Overvoltage protection circuit, switching power supply circuit, and charging device

Abstract

The utility model discloses a kind of overvoltage protection circuit, switching power supply circuit and charging device, including input partial pressure circuit output first partial pressure voltage to reference voltage stabilizing circuit;When first partial pressure voltage is greater than first reference voltage, reference voltage stabilizing circuit exports first voltage stabilizing voltage;Second grade partial pressure circuit exports second partial pressure voltage according to first voltage stabilizing voltage;First capacitor circuit inhibits high-frequency noise signal, and the working parameter of first switching circuit and the working parameter of reference voltage stabilizing circuit are temperature compensation;First switching circuit according to second partial pressure voltage, first chip and first reference ground are turned on, to indicate first chip to carry out overvoltage protection, inhibit high-frequency noise signal by first capacitor circuit and carry out temperature compensation, and utilize first switching circuit in when first partial pressure voltage is greater than first reference voltage, first chip and first reference ground are turned on, to indicate first chip to carry out overvoltage protection, improve the response speed and reliability of overvoltage protection.

Description

Technical Field

[0001] This utility model relates to the field of overvoltage protection technology, and in particular to an overvoltage protection circuit, a switching power supply circuit, and a charging device. Background Technology

[0002] Switching power supplies, due to their advantages such as high efficiency, small size, and light weight, are widely used in various electronic devices as core power supply modules. Traditional switching power supplies typically include input filtering, power conversion, output rectification and filtering, and basic control and protection circuits.

[0003] While some switching power supply solutions with overvoltage, overcurrent, or overheat protection exist in the existing technology, these protection functions often suffer from problems such as insufficiently optimized design of detection points and feedback paths, resulting in delayed or malfunctioning protection responses, poor dynamic performance, or complex circuit structures with a large number of components, which are not conducive to cost control and miniaturization design. Utility Model Content

[0004] This utility model provides an overvoltage protection circuit, a switching power supply circuit, and a charging device to solve the problems of slow response and poor reliability of existing overvoltage protection circuits.

[0005] An overvoltage protection circuit includes an input voltage divider circuit, a reference voltage regulator circuit, a two-stage voltage divider circuit, a first switching circuit, and a first capacitor circuit. The input voltage divider circuit is connected to the voltage input terminal, the reference voltage regulator circuit, and the first reference ground, and is used to output a first voltage divider voltage to the reference voltage regulator circuit according to the input voltage input at the voltage input terminal. The reference voltage regulator circuit is connected to the two-stage voltage divider circuit to provide a first reference voltage. When the first voltage divider voltage is greater than the first reference voltage, a first regulated voltage is output to the two-stage voltage divider circuit. The two-stage voltage divider circuit is connected to the first switching circuit and is used to output a second voltage divider to the first switching circuit according to the first regulated voltage. The first capacitor circuit is connected to the first switching circuit, the reference voltage regulator circuit, and the first reference ground, and is used to suppress high-frequency noise signals and to perform temperature compensation on the operating parameters of the first switching circuit and the operating parameters of the reference voltage regulator circuit. The first switching circuit is used to connect the first chip and is connected to the first reference ground. It is used to turn on the first chip and the first reference ground according to the second voltage divider voltage to instruct the first chip to perform overvoltage protection.

[0006] Furthermore, the input voltage divider circuit includes a first resistor circuit and a second resistor circuit; The first terminal of the first resistor circuit is connected to the voltage input terminal, the second terminal of the first resistor circuit is connected to the first terminal of the second resistor circuit, the second terminal of the second resistor circuit is connected to the first reference ground, and the connection node between the first resistor circuit and the second resistor circuit is connected to the reference voltage regulator circuit.

[0007] Furthermore, the first resistor circuit includes at least two first resistors; the at least two first resistors are connected in series. The second resistor circuit includes at least two second resistors, which are connected in parallel.

[0008] Furthermore, the reference voltage regulator circuit includes a Zener diode, and the first reference voltage is the breakdown voltage of the Zener diode.

[0009] Furthermore, the two-stage voltage divider circuit includes a third resistor and a fourth resistor; The first end of the third resistor is connected to the reference voltage regulator circuit, the second end of the third resistor is connected to the first end of the fourth resistor, and the first end of the fourth resistor is connected to the first reference ground. The connection node between the third resistor and the fourth resistor is connected to the first switching circuit.

[0010] Furthermore, the first switching circuit includes a first transistor; The collector of the first transistor is connected to the first chip, the emitter of the first transistor is connected to the first reference ground, and the base of the first transistor is connected to the two-stage voltage divider circuit.

[0011] Furthermore, the overvoltage protection circuit also includes a current-limiting resistor; the collector of the first transistor is connected to the first end of the current-limiting resistor, and the second end of the current-limiting resistor is connected to the first chip.

[0012] Furthermore, the first capacitor circuit includes a first capacitor and a second capacitor. The first terminal of the first capacitor is connected to the first switching circuit, and the second terminal of the first capacitor is connected to the first reference ground. The first terminal of the second capacitor is connected to the reference voltage regulator circuit, and the second terminal of the second capacitor is connected to the first reference ground.

[0013] A switching power supply circuit includes a first chip and the overvoltage protection circuit described above; the first chip is connected to the overvoltage protection circuit.

[0014] A charging device includes the aforementioned switching power supply circuit.

[0015] This utility model provides an overvoltage protection circuit, a switching power supply circuit, and a charging device. The overvoltage protection circuit includes an input voltage divider circuit, a reference voltage regulator circuit, a two-stage voltage divider circuit, a first switching circuit, and a first capacitor circuit. The input voltage divider circuit is connected to a voltage input terminal, the reference voltage regulator circuit, and a first reference ground, and is used to output a first divided voltage to the reference voltage regulator circuit based on the input voltage input to the voltage input terminal. The reference voltage regulator circuit is connected to the two-stage voltage divider circuit and is used to provide a first reference voltage. When the first divided voltage is greater than the first reference voltage, it outputs a first regulated voltage to the two-stage voltage divider circuit. The two-stage voltage divider circuit is connected to the first switching circuit and is used to output a second divided voltage to the first switching circuit based on the first regulated voltage. The circuit includes a first capacitor circuit connected to a first switching circuit, a reference voltage regulator circuit, and a first reference ground. This circuit suppresses high-frequency noise signals and provides temperature compensation for the operating parameters of the first switching circuit and the reference voltage regulator circuit. The first switching circuit connects to the first chip and is also connected to the first reference ground. It is used to turn on the first chip and the first reference ground according to the second voltage divider voltage, indicating that the first chip should perform overvoltage protection. This process suppresses high-frequency noise signals and provides temperature compensation through the first capacitor circuit. Furthermore, when the first voltage divider voltage exceeds the first reference voltage, the first switching circuit turns on the first chip and the first reference ground, indicating that the first chip should perform overvoltage protection, thereby improving the response speed and reliability of the overvoltage protection. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the description of the embodiments of this utility model will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of an overvoltage protection circuit in one embodiment of the present invention.

[0018] In the diagram: 1. Input high-voltage electrolytic capacitor; 2. Transformer; 3. First chip; 4. Overvoltage protection circuit; 41. Input voltage divider circuit; 411. First resistor circuit; 412. Second resistor circuit; 42. Reference voltage regulator circuit; 43. Second-stage voltage divider circuit; 44. First switching circuit; 45. First capacitor circuit. Detailed Implementation

[0019] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present utility model.

[0020] It should be understood that this invention can be embodied in various forms and should not be construed as being limited to the embodiments set forth herein. Rather, providing these embodiments will make the disclosure thorough and complete, and will fully convey the scope of this invention to those skilled in the art.

[0021] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the invention. When used herein, the singular forms “a,” “an,” and “ / the” are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprising” and / or “comprising,” when used in this specification, identify the presence of features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups. When used herein, the term “and / or” includes any and all combinations of the associated listed items.

[0022] To fully understand this utility model, detailed structures and steps will be presented in the following description to illustrate the technical solution proposed by this utility model. Preferred embodiments of this utility model are described in detail below; however, in addition to these detailed descriptions, this utility model may have other embodiments.

[0023] This embodiment provides an overvoltage protection circuit 4, such as Figure 1 As shown, this is applied in a switching power supply circuit. Exemplarily, the overvoltage protection circuit 4 is connected to the voltage input terminal and the first chip 3 in the switching power supply circuit. The voltage input terminal is connected to the input high-voltage electrolytic capacitor 1 of the switching power supply circuit to receive the input voltage. The first chip 3 is used to control the operation of the switching power supply circuit. Exemplarily, when the input voltage is too high, overvoltage protection is executed. For example, the switching power supply circuit is controlled to stop output. It is understood that the specific method by which the first chip 3 controls the operation of the switching power supply circuit is well-known to those skilled in the art and will not be described further here.

[0024] For example, the switching power supply circuit includes an input high-voltage electrolytic capacitor 1, a transformer 2, a first switching transistor, and a load connection terminal. The first terminal of the input high-voltage electrolytic capacitor 1 is connected to the first input terminal of the transformer 2, and the second terminal of the input high-voltage electrolytic capacitor 1 is connected to a first reference ground GND1. The second input terminal of the transformer 2 is connected to the first reference ground GND1 through the first switching transistor. The output terminal of the transformer 2 is connected to the load connection terminal. A first chip 3 is connected to the first switching transistor, and by controlling the alternating conduction of the first switching transistor, the output of the switching power supply is controlled.

[0025] This embodiment provides an overvoltage protection circuit 4, such as Figure 1 As shown, the circuit includes an input voltage divider circuit 41, a reference voltage regulator circuit 42, a second-stage voltage divider circuit 43, a first switching circuit 44, and a first capacitor circuit 45. The input voltage divider circuit 41 is connected to the voltage input terminal, the reference voltage regulator circuit 42, and the first reference ground GND1, and is used to output a first divided voltage to the reference voltage regulator circuit 42 according to the input voltage input to the voltage input terminal. The reference voltage regulator circuit 42 is connected to the second-stage voltage divider circuit 43, and is used to provide a first reference voltage. When the first divided voltage is greater than the first reference voltage, it outputs a first regulated voltage to the second-stage voltage divider circuit 43. The second-stage voltage divider circuit 44 is connected to the first switching circuit 45. The switching circuit 44 is connected to the first switching circuit 44 and is used to output the second divided voltage to the first switching circuit 44 according to the first regulated voltage; the first capacitor circuit 45 is connected to the first switching circuit 44, the reference voltage regulator circuit 42 and the first reference ground GND1, and is used to suppress high-frequency noise signals and perform temperature compensation on the operating parameters of the first switching circuit 44 and the operating parameters of the reference voltage regulator circuit 42; the first switching circuit 44 is used to connect the first chip 3 and is connected to the first reference ground GND1, and is used to turn on the first chip 3 and the first reference ground GND1 according to the second divided voltage to indicate the first chip 3 to perform overvoltage protection.

[0026] As an example, the input voltage divider circuit 41 is connected to the voltage input terminal, the reference voltage regulator circuit 42, and the first reference ground GND1. It outputs a first divided voltage to the reference voltage regulator circuit 42 based on the input voltage received at the voltage input terminal. In this example, the input voltage is obtained through the input voltage divider circuit 41 so that the reference voltage regulator circuit 42 can determine whether the input voltage is overvoltage. Furthermore, it can proportionally reduce a higher input voltage to a lower first divided voltage, allowing the subsequent reference voltage regulator circuit 42 to operate without high voltage, thus enabling the use of low-voltage components and reducing system cost and size.

[0027] As an example, a reference voltage regulator circuit 42 is connected to a two-stage voltage divider circuit 43 to provide a first reference voltage. When the first divided voltage is greater than the first reference voltage, a first regulated voltage is output to the two-stage voltage divider circuit 43. Exemplarily, the first reference voltage is 7.5V. The voltage divider node voltage of the input voltage divider circuit 41 is Vdiv. When the voltage divider node voltage Vdiv of the input voltage divider circuit 41 is less than or equal to 7.5V, the reference voltage regulator circuit 42 does not output the first regulated voltage. When the first divided voltage is greater than the first reference voltage, the first regulated voltage is output to the two-stage voltage divider circuit 43, thus outputting the first regulated voltage only when the first divided voltage is greater than the first reference voltage, reducing the power consumption of the reference voltage regulator circuit 42.

[0028] As an example, the two-stage voltage divider circuit 43 is connected to the first switching circuit 44 and is used to output a second divided voltage to the first switching circuit 44 based on the first regulated voltage. In this embodiment, the two-stage voltage divider circuit 43 performs a second voltage division on the first regulated voltage to generate the second divided voltage required to drive the first switching circuit 44, thus achieving level conversion and impedance matching.

[0029] As an example, the first capacitor circuit 45 is connected to the first switching circuit 44, the reference voltage regulator circuit 42, and the first reference ground GND1. It is used to suppress high-frequency noise signals and to perform temperature compensation on the operating parameters of the first switching circuit 44 and the reference voltage regulator circuit 42. In this example, by suppressing high-frequency interference through the first capacitor circuit 45, the impact of temperature drift of the parameters of the first switching circuit 44 and the reference voltage regulator circuit 42 on the stability of the overvoltage protection circuit 4 is reduced. This indirectly achieves temperature compensation on the operating parameters of the overvoltage protection circuit 4, improving the reliability of the overvoltage protection circuit 4 in complex environments.

[0030] As an example, the first switching circuit 44 is used to connect the protection pin COMP of the first chip 3 and is connected to the first reference ground GND1. It is used to turn on the first chip 3 and the first reference ground GND1 according to the second voltage divider voltage, to instruct the first chip 3 to perform overvoltage protection. Exemplarily, when the first voltage divider voltage is less than or equal to the first reference voltage, the reference voltage regulator circuit 42 does not output the first regulated voltage. The first switching circuit 44 is not turned on, the protection pin COMP of the first chip 3 is at a high level, and the switching power supply circuit operates normally. When the first voltage divider voltage is greater than the first reference voltage, the reference voltage regulator circuit 42 outputs the first regulated voltage to the second-stage voltage divider circuit 43, the second-stage voltage divider circuit 43 outputs the second voltage divider voltage to the first switching circuit 44, the first switching circuit 44 is turned on, pulling the protection pin COMP of the first chip 3 to a low level, triggering the overvoltage protection action of the first chip 3, and controlling the switching power supply circuit to stop outputting.

[0031] In this embodiment, the overvoltage protection circuit 4 includes an input voltage divider circuit 41, a reference voltage regulator circuit 42, a second-stage voltage divider circuit 43, a first switching circuit 44, and a first capacitor circuit 45. The input voltage divider circuit 41 is connected to the voltage input terminal, the reference voltage regulator circuit 42, and the first reference ground GND1, and is used to output a first divided voltage to the reference voltage regulator circuit 42 according to the input voltage input to the voltage input terminal. The reference voltage regulator circuit 42 is connected to the second-stage voltage divider circuit 43, and is used to provide a first reference voltage. When the first divided voltage is greater than the first reference voltage, it outputs a first regulated voltage to the second-stage voltage divider circuit 43. The second-stage voltage divider circuit 43 is connected to the first switching circuit 44, and is used to output a second divided voltage to the first switching circuit 44 according to the first regulated voltage. The first capacitor circuit 45 is connected to the first... A switching circuit 44, a reference voltage regulator circuit 42, and a first reference ground GND1 are connected to suppress high-frequency noise signals and to perform temperature compensation on the operating parameters of the first switching circuit 44 and the reference voltage regulator circuit 42. The first switching circuit 44 is connected to the first chip 3 and the first reference ground GND1. It is used to turn on the first chip 3 and the first reference ground GND1 according to the second voltage divider voltage to instruct the first chip 3 to perform overvoltage protection. This suppresses high-frequency noise signals and performs temperature compensation through the first capacitor circuit 45. The first switching circuit 44 turns on the first chip 3 and the first reference ground GND1 when the first voltage divider voltage is greater than the first reference voltage to instruct the first chip 3 to perform overvoltage protection, thereby improving the response speed and reliability of overvoltage protection.

[0032] In one embodiment, the input voltage divider circuit 41 includes a first resistor circuit 411 and a second resistor circuit 412; the first terminal of the first resistor circuit 411 is connected to the voltage input terminal, the second terminal of the first resistor circuit 411 is connected to the first terminal of the second resistor circuit 412, the second terminal of the second resistor circuit 412 is connected to the first reference ground GND1, and the connection node between the first resistor circuit 411 and the second resistor circuit 412 is connected to the reference voltage regulator circuit 42.

[0033] In this embodiment, by setting and adjusting the resistance ratio of the first resistor circuit 411 and the second resistor circuit 412, the overvoltage protection point of the overvoltage protection circuit 4 can be flexibly set, increasing the versatility and adjustability of the overvoltage protection circuit 4.

[0034] In one embodiment, the first resistor circuit 411 includes at least two first resistors connected in series; the second resistor circuit 412 includes at least two second resistors connected in parallel. Figure 1 As shown, at least two first resistors include resistor R11 and resistor R22. At least two second resistors include resistor R21 and resistor R22.

[0035] In this embodiment, by connecting at least two first resistors in series and at least two second resistors in parallel, the accuracy of the voltage divider network can be increased, the overvoltage detection threshold can be avoided, and the total resistance error can be reduced to <±2%.

[0036] In one embodiment, the reference voltage regulator circuit 42 includes a Zener diode ZD1, and the first reference voltage is the breakdown voltage of the Zener diode ZD1. In this embodiment, the cathode of the Zener diode ZD1 is connected to the voltage divider node of the input voltage divider circuit 41, and the anode is used as the output. Therefore, the Zener diode ZD1 will only conduct in reverse when the voltage of the voltage divider node of the input voltage divider circuit 41 exceeds its breakdown voltage, thereby providing a very stable and accurate first reference voltage for the subsequent circuits, which in turn determines the threshold for protection action. This results in high accuracy and good stability. Furthermore, it ensures that the overvoltage protection circuit 4 consumes very little power under normal voltage, only operating under overvoltage conditions, making it energy-saving and safe.

[0037] In one embodiment, the two-stage voltage divider circuit 43 includes a third resistor R31 and a fourth resistor R41; the first end of the third resistor R31 is connected to the reference voltage regulator circuit 42, the second end of the third resistor R31 is connected to the first end of the fourth resistor R41, and the first end of the fourth resistor R41 is connected to the first reference ground GND1; the connection node between the third resistor R31 and the fourth resistor R41 is connected to the first switching circuit 44.

[0038] In this embodiment, by selecting the resistance values ​​of the third resistor R31 and the fourth resistor R41, the voltage and current of the control drive first switch circuit 44 can be flexibly adjusted to ensure its reliable conduction and cutoff, avoiding problems caused by insufficient or excessive drive, and improving the reliability of the overvoltage protection circuit 4.

[0039] In one embodiment, the first switching circuit 44 includes a first transistor Q1; the collector of the first transistor Q1 is connected to the first chip 3, the emitter of the first transistor Q1 is connected to the first reference ground GND1, and the base of the first transistor Q1 is connected to the two-stage voltage divider circuit 43.

[0040] As an example, the first transistor Q1 is an NPN transistor. In this example, the emitter of the first transistor Q1 is directly grounded, forming a common-emitter switching circuit. This circuit has good switching characteristics, fast response speed, and can quickly transmit signals to the first chip 3, thus improving the overvoltage response speed.

[0041] In one embodiment, the overvoltage protection circuit 4 further includes a current-limiting resistor R51; the collector of the first transistor Q1 is connected to the first end of the current-limiting resistor R51, and the second end of the current-limiting resistor R51 is connected to the first chip 3.

[0042] In this embodiment, by connecting a current-limiting resistor R51 in series with the collector of the first transistor Q1, the current flowing into the protection pin COMP of the first chip 3 can be effectively limited, preventing damage to the first chip 3 or the first transistor Q1 due to excessive current when the first transistor Q1 is turned on, thereby enhancing the safety of the overvoltage protection circuit 4.

[0043] In one embodiment, the first capacitor circuit 45 includes a first capacitor C1 and a second capacitor C2; the first terminal of the first capacitor C1 is connected to the first switching circuit 44, and the second terminal of the first capacitor C1 is connected to the first reference ground GND1; the first terminal of the second capacitor C2 is connected to the reference voltage regulator circuit 42, and the second terminal of the second capacitor C2 is connected to the first reference ground GND1.

[0044] In this embodiment, the first capacitor C1 is connected between the base of the first transistor Q1 and the first reference ground GND1, which can efficiently filter out high-frequency noise signals that may be coupled to the base of the first transistor Q1 through lines or space, greatly enhancing the anti-interference capability of the first switching circuit 44 and effectively preventing false triggering caused by noise. By connecting the second capacitor C2 between the input terminal of the reference voltage regulator circuit 42 and the first reference ground GND1, a high-frequency bypass is provided for the Zener diode ZD1 in the reference voltage regulator circuit 42, further stabilizing its operating point and suppressing the influence of ripple and noise in the input voltage on the reference voltage.

[0045] Furthermore, the first capacitor C1 and the third resistor R31 in the second-stage voltage divider circuit 43 form an RC filter network to prevent the first transistor Q1 from being falsely triggered, while maintaining the response speed.

[0046] This embodiment provides a switching power supply circuit, including a first chip 3 and the overvoltage protection circuit 4 described above; the first chip 3 is connected to the overvoltage protection circuit 4.

[0047] This embodiment provides a charging device, including the switching power supply circuit described above.

[0048] The above embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Although this utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this utility model, and should all be included within the protection scope of this utility model.

Claims

1. An overvoltage protection circuit, characterized in that, It includes an input voltage divider circuit, a reference voltage regulator circuit, a two-stage voltage divider circuit, a first switching circuit, and a first capacitor circuit; The input voltage divider circuit is connected to the voltage input terminal, the reference voltage regulator circuit, and the first reference ground, and is used to output a first voltage divider voltage to the reference voltage regulator circuit according to the input voltage input at the voltage input terminal. The reference voltage regulator circuit is connected to the two-stage voltage divider circuit to provide a first reference voltage. When the first voltage divider voltage is greater than the first reference voltage, a first regulated voltage is output to the two-stage voltage divider circuit. The two-stage voltage divider circuit is connected to the first switching circuit and is used to output a second voltage divider to the first switching circuit according to the first regulated voltage. The first capacitor circuit is connected to the first switching circuit, the reference voltage regulator circuit, and the first reference ground, and is used to suppress high-frequency noise signals and to perform temperature compensation on the operating parameters of the first switching circuit and the operating parameters of the reference voltage regulator circuit. The first switching circuit is used to connect the first chip and is connected to the first reference ground. It is used to turn on the first chip and the first reference ground according to the second voltage divider voltage to instruct the first chip to perform overvoltage protection.

2. The overvoltage protection circuit according to claim 1, characterized in that, The input voltage divider circuit includes a first resistor circuit and a second resistor circuit; The first terminal of the first resistor circuit is connected to the voltage input terminal, the second terminal of the first resistor circuit is connected to the first terminal of the second resistor circuit, the second terminal of the second resistor circuit is connected to the first reference ground, and the connection node between the first resistor circuit and the second resistor circuit is connected to the reference voltage regulator circuit.

3. The overvoltage protection circuit according to claim 2, characterized in that, The first resistor circuit includes at least two first resistors; the at least two first resistors are connected in series. The second resistor circuit includes at least two second resistors, which are connected in parallel.

4. The overvoltage protection circuit according to claim 1, characterized in that, The reference voltage regulator circuit includes a Zener diode, and the first reference voltage is the breakdown voltage of the Zener diode.

5. The overvoltage protection circuit according to claim 1, characterized in that, The two-stage voltage divider circuit includes a third resistor and a fourth resistor; The first end of the third resistor is connected to the reference voltage regulator circuit, the second end of the third resistor is connected to the first end of the fourth resistor, and the first end of the fourth resistor is connected to the first reference ground. The connection node between the third resistor and the fourth resistor is connected to the first switching circuit.

6. The overvoltage protection circuit according to claim 1, characterized in that, The first switching circuit includes a first transistor; The collector of the first transistor is connected to the first chip, the emitter of the first transistor is connected to the first reference ground, and the base of the first transistor is connected to the two-stage voltage divider circuit.

7. The overvoltage protection circuit according to claim 6, characterized in that, The overvoltage protection circuit also includes a current-limiting resistor; the collector of the first transistor is connected to the first end of the current-limiting resistor, and the second end of the current-limiting resistor is connected to the first chip.

8. The overvoltage protection circuit according to claim 1, characterized in that, The first capacitor circuit includes a first capacitor and a second capacitor; The first terminal of the first capacitor is connected to the first switching circuit, and the second terminal of the first capacitor is connected to the first reference ground. The first terminal of the second capacitor is connected to the reference voltage regulator circuit, and the second terminal of the second capacitor is connected to the first reference ground.

9. A switching power supply circuit, characterized in that, It includes a first chip and an overvoltage protection circuit as described in any one of claims 1 to 8; the first chip is connected to the overvoltage protection circuit.

10. A charging device, characterized in that, Includes the switching power supply circuit as described in claim 9.

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