Relay protection circuit, control system and door control device

Abstract

The utility model relates to a relay protection circuit, a control system and a door control device, the relay protection circuit comprises a voltage reduction time delay module, a switch module, a detection control module, a strong current control module, a direct current power supply and a relay, the input end of the voltage reduction time delay module is connected with the direct current power supply, and the output end of the voltage reduction time delay module is connected with the first end of a coil of the relay; the second end of the coil is connected with the switch module, the strong current control module is arranged on a branch where a contact of the relay is located, and the detection control module is connected with the direct-current power source and the strong current control module. The detection control module in the relay protection circuit sends the control signal to the strong current control module to disconnect the branch where the contact is located when the direct current power supply is powered down, the power-off time of the branch where the coil is located is later than the power-off time of the branch where the contact is located under the action of the voltage-reducing delay module, and the relay contact is disconnected after the large current disappears, so that the relay is protected. Ablation can be avoided, so that the relay and an electrical connecting piece thereof are protected.

Description

Technical Field

[0001] This application relates to the field of control circuit technology, and in particular to a relay protection circuit, a control system, and a gate control device. Background Technology

[0002] Relays are one of the most commonly used components in electronic products. They are typically used for strong and weak current isolation, enabling weak current to control strong current. Their working principle is as follows: when a low-voltage DC source supplies power to the coil on the weak current side of the relay, the strong current side contacts close under the action of electromagnetic principles to complete the connection of the strong current side circuit; otherwise, the strong current side circuit is disconnected.

[0003] Currently, relay control circuits still have the following defects: When the DC power source on the weak current side fails to power, the relay coil on the weak current side is de-energized, and the relay contacts immediately release. Since the voltage on the strong current side circuit is still present, a large current still passes through the relay contacts. Under the action of high voltage and high current, the energy is high at the moment the contacts open, and the relay contacts may be burned and stuck, which may lead to relay failure and circuit board failure. Summary of the Invention

[0004] To address at least one of the aforementioned technical problems, this application proposes a relay protection circuit, a control system, and a gate control device.

[0005] According to some embodiments of this application, a relay protection circuit is provided, including a step-down delay module, a switching module, a detection and control module, a high-voltage control module, a DC power supply, and a relay. The input terminal of the step-down delay module is connected to the DC power supply, the output terminal of the step-down delay module is connected to the first terminal of the relay coil, and the second terminal of the coil is connected to the switching module. The switching module is used to control the on / off state of the branch where the coil is located. The step-down delay module is used to supply power to the branch where the coil is located. The step-down delay module includes a step-down circuit and a charging / discharging circuit disposed at the output terminal of the step-down circuit. The high-voltage control module is disposed in the branch where the relay contacts are located and is used to control the on / off state of the branch where the contacts are located. The detection and control module is connected to both the DC power supply and the high-voltage control module, and is used to detect the power-off state of the DC power supply to send a control signal to the high-voltage control module.

[0006] Based on the above scheme, when the DC power supply fails, the detection and control module sends a control signal to the high-voltage control module to disconnect the branch where the contact is located. Under the action of the step-down delay module, the power-off time of the branch where the coil is located is later than the power-off time of the branch where the contact is located. The relay contact disconnects after the large current disappears, which can avoid burning and thus protect the relay and its electrical connections.

[0007] In some possible implementations, the step-down circuit includes a low-dropout regulator, and the charging / discharging circuit includes an output capacitor; a first terminal of the low-dropout regulator is connected to the DC power supply, a second terminal of the low-dropout regulator is grounded, a third terminal of the low-dropout regulator is connected to the first terminal of the coil, an input capacitor is provided between the first and second terminals of the low-dropout regulator, and an output capacitor is provided between the third and second terminals of the low-dropout regulator.

[0008] Based on the above scheme, by setting a low-dropout regulator as part of the step-down circuit, the low-dropout regulator can enhance the stability of the step-down. In conjunction with the output capacitor of the discharge circuit, it can achieve the effect of slow power loss in the branch where the coil is located after the DC power supply fails. In addition, the low-dropout regulator can also reduce the risk of capacitor capacity degradation after long-term use.

[0009] In some possible implementations, the output capacitor is a variable capacitor.

[0010] Based on the above scheme, the output capacitor is set as a variable capacitor. By adjusting the capacitance value of the variable capacitor, the charging and discharging speed of the buck delay module can be adjusted, thereby changing the power-off time of the branch where the coil is located, so as to ensure that the contact is disconnected after the large current in the branch where the contact is located disappears.

[0011] In some possible implementations, the detection control module is connected to the switch module, and the detection control module is also used to send a switch control signal to the switch module to control the on / off state of the switch module.

[0012] Based on the above solution, the control part of the switching module can be integrated with the detection control module. The detection control module can simultaneously monitor the DC power failure, the continuity of the branch where the coil is located, and the continuity of the branch where the control contact is located, which can effectively reduce the redundancy of the circuit.

[0013] In some possible implementations, the switching module includes a transistor, the collector of which is connected to the second end of the coil, the emitter of which is grounded, and the base of which is connected to the detection and control module.

[0014] Based on the above scheme, a transistor is used to realize the function of the switching module. The circuit structure is simple and efficient, which helps to reduce costs.

[0015] In some possible implementations, the switching module further includes a protection diode, the anode of which is connected to the collector of the transistor, and the cathode of which is connected to the output of the buck delay module.

[0016] Based on the above scheme, setting up a protection diode can dissipate excess current and ensure the stability of the transistor's operation.

[0017] In some possible implementations, the detection control module includes a microcontroller and a power-down detection circuit. The power-down detection circuit includes a voltage divider unit and an isolation detection unit. The voltage divider unit is used to divide the DC power supply to obtain a voltage divider signal. The isolation detection unit is used to output a voltage divider feedback signal based on the voltage divider signal. The microcontroller is used to detect the voltage divider feedback signal to determine the power-down status of the DC power supply.

[0018] Based on the above scheme, the power failure monitoring circuit using the voltage divider unit and the isolation monitoring unit can convert the DC power supply signal into a voltage divider feedback signal that is easy for the microcontroller to recognize, thereby improving the accuracy of DC power failure monitoring.

[0019] In some possible implementations, the high-voltage control module includes a smart power module.

[0020] Based on the above solution, by setting up an intelligent power module, the stability and response speed of the on / off control of the branch where the contact is located can be improved.

[0021] According to some other embodiments of this application, a control system is provided, including a relay protection circuit as described in any of the above embodiments, and further including a power controller, the power controller being used to control the power-on and power-off of the DC power supply, and the control system being used to, when the DC power supply is cut off, first cut off the branch where the relay contacts are located, and then cut off the branch where the relay coil is located to disconnect the relay contacts.

[0022] Based on the above scheme, the control system can directly control the branch where the relay contacts are located to disconnect by the detection and control circuit, or control the DC power supply to disconnect the branch where the relay contacts are located, thus enabling the control system to have multiple relay control modes.

[0023] According to some other embodiments of this application, a door control device is provided, including a door control unit and a control system as described in the above embodiments, wherein the door control unit is used to control the power controller to cut off the DC power supply when the door is detected to be open.

[0024] Based on the above scheme, when the door is opened, the door control unit can control the cutting off of the DC power supply and thus cut off the branch where the relay contacts are located, so that the door control device has the effect of stopping the equipment controlled by the relay when the door is opened, thereby improving the safety of equipment operation.

[0025] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this application.

[0026] Other features and aspects of this application will become clear from the following detailed description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0027] To more clearly illustrate the technical solutions and advantages in the embodiments or prior art of this specification, the drawings used in the description of the embodiments or prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this specification. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 A structural block diagram of a relay control circuit in the related art is shown;

[0029] Figure 2 This diagram shows a structural block diagram of a relay protection circuit according to an embodiment of this application;

[0030] Figure 3 A circuit diagram of a relay protection circuit according to an embodiment of this application is shown;

[0031] Figure 4 This diagram shows a structural block diagram of a detection control module according to an embodiment of this application;

[0032] Figure 5 A structural block diagram of a control system according to an embodiment of this application is shown.

[0033] In the picture,

[0034] 1. Step-down delay module; 11. Step-down circuit; 12. Charging and discharging circuit; 2. Switching module; 3. Detection and control module; 31. Microcontroller; 32. Power failure detection circuit; 4. High-voltage control module; 5. DC power supply; 6. Relay; 7. Power controller. Detailed Implementation

[0035] The technical solutions in the embodiments of this specification will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this specification, and not all embodiments. Based on the embodiments in this specification, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0036] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or server that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or devices.

[0037] Various exemplary embodiments, features, and aspects of this application will now be described in detail with reference to the accompanying drawings. The same reference numerals in the drawings denote elements that have the same or similar functions. Although various aspects of the embodiments are shown in the drawings, they are not necessarily drawn to scale unless specifically indicated otherwise.

[0038] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments.

[0039] In this document, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three cases: A alone, A and B simultaneously, and B alone. Furthermore, the term "at least one" in this document means any combination of at least two of any one or more elements. For example, including at least one of A, B, and C can mean including any one or more elements selected from the set consisting of A, B, and C.

[0040] Furthermore, to better illustrate this application, numerous specific details are provided in the following detailed description. Those skilled in the art should understand that this application can be implemented without certain specific details. In some instances, methods, means, components, and circuits well-known to those skilled in the art have not been described in detail in order to highlight the main points of this application.

[0041] In related technologies, the design concept of relay control circuits is as follows: Figure 1 As shown, a DC low-voltage source and a switching module are installed on the relay coil side. After being energized, the coil generates magnetic force to control the relay contacts to close. This scheme has the following disadvantages: when the DC low-voltage source suddenly loses power due to a fault or other reasons, the coil is de-energized, and the relay contacts immediately release. At this time, the high voltage and high current in the branch where the contacts are located still exist, which can easily lead to contact erosion and adhesion, causing relay failure.

[0042] To address the aforementioned technical problems, this application provides a relay protection circuit. On one hand, the protection circuit can detect whether the DC power supply on the coil side has failed, and immediately control the branch where the contact is located to disconnect the power when the DC power supply fails. On the other hand, the protection circuit includes a delay circuit in the branch where the coil is located, so that after the DC power supply fails, the branch where the coil is located slowly disconnects the power, so that the contact opens only after the branch where the contact is located is disconnected, thus preventing the contact from burning out and protecting the relay.

[0043] Please refer to Figure 2 , Figure 2 A relay protection circuit according to an embodiment of this application is shown, including a step-down delay module 1, a switch module 2, a detection and control module 3, a high-voltage control module 4, a DC power supply 5, and a relay 6. The input terminal of the step-down delay module 1 is connected to the DC power supply 5, the output terminal of the step-down delay module 1 is connected to the first end of the coil of the relay 6, the second end of the coil is connected to the switch module 2, the high-voltage control module 4 is disposed in the branch where the contacts of the relay 6 are located, and the detection and control module 3 is connected to both the DC power supply 5 and the high-voltage control module 4.

[0044] Among them, the step-down delay module 1 is used to step down the voltage signal of the DC power supply 5 and then send it to the coil to supply power to the branch where the coil is located; the switch module 2 is used to control the on / off of the branch where the coil is located; the high-voltage control module 4 is used to control the on / off of the branch where the contact is located; and the detection control module 3 is used to detect the power failure state of the DC power supply 5 and send a control signal to the high-voltage control module 4.

[0045] Based on the above circuit structure, the specific working process of the protection circuit includes: when the DC power supply 5 loses power, the detection and control circuit detects the power loss state and sends a control signal to the high-voltage control module 4. The high-voltage control module 4 responds to the control signal by disconnecting the power supply to the branch where the contact is located. After the DC power supply 5 loses power, the output voltage signal of the step-down delay module 1 slowly drops to 0 within a period of time, so that the power-off time of the branch where the coil is located is after the power-off time of the branch where the contact is located, that is, the contact is disconnected after the power supply to the branch where the contact is located is disconnected, thereby avoiding the contact from being burned and stuck due to high current.

[0046] In this embodiment, the step-down delay module 1 includes a step-down circuit 11 and a charging / discharging circuit 12 disposed at the output terminal of the step-down circuit 11. The input terminal of the step-down circuit 11 is connected to the DC power supply 5. The step-down circuit 11 is used to step down the output voltage signal of the DC power supply 5, and the resulting stepped-down signal is applied to the charging / discharging circuit 12. It should be understood that this application does not limit the selection of the step-down circuit 11 and the charging / discharging circuit 12. For example, the step-down circuit 11 can be a switching step-down circuit 11 (such as MOSFET, BJT, etc.), a step-down regulator circuit, a BUCK circuit (step-down converter circuit), or other step-down circuits 11, etc. Similarly, the charging / discharging circuit 12 can be a single or multiple energy storage elements, or a circuit or module based on energy storage elements.

[0047] In some embodiments, the buck circuit 11 includes a low-dropout regulator (LDO), and the charge / discharge circuit 12 includes an output capacitor. Specifically, please refer to... Figure 3 The first terminal of the low-dropout regulator is connected to the DC power supply 5, the second terminal of the low-dropout regulator is grounded, the third terminal of the low-dropout regulator is connected to the first terminal of the coil of the relay 6, an input capacitor is provided between the first and second terminals of the low-dropout regulator (i.e., the input port of the low-dropout regulator has an input capacitor), and an output capacitor is provided between the third and second terminals of the low-dropout regulator (i.e., the output port of the low-dropout regulator has an output capacitor).

[0048] Based on the above structure, when the DC power supply 5 is powered on, the low-dropout regulator steps down the voltage signal of the DC power supply 5 and charges the output capacitor until the voltage of the input capacitor reaches the stepped-down voltage. In the above embodiment, the reason for using a low-dropout regulator is that it can reduce fluctuations in the output voltage signal, preventing voltage instability from affecting the performance of the output capacitor, which could lead to a reduction in output capacitor capacity and a shorter lifespan.

[0049] It is worth noting that in this embodiment, the component that achieves the delay effect is mainly the charging and discharging circuit 12, and the function of the step-down circuit 11 is to provide a stable voltage signal to protect the charging and discharging circuit 12. That is to say, the step-down circuit 11 can be a step-down circuit 11 without delay function, such as a voltage regulator, or a step-down circuit 11 with delay function, such as a BUCK circuit.

[0050] In some embodiments, the output capacitor in the charging / discharging circuit 12 described above can be configured as a variable capacitor. Specifically, please refer to... Figure 3The output capacitor of the low-dropout regulator is a variable capacitor. By adjusting the capacitance value of the variable capacitor, the charging and discharging time of the charging and discharging circuit 12 can be adjusted. When the capacitance value of the variable capacitor increases, the charging and discharging time of the charging and discharging circuit 12 increases accordingly, and when the capacitance value of the variable capacitor decreases, the charging and discharging time of the charging and discharging circuit 12 decreases accordingly. Based on the variable capacitor, the power-off time of the branch where the relay 6 coil is located is controllable, ensuring that when the DC power supply 5 fails, the power-off time of the branch where the coil is located is after the power-off time of the branch where the contacts are located. In some possible implementations, both the output capacitor and the input capacitor of the low-dropout regulator can be configured as variable capacitors. The purpose of setting two / two sets of variable capacitors is to enhance the accuracy of the power-off delay control, thereby ensuring accurate, safe and effective control.

[0051] In this embodiment, the switch module 2 is used to control the on / off state of the branch where the coil is located. The selection of the switch module 2 is not limited. For example, the switch module 2 can be a semiconductor switch, a transformer or converter, or other forms of isolation switch such as optocoupler or electromagnetic.

[0052] In some embodiments, please refer to Figure 3 The switching module 2 includes a semiconductor switch. Specifically, the switching module 2 includes a transistor (BJT), with the collector of the transistor connected to the second end of the coil, the emitter of the transistor grounded, and the base of the transistor connected to a controller. The controller can send a current signal to the base of the transistor to turn it on, thereby turning on the branch containing the coil. The advantage of using a transistor as the switching module 2 in this embodiment is that the transistor control circuit structure is simple, which can reduce costs, and the transistor's conduction is controlled by circuit signals, which can adapt to the delayed power-off of the branch containing the coil. In some specific embodiments, the controller can be integrated with the detection control module 3, that is, the detection control module 3 is also used to send a switching control signal to the switching module 2 to control the on / off state of the switching module 2. Figure 3 As shown, the detection control module 3 is connected to the switch module 2, that is, the detection control module 3 is connected to the base of the transistor, and the detection is used to send a current signal to the transistor to control the transistor's on and off states.

[0053] For further details, please refer to Figure 3 The switching module 2 also includes a protection diode. The positive terminal of the protection diode is connected to the collector of the transistor, and the negative terminal of the protection diode is connected to the output terminal of the buck delay module 1. Based on the above scheme, the protection diode can dissipate excess current and ensure the stability of the transistor's operation.

[0054] It should be understood that the transistor in the above embodiment can be replaced with other types of transistors, such as MOSFETs. Correspondingly, the specific circuit structure of the switching module 2 should also be adjusted accordingly. This embodiment does not impose any restrictions on this.

[0055] In the embodiments of this application, please refer to Figure 4 The detection and control module 3 includes a microcontroller 31 and a power-down detection circuit 32. The power-down detection circuit 32 includes a voltage divider unit and an isolation detection unit. The voltage divider unit is used to divide the DC power supply 5 to obtain a voltage divider signal. The isolation detection unit is used to output a voltage divider feedback signal based on the voltage divider signal. The microcontroller 31 detects the voltage divider feedback signal to determine the power-down status of the DC power supply 5. The purpose of setting up the isolation detection unit is that the microcontroller 31 cannot directly obtain the output signal of the DC power supply 5. Therefore, the output signal of the DC power supply 5 needs to be pre-processed and converted into a signal that the microcontroller 31 can recognize, thereby improving the accuracy of power-down monitoring of the DC power supply 5. In the above circuit structure, the voltage divider unit can be a voltage conversion circuit, a bridge voltage divider circuit, or other forms of voltage divider devices; the isolation detection unit can be an optocoupler relay, a comparator, etc.

[0056] In this embodiment, the high-voltage control module 4 includes an intelligent power module (IPM module). By setting the intelligent power module, the stability and response speed of the on / off control of the branch where the contact is located can be improved.

[0057] The foregoing embodiments have detailed the overall structure and components of a relay protection circuit according to this application. Where there is no conflict, the features of the foregoing embodiments can be combined to form new solutions, and this application does not impose any limitations on this. The operation of the relay protection circuit of this application includes:

[0058] A-Control contact closing process:

[0059] When DC power supply 5 is powered on, wait for the output capacitor of the low dropout regulator to finish charging. Then, the microcontroller 31 outputs a switch control signal to the base of the transistor to make the branch where the coil is located conduct. After the coil is powered on, the control contact closes and the branch where the contact is located conducts.

[0060] B-Active control contact disconnection process:

[0061] The microcontroller 31 outputs a control signal to the intelligent power module to de-energize the branch where the contact is located. Subsequently, the microcontroller 31 outputs a switch control signal to the base of the transistor to disconnect the branch where the coil is located. After the coil is de-energized, the control contact opens.

[0062] C-Passive control contact disconnection process:

[0063] After the microcontroller 31 detects that the DC power supply 5 has lost power, it sends a control signal to the high-voltage control module 4. In response to the control signal, the high-voltage control module 4 disconnects the power supply to the branch where the contact is located. After the DC power supply 5 loses power, the output voltage signal of the step-down delay module 1 slowly drops to 0 over a period of time, so that the power-off time of the branch where the coil is located is after the power-off time of the branch where the contact is located. After the coil is de-energized, the control contact opens.

[0064] This application also provides a control system, please refer to... Figure 5 The system includes a relay protection circuit as described in any of the above embodiments. The system also includes a power controller 7, which controls the power supply 5. When the DC power supply 5 is disconnected, the control system first disconnects the branch containing the contacts of the relay 6, and then disconnects the branch containing the coil of the relay 6 to open the contacts of the relay 6. Based on the above system structure, the control system can directly control the disconnection of the branch containing the contacts of the relay 6 by the detection and control circuit, and also control the disconnection of the branch containing the contacts of the relay 6 by controlling the power supply 5, thus enabling the control system to have multiple relay control modes.

[0065] The control system of this application embodiment can be applied to household appliances, such as dishwashers, disinfection cabinets, refrigerators, and washing machines. In some specific embodiments, the above-mentioned control system can be applied to a door control device. The door control device includes a door control unit and the above-mentioned control system. The door control unit is used to control the power controller 7 to cut off the DC power supply 5 when it detects that the door is open. In a specific application scenario, the door control device is installed in a dishwasher. When the dishwasher is running, the dishwasher door is opened by the user. The door control unit detects that the door is open and controls the power controller 7 to cut off the DC power supply 5. Subsequently, the branch where the contacts of the relay 6 are located is disconnected, and the dishwasher's running motor stops, preventing the dishwasher from causing damage to the user.

[0066] The various embodiments of this application have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical applications, or technological improvements to the embodiments in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A relay protection circuit, characterized by comprising: It includes a step-down delay module (1), a switching module (2), a detection and control module (3), a high-voltage control module (4), a DC power supply (5), and a relay (6). The input terminal of the step-down delay module (1) is connected to the DC power supply (5), the output terminal of the step-down delay module (1) is connected to the first end of the coil of the relay (6), the second end of the coil is connected to the switch module (2), the switch module (2) is used to control the on / off state of the branch where the coil is located, the step-down delay module (1) is used to supply power to the branch where the coil is located, and the step-down delay module (1) includes a step-down circuit (11) and a charging / discharging circuit (12) disposed at the output terminal of the step-down circuit (11). The high-voltage control module (4) is located in the branch where the contacts of the relay (6) are located, and the high-voltage control module (4) is used to control the on / off state of the branch where the contacts are located. The detection and control module (3) is connected to the DC power supply (5) and the high-voltage control module (4) respectively. The detection and control module (3) is used to detect the power failure state of the DC power supply (5) and send a control signal to the high-voltage control module (4).

2. The relay protection circuit according to claim 1, characterized in that, The step-down circuit (11) includes a low-dropout regulator, and the charging / discharging circuit (12) includes an output capacitor; The first terminal of the low-dropout regulator is connected to the DC power supply (5), the second terminal of the low-dropout regulator is grounded, the third terminal of the low-dropout regulator is connected to the first terminal of the coil, an input capacitor is provided between the first terminal and the second terminal of the low-dropout regulator, and an output capacitor is provided between the third terminal and the second terminal of the low-dropout regulator.

3. The relay protection circuit according to claim 2, characterized in that, The output capacitor is a variable capacitor.

4. The relay protection circuit according to claim 1, characterized in that, The detection control module (3) is connected to the switch module (2), and the detection control module (3) is also used to send a switch control signal to the switch module (2) to control the on / off state of the switch module (2).

5. The relay protection circuit according to claim 4, characterized in that, The switching module (2) includes a transistor, the collector of which is connected to the second end of the coil, the emitter of which is grounded, and the base of which is connected to the detection and control module (3).

6. The relay protection circuit according to claim 5, characterized in that, The switching module (2) also includes a protection diode, the positive terminal of which is connected to the collector of the transistor, and the negative terminal of which is connected to the output terminal of the buck delay module (1).

7. The relay protection circuit according to claim 1, characterized in that, The detection control module (3) includes a microcontroller (31) and a power-down detection circuit (32). The power-down detection circuit (32) includes a voltage divider unit and an isolation detection unit. The voltage divider unit is used to divide the DC power supply (5) to obtain a voltage divider signal. The isolation detection unit is used to output a voltage divider feedback signal according to the voltage divider signal. The microcontroller (31) is used to detect the voltage divider feedback signal to determine the power-down status of the DC power supply (5).

8. The relay protection circuit according to claim 1, characterized in that, The high-voltage control module (4) includes an intelligent power module.

9. A control system characterized by, The relay protection circuit includes any one of claims 1-8, and further includes a power controller (7), which is used to control the power-on and power-off of the DC power supply (5). The control system is used to first cut off the branch where the relay (6) contact is located when the DC power supply (5) is cut off, and then cut off the branch where the relay (6) coil is located to disconnect the relay (6) contact.

10. A gating device, characterized by The system includes a gate control unit and a control system as described in claim 9, wherein the gate control unit is used to control the power controller (7) to cut off the DC power supply (5) when the gate is detected to be open.

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