Battery charging circuit and camera battery charging device

Abstract

The utility model relates to the technical field of charging, in particular to a battery charging circuit and a camera battery charging device. The battery charging circuit comprises a main control chip, a charging input end, a charging output end and a buck-boost module, and the charging input end is used for inputting an external power supply; the charging output end is used for outputting charging voltage to charge the battery; the buck-boost module comprises a buck switch tube, a first diode, an energy storage inductor and a boost unit, the driving end of the buck switch tube is connected with the main control chip, the first end of the buck switch tube is connected with the charging input end, the second end of the buck switch tube is connected with the first end of the energy storage inductor and the negative electrode of the first diode, and the second end of the energy storage inductor is connected with the boost unit; the boosting unit is connected with the charging output end, and the driving end of the boosting unit is connected with the main control chip. The circuit cost can be reduced to a certain extent.

Description

Technical Field

[0001] The utility model relates to the technical field of charging, in particular to a battery charging circuit and a camera battery charging device. Background Art

[0002] As an energy source, batteries can output relatively stable voltage and current, with stable and reliable performance. They play a great role in all aspects of modern social life. For example, batteries can be used as an energy source for cameras.

[0003] Battery charging circuits typically use a buck-boost topology, which uses two switching transistors to achieve voltage reduction. However, using two switching transistors to achieve voltage reduction is costly. Utility Model Content

[0004] The technical problem to be solved by the embodiments of the present invention is to provide a battery charging circuit and a battery charging device to solve the problem of high cost of battery charging circuits in the prior art.

[0005] The utility model discloses a battery charging circuit, including a main control chip, a charging input terminal, a charging output terminal and a buck-boost module, wherein:

[0006] The charging input terminal is used to input an external power source;

[0007] The charging output terminal is used to output a charging voltage to charge the battery;

[0008] The buck-boost module includes a buck switching tube, a first diode, an energy storage inductor and a boost unit. The driving end of the buck switching tube is connected to the main control chip, the first end of the buck switching tube is connected to the charging input end, the second end of the buck switching tube is connected to the first end of the energy storage inductor and the negative electrode of the first diode, the second end of the energy storage inductor is connected to the boost unit, the positive electrode of the first diode is connected to the ground end, the boost unit is connected to the charging output end and the driving end of the boost unit is connected to the main control chip.

[0009] Optionally, the buck-boost module further includes a buck driving unit, and the buck driving unit is provided between the driving end of the buck switch tube and the main control chip.

[0010] Optionally, the buck switching tube is a first PMOS tube, and the buck driving unit includes a first triode, a second triode and a third triode. The base of the first triode is connected to the main control chip, the collector is connected to the base of the second triode and the base of the third triode, the emitter of the first triode and the collector of the third triode are grounded, the collector of the second triode is connected to the charging input end and the source of the first PMOS tube, the emitter of the second triode is connected to the emitter of the third triode and the gate of the first PMOS tube, and the drain of the first PMOS tube is connected to the first end of the energy storage inductor and the negative electrode of the first diode.

[0011] Optionally, the battery charging circuit further includes a voltage sampling module for collecting a charging voltage, and the voltage sampling module is connected to the charging output terminal and the main control chip.

[0012] Optionally, the battery charging circuit further includes a voltage sampling control module, which is connected to the main control chip and is arranged between the charging output end and the voltage sampling module. The voltage sampling control module is used to connect or disconnect the path between the charging output end and the voltage sampling module.

[0013] Optionally, the voltage sampling control module includes a fourth transistor, a second PMOS transistor and a pull-up resistor, the base of the fourth transistor is connected to the main control chip, the emitter is grounded, the collector is connected to the gate of the second PMOS transistor and one end of the pull-up resistor, the source of the second PMOS transistor is connected to the charging output end and the other end of the pull-up resistor, and the drain is connected to the voltage sampling module.

[0014] Optionally, the battery charging circuit further includes a fast charging protocol chip, and the fast charging protocol chip is connected to the charging input terminal and the main control chip.

[0015] Optionally, the buck-boost module also includes a first energy storage capacitor and a second energy storage capacitor, the positive electrode of the first energy storage capacitor is connected to the charging input end and the first end of the buck switch tube, the positive electrode of the second energy storage capacitor is connected to the boost unit and the charging output end, and the negative electrode of the first energy storage capacitor and the negative electrode of the second energy storage capacitor are both grounded.

[0016] Optionally, the boost unit includes an NMOS tube and a second diode, the gate of the NMOS tube is connected to the main control chip, the source of the NMOS tube is grounded, the drain of the NMOS tube is connected to the second end of the energy storage inductor and the positive electrode of the second diode, and the negative electrode of the second diode is connected to the charging output end and the positive electrode of the second energy storage capacitor.

[0017] The utility model also discloses a camera battery charging device, comprising a storage box, a circuit board, and the battery charging circuit as described above, wherein the storage box is used to store camera batteries, the battery charging circuit is arranged on the circuit board, and the circuit board is arranged in the storage box, and the charging output end of the battery charging circuit outputs a charging voltage to charge the camera battery in the storage box.

[0018] Compared with the prior art, the battery charging circuit and camera battery charging device provided by the embodiments of the present invention have the following beneficial effects: by providing a main control chip, a charging input terminal, a charging output terminal, and a buck-boost module, the buck-boost module includes a buck switching tube, a first diode, an energy storage inductor, and a boost unit, the driving end of the buck switching tube is connected to the main control chip, the first end of the buck switching tube is connected to the charging input terminal, the second end of the buck switching tube is connected to the first end of the energy storage inductor and the negative electrode of the first diode, the second end of the energy storage inductor is connected to the boost unit, the positive electrode of the first diode is connected to the ground terminal, the boost unit is connected to the charging output terminal, and the driving end of the boost unit is connected to the main control chip. The first diode is used in the buck-boost module to replace one of the switching tubes, and the buck switching tube cooperates with the first diode and the energy storage inductor to achieve voltage reduction, thereby reducing circuit cost to a certain extent. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments, in which:

[0020] Figure 1 This is one of the structural block diagrams of the battery charging circuit provided by the embodiment of the present utility model;

[0021] Figure 2 This is the second structural block diagram of the battery charging circuit provided by the embodiment of the present utility model;

[0022] Figure 3 This is a partial circuit diagram of a battery charging circuit provided by an embodiment of the present utility model;

[0023] Figure 4 This is a partial circuit diagram of the main control chip provided by an embodiment of the utility model.

[0024] The reference numerals in the figures are:

[0025] 10 (U1), main control chip; 20, charging input terminal; 30, charging output terminal; 40, buck-boost module; 41, buck switch tube; 42 (D1), first diode; 43 (L1), energy storage inductor; 44, boost unit; 45, buck drive unit; 50, voltage sampling module; 60, voltage sampling control module; 70, current sampling module; 80 (U2), fast charging protocol chip;

[0026] Q1, first PMOS transistor; Q2, first transistor; Q3, second transistor; Q4, third transistor; Q5, fourth transistor; Q6, second PMOS transistor; Q7, NMOS transistor; D2, second diode; R1, first sampling resistor; R2, second sampling resistor; R3, pull-up resistor; R4, third sampling resistor; R5, fourth sampling resistor; C1, filter capacitor; C2, first energy storage capacitor; C3, second energy storage capacitor. DETAILED DESCRIPTION

[0027] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. Now, in conjunction with the accompanying drawings, a detailed description of the preferred embodiments of the present utility model will be given.

[0028] The present invention provides a battery charging circuit. Figure 1 As shown, the battery charging circuit includes a main control chip 10 (U1), a charging input terminal 20, a charging output terminal 30 and a buck-boost module 40.

[0029] The charging input terminal 20 is used to input an external power source, and is connected to the external power source to provide a power source for the battery charging circuit.

[0030] The charging output terminal 30 is used to output a charging voltage to charge the battery.

[0031] The buck-boost module 40 includes a buck switch tube 41, a first diode 42 (D1), an energy storage inductor 43 (L1) and a boost unit 44. The driving end of the buck switch tube 41 is connected to the main control chip 10 (U1), the first end of the buck switch tube 41 is connected to the charging input end 20, the second end of the buck switch tube 41 is connected to the first end of the energy storage inductor 43 (L1) and the negative electrode of the first diode 42 (D1), the second end of the energy storage inductor 43 (L1) is connected to the boost unit 44, the positive electrode of the first diode 42 (D1) is connected to the ground end, the boost unit 44 is connected to the charging output end 30 and the driving end of the boost unit 44 is connected to the main control chip 10 (U1).

[0032] The embodiment of the present invention is provided with a main control chip 10 (U1), a charging input terminal 20, a charging output terminal 30 and a buck-boost module 40. The boost part of the buck-boost module 40 uses a boost unit 44 in conjunction with an energy storage inductor 43 (L1) to achieve boosting, and the buck part uses a first diode 42 (D1) to replace one of the switch tubes. The buck switch tube 41 cooperates with the first diode 42 (D1) and the energy storage inductor 43 (L1) to achieve bucking, which reduces the circuit cost to a certain extent. In addition, the buck switch tube 41 cooperates with the first diode 42 (D1) and the energy storage inductor 43 (L1) to achieve bucking, which can avoid the risk of burning the switch tube due to a short circuit caused by the simultaneous conduction of the two switch tubes that achieve bucking, thereby improving the safety of the overall circuit.

[0033] In an alternative embodiment, reference Figure 2 The buck-boost module 40 further includes a buck driving unit 45 , which is disposed between the driving end of the buck switch tube 41 and the main control chip 10 ( U1 ).

[0034] By setting up a buck driving unit 45, the main control chip 10 (U1) controls the conduction and cutoff of the buck switch tube 41 through the buck driving unit 45, which can ensure that the buck switch tube 41 can be turned on or off, thereby improving the reliability of the circuit.

[0035] In other embodiments, the main control chip 10 (U1) may also be integrated with a driving circuit for driving the buck switch tube 41.

[0036] Further, refer to Figure 2 and Figure 3 The step-down switch tube 41 is a first PMOS tube Q1, and the step-down driving unit 45 includes a first transistor Q2, a second transistor Q3 and a third transistor Q4. The base of the first transistor Q2 is connected to the main control chip 10 (U1), and the collector is connected to the base of the second transistor Q3 and the base of the third transistor Q4. The emitter of the first transistor Q2 and the collector of the third transistor Q4 are grounded. The collector of the second transistor Q3 is connected to the charging input terminal 20 and the source of the first PMOS tube Q1. The emitter of the second transistor Q3 is connected to the emitter of the third transistor Q4 and the gate of the first PMOS tube Q1. The drain of the first PMOS tube Q1 is connected to the first end of the energy storage inductor 43 (L1) and the negative electrode of the first diode 42 (D1).

[0037] By using the first PMOS transistor Q1 as the buck switch 41, in conjunction with the first diode 42 (D1) and the energy storage inductor 43 (L1) to achieve voltage reduction, the first PMOS transistor Q1 has a high input impedance, which means that it is less sensitive to the input signal, can effectively reduce the interference caused by changes in the input signal, and improve the stability of the circuit; secondly, the driving power of the first PMOS transistor Q1 is low, which means that less energy is required to drive the first PMOS transistor Q1, which helps to reduce the energy consumption of the entire circuit.

[0038] By providing a first transistor Q2, a second transistor Q3, and a third transistor Q4 to form a drive circuit, the main control chip 10 (U1) drives the first PMOS transistor Q1 through the drive circuit, thereby achieving precise control of the first PMOS transistor Q1, ensuring its stability and reliability when turning on and off, and improving the efficiency of the circuit.

[0039] In a specific implementation, the first transistor Q2 and the second transistor Q3 are both NPN transistors, and the third transistor Q4 is a PNP transistor.

[0040] During specific operation, the main control chip 10 (U1) outputs a PWM signal. When the PWM signal is at a high level, the first transistor Q2 and the third transistor Q4 are turned on, the second transistor Q3 is turned off, the gate level of the first PMOS transistor Q1 is pulled low, and the first PMOS transistor Q1 is turned on; when the PWM signal is at a low level, the first transistor Q2 and the third transistor Q4 are disconnected, the second transistor Q3 is turned on, the gate level of the first PMOS transistor Q1 is pulled high, and the first PMOS transistor Q1 is turned off.

[0041] In other embodiments, the buck switch 41 may also be an NMOS transistor, with its gate connected to the buck driver 45, its source connected to the charging input 20, and its drain connected to the first terminal of the energy storage inductor 43 (L1) and the cathode of the first diode 42 (D1). The main control chip 10 (U1) drives the NMOS transistor on or off via the corresponding buck driver 45, thereby coordinating with the first diode 42 (D1) and the energy storage inductor 43 (L1) to achieve voltage reduction.

[0042] When an NMOS transistor is used as the buck switch 41, since the source of the NMOS transistor is connected to the charging input terminal 20 and has a higher voltage, its gate requires a higher voltage to drive the NMOS transistor. Therefore, the buck drive unit 45 corresponding to the NMOS transistor requires a more complex buck-boost circuit to provide the higher voltage to drive the NMOS transistor. This embodiment uses a PMOS transistor as the buck switch 41. The circuit of the buck drive unit 45 is simpler, eliminating the need for a complex boost drive circuit design. This improves the timeliness and stability of the control circuit, and further reduces the overall circuit cost.

[0043] refer to Figure 2 In an optional embodiment of the present application, the battery charging circuit further includes a voltage sampling module 50 for collecting the charging voltage. The voltage sampling module 50 is connected to the charging output terminal 30 and the main control chip 10 (U1).

[0044] By providing a voltage sampling module 50, the charging voltage output by the charging output terminal 30, i.e., the charging voltage of the external battery, can be collected and transmitted to the main control chip 10 (U1). The main control chip 10 (U1) adjusts the control of the buck switch 41 and the boost unit 44 based on the collected charging voltage to achieve charging voltage regulation. The main control chip 10 (U1) can use existing chips to implement the control and adjustment of the buck switch 41 and the boost unit 44 based on the collected charging voltage. The software portion of this control does not constitute an improvement of the present invention.

[0045] Specifically, refer to Figures 2 to 4The voltage sampling module 50 includes a first sampling resistor R1 and a second sampling resistor R2. The first sampling resistor R1 and the second sampling resistor R2 are connected in series. The series node between the first sampling resistor R1 and the second sampling resistor R2 is connected to the main control chip 10 (U1). The other end of the first sampling resistor R1 is connected to the charging output terminal 30, and the other end of the second sampling resistor R2 is grounded.

[0046] By providing a first sampling resistor R1 and a second sampling resistor R2 connected in series, the charging voltage of the charging output terminal 30 can be obtained by voltage division sampling, which has a simple circuit structure and low cost.

[0047] In other embodiments, the voltage sampling module 50 may include multiple resistors connected in series, and the series node of two of the resistors is connected to the main control chip 10 (U1) according to the resistance value to transmit the sampled charging voltage to the main control chip 10 (U1).

[0048] refer to Figure 2 In an optional embodiment of the present application, the battery charging circuit further includes a voltage sampling control module 60, which is connected to the main control chip 10 (U1) and is arranged between the charging output terminal 30 and the voltage sampling module 50. The voltage sampling control module 60 is used to connect or disconnect the path between the charging output terminal 30 and the voltage sampling module 50.

[0049] By setting up the voltage sampling control module 60, the path between the charging output terminal 30 and the voltage sampling module 50 can be controlled to be connected or disconnected, so that the voltage sampling of the voltage sampling module 50 can be started or stopped when needed, thereby reducing circuit power consumption and making voltage sampling flexible.

[0050] Specifically, refer to Figures 2 to 4 The voltage sampling control module 60 includes a fourth transistor Q5, a second PMOS transistor Q6, and a pull-up resistor R3. The base of the fourth transistor Q5 is connected to the main control chip 10 (U1), the emitter is grounded, the collector is connected to the gate of the second PMOS transistor Q6 and one end of the pull-up resistor R3, the source of the second PMOS transistor Q6 is connected to the charging output terminal 30 and the other end of the pull-up resistor R3, and the drain is connected to the voltage sampling module 50.

[0051] The fourth transistor Q5, the second PMOS transistor Q6, and the pull-up resistor R3 can receive a level signal from the main control chip 10 (U1), thereby connecting or disconnecting the path between the charging output terminal 30 and the voltage sampling module 50, connecting or disconnecting the discharge circuit formed by the voltage sampling module 50, and starting or stopping voltage sampling by the voltage sampling module 50, thereby reducing circuit power consumption.

[0052] During specific implementation, the fourth transistor Q5 is an NPN transistor.

[0053] During specific operation, the main control chip 10 (U1) outputs a high level, the fourth transistor Q5 is turned on, the gate level of the second PMOS transistor Q6 is pulled low, the second PMOS transistor Q6 is turned on, and the path between the charging output terminal 30 and the voltage sampling module 50 is connected, and the voltage sampling module 50 performs voltage sampling; the main control chip 10 (U1) outputs a low level, the fourth transistor Q5 is turned off, the voltage of the gate of the second PMOS transistor Q6 is pulled high, the second PMOS transistor Q6 is turned off, the path between the charging output terminal 30 and the voltage sampling module 50 is disconnected, the voltage sampling module 50 has no charging voltage input, cannot perform voltage sampling, and stops working.

[0054] When the voltage sampling module 50 specifically adopts the first sampling resistor R1 and the second sampling resistor R2 connected in series, the drain of the second PMOS transistor Q6 is connected to the other end of the first sampling resistor R1 .

[0055] The battery charging circuit may further include a current sampling module 70 for collecting the charging current. The current sampling module 70 is connected to the charging output terminal 30 and the main control chip 10 (U1).

[0056] By providing a current sampling module 70, the collected charging current can be transmitted to the main control chip 10 (U1). The main control chip 10 (U1) adjusts the control of the buck switch 41 and the boost unit 44 based on the charging current to achieve charging current regulation. The main control chip 10 (U1) can use existing chips to implement the control and adjustment of the buck switch 41 and the boost unit 44 based on the collected charging current. The software portion of this does not constitute an improvement of the present invention.

[0057] Specifically, the current sampling module 70 includes a third sampling resistor R4, a fourth sampling resistor R5, and a filter capacitor C1. One end of the third sampling resistor R4 is grounded, and the other end is connected to the charging output terminal 30 and one end of the fourth sampling resistor R5. The other end of the fourth sampling resistor R5 is connected to one end of the filter capacitor C1 and the main control chip 10 (U1). The other end of the filter capacitor C1 is grounded.

[0058] By setting the third sampling resistor R4, the fourth sampling resistor R5 and the filter capacitor C1, a current sampling circuit is formed to transmit the sampled charging current to the main control chip 10 (U1). Among them, the fourth sampling resistor R5 and the filter capacitor C1 form an RC filter circuit to play a filtering role.

[0059] In the optional embodiment of this application, refer to Figures 2 to 4 The battery charging circuit also includes a fast charging protocol chip 80 (U2), which is connected to the charging input terminal 20 and the main control chip 10 (U1).

[0060] By setting the fast charging protocol chip 80 (U2), the main control chip 10 (U1) can turn on the fast charging protocol chip 80 (U2) to induce the external power supply connected to the charging input terminal 20 to adjust the voltage of the input battery charging circuit to achieve fast charging.

[0061] During specific implementation, the fast charging protocol chip 80 (U2) can use an existing chip, such as the HUB238 chip, to achieve the induction of the input voltage of the charging input terminal 20.

[0062] In the optional embodiment of this application, refer to Figure 3 The buck-boost module 40 also includes a first energy storage capacitor C2 and a second energy storage capacitor C3. The positive electrode of the first energy storage capacitor C2 is connected to the charging input terminal 20 and the first end of the buck switch tube 41, the positive electrode of the second energy storage capacitor C3 is connected to the boost unit 44 and the charging output terminal 30, and the negative electrode of the first energy storage capacitor C2 and the negative electrode of the second energy storage capacitor C3 are both grounded.

[0063] By setting the first energy storage capacitor C2, the input voltage can be smoothed and stabilized; by setting the second energy storage capacitor C3, the output voltage can be smoothed and ensured to be stable, thereby improving the stability and reliability of the input and output of the battery charging circuit.

[0064] Further, refer to Figure 2 and Figure 3 The boost unit 44 includes an NMOS transistor Q7 and a second diode D2. The gate of the NMOS transistor Q7 is connected to the main control chip 10 (U1), the source of the NMOS transistor Q7 is grounded, the drain of the NMOS transistor Q7 is connected to the second end of the energy storage inductor 43 (L1) and the positive electrode of the second diode D2, the negative electrode of the second diode D2 is connected to the charging output terminal 30 and the positive electrode of the second energy storage capacitor C3, and the negative electrode of the second energy storage capacitor C3 is grounded.

[0065] By providing the NMOS transistor Q7 and the second diode D2, and cooperating with the energy storage inductor 43 (L1) to achieve voltage boost, the main control chip 10 (U1) can achieve precise control and regulation of the NMOS transistor Q7. The circuit structure is relatively simple, wherein the second diode D2 can ensure unidirectional current flow.

[0066] When the second energy storage capacitor C3 is provided, the cathode of the second diode D2 is also connected to the anode of the second energy storage capacitor C3.

[0067] Combine Figure 3 and Figure 4 The main working principle of the battery charging circuit of the embodiment of the utility model is as follows:

[0068] When the battery charging circuit is in the boosting process, the main control chip 10 (U1) outputs a PWM signal to control the conduction and cutoff of the NMOS tube Q7 to control the on-off of the current. The energy storage inductor 43 (L1) stores energy and prevents sudden current changes. The second diode D2 ensures unidirectional current flow and superimposes the reverse electromotive force generated when the NMOS tube Q7 is disconnected on the second energy storage capacitor C3 to achieve boosting. The second energy storage capacitor C3 can smooth the output voltage and ensure output stability. When the battery charging circuit is in the step-down operation process, the main control chip 10 (U1) outputs a PWM signal to control the on and off of the first PMOS transistor Q1. When the first PMOS transistor Q1 is turned on, the input voltage of the charging input terminal 20 charges the first energy storage capacitor C2, and at the same time supplies power to the load through the energy storage inductor 43 (L1). At this time, the energy storage inductor 43 (L1) and the second energy storage capacitor C3 store energy; when the first PMOS transistor Q1 is turned off, the energy stored in the energy storage inductor 43 (L1) and the second energy storage capacitor C3 begins to be released, and is freewheeled through the first diode 42 (D1), continuing to supply power to the load, while maintaining the voltage of the second energy storage capacitor C3 stable, so that the output voltage is stable.

[0069] The present invention also provides a camera battery charging device comprising a storage box, a circuit board, and the aforementioned battery charging circuit. The storage box is configured to receive camera batteries, and the battery charging circuit is disposed on the circuit board, which is disposed within the storage box. A charging output terminal 30 of the battery charging circuit outputs a charging voltage to charge the camera battery within the storage box. This camera battery charging device has the same circuit structure and benefits as the battery charging circuit in the aforementioned embodiment. The circuit structure and benefits of the battery charging circuit have been described in detail in the aforementioned embodiment and will not be further elaborated upon here.

[0070] In addition, the camera battery charging device of the embodiment of the present invention integrates the charging and storage functions of the camera battery by setting the above-mentioned battery charging circuit on a circuit board, placing the circuit board in a storage box, and the storage box can be used to store camera batteries, making it convenient to charge and carry the camera battery.

[0071] It should be understood that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Those skilled in the art may modify the technical solutions described in the above embodiments, or make equivalent replacements for some of the technical features therein; and all these modifications and replacements should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A battery charging circuit, characterized in that: It includes a main control chip, a charging input terminal, a charging output terminal and a buck-boost module, among which: The charging input terminal is used to input an external power source; The charging output terminal is used to output a charging voltage to charge the battery; The buck-boost module includes a buck switching tube, a first diode, an energy storage inductor and a boost unit. The driving end of the buck switching tube is connected to the main control chip, the first end of the buck switching tube is connected to the charging input end, the second end of the buck switching tube is connected to the first end of the energy storage inductor and the negative electrode of the first diode, the second end of the energy storage inductor is connected to the boost unit, the positive electrode of the first diode is connected to the ground end, the boost unit is connected to the charging output end and the driving end of the boost unit is connected to the main control chip.

2. The battery charging circuit according to claim 1, wherein: The buck-boost module further includes a buck driving unit, which is arranged between the driving end of the buck switch tube and the main control chip.

3. The battery charging circuit according to claim 2, characterized in that: The step-down switching tube is a first PMOS tube, and the step-down driving unit includes a first triode, a second triode and a third triode. The base of the first triode is connected to the main control chip, and the collector is connected to the base of the second triode and the base of the third triode. The emitter of the first triode and the collector of the third triode are grounded. The collector of the second triode is connected to the charging input end and the source of the first PMOS tube, the emitter of the second triode is connected to the emitter of the third triode and the gate of the first PMOS tube, and the drain of the first PMOS tube is connected to the first end of the energy storage inductor and the negative electrode of the first diode.

4. The battery charging circuit according to claim 1, wherein: The battery charging circuit further includes a voltage sampling module for collecting a charging voltage, and the voltage sampling module is connected to the charging output terminal and the main control chip.

5. The battery charging circuit according to claim 4, characterized in that: The battery charging circuit also includes a voltage sampling control module, which is connected to the main control chip and is arranged between the charging output end and the voltage sampling module. The voltage sampling control module is used to connect or disconnect the path between the charging output end and the voltage sampling module.

6. The battery charging circuit according to claim 5, characterized in that: The voltage sampling control module includes a fourth transistor, a second PMOS transistor and a pull-up resistor. The base of the fourth transistor is connected to the main control chip, the emitter is grounded, the collector is connected to the gate of the second PMOS transistor and one end of the pull-up resistor, the source of the second PMOS transistor is connected to the charging output end and the other end of the pull-up resistor, and the drain is connected to the voltage sampling module.

7. The battery charging circuit according to claim 1, wherein: The battery charging circuit also includes a fast charging protocol chip, which is connected to the charging input terminal and the main control chip.

8. The battery charging circuit according to any one of claims 1 to 7, characterized in that: The buck-boost module also includes a first energy storage capacitor and a second energy storage capacitor, the positive electrode of the first energy storage capacitor is connected to the charging input end and the first end of the buck switch tube, the positive electrode of the second energy storage capacitor is connected to the boost unit and the charging output end, and the negative electrode of the first energy storage capacitor and the negative electrode of the second energy storage capacitor are both grounded.

9. The battery charging circuit according to claim 8, characterized in that: The boost unit includes an NMOS tube and a second diode, the gate of the NMOS tube is connected to the main control chip, the source of the NMOS tube is grounded, the drain of the NMOS tube is connected to the second end of the energy storage inductor and the positive electrode of the second diode, and the negative electrode of the second diode is connected to the charging output end and the positive electrode of the second energy storage capacitor.

10. A camera battery charging device, characterized in that: It comprises a storage box, a circuit board, and a battery charging circuit as described in any one of claims 1 to 9, wherein the storage box is used to store a camera battery, the battery charging circuit is arranged on the circuit board, and the circuit board is arranged in the storage box, and the charging output end of the battery charging circuit outputs a charging voltage to charge the camera battery in the storage box.

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