A current limiting device and a battery pack

Abstract

The utility model discloses a current -limiting device and including its battery pack for battery pack group packs, and the battery pack still includes electric core group, BMS module, current -limiting device includes low voltage power module, PWM generation module, current -limiting module, low voltage power module is connected with electric core group, and the power supply is low voltage power module, and PWM generation module is connected with low voltage power module, and the power supply is from it, is used for according to feedback signal output PWM signal, and current -limiting module includes series connection's current detection module, BUCK circuit module, and current detection module is connected with the negative pole of parallel's battery pack, is used for detecting charging current, is used as the feedback signal of PWM generation module, and BUCK circuit module is connected with corresponding battery pack, and BUCK circuit module includes first controllable switch, and it is controlled by PWM signal and is connected or is disconnected. The utility model independently reduces circulation, improves group pack efficiency and the safety of battery pack, prolongs the life of battery pack.

Description

Technical Field

[0001] This utility model belongs to the field of parallel battery pack technology, specifically, it relates to a current limiting device and a battery pack. Background Technology

[0002] To meet the requirements of economy and portability in home or outdoor energy storage applications, individual battery packs need to be small in size and capacity. Based on users' actual needs for long battery life, a parallel connection technology for multiple battery packs is proposed. When multiple battery packs are connected in parallel, due to differences in voltage, capacity, and cell consistency among individual battery packs, voltage variations inevitably occur. This causes circulating current between the parallel battery packs, and the greater the voltage difference, the greater the circulating current. This results in a large current being generated at the moment of parallel connection, posing a significant threat to battery pack safety and lifespan.

[0003] Considering the safety and lifespan of battery packs, the circulating current phenomenon between battery packs connected in parallel cannot be ignored. Typically, before assembling the cells, the cells are divided into groups with small differences in capacity, resulting in lower assembly efficiency and poorer stability and reliability.

[0004] The information disclosed in this background section is only intended to enhance the understanding of the background technology of this application, and therefore may include prior art that is not known to those skilled in the art. Summary of the Invention

[0005] This invention addresses the problems in existing technologies where parallel battery packs require prior differentiation of voltage levels and result in low efficiency, instability, and poor reliability when assembling packs with small voltage differences. It proposes a current-limiting device and battery pack that autonomously adjusts the frequency of the charging current-reducing switch based on the magnitude of the circulating current during voltage differential balancing, thereby reducing the circulating current, improving the efficiency and safety of parallel battery pack assembly, and extending the battery pack's lifespan.

[0006] To achieve the above-mentioned utility model / design objectives, the present utility model adopts the following technical solution:

[0007] A current limiting device is applied to a parallel battery pack assembly, and is configured to limit the charging current of the low-voltage battery pack. The battery pack includes a cell assembly and a BMS module, which includes a low-voltage power supply module, a second controllable switch, a PWM generation module, and a current limiting module.

[0008] The low-voltage power module is used to connect with the battery cell assembly to generate stable low-voltage electricity;

[0009] The PWM generation module is connected to the low-voltage power supply module, which provides the low-voltage power to output a PWM signal based on the feedback signal.

[0010] The current limiting module includes a current detection module and a BUCK circuit module connected in series; the current detection module is used to detect the charging current; the current detection module is connected to the PWM generation module; the charging current is used as the feedback signal of the PWM generation module; one end of the BUCK circuit module away from the current detection module is used to connect to the corresponding battery pack; the other end of the current detection module away from the PWM generation module is used to connect to the negative terminal of the parallel-connected battery pack; the BUCK circuit module includes a first controllable switch, which is controlled to be connected or disconnected by the PWM signal.

[0011] In some specific embodiments, a second controllable switch is also included, which is used to connect to the battery cell assembly, the BMS module, and the low-voltage power supply module; when the second controllable switch is connected or disconnected, the low-voltage power supply module is connected or disconnected from the battery cell assembly, supplying power to or stopping the supply of power to the low-voltage power supply module.

[0012] In some specific embodiments, the second controllable switch includes a first optocoupler and a first transistor;

[0013] The two ends of the light-emitting diode of the first optocoupler are respectively used to connect to the BMS module and ground;

[0014] The first transistor is a PNP type, with its collector connected to the positive terminal of the battery cell assembly, its base connected to the transistor terminal of the first optocoupler, and its emitter connected to the low-voltage power supply module.

[0015] In some specific embodiments, the current limiting module further includes a third controllable switch, which is a P-channel MOS transistor. Its source is connected to the charging interface of the corresponding battery pack, its drain is connected to the BUCK circuit module, and its gate is connected to the transistor terminal of the first optocoupler.

[0016] In some specific embodiments, the BUCK circuit module further includes a voltage regulator module, an energy storage inductor, and a first freewheeling diode and a second freewheeling diode connected in parallel with the energy storage inductor;

[0017] The negative terminals of the first freewheeling diode and the second freewheeling diode are connected to the drain of the third controllable switch, and the positive terminals are connected to one end of the first controllable switch.

[0018] The voltage regulator module consists of at least one ripple capacitor connected in parallel; the voltage regulator module is connected in parallel with the first freewheeling diode, the second freewheeling diode, and the first controllable switch.

[0019] In some specific embodiments, the BUCK circuit module further includes an energy storage capacitor module, which includes at least one energy storage capacitor connected in parallel; the energy storage capacitor module is connected in series with the energy storage inductor.

[0020] The energy storage capacitor module also includes a third diode, a fourth diode, a fifth diode, and a first resistor, which are connected in series.

[0021] The fourth and fifth diodes are Zener diodes, with their negative terminals connected to the negative terminal of the third diode and their positive terminals connected to one end of the energy storage inductor and the negative terminal of the energy storage capacitor; the positive terminal of the third diode is connected to the first resistor; and the other end of the first resistor is connected to the positive terminal of the energy storage capacitor.

[0022] In some specific embodiments, the PWM generation module uses the pulse width modulation function of the TL494 switching power supply chip;

[0023] One of the error amplifiers has its positive input terminal connected to the current detection module and its negative input terminal connected to the reference voltage circuit module; pins C1 and C2 are connected to the low-voltage power supply module; pins E1 and E2 output the PWM signal.

[0024] In some specific embodiments, a driving module is also included; the first controllable switch is an N-channel MOS transistor, and there are two of them. The gate is connected to the PWM generation module through the driving module, and the source is connected to the discharge interface of the parallel battery pack through the current detection module.

[0025] In some specific embodiments, the driving module uses a MOSFET driving chip S4427, whose INA and INB pins are connected to the PWM generation module, and whose OUTA and OUTB pins are respectively connected to the gates of the two N-channel MOSFETs of the first controllable switch.

[0026] This utility model also discloses a battery pack, which includes a cell assembly, a BMS module, and the aforementioned current limiting device; the current limiting device is connected to the BMS module, and when multiple battery packs are connected in parallel, it is connected to the discharge interface of the parallel battery pack.

[0027] Compared with the prior art, the advantages and positive effects of this utility model are:

[0028] This utility model discloses a current limiting device and a battery pack including the current limiting device. When battery packs are connected in parallel, a current limiting device is configured for each cell group. The switching frequency of the current limiting module of the current limiting device corresponding to the low-voltage cell group is controlled according to the circulating current. This regulates and limits the current of the low-voltage cell group when it is charged by the circulating current, solving the problem of large current circulating current formed between battery packs in parallel packs causing great impact on the cell group and BMS module. This protects the power devices of the cell group and BMS module, improves packing efficiency and battery pack safety, and extends the battery pack life.

[0029] Other features and advantages of this utility model will become clearer after reading the specific embodiments of this utility model in conjunction with the accompanying drawings. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of this utility model, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a schematic diagram of the parallel battery pack connection structure according to an embodiment;

[0032] Figure 2 This is a schematic diagram of the composition and connection structure of the current limiting device according to the embodiment;

[0033] Figure 3 This is a schematic diagram of the connection and circuit of a low-voltage power supply module according to an embodiment;

[0034] Figure 4 This is a schematic diagram of the connection and circuit of the PWM generation module according to an embodiment;

[0035] Figure 5 This is a connection and circuit diagram of the current limiting module according to an embodiment.

[0036] In the picture,

[0037] 01. Battery Pack; 1. Cell Pack; 2. BMS Module; 3. Current Limiting Device; 31. Low-Voltage Power Supply Module; 32. Second Controllable Switch; 33. PWM Generation Module; 34. Current Limiting Module;

[0038] Q1, First transistor; U4, First optocoupler; U1, Buck power supply chip; U2, Switching power supply chip; P1, Third controllable switch; L1, Energy storage inductor; D1, First freewheeling diode; D2, Second freewheeling diode; D3, Third diode; D4, Fourth diode; D5, Fifth diode; R1, First resistor; E11, First capacitor; E12, Second capacitor; E13, Third capacitor; E14, Fourth capacitor; R2, Second resistor; N1, First N-channel MOSFET; N2, Second N-channel MOSFET; U3, Driver module; R3, Third resistor; R4, Fourth resistor. Detailed Implementation

[0039] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0040] In the description of this utility model, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0041] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances. In the description of the embodiments, specific features, structures, materials, or characteristics can be combined in any suitable manner in one or more embodiments or examples.

[0042] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature.

[0043] In the description of this utility model, unless otherwise stated, "a plurality of" means two or more.

[0044] Reference Figure 1 , Figure 2 This utility model discloses a current limiting device applied to parallel battery packs 01. It is configured to limit the charging current of the low-voltage battery pack 01. That is, each battery pack 01 is equipped with a current limiting device 3, which is connected to the corresponding battery pack 01 and the parallel battery packs 01 when the battery packs 01 are connected in parallel. It is used to adjust and / or limit the charging current of the low-voltage battery pack 01 when circulating current is generated due to voltage differences among the battery packs 01 in the pack.

[0045] The battery pack 01 includes a cell group 1 and a BMS module 2; the current limiting device 3 includes a low-voltage power supply module 31, a PWM generation module 33, and a current limiting module 34.

[0046] The low-voltage power module 31 is used to generate stable low-voltage electricity. It is used to connect to the positive terminal of the battery cell group 1 of the corresponding battery pack 01. The battery cell group 1 supplies power to the low-voltage power module 31, thereby enabling the low-voltage power module to generate stable low-voltage electricity.

[0047] The PWM generation module 33 is connected to the low-voltage power supply module 31, which provides voltage to the PWM signal for non-programmable output based on the feedback signal.

[0048] The current limiting module 34 includes a current detection module and a BUCK circuit module connected in series. The current detection module is used to detect the charging current. The current detection module is connected to the PWM generation module 33 and transmits the detected charging current to the PWM generation module 33 as a feedback signal. The end of the BUCK circuit module away from the current detection module is connected to the charging interface P-2 of the corresponding battery pack 01, and the end of the current detection module away from the PWM generation module 33, i.e., away from the BUCK circuit module, is connected to the discharging interface P-1 of the parallel battery pack 01. The charging interface P-2 and the discharging interface P-1 are respectively connected to the negative terminal of the cell group 1 through MOSFETs.

[0049] The BUCK circuit module includes a first controllable switch, which is controlled to be connected or disconnected by a PWM signal to realize the switching control of the charging circuit of the low-voltage battery pack 01, thereby controlling the charging current of the corresponding low-voltage battery pack 01.

[0050] This utility model also discloses a battery pack, which includes a cell group 1, a BMS module 2, and a current limiting device 3; the cell group 1 is connected to the BMS module 2 and the current limiting device 3 respectively; the current limiting device 3 is connected to the BMS module 2, and when each battery pack 01 is connected in parallel, it is connected to the BMS module 2 of the parallel battery pack 01.

[0051] Specifically, the current limiting device 3 is connected to the positive terminal of the cell pack 1, the charging interface of the BMS module 2, and the control interface, respectively; when the packs are connected in parallel, the discharge interface of the BMS of the battery pack 01 is connected in parallel with the current limiting device 3; the positive terminal of the battery pack is connected.

[0052] In this invention, when battery packs 01 are connected in parallel, a current limiting device 3 is configured for each cell group 1. The current limiting device 3 controls the switching frequency of the current limiting module 34 of the current limiting device 3 corresponding to the low-voltage cell group 1 by outputting a PWM signal without programming based on the circulating current. This regulates and limits the current of the low-voltage cell group 1 during circulating current charging, solving the problem of the large current circulating current formed between battery packs 01 in parallel charging having a large impact on cell group 1 and BMS module 2. This protects the power devices of cell group 1 and BMS module 2, improves packing efficiency and battery pack safety, and extends battery pack life.

[0053] The specific circuit structure and principle of the current limiting device and battery pack of this utility model will be described in detail below through specific embodiments.

[0054] In some specific embodiments, refer to Figure 1 , Figure 2 The current limiting device 3 also includes a second controllable switch 32; the low-voltage power module 31 is connected to the positive terminal of the cell group 1 of the corresponding battery pack 01 through the second controllable switch 32; when the second controllable switch 32 is connected, the low-voltage power module 31 is connected to the positive terminal of the cell group 1, and the cell group 1 supplies power to the low-voltage power module 31, thereby generating a stable low-voltage power supply.

[0055] The control terminal of the second controllable switch 32 is connected to the BMS module 2 and is controlled by a control signal generated by the BMS based on the charging current. This signal can be a hardware-implemented high-level or low-level signal that remains above a threshold. When the circulating current exceeds the threshold, the second controllable switch 32 of the current limiting device 3 corresponding to the battery pack 01 being charged is connected, the low-voltage power supply module 31 outputs low-voltage electricity, and the current limiting module 34 is powered and operates. When the battery pack 01 being discharged, the second controllable switch 32 of the current limiting device 3 corresponding to the discharging battery pack 01 is disconnected, and the current limiting module 34 of the corresponding current limiting device 3 is de-energized and stops operating, reducing energy consumption and saving energy.

[0056] The embodiment of the battery pack includes the current limiting device 3 described above, which is connected to the positive terminal of the cell group 1 of the same battery pack 01 in the manner described above, thereby reducing energy consumption and saving energy.

[0057] In some specific embodiments, refer to Figure 2 , Figure 5The current detection module of the current limiting device 3 includes a third resistor R3 and a fourth resistor R4, both of which are precision detection resistors connected in parallel. Their two ends are respectively connected to the discharge interface P-1 of the BUCK circuit module and the parallel battery pack, and are used to detect the charging current.

[0058] The battery pack embodiment includes the current limiting device 3 described above.

[0059] In some specific embodiments, refer to Figure 2 , Figure 3 The second controllable switch 32 includes a first optocoupler U4 and a first transistor Q1.

[0060] The two ends of the light-emitting diode of the first optocoupler U4 are used to connect to the BMS module 2 and ground, respectively; it receives the output signal of the BMS module 2 and controls the first optocoupler U4.

[0061] The first transistor Q1 is a PNP type. Its collector is used to connect to the positive terminal of the battery cell assembly 1, its base is connected to one end of the transistor of the first optocoupler U4, and its emitter is connected to the low-voltage power supply module 31. The other end of the transistor of the first optocoupler U4 is grounded.

[0062] When the light-emitting diode terminal of the first optocoupler U4 is connected to a high level, its transistor is connected; that is, the base of the first transistor Q1 is grounded; the collector is connected to a high level, and the collector and emitter of the first transistor Q1 are connected; the low-voltage power supply module 31 is connected to the positive terminal of the battery cell group 1, the low-voltage power supply module 31 is powered on, and outputs low-voltage electricity.

[0063] The battery pack embodiment includes the current limiting device 3 described above.

[0064] In this embodiment, the current limiting device and battery pack control whether the low-voltage power module 31 is connected to the positive terminal of the power supply cell group 1 via a second controllable switch 32 composed of the first optocoupler U4 and the first transistor Q1. That is, it controls whether the low-voltage power module 31 outputs low-voltage electricity to determine whether the current limiting device 3 has operating power. Thus, the second controllable switch 32 controls whether the current limiting device 3 operates. Furthermore, the first optocoupler U4 isolates the control terminal from the power supply terminal, increasing the safety, stability, and reliability of the BMS module 2.

[0065] In some specific embodiments, refer to Figure 1 , Figure 2 , Figure 3 The step-down power chip U1 of the low-voltage power module 31 is the MIP4581, which is a high-efficiency synchronous step-down converter with constant on-time (COT) control mode, which can provide fast transient response and make the output loop more stable.

[0066] The battery pack embodiment includes the current limiting device 3 described above.

[0067] In some specific embodiments, refer to Figure 1 , Figure 2 , Figure 5 The current limiting module 34 also includes a third controllable switch P1P1, which is a P-channel MOS transistor. The source S of the third controllable switch P1 is used to connect to the charging interface of the corresponding battery pack 01, the drain D is connected to the BUCK circuit module, and the gate G is connected to the non-grounded terminal of the transistor of the first optocoupler U4.

[0068] When the two ends of the transistor of the first optocoupler U4 are connected, the gate of the third controllable switch P1 is grounded, the source voltage is higher than the gate voltage, and its source and drain are connected; the power supply of the BUCK circuit module is controlled by the control signal that controls whether the low-voltage power supply module 31 is running, so that the power supply of the current limiting device 3 and the charging circuit are connected at the same time, thereby improving control efficiency and safety.

[0069] The battery pack embodiment includes the current limiting device 3 described above.

[0070] In some specific embodiments, refer to Figure 1 , Figure 2 , Figure 5 The BUCK circuit module also includes a voltage regulator module, an energy storage inductor L1L1, and a first freewheeling diode D1D1 and a second freewheeling diode D2D2 connected in parallel with the energy storage inductor L1L1.

[0071] The negative terminals of the first freewheeling diode D1 and the second freewheeling diode D2 are connected to the drain of the third controllable switch P1, and the positive terminals are connected to one end of the first controllable switch.

[0072] The voltage regulator module includes at least one ripple capacitor connected in parallel. The voltage regulator module is also connected in parallel with the first freewheeling diode D1, the second freewheeling diode D2, and the first controllable switch, serving as the output capacitor of the buck circuit module. Specifically, the ripple capacitors are connected in parallel, with their positive terminals connected to the negative terminals of the first and second freewheeling diodes D1 and D2, and their negative terminals connected to the other end of the first controllable switch. This process converts the pulsating DC voltage into a smooth DC voltage, reducing battery charging voltage and current ripple.

[0073] The battery pack embodiment includes the current limiting device 3 described above.

[0074] In some specific embodiments, refer to Figure 1 , Figure 2 , Figure 5 The voltage regulator module consists of multiple ripple capacitors connected in parallel, which reduces the height and size of the voltage regulator module.

[0075] The battery pack embodiment includes the current limiting device 3 described above.

[0076] In some specific embodiments, refer to Figure 1 , Figure 2 , Figure 5 The voltage regulator module includes two ripple capacitors, namely the first capacitor E11 and the second capacitor E12.

[0077] The battery pack embodiment includes the current limiting device 3 described above.

[0078] In some specific embodiments, refer to Figure 1 , Figure 2 , Figure 5 The BUCK circuit module also includes an energy storage capacitor module, which includes at least one energy storage capacitor connected in series with an energy storage inductor L1.

[0079] The energy storage capacitor module also includes a third diode D3, a fourth diode D4, a fifth diode D5, and a first resistor R1, which are connected in series, and the two ends of the series circuit are respectively connected to the two ends of the energy storage capacitor module.

[0080] That is, the fourth diode D4 and the fifth diode D5 are Zener diodes, with their negative terminals connected to the negative terminal of the third diode D3 and their positive terminals connected to one end of the energy storage inductor L1 and the negative terminal of the energy storage capacitor; the positive terminal of the third diode D3 is connected to the first resistor R1; and the other end of the first resistor R1 is connected to the positive terminal of the energy storage capacitor.

[0081] The battery pack embodiment includes the current limiting device 3 described above.

[0082] In this embodiment, the current limiting device and battery pack limit the energy storage voltage of the energy storage capacitor module through the fourth diode D4 and the fifth diode D5; the energy storage capacitor module provides energy storage current to the energy storage inductor L1, reduces the instantaneous discharge current of the discharge battery pack 01, protects the discharge battery pack 01, and maintains the voltage stability of the buck circuit module, thereby improving the stability of the buck circuit module.

[0083] In some specific embodiments, refer to Figure 1 , Figure 2 , Figure 5 The energy storage capacitor module includes two energy storage capacitors, namely the third capacitor E13 and the fourth capacitor E14.

[0084] The battery pack embodiment includes the current limiting device 3 described above.

[0085] In some specific embodiments, refer to Figure 1 , Figure 2 , Figure 5 The voltage regulator module also includes a second resistor R2, which is connected in parallel with each ripple capacitor and is used to discharge each ripple capacitor when the connection between the current limiting device 3 and the battery pack 01 is disconnected.

[0086] The battery pack embodiment includes the current limiting device 3 described above.

[0087] In some specific embodiments, refer to Figure 1 , Figure 2 , Figure 4 The PWM generation module 33 uses the pulse width modulation function of the switching power supply chip U2, model number TL494.

[0088] One of the error amplifiers has its positive input connected to the current detection module and its negative input connected to the reference voltage circuit module; pins C1 and C2 are connected to the low voltage circuit; pins E1 and E2 output the PWM signal CON PWM.

[0089] The battery pack embodiment includes the current limiting device 3 described above.

[0090] The current limiting device and battery pack in this embodiment use a TL494 switching power supply chip U2. This chip has two operational amplifiers inside. These two operational amplifiers are used as feedback input terminals, and their output signals are converted into PWM signals modulated inside the chip, thereby realizing the periodic opening and closing of the MOS. Combined with energy storage components such as inductors and capacitors, energy is transferred from high to low. Furthermore, the required current value can be adjusted by adjusting the sampling resistor value of the current detection module or the reference voltage value of the current feedback input terminal. The entire process does not require software algorithm control; it automatically identifies and outputs, thereby greatly reducing the burden on the controller of the BMS control module.

[0091] In some specific embodiments, refer to Figure 1 , Figure 2 , Figure 5 It also includes a drive module U3; the first controllable switch is an N-channel MOSFET, there are two of them, namely the first N-channel MOSFET N1 and the second N-channel MOSFET N2. The gate of the switch is connected to the PWM generation module 33 through the drive module U3, the source is connected to the discharge interface of the parallel battery pack 01 through the current detection module, and the drain is connected to the positive terminal of the first freewheeling diode D1 and the second freewheeling diode D2.

[0092] The battery pack embodiment includes the current limiting device 3 described above.

[0093] In some specific embodiments, refer to Figure 1 , Figure 2 , Figure 5 The drive module U3 uses the MOSFET drive chip S4427. Its INA and INB pins are connected to the PWM generation module 33, and its OUTA and OUTB pins are connected to the gates of the two N-channel MOSFETs of the first controllable switch, respectively.

[0094] The battery pack embodiment includes the current limiting device 3 described above.

[0095] The above embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Although this utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions claimed by this utility model.

Claims

1. A current limiting device, applied to a parallel battery pack assembly, configured for each battery pack to limit the charging current of the low-voltage battery pack; the battery pack... Including battery cell assembly and BMS module, characterized in that it includes: A low-voltage power supply module is used to connect to the battery cell assembly to generate stable low-voltage electricity; A PWM generation module is connected to the low-voltage power supply module, which provides the low-voltage power to the module and is used to output a PWM signal based on a feedback signal. A current limiting module includes a current detection module and a BUCK circuit module connected in series. The current detection module is used to detect the charging current. The current detection module is connected to the PWM generation module. The charging current is used as the feedback signal of the PWM generation module. One end of the BUCK circuit module away from the current detection module is used to connect to the corresponding battery pack. The other end of the current detection module away from the PWM generation module is used to connect to the negative terminal of the parallel-connected battery pack. The BUCK circuit module includes a first controllable switch, which is controlled to be connected or disconnected by the PWM signal.

2. The current limiting device according to claim 1, characterized in that, It also includes a second controllable switch, which is used to connect to the battery cell assembly, the BMS module, and the low-voltage power supply module; when the second controllable switch is connected or disconnected, the low-voltage power supply module is connected or disconnected from the battery cell assembly, supplying power to or stopping the supply of power to the low-voltage power supply module.

3. The current limiting device according to claim 2, characterized in that, The second controllable switch includes a first optocoupler and a first transistor; The two ends of the light-emitting diode of the first optocoupler are respectively used to connect to the BMS module and ground; The first transistor is a PNP type, with its collector connected to the positive terminal of the battery cell assembly, its base connected to the transistor terminal of the first optocoupler, and its emitter connected to the low-voltage power supply module.

4. The current limiting device according to claim 3, characterized in that, The current limiting module also includes a third controllable switch, which is a P-channel MOS transistor. Its source is connected to the charging interface of the corresponding battery pack, its drain is connected to the BUCK circuit module, and its gate is connected to the transistor terminal of the first optocoupler.

5. The current limiting device according to claim 4, characterized in that, The BUCK circuit module also includes a voltage regulator module, an energy storage inductor, and a first freewheeling diode and a second freewheeling diode connected in parallel with the energy storage inductor. The negative terminals of the first freewheeling diode and the second freewheeling diode are connected to the drain of the third controllable switch, and the positive terminals are connected to one end of the first controllable switch. The voltage regulator module consists of at least one ripple capacitor connected in parallel; the voltage regulator module is connected in parallel with the first freewheeling diode, the second freewheeling diode, and the first controllable switch.

6. The current limiting device according to claim 5, characterized in that, The BUCK circuit module also includes an energy storage capacitor module, which includes at least one energy storage capacitor connected in parallel; the energy storage capacitor module is connected in series with the energy storage inductor. The energy storage capacitor module also includes a third diode, a fourth diode, a fifth diode, and a first resistor, which are connected in series. The fourth and fifth diodes are Zener diodes, with their negative terminals connected to the negative terminal of the third diode and their positive terminals connected to one end of the energy storage inductor and the negative terminal of the energy storage capacitor; the positive terminal of the third diode is connected to the first resistor; and the other end of the first resistor is connected to the positive terminal of the energy storage capacitor.

7. The current limiting device according to any one of claims 1 to 6, characterized in that, The PWM generation module uses the pulse width modulation function of the TL494 switching power supply chip; The positive input terminal of one of the error amplifiers is connected to the current detection module, and the negative input terminal is connected to the reference voltage circuit module; pins C1 and C2 are connected to the low-voltage power supply module. The PWM signal is output from pins E1 and E2.

8. The current limiting device according to claim 7, characterized in that, It also includes a drive module; the first controllable switch is an N-channel MOSFET, and there are two of them. The gate is connected to the PWM generation module through the drive module, and the source is connected to the discharge interface of the parallel battery pack through the current detection module.

9. The current limiting device according to claim 8, characterized in that, The driving module uses a MOSFET driver chip S4427, whose INA and INB pins are connected to the PWM generation module, and whose OUTA and OUTB pins are connected to the gates of the two N-channel MOSFETs of the first controllable switch, respectively.

10. A battery pack, characterized in that, It includes a battery cell assembly, a BMS module, and a current limiting device as described in any one of claims 1 to 9; the current limiting device is connected to the BMS module and, when multiple battery packs are connected in parallel, is connected to the discharge interface of the parallel battery pack.

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