Contact protection circuit and electronic equipment

Abstract

The invention provides a contact protection circuit and electronic equipment. The contact protection circuit comprises an accessory detection circuit, a clamping circuit and a switch switching circuit, the input end of the signal identification circuit is connected with a contact circuit of the electronic equipment, and the signal identification circuit is used for detecting whether an accessory is accessed or not; the input end of the clamping circuit is connected with the output end of the accessory detection circuit; the controlled end of the switch switching circuit is connected with the output end of the clamping circuit, the input end of the switch switching circuit is connected with the contact circuit, and the output end of the switch switching circuit is connected with a control circuit of the electronic equipment. According to the invention, the accessory and the control circuit can be connected after the accessory is stably connected, repeated disconnection is avoided, and the stability is improved.

Description

Technical Field

[0001] This invention relates to the field of wireless communication technology, specifically to a contact protection circuit and electronic device. Background Technology

[0002] Currently, most peripheral interfaces of electronic devices (such as radios, communication terminals, and other electronic devices with accessory interfaces) use metal contact points to connect accessories. During accessory connection, due to the structural characteristics of the metal contacts and human operation factors, the contacts are prone to frequent connection and disconnection, leading to voltage overshoot on the signal lines. In severe cases, this can cause abnormal device operation or even hardware damage. Summary of the Invention

[0003] This invention provides a contact protection circuit and electronic device, which aims to solve the problem of unstable signal voltage caused by repeated disconnections during the contact connection process of current handheld communication devices.

[0004] In a first aspect, the present invention provides a contact protection circuit, which includes an accessory detection circuit, a clamping circuit, and a switch switching circuit; the input terminal of the signal recognition circuit is connected to the contact circuit of the electronic device for detecting whether an accessory is connected; the input terminal of the clamping circuit is connected to the output terminal of the accessory detection circuit; the controlled terminal of the switch switching circuit is connected to the output terminal of the clamping circuit, the input terminal of the switch switching circuit is connected to the contact circuit, and the output terminal of the switch switching circuit is connected to the control circuit of the electronic device.

[0005] Furthermore, the accessory detection circuit includes at least one diode, the negative terminal of which is connected to the contact circuit, and the positive terminal of which is connected to the input terminal of the clamping circuit.

[0006] Furthermore, the accessory detection circuit includes three diodes, namely a first diode, a second diode, and a third diode; the negative terminals of the first diode, the second diode, and the third diode are all connected to the contact circuit, and the positive terminals of the first diode, the second diode, and the third diode are all connected to the input terminal of the clamping circuit.

[0007] Furthermore, the accessory detection circuit also includes a first resistor, a second resistor, a third resistor, a fourth resistor, and a first capacitor; the first resistor is connected in parallel with the negative terminal of the first diode, the second resistor is connected in parallel with the negative terminal of the second diode, the third resistor is connected in parallel with the negative terminal of the third diode, one end of the first capacitor is connected to the positive terminal of the first diode, the positive terminal of the second diode, and the positive terminal of the third diode, and the other end of the first capacitor is grounded.

[0008] Furthermore, the clamping circuit includes a first switching element and a reset chip; the controlled terminal of the first switching element is connected to the output terminal of the accessory detection circuit, the first terminal of the first switching element is connected to the reset chip, the second terminal of the first switching element is grounded, and the reset chip is connected to the switch switching circuit.

[0009] Furthermore, the clamping circuit also includes a fifth resistor, a sixth resistor, and a seventh resistor; one end of the fifth resistor is connected to the accessory detection circuit, the other end of the fifth resistor is connected to the controlled electrode of the first switching element, one end of the sixth resistor is connected to the power supply terminal, the other end of the sixth resistor is connected to the reset chip, one end of the seventh resistor is connected to the power supply terminal, and the other end of the seventh resistor is connected to the switch switching circuit.

[0010] Furthermore, the clamping circuit also includes a second capacitor and a third capacitor; one end of the second capacitor and one end of the third capacitor are both connected to the reset chip, and the other ends of the second capacitor and the third capacitor are both grounded.

[0011] Furthermore, the switch switching circuit includes a switching chip, which is connected to the clamping circuit, the control circuit, and the contact circuit respectively.

[0012] Furthermore, the switching circuit also includes an eighth resistor and a ninth resistor; one end of the eighth resistor and one end of the ninth resistor are both connected to the clamping circuit, the other end of the eighth resistor is grounded, and the other end of the ninth resistor is connected to the switching chip.

[0013] In a second aspect, the present invention also provides an electronic device, which includes a control circuit, a contact circuit, and a contact protection circuit as described in any of the preceding claims.

[0014] The electronic device disclosed in this invention includes a control circuit, a contact circuit, and a contact protection circuit. The contact protection circuit includes an accessory detection circuit, a clamping circuit, and a switch switching circuit. The accessory detection circuit is connected to the contact circuit and can detect whether the contact circuit is connected to an accessory. The accessory detection circuit is also connected to the clamping circuit. When the accessory detection circuit detects that the accessory is connected to the contact circuit, it outputs a detection signal to the clamping circuit. After continuously receiving the detection signal for a certain period of time, the clamping circuit outputs a switch signal to the switch switching circuit. The switch switching circuit is connected to both the contact circuit and the control circuit, and conducts upon receiving the switch signal, allowing the accessory to connect to the control circuit through the switch detection circuit. This ensures that the accessory is stably connected before connecting to the control circuit, avoiding repeated disconnections and improving stability. Attached Figure Description

[0015] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a block diagram of a contact protection circuit provided in an embodiment of the present invention; Figure 2 This is a circuit diagram of an accessory detection circuit provided in an embodiment of the present invention; Figure 3 This is a circuit diagram of a clamping circuit provided in an embodiment of the present invention; Figure 4 This is a circuit diagram of a switch switching circuit provided in an embodiment of the present invention. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] It should be understood that, when used in this specification and the appended claims, the terms “comprising” and “including” indicate the presence of the described features, integrals, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, operations, elements, components and / or collections thereof.

[0019] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used in this specification and the appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes such combinations.

[0020] Furthermore, the directional terms used in this invention, such as "up," "down," "front," "back," "left," "right," "inner," "outer," and "side," are merely for reference to the accompanying drawings and the product's usage state. Therefore, the directional terms used are for illustrating and understanding this invention, and not for limiting it. Additionally, in the accompanying drawings, structures that are similar or identical are indicated by the same reference numerals.

[0021] See Figures 1 to 4 , Figure 1 This is a block diagram of a contact protection circuit 100 provided in an embodiment of the present invention; Figure 2 This is a circuit diagram of the accessory detection circuit 10 provided in an embodiment of the present invention; Figure 3 This is a circuit diagram of a clamping circuit 20 provided in an embodiment of the present invention; Figure 4 This is a circuit diagram of a switch switching circuit 30 provided in an embodiment of the present invention. As shown in the figure, the contact protection circuit 100 includes an accessory detection circuit 10, a clamping circuit 20, and a switch switching circuit 30; the input terminal of the signal recognition circuit is connected to the contact circuit 200 of the electronic device, and is used to detect whether an accessory is connected; the input terminal of the clamping circuit 20 is connected to the output terminal of the accessory detection circuit 10; the controlled terminal of the switch switching circuit 30 is connected to the output terminal of the clamping circuit 20, the input terminal of the switch switching circuit 30 is connected to the contact circuit 200, and the output terminal of the switch switching circuit 30 is connected to the control circuit 300 of the electronic device.

[0022] Specifically, the electronic device can be a radio-like device, a communication terminal, or other electronic device with an accessory interface, such as a handheld radio, a vehicle-mounted radio, or a law enforcement recorder. This electronic device may include a control circuit 300, a contact circuit 200, and a contact protection circuit 100. The control circuit 300 is connected to the contact circuit 200 through the contact protection circuit 100. The contact circuit 200 is used to connect to the accessory. When the accessory is connected, the contact protection circuit 100 can detect it, and only after the connection is stable will it connect the control circuit 300 and the contact circuit 200 to prevent unstable connections.

[0023] The contact protection circuit 100 may include an accessory detection circuit 10, a clamping circuit 20, and a switch switching circuit 30. The accessory detection circuit 10 is connected to the contact circuit 200 and is used to detect whether an accessory is connected. For example, it can be confirmed whether the accessory is connected by detecting whether the ground pin of the accessory is connected to the contact. When the ground pin of the accessory is connected to the contact, it can be confirmed that the accessory is connected. At the same time, the accessory detection circuit 10 is also connected to the clamping circuit 20. When the accessory is connected, the accessory detection circuit 10 outputs a first level signal; when the accessory is not connected, the accessory detection circuit 10 outputs a second level signal.

[0024] The clamping circuit 20 is connected to the accessory detection circuit 10 to ensure that the signal path is turned on only after the accessory is stably connected. For example, when no accessory is connected, the accessory detection circuit 10 outputs a second-level signal and the clamping circuit 20 outputs a low-level signal. When the accessory is stably connected, the accessory detection circuit 10 outputs a first-level signal and the clamping circuit 20 outputs a high-level signal, triggering the switch switching circuit 30 to operate.

[0025] The controlled terminal of the switch switching circuit 30 is connected to the output terminal of the clamping circuit 20, its input terminal is connected to the contact circuit 200, and its output terminal is connected to the control circuit 300 of the handheld communication device. It is used to control the connection and disconnection between the contact circuit 200 and the control circuit 300 based on the output signal of the clamping circuit 20. When no accessory is connected or the accessory is not stably connected, the clamping circuit 20 outputs a low level, the switch switching circuit 30 is open, and the connection between the contact circuit 200 and the control circuit 300 is broken. When the accessory is stably connected, the clamping circuit 20 outputs a high level, the switch switching circuit 30 is turned on, and a signal path is established between the contact circuit 200 and the control circuit 300.

[0026] As a further embodiment, the accessory detection circuit 10 includes at least one diode, the negative terminal of which is connected to the contact circuit 200, and the positive terminal of which is connected to the input terminal of the clamping circuit 20.

[0027] Specifically, the negative terminal of the diode is connected to the accessory identification pin in the handheld radio contact circuit 200 to detect whether the ground pin of the accessory is connected to the contact circuit 200, and the positive terminal is connected to the signal input terminal of the clamping circuit 20. When the accessory is not connected, the identification pin of the contact circuit 200 is at a high level, the diode is cut off, and the accessory detection circuit 10 outputs a second level signal (high level) to the clamping circuit 20. When the accessory is connected and the ground pin of the accessory is connected to the contact circuit 200, the accessory identification pin is pulled low by the accessory, the diode is turned on, and a first level signal (low level) is output, realizing the rapid detection of the accessory connection status.

[0028] As a further embodiment, the accessory detection circuit 10 includes three diodes, namely a first diode D1, a second diode D2, and a third diode D3; the negative terminals of the first diode D1, the second diode D2, and the third diode D3 are all connected to the contact circuit 200, and the positive terminals of the first diode D1, the second diode D2, and the third diode D3 are all connected to the input terminal of the clamping circuit 20.

[0029] The accessory detection circuit 10 may include multiple diodes, with different diodes corresponding to different types of accessory pins. For example, it may include three diodes, each corresponding to one of the three types of accessory pins in the handheld radio contact circuit 200. For instance, the cathode of the first diode D1 is connected to the charging accessory identification pin, which detects whether the ground pin of a charging accessory is connected; the cathode of the second diode D2 is connected to the audio accessory identification pin, which detects whether the ground pin of an audio accessory is connected; and the cathode of the third diode D3 is connected to the data accessory identification pin, which detects whether the ground pin of a data accessory is connected. The three diodes use a common positive terminal design. Whenever any accessory is connected and pulls down the corresponding pin level, the common positive terminal of the three diodes will output a first-level signal, enabling detection of all types of charging, audio, and data accessories, thus improving circuit compatibility.

[0030] As a further embodiment, the accessory detection circuit 10 further includes a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, and a first capacitor C1; the first resistor R1 is connected in parallel with the negative terminal of the first diode D1, the second resistor R2 is connected in parallel with the negative terminal of the second diode D2, the third resistor R3 is connected in parallel with the negative terminal of the third diode D3, one end of the first capacitor C1 is connected to the positive terminal of the first diode D1, the positive terminal of the second diode D2, and the positive terminal of the third diode D3, and the other end of the first capacitor C1 is grounded.

[0031] Among them, the first to third resistors R3 are all pull-up resistors, which stabilize the corresponding diode cathode at a high level when no accessories are connected, avoiding false triggering of the floating pin. The fourth resistor R4 is a pull-up resistor, which ensures that the accessory detection circuit 10 outputs a stable high level when no accessories are connected; the first capacitor C1 is a filter capacitor, used to filter out high-frequency noise in the detection signal, ensuring that the level signal output to the clamping circuit 20 is stable.

[0032] As a further embodiment, the clamping circuit 20 includes a first switching element Q1 and a reset chip U1; the controlled terminal of the first switching element Q1 is connected to the output terminal of the accessory detection circuit 10, the first terminal of the first switching element Q1 is connected to the reset chip U1, the second terminal of the first switching element Q1 is grounded, and the reset chip U1 is connected to the switch switching circuit 30.

[0033] In this circuit, the first switching element Q1 can be an NMOS transistor, whose controlled terminal (gate), first terminal (drain), and second terminal (source) are respectively connected to the output terminal of the accessory detection circuit 10, the SENSE pin of the reset chip U1, and ground. When the accessory detection circuit 10 outputs a second-level signal (high level), the gate of the NMOS transistor is energized and turned on, and the SENSE pin of the reset chip U1 is pulled low; when the first-level signal (low level) is output, the NMOS transistor is turned off, and the SENSE pin of the reset chip U1 returns to a high level, thus realizing the state switching of the reset chip U1.

[0034] As a further embodiment, the clamping circuit 20 further includes a fifth resistor R5, a sixth resistor R6, and a seventh resistor R7; one end of the fifth resistor R5 is connected to the accessory detection circuit 10, and the other end of the fifth resistor R5 is connected to the controlled electrode of the first switching element Q1; one end of the sixth resistor R6 is connected to the power supply terminal, and the other end of the sixth resistor R6 is connected to the reset chip U1; one end of the seventh resistor R7 is connected to the power supply terminal, and the other end of the seventh resistor R7 is connected to the switch switching circuit 30.

[0035] Among them, the fifth resistor R5 is a gate current limiting resistor to prevent excessive current from damaging the gate of the NMOS transistor; the sixth resistor R6 is a pull-up resistor, one end of which is connected to the 3.3V power supply terminal of the handheld radio to provide a high-level reference for the U1SENSE pin of the reset chip; the seventh resistor R7 is a current limiting resistor to limit the output current from the power supply terminal to the switch switching circuit 30 to avoid overcurrent damage to the controlled terminal.

[0036] As a further embodiment, the clamping circuit 20 further includes a second capacitor C2 and a third capacitor C3; one end of the second capacitor C2 and one end of the third capacitor C3 are both connected to the reset chip U1, and the other ends of the second capacitor C2 and the third capacitor C3 are both grounded.

[0037] The second capacitor C2 can be a surface-mount ceramic capacitor, connected in parallel between the VDD pin of the reset chip U1 and ground, to filter out the ripple of the 3.3V power supply and ensure the stable operation of the reset chip U1; the third capacitor C3 is connected between the Ct pin of the reset chip U1 and ground, and the delay trigger time is set to a preset time, such as 1.23s, based on the chip characteristics, to ensure that the reset chip U1 only outputs a high level after the accessory is stably connected for 1.23s, thus filtering out interference from the temporary disconnection of the contacts.

[0038] As a further embodiment, the switch switching circuit 30 includes a switching chip U2, which is connected to the clamping circuit 20, the control circuit 300 and the contact circuit 200 respectively.

[0039] In this embodiment, the HSD2+ and HSD2+- pins of the switching chip U2 are connected to the USB_D+ and USB_D- signal terminals (input terminals) of the handheld radio contact circuit 200, and the S pin is connected to the output terminal (controlled terminal) of the clamping circuit 20. When the clamping circuit 20 outputs a low level, the switching chip U2 is open; when it outputs a high level, the switching chip U2 is turned on, thereby realizing the switching of the signal path between the contact circuit 200 and the control circuit 300.

[0040] As a further embodiment, the switch switching circuit 30 further includes an eighth resistor R8 and a ninth resistor R9; one end of the eighth resistor R8 and one end of the ninth resistor R9 are both connected to the clamping circuit 20, the other end of the eighth resistor R8 is grounded, and the other end of the ninth resistor R9 is connected to the switching chip U2.

[0041] Among them, the eighth resistor R8 is a pull-down resistor. When the high-level output of the no-clamp circuit 20 is achieved, it stabilizes the U2S pin of the switching chip at a low level to prevent false turn-on. The ninth resistor R9 is a current-limiting resistor, which limits the current flowing into the U2S pin of the switching chip and protects the controlled end of the chip.

[0042] The following describes the operating status of electronic devices. No attachment access status When no accessories are connected to the contact circuit 200, the negative terminals of the first diode D1 to the third diode D3 are all at a high level, the diodes are cut off, and the output terminal of the accessory detection circuit 10 is at a high level. This high level is input to the controlled terminal of the first switching element Q1 through the fifth resistor R5, the first switching element Q1 is turned on, the SENSE pin of the reset chip U1 is pulled low, and the reset chip U1 outputs a low level. Because the S pin of the switching circuit 30 is at a low level, the switching chip U2 remains open, disconnecting the contact circuit 200 from the control circuit 300.

[0043] Unstable access status for attachments During the insertion and removal of accessories, the contacts repeatedly disconnect, the negative terminal levels of the first diode D1 to the third diode D3 fluctuate frequently, and the output level of the accessory detection circuit 10 is unstable; the on / off state of the first switching element Q1 switches repeatedly, the SENSE pin of the reset chip U1 cannot maintain a high level for the delay time, the reset chip U1 always outputs a low level, and the switching chip U2 remains open to prevent voltage overshoot signals from entering the control circuit 300.

[0044] Attachment stable access status When the accessory ground contact and the identification contact are stably connected, at least one of the negative terminals of the first diode D1 to the third diode D3 is pulled low, the diode is turned on, and the output of the accessory detection circuit 10 is low. When the controlled terminal of the first switching element Q1 is connected to the low level, the first switching element Q1 is turned off, and the SENSE pin of the reset chip U1 is connected to 3V3 through the sixth resistor R6 to become high. When the high level duration reaches the preset time, the reset chip U1 outputs a high level. This high level is input to the S pin of the switching chip U2 through the ninth resistor R9, the switching chip U2 is turned on, and the signal of the contact circuit 200 is transmitted to the control circuit 300 through the switching chip U2 to achieve stable communication.

[0045] The present invention also provides an electronic device, the electronic device including a control circuit 300, a contact circuit 200, and a contact protection circuit 100 as described in any of the above embodiments; the contact protection circuit 100 includes an accessory detection circuit 10, a clamping circuit 20, and a switch switching circuit 30; the input terminal of the signal recognition circuit is connected to the contact circuit 200 of the electronic device, and is used to detect whether an accessory is connected; the input terminal of the clamping circuit 20 is connected to the output terminal of the accessory detection circuit 10; the controlled terminal of the switch switching circuit 30 is connected to the output terminal of the clamping circuit 20, the input terminal of the switch switching circuit 30 is connected to the contact circuit 200, and the output terminal of the switch switching circuit 30 is connected to the control circuit 300 of the electronic device.

[0046] Specifically, the electronic device can be a handheld radio, which may include a control circuit 300, a contact circuit 200, and a contact protection circuit 100. The control circuit 300 is connected to the contact circuit 200 through the contact protection circuit 100. The contact circuit 200 is used to connect to an accessory. When the accessory is connected, the contact protection circuit 100 can detect it, and after the connection is stable, it will then connect the control circuit 300 and the contact circuit 200 to avoid unstable connection.

[0047] The contact protection circuit 100 may include an accessory detection circuit 10, a clamping circuit 20, and a switch switching circuit 30. The accessory detection circuit 10 is connected to the contact circuit 200 and is used to detect whether an accessory is connected. At the same time, the accessory detection circuit 10 is also connected to the clamping circuit 20. When the accessory is connected, the accessory detection circuit 10 outputs a first level signal. When the accessory is not connected, the accessory detection circuit 10 outputs a second level signal.

[0048] The clamping circuit 20 is connected to the accessory detection circuit 10 to ensure that the signal path is turned on only after the accessory is stably connected. For example, when no accessory is connected, the accessory detection circuit 10 outputs a second level signal and a low level signal; when the accessory is stably connected, the accessory detection circuit 10 outputs a first level signal and a high level signal, triggering the switch switching circuit 30 to operate.

[0049] The controlled terminal of the switch switching circuit 30 is connected to the output terminal of the clamping circuit 20, its input terminal is connected to the contact circuit 200, and its output terminal is connected to the control circuit 300 of the handheld communication device. It is used to control the connection and disconnection between the contact circuit 200 and the control circuit 300 based on the output signal of the clamping circuit 20. When no accessory is connected or the accessory is not stably connected, the clamping circuit 20 outputs a low level, the switch switching circuit 30 is open, and the connection between the contact circuit 200 and the control circuit 300 is broken. When the accessory is stably connected, the clamping circuit 20 outputs a high level, the switch switching circuit 30 is turned on, and a signal path is established between the contact circuit 200 and the control circuit 300.

[0050] The contact protection circuit and electronic device disclosed in this invention include an accessory detection circuit connected to the contact circuit. This accessory detection circuit can detect whether the contact circuit is connected to an accessory. The accessory detection circuit is also connected to a clamping circuit. When the accessory detection circuit detects a connection between the accessory and the contact circuit, it outputs a detection signal to the clamping circuit. After continuously receiving the detection signal for a certain period, the clamping circuit outputs a switch signal to a switch switching circuit. The switch switching circuit is connected to both the contact circuit and the control circuit, and it conducts upon receiving the switch signal, allowing the accessory to connect to the control circuit through the switch detection circuit. This ensures that the accessory is stably connected before being connected to the control circuit, avoiding repeated disconnections and improving stability.

[0051] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A contact protection circuit, characterized in that, The contact protection circuit, applied to electronic devices, includes: An accessory detection circuit is provided, wherein the input terminal of the signal recognition circuit is connected to the contact circuit of the electronic device, and is used to detect whether an accessory is connected. A clamping circuit, wherein the input terminal of the clamping circuit is connected to the output terminal of the accessory detection circuit; A switch switching circuit is provided, wherein the controlled terminal of the switch switching circuit is connected to the output terminal of the clamping circuit, the input terminal of the switch switching circuit is connected to the contact circuit, and the output terminal of the switch switching circuit is connected to the control circuit of the electronic device.

2. The contact protection circuit as described in claim 1, characterized in that, The accessory detection circuit includes at least one diode, the negative terminal of which is connected to the contact circuit, and the positive terminal of which is connected to the input terminal of the clamping circuit.

3. The contact protection circuit as described in claim 2, characterized in that, The accessory detection circuit includes three diodes, namely a first diode, a second diode, and a third diode; The negative terminals of the first diode, the second diode, and the third diode are all connected to the contact circuit, and the positive terminals of the first diode, the second diode, and the third diode are all connected to the input terminal of the clamping circuit.

4. The contact protection circuit as described in claim 3, characterized in that, The accessory detection circuit also includes a first resistor, a second resistor, a third resistor, a fourth resistor, and a first capacitor; The first resistor is connected in parallel with the negative terminal of the first diode, the second resistor is connected in parallel with the negative terminal of the second diode, the third resistor is connected in parallel with the negative terminal of the third diode, one end of the first capacitor is connected to the positive terminal of the first diode, the positive terminal of the second diode and the positive terminal of the third diode respectively, and the other end of the first capacitor is grounded.

5. The contact protection circuit as described in claim 1, characterized in that, The clamping circuit includes a first switching element and a reset chip; The controlled electrode of the first switching element is connected to the output terminal of the accessory detection circuit, the first electrode of the first switching element is connected to the reset chip, the second electrode of the first switching element is grounded, and the reset chip is connected to the switch switching circuit.

6. The contact protection circuit as described in claim 5, characterized in that, The clamping circuit also includes a fifth resistor, a sixth resistor, and a seventh resistor; One end of the fifth resistor is connected to the accessory detection circuit, and the other end of the fifth resistor is connected to the controlled electrode of the first switching element. One end of the sixth resistor is connected to the power supply terminal, and the other end of the sixth resistor is connected to the reset chip. One end of the seventh resistor is connected to the power supply terminal, and the other end of the seventh resistor is connected to the switch switching circuit.

7. The contact protection circuit as described in claim 5, characterized in that, The clamping circuit also includes a second capacitor and a third capacitor; One end of the second capacitor and one end of the third capacitor are both connected to the reset chip, and the other ends of the second capacitor and the third capacitor are both grounded.

8. The contact protection circuit as described in claim 1, characterized in that, The switch switching circuit includes a switching chip, which is connected to the clamping circuit, the control circuit, and the contact circuit.

9. The contact protection circuit as described in claim 8, characterized in that, The switching circuit further includes an eighth resistor and a ninth resistor; One end of the eighth resistor and one end of the ninth resistor are both connected to the clamping circuit, the other end of the eighth resistor is grounded, and the other end of the ninth resistor is connected to the switching chip.

10. An electronic device, characterized in that, The electronic device includes a control circuit, a contact circuit, and a contact protection circuit as described in any one of claims 1-9.

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