Charging circuit and electronic equipment

Abstract

The present application discloses a charging circuit and an electronic device, belonging to the field of charging technology. The charging circuit is applied to an electronic device, the electronic device includes a battery module, and the charging circuit includes a half-voltage charging circuit, a pre-charge charging circuit and a constant-voltage charging circuit; the input end of the half-voltage charging circuit is used to connect to an external power supply, and the output end of the half-voltage charging circuit is respectively connected to the input end of the pre-charge charging circuit, the input end of the constant-voltage charging circuit and the battery module; the output end of the pre-charge charging circuit is connected to the battery module; the output end of the constant-voltage charging circuit is connected to the battery module. By reusing the existing half-voltage charging circuit and adding a voltage feedback loop and a current monitoring circuit on its basis, the voltage stabilization and feedback functions can be realized to achieve fast charging, simplifying the circuit structure and saving space for electronic equipment.

Description

Technical Field

[0001] The present application belongs to the field of charging technology, and specifically relates to a charging circuit and an electronic device. Background Art

[0002] With the development of communication technology, electronic devices have higher and higher configurations, more and more functions, and faster and faster power consumption. Users' demand for charging speed is also gradually increasing, and they are generally charged by fast charging or super fast charging. Fast charging basically uses a charge pump half-voltage charging system, which has high charging efficiency and is applied to fast charging and high current charging. However, since half-voltage charging is an open-loop system, the working principle is to use an open-loop charge pump, which does not have voltage stabilization and feedback functions. In the pre-charging stage and the constant voltage stage, it needs to switch to a step-down conversion circuit (buck) for charging.

[0003] Due to users' demands for electronic devices to be thin and light with multiple functions, the space for electronic devices is relatively tight. However, to achieve fast charging of charge pump half-voltage charging, it is necessary to add buck charging chips, power inductors and related components on the basis of charge pump half-voltage charging chips, which affects the thin and light, miniaturized design of electronic devices and also increases costs. Summary of the invention

[0004] The embodiments of the present application provide a charging circuit and an electronic device, which can solve the problem in the prior art that fast charging requires two chips, occupies space in the electronic device, and is difficult to design.

[0005] In a first aspect, an embodiment of the present application provides a charging circuit, which is applied to an electronic device, wherein the electronic device includes a battery module, and the charging circuit includes: a half-voltage charging circuit, a pre-charge charging circuit, and a constant-voltage charging circuit;

[0006] The input end of the half-voltage charging circuit is used to connect to an external power supply, and the output end of the half-voltage charging circuit is respectively connected to the input end of the pre-charge circuit, the input end of the constant voltage charging circuit and the battery module; the output end of the pre-charge circuit is connected to the battery module; the output end of the constant voltage charging circuit is connected to the battery module;

[0007] Among them, in the first charging stage, the half-voltage charging circuit is connected to the pre-charging circuit, and the external power supply charges the battery module through the half-voltage charging circuit and the pre-charging circuit; in the second charging stage, the half-voltage charging circuit is turned on, and the external power supply charges the battery module through the half-voltage charging circuit; in the third charging stage, the half-voltage charging circuit and the constant-voltage charging circuit are turned on, and the external power supply charges the battery module through the half-voltage charging circuit and the constant-voltage charging circuit.

[0008] In a second aspect, an embodiment of the present application provides an electronic device, comprising the charging circuit described in the first aspect.

[0009] A charging circuit is disclosed in an embodiment of the present application, which includes a half-voltage charging circuit, a pre-charge charging circuit and a constant-voltage charging circuit; the input end of the half-voltage charging circuit is used to connect to an external power supply, the output end of the half-voltage charging circuit is respectively connected to the input end of the pre-charge charging circuit, the input end of the constant-voltage charging circuit and the battery, the output end of the pre-charge charging circuit is connected to the battery module, and the output end of the constant-voltage charging circuit is connected to the battery module; wherein, in a first charging stage, the half-voltage charging circuit and the pre-charge charging circuit are turned on, and the external power supply charges the battery module through the half-voltage charging circuit and the pre-charge charging circuit; in a second charging stage, the half-voltage charging circuit is turned on, and the external power supply charges the battery module through the half-voltage charging circuit; in a third charging stage, the half-voltage charging circuit and the constant-voltage charging circuit are turned on, and the external power supply charges the battery module through the half-voltage charging circuit and the constant-voltage charging circuit. The present application realizes the voltage stabilization and feedback functions by reusing the existing half-voltage charging circuit and adding a voltage feedback loop and a current monitoring circuit thereon. There is no need to add a step-down conversion circuit charging chip and its related circuits, and the pre-charging stage, constant current charging stage and constant voltage charging stage in the fast charging process can be completed, saving space for electronic equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0011] Figure 1 is a structural block diagram of a charging circuit provided by an embodiment of the present application;

[0012] Figure 2 It is a circuit diagram of a charging circuit provided by an embodiment of the present application.

[0013] Among them, 10-half-voltage charging circuit; 20-pre-charge charging circuit; 30-constant-voltage charging circuit; 40-battery module. DETAILED DESCRIPTION

[0014] The following will be combined with the drawings in the embodiments of the present application to clearly describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments in the present application belong to the scope of protection of this application.

[0015] The terms "first", "second", etc. in the specification and claims of the present application are used to distinguish similar objects, and are not used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable under appropriate circumstances, so that the embodiments of the present application can be implemented in an order other than those illustrated or described here. In addition, the "and / or" in the specification and claims represents at least one of the connected objects, and the character " / " generally represents that the objects associated with each other are in an "or" relationship.

[0016] The following is combined with Figure 1-2 , a charging circuit and an electronic device provided in an embodiment of the present application are described in detail through specific embodiments and their application scenarios.

[0017] like Figure 1 As shown in FIG. 1 , it is a structural block diagram of a charging circuit provided in an embodiment of the present application. Figure 1 As shown, the charging circuit is applied to an electronic device, and the electronic device includes a battery module 40. The charging circuit may include: a half-voltage charging circuit 10, a pre-charge charging circuit 20 and a constant voltage charging circuit 30.

[0018] Specifically, the input end of the half-voltage charging circuit 10 is used to connect to an external power supply, and the output end of the half-voltage charging circuit 10 is respectively connected to the input end of the pre-charging circuit 20, the input end of the constant voltage charging circuit 30 and the battery module 40, the output end of the pre-charging circuit 20 is connected to the battery module 40, and the output end of the constant voltage charging circuit 30 is connected to the battery module 40.

[0019] Among them, in the first charging stage, the half-voltage charging circuit 10 and the pre-charging circuit 20 are turned on, and the external power supply charges the battery module 40 through the half-voltage charging circuit 10 and the pre-charging circuit 20; in the second charging stage, the half-voltage charging circuit 10 is turned on, and the external power supply charges the battery module 40 through the half-voltage charging circuit 10; in the third charging stage, the half-voltage charging circuit 10 and the constant-voltage charging circuit 30 are turned on, and the external power supply charges the battery module 40 through the half-voltage charging circuit 10 and the constant-voltage charging circuit 30.

[0020] The half-voltage charging circuit 10 can be connected to a power source through a charging interface, that is, the power source charges the battery module 40 through the charging interface and the charging circuit.

[0021] It is worth noting that the first charging stage can be a pre-charging stage, at which time the charging circuit performs low-current charging, and does not require real-time monitoring by a microcontroller. It only needs to output a constant voltage, which can avoid long-term damage to the battery caused by high-current charging. The second charging stage can be a constant-current charging stage, which is a half-voltage charging stage. The output voltage is higher than twice the battery voltage, and then the battery module 40 is charged with a constant current. The third stage can be a constant-voltage charging stage, in which the system output voltage remains constant, so that the charging current gradually decreases to the cut-off current and stops charging. No external microcontroller is required for real-time monitoring, and only a constant voltage needs to be output.

[0022] In an embodiment of the present application, the charging circuit includes a half-voltage charging circuit 10, a pre-charge charging circuit 20 and a constant-voltage charging circuit 30; the input end of the half-voltage charging circuit 10 is used to connect to an external power supply, and the output end of the half-voltage charging circuit 10 is respectively connected to the output end of the pre-charge charging circuit 20, the output end of the constant-voltage charging circuit 30 and the battery module, the output end of the pre-charge charging circuit 20 is connected to the battery module 40, and the output end of the constant-voltage charging circuit 30 is connected to the battery module 40; wherein, in a first charging stage, the half-voltage charging circuit 10 is turned on with the pre-charge charging circuit 20, and the external power supply charges the battery module 40 through the half-voltage charging circuit 10 and the pre-charge charging circuit 20; in a second charging stage, the half-voltage charging circuit 10 is turned on, and the external power supply charges the battery module 40 through the half-voltage charging circuit 10; in a third charging stage, the half-voltage charging circuit 10 and the constant-voltage charging circuit 30 are turned on, and the external power supply charges the battery module 40 through the half-voltage charging circuit 10 and the constant-voltage charging circuit 30. The present application realizes the voltage stabilization and feedback functions by reusing the existing half-voltage charging circuit and adding a voltage feedback loop and a current monitoring circuit thereon. There is no need to add a step-down conversion circuit charging chip and its related circuits, and the pre-charging stage, constant current charging stage and constant voltage charging stage in the fast charging process can be completed, saving space for electronic equipment.

[0023] It is worth noting that the charging circuit may include a microcontroller.

[0024] The microcontroller is connected to the half-voltage charging circuit 10 , and the microcontroller is used to output a control signal to the half-voltage charging circuit 10 to control the conduction or disconnection of the half-voltage charging circuit 10 .

[0025] In the embodiment of the present application, the microcontroller outputs a control signal to the half-voltage charging circuit 10 to control its working state. When fast charging is required, the half-voltage charging circuit 10 can be controlled to work to charge the battery module 40. When charging is completed, the half-voltage charging circuit 10 is controlled to disconnect and end charging.

[0026] In a possible implementation manner of the present application, the half-voltage charging circuit 10 may include: a first capacitor C1, a charging path, and a discharging path.

[0027] In the first time period of the second charging stage, the external power source charges the first capacitor C1 through the charging path; in the second time period of the second charging stage, the first capacitor C1 charges the battery module 40 through the discharging path.

[0028] That is, the half-voltage charging circuit 10 has two working modes, that is, when the half-voltage charging circuit 10 is working, the charging stage and the discharging stage of the first capacitor C1 can be performed alternately, thereby achieving the effect of halving the voltage and doubling the current to reduce the voltage of the charging interface.

[0029] like Figure 2 As shown, the input voltage is VIN, the input current is Iin, the output voltage is VOUT, and the output current is Iout. In the operation of the entire circuit, the charging and discharging of the first capacitor C1 is controlled by controlling the state of the switch tube. Since the duty cycle of the on-cycle and the off-cycle of the switch tube is 50% in the switching cycle, the function of halving the voltage and doubling the current is achieved, that is, VOUT = VIN / 2, Iout = 2*Iin.

[0030] In a specific implementation of the present application, the charging path may include: a first switch tube Q1 and a third switch tube Q3.

[0031] Among them, the first end of the first switch tube Q1 is connected to the external power supply, the first end of the first switch tube Q1 is connected to the pre-charge charging circuit 20, the second end of the first switch tube Q1 is respectively connected to the first end of the first capacitor C1 and the pre-charge charging circuit 20, the second end of the first capacitor C1 is connected to the first end of the third switch tube Q3, the second end of the third switch tube Q3 is respectively connected to the first end of the battery module 40 and the constant voltage charging circuit 30, the second end of the battery module 40 is grounded, the control end of the first switch tube Q1 and the control end of the third switch tube Q3 are both connected to the controller of the electronic device, and the controller controls the conduction and shutdown of the first switch tube Q1 and the third switch tube Q3.

[0032] That is, the controller controls the first switch tube Q1 and the third switch tube Q3 to be turned on to charge the first capacitor C1.

[0033] Specifically, the charging path is during the on-cycle of the switch tubes, the first switch tube Q1 and the third switch tube Q3 are turned on, and the second switch tube Q2 and the fourth switch tube Q4 are turned off, which is equivalent to VIN charging the first capacitor C1.

[0034] In the embodiment of the present application, the controller controls the first switch tube Q1 and the third switch tube Q3 to be turned on, and controls the second switch tube Q2 and the fourth switch tube Q4 to be turned off, so as to form a charging path to charge the first capacitor C1, which is the charging stage of the half-voltage charging circuit 10.

[0035] Furthermore, the charging path may also include: a second capacitor and a third capacitor.

[0036] Specifically, the first end of the second capacitor C2 is respectively connected to the external power supply and the first end of the first switch tube Q1, and the second end of the second capacitor C2 is grounded; the first end of the third capacitor C3 is respectively connected to the second end of the third switch tube Q3 and the first end of the battery module, and the second end of the third capacitor C3 is grounded.

[0037] The second capacitor C2 and the third capacitor C3 are both filter capacitors used for filtering.

[0038] In a specific implementation of the present application, the discharge path may include: a second switch tube Q2 and a fourth switch tube Q4.

[0039] Among them, the first end of the second switch tube Q2 is connected to the first end of the first capacitor C1, the second end of the first capacitor C1 is connected to the first end of the fourth switch tube Q4, the second end of the fourth switch tube Q4 is grounded, the second end of the second switch tube Q2 is respectively connected to the first end of the third capacitor C3 and the first end of the battery module 40, the second end of the third capacitor C3 and the second end of the battery module 40 are both grounded, the control end of the second switch tube Q2 is respectively connected to the controller, the pre-charge circuit and the constant voltage charging circuit 30, the control end of the fourth switch tube Q4 is connected to the controller, and the controller controls the conduction and shutdown of the second switch tube Q2 and the third switch tube Q3.

[0040] That is, the controller controls the second switch tube Q2 and the fourth switch tube Q4 to be turned on, and the battery module 40 is charged through the first capacitor C1.

[0041] Specifically, in the discharge path, during the off period of the switch tube, the second switch tube Q2 and the fourth switch tube Q4 are turned on, the first switch tube Q1 and the third switch tube Q3 are turned off, and the first capacitor C1 and the third capacitor C3 are connected in parallel to charge the battery module 40 .

[0042] In the embodiment of the present application, the controller controls the second switch tube Q2 and the fourth switch tube Q4 to be turned on, and at the same time controls the first switch tube Q1 and the third switch tube Q3 to be turned off, so that a discharge path is formed, and the first capacitor C1 is discharged, which is the discharge stage of the half-voltage charging circuit 10.

[0043] In some embodiments, super fast charging, for example, a 100W external power supply charges the battery module 40 at 20V / 5A. Through the half-voltage charging circuit 10 of the embodiment of the present application, it can be converted into a low-voltage and high-current of 10V / 10A, achieving safe and fast charging with high conversion rate and low heat generation.

[0044] In a possible implementation manner of the present application, the pre-charge circuit 20 may include: a first amplifier U1 and a second amplifier U2.

[0045] Specifically, a first input end of the first amplifier U1 is connected to a first end of the first switch tube Q1, a second input end of the first amplifier U1 is connected to a second end of the first switch tube Q1, an output end of the first amplifier U1 is connected to a first input end of the second amplifier U2, a first reference voltage is input to a second input end of the second amplifier U2, and an output end of the second amplifier U2 is connected to a control end of the second switch tube Q2;

[0046] Among them, in the first charging stage, the first switch tube Q1 is turned on, the first amplifier U1 amplifies the voltage difference between the two ends of the first switch tube Q1 to obtain a first output voltage, and the second amplifier U2 compares the first output voltage with the first reference voltage and outputs a second output voltage. The second output voltage controls the impedance of the second switch tube Q2 to control the external power supply to be the charging current of the battery module 40.

[0047] In the first charging stage, also known as the pre-charging stage, since the charging circuit performs low-current charging, there is no need for real-time monitoring by the controller. The adapter can simply output a constant output voltage, which also prevents the charging circuit from entering high-current charging, thereby causing long-term damage to the battery.

[0048] When the voltage of the battery module 40 is very low, which is the pre-charging stage, the first switch tube Q1 is controlled to open, and the first amplifier U1 obtains the voltage across the first switch tube Q1 and amplifies it to monitor the current passing through the first switch tube Q1. The amplified value of the first amplifier U1 is compared with the first reference voltage VREF1 through the second amplifier U2, that is, the error amplifier, and then controls the second switch tube Q2 to adjust the impedance of the second switch tube Q2 to achieve low-current charging.

[0049] As the voltage of the battery module 40 gradually increases, the output voltage VOUT of the charging circuit also gradually increases, and the voltage difference between the input voltage and the output voltage of the charging circuit gradually decreases. Since the path impedance is fixed, the charging current becomes smaller, and the voltage amplified by the first amplifier U1 becomes smaller. After being compared with the first reference voltage VREF1, the difference becomes larger, so that the gate-to-source voltage Vgs of the second switch tube Q2 becomes larger, the internal impedance becomes lower, the charging current becomes larger, and the current is kept constant, thereby realizing pre-charging with a small current and constant current.

[0050] Among them, the larger the Vgs is, the smaller the on-resistance of the switch tube is, and the smaller the Vgs is, the larger the on-resistance of the switch tube is.

[0051] In a possible implementation manner of the present application, the pre-charge circuit 20 may further include: a first diode D1.

[0052] The input end of the first diode D1 is connected to the output end of the second amplifier U2 , and the output end of the first diode D1 is connected to the control end of the second switch tube Q2 .

[0053] In this embodiment, the first diode D1 is used to prevent voltage backflow and protect the entire circuit.

[0054] In a possible implementation manner of the present application, the constant voltage charging circuit 30 may include: a third amplifier U3, a first resistor, and a second resistor.

[0055] Specifically, the first input end of the third amplifier U3 is connected to the first end of the first resistor and the first end of the second resistor respectively, the second end of the third amplifier U3 inputs the second reference voltage, the output end of the third amplifier U3 is connected to the control end of the second switch tube Q2, the second end of the first resistor is connected to the second end of the second switch tube Q2, and the second end of the second resistor is grounded.

[0056] Among them, in the third charging stage, the first switch tube Q1 is turned on, and the output voltage of the second switch tube Q2 is divided by the first resistor and the second resistor, and then amplified by the third amplifier U3 with the second reference voltage to obtain a third output voltage. The third output voltage controls the impedance of the second switch tube Q2 to control the external power supply to be the charging voltage of the battery module 40.

[0057] In the third charging stage, the charging output voltage is kept constant, so that the charging current is gradually reduced to the cut-off current and charging is stopped. No external controller is required for real-time monitoring, and the charging circuit can output a constant output voltage.

[0058] As the voltage of the battery module 40 gradually increases, the output voltage VOUT of the charging circuit is equal to the voltage of the battery module 40, and the constant voltage charging stage is entered. Figure 2 As shown, the controller controls the first switch tube Q1 to be fully turned on, and the default output voltage of the second switch tube Q2 is VOUT. After voltage division by the first resistor and the second resistor, the difference between the reference voltage VEFG2 and the second reference voltage VEFG2 is amplified by the third amplifier U3, i.e., the error amplifier, and the second switch tube Q2 is controlled to adjust the impedance to achieve a constant output voltage VOUT.

[0059] As the battery voltage gradually increases, the charging current gradually decreases, and the system output voltage VOUT increases. The voltage increases after being divided by the first resistor and the second resistor through negative feedback, and the difference between the feedback voltage and the second reference voltage VREF2 decreases. After passing through the third amplifier U3, Vgs decreases, so that the impedance of the second switch tube Q2 increases, and the output voltage VOUT is dynamically reduced to avoid the VOUT voltage from becoming high, thereby achieving a constant output voltage.

[0060] In a possible implementation manner of the present application, the constant voltage charging circuit 30 may further include: a second diode D2.

[0061] Specifically, the input end of the second diode D2 is connected to the output end of the third amplifier U3, and the output end of the second diode D2 is connected to the control end of the second switch tube Q2.

[0062] In this embodiment, the second diode D2 is used to prevent voltage backflow and protect the entire circuit.

[0063] In an embodiment of the present application, during the pre-charging stage, the constant voltage charging circuit 30 is in a closed state, during the constant current charging stage, both the pre-charging circuit 20 and the constant voltage charging circuit 30 are in a closed state, and during the constant voltage charging stage, the pre-charging circuit 20 is in a closed state.

[0064] The embodiment of the present application further provides an electronic device, including a battery module 40 and a charging circuit provided by any of the above embodiments, and can achieve the same technical effect, which will not be described here to avoid repetition.

[0065] It should be noted that, in this article, the terms "comprise", "include" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise one..." do not exclude the presence of other identical elements in the process, method, article or device including the element. In addition, it should be pointed out that the scope of the methods and devices in the embodiments of the present application is not limited to performing functions in the order shown or discussed, and may also include performing functions in a substantially simultaneous manner or in reverse order according to the functions involved, for example, the described method may be performed in an order different from that described, and various steps may also be added, omitted, or combined. In addition, the features described with reference to certain examples may be combined in other examples.

[0066] Through the description of the above implementation methods, those skilled in the art can clearly understand that the above-mentioned embodiment methods can be implemented by means of software plus a necessary general hardware platform, and of course by hardware, but in many cases the former is a better implementation method. Based on such an understanding, the technical solution of the present application, or the part that contributes to the prior art, can be embodied in the form of a software product, which is stored in a storage medium (such as ROM / RAM, a magnetic disk, or an optical disk), and includes a number of instructions for a terminal (which can be a mobile phone, a computer, a server, an air conditioner, or a network device, etc.) to execute the methods described in each embodiment of the present application.

[0067] The embodiments of the present application are described above in conjunction with the accompanying drawings, but the present application is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of the present application, ordinary technicians in this field can also make many forms without departing from the purpose of the present application and the scope of protection of the claims, all of which are within the protection of the present application.

Claims

1. A charging circuit, applied to an electronic device, wherein the electronic device comprises a battery module, characterized in that: The charging circuit includes: a half-voltage charging circuit, a pre-charge charging circuit and a constant-voltage charging circuit; The input end of the half-voltage charging circuit is used to connect to an external power supply, and the output end of the half-voltage charging circuit is respectively connected to the input end of the pre-charge circuit, the input end of the constant voltage charging circuit and the battery module; the output end of the pre-charge circuit is connected to the battery module; the output end of the constant voltage charging circuit is connected to the battery module; Wherein, in the first charging stage, the half-voltage charging circuit is connected to the pre-charge charging circuit, and the external power supply charges the battery module through the half-voltage charging circuit and the pre-charge charging circuit; in the second charging stage, the half-voltage charging circuit is connected, and the external power supply charges the battery module through the half-voltage charging circuit; in the third charging stage, the half-voltage charging circuit and the constant-voltage charging circuit are connected, and the external power supply charges the battery module through the half-voltage charging circuit and the constant-voltage charging circuit; The half-voltage charging circuit comprises: a first capacitor, a charging path and a discharging path; The charging path includes: a first switch tube; a first end of the first switch tube is respectively connected to the external power supply and the pre-charge circuit, a second end of the first switch tube is respectively connected to the first end of the first capacitor and the pre-charge circuit, and a control end of the first switch tube is connected to a controller of the electronic device; The discharge path includes: a second switch tube, a first end of the second switch tube is connected to the first end of the first capacitor, a second end of the second switch tube is connected to the first end of the battery module, and a control end of the second switch tube is respectively connected to the controller, the pre-charge circuit and the constant voltage charging circuit; The pre-charge circuit comprises: a first amplifier and a second amplifier; The first input end of the first amplifier is connected to the first end of the first switch tube, the second input end of the first amplifier is connected to the second end of the first switch tube, the output end of the first amplifier is connected to the first input end of the second amplifier, the second input end of the second amplifier inputs a first reference voltage, and the output end of the second amplifier is connected to the control end of the second switch tube.

2. The charging circuit according to claim 1, characterized in that: During a first time period of the second charging stage, the external power supply charges the first capacitor through the charging path; during a second time period of the second charging stage, the first capacitor charges the battery module through the discharging path.

3. The charging circuit according to claim 2, characterized in that: The charging path further includes: a third switch tube; The second end of the first capacitor is connected to the first end of the third switch tube, the second end of the third switch tube is respectively connected to the first end of the battery module and the constant voltage charging circuit, the second end of the battery module is grounded, and the control end of the third switch tube is connected to the controller of the electronic device, and the controller controls the conduction and shutdown of the first switch tube and the third switch tube.

4. The charging circuit according to claim 3, characterized in that: The charging path further includes: a second capacitor and a third capacitor; The first end of the second capacitor is respectively connected to the external power supply and the first end of the first switch tube, and the second end of the second capacitor is grounded; the first end of the third capacitor is respectively connected to the second end of the third switch tube and the first end of the battery module, and the second end of the third capacitor is grounded.

5. The charging circuit according to claim 4, characterized in that: The discharge path further includes: a fourth switch tube; The second end of the first capacitor is connected to the first end of the fourth switch tube, the second end of the fourth switch tube is grounded, the second end of the second switch tube is connected to the first end of the third capacitor, the second end of the third capacitor and the second end of the battery module are both grounded, and the control end of the fourth switch tube is connected to the controller, and the controller controls the conduction and shutdown of the second switch tube and the fourth switch tube.

6. The charging circuit according to claim 5, characterized in that: In the first charging stage, the first switch tube is turned on, the first amplifier amplifies the voltage difference across the first switch tube to obtain a first output voltage, the second amplifier compares the first output voltage with the first reference voltage and outputs a second output voltage, and the second output voltage controls the impedance of the second switch tube to control the external power supply to be the charging current of the battery module.

7. The charging circuit according to claim 6, characterized in that: The pre-charge circuit further includes: a first diode; The input end of the first diode is connected to the output end of the second amplifier, and the output end of the first diode is connected to the control end of the second switch tube.

8. The charging circuit according to claim 5, characterized in that: The constant voltage charging circuit comprises: a third amplifier, a first resistor and a second resistor; The first input end of the third amplifier is connected to the first end of the first resistor and the first end of the second resistor respectively, the second end of the third amplifier inputs the second reference voltage, the output end of the third amplifier is connected to the control end of the second switch tube, the second end of the first resistor is connected to the second end of the second switch tube, and the second end of the second resistor is grounded; Among them, in the third charging stage, the first switch tube is turned on, and the output voltage of the second switch tube is divided by the first resistor and the second resistor, and then compared with the second reference voltage through the third amplifier to obtain a third output voltage. The third output voltage controls the impedance of the second switch tube to control the external power supply to be the charging voltage of the battery module.

9. The charging circuit according to claim 8, characterized in that: The constant voltage charging circuit further includes: a second diode; The input end of the second diode is connected to the output end of the third amplifier, and the output end of the second diode is connected to the control end of the second switch tube.

10. An electronic device, characterized in that: The invention comprises a battery module and a charging circuit as claimed in any one of claims 1 to 9.

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