Current limiting circuit and battery pack

Abstract

The utility model discloses a current limiting circuit and a battery pack, and relates to the technical field of batteries, the current limiting circuit comprises a switching circuit, the input end of the switching circuit is electrically connected with the second end of an impedance circuit, the output end of the switching circuit is electrically connected with the power supply output end, and the controlled end of the switching circuit is electrically connected with the signal output end of a main control module; the first end of the capacitive circuit is electrically connected with the controlled end of the switching circuit, and the second end of the capacitive circuit is grounded; the input end of the charging circuit is electrically connected with the signal output end of the main control module, and the output end of the charging circuit is electrically connected with the first end of the capacitance circuit; the input end of the discharging circuit is electrically connected with the signal output end of the main control module, and the output end of the discharging circuit is electrically connected with the first end of the capacitance circuit; wherein the impedance of the charging circuit is smaller than that of the discharging circuit; the utility model aims to eliminate the ripple current generated by the switch tube.

Description

Technical Field

[0001] The utility model relates to the technical field of batteries, and in particular to a current limiting circuit and a battery pack. Background Art

[0002] The battery pack is mainly composed of battery cells and BMS (battery management system). Figure 4 As shown in the figure, one application of battery packs involves connecting multiple battery packs of the same specification in parallel. In this case, the outputs of the individual battery packs are short-circuited together to form a parallel battery pack network. There is typically a voltage difference between the battery packs. Due to this voltage difference, when connected in parallel, charge flows from the higher-voltage battery pack through the BMS's main circuit switch to the lower-voltage battery packs, thereby achieving pedestrian current balancing. When the voltage difference between battery packs is large, the balancing current between the packs will be high, which can damage the batteries and main circuit components. In this case, the main circuit switch must be disconnected to allow the balancing current to flow through a current limiting circuit. This controls the balancing current of the current packs within a certain range and balances the voltage difference between the battery packs through the current limiting circuit. When the voltage difference between the battery packs is below a certain level, the BMS's main circuit switch is switched back on. At this point, the voltage difference between the battery packs is small, and the balancing current is also low.

[0003] Existing current-limiting circuits typically control the on-time of a MOS transistor (MOSFET) using a PWM signal output by a power supply chip, thereby controlling the current flow. However, due to their operating principles, the maximum duty cycle of the drive signals output by various power supply chips on the market is less than 100%. Driven by a drive signal with a duty cycle less than 100%, a MOS transistor will operate in an intermittent switching mode. In this case, the current flowing through the MOS transistor intermittently switches as it switches on and off, resulting in a large ripple current. This ripple current can damage the battery and shorten its lifespan, so it is necessary to control the ripple current within a certain range. Utility Model Content

[0004] The main purpose of the utility model is to provide a current limiting circuit and a battery pack, aiming to eliminate the ripple current generated by the switch tube.

[0005] To achieve the above objectives, the present invention proposes a current limiting circuit, which is applied to a battery pack. The battery pack includes a power input terminal, a power output terminal, a battery, and a main control module. The power input terminal is electrically connected to the positive electrode of the battery. The main control module has a signal output terminal for outputting a PWM signal. The current limiting circuit includes:

[0006] an impedance circuit, wherein a first end of the impedance circuit is electrically connected to the negative electrode of the battery;

[0007] a switch circuit, wherein an input end of the switch circuit is electrically connected to the second end of the impedance circuit, an output end of the switch circuit is electrically connected to the power output end, and a controlled end of the switch circuit is electrically connected to the signal output end of the main control module;

[0008] a capacitor circuit, wherein a first end of the capacitor circuit is electrically connected to the controlled end of the switch circuit, and a second end of the capacitor circuit is grounded;

[0009] a charging circuit, wherein an input end of the charging circuit is electrically connected to a signal output end of the main control module, and an output end of the charging circuit is electrically connected to a first end of the capacitor circuit;

[0010] a discharge circuit, wherein an output end of the discharge circuit is electrically connected to a signal output end of the main control module, and an input end of the discharge circuit is electrically connected to a first end of the capacitor circuit;

[0011] Wherein, the impedance of the charging circuit is smaller than the impedance of the discharging circuit.

[0012] In one embodiment, the discharge circuit includes:

[0013] A first unidirectional conducting circuit, wherein an input end of the first unidirectional conducting circuit is electrically connected to a signal output end of a main control circuit, and an output end of the first unidirectional conducting circuit is electrically connected to a controlled end of the switch circuit.

[0014] In one embodiment, the charging circuit includes:

[0015] a second unidirectional conducting circuit, wherein an output end of the second unidirectional conducting circuit is electrically connected to a signal output end of the main control circuit, and an input end of the first unidirectional conducting circuit is electrically connected to a controlled end of the switch circuit;

[0016] The impedance of the second unidirectional conducting circuit is smaller than the impedance of the first unidirectional conducting circuit.

[0017] In one embodiment, the first unidirectional conducting circuit and the second unidirectional conducting circuit both include:

[0018] a first resistor, wherein a first end of the first resistor is electrically connected to the signal output end of the main control circuit, and a second end of the first resistor is electrically connected to the first end of the capacitor circuit and the controlled end of the switch circuit respectively;

[0019] The second unidirectional conducting circuit further includes:

[0020] a first diode, wherein an anode of the first diode is electrically connected to a signal output terminal of the main control circuit;

[0021] A second resistor, wherein a first end of the second resistor is electrically connected to the cathode of the first diode, and a second end of the second resistor is electrically connected to the first end of the capacitor circuit and the controlled end of the switch circuit respectively.

[0022] In one embodiment, the switching circuit includes:

[0023] a first switching tube, wherein an input end of the first switching tube is electrically connected to the second end of the impedance circuit;

[0024] A second diode, wherein an anode of the second diode is electrically connected to the output end of the first switch tube, and a cathode of the second diode is electrically connected to the output end of the power supply.

[0025] In one embodiment, the impedance circuit includes:

[0026] an inductor circuit, wherein a first end of the inductor circuit is electrically connected to the negative electrode of the battery, and a second end of the inductor circuit is electrically connected to the input end of the switch circuit;

[0027] A third diode, wherein a cathode of the third diode is electrically connected to the positive electrode of the battery, and an anode of the third diode is electrically connected to the second end of the inductor circuit.

[0028] In one embodiment, the capacitive circuit includes:

[0029] A first capacitor, wherein a first end of the first capacitor is electrically connected to the output end of the charging circuit and the input end of the discharging circuit respectively, and a second end of the first capacitor is grounded.

[0030] In one embodiment, the current limiting circuit further includes:

[0031] A driving chip, wherein an input end of the driving chip is electrically connected to the first end of the capacitor circuit, and an output end of the driving chip is electrically connected to the controlled end of the switch circuit.

[0032] The present utility model also proposes a battery pack, comprising a main control module, a battery and a current limiting circuit as described in any one of the above items; the signal output end of the main control module is connected to the controlled end of the current limiting circuit, the positive pole of the battery is electrically connected to the input end of the current limiting circuit, and the negative pole of the battery is electrically connected to the output end of the current limiting circuit.

[0033] The technical solution of the present invention is to provide a capacitor circuit, a charging circuit, and a discharging circuit in a path between a signal output terminal of a main control module and a controlled terminal of a switching circuit, so that the signal output terminal simultaneously outputs a PWM signal to the switching circuit while also charging the capacitor circuit through the charging circuit, and the capacitor circuit discharges through the discharging circuit. Since the impedance of the charging circuit is smaller than the impedance of the discharging circuit, the charging speed of the capacitor circuit is greater than the discharging speed. With this arrangement, when the main control module outputs a PWM signal with a duty cycle close to 100%, the PWM signal with a duty cycle close to 100% will have a very short falling edge phase. When the PWM signal enters the falling edge phase, under normal circumstances, the falling edge of the PWM signal will drop to close to 0V according to normal rules. However, due to the presence of the capacitor circuit, during the falling edge phase, the capacitor circuit is discharged while also charging at a relatively fast rate (because the charging speed is greater than the discharging speed). Therefore, the voltage drop rate of the PWM signal is slowed down and the falling edge is prolonged. As a result, before the falling edge drops to 0V, due to the periodic characteristics of the PWM signal and the very short duration of the falling edge phase, the PWM signal has already entered the rising edge phase. In this way, the current limiting circuit of the present invention can convert a PWM signal with a duty cycle close to 100% into a PWM signal with a duty cycle of 100%. When the switching circuit receives the PWM signal with a duty cycle of 100%, it will be in a normally open state. In this case, the switching circuit only has conduction loss and no switching loss, thereby basically eliminating the generation of ripple current. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0035] Figure 1 This is a schematic diagram of a module according to an embodiment of the present invention;

[0036] Figure 2 This is a schematic diagram of a module of another embodiment of the present utility model;

[0037] Figure 3 This is a schematic diagram of the circuit structure of an embodiment of the present utility model;

[0038] Figure 4 A schematic diagram of multiple battery packs of the same specifications connected in parallel.

[0039] Description of Figure Numbers:

[0040] 10. Impedance circuit; 20. Switching circuit; 30. Capacitive circuit; 40. Charging circuit; 41. Second unidirectional conducting circuit; 50. Discharging circuit; 51. First unidirectional conducting circuit; 60. Driver chip.

[0041] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0042] 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 embodiments described 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 making creative efforts shall fall within the scope of protection of the present invention.

[0043] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture. If the specific posture changes, the directional indications will also change accordingly.

[0044] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features limited to "first" and "second" may explicitly or implicitly include at least one of such features. In addition, if "and / or" or "and / or" appears in the full text, its meaning includes three parallel schemes. Taking "A and / or B" as an example, it includes scheme A, or scheme B, or a scheme in which A and B are satisfied at the same time. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0045] The battery pack is mainly composed of battery cells and BMS (battery management system). Figure 4As shown in the figure, one application of battery packs involves connecting multiple battery packs of the same specification in parallel. In this case, the outputs of the individual battery packs are short-circuited together to form a parallel battery pack network. There is typically a voltage difference between the battery packs. Due to this voltage difference, when connected in parallel, charge flows from the higher-voltage battery pack through the BMS's main circuit switch to the lower-voltage battery packs, thereby achieving pedestrian current balancing. When the voltage difference between battery packs is large, the balancing current between the packs will be high, which can damage the batteries and main circuit components. In this case, the main circuit switch must be disconnected to allow the balancing current to flow through a current limiting circuit. This controls the balancing current of the current packs within a certain range and balances the voltage difference between the battery packs through the current limiting circuit. When the voltage difference between the battery packs is below a certain level, the BMS's main circuit switch is switched back on. At this point, the voltage difference between the battery packs is small, and the balancing current is also low.

[0046] Existing current-limiting circuits typically control the on-time of a MOS transistor (MOSFET) using a PWM signal output by a power supply chip, thereby controlling the current flow. However, due to their operating principles, the maximum duty cycle of the drive signals output by various power supply chips on the market is less than 100%. Driven by a drive signal with a duty cycle less than 100%, a MOS transistor will operate in an intermittent switching mode. In this case, the current flowing through the MOS transistor intermittently switches as it switches on and off, resulting in a large ripple current. This ripple current can damage the battery and shorten its lifespan, so it is necessary to control the ripple current within a certain range.

[0047] To this end, the present invention proposes a current limiting circuit and a battery pack, aiming to eliminate the ripple current generated by the switching tube.

[0048] refer to Figure 1 In one embodiment of the present invention, a current limiting circuit is applied to a battery pack. The battery pack includes a power input terminal, a power output terminal, a battery, and a main control module. The power input terminal is electrically connected to the positive electrode of the battery. The main control module has a signal output terminal for outputting a PWM signal. The current limiting circuit includes:

[0049] an impedance circuit 10, wherein a first end of the impedance circuit 10 is electrically connected to the negative electrode of the battery;

[0050] a switch circuit 20, wherein the input end of the switch circuit 20 is electrically connected to the second end of the impedance circuit 10, the output end of the switch circuit 20 is electrically connected to the power output end, and the controlled end of the switch circuit 20 is electrically connected to the signal output end of the main control module;

[0051] a capacitor circuit 30, wherein a first end of the capacitor circuit 30 is electrically connected to the controlled end of the switch circuit 20, and a second end of the capacitor circuit 30 is grounded;

[0052] a charging circuit 40 , wherein an input end of the charging circuit 40 is electrically connected to a signal output end of the main control module, and an output end of the charging circuit 40 is electrically connected to a first end of the capacitor circuit 30 ;

[0053] a discharge circuit 50, wherein the output end of the discharge circuit 50 is electrically connected to the signal output end of the main control module, and the input end of the discharge circuit 50 is electrically connected to the first end of the capacitor circuit 30;

[0054] The impedance of the charging circuit 40 is smaller than the impedance of the discharging circuit 50 .

[0055] In this embodiment, the impedance circuit 10 includes at least one impedance component such as a resistor, a capacitor or an inductor. The impedance circuit 10 is used to limit the current and voltage output by the battery to prevent the current of the battery from flowing to the other battery when the voltage of the battery is greater than the voltage of the other battery.

[0056] In this embodiment, the switching circuit 20 can be implemented by at least one switching tube, such as a MOS tube, an IGBT tube, a thyristor, a triode, a power tube, etc., and / or by at least one switching device, such as a contactor, a circuit breaker and a relay.

[0057] In this embodiment, the capacitor circuit 30 includes at least one capacitor, for example, Figure 3 The capacitor circuit 30 includes: a first capacitor C1, a first end of the first capacitor C1 is electrically connected to the output end of the charging circuit 40 and the output end of the discharging circuit 50 respectively, and a second end of the first capacitor C1 is grounded.

[0058] Specifically, the technical solution of the present invention is to set a capacitor circuit 30, a charging circuit 40 and a discharge circuit 50 in the path between the signal output end of the main control module and the controlled end of the switch circuit 20, so that the signal output end can charge the capacitor circuit 30 through the charging circuit 40 while outputting the PWM signal to the switch circuit 20, and the capacitor circuit 30 can discharge through the discharge circuit 50. Since the impedance of the charging circuit 40 is smaller than the impedance of the discharge circuit 50, the charging speed of the capacitor circuit 30 is greater than the discharging speed. With this arrangement, when the main control module outputs a PWM signal with a duty cycle close to 100%, the duty cycle close to 1 A PWM signal with a duty cycle of 100% has a very short falling edge phase. When the PWM signal enters the falling edge phase, under normal circumstances, the falling edge of the PWM signal will drop to nearly 0V according to normal rules. However, due to the presence of capacitor circuit 30, during the falling edge phase, capacitor circuit 30 is simultaneously discharging and charging at a faster rate (because the charging rate is greater than the discharging rate). Therefore, the voltage drop rate of the PWM signal is slowed down, and the falling edge is prolonged. As a result, before the falling edge drops to 0V, due to the periodic characteristics of the PWM signal and the very short duration of the falling edge phase, the PWM signal has already entered the rising edge phase. In this way, the present invention can convert a PWM signal with a duty cycle of nearly 100% into a PWM signal with a duty cycle of 100%. When receiving the PWM signal with a duty cycle of 100%, the switch circuit 20 is in a normally open state. In this case, the switch circuit 20 only has conduction loss and no switching loss, thereby substantially eliminating the generation of ripple current.

[0059] It should be noted that the reference Figure 3 The current limiting circuit further includes a driver chip 60, which is configured to shape the falling edge portion of the PWM signal that does not reach 0V and convert it to a high level after shaping, thereby ensuring that the duty cycle of the PWM signal is 100%. The input end of the driver chip 60 is electrically connected to the first end of the capacitor circuit 30, and the output end of the driver chip 60 is electrically connected to the controlled end of the switch circuit 20.

[0060] In the prior art, two solutions are commonly used to reduce the ripple current in current-limiting circuits. The first is to increase the inductance in the current-limiting circuit. By increasing the inductance, the ripple current can be reduced, other conditions remaining unchanged. However, this solution increases device cost and product size. The second solution is to increase the MOS switching frequency in the current-limiting circuit, that is, to increase the frequency of the PWM signal. This higher switching frequency can reduce the ripple current, other conditions remaining unchanged. However, this reduces the efficiency of the MOS transistor and increases heat generation, requiring either increased heat dissipation or the selection of higher-performance MOS transistors, which also increases cost.

[0061] refer to Figure 2 In one embodiment of the present invention, the discharge circuit 50 includes:

[0062] A first unidirectional conducting circuit 51 has an input terminal electrically connected to a signal output terminal of a main control circuit, and an output terminal electrically connected to a controlled terminal of the switch circuit 20 .

[0063] The charging circuit 40 includes:

[0064] a second unidirectional conducting circuit 41, wherein the output end of the second unidirectional conducting circuit 41 is electrically connected to the signal output end of the main control module, and the input end of the second unidirectional conducting circuit 41 is electrically connected to the controlled end of the switch circuit 20;

[0065] The impedance of the second unidirectional conducting circuit 41 is smaller than the impedance of the first unidirectional conducting circuit 51 .

[0066] In this embodiment, the first unidirectional conduction circuit 51 and the second unidirectional conduction circuit 41 both include at least one resistor and a diode. Due to the unidirectional conduction characteristics of the diode, the signal output end of the main control module charges the capacitor circuit 30 through the second unidirectional conduction circuit 41, and the capacitor circuit 30 discharges through the first unidirectional conduction circuit 51.

[0067] In one embodiment, reference Figure 3 , the first unidirectional conducting circuit 51 and the second unidirectional conducting circuit 41 both include:

[0068] a first resistor R1, wherein a first end of the first resistor R1 is electrically connected to the signal output end of the main control circuit, and a second end of the first resistor R1 is electrically connected to the first end of the capacitor circuit 30 and the controlled end of the switch circuit 20 respectively;

[0069] The second unidirectional conducting circuit 41 further includes:

[0070] a first diode D1, wherein an anode of the first diode D1 is electrically connected to a signal output terminal of the main control circuit;

[0071] A second resistor R2 , wherein a first end of the second resistor R2 is electrically connected to the cathode of the first diode D1 , and a second end of the second resistor R2 is electrically connected to the first end of the capacitor circuit 30 and the controlled end of the switch circuit 20 .

[0072] In this embodiment, since the impedance of the second unidirectional conduction circuit 41 is smaller than the impedance of the first unidirectional conduction circuit 51, and the equivalent impedance of the first unidirectional conduction circuit 51 and the second unidirectional conduction circuit 41 in parallel is also smaller than the first unidirectional conduction circuit 51, the first unidirectional conduction circuit 51 can only include a resistor, so that the PWM signal output by the main control module charges the capacitor circuit 30 through the first unidirectional conduction circuit 51 and the second unidirectional conduction circuit 41, and the capacitor circuit 30 discharges through the first unidirectional conduction circuit 51, thereby reducing the cost of the current limiting circuit of the present invention. For example, referring to Figure 3 The signal output end of the main control module charges the capacitor circuit 30 through the first resistor R1, the first diode D1 and the second resistor R2. Due to the unidirectional conduction characteristic of the first diode D1, the capacitor circuit 30 can only discharge through the first resistor R1. Among them, the equivalent impedance of the second unidirectional conduction circuit 41 is R1 / / (D1+R2), and the impedance of the first unidirectional conduction circuit 51 is R1. According to the above formula, the equivalent impedance of the second unidirectional conduction circuit 41 is smaller than the impedance of the first unidirectional conduction circuit 51, so that the charging speed of the capacitor circuit 30 is greater than the discharging speed. With this arrangement, a PWM signal with a duty cycle approaching 100% will have a very short falling edge phase. When the PWM signal enters the falling edge phase, under normal circumstances, the falling edge of the PWM signal will normally drop to near 0V. However, due to the presence of the capacitor circuit 30, during the falling edge phase, the capacitor circuit 30 is simultaneously discharging and charging at a relatively fast rate (because the charging rate is greater than the discharging rate), thereby slowing the voltage drop of the PWM signal and prolonging the falling edge. As a result, before the falling edge drops to 0V, the PWM signal has already entered the rising edge phase due to the cyclic characteristics of the PWM signal and the very short falling edge phase. In this way, the current limiting circuit of the present invention can convert a PWM signal with a duty cycle approaching 100% into a PWM signal with a duty cycle of 100%. When the switch circuit 20 receives the PWM signal with a duty cycle of 100%, it will be in a normally open state. In this case, the switch circuit 20 only has conduction losses and no switching losses, thereby substantially eliminating the generation of ripple current.

[0073] In this way, the current limiting circuit of the present invention only needs to use two resistors, one capacitor and one diode to basically eliminate the ripple current. The two resistors, one capacitor and one diode are all very common materials and are inexpensive. Compared with the two solutions of the above-mentioned prior art, the present invention achieves the purpose of basically eliminating the ripple current while keeping the device cost and occupied area basically unchanged. Since the cost is effectively controlled, the market competitiveness of the battery pack using the current limiting circuit of the present invention can be improved.

[0074] refer to Figure 3 In one embodiment of the present invention, the switch circuit 20 includes:

[0075] a first switch tube Q1, wherein an input end of the first switch tube Q1 is electrically connected to a second end of the impedance circuit 10;

[0076] A second diode D2 , wherein an anode of the second diode D2 is electrically connected to the output end of the first switch tube Q1 , and a cathode of the second diode D2 is electrically connected to the power output end.

[0077] In this embodiment, the first switch tube Q1 can be implemented by a switch tube such as a MOS tube, an IGBT tube, a thyristor, a triode, a power tube, etc., and / or a switching device such as a contactor, a circuit breaker and a relay.

[0078] In this embodiment, the second diode D2 is used to prevent current backflow.

[0079] refer to Figure 3 In one embodiment of the present invention, the impedance circuit 10 includes:

[0080] an inductor circuit, wherein a first end of the inductor circuit is electrically connected to the negative electrode of the battery, and a second end of the inductor circuit is electrically connected to the input end of the switch circuit 20;

[0081] A third diode D3, wherein a cathode of the third diode D3 is electrically connected to the positive electrode of the battery, and an anode of the third diode D3 is electrically connected to the second end of the inductor circuit.

[0082] In this embodiment, the inductive circuit includes at least one inductor, for example Figure 3 The first inductor L1 in the inductor circuit is used to limit the ripple current in the current, and the third diode D3 is used to provide a discharge path for the inductor circuit when the switch circuit 20 is turned off, so that the current released by the inductor circuit charges the battery.

[0083] The present utility model also proposes a battery pack, comprising a main control module, a battery and the current limiting circuit as described above; wherein, the signal output end of the main control module is connected to the controlled end of the current limiting circuit, the positive pole of the battery is electrically connected to the input end of the current limiting circuit, and the negative pole of the battery is electrically connected to the output end of the current limiting circuit.

[0084] It is worth noting that since the battery pack of the present invention is based on the above-mentioned current limiting circuit, the embodiments of the battery pack of the present invention include all technical solutions of all embodiments of the above-mentioned current limiting circuit, and the technical effects achieved are also exactly the same, which will not be repeated here.

[0085] The above description is merely an exemplary embodiment of the present invention and does not limit the patent scope of the present invention. All equivalent structural transformations made using the contents of the present invention specification and drawings under the technical concept of the present invention, or direct / indirect application in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A current limiting circuit, applied to a battery pack, comprising a power input terminal, a power output terminal, a battery, and a main control module, wherein the power input terminal is electrically connected to the positive electrode of the battery, and the main control module has a signal output terminal for outputting a PWM signal, characterized in that: The current limiting circuit comprises: an impedance circuit, wherein a first end of the impedance circuit is electrically connected to the negative electrode of the battery; a switch circuit, wherein an input end of the switch circuit is electrically connected to the second end of the impedance circuit, an output end of the switch circuit is electrically connected to the power output end, and a controlled end of the switch circuit is electrically connected to the signal output end of the main control module; a capacitor circuit, wherein a first end of the capacitor circuit is electrically connected to the controlled end of the switch circuit, and a second end of the capacitor circuit is grounded; a charging circuit, wherein an input end of the charging circuit is electrically connected to a signal output end of the main control module, and an output end of the charging circuit is electrically connected to a first end of the capacitor circuit; a discharge circuit, wherein an output end of the discharge circuit is electrically connected to a signal output end of the main control module, and an input end of the discharge circuit is electrically connected to a first end of the capacitor circuit; Wherein, the impedance of the charging circuit is smaller than the impedance of the discharging circuit.

2. The current limiting circuit according to claim 1, wherein: The discharge circuit comprises: A first unidirectional conducting circuit, wherein an input end of the first unidirectional conducting circuit is electrically connected to a signal output end of a main control circuit, and an output end of the first unidirectional conducting circuit is electrically connected to a controlled end of the switch circuit.

3. The current limiting circuit according to claim 2, wherein: The charging circuit includes: a second unidirectional conducting circuit, wherein an output end of the second unidirectional conducting circuit is electrically connected to a signal output end of the main control circuit, and an input end of the first unidirectional conducting circuit is electrically connected to a controlled end of the switch circuit; The impedance of the second unidirectional conducting circuit is smaller than the impedance of the first unidirectional conducting circuit.

4. The current limiting circuit according to claim 3, wherein: The first unidirectional conducting circuit and the second unidirectional conducting circuit both include: a first resistor, wherein a first end of the first resistor is electrically connected to the signal output end of the main control circuit, and a second end of the first resistor is electrically connected to the first end of the capacitor circuit and the controlled end of the switch circuit respectively; The second unidirectional conducting circuit further includes: a first diode, wherein an anode of the first diode is electrically connected to a signal output terminal of the main control circuit; A second resistor, wherein a first end of the second resistor is electrically connected to the cathode of the first diode, and a second end of the second resistor is electrically connected to the first end of the capacitor circuit and the controlled end of the switch circuit respectively.

5. The current limiting circuit according to claim 1, wherein: The switching circuit comprises: a first switching tube, wherein an input end of the first switching tube is electrically connected to the second end of the impedance circuit; A second diode, wherein an anode of the second diode is electrically connected to the output end of the first switch tube, and a cathode of the second diode is electrically connected to the output end of the power supply.

6. The current limiting circuit according to claim 1, wherein: The impedance circuit comprises: an inductor circuit, wherein a first end of the inductor circuit is electrically connected to the negative electrode of the battery, and a second end of the inductor circuit is electrically connected to the input end of the switch circuit; A third diode, wherein a cathode of the third diode is electrically connected to the positive electrode of the battery, and an anode of the third diode is electrically connected to the second end of the inductor circuit.

7. The current limiting circuit according to claim 1, wherein: The capacitor circuit comprises: A first capacitor, wherein a first end of the first capacitor is electrically connected to the output end of the charging circuit and the input end of the discharging circuit respectively, and a second end of the first capacitor is grounded.

8. The current limiting circuit according to any one of claims 1 to 7, wherein: The current limiting circuit further includes: A driving chip, wherein an input end of the driving chip is electrically connected to the first end of the capacitor circuit, and an output end of the driving chip is electrically connected to the controlled end of the switch circuit.

9. A battery pack, characterized in that: It includes a main control module, a battery and a current limiting circuit as described in any one of items 1 to 8; the signal output end of the main control module is connected to the controlled end of the current limiting circuit, the positive pole of the battery is electrically connected to the input end of the current limiting circuit, and the negative pole of the battery is electrically connected to the output end of the current limiting circuit.

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