Relay drive circuit and vehicle-mounted device

Abstract

The embodiment of the application provides a relay driving circuit and a vehicle-mounted device. The working state of a relay coil is detected through a state detection circuit, and the working state of the relay coil is fed back to a controller. The controller controls a switch module to be turned on or turned off according to the working state of the relay coil, thereby controlling the relay coil to be turned on or turned off. When the relay coil works abnormally, the relay coil is turned off, and damage of the relay driving circuit is avoided.

Description

Technical Field

[0001] This application relates to the field of relay technology, and in particular to a relay drive circuit and an on-board device. Background Technology

[0002] Relays, as electrical switching devices, are widely used in various electrical equipment and electronic systems. Relays require a relay driver circuit to operate. During actual use, relays may malfunction, leading to damage to the relay driver circuit.

[0003] However, the relevant technologies lack effective means to detect the working state of the relay coil, and cannot protect the relay drive circuit based on the working state of the relay coil. Summary of the Invention

[0004] To overcome the problems existing in related technologies, this application provides a relay drive circuit and an on-board device, which can effectively detect the working state of the relay coil and protect the relay drive circuit.

[0005] According to a first aspect of the embodiments of this application, a relay driving circuit is provided, including a switching module, a state detection circuit, and a controller;

[0006] The first end of the relay coil is connected to the first power supply, and the second end of the relay coil is connected to the first signal terminal of the switch module; the drive terminal of the switch module is connected to the output terminal of the controller, and the second signal terminal of the switch module is grounded; the switch module is used to turn the relay coil on or off according to the control signal output by the controller.

[0007] The input terminal of the state detection circuit is connected to the second terminal of the relay coil, and the output terminal of the state detection circuit is connected to the input terminal of the controller. The state detection circuit is used to detect the working state of the relay coil and feed the working state back to the controller so that the controller can control the relay coil to turn on or off according to the working state.

[0008] According to a second aspect of the embodiments of this application, an in-vehicle device is provided, including a relay, a load device, and the aforementioned relay drive circuit; the relay includes a relay coil, a first contact, and a second contact, a first end of the relay coil is connected to a first power supply, a second end of the relay coil is connected to a first signal terminal of a switch module, the first contact is connected to a first end of the load device, and the second contact is connected to a second end of the load device. The relay is driven to turn on or off by the relay drive circuit, so that the first contact and the second contact are connected or disconnected, thereby connecting or disconnecting the load device.

[0009] This application embodiment detects the working state of the relay coil through a state detection circuit and feeds the working state of the relay coil back to the controller. The controller controls the switch module to turn on or off according to the working state of the relay coil, thereby controlling the relay coil to turn on or off. This ensures that when the relay coil is malfunctioning, it is disconnected, thus avoiding damage to the relay drive circuit.

[0010] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application.

[0011] To better understand and implement this invention, the following detailed description is provided in conjunction with the accompanying drawings. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the circuit structure of a relay driving circuit according to one embodiment of this application;

[0013] Figure 2 This is a schematic diagram of the specific circuit structure of a relay driving circuit according to an embodiment of this application;

[0014] Figure 3 This is a schematic diagram of the circuit structure of a relay driving circuit shown in another embodiment of this application;

[0015] Figure 4 This is a schematic diagram of the circuit structure of a relay driving circuit shown in another embodiment of this application;

[0016] Figure 5 This is a schematic diagram of the circuit structure of a relay driving circuit shown in another embodiment of this application;

[0017] Figure 6 This is a schematic diagram of the structure of a vehicle-mounted device according to one embodiment of this application. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this application clearer, the embodiments of this application will be described in further detail below with reference to the accompanying drawings.

[0019] It should be understood that the described embodiments are merely the first part of the embodiments of this application, and not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this application.

[0020] When the following description refers to the accompanying drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements.

[0021] In the description of this application, it should be understood that the terms "first," "second," "third," etc., are used only to distinguish similar objects and are not necessarily used to describe a specific order or sequence, nor should they be construed as indicating or implying relative importance. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances. The singular forms "a," "the," and "the" used in this application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise. The words "if" or "when" as used herein can be interpreted as "when," "in response to a determination." Furthermore, in the description of this application, unless otherwise stated, "a plurality" means two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist; for example, A and / or B can represent: A alone, A and B simultaneously, or B alone. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship.

[0022] Relays require a relay driver circuit to operate. During actual use, relays may malfunction, leading to damage to the relay driver circuit.

[0023] In related technologies, there is a lack of effective means to detect the working state of relay coils, making it impossible to protect the relay drive circuit based on the working state of the relay coils.

[0024] Therefore, this application provides a relay driving circuit that, through the joint cooperation of a switching module, a state detection circuit, and a controller, realizes the detection of the working state of the relay coil, and controls the relay coil to be turned on or off according to the working state of the relay coil, so as to avoid damage to the relay driving circuit when the working state of the relay coil is abnormal.

[0025] Please see Figure 1 This is a schematic diagram of the relay driving circuit shown in an embodiment of this application. The relay driving circuit provided in this embodiment includes a switch module 10, a state detection circuit 20, and a controller 30;

[0026] The first end of the relay coil is connected to the first power supply, and the second end of the relay coil is connected to the first signal terminal of the switch module 10; the drive terminal of the switch module 10 is connected to the output terminal of the controller 30, and the second signal terminal of the switch module 10 is grounded; the switch module 10 is used to turn the relay coil on or off according to the control signal output by the controller 30.

[0027] The input terminal of the state detection circuit 20 is connected to the second terminal of the relay coil, and the output terminal of the state detection circuit 20 is connected to the input terminal of the controller 30. The state detection circuit 20 is used to detect the working state of the relay coil and feed the working state back to the controller 30 so that the controller 30 can control the relay coil to be turned on or off according to the working state.

[0028] The switching module 10 is used to turn the relay coil on or off according to the control signal output by the controller 30. Specifically, the switching module 10 includes, but is not limited to, transistors and MOSFETs.

[0029] The status detection circuit 20 is used to detect the operating status of the relay coil. Specifically, the status detection circuit 20 can be a control chip or multiple resistors connected in series and parallel.

[0030] The controller 30 is used to output control signals to control the relay coil to turn on or off. Specifically, the controller 30 can be an MCU, and the control signal can be a high level or a low level.

[0031] The relay includes a relay coil, a first contact, and a second contact. When the relay coil is energized, the first contact and the second contact are connected. When the relay coil is de-energized, the first contact and the second contact are disconnected.

[0032] The first power source is a DC power source.

[0033] The operating states of a relay include, but are not limited to, the normal state of the relay coil, the open-circuit state of the relay coil, and the short-circuit state of the relay coil.

[0034] In this embodiment, the controller 30 outputs a high-level signal to the switch module 10, turning the switch module 10 on. The current output from the first power supply flows through the relay coil and the switch module 10 to the ground terminal, forming a closed loop, and the relay coil is energized. When the controller 30 outputs a low-level signal to the switch module 10, the switch module 10 is turned off. The current output from the first power supply cannot flow through the relay coil and the switch module 10 to the ground terminal, thus failing to form a closed loop. The relay coil receives no current and does not operate. When the relay coil is energized, the state detection circuit 20 detects a voltage value, which is the voltage after dividing the relay coil's internal resistance by the series voltage divider of the resistors in the state detection circuit 20. When the relay coil experiences an open circuit or short circuit, the state detection circuit 20 detects another voltage value. The state detection circuit 20 sends the detected voltage value to the controller 30, which determines the operating state of the relay coil based on the voltage value. When the relay coil's operating state is abnormal, a low-level signal is output, turning off the switch module 10. When the relay coil's operating state is normal, a high-level signal continues to be output, turning on the switch module 10.

[0035] In the embodiments of this application, the operating state of the relay coil is detected by the state detection circuit 20 and fed back to the controller 30. The controller 30 controls the switch module 10 to be turned on or off according to the operating state of the relay coil, thereby controlling the relay coil to be turned on or off. This ensures that when the relay coil is malfunctioning, the relay coil is disconnected, thus avoiding damage to the relay drive circuit.

[0036] In one embodiment, see Figure 2 The status detection circuit 20 includes a first resistor R1 and a second resistor R4;

[0037] The first end of the first resistor R1 is the input terminal of the state detection circuit 20, the second end of the first resistor R1 is the output terminal of the state detection circuit 20, the first end of the second resistor R4 is connected to the second end of the first resistor R1, and the second end of the second resistor R4 is grounded.

[0038] In this embodiment, the first resistor R1 and the second resistor R4 are connected in series, and the state detection circuit 20 outputs the voltage across the second resistor R4 to the controller 30. When the relay coil is working normally, the voltage supplied by the first power supply is divided by the relay coil's internal resistance, the first resistor R1, and the second resistor R4 in series, and the voltage across the second resistor R4 is a certain voltage value. When the relay coil is open-circuited or short-circuited, the voltage across the second resistor R4 is 0.

[0039] According to the embodiments of this application, the working state of the relay coil can be accurately determined based on the voltage across the second resistor R4.

[0040] In one embodiment, see Figure 2 The state detection circuit 20 also includes a third resistor R5, a first diode D3, and a first capacitor C3;

[0041] The first end of the third resistor R5 is connected to the second end of the first resistor R1, and the second end of the third resistor R5 is connected to the input end of the controller 30.

[0042] The cathode of the first diode D3 is connected to the second power supply, and the anode of the first diode D3 is connected to the second terminal of the third resistor R5.

[0043] The first terminal of the first capacitor C3 is connected to the second terminal of the third resistor R5, and the second terminal of the first capacitor C3 is grounded.

[0044] In this embodiment, the third resistor R5 is a current-limiting resistor to prevent excessive current at the input terminal of the controller 30. The first diode D3 is used for overvoltage protection at the input terminal of the controller 30, and the first capacitor C3 is used for filtering.

[0045] In this embodiment of the application, by setting a third resistor R5, a first diode D3 and a first capacitor C3, overcurrent and overvoltage protection and filtering can be provided for the input terminal of the controller 30, so as to avoid damage to the controller 30 and improve the signal quality of the input terminal of the controller 30.

[0046] In one embodiment, see Figure 3 The relay drive circuit also includes an overcurrent protection circuit 40;

[0047] The input terminal of the overcurrent protection circuit 40 is connected to the second signal terminal of the switching module 10, and the output terminal of the overcurrent protection circuit 40 is connected to the drive terminal of the switching module 10.

[0048] The overcurrent protection circuit 40 is used to disconnect the switch module 10 when the current of the relay coil is greater than the preset current threshold, so as to provide overcurrent protection for the relay drive circuit; after the switch module 10 is disconnected, the switch module 10 is turned on again.

[0049] The state detection circuit 20 is used to output the detected first operating state to the controller 30 when the switch module 10 is turned off; and to output the detected second operating state to the controller 30 when the switch module 10 is turned on again; the controller 30 is used to control the relay coil to turn off through the switch module 10 when it is determined that the relay coil is in an overcurrent operating state based on the transition between the first operating state and the second operating state.

[0050] The preset current threshold can be manually set according to actual needs.

[0051] In this embodiment, when the current in the relay coil exceeds a preset current threshold, the overcurrent protection circuit 40 activates, controlling the switch module 10 to disconnect, thus reducing the current in the relay coil to zero. After the switch module 10 disconnects, the overcurrent protection circuit 40 deactivates, and the switch module 10 continues to receive a high-level signal from the control module, reactivating. When the switch module 10 reactivates, the current in the relay coil exceeds the preset current threshold, triggering the overcurrent protection circuit 40 to activate and disconnect the switch module 10. Therefore, when the current in the relay coil exceeds the preset current threshold, the switch module 10 repeatedly switches between disconnected and activated states under the action of the overcurrent protection circuit 40. When the switch module 10 is in the ON state, the voltage value detected by the state detection circuit 20 is non-zero. When the switch module 10 is in the OFF state, the voltage value detected by the state detection circuit 20 is 0. Therefore, the state detection circuit 20 will detect the voltage value jumping between 0 and non-zero, and output the detected voltage value to the controller 30. The controller 30 determines that the relay coil is in an overcurrent working state based on the voltage jump value, and outputs a low level to the switch module 10, so that the switch module 10 is always OFF, thereby controlling the relay coil to disconnect.

[0052] In this embodiment, the overcurrent protection circuit 40 provides temporary overcurrent protection for the relay drive circuit, and the status detection circuit 20 provides permanent overcurrent protection for the relay drive circuit, thus preventing damage to the relay drive circuit.

[0053] In one embodiment, see Figure 2 The overcurrent protection circuit 40 includes a fourth resistor R6, a fifth resistor R7, and a switching transistor Q2.

[0054] The first end of the fourth resistor R6 is the input terminal of the overcurrent protection circuit 40, and the second end of the fourth resistor R6 is grounded; the driving terminal of the switch Q2 is connected to the first end of the fourth resistor R6 through the fifth resistor R7, the first signal terminal of the switch Q2 is the output terminal of the overcurrent protection circuit 40, and the second signal terminal of the switch Q2 is grounded.

[0055] Among them, the switching transistor Q2 includes, but is not limited to, transistors and MOSFETs.

[0056] In this embodiment, the switching transistor Q2 is a transistor Q2, and the switching module 10 is a transistor Q1. When the current in the relay coil is too large, the voltage drop across the fourth resistor R6 increases. When the voltage across the fourth resistor R6 is greater than the turn-on voltage of transistor Q2, transistor Q2 turns on, the base of transistor Q1 is pulled low, and transistor Q1 turns off. When transistor Q1 turns off, the current in the relay coil is 0, the voltage across the fourth resistor R6 is 0, transistor Q2 turns off, the base of transistor Q1 receives the high level output by the controller 30, and transistor Q1 turns on again.

[0057] In this embodiment, the overcurrent protection circuit 40, through the combined action of the fourth resistor R6, the fifth resistor R7, and the switching transistor Q2, can control the switching module 10 to disconnect when the relay coil is in an overcurrent state, thus preventing damage to the relay drive circuit.

[0058] In one embodiment, the overcurrent protection circuit 40 further includes a sixth resistor R9, a seventh resistor R10, and a second capacitor C4.

[0059] The first end of the sixth resistor R9 is connected to the first signal terminal of the switching transistor, and the second end of the sixth resistor R9 is connected to the output terminal of the controller 30.

[0060] The first terminal of the seventh resistor R10 is connected to the second terminal of the sixth resistor R9, and the second terminal of the seventh resistor R10 is grounded.

[0061] The first terminal of the second capacitor C4 is connected to the second terminal of the sixth resistor R9, and the second terminal of the second capacitor C4 is grounded.

[0062] In this embodiment, the sixth resistor R9 is a current-limiting resistor, and the seventh resistor R10 and the second capacitor C4 form an RC filter circuit to filter out noise in the circuit. The control signal output by the controller 30 passes through the sixth resistor R9, the seventh resistor R10 and the second capacitor C4, and reaches the base of the transistor Q1 to control the conduction or disconnection of the transistor Q1.

[0063] The embodiments of this application can improve the quality of the control signal by setting a sixth resistor R9, a seventh resistor R10, and a second capacitor C4.

[0064] In one embodiment, see Figure 4 The relay drive circuit also includes an overvoltage protection circuit 50;

[0065] The input terminal of the overvoltage protection circuit 50 is connected to the second terminal of the relay coil, and the output terminal of the overvoltage protection circuit 50 is connected to the first signal terminal of the switching module 10.

[0066] The overvoltage protection circuit 50 is used to absorb the pulse voltage when the pulse voltage generated by the relay coil is greater than or equal to a first preset voltage threshold, so as to provide overvoltage protection for the relay drive circuit.

[0067] The first preset voltage threshold can be manually set according to actual needs. Specifically, the first preset voltage threshold is a multiple of the voltage of the first power supply. For example, if the voltage of the first power supply is 12V, the first preset voltage threshold is 120V.

[0068] In this embodiment, when the relay coil is first energized or immediately de-energized, it generates a pulse voltage, which may reach hundreds of volts and damage the relay drive circuit. Therefore, an overvoltage protection circuit 50 is provided to absorb the pulse voltage and protect the relay drive circuit.

[0069] In one embodiment, see Figure 2 The overvoltage protection circuit 50 includes a second diode D1, an eighth resistor R1, a third capacitor C1, and an inductor L1.

[0070] The anode of the second diode D1 is the input terminal of the overvoltage protection circuit 50, and the cathode of the second diode D1 is connected to the second power supply.

[0071] The first end of the eighth resistor R1 is connected to the anode of the second diode D1, the second end of the eighth resistor R1 is connected to the first end of the third capacitor C1, and the second end of the third capacitor C1 is grounded.

[0072] The first end of inductor L1 is connected to the anode of the second diode D1, and the second end of inductor L1 is the output of the overvoltage protection circuit 50.

[0073] In this embodiment, the pulse voltage generated by the relay coil is first clamped and protected by the second diode D1. Most of the energy is directed into a power supply network with a larger capacitive voltage (second power supply), and the remaining part is buffered by the eighth resistor R1 and the third capacitor C1 to suppress ringing that may be caused by the inductive load of the relay. Inductor L1 is used to suppress electromagnetic interference in the circuit.

[0074] By setting the second diode D1, the eighth resistor R1, the third capacitor C1, and the inductor L1, the pulse voltage generated by the relay coil can be absorbed, thus providing overvoltage protection for the relay drive circuit.

[0075] In one embodiment, the state detection circuit 20 is used to send the operating state of the relay coil to the controller 30. When the voltage value corresponding to the operating state is greater than or equal to the second preset voltage threshold, the controller 30 determines that the relay drive circuit is in an overvoltage state and controls the relay coil to disconnect through the switching module 10.

[0076] The second preset voltage threshold can be manually set according to actual needs. Specifically, the second preset voltage threshold is close to the voltage value of the first power supply, and is less than the first preset voltage threshold. For example, if the voltage value of the first power supply is 12V, the second preset voltage threshold is 10V.

[0077] When the internal resistance of the relay coil suddenly decreases, it can cause the relay drive circuit to be in an overvoltage state.

[0078] In this embodiment, the state detection circuit 20 outputs the detected voltage value to the controller 30. The controller 30 compares the voltage value with a second preset voltage threshold. When the voltage value is greater than or equal to the second preset voltage threshold, the controller 30 determines that the relay drive circuit is in an overvoltage state and outputs a low level to the switch module 10, causing the switch module 10 to open, thereby controlling the relay coil to open. When the voltage value is less than the second preset voltage threshold, the controller 30 determines that the relay drive circuit is not in an overvoltage state and continues to output a high level to the switch module 10, causing the switch module 10 to turn on, controlling the relay coil to turn on.

[0079] In this embodiment, the voltage value output by the state detection circuit 20 to the controller 30 can accurately determine whether the relay drive circuit is in an overvoltage state.

[0080] In one embodiment, see Figure 5 The relay drive circuit also includes an excitation source circuit 60;

[0081] The input terminal of the excitation source circuit 60 is connected to the third power supply, and the output terminal of the excitation source circuit 60 is connected to the first signal terminal of the switching module 10; wherein, the voltage value of the third power supply is less than the voltage value of the first power supply.

[0082] The excitation source circuit 60 is used to divide the voltage value of the third power supply and output the divided voltage value to the state detection circuit 20. The state detection circuit 20 is used to send the working state of the relay coil to the controller 30. When the voltage value corresponding to the working state is greater than 0 and less than or equal to the third preset voltage threshold, the controller 30 determines that the relay coil is in an open circuit state. When the voltage value corresponding to the working state is 0, the controller 30 determines that the relay coil is in a short circuit state.

[0083] The voltage of the third power supply is lower than that of the first power supply. For example, the voltage of the first power supply is 12V, and the voltage of the third power supply is 6V.

[0084] The third preset voltage threshold can be manually set according to actual needs. Specifically, the third preset voltage threshold is a smaller voltage value, which is less than the second preset voltage threshold. For example, the third preset voltage threshold is 0.9V.

[0085] In this embodiment, when the relay coil is operating normally, the excitation source circuit 60 is bypassed because the voltage of the first power supply is greater than that of the third power supply, thus not affecting the switching module 10 or the state detection circuit 20. When the relay coil is open-circuited, the first power supply no longer provides voltage. At this time, the third power supply outputs a low-voltage DC excitation source through the excitation source circuit 60, and the state detection circuit 20 can detect a voltage value greater than 0. When the relay coil is short-circuited to ground, the voltage value detected by the state detection circuit 20 is 0. The controller 30 can determine the operating state of the relay coil based on the voltage value detected by the state detection circuit 20.

[0086] This application embodiment, by setting the excitation source circuit 60, can accurately distinguish whether the relay coil is in an open-circuit state or a short-circuit state.

[0087] In one embodiment, see Figure 2 The excitation source circuit 60 includes a third diode D2 and a ninth resistor R2;

[0088] The anode of the third diode D2 is the input terminal of the excitation source circuit 60, the cathode of the third diode D2 is connected to the first terminal of the ninth resistor R2, and the second terminal of the ninth resistor R2 is the output terminal of the excitation source circuit 60.

[0089] In this embodiment, the third diode D2 is used to prevent reverse current flow, and the ninth resistor R2 is used to protect the third power supply and the third diode D2 from being burned out when the relay coil is short-circuited to ground.

[0090] In this embodiment, the third diode D2 and the ninth resistor R2 work together to ensure that the voltage detected by the state detection circuit is not zero when the relay coil is open-circuited, thereby quickly distinguishing between the open-circuit and short-circuit states of the relay coil.

[0091] In one embodiment, see Figure 6 This application also provides an on-board device, including a relay 100, a load device 200, and the aforementioned relay drive circuit 300. The relay 100 includes a relay coil, a first contact, and a second contact. The first end of the relay coil is connected to a first power supply, and the second end of the relay coil is connected to a first signal terminal of a switch module. The first contact is connected to the first end of the load device 200, and the second contact is connected to the second end of the load device 200. The relay drive circuit 300 drives the relay coil to conduct or disconnect, thereby connecting or disconnecting the first contact and the second contact, and connecting or disconnecting the load device.

[0092] The load device can be an in-vehicle electrical appliance, which includes, but is not limited to, vehicle lights, sensors, and motors.

[0093] In this embodiment, the relay drive circuit controls the relay coil to conduct, energizing the relay coil and connecting the first and second contacts to connect the load device, thus enabling the load device to operate. Conversely, the relay drive circuit controls the relay coil to de-energize, de-energizing the relay coil and disconnecting the first and second contacts, thus disconnecting the load device and preventing it from operating.

[0094] By applying the embodiments of this application and using the aforementioned relay drive circuit, the relay can be driven to operate, enabling the load device to function. Simultaneously, since the relay drive circuit can detect the operating state of the relay coil and provide overcurrent and overvoltage protection, damage to the on-board equipment can be prevented.

[0095] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0096] The above are merely embodiments of this application and are not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A relay drive circuit, characterized in that, Includes a switch module, a status detection circuit, and a controller; The first end of the relay coil is connected to a first power supply, and the second end of the relay coil is connected to the first signal terminal of the switch module; the drive terminal of the switch module is connected to the output terminal of the controller, and the second signal terminal of the switch module is grounded; the switch module is used to turn the relay coil on or off according to the control signal output by the controller. The input terminal of the state detection circuit is connected to the second terminal of the relay coil, and the output terminal of the state detection circuit is connected to the input terminal of the controller. The state detection circuit is used to detect the working state of the relay coil and feed the working state back to the controller so that the controller can control the relay coil to be turned on or off according to the working state.

2. The relay drive circuit according to claim 1, characterized in that: The state detection circuit includes a first resistor and a second resistor; The first end of the first resistor is the input terminal of the state detection circuit, the second end of the first resistor is the output terminal of the state detection circuit, the first end of the second resistor is connected to the second end of the first resistor, and the second end of the second resistor is grounded.

3. The relay drive circuit according to claim 2, characterized in that: The state detection circuit also includes a third resistor, a first diode, and a first capacitor; The first end of the third resistor is connected to the second end of the first resistor, and the second end of the third resistor is connected to the input end of the controller; The cathode of the first diode is connected to the second power supply, and the anode of the first diode is connected to the second terminal of the third resistor; The first terminal of the first capacitor is connected to the second terminal of the third resistor, and the second terminal of the first capacitor is grounded.

4. The relay drive circuit according to any one of claims 1 to 3, characterized in that, The relay drive circuit also includes an overcurrent protection circuit. The input terminal of the overcurrent protection circuit is connected to the second signal terminal of the switching module, and the output terminal of the overcurrent protection circuit is connected to the driving terminal of the switching module. The overcurrent protection circuit is used to disconnect the switching module when the current of the relay coil is greater than a preset current threshold, so as to provide overcurrent protection for the relay drive circuit; after the switching module is disconnected, the switching module is turned on again. The state detection circuit is used to output a detected first operating state to the controller when the switch module is disconnected; and to output a detected second operating state to the controller when the switch module is turned back on. The controller is used to control the relay coil to disconnect via the switching module when it is determined that the relay coil is in an overcurrent operating state based on the transition between the first operating state and the second operating state.

5. The relay drive circuit according to claim 4, characterized in that: The overcurrent protection circuit includes a fourth resistor, a fifth resistor, and a switching transistor; The first end of the fourth resistor is the input end of the overcurrent protection circuit, and the second end of the fourth resistor is grounded; the driving end of the switching transistor is connected to the first end of the fourth resistor through the fifth resistor, the first signal end of the switching transistor is the output end of the overcurrent protection circuit, and the second signal end of the switching transistor is grounded.

6. The relay drive circuit according to claim 5, characterized in that: The overcurrent protection circuit also includes a sixth resistor, a seventh resistor, and a second capacitor; The first end of the sixth resistor is connected to the first signal terminal of the switching transistor, and the second end of the sixth resistor is connected to the output terminal of the controller. The first end of the seventh resistor is connected to the second end of the sixth resistor, and the second end of the seventh resistor is grounded; The first terminal of the second capacitor is connected to the second terminal of the sixth resistor, and the second terminal of the second capacitor is grounded.

7. The relay drive circuit according to any one of claims 1 to 3, characterized in that, The relay drive circuit also includes an overvoltage protection circuit. The input terminal of the overvoltage protection circuit is connected to the second terminal of the relay coil, and the output terminal of the overvoltage protection circuit is connected to the first signal terminal of the switching module. The overvoltage protection circuit is used to absorb the pulse voltage when the pulse voltage generated by the relay coil is greater than or equal to a first preset voltage threshold, so as to provide overvoltage protection for the relay drive circuit.

8. The relay drive circuit according to claim 7, characterized in that: The overvoltage protection circuit includes a second diode, an eighth resistor, a third capacitor, and an inductor; The anode of the second diode is the input terminal of the overvoltage protection circuit, and the cathode of the second diode is connected to the second power supply. The first end of the eighth resistor is connected to the anode of the second diode, the second end of the eighth resistor is connected to the first end of the third capacitor, and the second end of the third capacitor is grounded. The first end of the inductor is connected to the anode of the second diode, and the second end of the inductor is the output terminal of the overvoltage protection circuit.

9. The relay drive circuit according to any one of claims 1 to 3, characterized in that: The state detection circuit is used to send the operating state of the relay coil to the controller. When the voltage value corresponding to the operating state is greater than or equal to the second preset voltage threshold, the controller determines that the relay drive circuit is in an overvoltage state and controls the relay coil to disconnect through the switching module.

10. The relay drive circuit according to any one of claims 1 to 3, characterized in that, The relay drive circuit also includes an excitation source circuit; The input terminal of the excitation source circuit is connected to a third power supply, and the output terminal of the excitation source circuit is connected to the first signal terminal of the switching module; wherein, the voltage value of the third power supply is less than the voltage value of the first power supply. The excitation source circuit is used to divide the voltage value of the third power supply and output the divided voltage value to the state detection circuit; the state detection circuit is used to send the operating state of the relay coil to the controller. When the voltage value corresponding to the operating state is greater than 0 and less than or equal to a third preset voltage threshold, the controller determines that the relay coil is in an open circuit state; when the voltage value corresponding to the operating state is 0, the controller determines that the relay coil is in a short circuit state.

11. The relay drive circuit according to claim 10, characterized in that: The excitation source circuit includes a third diode and a ninth resistor; The anode of the third diode is the input terminal of the excitation source circuit, the cathode of the third diode is connected to the first terminal of the ninth resistor, and the second terminal of the ninth resistor is the output terminal of the excitation source circuit.

12. A vehicle-mounted device, characterized in that, The device includes a relay, a load device, and a relay drive circuit as described in any one of claims 1 to 11. The relay includes a relay coil, a first contact, and a second contact. A first end of the relay coil is connected to a first power supply, and a second end of the relay coil is connected to a first signal terminal of the switch module. The first contact is connected to a first end of the load device, and the second contact is connected to a second end of the load device. The relay drive circuit drives the relay coil to turn on or off, thereby connecting or disconnecting the first contact and the second contact, and connecting or disconnecting the load device.

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