Relay control circuit and control method

Abstract

The present application relates to the technical field of relay driving. Provided are a relay control circuit and a control method, which are used for ameliorating the technical problem of electric arcs and electromagnetic interference being prone to be generated when a relay is turned on and off and thereby shortening the service life of the relay and impacting the reliability of a circuit. The relay control circuit comprises: an isolation voltage threshold collection module, which is used for collecting the voltage value of a leading phase of a load phase connected to a relay, and outputting an enable signal when the collected voltage value reaches a target alternating-current voltage threshold, wherein the enable signal is a control signal for allowing the relay to perform zero-crossing turning-on / off; a determination module, which is used for outputting a driving signal upon receiving an on-off signal and the enable signal; and a relay driving module, which is used for controlling the turning-on / off of the relay on the basis of the driving signal. The present application can prevent the generation of electric arcs when a relay acts, thereby effectively prolonging the service life of the relay, reducing electromagnetic interference, and ameliorating the impact of the electromagnetic interference on a circuit.

Description

Relay control circuit and control method

[0001] The present disclosure claims priority to the Chinese patent application No. CN202410690868.2, filed on May 30, 2024, and entitled "Relay control circuit and control method", the entire content of which is incorporated herein by reference. TECHNICAL FIELD

[0002] The present application relates to the technical field of relay driving, in particular to a relay control circuit and control method. BACKGROUND

[0003] An electromagnetic relay is a mechanical electromagnetic switch. When the electromagnetic relay is started, the current passing through the coil generates a magnetic field, which makes the armature contact or break at the contact position. This process is based on mechanical principles and takes a certain amount of time to complete, which is called the action time.

[0004] In the related art, the relay is equipped with a zero-crossing detection circuit to control the turn-on or turn-off operation of the relay at the zero-crossing point of the alternating voltage waveform, so as to avoid excessive impact on the relay during the current peak period, thereby prolonging the service life of the relay. However, due to the certain response delay of the switching or turn-on operation of the relay itself, the contact is not always at the zero-crossing point of the voltage waveform when the operation is performed. In this case, the contact contact or break may cause arc discharge between the contacts due to the sudden change of the current, accelerate the wear of the relay, and shorten the service life of the relay. In addition, the sudden change of the current may also cause electromagnetic interference (EMI) and propagate in the circuit, affecting the normal work of the components in the circuit and reducing the reliability of the circuit. SUMMARY

[0005] Embodiments of the present application provide a relay control circuit and control method to improve the technical problem that the relay is prone to arc and electromagnetic interference when turned on and off, thereby shortening the service life of the relay and affecting the reliability of the circuit.

[0006] In a first aspect, embodiments of the present application provide a relay control circuit, comprising:

[0007] An isolation voltage threshold acquisition module configured to acquire a voltage value of a leading phase of a load phase connected to the relay and output an enable signal;

[0008] a judgment module configured to receive the on-off signal and the enable signal, judge the enable signal, output a driving signal if the enable signal is a valid enable signal, and output a maintaining signal if the enable signal is an invalid enable signal, wherein the valid enable signal is an enable signal when the voltage value of the leading phase of the load phase reaches a target AC voltage threshold, and the invalid enable signal is an enable signal when the voltage value of the leading phase of the load phase does not reach the target AC voltage threshold.

[0009] a relay driving module configured to control the on-off of the relay based on the driving signal and control the action of the relay based on the maintaining signal.

[0010] In some embodiments of the present application, the target AC voltage threshold is:

[0011] wherein T R represents the action time of the on-off of the relay, V ac represents the effective value of the AC voltage, and V th represents the target AC voltage threshold.

[0012] In some embodiments of the present application, the relay control circuit further comprises an A-phase line, a B-phase line, and a C-phase line, the load phase is an AB phase of an AC power supply, the leading phase is a CA phase of the AC power supply, the moving contact and the stationary contact of the relay are connected to the A-phase line and the B-phase line respectively, the input end of the isolated voltage threshold acquisition module is connected to the A-phase line and the C-phase line respectively, and the output end of the isolated voltage threshold is connected to the judgment module.

[0013] In some embodiments of the present application, the isolated voltage threshold acquisition module comprises an acquisition circuit and a buffer circuit, the input end of the acquisition circuit is connected to the buffer circuit, the acquisition circuit is configured to acquire the voltage value of the leading phase of the load phase connected to the relay and output a voltage signal, the buffer circuit is configured to receive the voltage signal and process the voltage signal into an enable signal, and the output end of the buffer circuit is connected to the judgment module to output the enable signal to the judgment module.

[0014] In some embodiments of the present application, the acquisition circuit comprises a bidirectional optocoupler U3 and a filter circuit RC3, the input end of the bidirectional optocoupler U3 is connected to the A-phase line and the C-phase line, the output end of the bidirectional optocoupler U3 is connected to the filter circuit RC3, and the output end of the filter circuit RC3 is connected to the buffer circuit.

[0015] In some embodiments of the present application, the turn-on voltage of the bidirectional optocoupler U3 is equal to the target AC voltage threshold.

[0016] In some embodiments of the present application, the filter circuit RC3 comprises a resistor R12 and a capacitor C3, an input end of the resistor R12 is connected with an output end of the bidirectional optical coupler U3, the resistor R12 is connected with the capacitor C3 in parallel, and a parallel output end of the resistor R12 and the capacitor C3 is connected with the buffer circuit.

[0017] In some embodiments of the present application, the buffer circuit comprises a signal processing chip, the signal processing chip has three input ports and three output ports and a set of power supply ports, the three input ports are respectively connected with the AB-phase circuit, the CA-phase circuit and the BC-phase circuit of the acquisition circuit, and the three output ports are connected with the judgment module.

[0018] In some embodiments of the present application, the judgment module comprises a logic chip, a clock circuit, a reset circuit and a data circuit, the logic chip has a clock port, a reset port and a data port, the clock port is connected with the clock circuit, the reset port is connected with the reset circuit, and the data port is connected with the data circuit.

[0019] In a second aspect, embodiments of the present application provide a relay control method, comprising:

[0020] acquiring a voltage value of a leading phase of a load phase connected with the relay and outputting an enable signal;

[0021] receiving an on-off signal and the enable signal, judging the enable signal, if the enable signal is a valid enable signal, outputting a drive signal, the valid enable signal is an enable signal when the voltage value of the leading phase of the load phase reaches a target AC voltage threshold, if the enable signal is an invalid enable signal, outputting a maintenance signal;

[0022] controlling on-off of the relay based on the drive signal, and controlling action maintenance of the relay based on the maintenance signal.

[0023] In some embodiments of the present application, before the step of acquiring a voltage value of a leading phase of a load phase connected with the relay and outputting an enable signal, the method further comprises:

[0024] acquiring an action time of the relay;

[0025] determining the target AC voltage threshold when the zero-point on-off signal is sent according to the action time and a phase difference between the load phase and the leading phase.

[0026] The beneficial effects of embodiments of the present application are as follows:

[0027] In the embodiment of the present application, the load phase leading phase voltage value collection and the enable signal output are mainly realized by using the isolation voltage threshold value collection module, the driving signal output is realized by using the judgment module to judge the enable signal, and finally the relay is controlled to realize zero-crossing switching by using the relay driving module to receive the driving signal, so as to effectively avoid the arc discharge of the relay during switching, prolong the service life of the relay, and make the current change more slowly and the inrush current smaller by making the relay switch at zero-crossing, thereby reducing the impact on other elements in the current and effectively reducing the generation of electromagnetic interference, improving the reliability and safety of the circuit. In detail, first, the isolation voltage threshold value collection module collects the voltage value of the leading phase of the load phase connected to the relay and outputs an enable signal. Then, the judgment module receives the switching signal and continuously receives the enable signal, judges the enable signal, and outputs a driving signal if the enable signal is a valid enable signal, that is, the enable signal output by the isolation voltage threshold value collection module when the voltage value reaches the target voltage threshold. Finally, the relay driving module controls the relay to switch based on the driving signal, so that the relay can offset the time delay of its own action by using the leading phase, thereby making the relay switch at zero-crossing, preventing the generation of arc, and effectively prolonging the service life of the relay. If the enable signal received by the judgment module is an invalid enable signal, a maintenance signal will be output, and the relay driving module will keep its current action unchanged based on the maintenance signal, for example, if the relay is currently closed, it will continue to maintain the closed state, and if the relay is currently open, it will continue to maintain the open state. When the enable signal is a valid enable signal, the relay driving module drives the relay to switch based on the switching signal and the driving signal, which can effectively prevent the relay from switching at a non-zero-crossing point, effectively reduce the probability of electromagnetic interference and arc generation. Moreover, the relay zero-crossing switching can be realized by using various hardware devices without using a microcontroller, which can effectively reduce the complexity and cost of the circuit. BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0029] FIG. 1 is a connection diagram of a relay control circuit provided by an embodiment of the present application;

[0030] FIG. 2 is a structural diagram of a relay control circuit provided by an embodiment of the present application;

[0031] FIG. 3 is a circuit diagram of a collection circuit in an isolation voltage threshold value collection module provided by an embodiment of the present application;

[0032] Fig. 4 is a circuit diagram of a buffer circuit provided by an embodiment of the present application;

[0033] Fig. 5 is a circuit diagram of one phase of a judging module provided by an embodiment of the present application;

[0034] Fig. 6 is a circuit diagram of one phase of a relay driving module provided by an embodiment of the present application;

[0035] Fig. 7 is a flow chart of a relay zero-point switch control method provided by an embodiment of the present application;

[0036] Fig. 8 is a data diagram of a relay zero-point test provided by an embodiment of the present application. DETAILED DESCRIPTION

[0037] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application. In addition, it should be understood that the specific implementations described herein are only used to illustrate and explain the present application, and are not used to limit the present application. In the present application, the orientation words such as "upper" and "lower" generally refer to the upper and lower in the actual use or working state of the device, and specifically refer to the direction of the drawing surface in the drawings; and "inner" and "outer" refer to the outline of the device.

[0038] Referring to Figs. 1 and 2, the embodiments of the present application provide a relay control circuit, which comprises:

[0039] an isolation voltage threshold acquisition module, configured to acquire a voltage value of a leading phase of a load phase of a relay and output an enable signal;

[0040] a judging module, configured to receive a on-off signal and the enable signal, and judge the enable signal, output a driving signal if the enable signal is a valid enable signal, and output a maintaining signal if the enable signal is an invalid enable signal, wherein the valid enable signal is an enable signal when the voltage value of the leading phase of the load phase reaches a target AC voltage threshold.

[0041] a relay driving module, configured to control the on-off of the relay based on the driving signal, and control the action maintenance of the relay based on the maintaining signal.

[0042] The technical scheme provided in the application is mainly to collect the voltage value of the leading phase of the load phase by using the isolated voltage threshold acquisition module and output an enable signal, to output a driving signal by using the judging module to judge the enable signal, and finally to receive the driving signal by using the relay driving module and control the relay to realize zero-crossing switching, so as to effectively avoid the arc discharge of the relay during switching, prolong the service life of the relay, and make the current change more slowly by making the relay zero-crossing switching, so as to reduce the impact on other elements in the current, effectively reduce the generation of electromagnetic interference, and improve the reliability and safety of the circuit. In detail, the voltage value of the leading phase of the load phase connected to the relay is collected by using the isolated voltage threshold acquisition module and an enable signal is output. The switching signal is received by using the judging module, and the enable signal is continuously received and judged. If the enable signal is a valid enable signal, that is, the enable signal output by the isolated voltage threshold acquisition module when the voltage value reaches the target voltage threshold, the judging module outputs a driving signal. Finally, the relay driving module controls the relay switching based on the driving signal, so that the relay can offset the time delay of its own action by using the leading phase, so that the relay can realize zero-crossing switching and prevent the generation of arc, effectively prolonging the service life of the relay. If the enable signal received by the judging module is an invalid enable signal, a maintenance signal will be output, and the relay driving module will keep its current action unchanged based on the maintenance signal, such as the current relay being closed, which will continue to maintain the closed state, and the relay being open, which will continue to maintain the open state, until the enable signal is a valid enable signal, and then the relay driving module will drive the relay to switch based on the switching signal and the driving signal, which can effectively avoid the action of the relay at the non-zero-crossing point, effectively reduce the probability of electromagnetic interference and arc generation. Moreover, the relay zero-crossing switching can be realized by using various hardware devices without using a microcontroller, which can effectively reduce the complexity and cost of the circuit.

[0043] It should be noted that the AC power supply includes A phase, B phase and C phase, the contact end of the relay is connected with the AB phase, that is, the load phase is the AB phase of the AC power supply, the leading phase is the CA phase, and the CA phase leads the AB phase by 120°. In other embodiments, the contact end of the relay can also be connected with other phases, such as the BC phase, as long as the leading phase can lead the phase connected to the relay by 120°.

[0044] In some embodiments, referring to FIG. 2, the relay control circuit can further comprise a time acquisition module and a threshold calculation module. The time acquisition module is in signal connection with the threshold calculation module, the isolated voltage threshold acquisition module is in signal connection with the threshold calculation module, and the isolated voltage threshold acquisition module is also in signal connection with the judgment module, the judgment module is in signal connection with the relay drive module, and the relay drive module is in signal connection with the relay.

[0045] The time acquisition module is mainly responsible for capturing the starting action time and the ending action time of the relay in real time, thereby obtaining the delay action time of the relay, and collecting multiple sets of action data to obtain the average delay time of the relay, i.e., the action time of the relay. Because the action time of the relay can be effectively resisted from changing due to the increase of the service life of the relay (the action time of the relay generally changes due to various reasons such as mechanical wear as the service life increases), the action time information is directly transmitted to the threshold calculation module through signal connection. The threshold calculation module calculates the accurate time of the next zero voltage crossing point through a preset algorithm according to the received action time data, thereby determining the optimal relay action time point. The signal connection between the time acquisition module and the threshold calculation module ensures that the threshold calculation module can obtain the relay action time information in real time, increases the accuracy and response speed of the circuit control, and avoids the negative impact of alternating voltage fluctuation on the relay action. In other embodiments, the action time of the relay can also be measured by a measurement circuit composed of an oscilloscope, a signal generator, a sensor, a power supply, and the like.

[0046] The isolated voltage threshold acquisition module is in signal connection with both the threshold calculation module and the judgment module. It is responsible for collecting the voltage threshold of the load phase and converting the information into the corresponding enable signal. This conversion process is completed through a buffer circuit, ensuring the stability and reliability of the signal. The role of this module not only lies in providing real-time voltage threshold data to the threshold calculation module to assist in calculation, but also lies in directly providing key enable signals to the judgment module, improving the flexibility and response capability of the entire control circuit.

[0047] The judgment module performs logical judgment according to the enable signal received from the isolated voltage threshold acquisition module and the on-off signal provided by the threshold calculation module. If the judgment result shows that the on-off condition is met (i.e., there is an input of valid enable signal and on-off signal), the instruction to drive the relay action is output to the relay drive module. This connection ensures that the relay is driven to perform on-off operation at the correct time, reducing the wear of the electrical contact points and prolonging the service life of the relay.

[0048] The relay driving module receives the driving signal from the judging module, and effectively drives the relay through the internal driving circuit (such as MOS tube, light emitting diode, etc.) to complete the on-off operation. This connection not only serves as a bridge between the judging module and the relay, but also reduces the energy loss generated during the driving process through circuit design, thereby improving the overall energy efficiency of the system.

[0049] In some embodiments, the threshold calculation module calculates the target AC voltage threshold according to the following formula:

[0050] wherein T R represents the action time, V ac represents the AC voltage effective value, V th represents the target AC voltage threshold. The AC voltage effective value (RMS, Root Mean Square) is a measure of the size of the AC voltage, which is equivalent to the DC voltage value that can produce the same thermal effect. The AC voltage effective value is the statistical average of the voltage or current in the AC circuit, which can reflect the actual power of the electric energy transmission. The effective value is the square root of the average value of the square of the time-varying function of voltage or current, and its specific calculation formula is the existing formula, which is not described here. In a sinusoidal AC, the voltage effective value is about 0.707 times the peak voltage.

[0051] In some embodiments, the load phase is the B-phase line of the AC power supply, the leading phase is the C-phase line of the AC power supply, the power line of the AC power supply is the A-phase line, the moving and stationary contacts of the relay are connected with the A-phase line and the B-phase line respectively, the input end of the isolation voltage threshold acquisition module is connected with the A-phase line and the C-phase line respectively, and the output end of the isolation voltage threshold is connected with the judging module.

[0052] In some embodiments, the isolation voltage threshold acquisition module includes an acquisition circuit and a buffer circuit, the input end of the acquisition circuit is connected with the input end of the buffer circuit, the acquisition circuit is used to acquire the voltage value of the leading phase of the load phase connected with the relay, and output a voltage signal when the acquired voltage value reaches the target AC voltage threshold, the buffer circuit is used to receive the voltage signal and process the voltage signal into an effective enable signal, and the output end of the buffer circuit is connected with the judging module to output the effective enable signal to the judging module. The acquisition circuit and the buffer circuit are connected through signals, ensuring that the voltage information obtained from the acquisition circuit can be smoothly and accurately transmitted to the buffer circuit. The enable signal processed by the buffer circuit is transmitted to the judging module through the output end thereof.

[0053] The main task of the acquisition circuit is to detect and acquire the voltage on the load phase, especially the voltage value near the relay action time. Specifically, the instantaneous voltage at each moment in the AC circuit is measured, and then the corresponding voltage threshold is selected according to the action time. By directly measuring the load voltage and capturing the voltage threshold at the correct moment, the acquisition circuit ensures the accuracy of the obtained signal. In addition, as the relay action characteristics change (for example, due to performance degradation caused by age or environmental changes), the acquisition circuit can update the voltage threshold information near the action time in real time. This means that the system can adapt itself and maintain the optimization of relay action even in the case of device aging or environmental condition changes.

[0054] The role of the buffer circuit is to receive the voltage signal output by the acquisition circuit and perform necessary processing on the signal, such as signal amplification, filtering, or conversion, to generate the correct enable signal. The buffer circuit not only ensures stable transmission of the signal and avoids signal errors caused by load fluctuations, but also provides necessary signal adjustment functions, such as removing noise through a filter and enhancing signal strength through an amplifier, thereby ensuring that the enable signal output to the judgment module is stable and reliable.

[0055] In some embodiments, the judgment module mainly outputs the corresponding judgment result by determining whether the enable signal and the on-off signal are input at the same time, and whether the enable signal is a valid enable signal or an invalid enable signal. In detail, if the judgment module receives the on-off signal and the valid enable signal, it outputs the drive signal; otherwise, it outputs the maintenance signal to prevent the relay from acting.

[0056] It should be noted that the valid enable signal refers to the signal output when the voltage threshold of the load phase is equal to the target AC voltage threshold. The voltage threshold of the load phase refers to the voltage value measured directly from the load phase by the isolation voltage threshold acquisition module through its acquisition circuit. This voltage value changes in real time with the periodic fluctuations of the grid voltage. The target AC voltage threshold refers to the preset voltage value calculated by the threshold calculation module according to a specific algorithm (considering parameters such as relay action time). This threshold aims to determine the optimal relay on-off time to ensure that the relay operates near the zero voltage point of the AC voltage waveform. By ensuring that the valid enable signal is only output when the voltage threshold of the load phase is equal to the set target AC voltage threshold, this scheme can accurately control the on-off time of the relay near the zero point of the voltage waveform, which helps to minimize the arc generated during on-off operation and reduce the damage to the relay contacts.

[0057] In some embodiments, the control circuit further comprises a correction module. The correction module is connected with the time acquisition module, and is configured to correct the action time of the relay. The correction module is mainly used to detect whether the action time of the relay matches the marked action time, and if not, the correction module takes the actual action time of the relay as the calculation time of the subsequent target AC voltage threshold, so as to ensure that the relay can always act at zero point.

[0058] In some embodiments, referring to FIG. 3, the isolated voltage threshold acquisition module comprises A-phase circuit, B-phase circuit and C-phase circuit connected with each other, and further comprises bidirectional optocoupler U3, bidirectional optocoupler U2, bidirectional optocoupler U1 and filter circuit RC3, filter circuit RC2 and filter circuit RC1. The input end of the bidirectional optocoupler U3 is connected with the A-phase line and the C-phase line, the output end of the bidirectional optocoupler U3 is connected with the filter circuit RC3, and the output end of the filter circuit RC3 is connected with the buffer circuit. The input end of the bidirectional optocoupler U2 is connected with the B-phase line and the C-phase line, the output end of the bidirectional optocoupler U2 is connected with the filter circuit RC2, and the output end of the filter circuit RC2 is connected with the buffer circuit. The input end of the bidirectional optocoupler U1 is connected with the A-phase line and the B-phase line, the output end of the bidirectional optocoupler U1 is connected with the filter circuit RC1, and the output end of the filter circuit RC1 is connected with the buffer circuit. In a three-phase circuit, A-phase, B-phase and C-phase represent three sinusoidal AC voltages with a phase difference of 120°. The A-phase circuit, the B-phase circuit and the C-phase circuit are connected to the corresponding three-phase load for monitoring the corresponding voltage. The optocoupler is a device that uses optical signals for electrical isolation, which allows the circuit to transmit signals between different potentials without interfering with each other. In the module, bidirectional optocouplers U1, U2 and U3 are responsible for isolating signals between A-phase and B-phase, B-phase and C-phase, and C-phase and A-phase, respectively. This design using optocouplers not only provides a channel for signal transmission, but also ensures the safety of isolation between the control circuit and the high-voltage side. The filter circuit is used to filter noise from the signals transmitted by the optocoupler, delete possible interference, and stabilize the output signal, thereby further improving the quality and reliability of the signal.

[0059] Further, the bidirectional optical coupler U1, the bidirectional optical coupler U2, and the bidirectional optical coupler U3 have the same structure, and the filter circuit RC1, the filter circuit RC2, and the filter circuit RC3 have the same structure. The bidirectional optical coupler mainly serves as a medium between the sensing signal and the control signal, allowing the signal to cross the boundary of electrical isolation while preventing direct electrical connection between circuits to ensure the safety of the equipment and the user. The filter circuit RC1 includes a resistor R12 and a capacitor C3, an input end of the resistor R12 is connected with an output end of the bidirectional optical coupler U3, the resistor R12 is connected with the capacitor C3 in parallel, and a parallel output end of the resistor R12 and the capacitor C3 is connected with the buffer circuit, effectively removing high-frequency noise generated by external interference, power fluctuations, or signal transmission processes.

[0060] Further, the output end of the bidirectional optical coupler U1, the output end of the bidirectional optical coupler U2, and the output end of the bidirectional optical coupler U3 are each provided with a reserved end, increasing the connection port of the bidirectional optical coupler and improving the circuit compatibility of the bidirectional optical coupler.

[0061] It should be noted that the turn-on voltage of the bidirectional optical coupler U3 is equal to the target AC voltage threshold, so that the condition for the isolation voltage threshold acquisition module to turn on must be that the acquired voltage value is equal to the target AC voltage threshold, thereby realizing the relationship determination between the acquired voltage and the target AC voltage threshold without the need for the microcontroller to regulate the voltage, so as to output an effective enable signal that enables the relay to pass through zero and turn on.

[0062] In some embodiments, referring to FIG. 4, the buffer circuit includes a signal processing chip having three input ports and three output ports and a set of power supply ports, the three input ports are respectively connected with the A-phase circuit, the B-phase circuit, and the C-phase circuit of the acquisition circuit, and the three output ports are connected with the judgment module.

[0063] In some embodiments, referring to FIG. 5, the judging module includes a logic chip, a clock circuit, a reset circuit, and a data circuit. The logic chip has a clock port, a reset port, and a data port. The clock port is connected to the clock circuit, the reset port is connected to the reset circuit, and the data port is connected to the data circuit. The logic chip is the core of the judging module, which is used to process input signals and generate output. These input signals usually include clock signals, reset signals, and data signals from the data circuit. According to these inputs, the logic chip performs a predetermined logic operation to determine whether to output a signal to drive the relay. The clock circuit provides a continuous clock signal (pulse sequence) to ensure that the operation of the judging module can be synchronized at regular time intervals. The reset circuit can initialize the state of the logic chip, i.e., reset the output of the logic chip to the initial state when the power is turned on or under certain conditions, which can prevent false operation of the logic chip due to accidental circuit fluctuations or abnormalities. The data circuit provides input data to the logic chip. These data come from the circuit in the previous stage, such as the filter circuit in the isolated voltage threshold acquisition module. These data carry information about the system state, such as whether the voltage threshold is reached, whether the relay should be on or off, etc. The logic chip will make a judgment based on these data and output the corresponding control signal.

[0064] It should be noted that the clock circuit includes resistors R17, R20, and capacitor C6. The resistor R17 is connected in parallel with the resistor R20 and the capacitor C6, and the resistor R20 is also connected in parallel with the capacitor C6. The two ends of the clock circuit are connected to the output end of the buffer circuit and the clock circuit end of the logic chip, respectively. The reset circuit includes resistors R18 and capacitor C7, which are connected in parallel. The data circuit includes resistors R16 and R19, which are connected in parallel.

[0065] It should also be noted that the judging module is connected to the three-phase power supply, so the logic chip, clock circuit, reset circuit, and data circuit in the judging module are provided in each phase, and the structures are the same. In this embodiment, the judging module includes the logic chip, clock circuit, reset circuit, and data circuit of phase C, as well as the logic chip, clock circuit, reset circuit, and data circuit of phase A and the logic chip, clock circuit, reset circuit, and data circuit of phase B. The structures of the logic chip, clock circuit, reset circuit, and data circuit of phase A, phase B, and phase C are the same.

[0066] In some embodiments, referring to FIG. 6, the relay driving module includes a relay K1, a light-emitting diode D2, a Schottky diode D1, and a MOS tube Q1, the relay K1, the light-emitting diode D2, and the Schottky diode D1 are connected in parallel with each other, the source of the MOS tube Q1 is grounded, the drain of the MOS tube Q1 is connected with the parallel output end of the relay K1, the light-emitting diode D2, and the Schottky diode D1, and the gate of the MOS tube Q1 is connected with the output end of the judging module.

[0067] Among them, the relay K1 is the core of the whole driving module, and according to the control signal, the circuit is closed or opened, so as to drive the power-on or power-off of the corresponding equipment. In this embodiment, because the vacuum pump needs to be heated when it is running, so as to avoid the condensation deposition of the vacuum pump or other adverse consequences. The relay and the relay control circuit in this embodiment are mainly applied to the switching control of the heating device of the vacuum pump. By setting the relay control circuit capable of zero-crossing conduction, the relay is controlled to pass through zero, which is beneficial to avoid the arc caused by the on-off of the relay in the high-voltage environment, affecting the service life of the relay, and the surge current and electromagnetic interference caused by the on-off of the relay, causing adverse effects on the control system of the whole vacuum pump.

[0068] The light-emitting diode D2 (LED) in the relay driving module, the parallel light-emitting diode D2 plays an indicating role, when the relay K1 is driven (i.e. the MOS tube Q1 is turned on), D2 emits light, providing intuitive working state indication for the operator.

[0069] The Schottky diode D1 has the characteristics of low forward voltage drop and fast switching. In this driving module, the Schottky diode D1 is connected in parallel with the relay K1 and D2, and is mainly used to prevent the reverse potential released by the relay coil from damaging the driving tube or other sensitive elements when the MOS tube Q1 is cut off.

[0070] The MOS tube Q1 is used as a switching element of the driving module, and is responsible for directly driving the relay K1 according to the output control signal of the judging module. When Q1 is turned on, the current flows through the relay K1, the light-emitting diode D2, and the Schottky diode D1, so that the relay K1 is attracted and the status indication LED is lit.

[0071] The relay K1, the light-emitting diode D2, and the Schottky diode D1 are connected in parallel with each other. This parallel connection ensures that when the MOS tube Q1 is turned on, the current can flow through the relay K1, the light-emitting diode D2, and the Schottky diode D1 at the same time. Among them, the Schottky diode D1 provides a freewheeling circuit when the relay coil is powered off, and the light-emitting diode D2 provides operation indication.

[0072] Please refer to FIG. 7, the embodiment of the application further provides a relay zero-point switch control method, which is applied to the relay control circuit in any of the foregoing embodiments, and the control method comprises the following steps:

[0073] S1, collecting a voltage value of a leading phase of a load phase connected to a relay and outputting an enable signal;

[0074] S2, receiving the on-off signal and the enable signal, judging the enable signal, outputting a driving signal if the enable signal is a valid enable signal, outputting a maintaining signal if the enable signal is an invalid enable signal, the valid enable signal being an enable signal when the voltage value of the leading phase of the load phase reaches a target AC voltage threshold, and the invalid enable signal being any other enable signal;

[0075] S3, controlling the on-off of the relay based on the driving signal and controlling the action of the relay based on the maintaining signal.

[0076] In the step of collecting the voltage value of the leading phase of the load phase connected to the relay and outputting the enable signal, the collection of the voltage value and the output of the enable signal are continuous, i.e. continuously collecting the voltage value and outputting the enable signal. It should be noted that the output enable signal is different according to the voltage value, specifically, the enable signal output when the collected voltage value reaches the target AC voltage threshold is the valid enable signal, and the remaining enable signals are invalid enable signals.

[0077] In the step of outputting the driving signal according to the received on-off signal and enable signal, the judgment module will output the result according to the signals received by itself. If the judgment module receives the on-off signal and the valid enable signal, the judgment module will output a positive judgment result, i.e. output the driving signal. If only the on-off signal or the invalid enable signal is received, or neither the on-off signal nor the invalid enable signal is received, the maintaining signal is output, the relay is not controlled to act, and the original state is maintained, if the relay is in the attracted state, the attracted state is maintained, and if the relay is in the disconnected state, the disconnected state is maintained.

[0078] In some embodiments, before step S1, the control method can further comprise:

[0079] acquiring an action time of the relay;

[0080] determining the target AC voltage threshold when the zero-point on-off signal is sent according to the action time and the phase difference between the load phase and the leading phase.

[0081] In the step of acquiring the action time of the relay, the system first needs to determine the time required for the relay to act (i.e. the contact to close or open) from receiving the on-off signal. This time can be obtained by testing or based on the specification parameters of the relay.

[0082] In the step of determining the target AC voltage threshold at which the zero-crossing signal is sent according to the action time and the phase difference between the load phase and the leading phase, the target AC voltage threshold required is calculated according to the frequency of the current power grid, the action time and the phase of the load. This value indicates the voltage level at which the zero-crossing signal is sent, i.e. the voltage level at which the relay action is synchronized with the zero-crossing of the AC voltage.

[0083] In some embodiments, the step of determining the target AC voltage threshold at which the zero-crossing signal is sent according to the action time and the phase difference between the load phase and the leading phase comprises:

[0084] The load phase is obtained and a phase line leading the load phase by 120° is determined as the reference phase for the enable signal of the relay. In a three-phase AC system, the load phase refers to the specific phase line (e.g. phase A, phase B or phase C) to which the relay is connected. In this embodiment, another phase line leading the load phase by 120° is selected as the reference phase. Since the phase lines of a three-phase system are inherently staggered by 120° with respect to each other, selecting a reference phase leading by 120° means that a forward-looking enable signal can be provided using the reference phase to ensure accurate control of the load phase.

[0085] The time at which the relay is to act on the reference phase of the enable signal and the corresponding angle are calculated according to the phase difference of the AC voltage and the action time. The time at which the relay is to act on the reference phase is calculated according to the phase difference of the AC voltage and the action time of the relay. This time is calculated according to the frequency of the power grid and the physical characteristics of the action time of the relay. The corresponding angle is also calculated, because in an AC circuit, time can be converted into an angle related to the frequency on the voltage waveform.

[0086] The effective value of the AC voltage is obtained, and the target AC voltage threshold is calculated according to the effective value of the AC voltage and the time and angle at which the reference phase of the enable signal is to act. The system needs to obtain the effective value (i.e. RMS value) of the AC voltage. This is a fixed value, which is usually determined according to the standard of the power grid (e.g. 220V RMS). According to the obtained effective value of the AC voltage and the calculated time and angle at which the reference phase of the enable signal is to act, the target AC voltage threshold is then calculated. This threshold is the voltage level to be considered when the zero-crossing signal is sent. Through the calculation of this threshold, it is ensured that the AC voltage is passing through zero when the contacts of the relay are to act.

[0087] It should be noted that the calculation formula for the time at which the reference phase of the enable signal is to act is:

[0088] T l = 6.66 - T R

[0089] wherein, T R represents the action time, T l refers to the time when the enable signal refers to the phase action.

[0090] The calculation formula of the angle corresponding to the enable signal referring to the phase action is:

[0091] The calculation formula of the target AC voltage threshold is:

[0092] V th = sin(a l )·V ac

[0093] wherein, V ac represents the AC voltage effective value, V th represents the target AC voltage threshold.

[0094] In some embodiments, the step of collecting the voltage value of the leading phase of the load phase connected to the relay and outputting the enable signal comprises:

[0095] Collecting the voltage threshold of the load phase and outputting the voltage signal according to the voltage threshold. The system continuously collects the real-time voltage of the load phase through the monitoring circuit, and compares the collected voltage value with the predetermined voltage threshold. If the collected voltage value meets the range of the target AC voltage threshold, the collected voltage value is output as a voltage signal. The purpose of this comparison process is to determine whether the current grid voltage has reached a specific level, which is calculated according to the actual application conditions and the characteristics of the relay, and in an ideal case, should be as close to the zero voltage crossing point as possible.

[0096] Outputting the effective enable signal corresponding to the voltage signal. After the system generates a voltage signal, it needs to be converted into an effective enable signal. The generation of the effective enable signal usually depends on a series of electronic circuit operations, including logical judgment, signal conversion, etc. These operations ensure that the output of the enable signal strictly corresponds to the voltage signal, ensuring that the voltage is in an ideal state, i.e., zero or close to zero, when the on-off operation is actually performed.

[0097] In some embodiments, the step of judging the enable signal according to the received on-off signal and enable signal, outputting the drive signal if the enable signal is the effective enable signal, and outputting the maintenance signal if the enable signal is the ineffective enable signal, comprises:

[0098] When the judging module receives the on-off signal and the enable signal, and the enable signal is a valid enable signal, the judging module outputs a driving signal to drive the relay to act. The judging module only outputs the driving signal when it receives both the on-off signal and the valid enable signal. If the judging module only receives the on-off signal, does not receive the enable signal, or receives the on-off signal and the enable signal but the enable signal is an invalid enable signal, the judging module outputs a maintaining signal to maintain the current state of the relay until the valid enable signal is received. In this way, the relay can realize zero-point on-off, and the whole judging process does not need to use a microcontroller, so that the control circuit is simpler. The valid enable signal means that it reflects that the voltage threshold of the load phase has matched the preset target AC voltage threshold, that is, if the relay acts at this time, the time of the relay action will be at zero point.

[0099] Based on the above control method and control circuit, the application provides an experiment of relay zero-point on-off. Please refer to FIG. 8. FIG. 8 is a data schematic diagram of the relay zero-point test provided by the embodiment of the application.

[0100] The above has described the embodiments of the application in detail, and the principles and implementation manners of the application have been described by using specific examples. The above description of the embodiments is only used to help understand the method of the application and its core idea; meanwhile, for those skilled in the art, according to the idea of the application, the specific implementation manner and application range can be changed, and the above description of the content of the specification should not be understood as a limitation of the application.

Claims

1. A relay control circuit, characterized by comprising: The relay control circuit comprises a relay, a relay driving module, a judgment module and an isolated voltage threshold acquisition module. The relay control circuit further comprises an A-phase line, a B-phase line and a C-phase line, the load phase is an AB phase of an alternating current power supply, the leading phase is a CA phase of the alternating current power supply, the moving contact and the stationary contact of the relay are connected with the A-phase line and the B-phase line respectively, the input ends of the isolated voltage threshold acquisition module are connected with the A-phase line and the C-phase line respectively, and the output end of the isolated voltage threshold is connected with the judgment module. The isolated voltage threshold acquisition module comprises an acquisition circuit and a buffer circuit, the input end of the acquisition circuit is connected with the buffer circuit, the acquisition circuit is used for acquiring the voltage value of the leading phase of the load phase connected with the relay and outputting a voltage signal, the buffer circuit is used for receiving the voltage signal and processing the voltage signal into an enable signal, and the output end of the buffer circuit is connected with the judgment module to output the enable signal to the judgment module. The acquisition circuit comprises a bidirectional optical coupler U3 and a filter circuit RC3, the input end of the bidirectional optical coupler U3 is connected with the A-phase line and the C-phase line, the output end of the bidirectional optical coupler U3 is connected with the filter circuit RC3, and the output end of the filter circuit RC3 is connected with the buffer circuit.

2. The relay control circuit of claim 1, wherein, The target AC voltage threshold is: where T R represents the action time of the relay on-off, V ac represents the effective value of the alternating voltage, V th represents the target alternating voltage threshold value.

3. The relay control circuit of claim 1, wherein, The turn-on voltage of the bidirectional optical coupler U3 is equal to the target alternating current voltage threshold.

4. The relay control circuit of claim 3, wherein, The filter circuit RC3 comprises a resistor R12 and a capacitor C3, the input end of the resistor R12 is connected with the output end of the bidirectional optical coupler U3, the resistor R12 is connected with the capacitor C3 in parallel, and the parallel output end of the resistor R12 and the capacitor C3 is connected with the buffer circuit.

5. The relay control circuit of claim 4, wherein, The buffer circuit comprises a signal processing chip, the signal processing chip has three input ports, three output ports and a group of power supply ports, the three input ports are connected with the AB phase circuit, the CA phase circuit and the BC phase circuit of the acquisition circuit respectively, and the three output ports are connected with the judgment module.

6. The relay control circuit of claim 5, wherein, The judgment module comprises a logic chip, a clock circuit, a reset circuit and a data circuit, the logic chip has a clock port, a reset port and a data port, the clock port is connected with the clock circuit, the reset port is connected with the reset circuit, and the data port is connected with the data circuit.

7. The relay control circuit of claim 5, wherein, The relay control circuit comprises a relay, a relay driving module, a judgment module and an isolated voltage threshold acquisition module.

8. The relay control circuit of claim 5, wherein, The relay control circuit further comprises an A-phase line, a B-phase line and a C-phase line, the load phase is an AB phase of an alternating current power supply, the leading phase is a CA phase of the alternating current power supply, the moving contact and the stationary contact of the relay are connected with the A-phase line and the B-phase line respectively, the input ends of the isolated voltage threshold acquisition module are connected with the A-phase line and the C-phase line respectively, and the output end of the isolated voltage threshold is connected with the judgment module.

9. The relay control circuit according to any one of claims 1 to 8, wherein The isolated voltage threshold acquisition module comprises an acquisition circuit and a buffer circuit, the input end of the acquisition circuit is connected with the buffer circuit, the acquisition circuit is used for acquiring the voltage value of the leading phase of the load phase connected with the relay and outputting a voltage signal, the buffer circuit is used for receiving the voltage signal and processing the voltage signal into an enable signal, and the output end of the buffer circuit is connected with the judgment module to output the enable signal to the judgment module.

10. A relay control method characterized by, The acquisition circuit comprises a bidirectional optical coupler U3 and a filter circuit RC3, the input end of the bidirectional optical coupler U3 is connected with the A-phase line and the C-phase line, the output end of the bidirectional optical coupler U3 is connected with the filter circuit RC3, and the output end of the filter circuit RC3 is connected with the buffer circuit. The turn-on voltage of the bidirectional optical coupler U3 is equal to the target alternating current voltage threshold. The filter circuit RC3 comprises a resistor R12 and a capacitor C3, the input end of the resistor R12 is connected with the output end of the bidirectional optical coupler U3, the resistor R12 is connected with the capacitor C3 in parallel, and the parallel output end of the resistor R12 and the capacitor C3 is connected with the buffer circuit. The buffer circuit comprises a signal processing chip, the signal processing chip has three input ports, three output ports and a group of power supply ports, the three input ports are connected with the AB phase circuit, the CA phase circuit and the BC phase circuit of the acquisition circuit respectively, and the three output ports are connected with the judgment module. The judgment module comprises a logic chip, a clock circuit, a reset circuit and a data circuit, the logic chip has a clock port, a reset port and a data port, the clock port is connected with the clock circuit, the reset port is connected with the reset circuit, and the data port is connected with the data circuit. The relay control circuit comprises a relay, a relay driving module, a judgment module and an isolated voltage threshold acquisition module. The relay control circuit further comprises an A-phase line, a B-phase line and a C-phase line, the load phase is an AB phase of an alternating current power supply, the leading phase is a CA phase of the alternating current power supply, the moving contact and the stationary contact of the relay are connected with the A-phase line and the B-phase line respectively, the input ends of the isolated voltage threshold acquisition module are connected with the A-phase line and the C-phase line respectively, and the output end of the isolated voltage threshold is connected with the judgment module. The on-off signal and the enable signal are received, and the enable signal is judged. If the enable signal is a valid enable signal, a driving signal is output. The valid enable signal is an enable signal when the voltage value of the leading phase of the load phase reaches a target AC voltage threshold. If the enable signal is an invalid enable signal, a maintenance signal is output. The on-off of the relay is controlled based on the driving signal, and the action of the relay is maintained based on the maintenance signal.

11. The relay control method according to claim 10, wherein Before the step of collecting the voltage value of the leading phase of the load phase connected to the relay and outputting the enable signal, the method further comprises: acquiring the action time of the relay; determining the target AC voltage threshold when the zero-point on-off signal is sent according to the action time and the phase difference between the load phase and the leading phase.

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