistors N1 and N2 connected in series. The drain of the MOS transistor N1 is the input end of the first switch branch, and the source of the MOS transistor N2 is the output end of the first switch branch.

7. The reconfigurable charge-discharge circuit with equalization function according to claim 4, characterized in that: The balancing circuit includes an inductor L1, M-1 second switch branches, m-1 third switch branches, a MOS transistor N3, a MOS transistor N4, a diode D1 and a diode D2; The negative electrode of the first-end battery is electrically connected to the anode of the diode D1 and the source of the MOS tube N3, and the positive electrode of the terminal battery is electrically connected to the cathode of the diode D2 and the drain of the MOS tube N4; Except for the terminal battery, the positive electrode of each battery is electrically connected to an input end of a second switch branch and an output end of a third switch branch respectively; The output ends of all second switch branches, the cathode of the diode D1 and the source of the MOS tube N4 are electrically connected to one end of the inductor L1; The input ends of all the third switch branches, the anode of the diode D2 and the drain of the MOS transistor N3 are electrically connected to the other end of the inductor L1.

8. The reconfigurable charge-discharge circuit with balancing function according to claim 7, characterized in that: The second switch branch includes a diode D3 and a MOS transistor N5, the anode of the diode D3 is the input end of the second switch branch, the cathode of the diode D3 is electrically connected to the drain of the MOS transistor N5, and the source of the MOS transistor N5 is the output end of the second switch branch; The third switch branch includes a diode D4 and a MOS transistor N6, the cathode of the diode D4 is the output end of the third switch branch, the anode of the diode D4 is electrically connected to the source of the MOS transistor N6, and the drain of the MOS transistor N6 is the input end of the third switch branch.

9. The reconfigurable charge-discharge circuit with equalization function according to claim 4, characterized in that: The process of balancing the cells in a battery pack is as follows: S1: Get the voltage of m batteries; S2: Find the maximum battery voltage and the minimum battery voltage from the voltages of the m batteries; S3: Determine whether the difference between the maximum battery voltage and the minimum battery voltage is greater than a determination threshold. If the difference is greater than the determination threshold, execute step S4. Otherwise, terminate step S3 and stop balancing. S4: The electric energy is transferred from the battery with the highest battery voltage to the battery with the lowest battery voltage through the balancing circuit. After the transfer is completed, step S1 is executed.

10. The reconfigurable charge-discharge circuit with equalization function according to claim 1, characterized in that: The equalization process of the charging and discharging circuit during the discharging process is as follows: S11: obtaining the voltages of x battery packs; S12: Find the battery pack corresponding to the lowest voltage among the obtained voltages of the x battery packs; S13: isolating the battery pack found in step S12 by controlling the on and off of the first switch and the second switch; S14: Obtain the voltage of the remaining battery packs to be discharged, and find the maximum battery pack voltage; S15: Determine whether the maximum battery pack voltage found in step 1 is the same as the minimum voltage in step S12. If they are the same, execute step S16; otherwise, execute step S12. S16: Determine whether the balanced discharge needs to be terminated. If the balanced discharge does not need to be terminated, execute step S11. Otherwise, terminate step S16. The balancing process of the charge and discharge circuit during the charging process is as follows: S21: Obtain the voltage of x battery packs; S22: taking the highest voltage among the x battery packs as a reference, charging the battery pack with the lowest voltage among the x battery packs in sequence by controlling the on and off of the first switch and the second switch; S23: Determine whether the highest voltage and the lowest voltage among the voltages of the x battery packs are the same, if they are the same, execute step S24, otherwise continue to execute step S22; S24: Detect the power of the battery pack; S25: Determine whether the power of the battery pack reaches the charging stop threshold, if not, execute step S26, otherwise, end step S25; S26: charging the battery pack; S27: Return to step S24.

Images