Battery charging circuit and electronic equipment

Abstract

The utility model discloses a battery charging circuit and electronic equipment, and belongs to the technical field of power electronics. The first voltage sampling circuit samples the voltage of the input direct current so as to output a first sampling voltage; the second voltage sampling circuit samples the charging voltage to output a second sampling voltage; the control circuit outputs a first control signal in response to the condition that the difference between the first sampling voltage and the second sampling voltage is smaller than a preset value; the switching circuit transmits input direct current according to the first control signal; therefore, the instantaneous current is reduced, and the pre-charging time is reduced as much as possible, so that the possibility of damage to the switching circuit is reduced, the service life of the switching circuit is prolonged, and the charging efficiency is also considered.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of power electronics, and particularly relates to a battery charging circuit and an electronic device. BACKGROUND

[0002] During the battery charging process, a capacitor is connected in parallel across the battery. If the main relay is directly closed, the voltage across the capacitor will not change abruptly. At this time, the load is the resistance of the wire and the main relay contact (the resistance is generally less than 20 mΩ), while the battery voltage is usually higher than 300 V. When the main relay is closed, it is equivalent to an instantaneous short circuit, which generates an instantaneous current. The instantaneous current may exceed 15,000 A, which reduces the service life of the main relay and even directly causes damage to the main relay.

[0003] Generally, a pre-charging circuit is arranged in the charging circuit to reduce the possibility of damage to the relay, that is, a current-limiting resistor and a field effect transistor are connected in parallel with the main relay. The microprocessor first opens the field effect transistor to charge the capacitor, and then closes the main relay after a preset time to reduce the instantaneous current. However, it is difficult to accurately set the preset time. If the preset time is too short, the instantaneous current may still damage the main relay, and if the preset time is too long, the battery pre-charging time is long, which reduces the charging efficiency. Therefore, the existing charging circuit cannot balance reliability and charging efficiency. CONTENT OF THE UTILITY MODEL

[0004] The application aims to provide a battery charging circuit and an electronic device, and aims to solve the problem that the existing charging circuit cannot balance reliability and charging efficiency.

[0005] The application embodiment provides a battery charging circuit, which comprises:

[0006] A charging circuit is configured to charge input direct current and output a charging voltage.

[0007] A first voltage sampling circuit is connected with the charging circuit and configured to sample the voltage of the input direct current and output a first sampling voltage.

[0008] A second voltage sampling circuit is connected with the charging circuit and the first voltage sampling circuit and configured to sample the charging voltage and output a second sampling voltage.

[0009] A control circuit is connected with the first voltage sampling circuit and the second voltage sampling circuit and configured to output a first control signal in response to the difference between the first sampling voltage and the second sampling voltage being less than a preset value.

[0010] A switching circuit is connected with the charging circuit, the first voltage sampling circuit, the second voltage sampling circuit and the control circuit and configured to transmit the input direct current according to the first control signal.

[0011] In one of the embodiments, the battery charging circuit further comprises:

[0012] a voltage conversion circuit, connected with the first voltage sampling circuit, the charging circuit, the second voltage sampling circuit, the switch circuit and the control circuit, for converting the charging voltage into a supply voltage;

[0013] a control circuit, specifically for outputting the first control signal in response to a difference between the first sampling voltage and the second sampling voltage being less than a preset value under the excitation of the supply voltage.

[0014] In one of the embodiments, the first voltage sampling circuit and the second voltage sampling circuit each comprises a voltage sampling module.

[0015] In one of the embodiments, the voltage sampling module comprises an operational amplifier, a fifth resistor, a sixth resistor, a seventh resistor and an eighth resistor.

[0016] a first end of the seventh resistor and a first end of the fifth resistor are collectively used as an input end of the first voltage sampling circuit; an output end of the operational amplifier and a first end of the sixth resistor are collectively used as an output end of the voltage sampling module; a second end of the fifth resistor, a second end of the sixth resistor and an inverting input end of the operational amplifier are connected; a second end of the seventh resistor, a first end of the eighth resistor and a non-inverting input end of the operational amplifier are connected; and a second end of the eighth resistor is connected to a power supply ground.

[0017] In one of the embodiments, the charging circuit comprises:

[0018] a voltage output circuit, connected with the switch circuit and the first voltage sampling circuit, for outputting a first voltage according to the input direct current;

[0019] a pre-charging circuit, connected with the switch circuit, the first voltage sampling circuit and the voltage output circuit, for current-limiting the input direct current according to the first voltage to output a first direct current;

[0020] an energy storage circuit, connected with the switch circuit, the first voltage sampling circuit, the second voltage sampling circuit, the pre-charging circuit and the voltage output circuit, for charging according to the first direct current and outputting the charging voltage.

[0021] In one of the embodiments, the charging circuit further comprises:

[0022] The unidirectional conduction circuit is connected with the voltage output circuit, the pre-charge circuit, the switch circuit, the energy storage circuit and the second voltage sampling circuit, and is used for unidirectional conduction of the first direct current.

[0023] The energy storage circuit is specifically used for charging according to the first direct current after unidirectional conduction, and outputting the charging voltage.

[0024] In one of the embodiments, the pre-charge circuit includes a first field effect transistor and a first resistor.

[0025] The first end of the first resistor is used as an input direct current input end of the pre-charge circuit, and is connected with the first voltage sampling circuit, the switch circuit and the switch circuit to input the input direct current; the second end of the first resistor is connected with the drain of the first field effect transistor, and the gate of the first field effect transistor and the source of the first field effect transistor are used as a first voltage input end of the pre-charge circuit, and are connected with the voltage output circuit and the unidirectional conduction circuit to output the first direct current.

[0026] In one of the embodiments, the voltage output circuit includes a first diode, a voltage stabilizing diode, a second capacitor, a second resistor, a third resistor and a fourth resistor.

[0027] The first end of the second resistor is used as an input direct current input end of the voltage output circuit, and is connected with the pre-charge circuit, the first voltage sampling circuit and the switch circuit to input the input direct current; the second end of the second resistor is connected with the anode of the first diode, the cathode of the first diode, the first end of the third resistor, the first end of the fourth resistor, the cathode of the voltage stabilizing diode and the first end of the second capacitor are connected, and the second end of the third resistor, the anode of the voltage stabilizing diode, the second end of the second capacitor and the second end of the fourth resistor are used as a first voltage output end of the voltage output circuit, and are connected with the pre-charge circuit and the unidirectional conduction circuit to output the first voltage.

[0028] In one of the embodiments, the control circuit includes a microprocessor.

[0029] The first general input and output end of the microprocessor is connected with the first voltage sampling circuit as the first sampling voltage input end of the control circuit to input the first sampling voltage; the second general input and output end of the microprocessor is connected with the second voltage sampling circuit as the second sampling voltage input end of the control circuit to input the second sampling voltage; the third general input and output end of the microprocessor is connected with the switch circuit as the first control signal output end of the control circuit to output the first control signal; and the power supply end of the microprocessor is connected with the voltage conversion circuit as the power supply voltage input end of the control circuit to input the power supply voltage.

[0030] The embodiment of the present application also provides an electronic device, which comprises the battery charging circuit.

[0031] Compared with the prior art, the embodiment of the present application has the beneficial effects that when the difference between the first sampling voltage and the second sampling voltage is less than the preset value, the control circuit outputs the first control signal to open the switch circuit, thereby reducing the instantaneous current, and in response to the difference between the first sampling voltage and the second sampling voltage being less than the preset value, the first control signal is outputted, which reduces the time of pre-charging as much as possible while reducing the instantaneous current, thereby reducing the possibility of damage of the switch circuit, prolonging the service life of the switch circuit, and taking into account the charging efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description only show some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative effort.

[0033] Figure 1 A structural schematic diagram of the battery charging circuit provided by an embodiment of the present application;

[0034] Figure 2 Another structural schematic diagram of the battery charging circuit provided by an embodiment of the present application;

[0035] Figure 3 Another structural schematic diagram of the battery charging circuit provided by an embodiment of the present application;

[0036] Figure 4 Another structural schematic diagram of the battery charging circuit provided by an embodiment of the present application;

[0037] Figure 5 A partial example circuit schematic diagram of the battery charging circuit provided by an embodiment of the present application. DETAILED DESCRIPTION

[0038] In order to make the technical problems to be solved, technical solutions and beneficial effects of the present application clearer, the present application will be further described in detail below in conjunction with the drawings and embodiments. It should be understood that the specific embodiments described herein are only intended to explain the present application, and not to limit the present application.

[0039] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0040] It should be understood that the terms "length", "width", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the purpose of facilitating the description of the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0041] In addition, the terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second", etc. can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise specifically limited.

[0042] Figure 1 The structure of the battery charging circuit provided by an embodiment of the present application is shown in the structural schematic diagram. For the purpose of illustration, only the parts related to the present embodiment are shown, and the details are as follows:

[0043] The above-mentioned battery charging circuit includes a charging circuit 10, a first voltage sampling circuit 20, a second voltage sampling circuit 30, a control circuit 40, and a switching circuit 50.

[0044] The charging circuit 10 is used for charging the input DC and outputting a charging voltage.

[0045] The first voltage sampling circuit 20 is connected with the charging circuit 10, and is used for sampling the voltage of the input DC to output a first sampling voltage.

[0046] The second voltage sampling circuit 30 is connected with the pre-charging circuit 12 and the energy storage circuit 13, and is used for sampling the charging voltage to output a second sampling voltage.

[0047] The control circuit 40 is connected with the first voltage sampling circuit 20 and the second voltage sampling circuit 30, and is configured to output a first control signal in response to a difference between the first sampling voltage and the second sampling voltage being less than a preset value.

[0048] The switch circuit 50 is connected with the charging circuit 10, the first voltage sampling circuit 20, the second voltage sampling circuit 30, and the control circuit 40, and is configured to transmit the input direct current according to the first control signal.

[0049] In specific implementation, the preset value can be set according to actual needs, and the first control signal can be a pulse width modulation signal or a level signal.

[0050] As an example but not limitation, as shown in Figure 2 The battery charging circuit further includes a voltage conversion circuit 60.

[0051] The voltage conversion circuit 60 is connected with the first voltage sampling circuit 20, the charging circuit 10, the second voltage sampling circuit 30, the switch circuit 50, and the control circuit 40, and is configured to convert the charging voltage into a supply voltage.

[0052] The control circuit 40 is specifically configured to output the first control signal in response to the difference between the first sampling voltage and the second sampling voltage being less than the preset value under the excitation of the supply voltage.

[0053] In specific implementation, the voltage conversion circuit 60 can be a flyback switching power supply circuit. The flyback switching power supply circuit includes an auxiliary power supply control module, a conversion module, and an optocoupler feedback module.

[0054] The auxiliary power supply control module is configured to output a switching signal under the excitation of the charging voltage.

[0055] The conversion module is connected with the auxiliary power supply control module, and is configured to convert the charging voltage into the supply voltage according to the switching signal.

[0056] The optocoupler feedback module is connected with the conversion module and the optocoupler feedback module, and is configured to sample the supply voltage to output a supply voltage sampling signal.

[0057] The auxiliary power supply is specifically configured to output the switching signal according to the supply voltage sampling signal under the excitation of the charging voltage.

[0058] The charging circuit 10 charges according to the input direct current and outputs a charging voltage; the first voltage sampling circuit 20 samples the voltage of the input direct current to output a first sampling voltage; the second voltage sampling circuit 30 samples the charging voltage to output a second sampling voltage; the voltage conversion circuit 60 converts the charging voltage into a supply voltage, the control circuit 40 starts to work based on the supply voltage, and outputs a first control signal to turn on the switch circuit 50 in response to the difference between the first sampling voltage and the second sampling voltage being less than a preset value, so that the control of the switch circuit 50 can be realized without additional independent power supply for the control circuit 40, and the battery charging circuit is simplified.

[0059] As an example but not limitation, the first voltage sampling circuit 20 and the second voltage sampling circuit 30 each include a voltage sampling module.

[0060] As an example but not limitation, as shown in Figure 3 The charging circuit 10 includes a voltage output circuit 11, a pre-charging circuit 12 and an energy storage circuit 13.

[0061] The voltage output circuit 11 is connected with the switch circuit 50 and the first voltage sampling circuit 20, and is configured to output a first voltage according to the input direct current.

[0062] The pre-charging circuit 12 is connected with the switch circuit 50, the first voltage sampling circuit 20 and the voltage output circuit 11, and is configured to limit the current of the input direct current according to the first voltage to output a first direct current.

[0063] The energy storage circuit 13 is connected with the switch circuit 50, the first voltage sampling circuit 20, the second voltage sampling circuit 30, the pre-charging circuit 12 and the voltage output circuit 11, and is configured to charge according to the first direct current and output a charging voltage.

[0064] The possibility of damaging electronic components when the input direct current is too large is reduced by the pre-charging circuit 12, and the safety of the battery charging circuit is improved.

[0065] As an example but not limitation, as shown in Figure 4 The charging circuit 10 further includes a unidirectional conduction circuit 14.

[0066] The unidirectional conduction circuit 14 is connected with the voltage output circuit 11, the pre-charging circuit 12, the energy storage circuit 13 and the second voltage sampling circuit 30, and is configured to conduct the first direct current unidirectionally to output a first direct current after unidirectional conduction.

[0067] The energy storage circuit 13 is specifically configured to charge according to the first direct current after unidirectional conduction and output a charging voltage.

[0068] The possibility of the charging voltage backflowing to the voltage output circuit 11 and the pre-charge circuit 12 is reduced by the unidirectional conducting circuit 14, and the reliability of the battery charging circuit is improved.

[0069] Figure 5 A partial example circuit structure of the battery charging circuit provided by the embodiments of the present application is shown, only the parts related to the embodiments of the present application are shown for the convenience of description, and the details are as follows:

[0070] The voltage sampling module includes an operational amplifier M1, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, and an eighth resistor R8.

[0071] The first end of the seventh resistor R7 and the first end of the fifth resistor R5 are commonly used as the input end of the first voltage sampling circuit; the output end of the operational amplifier and the first end of the sixth resistor R6 are commonly used as the output end of the voltage sampling module; the second end of the fifth resistor R5, the second end of the sixth resistor R6, and the inverting input end of the operational amplifier are connected, the second end of the seventh resistor R7, the first end of the eighth resistor R8, and the non-inverting input end of the operational amplifier are connected, and the second end of the eighth resistor R8 is connected to the power supply ground.

[0072] When the voltage sampling module is applied to the first voltage sampling circuit 20, the input end is connected with the switching circuit 50, the charging circuit 10, and the second voltage sampling circuit 30, and the output end is connected with the control circuit 40.

[0073] When the voltage sampling module is applied to the second voltage sampling circuit 30, the input end is connected with the switching circuit 50, the charging circuit 10, and the second voltage sampling circuit 30, and the output end is connected with the control circuit 40.

[0074] The high-voltage signal is converted into a weak electric signal by the operational amplifier M1, the fifth resistor R5, the sixth resistor R6, the seventh resistor R7, and the eighth resistor R8, and transmitted to the control circuit 40, without the need for additional isolation circuit, thereby reducing the cost of the hardware circuit.

[0075] The voltage output circuit 11 includes a first diode D1, a voltage stabilizing diode Z1, a second capacitor C2, a second resistor R2, a third resistor R3, and a fourth resistor R4.

[0076] The first end of the second resistor R2 is connected with the pre-charge circuit 12, the first voltage sampling circuit 20 and the switch circuit 50 as an input DC input end of the voltage output circuit 11, for inputting input DC; the second end of the second resistor R2 is connected with the anode of the first diode D1, the cathode of the first diode D1, the first end of the third resistor R3, the first end of the fourth resistor R4, the cathode of the voltage stabilizing diode Z1 and the first end of the second capacitor C2, the second end of the third resistor R3, the anode of the voltage stabilizing diode Z1, the second end of the second capacitor C2 and the second end of the fourth resistor R4 are collectively used as a first voltage output end of the voltage output circuit 11, connected with the pre-charge circuit 12 and the unidirectional conduction circuit 14, for outputting a first voltage.

[0077] The circuit is simple and reliable.

[0078] The pre-charge circuit 12 comprises a first field effect transistor Q1 and a first resistor R1.

[0079] The first end of the first resistor R1 is connected with the first voltage sampling circuit 20, the switch circuit 50 and the switch circuit 50 as an input DC input end of the pre-charge circuit 12, for inputting input DC; the second end of the first resistor R1 is connected with the drain of the first field effect transistor Q1, the gate of the first field effect transistor Q1 and the source of the first field effect transistor Q1 are collectively used as a first voltage input end of the pre-charge circuit 12, connected with the voltage output circuit 11 and the unidirectional conduction circuit 14, for outputting a first DC.

[0080] The first resistor R1 is a current-limiting resistor, and the resistance value of the first resistor R1 can be set according to the battery voltage.

[0081] The first field effect transistor Q1 has no mechanical contact and has a long service life.

[0082] The energy storage circuit 13 comprises a first capacitor C1.

[0083] The first end of the first capacitor C1 is connected with the switch circuit 50, the voltage output circuit 11, the pre-charge circuit 12 and the second voltage sampling circuit 30, the second end of the first capacitor C1 is connected with the first voltage sampling circuit 20 and the second voltage sampling circuit 30, and the first end of the first capacitor C1 and the second end of the first capacitor C1 are collectively used as a first DC input end of the energy storage circuit 13 and a charging voltage output end of the energy storage circuit 13, for inputting a first DC and outputting a charging voltage.

[0084] The first capacitor C1 has high energy conversion efficiency.

[0085] The control circuit 40 comprises a microprocessor U1.

[0086] The first general input and output end P1.0 of the microprocessor U1 is connected with the first voltage sampling circuit 20 as the first sampling voltage input end of the control circuit 40 to input the first sampling voltage; the second general input and output end P1.1 of the microprocessor U1 is connected with the second voltage sampling circuit 30 as the second sampling voltage input end of the control circuit 40 to input the second sampling voltage; the third general input and output end P2.0 of the microprocessor U1 is connected with the switching circuit 50 as the first control signal output end of the control circuit 40 to output the first control signal; and the power supply end VCC of the microprocessor U1 is connected with the voltage conversion circuit 60 as the power supply voltage input end of the control circuit 40 to input the power supply voltage.

[0087] The microprocessor U1 has high integration and is convenient to use.

[0088] The switching circuit 50 comprises a relay K1, a second field effect transistor Q2, a third diode D3, a thirteenth resistor R13 and a fourteenth resistor R14.

[0089] The first end of the thirteenth resistor R13 is connected with the control circuit 40 as the first control signal input end of the switching circuit 50 to input the first control signal; the second end of the thirteenth resistor R13, the first end of the fourteenth resistor R14 and the gate of the second field effect transistor Q2 are connected; the first contact of the relay K1 is connected with the first voltage sampling circuit 20 and the charging circuit 10 as the input direct current input end of the switching circuit 50 to input the input direct current; the second contact of the relay K1 is connected with the second voltage sampling circuit 30 and the energy storage circuit 13 as the input direct current output end of the switching circuit 50 to output the input direct current; the first end of the coil of the relay K1, the positive pole of the third diode D3 and the drain of the second field effect transistor Q2 are connected; the second end of the coil of the relay K1, the negative pole of the third diode D3 are connected with the first power supply; and the source of the second field effect transistor Q2 and the second end of the fourteenth resistor R14 are connected to the power supply ground.

[0090] The unidirectional conduction circuit 14 comprises a second diode D2.

[0091] The positive pole of the second diode D2 is connected with the voltage output circuit 11 and the pre-charge circuit 12 as the first direct current input end of the unidirectional conduction circuit 14 to input the first direct current; and the negative pole of the second diode D2 is connected with the switching circuit 50, the energy storage circuit 13 and the second voltage sampling circuit 30 as the first direct current output end after unidirectional conduction of the unidirectional conduction circuit 14 to output the first direct current after unidirectional conduction.

[0092] The working principle of the application will be further described below with reference to the drawings. Figure 5

[0093] ​The input direct current passes through the normally open switch S1, the second resistor R2 and the first diode D1 to the second capacitor C2, the second capacitor C2 is charged, and after a period of time, the voltage across the second capacitor C2 rises to the turn-on voltage of the first field effect transistor Q1, the voltage stabilizing diode Z1 stabilizes the voltage, the voltage across the second capacitor C2 is loaded to the gate of the first field effect transistor Q1 and the source of the first field effect transistor Q1, the first field effect transistor Q1 is turned on, the input direct current passes through the first resistor R1 and the first field effect transistor Q1 and is output to the anode of the second diode D2, the second diode D2 is unidirectionally turned on to the input direct current, and the input direct current after being unidirectionally turned on is output from the cathode of the second diode D2 to the first capacitor C1 and the voltage conversion circuit 60, the first capacitor C1 stores energy according to the input direct current after being unidirectionally turned on, and the voltage conversion circuit 60 converts the input direct current after being unidirectionally turned on into a supply voltage and outputs the supply voltage to the power supply end VCC of the microprocessor U1.

[0094] The first end of the seventh resistor R7 and the first end of the fifth resistor R5 are commonly connected to the input direct current, the operational amplifier M1, the fifth resistor R5, the sixth resistor R6, the seventh resistor R7 and the eighth resistor R8 differentially operate and amplify the input direct current, and output a first sampling voltage from the output end of the operational amplifier M1 and the second end of the sixth resistor R6 to the first general input / output end P1.0 of the microprocessor U1; the second end of the eleventh resistor R11 and the second end of the ninth resistor R9 are connected to the charging voltage, the second operational amplifier M2, the ninth resistor R9, the tenth resistor R10, the eleventh resistor R11 and the twelfth resistor R12 differentially operate and amplify the charging voltage, and output a second sampling voltage from the output end of the second operational amplifier M2 and the second end of the tenth resistor R10 to the second general input / output end P1.1 of the microprocessor U1, the microprocessor U1 responds to the supply voltage, under the excitation of the supply voltage, and in response to the difference between the first sampling voltage and the second sampling voltage being less than a preset value, outputs a first control signal to the first end of the thirteenth resistor R13, the second field effect transistor Q2 is turned on, the coil of the relay K1 is powered, the relay K1 is closed, the input direct current is transmitted to the battery to be charged through the relay K1, thereby completing the pre-charging, reducing the possibility of the instantaneous current flowing through the relay K1 being too large, and improving the reliability of the pre-charging.

[0095] The embodiment of the present application also provides an electronic device, which comprises the above battery charging circuit.

[0096] It should be understood that the size of the serial number of each step in the above embodiment does not mean the order of execution, the execution order of each process should be determined according to its function and inherent logic, and should not constitute any limitation on the implementation process of the embodiment of the present application.

[0097] The above-described embodiments are only used to illustrate the technical solutions of the present application, but not limit them; although the present application is described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement to part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be included in the protection scope of the present application.

Claims

1. A battery charging circuit, characterized by, The application relates to a charging circuit and a voltage sampling circuit. The charging circuit is used for charging input direct current and outputting a charging voltage; The first voltage sampling circuit is connected with the charging circuit and is used for sampling the voltage of the input direct current to output a first sampling voltage; The second voltage sampling circuit is connected with the charging circuit and the first voltage sampling circuit and is used for sampling the charging voltage to output a second sampling voltage; The control circuit is connected with the first voltage sampling circuit and the second voltage sampling circuit and is used for outputting a first control signal in response to the difference between the first sampling voltage and the second sampling voltage being less than a preset value; The switch circuit is connected with the charging circuit, the first voltage sampling circuit, the second voltage sampling circuit and the control circuit and is used for transmitting the input direct current according to the first control signal.

2. The battery charging circuit of claim 1, wherein, The application further relates to a voltage conversion circuit and a control circuit. The voltage conversion circuit is connected with the first voltage sampling circuit, the charging circuit, the second voltage sampling circuit, the switch circuit and the control circuit and is used for converting the charging voltage into a power supply voltage; The control circuit is specifically used for outputting the first control signal in response to the difference between the first sampling voltage and the second sampling voltage being less than the preset value under the excitation of the power supply voltage.

3. The battery charging circuit of claim 1, wherein, The first voltage sampling circuit and the second voltage sampling circuit both comprise a voltage sampling module.

4. The battery charging circuit of claim 3, wherein, The voltage sampling module comprises an operational amplifier, a fifth resistor, a sixth resistor, a seventh resistor and an eighth resistor; The first end of the seventh resistor and the first end of the fifth resistor are used as the input end of the first voltage sampling circuit; the output end of the operational amplifier and the first end of the sixth resistor are used as the output end of the voltage sampling module; the second end of the fifth resistor, the second end of the sixth resistor and the inverting input end of the operational amplifier are connected; the second end of the seventh resistor, the first end of the eighth resistor and the non-inverting input end of the operational amplifier are connected; and the second end of the eighth resistor is connected to a power supply ground.

5. The battery charging circuit of claim 1, wherein, The charging circuit comprises a voltage output circuit, a pre-charging circuit and an energy storage circuit. The voltage output circuit is connected with the switch circuit and the first voltage sampling circuit and is used for outputting a first voltage according to the input direct current; The pre-charging circuit is connected with the switch circuit, the first voltage sampling circuit and the voltage output circuit and is used for limiting the current of the input direct current according to the first voltage to output a first direct current; The energy storage circuit is connected with the switch circuit, the first voltage sampling circuit, the second voltage sampling circuit, the pre-charging circuit and the voltage output circuit and is used for charging according to the first direct current and outputting the charging voltage.

6. The battery charging circuit of claim 5, wherein, The charging circuit further comprises a one-way conduction circuit. The one-way conduction circuit is connected with the voltage output circuit, the pre-charging circuit, the switch circuit, the energy storage circuit and the second voltage sampling circuit and is used for conducting the first direct current in one direction; The energy storage circuit is specifically used for charging according to the first direct current after one-way conduction and outputting the charging voltage.

7. The battery charging circuit of claim 6, wherein, The pre-charging circuit comprises a first field effect transistor and a first resistor; The first end of the first resistor is an input direct current input end of the pre-charge circuit, and is connected with the first voltage sampling circuit, the switch circuit and the switch circuit to input the input direct current; The second end of the first resistor is connected with the drain of the first field effect transistor, and the gate of the first field effect transistor and the source of the first field effect transistor are collectively a first voltage input end of the pre-charge circuit, and are connected with the voltage output circuit and the unidirectional conduction circuit to output the first direct current.

8. The battery charging circuit of claim 6, wherein, The voltage output circuit comprises a first diode, a voltage stabilizing diode, a second capacitor, a second resistor, a third resistor and a fourth resistor; The first end of the second resistor is an input direct current input end of the voltage output circuit, and is connected with the pre-charge circuit, the first voltage sampling circuit and the switch circuit to input the input direct current; the second end of the second resistor is connected with the anode of the first diode, and the cathode of the first diode, the first end of the third resistor, the first end of the fourth resistor, the cathode of the voltage stabilizing diode and the first end of the second capacitor are connected; the second end of the third resistor, the anode of the voltage stabilizing diode, the second end of the second capacitor and the second end of the fourth resistor are collectively a first voltage output end of the voltage output circuit, and are connected with the pre-charge circuit and the unidirectional conduction circuit to output the first voltage.

9. The battery charging circuit of claim 1, wherein, The control circuit comprises a microprocessor; The first general input and output end of the microprocessor is a first sampling voltage input end of the control circuit, and is connected with the first voltage sampling circuit to input the first sampling voltage; the second general input and output end of the microprocessor is a second sampling voltage input end of the control circuit, and is connected with the second voltage sampling circuit to input the second sampling voltage; the third general input and output end of the microprocessor is a first control signal output end of the control circuit, and is connected with the switch circuit to output the first control signal; The power supply end of the microprocessor is a power supply voltage input end of the control circuit, and is connected with the voltage conversion circuit to input the power supply voltage.

10. An electronic device, comprising: The battery charging circuit comprises the battery charging circuit according to any one of claims 1 to 9.

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