Over-voltage and under-voltage protection circuit and over-voltage and under-voltage protector

Abstract

The utility model provides an overvoltage and undervoltage protection circuit and an overvoltage and undervoltage protector, and relates to the technical field of circuit protection. The overvoltage and undervoltage protection circuit provided by the utility model comprises a main processing module, a key detection module and a nixie tube module, the main processing module is used for acquiring an input voltage signal, a preset overvoltage value and a preset undervoltage value; the key detection module is connected with the main processing module and is used for generating a key signal in response to the switch-on condition of a circuit corresponding to a key on the overvoltage and undervoltage protector and transmitting the key signal to the main processing module, and the main processing module is also used for executing a response action according to the key signal and generating a response action signal; and the main processing module is connected with the nixie tube module and is used for transmitting the response action signal to the nixie tube module, so that the nixie tube module displays the response action signal. The overvoltage and undervoltage protector can solve the problem that an existing overvoltage and undervoltage protector can only carry out overvoltage and undervoltage protection on a circuit in a fixed voltage interval and lacks flexibility.

Description

Technical Field

[0001] This application relates to the technical field of circuit protection, and more particularly to an over / under voltage protection circuit and an over / under voltage protector. Background Technology

[0002] Most self-resetting over / under voltage protectors on the market currently use the traditional LED (Light-Emitting Diode) indicator window to monitor the mains voltage. Whether the LED lights up or not indicates whether the circuit has an overvoltage or undervoltage condition. Users only pay attention to the mains voltage when a fault occurs.

[0003] However, in areas where the power grid is relatively unstable, if the product only protects according to the factory-set voltage value, it lacks flexibility and may cause the contactor to trip repeatedly near the critical value, affecting the user's use. Utility Model Content

[0004] This application provides an over / under voltage protection circuit and an over / under voltage protector to solve the problem that existing over / under voltage protectors can only provide over / under voltage protection for circuits within a fixed voltage range, lacking flexibility.

[0005] In a first aspect, this application provides an over / under voltage protection circuit applied to an over / under voltage protector. The input terminal of the over / under voltage protection circuit is connected to the mains circuit, and the output terminal is connected to a relay to control the relay to trip when the input voltage signal of the over / under voltage protection circuit exceeds the preset overvoltage value or falls below the preset undervoltage value of the over / under voltage protector. The over / under voltage protection circuit includes: a main processing module, a key detection module, and a digital tube module. The main processing module is used to acquire the input voltage signal, the preset overvoltage value, and the preset undervoltage value. The key detection module is connected to the main processing module and is used to generate a key signal in response to the connection status of the circuit corresponding to the key on the over / under voltage protector, and transmit the key signal to the main processing module. The main processing module is also used to execute a response action according to the key signal and generate a response action signal. The key signal includes at least a parameter setting signal, the response action includes at least modifying the preset overvoltage value or the preset undervoltage value, and the response action signal includes at least the modified preset overvoltage value or the preset undervoltage value. The main processing module is connected to the digital tube module and is used to transmit the response action signal to the digital tube module so that the digital tube module displays the response action signal.

[0006] The over / under voltage protection circuit provided in the first aspect allows for the modification of preset overvoltage and undervoltage values ​​when used in areas with unstable grid voltage or when the grid voltage in the area differs from the normal voltage. Specifically, the user presses a button on the over / under voltage protector, triggering the corresponding circuit. This triggers a button detection module that transmits the button signal to the main processing module. Upon receiving the button signal, the main processing module executes a response action, generates a response signal, and transmits it to the digital tube module for display. When the button signal is a parameter setting signal, the main processing module can also modify the preset overvoltage or undervoltage value accordingly, displaying the modified value on the digital tube module for easy viewing by the user to confirm whether the preset overvoltage or undervoltage value has been modified to the target value. Therefore, the above-mentioned over / under voltage protection circuit can make up for the shortcomings of existing over / under voltage protectors, which can only provide over / under voltage protection within a fixed voltage range, improve the flexibility of over / under voltage protectors, and expand the scope of application of over / under voltage protectors.

[0007] In one possible design, the digital tube module includes a digital tube driver chip and a digital tube display unit. The digital tube driver chip is connected to the digital tube display unit and to the main processing module. The digital tube driver chip is used to read the response action signal or the input voltage signal of the over / under voltage protection circuit from the main processing module, and drive the digital tube display unit to display at least one of the following signals: the current voltage value of the power grid, the remaining recovery time of the relay, the internal parameter configuration options of the over / under voltage protector, and the interface configuration.

[0008] With the above solution, users can obtain a variety of signals from the over / under voltage protector from the digital tube module, making it convenient for users to know the power grid status and to set the parameters of the over / under voltage protector.

[0009] In one possible design, the over / under voltage protection circuit also includes a communication module connected to the main processing module. The communication module includes a communication interface for connecting to a communication device, and the communication module is used to realize signal transmission between the communication device and the main processing module.

[0010] By connecting the communication interface to the communication device, signal transmission between the communication device and the main processing module can be realized, thereby enabling signal transmission between the communication device and the over / under voltage protector. This provides the possibility for information sharing and mutual response between the over / under voltage protector and other communication devices.

[0011] In one possible design, the communication module also includes an anti-interference unit connected to the communication interface, used to reduce signal errors between the communication device and the main processing module.

[0012] By setting up an anti-interference module connected to the communication interface, signal errors caused by external factors during signal transmission between the communication device and the main processing module can be reduced, thus reducing signal interference.

[0013] In one possible design, the over / under voltage protection circuit also includes a relay drive module. The relay drive module includes a relay interface for connecting a relay. The relay drive module is connected to the main processing module. The main processing module is also used to control the on / off state of the relay drive module according to the input voltage signal of the over / under voltage protection circuit, so that the relay drive module controls the relay to open or close.

[0014] The above scheme provides a possible way to enable the over / under voltage protector to control the relay to open or close based on the input voltage signal of the over / under voltage protection circuit.

[0015] In one possible design, the over / under voltage protection circuit also includes an output voltage feedback module. The output voltage feedback module is connected to the output terminal of the relay and to the main processing module. It is used to detect the output voltage signal of the relay and transmit the output voltage signal to the main processing module. The main processing module is also used to determine the open / closed state of the relay based on the output voltage signal.

[0016] The above scheme connects the output voltage feedback module to the output terminal of the relay, enabling the detection of the relay's output voltage signal. After obtaining the output voltage signal, the main processing module determines the relay's opening and closing status based on the signal, allowing for further monitoring of the circuit breaker's opening and closing status. This ensures timely identification of whether the relay is operating according to the control logic and provides the possibility of taking further measures if the relay fails to operate correctly according to the control logic.

[0017] In one possible design, the over / under voltage protection circuit also includes a voltage supply module. The input of the voltage supply module is connected to the main grid circuit, and the output is connected to the main processing module and the digital tube module respectively. It is used to convert the main grid voltage into a first output voltage suitable for the main processing module and the digital tube module.

[0018] In one possible design, the voltage supply module includes a first step-down unit and a second step-down unit. The input terminal of the first step-down unit is connected to the mains circuit, and the output terminal is connected to the input terminal of the second step-down circuit. The output terminal of the second step-down unit is connected to the main processing module and the digital tube module, respectively. The first step-down unit is used to convert the mains voltage into a second output voltage, and the second step-down unit is used to convert the second output voltage into a first output voltage. The second output voltage and the first output voltage are voltages of different magnitudes.

[0019] The above scheme, by setting up a first step-down unit and a second step-down unit, enables the grid voltage to be output as a first output voltage and a second output voltage respectively, thereby meeting the usage requirements of different components or modules of the over- and under-voltage protection circuit.

[0020] In one possible design, the first step-down unit includes a surge protection circuit, a rectifier circuit, and a step-down circuit. The input terminal of the surge protection circuit is connected to the mains circuit, the output terminal of the surge protection circuit is connected to the input terminal of the rectifier circuit, and the output terminal of the rectifier circuit is connected to the input terminal of the step-down circuit.

[0021] The surge protection circuit is used to disconnect when the voltage of the mains circuit exceeds a first threshold. The rectifier circuit is used to convert the AC voltage input from the surge protection circuit into DC voltage and output it to the step-down circuit. The step-down circuit is used to step down the DC voltage input from the rectifier circuit to a second output voltage and output it from the output terminal.

[0022] Through the above scheme, the surge protection circuit disconnects when the voltage of the mains circuit exceeds the first threshold, thus protecting the over / under voltage protection circuit and preventing it from being damaged during a surge. The rectifier circuit converts AC voltage into DC voltage, and the step-down circuit further reduces the DC voltage output by the rectifier circuit to a second output voltage. Therefore, the second output voltage is the stepped-down DC voltage, which meets the needs of each module and electrical component in the over / under voltage protection circuit and protects the components in the over / under voltage protection circuit.

[0023] Secondly, this application provides an over / under voltage protector, including the over / under voltage protection circuit and a relay in any of the above embodiments. One output terminal of the over / under voltage protection circuit is connected to the relay, and is used to control the relay to open when the input voltage of the over / under voltage protection circuit exceeds a preset overvoltage value or is lower than a preset undervoltage value, and to control the relay to close after a preset recovery time.

[0024] The advantages of the over / under voltage protectors provided in the second aspect and the various possible designs of the second aspect can be found in the first aspect and the various possible implementations of the first aspect, and will not be repeated here. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the overall structure of an over / under voltage protection circuit provided in an embodiment of this application.

[0026] Figure 2 This is a circuit diagram of a main processing module provided in an embodiment of this application.

[0027] Figure 3 This is a circuit diagram of an input voltage detection module provided in an embodiment of this application.

[0028] Figure 4 This is a schematic diagram of a key detection module provided in an embodiment of this application.

[0029] Figure 5 This is a circuit diagram of a digital tube module provided in an embodiment of this application.

[0030] Figure 6 This is a circuit diagram of a communication module provided in one embodiment of this application.

[0031] Figure 7 This is a circuit diagram of a relay driving module provided in one embodiment of this application.

[0032] Figure 8 This is a circuit diagram of an output voltage feedback module provided in one embodiment of this application.

[0033] Figure 9 This is a circuit diagram of a status indication module provided in one embodiment of this application.

[0034] Figure 10 This is a circuit diagram of a first step-down unit provided in an embodiment of this application.

[0035] Figure 11 This is a circuit diagram of a second step-down unit provided in an embodiment of this application.

[0036] Explanation of reference numerals in the attached diagram: 100, Voltage supply module; 110, First step-down unit; 111, Surge protection circuit; 112, Rectifier circuit; 113, Step-down circuit; 120, Second step-down unit; 200, Main processing module; 210, MCU chip; 220, Peripheral circuit for MCU chip; 300, Input voltage detection module; 400, Key detection module; 410, Key detection circuit; 500, Digital tube module; 510, Digital tube driver chip; 520, Digital tube display unit; 600, Communication module; 610, Communication interface; 620, Anti-interference unit; 700, Relay driver module; 710, Relay interface; 720, H-bridge driver circuit; 800, Output voltage feedback module; 900, Status indicator module; 910, Normal state indicator circuit; 920, Fault indicator circuit; 1000, Communication equipment. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein in the specification of the application is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims and drawings of this application are intended to cover non-exclusive inclusion.

[0039] The term "embodiment" as used herein means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of the phrase "embodiment" in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0040] In this article, 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 mean: A exists, A and B exist simultaneously, or B exists. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0041] Furthermore, the terms "first," "second," etc., in the specification and claims of this application or in the aforementioned drawings are used to distinguish different objects rather than to describe a specific order, and may explicitly or implicitly include one or more of the features.

[0042] In the description of this application, unless otherwise stated, "multiple" means two or more (including two), and similarly, "multiple groups" means two or more (including two groups).

[0043] In the description of this application, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, "connection" or "linking" in mechanical structures can refer to a physical connection, such as a fixed connection, for example, a connection secured by screws, bolts, or other spacers; a physical connection can also be a detachable connection, such as a snap-fit ​​or interlocking connection; a physical connection can also be an integral connection, for example, a connection formed by welding, bonding, or integral molding. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances. In circuit structures, "connection" or "linking" can refer not only to a physical connection but also to an electrical connection or a signal connection. For example, it can be a direct connection, i.e., a physical connection, or an indirect connection through at least one intermediate component, as long as the circuit is connected; it can also refer to the internal connection of two components. Signal connection can refer not only to signal connection through a circuit but also to signal connection through a medium, such as radio waves. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0044] This application provides an over / under voltage protection circuit, which is applied to an over / under voltage protector. The input terminal of the over / under voltage protection circuit is connected to the power grid circuit, and the output terminal is used to connect to a relay to control the relay to trip when the input voltage signal of the over / under voltage protection circuit exceeds the preset overvoltage value or falls below the preset undervoltage value of the over / under voltage protector.

[0045] Figure 1 This is a schematic diagram of the overall structure of an over / under voltage protection circuit provided in an embodiment of this application, as shown below. Figure 1 As shown, the over / under voltage protection circuit includes a main processing module 200, a key detection module 400, and a digital tube module 500.

[0046] The main processing module 200 is used to acquire the input voltage signal, preset overvoltage value and preset undervoltage value of the overvoltage and undervoltage protector.

[0047] The key detection module 400 is connected to the main processing module 200 and is used to generate a key signal in response to the connection status of the circuit corresponding to the key on the over / under voltage protector. The key signal is then transmitted to the main processing module 200. The main processing module 200 is also used to execute a response action based on the key signal and generate a response action signal. The key signal includes at least a parameter setting signal, the response action includes at least modifying the preset overvoltage value or preset undervoltage value, and the response action signal includes at least the modified preset overvoltage value or preset undervoltage value.

[0048] The main processing module 200 is connected to the digital tube module 500 and is used to transmit the response action signal to the digital tube module 500 so that the digital tube module 500 can display the response action signal.

[0049] The input terminal of the over / under voltage protection circuit is connected to the power grid circuit so that it can directly obtain the power grid voltage signal and be powered by the power grid. The power grid voltage signal is the input voltage signal of the over / under voltage protection circuit.

[0050] The preset overvoltage and undervoltage values ​​are stored in the overvoltage and undervoltage protector. The voltage range defined by the preset overvoltage and undervoltage values ​​is a safe voltage range. When the input voltage signal of the overvoltage and undervoltage protection circuit is between the preset undervoltage and preset overvoltage values, the overvoltage and undervoltage protector controls the relay to be in the closed state, and the circuit where the relay main circuit is located is normally connected. When the input voltage signal of the overvoltage and undervoltage protection circuit exceeds the preset overvoltage value or is lower than the preset undervoltage value, the overvoltage and undervoltage protector controls the relay to be opened, and the circuit where the relay main circuit is located is disconnected, thereby protecting the electrical appliances in the circuit where the relay main circuit is located.

[0051] Figure 2 A circuit diagram of a main processing module 200 provided in this application embodiment is shown below. Figure 2 As shown, the main processing module 200 includes an MCU chip 210 and peripheral circuitry 220 configured for the MCU chip. The MCU chip 210 may include functional modules corresponding to the key detection module 400 and the digital tube module 500, which can be specifically configured according to the functions of the main processing module 200. For example, if the main processing module 200 is used to acquire input voltage signals, the MCU chip 210 includes a functional module for acquiring the input voltage signals of the over / under voltage protection circuit, and corresponding chip pins are set on the MCU chip 210 to directly or indirectly acquire the input voltage signals of the over / under voltage protection circuit.

[0052] The peripheral circuit 220 for the MCU chip includes pins related to the functional modules within the MCU chip 210, as well as a ground pin. It also includes a voltage regulator circuit, a RESET circuit, and a debugging circuit for the MCU chip 210. Specifically, the voltage regulator circuit includes a power supply terminal, a ground terminal, and two parallel capacitors connected between the power supply terminal and the ground terminal. The power supply terminal is connected to the pin of the MCU chip 210 that connects to the power supply, the ground terminal is used for grounding, and the two parallel capacitors serve to regulate the voltage.

[0053] In addition, the main processing module 200 can directly or indirectly acquire the input voltage signal, preset overvoltage value, and preset undervoltage value. For example, the MCU chip 210 is provided with a voltage acquisition interface, which is directly connected to the input terminal of the overvoltage and undervoltage protection circuit to acquire the input voltage signal of the overvoltage protection circuit.

[0054] like Figure 1 As shown, in some other examples, the over / under voltage protection circuit also includes an input voltage detection module 300. Figure 3 A circuit diagram of an input voltage detection module provided in an embodiment of this application is shown below. Figure 3 One end of the input voltage detection module 300 is connected to the power grid circuit, specifically to the neutral input terminal L_IN of the power grid circuit, and the other end is connected to the main processing module 200. It is used to collect the power grid voltage signal and transmit the power grid voltage signal to the main processing module 200, thereby completing the acquisition of the power grid voltage signal by the main processing module 200. The power grid voltage signal is the input voltage signal of the over- and under-voltage protection circuit, thus completing the acquisition of the input voltage signal by the main processing module 200.

[0055] For details, please refer to Figure 3 The input voltage detection module 300 includes a diode D3, a voltage divider resistor R3, and a voltage follower U3. The forward input terminal of diode D3 is connected to the mains circuit, and the forward output terminal is connected to the voltage divider resistor R3. The other end of the voltage divider resistor R3 is connected to the input terminal of the voltage follower U3. The output terminal V_ADC of the voltage follower U3 is connected to the main processing module 200. When the main processing module 200 includes an MCU chip 210, the output terminal V_ADC of the voltage follower U3 is connected to the corresponding analog channel pin V_ADC on the MCU chip 210. The diode D3 uses half-wave rectification to convert the AC voltage of the mains grid into DC voltage. After being divided by the voltage divider resistor R3, the voltage is input to the analog channel pin V_ADC of the MCU chip 210 via the voltage follower U3. The voltage follower U3 can improve the accuracy of the voltage acquisition by the MCU chip 210 and reduce the probability of voltage misjudgment.

[0056] Figure 4This is a circuit diagram of a key detection module 400 provided in an embodiment of this application. Figure 4 As shown, in some embodiments, the button detection module 400 includes multiple parallel button detection circuits 410, and each button detection circuit 410 is connected to the main processing module 200. The number of button detection circuits 410 corresponds to the number of adjustment buttons on the over / under voltage protector. For example, if the over / under voltage protector has four buttons, the button detection module 400 includes four parallel button detection circuits 410.

[0057] Each key detection circuit 410 may specifically include a key switch and a resistor connected in series. Multiple key detection circuits 410 each include a first terminal, a second terminal, and a third terminal. The first terminal is connected to voltage VCC, the second terminal is grounded, and the third terminal is connected to the corresponding pin on the MCU chip 210. The key switch is associated with a button on the over / under voltage protector. When a user presses a button, the key switch on the corresponding key detection circuit 410 is activated, and the pin on the MCU chip 210 corresponding to that key detection circuit 410 will acquire a high-level signal. This high-level signal is the key signal. The MCU chip 210 determines which key was pressed based on this key signal, executes a response action based on the key signal, and generates a response action signal.

[0058] For example, the four parallel key detection circuits 410 are respectively a KEY UP circuit for detecting the up key, a KEY DOWN circuit for detecting the down key, a KEY ENT circuit for detecting the confirmation key, and a KEY SET circuit for detecting the return key. When the user presses the confirmation key, the KEY ENT key detection circuit corresponding to the confirmation key is turned on. The pin on the MCU chip 210 connected to the KEY ENT circuit collects a high-level signal, thereby executing the response action of loading the product configuration interface, and transmitting the loaded product configuration interface as a response action signal to the digital tube module 500. After receiving the response action signal, the digital tube module 500 displays the product configuration interface. The user can further select the desired configuration box using the up, down, and confirmation keys. For example, when entering the parameter setting box, the MCU chip 210 obtains the current key signal as the parameter setting signal based on the high level generated by the four key detection circuits 410. This allows the MCU chip to respond to further key actions by the user, modify the preset overvoltage or undervoltage value, and transmit the modified preset overvoltage or undervoltage value as a response signal to the digital tube module 500. The digital tube module 500 then displays the modified overvoltage or undervoltage value of the current device.

[0059] When the MCU chip 210 fails to acquire a high level from any of the key acquisition circuits, the MCU can still drive the digital tube to display at least one of the following signals: current voltage information, remaining recovery time of the relay, internal parameter configuration options of the over / under voltage protector, and interface configuration, so that users can more intuitively monitor the current power grid circuit status.

[0060] The over / under voltage protection circuit provided in the first aspect allows for the modification of preset overvoltage and undervoltage values ​​when the over / under voltage protector is used in areas with unstable grid voltage or when the grid voltage in the area where the over / under voltage protector is used differs from the normal voltage. Specifically, the user presses a button on the over / under voltage protector, triggering the corresponding circuit. This causes the button detection module 400 to generate a button signal, which is then transmitted to the main processing module 200. Upon receiving the button signal, the main processing module 200 executes a response action and generates a response action signal, which is then transmitted to the digital tube module 500 for display. When the button signal is a parameter setting signal, the main processing module 200 can also modify the preset overvoltage or preset undervoltage value in response to the parameter setting signal, displaying the modified value on the digital tube module 500 for easy viewing by the user to see whether the preset overvoltage or preset undervoltage value has been modified to the target value. Therefore, the above-mentioned over / under voltage protection circuit can make up for the shortcomings of existing over / under voltage protectors, which can only provide over / under voltage protection within a fixed voltage range, improve the flexibility of over / under voltage protectors, and expand the scope of application of over / under voltage protectors.

[0061] Figure 5 This is a circuit diagram of a digital tube module 500 provided in an embodiment of this application. Figure 5 As shown, in one possible design, the digital tube module 500 includes a digital tube driver chip 510 and a digital tube display unit 520. The digital tube driver chip 510 is connected to the digital tube display unit 520 and is also connected to the main processing module 200. The digital tube driver chip 510 is used to read the response action signal or the input voltage signal of the over / under voltage protection circuit from the main processing module 200, and drive the digital tube display unit 520 to display at least one of the following signals: the current voltage value of the power grid, the remaining recovery time of the relay, the internal parameter configuration options of the over / under voltage protector, and the interface configuration.

[0062] The digital tube driver chip 510 is connected to the main processing module 200 and is used to obtain response action signals or input voltage signals of the over / under voltage protection circuit from the main processing module 200. For example, the digital tube driver chip 510 is provided with a clock pin CLK and a digital input / output pin DIO. The MCU chip 210 is also provided with a clock pin CLK and a digital input / output pin DIO. The clock pin CLK on the MCU chip 210 of the digital tube driver chip 510 is connected to the clock pin CLK on the MCU chip 210, and the digital input / output pin DIO on the digital tube driver chip 510 is connected to the digital input / output pin DIO on the MCU chip 210, thereby enabling the digital tube driver chip 510 to read response action signals or input voltage signals of the over / under voltage protection circuit from the main processing module 200.

[0063] The digital tube display unit 520 can be configured as a four-digit common cathode digital tube. The four-digit common cathode digital tube corresponds to the display screen on the over / under voltage protector, so that the content displayed on the digital tube is displayed to the user through the display screen on the over / under voltage protector.

[0064] The digital tube driver chip 510 is mainly used to control the display content of the digital tube display unit 520. The digital tube driver chip 510 has multiple pins, which are connected to corresponding pins of the digital tube display unit 520. For example, the digital tube driver chip 510 has four control pins and eight digital pins. The four control pins are denoted as COM1, COM2, COM3, and COM4, ​​and the eight digital pins are denoted as A, B, C, D, E, F, G, and DP. The four-digit common cathode digital tube also has four control pins and eight digital pins. The four control pins of the digital tube driver chip 510 are connected to the four control pins of the four-digit common cathode digital tube, and the eight digital pins of the digital tube driver chip 510 are connected to the eight digital pins of the four-digit common cathode digital tube, thereby enabling the digital tube driver chip 510 to control the display content of the digital tube display unit 520.

[0065] Through the connection between the digital tube driver chip 510, the main processing module 200, and the digital tube display unit 520, the digital tube driver chip 510 can ultimately read the response action signal or the input voltage signal of the over / under voltage protection circuit from the main processing module 200, and drive the digital tube display unit 520 to display at least one signal from the current voltage value of the power grid, the remaining recovery time of the relay, the internal parameter configuration options of the over / under voltage protector, and the interface configuration. In this solution, the user can obtain a variety of signals from the over / under voltage protector from the digital tube module 500, which facilitates the user to know the power grid status and to set the parameters of the over / under voltage protector.

[0066] In addition, the digital tube driver chip 510 is also equipped with conventional pins such as power supply pin VCC and ground pin GND. Multiple parallel capacitors can also be connected between the clock pin CLK and the digital input / output pin DIO on the digital tube driver chip 510 to achieve voltage regulation. This application will not elaborate on this further.

[0067] Please continue to refer to Figure 1 In one possible design, the over / under voltage protection circuit also includes a communication module 600, which is connected to the main processing module 200. The communication module 600 includes a communication interface 610, which is used to connect to the communication device 1000. The communication module 600 is used to realize signal transmission between the communication device 1000 and the main processing module 200.

[0068] Please refer to Figure 6 , Figure 6 This is a circuit diagram of a communication module 600 provided in one embodiment of this application. Exemplarily, the communication module 600 includes a transceiver U6, which has at least one transmit data pin TX, one receive data pin RX, and one read data pin REDE. The MCU chip 210 also has corresponding transmit data pin TX, receive data pin RX, and read data pin REDE. The pins on the transceiver U6 are connected to the corresponding pins on the MCU chip 210, enabling signal transmission between the communication module 600 and the main processing module 200, thereby achieving communication between the communication module 600 and the main processing module 200.

[0069] More specifically, the transceiver U6 is also equipped with a communication interface 610, which consists of communication pin A and communication pin B on the transceiver U6. The communication interface 610 can be a communication conversion interface, which can be connected to a gateway, or to products such as computers and circuit breakers, thereby realizing communication between the connected communication device 1000 and the communication module 600.

[0070] After establishing communication between the communication module 600 and the main processing module 200, as well as between the connected communication device 1000 and the communication module 600, it can be concluded that the over / under voltage protection circuit in this application, by setting up the communication module 600, enables communication between the main processing module 200 and the communication device. Based on this, the over / under voltage protector can synchronize information such as the current grid voltage, the product's opening and closing status, and other information with the connected communication device 1000. Users can also obtain or modify the configuration information of the connected communication device 1000 by issuing commands to the over / under voltage protector, or vice versa. This further increases the flexibility and functional versatility of the over / under voltage protector.

[0071] Understandably, when the communication module 600 includes a transceiver U6, the transceiver U6 is also connected to a power supply pin VDD and a ground pin GND. At the same time, multiple capacitors can be connected in parallel between the power supply pin VDD and the ground pin GND to achieve voltage regulation.

[0072] Optionally, the communication module 600 also includes an anti-interference unit 620, which is connected to the communication interface 610 and is used to reduce signal errors between the communication device and the main processing module 200.

[0073] For example, the anti-interference unit 620 includes a diode, specifically, the diode may be a bidirectional transient diode (TVS).

[0074] Taking the communication interface 610, which consists of communication pin A and communication pin B on the transceiver, as an example, one end of each of the communication pins A and B is led out for grounding. The anti-interference unit 620 includes three bidirectional transient diodes (TVS), denoted as D61, D62, and D63, respectively. The three bidirectional transient diodes are connected between communication pin A and communication pin B, between communication pin A and the ground terminal led out from communication pin A, and between communication pin B and the ground terminal led out from communication pin B.

[0075] By setting up the anti-interference unit 620, surge protection of the communication interface 610 can be achieved, signal interference can be reduced, and signal errors caused by external factors can be reduced when the communication device transmits signals between the main processing module 200.

[0076] like Figure 1 As shown, in one possible design, the over / under voltage protection circuit also includes a relay drive module 700. Figure 7 This is a circuit diagram of a relay driving module provided in one embodiment of this application. Figure 7 As shown, the relay drive module 700 includes a relay interface 710 for connecting a relay. The relay drive module 700 is connected to the main processing module 200. The main processing module 200 is also used to control the on / off state of the relay drive module 700 according to the input voltage signal of the over / under voltage protection circuit, so that the relay drive module 700 controls the relay to open or close.

[0077] In a specific example, the relay drive module 700 includes an H-bridge drive circuit 720. The H-bridge drive circuit 720 includes three input pins and two output pins. One input pin is a power supply pin used to connect to a power source. The other two input pins are denoted as drive1 and drive2, respectively. Input pins drive1 and drive2 are connected to the main processing module 200. The two output pins are denoted as the first output pin and the second output pin, respectively. The first output pin and the second output pin together form an output interface used to connect to the relay. Input pins drive1 and drive2 are used to receive high and low levels output by the main processing module 200, thereby controlling the on / off state of the H-bridge drive circuit 720, and further controlling the output levels of the two output pins, ultimately achieving the purpose of controlling the relay to open and close.

[0078] The H-bridge driver circuit 720 specifically includes six transistors, denoted as Q1, Q2, Q3, Q4, Q5, and Q6. Q1 and Q2 are PNP transistors, while Q3, Q4, Q5, and Q6 are NPN transistors. The emitter of transistor Q1 is connected to the emitter of transistor Q2, and a power supply pin is led out between the emitters of Q1 and Q2. The base of transistor Q1 is connected to the collector of Q3, the collector of transistor Q1 is connected to the collector of transistor Q5, the base of transistor Q2 is connected to the collector of transistor Q4, and the collector of transistor Q2 is connected to the collector of transistor Q6. The collectors of transistors Q1 and Q2 are connected. The base of transistor Q3 is connected to the input pin drive1. The emitter of transistor Q3 is connected to the base of transistor Q6. The base of transistor Q4 is connected to the input pin drive2. The emitter of transistor Q4 is connected to the base of transistor Q5. The emitter of transistor Q5 is connected to the emitter of transistor Q6. A ground terminal is connected between the emitters of transistor Q5 and Q6 for grounding. The first output pin is connected between the collector of transistor Q1 and the collector of transistor Q5. The second output pin is connected between the collector of transistor Q2 and the collector of transistor Q6.

[0079] By employing the H-bridge drive circuit 720 described above, when the main processing module 200 inputs a high level to input pin drive1 and a low level to input pin drive2, Q3, Q6, and Q1 are turned on, the first output pin outputs a high level, and the second output pin outputs a low level, thereby controlling the relay to close. When the main processing module 200 inputs a high level to input pin drive2 and a low level to input pin drive1, Q2, Q5, and Q4 are turned on, the second output pin outputs a high level, and the first output pin outputs a low level, thereby controlling the relay to close.

[0080] The relay drive module with the above structure provides a possible implementation method for the over / under voltage protector to control the relay to open or close based on the input voltage signal of the over / under voltage protection circuit, and the cost is low.

[0081] Optionally, a bidirectional transient diode ZD2 is connected between the first output pin and the second output pin of the H-bridge drive circuit 720 to protect the relay and prevent damage to the relay caused by current surges.

[0082] Optionally, a ground terminal can be led out between the emitters of transistors Q1 and Q2 in the H-bridge driver circuit 720, and a capacitor can be connected to the ground terminal for energy storage and voltage regulation. Specifically, the capacitor can be an electrolytic capacitor E1, with its positive terminal connected between the emitters of transistors Q1 and Q2, and its negative terminal connected to the ground terminal.

[0083] In addition, diode D4 can be connected to the power supply pin of the H-bridge driver circuit 720. The positive terminal of diode D4 is connected to the power supply pin, and the negative terminal is connected between the emitter of transistor Q1 and the emitter of transistor Q2, which serves as rectification and filtering.

[0084] Furthermore, in the H-bridge drive circuit 720 described above, a voltage divider resistor can be connected between any two transistors according to the voltage requirements of the transistors, so as to control the voltage of one or more transistors.

[0085] Considering that under certain fault conditions, the relay may fail to reliably open or close under the control of the relay drive module 700, causing losses to the user, such as... Figure 1 As shown, in one possible design, the over / under voltage protection circuit also includes an output voltage feedback module 800. The output voltage feedback module 800 is connected to the output terminal of the relay and to the main processing module 200. It is used to detect the output voltage signal of the relay and transmit the output voltage signal to the main processing module 200. The main processing module 200 is also used to determine the opening and closing status of the relay based on the output voltage signal.

[0086] Specifically, Figure 8 A circuit diagram of an output voltage feedback module provided in one embodiment of this application is shown below. Figure 8In some embodiments, the output voltage feedback module 800 includes two input terminals and one output terminal. The two input terminals are denoted as the first input terminal L_OUT and the second input terminal N_IN, respectively. The output terminal is denoted as V_FEEDBACK. The first input terminal L_OUT is connected to the live wire output terminal of the relay, the second input terminal N_IN is connected to the neutral wire input terminal of the relay, and the output terminal V_FEEDBACK is connected to the V_FEEDBACK pin of the main processing module 200. An optocoupler U8 is connected between the two input terminals and the output terminal. The first input terminal L_OUT is connected to the positive terminal of the primary side of the optocoupler U8, the second input terminal N_IN is connected to the negative terminal of the primary side of the optocoupler U8, the collector of the secondary side of the optocoupler U8 is connected to the output terminal V_FEEDBACK, and the emitter of the secondary side of the optocoupler U8 is grounded.

[0087] The output voltage feedback module 800 can detect the voltage at the output terminal of the relay and connect to the main processing module 200 through the output terminal V_FEEDBACK, thereby transmitting the voltage signal at the output terminal of the relay to the main processing module 200. After receiving the output voltage signal, the main processing module 200 determines the opening and closing status of the relay based on the output voltage signal, and can further monitor the opening and closing status of the circuit breaker, so as to know in a timely manner whether the relay opens and closes according to the control logic, and provides the possibility of taking further measures if the relay does not open and close correctly according to the control logic.

[0088] For example, if the main processing module 200 determines that the relay has not opened according to the control logic, the main processing module 200 can again control the relay to open by controlling the circuit connection of the relay drive module 700. The output voltage feedback module 800 further feeds back the detected output voltage signal to the main processing module 200. If the main processing module 200 still determines that the relay has not opened according to the control logic, it indicates that the over / under voltage protector has malfunctioned. The main processing module 200 can further control the over / under voltage protector to issue a fault warning.

[0089] For example, such as Figure 1 As shown, the over / under voltage protection circuit also includes a status indication module 900. Figure 9 A circuit diagram of a status indication module provided in one embodiment of this application is shown below. Figure 9The status indication module 900 includes a normal state indication circuit 910 and a fault indication circuit 920. One pin of the fault indication circuit 920 is connected to the power supply, and the other pin is connected to the alarm pin ALARM of the main processing module 200. A first light-emitting diode ALARM1 and a resistor are connected between the two pins of the fault indication circuit 920. One pin of the normal state indication circuit 910 is connected to the power supply, and the other pin is connected to the power supply pin POWER of the main processing module 200. A second light-emitting diode PWR1 and a resistor are connected between the two pins of the normal state indication circuit. When the main processing module 200 determines that the over / under voltage protector has malfunctioned based on the output voltage signal, it outputs a high level to the fault indication circuit through the alarm pin ALARM and a low level to the normal operation indication circuit through the power supply pin POWER. At this time, the first LED ALARM1 illuminates, while the second LED PWR1 does not illuminate, indicating to the user that the over / under voltage protector is in a faulty state. Conversely, when the main processing module 200 determines that the over / under voltage protector is not malfunctioning based on the output voltage signal, it outputs a low level to the fault indication circuit 920 through the alarm pin ALARM and a high level to the normal operation indication circuit 910 through the power supply pin POWER. At this time, the first LED ALARM1 does not illuminate, while the second LED PWR1 illuminates, indicating to the user that the over / under voltage protector is in normal operating condition.

[0090] Please refer to Figure 1 In addition to the above-mentioned functional modules, the over / under voltage protection circuit in this application also includes a voltage supply module 100. The input terminal of the voltage supply module 100 is connected to the power grid circuit, and the output terminal is connected to the main processing module 200 and the digital tube module 500 respectively, for converting the power grid voltage into a first output voltage suitable for use by the main processing module 200 and the digital tube module 500.

[0091] The first output voltage can be a 3.3V DC voltage, which can meet the requirements of the main processing module 200 and the digital tube module 500. In the case that the over- and under-voltage protection circuit includes the key detection module 400, the digital tube module 500, the status indicator module, the input voltage detection module 300, and the output voltage feedback module, the output terminal of the voltage supply module 100 is also connected to the key detection module 400, the digital tube module 500, the communication module 600, the status indicator module 900, the input voltage detection module 300, and the output voltage feedback module 800 respectively to provide them with the first output voltage.

[0092] Considering that different modules or electronic components in the over / under voltage protection circuit may have different applicable voltage values ​​or types, for example, the relay drive module 700 requires a DC voltage of 16V, which is different from the voltage requirements of the main processing module 200 and the digital tube module 500, the voltage supply module 100 may include multiple output terminals, each of which can output a different voltage. Here, different voltages refer to different voltage magnitudes or different types of voltage in terms of DC or AC.

[0093] For example, refer to Figure 1 In one possible design, the voltage supply module 100 includes a first step-down unit 110 and a second step-down unit 120. The input terminal of the first step-down unit 110 is connected to the mains circuit, and the output terminal is connected to the input terminal of the second step-down circuit 113. The output terminal of the second step-down unit 120 is connected to the main processing module 200 and the digital tube module 500, respectively. The first step-down unit 110 is used to convert the mains voltage into a second output voltage, and the second step-down unit 120 is used to convert the second output voltage into a first output voltage. The second output voltage and the first output voltage are voltages of different magnitudes.

[0094] The second buck unit 120 further bucks the second output voltage output by the first buck unit 110 based on the first buck unit 110, thereby outputting a first output voltage that is different from the second output voltage.

[0095] As can be seen, by setting the first step-down unit 110 and the second step-down unit 120, the grid voltage can be output as the first output voltage and the second output voltage respectively, thereby meeting the usage requirements of different components or modules of the over- and under-voltage protection circuit.

[0096] For example, the second output voltage is 16V DC voltage, and the first output voltage is 3.3V DC voltage.

[0097] The following is a schematic description of the possible structures of the first step-down unit 110 and the second step-down unit 120.

[0098] Figure 10 This is a circuit diagram of a first step-down unit 110 provided in one embodiment of this application. Figure 10 As shown, in one possible design, the first step-down unit 110 includes a surge protection circuit 111, a rectifier circuit 112, and a step-down circuit 113. The input terminal of the surge protection circuit 111 is connected to the power grid circuit, the output terminal of the surge protection circuit 111 is connected to the input terminal of the rectifier circuit 112, and the output terminal of the rectifier circuit 112 is connected to the input terminal of the step-down circuit 113.

[0099] Surge protection circuit 111 is used to disconnect when the voltage of the mains circuit exceeds a first threshold. Rectifier circuit 112 is used to convert the AC voltage input from surge protection circuit 111 into DC voltage and output it to buck circuit 113. Buck circuit 113 is used to step down the DC voltage input from rectifier circuit 112 to a second output voltage and output it from the output terminal.

[0100] Specifically, in some embodiments, one input terminal of the surge protection circuit 111 is the live wire input terminal L_IN, and the other input terminal is the neutral wire input terminal N_IN. The live wire input terminal L_IN is connected to the live wire of the power grid circuit, and the neutral wire input terminal N_IN is connected to the neutral wire of the power grid circuit. A varistor is connected between the live wire input terminal L_IN and the neutral wire input terminal N_IN. When the voltage between the live wire input terminal L_IN and the neutral wire input terminal N_IN exceeds a certain preset value, the resistance of the varistor increases sharply, thereby preventing the over / under voltage protection circuit from generating a large current and burning out the components in the circuit, thus realizing the surge protection function of the over / under voltage protection circuit. It can be understood that multiple varistors can be connected in parallel between the live wire input terminal L_IN and the neutral wire input terminal N_IN to realize the multiple surge protection function of the over / under voltage protection circuit. At the same time, one or more resistors with fixed resistance values ​​or adjustable resistors can be connected in series in the circuit where each varistor is located to realize voltage division.

[0101] The rectifier circuit 112 includes a positive input terminal, a negative input terminal, a positive output terminal, and a negative output terminal.

[0102] In some embodiments, the rectifier circuit 112 further includes a bridge rectifier circuit 112, which can be implemented by connecting a bridge rectifier, as will not be described in detail in this application embodiment. The bridge rectifier circuit 112 converts the AC voltage between the positive and negative input terminals into a DC voltage between the positive and negative output terminals, thus achieving the purpose of converting AC to DC.

[0103] In some embodiments, the rectifier circuit 112 may further include a capacitive rectifier circuit 112, that is, the rectifier circuit 112 includes multiple electrolytic capacitors connected in parallel between the positive input terminal and the negative input terminal of the rectifier circuit 112. The positive terminal of the electrolytic capacitor is connected to the positive input terminal of the rectifier circuit 112, and the negative terminal of the electrolytic capacitor is connected to the negative input terminal of the rectifier circuit 112. Ultimately, the AC voltage between the positive and negative input terminals is transformed into a DC voltage between the positive and negative output terminals, achieving the purpose of AC to DC conversion. It is understood that an inductor can also be connected in series in the circuit containing any of the electrolytic capacitors to further achieve rectification and filtering.

[0104] Furthermore, in some embodiments, the rectifier circuit 112 may simultaneously include the bridge rectifier circuit 112 and the capacitor rectifier circuit 112 described above, achieving the effects of rectification, filtering, and voltage regulation. For specific structures, please refer to [reference needed]. Figure 10 .

[0105] In some embodiments, the step-down circuit 113 includes a power switch chip U10 and peripheral circuitry adapted to the power switch chip U10. The input terminal of the step-down circuit 113 is connected to the positive output terminal of the rectifier circuit 112, and the output terminal of the step-down circuit 113 is connected to the input terminal of the second step-down circuit 113. The power switch chip U10 and its adapted peripheral circuitry cooperate to achieve the purpose of stepping down the rectified mains voltage to a second output voltage.

[0106] Specifically, the power switch chip U10 can use a non-isolated buck circuit 113. Compared with the resistor-capacitor buck circuit 113, the non-isolated buck circuit 113 has a stronger current output capability. In addition, the magnetic components used in the non-isolated buck circuit 113 are smaller, more energy-efficient, have fewer components, and have a lower total bill of materials cost.

[0107] The first step-down unit 110 in the above structure disconnects when the voltage of the mains circuit exceeds a first threshold via the surge protection circuit 111, thus protecting the over / under voltage protection circuit and preventing it from being damaged during a surge. The rectifier circuit 112 converts AC voltage into DC voltage, and the step-down circuit 113 further reduces the DC voltage output by the rectifier circuit 112 to a second output voltage. Therefore, the second output voltage is the stepped-down DC voltage, which meets the needs of each module and electrical component in the over / under voltage protection circuit and protects the components in the over / under voltage protection circuit.

[0108] In some embodiments, the second buck unit 120 adopts an LDO (Low Dropout Regulator) voltage drop circuit. Specifically, the second buck unit 120 includes an input terminal and an output terminal. The input terminal of the second buck unit 120 is connected to the output terminal of the first buck unit 110. The output terminal of the second buck unit 120 is used to connect to at least the main processing module 200, the digital tube module 500, and the key detection module 400 to provide the above modules with a first output voltage that meets the requirements.

[0109] Figure 11 This is a circuit diagram of a second step-down unit 120 provided in one embodiment of this application. Figure 11As shown, when the second step-down unit 120 uses an LDO voltage drop circuit, the second step-down unit 120 specifically includes a low-dropout linear regulator U4 and peripheral circuitry adapted to the low-dropout linear regulator U4. The low-dropout linear regulator U4 includes a voltage input interface VIN, a voltage output interface VO, and a ground interface GND. The peripheral circuitry adapted to the low-dropout linear regulator includes a voltage regulation circuit composed of multiple capacitors connected in parallel, etc., which will not be described in detail in this embodiment of the application. The input voltage of the second step-down unit 120 is further reduced to the first output voltage by the low-dropout linear regulator to at least meet the needs of the main processing module 200, the digital tube module 500, and the key detection module 400.

[0110] It is understandable that diodes and resistors can be connected in series at the input of the second step-down unit 120 to achieve filtering and voltage division respectively.

[0111] In summary, when the over / under voltage protection circuit provided in this application is used in areas with unstable mains voltage or when the mains voltage in the area where the over / under voltage protector is used differs from the normal voltage, the preset overvoltage and preset undervoltage values ​​of the over / under voltage protector can be changed as needed using buttons. The changed preset overvoltage or preset undervoltage values ​​can be displayed on the digital tube module 500, allowing users to intuitively see whether the preset overvoltage or preset undervoltage values ​​have been modified to the target values. Therefore, the above-mentioned over / under voltage protection circuit can overcome the deficiency of existing over / under voltage protectors, which can only provide over / under voltage protection within a fixed voltage range, improving the flexibility of the over / under voltage protector and expanding its applicability.

[0112] This application also provides an over / under voltage protector, including the over / under voltage protection circuit and a relay in any of the above embodiments. One output terminal of the over / under voltage protection circuit is connected to the relay, and is used to control the relay to open when the input voltage of the over / under voltage protection circuit exceeds a preset overvoltage value or is lower than a preset undervoltage value, and to control the relay to close after a preset recovery time.

[0113] Since the over / under voltage protection circuit in any of the above embodiments is used, the over / under voltage protector in this embodiment of the application has the various beneficial effects brought about by the over / under voltage protection circuit, which will not be described again in this embodiment of the application.

Claims

1. An over / under voltage protection circuit, applied to an over / under voltage protector, wherein the input terminal of the over / under voltage protection circuit is connected to the mains circuit, and the output terminal is connected to a relay to control the relay to trip when the input voltage signal of the over / under voltage protection circuit exceeds a preset overvoltage value or falls below a preset undervoltage value of the over / under voltage protector, characterized in that, The over / under voltage protection circuit includes a main processing module, a key detection module, and a digital tube module; The main processing module is used to acquire the input voltage signal, the preset overvoltage value, and the preset undervoltage value; The key detection module is connected to the main processing module and is used to generate a key signal in response to the connection status of the circuit corresponding to the key on the over / under voltage protector, and transmit the key signal to the main processing module. The main processing module is also used to execute a response action according to the key signal and generate a response action signal. The key signal includes at least a parameter setting signal, the response action includes at least modifying the preset overvoltage value or the preset undervoltage value, and the response action signal includes at least the modified preset overvoltage value or preset undervoltage value. The main processing module is connected to the digital tube module and is used to transmit the response action signal to the digital tube module so that the digital tube module displays the response action signal.

2. The over / under voltage protection circuit according to claim 1, characterized in that, The digital tube module includes a digital tube driver chip and a digital tube display unit. The digital tube driver chip is connected to the digital tube display unit and to the main processing module. It is used to read the response action signal or the current voltage signal of the power grid from the main processing module, and drive the digital tube display unit to display at least one of the following signals: the current voltage value of the power grid, the remaining recovery time of the relay, the internal parameter configuration options of the over / under voltage protector, and the interface configuration.

3. The over / under voltage protection circuit according to claim 1, characterized in that, The circuit also includes a communication module connected to the main processing module. The communication module includes a communication interface for connecting to a communication device. The communication module is used to realize signal transmission between the communication device and the main processing module.

4. The over / under voltage protection circuit according to claim 3, characterized in that, The communication module further includes an anti-interference unit, which is connected to the communication interface and is used to reduce the signal error between the communication device and the main processing module.

5. The over / under voltage protection circuit according to claim 1, characterized in that, The circuit also includes a relay drive module, which includes a relay interface for connecting a relay. The relay drive module is connected to the main processing module, and the main processing module is also used to control the connection status of the relay drive module according to the input voltage signal of the over / under voltage protection circuit, so that the relay drive module controls the relay to open or close.

6. The over / under voltage protection circuit according to claim 1, characterized in that, The circuit also includes an output voltage feedback module, which is connected to the output circuit of the relay and to the main processing module. The output voltage feedback module is used to detect the output voltage signal of the relay and transmit the output voltage signal to the main processing module. The main processing module is also used to determine the opening and closing status of the relay based on the output voltage signal of the relay.

7. The over / under voltage protection circuit according to any one of claims 1-6, characterized in that, The circuit also includes a voltage supply module, the input of which is connected to the power grid circuit, and the output of which is connected to the main processing module and the digital tube module respectively, for converting the power grid voltage into a first output voltage suitable for the main processing module and the digital tube module.

8. The over / under voltage protection circuit according to claim 7, characterized in that, The voltage supply module includes a first step-down unit and a second step-down unit. The input terminal of the first step-down unit is connected to the power grid circuit, and the output terminal is connected to the input terminal of the second step-down unit. The output terminal of the second step-down unit is connected to the main processing module and the digital tube module, respectively. The first step-down unit is used to convert the power grid voltage into a second output voltage, and the second step-down unit is used to convert the second output voltage into a first output voltage. The second output voltage and the first output voltage are voltages of different magnitudes.

9. The over / under voltage protection circuit according to claim 8, characterized in that, The first step-down unit includes a surge protection circuit, a rectifier circuit, and a step-down circuit. The input terminal of the surge protection circuit is connected to the power grid circuit, the output terminal of the surge protection circuit is connected to the input terminal of the rectifier circuit, and the output terminal of the rectifier circuit is connected to the input terminal of the step-down circuit. The surge protection circuit is used to disconnect when the voltage of the power grid circuit exceeds a first threshold. The rectifier circuit is used to convert the AC voltage input from the surge protection circuit into DC voltage and output it to the step-down circuit. The step-down circuit is used to step down the DC voltage input from the rectifier circuit to a second output voltage and output it from the output terminal.

10. An over / under voltage protector, characterized in that, The circuit includes the over / under voltage protection circuit and relay as described in any one of claims 1 to 9, wherein one output terminal of the over / under voltage protection circuit is connected to the relay for controlling the relay to open when the input voltage of the over / under voltage protection circuit exceeds a preset overvoltage value or falls below a preset undervoltage value, and controlling the relay to close after a preset recovery time.

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