Lithium battery active equalization control system and method based on passive equalization

Abstract

The invention discloses a lithium battery active equalization control system and method based on passive equalization, and belongs to the technical field of battery equalization. Comprising a battery pack, the battery pack comprises N battery cells which are sequentially connected in series, and an acquisition node is arranged between every two adjacent connected battery cells; the analog front-end chip comprises N + 1 detection ports, the first detection port is connected with the negative electrode of the battery cell located at the head end, the N + 1 detection port is connected with the positive electrode of the battery cell located at the tail end, and the other detection ports are sequentially connected with the corresponding acquisition nodes; n analog switch control parts, wherein one analog switch control part is connected in parallel with one battery cell; n magnetic induction coil groups, wherein one magnetic induction coil group is connected with one analog switch control part; wherein N is a positive integer. The beneficial effects of the technical scheme are that the magnetic induction coil group and the analog switch control circuit are added, and the magnetic induction coil group is utilized to transfer electric energy, so that the active equalization function is achieved, the control is simple, the used components are few, and the cost is saved.

Description

Technical Field

[0001] The present invention relates to the technical field of battery balancing, and in particular to a lithium battery active balancing control system and method. Background Art

[0002] Lithium-ion battery cells need to operate within a specific State of Charge (SOC) range to avoid damage. Therefore, in order to maximize the life of the battery cells, all cells must be kept within the specified SOC range. Figure 1 The battery pack includes a first battery cell A1, a second battery cell A2, and a third battery cell A3 connected in series in sequence. Figure 2 When the first battery cell A1 reaches the lower limit of SOC, the discharge of the entire battery pack stops. Figure 3 When the third battery cell A3 reaches the upper limit of SOC, the charging of the entire battery pack stops.

[0003] Reference Figure 4 In order to make the state of all series cells (SOC) consistent, active balancing technology significantly improves energy efficiency by transferring the energy of high-energy cell A3 to low-energy cell A1. Existing active balancing methods include active balancing methods based on bidirectional flyback converters, which usually require many transformers (such as Figure 5 The first transformer T1, the second transformer T2) and the switch control circuit in the embodiment of the present invention will result in a large volume and high cost of the battery pack solution with a high number of strings; Figure 6 The active balancing method of the switch matrix plus transformer only requires a third transformer T3. The disadvantage is that it requires more switch control circuits, the logic control is more complicated, and it will also cause the active balancing solution of the battery pack with a high number of strings to be large in size and high in cost. Figure 7 The active balancing method of the buck-boost active balancer provides bidirectional charge movement between two adjacent battery cells through buck balancing mode or boost balancing mode. The control circuit is simple and the cost is low, but the disadvantage is that energy can only be transferred between adjacent battery cells. For the case where inconsistent battery cells are not adjacent, energy needs to be transferred multiple times, the logic control is complex, and the balancing time is long. Summary of the invention

[0004] The purpose of the present invention is to provide a lithium battery active balancing control system based on passive balancing to solve the above technical problems;

[0005] The present invention also aims to provide a lithium battery active equalization control method based on passive equalization to solve the above technical problems;

[0006] A lithium battery active balancing control system based on passive balancing, comprising:

[0007] A battery pack, wherein the battery pack comprises N battery cells connected in series, and a collection node is provided between adjacent battery cells;

[0008] An analog front-end chip, the analog front-end chip comprising N+1 detection ports, wherein the first detection port is connected to the negative electrode of the battery cell at the very beginning, the N+1th detection port is connected to the positive electrode of the battery cell at the very end, and the remaining detection ports are sequentially connected to the corresponding acquisition nodes;

[0009] N analog switch control units, one of which is connected in parallel to one of the cells, for controlling the cell to charge and discharge;

[0010] N magnetic induction coil groups, one of the magnetic induction coil groups is connected to one of the analog switch control units, and is used to transfer the electrical energy of the battery core;

[0011] Wherein N is a positive integer.

[0012] Preferably, the magnetic induction coil group includes:

[0013] A first balancing coil is arranged on one side of the magnetic core;

[0014] The second balancing coil is arranged on the other side of the magnetic core.

[0015] Preferably, the analog switch control unit includes:

[0016] a first insulated gate field effect transistor, wherein a source of the first insulated gate field effect transistor is connected to a first end of the first balancing coil and a positive electrode of the battery cell, and a drain of the first insulated gate field effect transistor is connected to a first end of the second balancing coil;

[0017] a second insulated gate field effect transistor, wherein a drain of the second insulated gate field effect transistor is connected to the second end of the first balancing coil, and a source of the second insulated gate field effect transistor is connected to the second end of the second balancing coil and the negative electrode of the battery cell;

[0018] a third insulated gate field effect transistor, wherein the drain of the third insulated gate field effect transistor is connected to the gate of the first insulated gate field effect transistor, and the gate of the third insulated gate field effect transistor is connected to the drain of the first insulated gate field effect transistor via a first resistor connected in series;

[0019] a fourth insulated gate field effect transistor, wherein the drain of the fourth insulated gate field effect transistor is connected to the gate of the second insulated gate field effect transistor, and the gate of the fourth insulated gate field effect transistor is connected between the first resistor and the gate of the third insulated gate field effect transistor;

[0020] A second resistor, wherein a first end of the second resistor is connected to the gate of the fourth insulated gate field effect transistor, and a second end of the second resistor is connected to the source of the fourth insulated gate field effect transistor.

[0021] Preferably, the source of the third insulated gate field effect transistor is connected to the N+1th detection port, and the source of the fourth insulated gate field effect transistor is connected to the Nth detection port.

[0022] Preferably, the analog switch control unit includes:

[0023] a first diode, wherein a cathode of the first diode is connected to a first end of the first balancing coil and a positive electrode of the battery cell, and an anode of the first diode is connected to a first end of the second balancing coil;

[0024] A second insulated gate field effect transistor, wherein the drain of the second insulated gate field effect transistor is connected to the second end of the first balancing coil, and the source of the second insulated gate field effect transistor is connected to the second end of the second balancing coil and the negative electrode of the battery cell.

[0025] Preferably, the gate of the second insulated gate field effect transistor is connected to the Nth detection port.

[0026] Preferably, the first detection port is connected to the analog switch control unit located at the very beginning through a control line, the N+1th detection port is connected to the analog switch control unit located at the very end through a control line, and the remaining detection ports are respectively connected to two adjacent analog switch control units through two control lines.

[0027] Preferably, a collection resistor is connected to the front end of each detection port, the first detection port is connected to the negative electrode of the battery cell at the very beginning through the collection resistor, the N+1th detection port is connected to the positive electrode of the battery cell at the very end through the collection resistor, and the remaining detection ports are respectively connected to the corresponding collection nodes through the collection resistor.

[0028] Preferably, the ground terminal of the analog front-end chip is grounded, and the negative electrode of the battery cell at the front end is grounded.

[0029] A lithium battery active balancing control method based on passive balancing is used to control the lithium battery active balancing control system, comprising:

[0030] Step S1, collecting the real-time voltage of the battery cell through the analog front-end chip;

[0031] Step S2, the magnetic induction coil group generates an induced voltage at both ends of the battery cell, and determines whether the real-time voltage is higher than the induced voltage. If so, the battery cell discharges to the magnetic induction coil group through the analog switch control unit; if not, the magnetic induction coil group charges the battery cell through the analog switch control unit.

[0032] The beneficial effects of the present invention are: adding a magnetic induction coil group and an analog switch control circuit on the basis of an analog front-end chip used for passive balancing, utilizing the magnetic induction coil group to transfer electrical energy, thereby achieving the function of active balancing, with simple control, fewer components used, and cost savings. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the internal power distribution of a battery cell in the prior art;

[0034] Figure 2 It is a schematic diagram of the power distribution of the battery cell when the discharge stops in the prior art;

[0035] Figure 3 It is a schematic diagram of the power distribution of a battery cell when charging stops in the prior art;

[0036] Figure 4 It is a schematic diagram of active balancing of a battery pack in the prior art;

[0037] Figure 5 It is a schematic diagram of active balancing through a bidirectional flyback converter in the prior art;

[0038] Figure 6 It is a schematic diagram of the prior art for active balancing by means of a switch matrix plus a transformer;

[0039] Figure 7 It is a schematic diagram of active balancing by a boost / lower pressure active balancer in the prior art;

[0040] Figure 8 is a circuit diagram of the lithium battery active balancing control system of the present invention;

[0041] Fig. 9 is a circuit diagram of an analog switch control unit in one embodiment of the present invention;

[0042] Fig.10 is a circuit diagram of an analog switch control unit in another embodiment of the present invention;

[0043] Fig.11 It is a step diagram of the lithium battery active equalization control method of the present invention. DETAILED DESCRIPTION

[0044] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0045] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0046] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.

[0047] A lithium battery active balancing control system based on passive balancing, such as Figure 8 As shown, including

[0048] A battery pack P, the battery pack P includes N cells connected in series, and a collection node X is provided between adjacent connected cells;

[0049] The analog front-end chip AFE includes N+1 detection ports, wherein the first detection port is connected to the negative electrode of the battery cell at the front end, the N+1th detection port is connected to the positive electrode of the battery cell at the end, and the remaining detection ports are connected to the corresponding acquisition nodes X in sequence;

[0050] N analog switch control units K, one analog switch control unit K is connected in parallel to one battery cell, and is used to control the battery cell to charge and discharge;

[0051] N magnetic induction coil groups L, one magnetic induction coil group L is connected to an analog switch control unit K, and is used to transfer the electric energy of the battery cell;

[0052] Wherein N is a positive integer.

[0053] Specifically, the present invention provides a lithium battery active balancing control system based on passive balancing, wherein the detection port of the analog front-end chip AFE provides the functions of voltage detection and passive balancing input and output. A magnetic induction coil group L and an analog switch control circuit (analog switch control unit K) are added on the basis of the analog front-end chip AFE used for passive balancing, and the analog switch control circuit can be selected for different balancing applications and different balancing strategies. The magnetic induction coil group L is used to transfer electrical energy, thereby achieving the function of active balancing, and the overall control is simple, and the components used are few, saving costs.

[0054] In a preferred embodiment, the magnetic induction coil group L includes:

[0055] The first balancing coil L1 is arranged on one side of the magnetic core E;

[0056] The second balancing coil L2 is arranged on the other side of the magnetic core E.

[0057] Specifically, refer to Fig. 9 The first balancing coil L1 and the second balancing coil L2 are both excitation coils, and magnetic induction coils can be added or reduced according to different balancing applications and different balancing strategies.

[0058] The first end of the first balancing coil L1 is pin 1 , the second end of the first balancing coil L1 is pin 4 , the first end of the second balancing coil L2 is pin 2 , and the second end of the second balancing coil L2 is pin 3 .

[0059] In a preferred embodiment, referring to Fig. 9 , the analog switch control unit K includes,

[0060] A first insulated gate field effect transistor M1, wherein the source of the first insulated gate field effect transistor M1 is connected to the first end of the first balancing coil L1 and the positive electrode of the battery cell, and the drain of the first insulated gate field effect transistor M1 is connected to the first end of the second balancing coil L2;

[0061] A second insulated gate field effect transistor M2, wherein the drain of the second insulated gate field effect transistor M2 is connected to the second end of the first balancing coil L1, and the source of the second insulated gate field effect transistor M2 is connected to the second end of the second balancing coil L2 and the negative electrode of the battery cell;

[0062] A third insulated gate field effect transistor M3, wherein the drain of the third insulated gate field effect transistor M3 is connected to the gate of the first insulated gate field effect transistor M1, and the gate of the third insulated gate field effect transistor M3 is connected to the drain of the first insulated gate field effect transistor M1 via a first resistor R1 connected in series;

[0063] A fourth insulated gate field effect transistor M4, wherein the drain of the fourth insulated gate field effect transistor M4 is connected to the gate of the second insulated gate field effect transistor M2, and the gate of the fourth insulated gate field effect transistor M4 is connected between the first resistor R1 and the gate of the third insulated gate field effect transistor M3;

[0064] a second resistor R2, wherein a first end of the second resistor R2 is connected to a gate of a fourth insulated gate field effect transistor M4, and a second end of the second resistor R2 is connected to a source of the fourth insulated gate field effect transistor M4;

[0065] The source of the third insulated gate field effect transistor M3 is connected to the N+1th detection port, and the source of the fourth insulated gate field effect transistor M4 is connected to the Nth detection port.

[0066] Specifically, in the balanced discharge cycle, if the detection port of the VCx node is discharged, the analog front-end chip AFE controls the passive balanced switch inside VCx to open. At this time, there is no current in the initial stage of the magnetic induction coil group L, and the induced voltage is 0. Pin 2 is at a low level, the voltage of pin 6 is greater than the voltage of pin 5, the fourth insulated gate field effect transistor M4 and the second insulated gate field effect transistor M2 are turned on, the first insulated gate field effect transistor M1 and the third insulated gate field effect transistor M3 are turned off, and the positive electrode (VBx+) of the discharge cell VBx passes through the magnetic induction coil group L, and then through the second insulated gate field effect transistor M2 to the negative electrode (VBx-) of the cell VBx to form a loop, and discharge to the magnetic induction coil group L.

[0067] If multiple cells are balanced at the same time, the discharge cycle can charge other cells at the same time. The corresponding channel AFE passive balancing can be controlled to open, and multiple cells are discharged to the magnetic induction loop at the same time, and the magnetic induction coil group L generates a magnetic field. At this time, there is an induced voltage at both ends of all balanced cells.

[0068] In the discharge shutdown cycle, the discharge of the VCx section is closed, and the analog front-end chip AFE controls the passive balancing switch inside the VCx to be closed. If the VCx section is charged, the analog front-end chip AFE controls the passive balancing switch inside the detection port to be opened. At this time, there is current in the magnetic induction coil group L, and the induced voltage is relatively large. Pin 2 is at a high level, the voltage of pin 7 is less than the voltage of pin 8, the fourth insulated gate field effect transistor M4 and the second insulated gate field effect transistor M2 are closed, the first insulated gate field effect transistor M1 and the third insulated gate field effect transistor M3 are turned on, and the positive electrode of the charging battery VBx passes through the magnetic induction coil group L, and then through the first insulated gate field effect transistor M1 to the positive electrode (VBx+) of the battery VBx to form a loop, and the magnetic induction coil group L charges VBx.

[0069] If multiple batteries are charged at the same time, the AFE of the corresponding channel can be controlled to open passive balancing, and there will be induced voltage at both ends of all balancing cells, and the magnetic induction circuit will charge multiple batteries at the same time.

[0070] In a preferred embodiment, referring to Fig.10 , the analog switch control unit K includes,

[0071] A first diode D1, wherein a cathode of the first diode D1 is connected to a first end of the first balancing coil L1 and a positive electrode of the battery cell, and an anode of the first diode D1 is connected to a first end of the second balancing coil L2;

[0072] A second insulated gate field effect transistor M2, wherein the drain of the second insulated gate field effect transistor M2 is connected to the second end of the first balancing coil L1, and the source of the second insulated gate field effect transistor M2 is connected to the second end of the second balancing coil L2 and the negative electrode of the battery cell;

[0073] The gate of the second insulated gate field effect transistor M2 is connected to the Nth detection port.

[0074] Specifically, if the balancing strategy is a discharge-off cycle, all cells are charged simultaneously, and the first insulated gate field effect transistor M1 of the analog switch control unit K can be replaced with a diode, such as Fig.10 As shown, the magnetic induction coil group L releases electric energy through the first diode D1 to charge the corresponding channel battery cell.

[0075] In a preferred embodiment, the control line S is Figure 8 As shown by the red line in the middle, the first detection port VC1 is connected to the analog switch control unit K at the head end through a control line S, and the N+1th detection port VC(N+1) is connected to the analog switch control unit K at the end through a control line S. Fig. 9 The source of the third insulated gate field effect transistor M3 is connected to VCx, and the source of the fourth insulated gate field effect transistor M4 is connected to VC(x-1).

[0076] The remaining detection ports are connected to two adjacent analog switch control parts K through two control lines S respectively.

[0077] Specifically, the control line S is a logic control line, and a connection mode can be selected according to different equalization circuits and different equalization strategies.

[0078] In a preferred embodiment, a collection resistor RS is connected to the front end of each detection port, the first detection port is connected to the negative electrode of the battery cell at the very beginning through the collection resistor RS, the N+1th detection port is connected to the positive electrode of the battery cell at the very end through the collection resistor RS, and the remaining detection ports are connected to the corresponding collection nodes X through the collection resistor RS.

[0079] In a preferred embodiment, the ground terminal of the analog front-end chip AFE is grounded, and the negative electrode of the battery cell at the front end is grounded.

[0080] A lithium battery active balancing control method based on passive balancing, referring to Fig.11 , used to control the lithium battery active balancing control system, including,

[0081] Step S1, collecting the real-time voltage of the battery cell through the analog front-end chip AFE;

[0082] Step S2, the magnetic induction coil group L generates an induced voltage at both ends of the battery cell, and determines whether the real-time voltage is higher than the induced voltage. If so, the battery cell discharges to the magnetic induction coil group L through the analog switch control unit K. If not, the magnetic induction coil group L charges the battery cell through the analog switch control unit K.

[0083] Specifically, the present invention also provides a lithium battery active balancing control method based on passive balancing, the above circuit can be placed inside the battery management chip, and the magnetic induction coil group L is a component that generates a magnetic field through current excitation. By generating an induced voltage at both ends of the battery cell, the system can determine whether the power of the battery cell is in a balanced state by comparing the induced voltage with the battery cell voltage.

[0084] The magnetic induction coil group L adjusts the energy transfer through the electromagnetic induction principle, and can realize the energy transmission between the cells, thereby actively adjusting the voltage of different cells in the battery pack. The magnetic induction coil group L is used to transfer the electric energy. In the subsequent use process, the application limitation of the present invention is relatively small, and the balancing efficiency and accuracy are greatly improved.

[0085] The analog switch control unit K is used in this method to control the direction of current flow. If discharge is required, the analog switch control unit K directs the current to the magnetic induction coil; if charging is required, the analog switch control unit K changes the direction of the current and charges the battery cell. The fast response and precise control of the analog switch control unit K can achieve energy balance between different battery cells, thereby improving the overall efficiency of the battery system.

[0086] Through active balancing control, the power of each cell in the battery pack can be effectively managed to avoid excessive power deviation between cells. This can not only reduce battery loss, but also effectively improve the overall energy output and utilization efficiency of the battery pack.

[0087] When the voltage of each cell in the battery pack is balanced, the working state of each cell is more stable, avoiding the accelerated aging of some cells due to excessive discharge or charging. Balanced control can extend the cycle life of the battery and reduce the premature degradation problem caused by unbalanced cells.

[0088] The above description is only a preferred embodiment of the present invention, and does not limit the implementation mode and protection scope of the present invention. For those skilled in the art, it should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the description and illustrations of the present invention should be included in the protection scope of the present invention.

Claims

1. A lithium battery active balancing control system based on passive balancing, characterized in that: include, A battery pack (P), the battery pack (P) comprising N cells connected in series, with a collection node (X) being provided between adjacent cells; An analog front-end chip (AFE), wherein the analog front-end chip (AFE) comprises N+1 detection ports, wherein the first detection port is connected to the negative electrode of the battery cell at the head end, the N+1th detection port is connected to the positive electrode of the battery cell at the end end, and the remaining detection ports are sequentially connected to the corresponding acquisition nodes (X); N analog switch control units (K), one of the analog switch control units (K) is connected in parallel to one of the battery cells, and is used to control the battery cell to charge and discharge; N magnetic induction coil groups (L), one of the magnetic induction coil groups (L) is connected to one of the analog switch control units (K) for transferring the electrical energy of the battery core; Wherein N is a positive integer.

2. The lithium battery active balancing control system based on passive balancing according to claim 1, characterized in that: The magnetic induction coil group (L) comprises: A first balancing coil (L1) is arranged on one side of the magnetic core (E); The second balancing coil (L2) is arranged on the other side of the magnetic core (E).

3. The lithium battery active balancing control system based on passive balancing according to claim 2, characterized in that: The analog switch control unit (K) includes: a first insulated gate field effect transistor (M1), wherein a source electrode of the first insulated gate field effect transistor (M1) is connected to a first end of the first balancing coil (L1) and a positive electrode of the battery core, and a drain electrode of the first insulated gate field effect transistor (M1) is connected to a first end of the second balancing coil (L2); a second insulated gate field effect transistor (M2), wherein a drain of the second insulated gate field effect transistor (M2) is connected to the second end of the first balancing coil (L1), and a source of the second insulated gate field effect transistor (M2) is connected to the second end of the second balancing coil (L2) and the negative electrode of the battery cell; a third insulated gate field effect transistor (M3), wherein the drain of the third insulated gate field effect transistor (M3) is connected to the gate of the first insulated gate field effect transistor (M1), and the gate of the third insulated gate field effect transistor (M3) is connected to the drain of the first insulated gate field effect transistor (M1) via a first resistor (R1) connected in series; a fourth insulated gate field effect transistor (M4), wherein the drain of the fourth insulated gate field effect transistor (M4) is connected to the gate of the second insulated gate field effect transistor (M2), and the gate of the fourth insulated gate field effect transistor (M4) is connected between the first resistor (R1) and the gate of the third insulated gate field effect transistor (M3); A second resistor (R2), wherein a first end of the second resistor (R2) is connected to a gate of the fourth insulated gate field effect transistor (M4), and a second end of the second resistor (R2) is connected to a source of the fourth insulated gate field effect transistor (M4).

4. The lithium battery active balancing control system based on passive balancing according to claim 3, characterized in that: The source of the third insulated gate field effect transistor (M3) is connected to the N+1th detection port, and the source of the fourth insulated gate field effect transistor (M4) is connected to the Nth detection port.

5. The lithium battery active balancing control system based on passive balancing according to claim 2, characterized in that: The analog switch control unit (K) includes: a first diode (D1), wherein a cathode of the first diode (D1) is connected to a first end of the first balancing coil (L1) and a positive electrode of the battery cell, and an anode of the first diode (D1) is connected to a first end of the second balancing coil (L2); A second insulated gate field effect transistor (M2), wherein a drain of the second insulated gate field effect transistor (M2) is connected to the second end of the first balancing coil (L1), and a source of the second insulated gate field effect transistor (M2) is connected to the second end of the second balancing coil (L2) and the negative electrode of the battery cell.

6. The lithium battery active balancing control system based on passive balancing according to claim 5, characterized in that: The gate of the second insulated gate field effect transistor (M2) is connected to the Nth detection port.

7. The lithium battery active balancing control system based on passive balancing according to claim 1, characterized in that: The first detection port is connected to the analog switch control unit (K) at the very beginning via a control line (S), the N+1th detection port is connected to the analog switch control unit (K) at the very end via a control line (S), and the remaining detection ports are respectively connected to two adjacent analog switch control units (K) via two control lines (S).

8. The lithium battery active balancing control system based on passive balancing according to claim 1, characterized in that: A collection resistor (RS) is connected to the front end of each detection port, the first detection port is connected to the negative electrode of the battery cell at the very beginning through the collection resistor (RS), the N+1th detection port is connected to the positive electrode of the battery cell at the very end through the collection resistor (RS), and the remaining detection ports are respectively connected to the corresponding collection nodes (X) through the collection resistor (RS).

9. The lithium battery active balancing control system based on passive balancing according to claim 1, characterized in that: The ground terminal of the analog front end chip (AFE) is grounded, and the negative electrode of the battery cell at the front end is grounded.

10. A lithium battery active balancing control method based on passive balancing, characterized in that: A lithium battery active balancing control system for controlling any one of claims 1 to 9, comprising: Step S1, collecting the real-time voltage of the battery cell through the analog front-end chip (AFE); Step S2, the magnetic induction coil group (L) generates an induced voltage at both ends of the battery cell, and determines whether the real-time voltage is higher than the induced voltage. If so, the battery cell discharges to the magnetic induction coil group (L) through the analog switch control unit (K); if not, the magnetic induction coil group (L) charges the battery cell through the analog switch control unit (K).

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