Lithium battery pack charging equalization circuit

Abstract

The invention discloses a lithium battery pack charging equalization circuit. The circuit comprises a basic Cuk converter, n-1 bridging capacitors, n-1 output expansion units and n lithium ion batteries, the basic Cuk converter comprises an inductor L1, a Lin, a capacitor C1, a capacitor Cin, a switch S1 and a diode D1. Compared with a traditional DC / DC converter circuit equalization structure, the lithium battery pack charging equalization circuit realizes automatic voltage equalization among battery units through bridging capacitors, does not need complex sampling and control algorithms, avoids the problem of terminal voltage imbalance caused by cross adjustment rate when a converter has multiple outputs, effectively reduces voltage deviation, and improves the reliability of the lithium battery pack charging equalization circuit. And the battery equalization precision is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium battery pack charging management, and in particular to a lithium battery pack charging equalization circuit. Background Art

[0002] In order to meet the performance requirements of energy storage systems, lithium-ion batteries usually need to be used in groups, but there are inconsistencies between different battery cells, such as differences in performance such as capacity, internal resistance, and voltage. These differences will reduce the capacity utilization of the battery pack, and will also cause overcharging and over-discharging of the battery, accelerate battery aging, and endanger the safety of the battery system. At present, lithium battery balancing technology is most effective in optimizing inconsistencies. Lithium battery balancing technology is mainly divided into passive balancing and active balancing. Passive balancing, also known as energy-consuming balancing, refers to consuming all the excess energy of lithium battery cells in the form of heat, but this method will cause large battery energy loss, and the high temperature environment caused by improper heat dissipation will damage the battery performance. Active balancing, as a non-energy-consuming balancing, refers to the transfer of energy through energy storage elements, thereby reducing the inconsistency of lithium battery packs and achieving energy balance of lithium batteries. Active balancing is a hot spot in battery balancing technology due to its high energy utilization and flexible energy transfer. Summary of the invention

[0003] The present invention provides a lithium battery pack charging equalization circuit, which is based on the equalization circuit of the converter, adopts a multi-output Cuk converter equalization topology structure, and realizes the terminal voltage equalization (sameness) of the lithium battery cells inside the lithium battery pack by adding a jumper capacitor between each output unit. Compared with the traditional DC / DC converter circuit equalization structure, the circuit of the present invention realizes automatic voltage equalization between lithium battery cells through the jumper capacitor, does not require complex sampling and control algorithms, and avoids the terminal voltage imbalance problem caused by the cross-regulation rate of the converter when there are multiple outputs, effectively reduces voltage deviation, and improves the equalization accuracy of lithium batteries.

[0004] The technical solution adopted by the present invention is:

[0005] A lithium battery pack charging equalization circuit, the circuit comprising a basic Cuk converter, n-1 cross-connected capacitors, n-1 output expansion units, and n lithium-ion batteries;

[0006] The basic Cuk converter includes an inductor L 1 , L in , capacitor C 1 , C in , switch S 1 and diode D 1 ;

[0007] DC input source u in Positive connection inductor L in One end, inductor Lin The other end is connected to the switch S 1 Drain, capacitor C in One end, capacitor C in The other end is connected to diode D 1 Anode, inductor L 1 One end, inductor L 1 The other end is connected to capacitor C 1 One end, capacitor C 1 The other end is connected to diode D 1 Cathode, switch S 1 Source and DC input source u in cathode;

[0008] In n-1 output expansion units:

[0009] The first output expansion unit includes an inductor L 2 , capacitor C 2 、Diode D 2 ; Among them, the inductor L 2 One end is connected to diode D 2 Anode, inductance L 2 The other end is connected to capacitor C 2 One end, capacitor C 2 The other end is connected to diode D 2 cathode;

[0010] The second output expansion unit includes an inductor L 3 , capacitor C 3 、Diode D 3 ; Among them, the inductance L 3 One end is connected to diode D 3 Anode, inductance L 3 The other end is connected to capacitor C 3 One end, capacitor C 3 The other end is connected to diode D 3 cathode;

[0011] The third output expansion unit includes an inductor L 4 , capacitor C 4 、Diode D 4 ; Among them, the inductor L 4 One end is connected to diode D 4 Anode, inductance L 4 The other end is connected to capacitor C 4 One end, capacitor C 4 The other end is connected to diode D 4 cathode;

[0012] ... and so on.

[0013] The n-1th output expansion unit includes an inductor Ln , capacitor C n 、Diode D n ; Among them, the inductor L n One end is connected to diode D n Anode, inductance L n The other end is connected to capacitor C n One end, capacitor C n The other end is connected to diode D n cathode.

[0014] Among n-1 jumper capacitors:

[0015] Capacitor C VB1 The upper end and the diode D 1 Anode connection, capacitor C VB1 The lower end and diode D 2 Anode connection;

[0016] Capacitor C VB2 The upper end and the diode D 2 Anode connection, capacitor C VB2 The lower end and diode D 3 Anode connection;

[0017] Capacitor C VB3 The upper end and the diode D 3 Anode connection, capacitor C VB3 The lower end and diode D 4 Anode connection;

[0018] ... and so on.

[0019] Capacitor C VB(n-1) The upper end and the diode D n-1 Anode connection, capacitor C VB(n-1) The lower end and diode D n Anode connection.

[0020] Lithium-ion battery B 1 The positive pole is connected to the capacitor C 1 The other end, diode D 1 Cathode, Li-ion Battery B 1 The negative pole is connected to the inductor L 1 The other end, capacitor C 1 one end;

[0021] Lithium-ion battery B 2 The positive pole is connected to the capacitor C 2 The other end, diode D 2 Cathode, Li-ion Battery B 2 The negative pole is connected to the inductor L 2 The other end, capacitor C 2 one end;

[0022] ... and so on.

[0023] Lithium-ion battery B n-1 The positive pole is connected to the capacitor C n-1 The other end, diode D n-1 Cathode, Li-ion Battery B n-1 The negative pole is connected to the inductor L n-1 The other end, capacitor C n-1 one end;

[0024] Lithium-ion battery B n The positive pole is connected to the capacitor C n The other end, diode D n Cathode, Li-ion Battery B n The negative pole is connected to the inductor L n The other end, capacitor C n one end;

[0025] Among n lithium-ion batteries:

[0026] Lithium-ion battery B 1 Positive electrode connected to lithium-ion battery B 2 Negative electrode, lithium-ion battery B 2 Positive electrode connected to lithium-ion battery B 3 Negative electrode, lithium-ion battery B 3 Positive electrode connected to lithium-ion battery B 4 Negative electrode, ... and so on, lithium-ion battery B n-1 Positive electrode connected to lithium-ion battery B n negative electrode.

[0027] The switch S 1 The gate of the controller is connected and its duty cycle can be varied between 0 and 1.

[0028] A charging equalization circuit for a lithium battery pack containing four battery cells, the circuit comprising a basic Cuk converter, three cross-connected capacitors, three output expansion units, and four lithium-ion batteries;

[0029] The basic Cuk converter includes an inductor L 1 , L in , capacitor C 1 , C in , switch S 1 and diode D 1 ;

[0030] DC input source u in Positive connection inductor L in One end, inductor L in The other end is connected to the switch S 1 Drain, capacitor C in One end, capacitor Cin The other end is connected to diode D 1 Anode, inductor L 1 One end, inductor L 1 The other end is connected to capacitor C 1 One end, capacitor C 1 The other end is connected to diode D 1 Cathode, switch S 1 Source and DC input source u in cathode;

[0031] 3 output expansion units:

[0032] The first output expansion unit includes an inductor L 2 , capacitor C 2 、Diode D 2 ; Among them, the inductor L 2 One end is connected to diode D 2 Anode, inductance L 2 The other end is connected to capacitor C 2 One end, capacitor C 2 The other end is connected to diode D 2 cathode;

[0033] The second output expansion unit includes an inductor L 3 , capacitor C 3 、Diode D 3 ; Among them, the inductor L 3 One end is connected to diode D 3 Anode, inductance L 3 The other end is connected to capacitor C 3 One end, capacitor C 3 The other end is connected to diode D 3 cathode;

[0034] The third output expansion unit includes an inductor L 4 , capacitor C 4 、Diode D 4 ; Among them, the inductor L 4 One end is connected to diode D 4 Anode, inductance L 4 The other end is connected to capacitor C 4 One end, capacitor C 4 The other end is connected to diode D 4 cathode.

[0035] Among the 3 jumper capacitors:

[0036] Capacitor C VB1 The upper end and the diode D 1 Anode connection, capacitor C VB1 The lower end and diode D 2 Anode connection;

[0037] Capacitor C VB2 The upper end and the diode D 2 Anode connection, capacitor C VB2 The lower end and diode D 3 Anode connection;

[0038] Capacitor C VB3 The upper end and the diode D 3 Anode connection, capacitor C VB3 The lower end and diode D 4 Anode connection.

[0039] Lithium-ion battery B 1 The positive pole is connected to the capacitor C 1 The other end, diode D 1 Cathode, Li-ion Battery B 1 The negative pole is connected to the inductor L 1 The other end, capacitor C 1 one end;

[0040] Lithium-ion battery B 2 The positive pole is connected to the capacitor C 2 The other end, diode D 2 Cathode, Li-ion Battery B 2 The negative pole is connected to the inductor L 2 The other end, capacitor C 2 one end;

[0041] Lithium-ion battery B 3 The positive pole is connected to the capacitor C 3 The other end, diode D 3 Cathode, Li-ion Battery B 3 The negative pole is connected to the inductor L 3 The other end, capacitor C 3 one end;

[0042] Lithium-ion battery B 4 The positive pole is connected to the capacitor C 4 The other end, diode D 4 Cathode, Li-ion Battery B 4 The negative pole is connected to the inductor L 4 The other end, capacitor C 4 One end.

[0043] Of the 4 lithium-ion batteries:

[0044] Lithium-ion battery B 1 Positive electrode connected to lithium-ion battery B 2 Negative electrode, lithium-ion battery B 2 Positive electrode connected to lithium-ion battery B 3 Negative electrode, lithium-ion battery B3 Positive electrode connected to lithium-ion battery B 4 negative electrode.

[0045] When the switch S 1 When conducting, diode D 1 , D 2 , D 3 , D 4 Withstand reverse voltage cutoff, capacitor C in Through loop C in →L 2 →C VB1 →C in To capacitor C VB1 Charging, similarly, capacitor C in To capacitor C VB2 , C VB3 Charging, capacitor C 1 , C 2 , C 3 , C 4 Provides energy to lithium-ion battery packs;

[0046] When the switch S 1 When off, the diode D 1 , D 2 , D 3 , D 4 On, input source u in Through inductor L in To capacitor C in Charging, capacitor C VB1 , C VB2 , C VB3 Discharge, capacitor C 1 , C 2 , C 3 , C 4 Charging, inductance L 1 , L 2 , L 3 , L 4 Through diode D 1 , D 2 , D 3 , D 4 Provides energy to the lithium-ion battery pack.

[0047] Assume that the single cell B in the lithium-ion battery pack is connected in series 1 If the SOC is higher than the average value, the initial voltage u B1 >u B2 When switch S 1 When turned off, due to the cross-capacitor C VB1 The role of the diode D in the circuit 1 It is not turned on, and the current is first given to the capacitor C VB1 Discharge until the capacitor CVB1 The voltage u CVB1 rises to the output voltage u of the circuit B1 When the diode D 1 Start conducting.

[0048] Assuming the output capacitor C 1 If the output voltage ripple is large enough, it is much smaller than the cross-capacitor C VB1 The voltage ripple can be considered as u B1 The average voltage across the capacitor C VB1 In switch S 1 The peak voltage during the turn-off phase. Therefore, u B1 and u B2 The voltage deviation Δu is equal to the difference between the peak voltage and the average value, that is, the cross-capacitor C VB1 The voltage ripple peak-to-peak value is half. VB1 As the capacitance increases, the capacitor C VB1 The voltage ripple will become smaller and smaller, so the output voltage deviation will increase with C VB1 As the capacitance increases, u decreases. B1 and u B2 The voltage of capacitor C will be closer. VB1 , C VB2 , C VB3 When the voltage is large enough, the voltages of the lithium-ion battery cells are equal, thus achieving voltage balance among the lithium-ion battery cells in the lithium-ion battery pack.

[0049] The present invention provides a lithium battery pack charging equalization circuit, and the technical effects are as follows:

[0050] 1) The battery charging equalization circuit converter of the present invention solves the problem of terminal voltage imbalance caused by cross-regulation rate when there are multiple outputs, effectively reduces voltage deviation and improves battery equalization accuracy.

[0051] 2) Compared with the traditional DC / DC converter circuit balancing structure, the circuit of the present invention is simple, and automatic voltage balancing between battery cells is achieved through jumper capacitors, without the need for complex sampling and control algorithms.

[0052] 3) The circuit of the present invention is simple and only one switch is used to achieve the balance of the battery pack, thereby reducing the control difficulty and cost of the circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0054] Figure 1 It is a circuit schematic diagram of the present invention.

[0055] Figure 2 The circuit schematic diagram of the present invention is to realize the balancing of a battery pack with four battery units connected in series.

[0056] Figure 3 It is a circuit simulation diagram of the present invention to realize a battery pack balancing converter with four battery units connected in series. DETAILED DESCRIPTION

[0057] The present invention will be further described in detail below in conjunction with the accompanying drawings. Figure 2 As shown, a charging equalization circuit of a lithium battery pack containing four battery cells of the present invention is shown, and the circuit includes a basic Cuk converter, three cross-connected capacitors, three output expansion units, and four lithium-ion batteries, wherein:

[0058] The basic Cuk converter includes an inductor L 1 , L in , capacitor C 1 , C in , switch S 1 and diode D 1 ;

[0059] DC input source u in Positive connection inductor L in One end, inductor L in The other end is connected to the switch S 1 Drain, capacitor C in One end, capacitor C in The other end is connected to diode D 1 Anode, inductor L 1 One end, inductor L 1 The other end is connected to capacitor C 1 One end, capacitor C 1 The other end is connected to diode D 1 Cathode, switch S 1 Source and DC input source u in cathode;

[0060] 3 output expansion units:

[0061] The first output expansion unit includes an inductor L 2 , capacitor C 2 、Diode D 2 ; Among them, the inductor L 2 One end is connected to diode D 2 Anode, inductance L 2 The other end is connected to capacitor C 2 One end, capacitor C 2 The other end is connected to diode D 2 cathode;

[0062] The second output expansion unit includes an inductor L 3 , capacitor C 3 、Diode D 3; Among them, the inductor L 3 One end is connected to diode D 3 Anode, inductance L 3 The other end is connected to capacitor C 3 One end, capacitor C 3 The other end is connected to diode D 3 cathode;

[0063] The third output expansion unit includes an inductor L 4 , capacitor C 4 、Diode D 4 ; Among them, the inductor L 4 One end is connected to diode D 4 Anode, inductance L 4 The other end is connected to capacitor C 4 One end, capacitor C 4 The other end is connected to diode D 4 cathode.

[0064] Among the 3 jumper capacitors:

[0065] Capacitor C VB1 The upper end and the diode D 1 Anode connection, capacitor C VB1 The lower end and diode D 2 Anode connection;

[0066] Capacitor C VB2 The upper end and the diode D 2 Anode connection, capacitor C VB2 The lower end and diode D 3 Anode connection;

[0067] Capacitor C VB3 The upper end and the diode D 3 Anode connection, capacitor C VB3 The lower end and diode D 4 Anode connection.

[0068] Lithium-ion battery B 1 The positive pole is connected to the capacitor C 1 The other end, diode D 1 Cathode, Li-ion Battery B 1 The negative pole is connected to the inductor L 1 The other end, capacitor C 1 one end;

[0069] Lithium-ion battery B 2 The positive pole is connected to the capacitor C 2 The other end, diode D 2 Cathode, Li-ion Battery B 2 The negative pole is connected to the inductor L 2 The other end, capacitor C 2one end;

[0070] Lithium-ion battery B 3 The positive pole is connected to the capacitor C 3 The other end, diode D 3 Cathode, Li-ion Battery B 3 The negative pole is connected to the inductor L 3 The other end, capacitor C 3 one end;

[0071] Lithium-ion battery B 4 The positive pole is connected to the capacitor C 4 The other end, diode D 4 Cathode, Li-ion Battery B 4 The negative pole is connected to the inductor L 4 The other end, capacitor C 4 One end.

[0072] Of the 4 lithium-ion batteries:

[0073] Lithium-ion battery B 1 Positive electrode connected to lithium-ion battery B 2 Negative electrode, lithium-ion battery B 2 Positive electrode connected to lithium-ion battery B 3 Negative electrode, lithium-ion battery B 3 Positive electrode connected to lithium-ion battery B 4 negative electrode.

[0074] When the switch S 1 When conducting, diode D 1 , D 2 , D 3 , D 4 Withstand reverse voltage cutoff, capacitor C in Through loop C in →L 2 →C VB1 →C in To capacitor C VB1 Charging, similarly, capacitor C in To capacitor C VB2 , C VB3 Charging, capacitor C 1 , C 2 , C 3 , C 4 Provides energy to lithium-ion battery packs;

[0075] When the switch S 1 When off, the diode D 1 , D 2 , D 3 , D 4 On, input source u in Through inductor L inTo capacitor C in Charging, capacitor C VB1 , C VB2 , C VB3 Discharge, capacitor C 1 , C 2 , C 3 , C 4 Charging, inductance L 1 , L 2 , L 3 , L 4 Through diode D 1 , D 2 , D 3 , D 4 Provides energy to the lithium-ion battery pack.

[0076] The principle of battery balancing is to keep the battery cells in a series-connected lithium-ion battery pack in a balanced state. Currently, the balance of the entire lithium-ion battery pack is mainly determined by whether the terminal voltages of the lithium-ion battery cells are balanced (same).

[0077] Assume that the single cell B in the lithium-ion battery pack is connected in series 1 If the SOC is higher than the average value, the initial voltage u B1 >u B2 When switch S 1 When turned off, due to the cross-capacitor C VB1 The role of the diode D in the circuit 1 It is not turned on, and the current is first given to the capacitor C VB1 Discharge until the capacitor C VB1 The voltage u CVB1 rises to the output voltage u of the circuit B1 When the diode D 1 Start conducting.

[0078] Assuming the output capacitor C 1 If the output voltage ripple is large enough, it is much smaller than the cross-capacitor C VB1 The voltage ripple can be considered as u B1 The average voltage across the capacitor C VB1 In switch S 1 The peak voltage during the turn-off phase. Therefore, u B1 and u B2 The voltage deviation Δu is equal to the difference between the peak voltage and the average value, that is, the cross-capacitor C VB1 The voltage ripple peak-to-peak value is half. VB1 As the capacitance increases, the capacitor C VB1 The voltage ripple will become smaller and smaller, so the output voltage deviation will increase with C VB1 As the capacitance increases, u decreases. B1 and uB2 The voltage of capacitor C will be closer. VB1 , C VB2 , C VB3 When the voltage is large enough, the voltages of the lithium-ion battery cells are equal, thus achieving voltage balance among the lithium-ion battery cells in the lithium-ion battery pack.

[0079] Depend on Figure 3 It can be seen that the SOCs of the four lithium-ion batteries in the series lithium-ion battery pack are different, and the other parameters are the same, among which the SOCs of lithium-ion battery B1 are 88, the SOCs of lithium-ion battery B2 are 84, the SOCs of lithium-ion battery B3 are 80, and the SOCs of lithium-ion battery B4 are 76. The circuit proposed in the present invention can achieve SOC balancing of the four lithium-ion battery units.

Claims

1. A lithium battery pack charging equalization circuit, characterized in that: The circuit includes a Cuk converter, n-1 cross-capacitors, n-1 output expansion units, and n lithium-ion batteries; The Cuk converter includes an inductor L1, L in , capacitors C1, C in , switch S1 and diode D1; DC input source u in Positive connection inductor L in One end, inductor L in The other end is connected to the drain of switch S1 and capacitor C in One end, capacitor C in The other end is connected to the anode of diode D1 and one end of inductor L1. The other end of inductor L1 is connected to one end of capacitor C1. The other end of capacitor C1 is connected to the cathode of diode D1, the source of switch S1 and the DC input source u. in cathode; In n-1 output expansion units: The first output expansion unit includes an inductor L2, a capacitor C2, and a diode D2; wherein one end of the inductor L2 is connected to the anode of the diode D2, the other end of the inductor L2 is connected to one end of the capacitor C2, and the other end of the capacitor C2 is connected to the cathode of the diode D2; The second output expansion unit includes an inductor L3, a capacitor C3, and a diode D3; wherein one end of the inductor L3 is connected to the anode of the diode D3, the other end of the inductor L3 is connected to one end of the capacitor C3, and the other end of the capacitor C3 is connected to the cathode of the diode D3; The third output expansion unit includes an inductor L4, a capacitor C4, and a diode D4; wherein one end of the inductor L4 is connected to the anode of the diode D4, the other end of the inductor L4 is connected to one end of the capacitor C4, and the other end of the capacitor C4 is connected to the cathode of the diode D4; ... and so on. The n-1th output expansion unit includes an inductor L n , capacitor C n 、Diode D n ; Among them, the inductance L n One end is connected to diode D n Anode, inductance L n The other end is connected to capacitor C n One end, capacitor C n The other end is connected to diode D n cathode; Among n-1 jumper capacitors: Capacitor C VB1 The upper end is connected to the anode of diode D1, and the capacitor C VB1 The lower end is connected to the anode of diode D2; Capacitor C VB2 The upper end is connected to the anode of diode D2, and the capacitor C VB2 The lower end is connected to the anode of diode D3; Capacitor C VB3 The upper end is connected to the anode of diode D3, and the capacitor C VB3 The lower end is connected to the anode of diode D4; ... and so on. Capacitor C VB(n-1) The upper end and the diode D n-1 Anode connection, capacitor C VB(n-1) The lower end and diode D n Anode connection; The positive electrode of the lithium-ion battery B1 is connected to the other end of the capacitor C1 and the cathode of the diode D1, and the negative electrode of the lithium-ion battery B1 is connected to the other end of the inductor L1 and one end of the capacitor C1; The positive electrode of the lithium-ion battery B2 is connected to the other end of the capacitor C2 and the cathode of the diode D2, and the negative electrode of the lithium-ion battery B2 is connected to the other end of the inductor L2 and one end of the capacitor C2; ... and so on. Lithium-ion battery B n-1 The positive electrode is connected to the capacitor C n-1 The other end, diode D n-1 Cathode, Li-ion Battery B n-1 The negative pole is connected to the inductor L n-1 The other end, capacitor C n-1 one end; Lithium-ion battery B n The positive electrode is connected to the capacitor C n The other end, diode D n Cathode, Li-ion Battery B n The negative pole is connected to the inductor L n The other end, capacitor C n one end; Among n lithium-ion batteries: The positive electrode of lithium-ion battery B1 is connected to the negative electrode of lithium-ion battery B2, the positive electrode of lithium-ion battery B2 is connected to the negative electrode of lithium-ion battery B3, the positive electrode of lithium-ion battery B3 is connected to the negative electrode of lithium-ion battery B4, and so on. n-1 Positive electrode connected to lithium-ion battery B n negative electrode.

2. A lithium battery pack charging equalization circuit according to claim 1, characterized in that: The gate of the switch S1 is connected to a controller, and its duty cycle can be changed between 0 and 1.

3. A charging equalization circuit for a lithium battery pack containing 4 battery cells, characterized in that: The circuit includes a Cuk converter, three jumper capacitors, three output expansion units, and four lithium-ion batteries; The Cuk converter includes an inductor L1, L in , capacitors C1, C in , switch S1 and diode D1; DC input source u in Positive connection inductor L in One end, inductor L in The other end is connected to the drain of switch S1 and capacitor C in One end, capacitor C in The other end is connected to the anode of diode D1 and one end of inductor L1. The other end of inductor L1 is connected to one end of capacitor C1. The other end of capacitor C1 is connected to the cathode of diode D1, the source of switch S1 and the DC input source u. in cathode; 3 output expansion units: The first output expansion unit includes an inductor L2, a capacitor C2, and a diode D2; wherein one end of the inductor L2 is connected to the anode of the diode D2, the other end of the inductor L2 is connected to one end of the capacitor C2, and the other end of the capacitor C2 is connected to the cathode of the diode D2; The second output expansion unit includes an inductor L3, a capacitor C3, and a diode D3; wherein one end of the inductor L3 is connected to the anode of the diode D3, the other end of the inductor L3 is connected to one end of the capacitor C3, and the other end of the capacitor C3 is connected to the cathode of the diode D3; The third output expansion unit includes an inductor L4, a capacitor C4, and a diode D4; wherein one end of the inductor L4 is connected to the anode of the diode D4, the other end of the inductor L4 is connected to one end of the capacitor C4, and the other end of the capacitor C4 is connected to the cathode of the diode D4; Among the 3 jumper capacitors: Capacitor C VB1 The upper end is connected to the anode of diode D1, and the capacitor C VB1 The lower end is connected to the anode of diode D2; Capacitor C VB2 The upper end is connected to the anode of diode D2, and the capacitor C VB2 The lower end is connected to the anode of diode D3; Capacitor C VB3 The upper end is connected to the anode of diode D3, and the capacitor C VB3 The lower end is connected to the anode of diode D4; The positive electrode of the lithium-ion battery B1 is connected to the other end of the capacitor C1 and the cathode of the diode D1, and the negative electrode of the lithium-ion battery B1 is connected to the other end of the inductor L1 and one end of the capacitor C1; The positive electrode of the lithium-ion battery B2 is connected to the other end of the capacitor C2 and the cathode of the diode D2, and the negative electrode of the lithium-ion battery B2 is connected to the other end of the inductor L2 and one end of the capacitor C2; The positive electrode of the lithium-ion battery B3 is connected to the other end of the capacitor C3 and the cathode of the diode D3, and the negative electrode of the lithium-ion battery B3 is connected to the other end of the inductor L3 and one end of the capacitor C3; The positive electrode of the lithium-ion battery B4 is connected to the other end of the capacitor C4 and the cathode of the diode D4, and the negative electrode of the lithium-ion battery B4 is connected to the other end of the inductor L4 and one end of the capacitor C4; Of the 4 lithium-ion batteries: The positive electrode of lithium-ion battery B1 is connected to the negative electrode of lithium-ion battery B2, the positive electrode of lithium-ion battery B2 is connected to the negative electrode of lithium-ion battery B3, and the positive electrode of lithium-ion battery B3 is connected to the negative electrode of lithium-ion battery B4.

4. A charging equalization circuit for a lithium battery pack containing four battery cells according to claim 3, characterized in that: When the switch S1 is turned on, the diodes D1, D2, D3, and D4 are cut off due to the reverse voltage, and the capacitor C in Through loop C in →L2→C VB1 →C in To capacitor C VB1 Charging, similarly, capacitor C in To capacitor C VB2 , C VB3 Charging, capacitors C1, C2, C3, and C4 provide energy for the lithium-ion battery pack; When the switch S1 is turned off, the diodes D1, D2, D3, and D4 are turned on, and the input source u in Through inductor L in To capacitor C in Charging, capacitor C VB1 , C VB2 , C VB3 Discharging, capacitors C1, C2, C3, and C4 are charged, and inductors L1, L2, L3, and L4 provide energy to the lithium-ion battery pack through diodes D1, D2, D3, and D4 respectively.

5. A charging equalization circuit for a lithium battery pack containing four battery cells according to claim 3, characterized in that: Assume that the SOC of the single cell B1 in the series lithium-ion battery pack is higher than the average value, then the initial voltage u B1 >u B2 ; When switch S1 is turned off, due to the cross-connected capacitor C VB1 The diode D1 in the circuit is not turned on, and the current is first fed to the capacitor C VB1 Discharge until the capacitor C VB1 The voltage u CVB1 rises to the output voltage u of the circuit B1 When they are equal, diode D1 starts to conduct; Assuming the output capacitor C1 is large enough, the output voltage ripple is much smaller than the cross-capacitor C VB1 The voltage ripple can be considered as u B1 The average voltage across the capacitor C VB1 The peak voltage during the turn-off phase of switch S1; therefore, u B1 and u B2 The voltage deviation Δu is equal to the difference between the peak voltage and the average value, that is, the cross-capacitor C VB1 Half of the peak-to-peak voltage ripple; with the capacitance C VB1 As the capacitance increases, the capacitor C VB1 The voltage ripple will become smaller and smaller, so the output voltage deviation will increase with C VB1 As the capacitance increases, u decreases. B1 and u B2 The voltage of capacitor C will be closer; VB1 , C VB2 , C VB3 When the voltage is large enough, the voltages of the lithium-ion battery cells are equal, thus achieving voltage balance among the lithium-ion battery cells in the lithium-ion battery pack.

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