Battery pack charging system

Abstract

The utility model provides a battery pack charging system, and belongs to the technical field of battery pack charging. The battery pack charging system comprises a reference voltage module, a comparison module, a charging mode switching module, a charging control module and a voltage detection module, the reference end of the comparison module is connected with the reference voltage module, the output end of the comparison module is connected with the input end of the charging mode switching module, the output end of the charging mode switching module is connected with the control end of the charging control module, and the output end of the charging control module is connected with the battery pack; the input end of the voltage detection module is connected with the feedback end of the charging control module. The output end of the voltage detection module is connected with the input end of the comparison module. And the charging mode switching module is configured to switch the charging mode of the battery pack according to the electric signal output by the comparison module. The charging efficiency of the battery pack can be improved.

Description

Technical Field

[0001] This disclosure relates to the field of battery pack charging technology, and more particularly to a battery pack charging system. Background Technology

[0002] With the rapid development of electric vehicles and heavy-duty truck battery swapping systems, the charging efficiency and safety of battery packs have become key factors restricting their widespread application. Traditional charging methods often employ a single charging mode, which cannot be flexibly adjusted according to the actual state of the battery pack. This may not only cause damage to the battery due to high current surges when the battery is low in charge, shortening its lifespan, but may also reduce charging efficiency due to improper charging strategies. Utility Model Content

[0003] This disclosure provides a battery pack charging system to improve the charging efficiency of the battery pack.

[0004] This disclosure provides a battery pack charging system, including: a reference voltage module, a comparison module, a charging mode switching module, a charging control module, and a voltage detection module;

[0005] The reference terminal of the comparison module is connected to the reference voltage module, the output terminal of the comparison module is connected to the input terminal of the charging mode switching module, the output terminal of the charging mode switching module is connected to the control terminal of the charging control module, and the output terminal of the charging control module is connected to the battery pack.

[0006] The input terminal of the voltage detection module is connected to the feedback terminal of the charging control module, and the output terminal of the voltage detection module is connected to the input terminal of the comparison module.

[0007] The charging mode switching module is configured to switch the charging mode of the battery pack according to the electrical signal output by the comparison module.

[0008] In one exemplary embodiment of this disclosure, the comparison module includes: operational amplifier U1 and operational amplifier U2;

[0009] The inverting input terminals of both operational amplifier U1 and operational amplifier U2 are connected to the output terminal of the voltage detection module.

[0010] The non-inverting input terminal of the operational amplifier U1 is used to connect to the first reference voltage of the reference voltage module, and the non-inverting input terminal of the operational amplifier U2 is used to connect to the second reference voltage of the reference voltage module.

[0011] The output terminals of both operational amplifier U1 and operational amplifier U2 are connected to the input terminal of the charging mode switching module.

[0012] The second reference voltage is greater than the first reference voltage.

[0013] In one exemplary embodiment of this disclosure, the reference voltage module includes: a variable resistor RP1, a resistor R1, and a resistor R2;

[0014] The first end of the variable resistor RP1 is connected to the VCC power supply, the second end of the variable resistor RP1 is connected to the first end of the resistor R1, the second end of the resistor R1 is grounded through the resistor R2, the first end of the resistor R1 is connected to the non-inverting input terminal of the operational amplifier U2, and the second end of the resistor R1 is connected to the non-inverting input terminal of the operational amplifier U1.

[0015] In one exemplary embodiment of this disclosure, the charging mode switching module includes: a D flip-flop, a transistor Q2, a transistor Q3, a transistor Q4, a resistor R4, an operational amplifier U4, and a resistor R6;

[0016] The input terminal of the D flip-flop U3 is connected to the output terminal of the operational amplifier U1, the output terminal of the operational amplifier U2 is connected to the clock terminal of the D flip-flop U3, the first output terminal of the D flip-flop U3 is connected to the base of the transistor Q2, the collector of the transistor Q2 is connected to the VCC power supply, the emitter of the transistor Q2 is connected to the non-inverting input terminal of the operational amplifier U4, and the resistor R4 is connected in parallel between the collector and emitter of the transistor Q2.

[0017] The second output terminal of the D flip-flop U3 is connected to the base of the transistor Q3, the emitter of the transistor Q3 is used to connect to the signal generator, the collector of the transistor Q3 is connected to the inverting input terminal of the operational amplifier U4, and the output terminal of the operational amplifier U4 is connected to the control terminal of the charging control module.

[0018] The base of transistor Q4 is connected to the base of transistor Q3, the collector of transistor Q4 is connected to the feedback terminal of the charging control module, and the emitter of transistor Q4 is connected to the inverting input terminal of operational amplifier U4.

[0019] In one exemplary embodiment of this disclosure, the charging control module includes: a switching transistor Q1 and a resistor R6;

[0020] The control terminal of the switching transistor Q1 is connected to the output terminal of the charging mode switching module. The first terminal of the switching transistor Q1 is connected to the VCC power supply, and the second terminal of the switching transistor Q1 is connected to the positive terminal of the battery pack. The negative terminal of the battery pack is grounded through the resistor R6.

[0021] In one exemplary embodiment of this disclosure, the voltage detection module includes: resistor R11, resistor R9, capacitor C1, operational amplifier U5, and resistor R10;

[0022] The first end of resistor R11 is connected to the negative terminal of the battery pack, and the second end of resistor R11 is connected to the inverting input terminal of operational amplifier U5. The first end of resistor R9 is connected to the positive terminal of the battery pack, and the second end of resistor R9 is grounded through capacitor C1. The second end of resistor R9 is connected to the non-inverting input terminal of operational amplifier U5. The output terminal of operational amplifier U5 is connected to the inverting input terminal of operational amplifier U5 through resistor R10. The output terminal of operational amplifier U5 is connected to the inverting input terminals of operational amplifiers U1 and U2.

[0023] In one exemplary embodiment of this disclosure, it further includes: an overcharge protection module;

[0024] The first end of the overcharge protection module is connected to the output end of the comparison module, and the second end of the overcharge protection module is connected to the control end of the charging control module.

[0025] In one exemplary embodiment of this disclosure, the overcharge protection module includes: NOT gate U6, NOT gate U8, AND gate U9 and transistor Q5;

[0026] The input terminal of NOT gate U6 is connected to the output terminal of operational amplifier U1, the output terminal of NOT gate U6 is connected to the first input terminal of AND gate U9, the input terminal of NOT gate U8 is connected to the output terminal of operational amplifier U2, the output terminal of NOT gate U8 is connected to the second input terminal of AND gate U9, the output terminal of AND gate U9 is connected to the base of transistor Q5, the collector of transistor Q5 is connected to the control terminal of the charging control module, and the emitter of transistor Q5 is grounded.

[0027] The beneficial effects of the battery pack charging system provided in this disclosure are as follows: The reference voltage module in this disclosure provides a benchmark for comparison, making the charging mode determination more accurate. The voltage detection module provides real-time feedback of the battery pack voltage, and together with the output signal of the comparison module, the charging mode switching module can automatically switch between different charging modes according to the battery status. This avoids damage to the battery caused by high-current charging when the battery is low, extending battery life, and enables rapid charging at appropriate stages, improving charging efficiency. Furthermore, the charging system in this disclosure constitutes a closed-loop control system, ensuring the safety and stability of the entire charging process and effectively guaranteeing the reliability and efficiency of battery pack charging. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of this disclosure, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a schematic diagram of the structure of the battery pack charging system provided in the embodiments of this disclosure;

[0030] Figure 2 This is a circuit diagram of a battery pack charging system provided in an embodiment of this disclosure. Detailed Implementation

[0031] To enable those skilled in the art to better understand this solution, the technical solutions in the embodiments of this solution will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this solution, not all of them. Based on the embodiments of this solution, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this solution.

[0032] The term "comprising" and any other variations thereof in the specification, claims, and accompanying drawings of this invention mean "including but not limited to," and are intended to cover a non-exclusive inclusion, not limited to the examples listed herein. Furthermore, the terms "first" and "second," etc., are used to distinguish different objects, not to describe a specific order.

[0033] The implementation of this disclosure will be described in detail below with reference to the specific accompanying drawings:

[0034] Figure 1 This is a schematic diagram of a battery pack charging system provided in an embodiment of this disclosure. (Refer to...) Figure 1 The battery pack charging system includes: a reference voltage module, a comparison module, a charging mode switching module, a charging control module, and a voltage detection module; the reference terminal of the comparison module is connected to the reference voltage module, the output terminal of the comparison module is connected to the input terminal of the charging mode switching module, the output terminal of the charging mode switching module is connected to the control terminal of the charging control module, and the output terminal of the charging control module is connected to the battery pack; the input terminal of the voltage detection module is connected to the feedback terminal of the charging control module, and the output terminal of the voltage detection module is connected to the input terminal of the comparison module; the charging mode switching module is configured to switch the charging mode of the battery pack according to the electrical signal output by the comparison module.

[0035] In this embodiment, the reference voltage module provides a reference voltage for the comparison module. The voltage detection module acquires the voltage of the battery pack and converts the battery pack voltage signal into a suitable electrical signal, which is then sent to the input of the comparison module. The comparison module compares the voltage output by the voltage detection module with the reference voltage. The comparison module can output different electrical signals based on the battery pack voltage. For example, when the battery pack voltage is lower than a certain set value, a specific electrical signal is output to indicate that the battery is in a low-charge state; when the battery pack voltage is higher than a certain set value, another electrical signal is output to indicate that the battery has reached a certain charge level.

[0036] The charging mode switching module receives the electrical signal output by the comparison module and switches between different charging modes based on this signal. Specifically, when the battery pack voltage is too low, i.e., at the beginning of charging, the comparison module outputs a corresponding low-charge signal. The charging mode switching module then sets the charging mode to trickle charging mode, using a small current to pre-charge the battery pack and avoid damaging the low-charge battery with a large current. As charging progresses, when the battery pack voltage exceeds a certain set value, the comparison module outputs a new electrical signal. Upon receiving this signal, the charging mode switching module switches the charging mode to constant-current charging mode, thereby achieving fast charging and improving charging efficiency.

[0037] After determining the charging mode, the charging mode switching module sends a control signal to the control terminal of the charging control module. Based on the received control signal, the charging control module charges the battery pack according to the corresponding charging mode, and its output terminal is connected to the battery pack to provide charging current. Simultaneously, the voltage detection module is connected to the feedback terminal of the charging control module to collect real-time data on the voltage changes of the battery pack during charging and feeds this information back to the comparison module, forming a closed-loop control system.

[0038] As can be seen from the above, the reference voltage module in this embodiment provides a benchmark for comparison, making the charging mode determination more accurate. The voltage detection module provides real-time feedback of the battery pack voltage, which, together with the output signal of the comparison module, allows the charging mode switching module to automatically switch between different charging modes based on the battery status. This avoids damage to the battery caused by high-current charging when the battery is low, extending battery life, and enables rapid charging at appropriate stages, improving charging efficiency. Furthermore, the charging system in this embodiment constitutes a closed-loop control system, ensuring the safety and stability of the entire charging process and effectively guaranteeing the reliability and efficiency of battery pack charging.

[0039] like Figure 2 As shown, in one embodiment of this disclosure, the comparison module includes: operational amplifier U1 and operational amplifier U2; the inverting input terminals of operational amplifier U1 and operational amplifier U2 are both connected to the output terminal of the voltage detection module; the non-inverting input terminal of operational amplifier U1 is used to connect to the first reference voltage of the reference voltage module, and the non-inverting input terminal of operational amplifier U2 is used to connect to the second reference voltage of the reference voltage module; the output terminals of operational amplifier U1 and operational amplifier U2 are both connected to the input terminal of the charging mode switching module; the second reference voltage is greater than the first reference voltage.

[0040] In this embodiment, the voltage detection module monitors the battery pack voltage in real time and outputs a corresponding voltage signal. When the battery pack voltage is too low, this signal voltage is less than both the first reference voltage provided by the reference voltage module and the second reference voltage (the second reference voltage is greater than the first reference voltage). At this time, operational amplifier U1 outputs a high level because the voltage at its inverting input is less than the first reference voltage at its non-inverting input; similarly, operational amplifier U2 also outputs a high level because the voltage at its inverting input is less than the second reference voltage at its non-inverting input. Upon receiving these two high-level signals, the charging mode switching module determines that the battery pack is in a low-charge state and sets the charging mode to trickle charging mode to safely charge with a small current and avoid damaging the battery.

[0041] As the battery pack charges, the voltage rises. When the voltage detection module outputs a voltage greater than the first reference voltage but still less than the second reference voltage, the voltage at the inverting input of operational amplifier U1 is higher than the first reference voltage at the non-inverting input, resulting in a low-level output. Meanwhile, the voltage at the inverting input of operational amplifier U2 remains lower than the second reference voltage at the non-inverting input, leading to a high-level output. The charging mode switching module recognizes this voltage combination—receiving a low level from operational amplifier U1 and a high level from operational amplifier U2—and determines that the battery pack is suitable for higher-efficiency charging. Therefore, it switches the charging mode to constant-current charging mode to accelerate the charging speed.

[0042] like Figure 2 As shown, in one embodiment of this disclosure, the reference voltage module includes: a variable resistor RP1, a resistor R1, and a resistor R2; the first end of the variable resistor RP1 is connected to the VCC power supply, the second end of the variable resistor RP1 is connected to the first end of the resistor R1, the second end of the resistor R1 is grounded through the resistor R2, the first end of the resistor R1 is connected to the non-inverting input terminal of the operational amplifier U2, and the second end of the resistor R1 is connected to the non-inverting input terminal of the operational amplifier U1.

[0043] In this embodiment, the variable resistor RP1, resistor R1, and resistor R2 are connected in series to form a voltage divider circuit, with resistors R1 and R2 dividing the voltage of the VCC power supply. Since the resistance of the variable resistor RP1 can be adjusted, the equivalent resistance of the entire series circuit can be changed by adjusting the resistance of RP1, thereby changing the voltage across resistor R1.

[0044] Among them, the voltage across resistor R2 is the first reference voltage, and the voltages across resistors R1 and R2 are the second reference voltages.

[0045] like Figure 2As shown, in one embodiment of this disclosure, the charging mode switching module includes: a D flip-flop, transistors Q2, Q3, and Q4, resistor R4, operational amplifier U4, and resistor R6; the input terminal of D flip-flop U3 is connected to the output terminal of operational amplifier U1, the output terminal of operational amplifier U2 is connected to the clock terminal of D flip-flop U3, the first output terminal of D flip-flop U3 is connected to the base of transistor Q2, the collector of transistor Q2 is connected to the VCC power supply, and the emitter of transistor Q2 is connected to the non-inverting input terminal of operational amplifier U4; resistor R6... R4 is connected in parallel between the collector and emitter of transistor Q2; the second output of D flip-flop U3 is connected to the base of transistor Q3, the emitter of transistor Q3 is used to connect to the signal generator, the collector of transistor Q3 is connected to the inverting input of operational amplifier U4, the output of operational amplifier U4 is connected to the control terminal of the charging control module; the base of transistor Q4 is connected to the base of transistor Q3, the collector of transistor Q4 is connected to the feedback terminal of the charging control module, and the emitter of transistor Q4 is connected to the inverting input of operational amplifier U4.

[0046] In this embodiment, when the battery pack voltage is less than the first reference voltage, both operational amplifiers U1 and U2 output a high level, the input and clock terminals of D flip-flop U3 are both low, the first output terminal of D flip-flop U3 outputs a high level, the second output terminal of D flip-flop U3 outputs a low level, transistors Q2 and Q3 are both turned on, and transistor Q4 is turned off. At this time, the non-inverting input terminal of operational amplifier U4 is connected to VCC, and the inverting input terminal of operational amplifier U4 receives the sawtooth wave signal output by the signal generator. Operational amplifier U4 forms a comparator, compares the sawtooth wave with the VCC power supply, and then outputs a pulse signal. This pulse signal is applied to the control terminal of the charging control module, and the charging control module controls the battery pack to charge based on the pulse signal output by operational amplifier U4.

[0047] After the battery pack is charged in pulse form (trickle charging mode) for a period of time, the voltage output by the voltage detection module begins to increase. When the voltage output by the voltage detection module is greater than the first reference voltage and less than the second reference voltage, operational amplifier U1 outputs a low level, operational amplifier U2 outputs a high level, and at this time, the first output terminal of D flip-flop U3 changes from high level to low level, and the second output terminal of D flip-flop U3 changes from low level to high level. Transistor Q2 is cut off, transistor Q3 is cut off, and transistor Q4 is turned on. At this time, operational amplifier U4 and resistor R4 form a comparator amplifier. The VCC power supply is applied to the non-inverting input terminal of operational amplifier U4 after resistor R4, and the inverting input terminal of operational amplifier U4 receives the voltage signal from the feedback terminal of the charging control module. Figure 2As shown, during the battery pack charging process, a voltage is generated across resistor R6. Resistor R6 is connected in series with the battery pack. When the charging current of the battery pack changes, the voltage across resistor R6 changes. The change in voltage across resistor R6 can be used to determine whether the charging current of the battery pack has changed. Based on the voltage across resistor R6, the output voltage of operational amplifier U4 is changed, thereby regulating the charging current of the battery pack and achieving constant current charging.

[0048] like Figure 2 As shown, in one embodiment of this disclosure, the charging control module includes: a switch Q1 and a resistor R6; the control terminal of the switch Q1 is connected to the output terminal of the charging mode switching module, the first terminal of the switch Q1 is connected to the VCC power supply, the second terminal of the switch Q1 is connected to the positive terminal of the battery pack, and the negative terminal of the battery pack is grounded through the resistor R6.

[0049] In this embodiment, when the battery pack is operating in trickle charging mode, the operational amplifier U4 outputs a pulse signal, and the switching transistor Q1 is turned on or off under the action of the pulse signal, so that the battery pack is charged in the form of pulses. At this time, the switching transistor Q1 is in the switching state.

[0050] When the battery pack operates in constant current charging mode, the operational amplifier U4 outputs an analog voltage signal, the switching transistor Q1 is turned on, and the switching transistor Q1 operates in the amplification state.

[0051] When the charging current of the battery pack increases, the voltage across resistor R6 increases, the voltage at the inverting input of operational amplifier U4 increases, while the voltage at the non-inverting input remains unchanged. Therefore, the output voltage of operational amplifier U4 decreases, and the voltage at the control terminal of switching transistor Q1 decreases, thereby reducing the current flowing through the battery pack. In this embodiment, the battery pack is represented by P1. Similarly, when the charging current of the battery pack decreases, the output voltage of operational amplifier U4 increases, the voltage at the control terminal of switching transistor Q1 increases, and the current flowing through the battery pack increases, thus ensuring that the charging current of battery pack P1 remains stable.

[0052] like Figure 2 As shown, in one embodiment of this disclosure, the voltage detection module includes: resistor R11, resistor R9, capacitor C1, operational amplifier U5, and resistor R10; the first end of resistor R11 is connected to the negative terminal of the battery pack, the second end of resistor R11 is connected to the inverting input terminal of operational amplifier U5, the first end of resistor R9 is connected to the positive terminal of the battery pack, the second end of resistor R9 is grounded through capacitor C1, the second end of resistor R9 is connected to the non-inverting input terminal of operational amplifier U5, the output terminal of operational amplifier U5 is connected to the inverting input terminal of operational amplifier U5 through resistor R10, and the output terminal of operational amplifier U5 is connected to the inverting input terminals of operational amplifiers U1 and U2.

[0053] In this embodiment, the voltage across the battery pack P1 is applied to the two input terminals of operational amplifier U5. Resistor R9 and capacitor C1 form a circuit for acquiring and filtering the positive voltage of the battery pack, which is used to filter out possible high-frequency noise and smooth the voltage signal. Operational amplifier U5 forms an amplification circuit, and finally the amplified voltage is sent to the inverting input terminals of operational amplifiers U1 and U2 respectively. Based on the comparison result, the output levels of operational amplifiers U1 and U2 are determined, which in turn affects the switching of charging mode by the charging mode switching module.

[0054] like Figure 1 As shown, in one embodiment of this disclosure, it further includes: an overcharge protection module; the first end of the overcharge protection module is connected to the output end of the comparison module, and the second end of the overcharge protection module is connected to the control end of the charging control module.

[0055] In this embodiment, the overcharge protection module can receive feedback information generated by the charging mode switching module during the charging process. This feedback information is the electrical signal output by operational amplifiers U1 and U2. Once an overcharge risk is detected, the overcharge protection module sends a corresponding control signal to the control terminal of the charging control module to limit or cut off the charging current, preventing the battery pack from being overcharged. For example, it can completely cut off the output of the charging control module to terminate the charging process, thereby protecting the battery pack from damage caused by overcharging.

[0056] like Figure 2 As shown, in one embodiment of this disclosure, the overcharge protection module includes: an NOT gate U6, an NOT gate U8, an AND gate U9, and a transistor Q5; the input terminal of the NOT gate U6 is connected to the output terminal of the operational amplifier U1, the output terminal of the NOT gate U6 is connected to the first input terminal of the AND gate U9, the input terminal of the NOT gate U8 is connected to the output terminal of the operational amplifier U2, the output terminal of the NOT gate U8 is connected to the second input terminal of the AND gate U9, the output terminal of the AND gate U9 is connected to the base of the transistor Q5, the collector of the transistor Q5 is connected to the control terminal of the charging control module, and the emitter of the transistor Q5 is grounded.

[0057] In this embodiment, when the battery pack has not reached an overcharge state, the output levels of operational amplifiers U1 and U2 depend on the comparison result between the battery pack voltage and the reference voltage. If the battery pack has not reached the overcharge voltage, the output levels of operational amplifiers U1 and U2 may be different combinations (such as the level combinations in trickle or constant current charging modes mentioned earlier). After passing through NOT gates U6 and U8, their outputs will also be correspondingly different level combinations, but at this time, AND gate U9 will not output a high level. For example, during the trickle or constant current charging stage, operational amplifiers U1 or U2 may output a high level, and after passing through NOT gates U6 or U8, they will output a low level. AND gate U9 will output a low level, transistor Q5 will be in the cutoff state, the charging control module will work normally, and the battery pack will continue to charge.

[0058] When the charging voltage of battery pack P1 reaches the set value, the voltage signal output by operational amplifier U5 is greater than the reference voltages at the non-inverting inputs of operational amplifiers U1 and U2, causing both operational amplifiers U1 and U2 to output a low level. At this time, NOT gate U6 inverts the low-level signal of operational amplifier U1 and outputs a high level; NOT gate U8 inverts the low-level signal of operational amplifier U2 and also outputs a high level. Since both inputs of AND gate U9 receive high-level signals, according to the logic characteristics of AND gates, AND gate U9 outputs a high level. When AND gate U9 outputs a high level, transistor Q5 conducts, thereby grounding the control terminal of the charging control module, stopping the control terminal of the charging control module from working, and stopping the battery pack from charging.

[0059] As can be seen from the above, the overcharge protection module performs logical processing on the outputs of operational amplifiers U1 and U2, and uses NOT and AND gates to pull down the control terminal of the charging control module by turning on the transistor when the battery pack charging voltage reaches the set overcharge threshold, thereby forcibly stopping the operation of the charging control module and thus achieving overcharge protection for the battery pack.

[0060] The above embodiments are only used to illustrate the technical solutions of this disclosure, and are not intended to limit it. Although this disclosure has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to 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 of the embodiments of this disclosure.

Claims

1. A battery pack charging system, characterized by, include: Reference voltage module, comparison module, charging mode switching module, charging control module, and voltage detection module; The reference terminal of the comparison module is connected to the reference voltage module, the output terminal of the comparison module is connected to the input terminal of the charging mode switching module, the output terminal of the charging mode switching module is connected to the control terminal of the charging control module, and the output terminal of the charging control module is connected to the battery pack. The input terminal of the voltage detection module is connected to the feedback terminal of the charging control module, and the output terminal of the voltage detection module is connected to the input terminal of the comparison module. The charging mode switching module is configured to switch the charging mode of the battery pack according to the electrical signal output by the comparison module.

2. The battery pack charging system of claim 1, wherein, The comparison module includes: operational amplifier U1 and operational amplifier U2; The inverting input terminals of both operational amplifier U1 and operational amplifier U2 are connected to the output terminal of the voltage detection module. The non-inverting input terminal of the operational amplifier U1 is used to connect to the first reference voltage of the reference voltage module, and the non-inverting input terminal of the operational amplifier U2 is used to connect to the second reference voltage of the reference voltage module. The output terminals of both operational amplifier U1 and operational amplifier U2 are connected to the input terminal of the charging mode switching module. The second reference voltage is greater than the first reference voltage.

3. The battery pack charging system of claim 2, wherein, The reference voltage module includes: a variable resistor RP1, a resistor R1, and a resistor R2; The first end of the variable resistor RP1 is connected to the VCC power supply, the second end of the variable resistor RP1 is connected to the first end of the resistor R1, the second end of the resistor R1 is grounded through the resistor R2, the first end of the resistor R1 is connected to the non-inverting input terminal of the operational amplifier U2, and the second end of the resistor R1 is connected to the non-inverting input terminal of the operational amplifier U1.

4. The battery pack charging system of claim 2, wherein, The charging mode switching module includes: a D flip-flop, transistors Q2, Q3, and Q4, resistor R4, operational amplifier U4, and resistor R6; The input terminal of the D flip-flop U3 is connected to the output terminal of the operational amplifier U1, the output terminal of the operational amplifier U2 is connected to the clock terminal of the D flip-flop U3, the first output terminal of the D flip-flop U3 is connected to the base of the transistor Q2, the collector of the transistor Q2 is connected to the VCC power supply, the emitter of the transistor Q2 is connected to the non-inverting input terminal of the operational amplifier U4, and the resistor R4 is connected in parallel between the collector and emitter of the transistor Q2. The second output terminal of the D flip-flop U3 is connected to the base of the transistor Q3, the emitter of the transistor Q3 is used to connect to the signal generator, the collector of the transistor Q3 is connected to the inverting input terminal of the operational amplifier U4, and the output terminal of the operational amplifier U4 is connected to the control terminal of the charging control module. The base of transistor Q4 is connected to the base of transistor Q3, the collector of transistor Q4 is connected to the feedback terminal of the charging control module, and the emitter of transistor Q4 is connected to the inverting input terminal of operational amplifier U4.

5. The battery pack charging system of claim 2, wherein, The charging control module includes: a switching transistor Q1 and a resistor R6; The control terminal of the switching transistor Q1 is connected to the output terminal of the charging mode switching module. The first terminal of the switching transistor Q1 is connected to the VCC power supply, and the second terminal of the switching transistor Q1 is connected to the positive terminal of the battery pack. The negative terminal of the battery pack is grounded through the resistor R6.

6. The battery pack charging system of claim 2, wherein, The voltage detection module includes: resistor R11, resistor R9, capacitor C1, operational amplifier U5, and resistor R10; The first end of resistor R11 is connected to the negative terminal of the battery pack, and the second end of resistor R11 is connected to the inverting input terminal of operational amplifier U5. The first end of resistor R9 is connected to the positive terminal of the battery pack, and the second end of resistor R9 is grounded through capacitor C1. The second end of resistor R9 is connected to the non-inverting input terminal of operational amplifier U5. The output terminal of operational amplifier U5 is connected to the inverting input terminal of operational amplifier U5 through resistor R10. The output terminal of operational amplifier U5 is connected to the inverting input terminals of operational amplifiers U1 and U2.

7. The battery pack charging system of claim 4, wherein, Also includes: Overcharge protection module; The first end of the overcharge protection module is connected to the output end of the comparison module, and the second end of the overcharge protection module is connected to the control end of the charging control module.

8. The battery pack charging system of claim 7, wherein, The overcharge protection module includes: NOT gate U6, NOT gate U8, AND gate U9 and transistor Q5; The input terminal of NOT gate U6 is connected to the output terminal of operational amplifier U1, the output terminal of NOT gate U6 is connected to the first input terminal of AND gate U9, the input terminal of NOT gate U8 is connected to the output terminal of operational amplifier U2, the output terminal of NOT gate U8 is connected to the second input terminal of AND gate U9, the output terminal of AND gate U9 is connected to the base of transistor Q5, the collector of transistor Q5 is connected to the control terminal of the charging control module, and the emitter of transistor Q5 is grounded.

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