Switching circuit and output isolation plate

Abstract

The utility model relates to the technical field of power electronics, and discloses a switching circuit and an output isolation board, the output isolation board is composed of a circuit board and a plurality of switching circuits integrated on the circuit board, each switching circuit comprises a voltage stabilizing circuit, a switching unit and an arc extinguishing circuit, the first output end and the second output end of the comparator are correspondingly connected with the first end and the second end of the switch unit respectively, and the second output end of the comparator is grounded; the third end of the switch unit is connected with the first end of the load, and the fourth end and the fifth end of the switch unit are correspondingly connected with the first end and the second end of the arc extinguishing circuit respectively; and the third end and the fourth end of the arc extinguishing circuit are correspondingly connected with the second end and the third end of the load bar. The utility model can improve the stability of load power supply, and is applied to the control box to simplify the wiring in the control box.

Description

Technical Field

[0001] The utility model relates to the technical field of power electronics, and particularly relates to a switching circuit and an output isolation board. Background Art

[0002] Existing output control boxes in underground mines usually do not consider the problems of humid environment and large fluctuations in power supply voltage. The output of a PLC output point usually controls a relay through two control lines. An electric control cabinet requires 8 to 16 groups of control lines or even more, resulting in time-consuming and laborious assembly for operators. Dozens of control lines also make the control cabinet bulky, and it is difficult to troubleshoot faults when the circuit fails.

[0003] In addition, lightning strikes are severe in non-coal mines, especially induced lightning. Small-scale fluctuations can cause great damage to electronic components at the output end. During the process of the relay contact being attracted and disconnected, induced electromotive force often occurs (sometimes the current at the moment of disconnection can be more than 10 times the normal value), or when a large current is disconnected, the air will be ionized to generate an arc. The high temperature of the arc, like arc welding, will melt the electrode contacts, resulting in poor contact or adhesion of the contacts, causing faults in the subsequent equipment. Summary of the Utility Model

[0004] Therefore, the technical problem to be solved by the utility model is to solve the problems of poor output stability and lack of arc extinguishing function in the existing output circuit in underground mines, so as to provide a switching circuit and an output isolation board.

[0005] To achieve the above object, the utility model provides the following technical solutions:

[0006] In a first aspect, the utility model provides a switching circuit, including: a voltage stabilizing circuit, a switching unit, and an arc extinguishing circuit. Among them, for the voltage stabilizing circuit, a control signal is input to its input terminal, its first output terminal and second output terminal are respectively connected to the first end and second end of the switching unit in correspondence, its second output terminal is also grounded, and it is used to suppress the voltage between the first end and second end of the switching unit; for the switching unit, its third end is connected to the first end of the load, and its fourth end and fifth end are respectively connected to the first end and second end of the arc extinguishing circuit in correspondence; for the arc extinguishing circuit, its third end and fourth end are connected to the second end and third end of the load in correspondence, and it is used to absorb the energy released when the switching unit switches its switching state; when the voltage of the control signal is greater than the voltage of the ground connection point, the switching unit switches its switching state, so that conduction is achieved between the first end and second end of the load to start working; when the voltage of the control signal is less than or equal to the voltage of the ground connection point, the switching unit switches its switching state, so that conduction is achieved between the first end and third end of the load to stop working.

[0007] The switching circuit provided by the present utility model, the voltage stabilizing circuit can suppress the overvoltage across the switching unit, avoiding damage to the load due to excessive output voltage or too large a fluctuation range. The arc extinguishing circuit can provide a discharge path for the arc current generated between the switch contacts when the switching unit switches its state in a humid environment, weaken the arc energy, reduce the temperature of the switching unit, and reduce the possibility of melting and adhesion of the switch contacts.

[0008] In an optional embodiment, the voltage stabilizing circuit includes: a lightning protection circuit and a zener diode. Among them, for the lightning protection circuit, its first end inputs a control signal, its second end is connected to the cathode of the zener diode and the first end of the switching unit, and it is used to suppress the overvoltage in the circuit; for the zener diode, its anode is connected to the second end of the switching unit, and it is used to provide a discharge path for the overvoltage in the circuit.

[0009] In an optional embodiment, the lightning protection circuit includes: a varistor, its first end inputs a control signal, and its second end is connected to the cathode of the zener diode.

[0010] In an optional embodiment, the voltage stabilizing circuit further includes: a lighting circuit, its first end is connected to the first end of the lightning protection circuit, its second end is connected to the anode of the zener diode, and it is used to emit light or go out based on the voltage magnitude of the control signal.

[0011] In an optional embodiment, the lighting circuit includes: a light emitting diode and a chip resistor. Among them, for the light emitting diode, its anode is connected to the first end of the lightning protection circuit, and its cathode is connected to the first end of the chip resistor; for the chip resistor, its second end is connected to the anode of the zener diode; when the voltage of the control signal is greater than the ground voltage, the light emitting diode emits light; when the voltage of the control signal is less than or equal to the ground voltage, the light emitting diode goes out.

[0012] For the switching circuit provided by the present utility model, the lighting circuit can gently touch and indicate the current working state of the circuit, facilitating the operator to judge the current power supply state of the load.

[0013] In an optional embodiment, the switching unit includes: a double-pole double-throw relay, its first end and second end are respectively connected to the first output end and the second output end of the voltage stabilizing circuit, its third end and fourth end are both connected to the first end of the load, its fifth end and sixth end are both connected to the first end of the arc extinguishing circuit, and its seventh end and eighth end are both connected to the second end of the arc extinguishing circuit; when the voltage of the control signal is greater than the ground voltage, the third end of the double-pole double-throw relay is connected to the fifth end, and the fourth end of the double-pole double-throw relay is connected to the sixth end; when the voltage of the control signal is less than or equal to the ground voltage, the fourth end of the double-pole double-throw relay is connected to the seventh end, and the fifth end of the double-pole double-throw relay is connected to the eighth end.

[0014] The switch circuit provided by the present utility model adopts a redundant structure of a double-pole double-throw switch, so that when one set of switches and contacts are damaged, the other set of switches and contacts can still be normally closed or cut off, ensuring that the switch circuit can normally respond to actions and improving the reliability of the switch circuit.

[0015] In an alternative embodiment, the arc extinguishing circuit includes: a first arc extinguishing unit and a second arc extinguishing unit, wherein the first arc extinguishing unit is serially connected between the fourth terminal of the switch unit and the second terminal of the load; the second arc extinguishing unit is serially connected between the fifth terminal of the switch unit and the third terminal of the load.

[0016] In an alternative embodiment, both the first arc extinguishing unit and the second arc extinguishing unit include a first capacitor and a first resistor connected in series.

[0017] In an alternative embodiment, the switch circuit further includes: a current limiting resistor, which is serially connected between the third terminal of the switch unit and the first terminal of the load, and is used to limit the magnitude of the current flowing into the first terminal of the load.

[0018] In a second aspect, the present utility model provides an output isolation board, including: a circuit board, a bus connector, and a plurality of switch circuits of the first aspect, wherein the bus connector and all the switch circuits are integrated on the circuit board; the input end of each voltage stabilizing circuit is connected to an output end of a PLC through the bus connector to receive a control signal; the second terminal of each switch unit is grounded through a ground point on the bus connector; when any voltage stabilizing circuit receives a control signal and the voltage of the control signal is greater than the ground point voltage, the switch unit connected to the voltage stabilizing circuit switches its switch state, so that the corresponding load starts to work; when any voltage stabilizing circuit receives a control signal and the voltage of the control signal is less than or equal to the ground point voltage, the switch unit connected to the voltage stabilizing circuit switches its switch state, so that the corresponding load stops working.

[0019] The output isolation board provided by the present utility model integrates a plurality of switch circuits on one circuit board and connects the input ends of the plurality of switch circuits to the PLC by using a bus connector. At the same time, the output isolation board has voltage stabilizing and arc extinguishing functions, the output is stable, and it can be safely applied to a humid environment. The ground point of each switch circuit is not directly connected to the PLC, but is commonly grounded through the ground point on the bus connector, thereby reducing the number of control lines between the PLC and making the wiring circuit simpler. The operator can check the wiring faults through the bus connector, reducing the labor consumption and the complexity of fault troubleshooting, and realizing fast wire replacement and wiring. Description of the Drawings

[0020] To more clearly illustrate the specific embodiments of the present utility model or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present utility model. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0021] Figure 1 It is a composition diagram of a specific example of the switch circuit according to an embodiment of the present utility model;

[0022] Figure 2 It is a structural diagram of a specific circuit of the switch circuit according to an embodiment of the present utility model;

[0023] Figure 3 It is a composition diagram of a specific example of the output isolation board according to an embodiment of the present utility model. Specific Embodiments

[0024] The following will clearly and completely describe the technical solutions of the present utility model in conjunction with the drawings. Obviously, the described embodiments are some embodiments of the present utility model, rather than all embodiments. Based on the embodiments in the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present utility model.

[0025] In the description of the present utility model, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present utility model. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0026] In the description of the present utility model, it should be noted that unless otherwise clearly specified and limited, the terms "installed", "connected", "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can also be the communication inside two elements. It can be a wireless connection or a wired connection. For those of ordinary skill in the art, the specific meanings of the above terms in the present utility model can be understood according to specific situations.

[0027] In addition, the technical features involved in different embodiments of the present utility model described below can be combined with each other as long as they do not conflict with each other.

[0028] In underground non - coal mines, it is generally extremely humid. When the switch circuit switches the switch state, during the process of the contact being attracted and disconnected, induced electromotive force often occurs. Or when the switch is disconnected under the action of a large current, the surrounding air will be ionized to generate an arc. The high temperature of the arc will melt the electrode contacts, resulting in faults such as short - circuit. At the same time, when there are frequent small fluctuations in the input signal, the switch circuit may malfunction frequently, increasing the possibility of faults in the subsequent circuit, and the switch circuit will amplify the small fluctuations, causing the load to be damaged under over - voltage conditions.

[0029] Based on this, this embodiment provides a switch circuit 1, as Figure 1 shown, including: a voltage - stabilizing circuit 11, a switch unit 12, and an arc - extinguishing circuit 13.

[0030] As Figure 1 shown, for the voltage - stabilizing circuit 11, its input terminal inputs a control signal, its first output terminal and second output terminal are respectively connected to the first end and second end of the switch unit 12 correspondingly, and its second output terminal is also grounded (the ground point voltage is 0V).

[0031] Specifically, Figure 1 in, the voltage - stabilizing circuit is used to suppress small fluctuations of the control signal, suppress the voltage between the first end and the second end of the switch unit 12 from being too high or fluctuating, and it can be a structure such as a diode, a triode, etc.

[0032] As Figure 1 shown, for the switch unit 12, its third end is connected to the first end of the load through a terminal block J1, and its fourth end and fifth end are respectively connected to the first end and second end of the arc - extinguishing circuit 13 correspondingly.

[0033] It should be noted that in order to increase the reliability of the switch circuit, the switch unit 12 can be selected as a redundant structure of multiple interlocking switches. When one of the switches fails, the other switches can still operate reliably, ensuring the reliability of the load power supply.

[0034] As Figure 1 shown, for the arc - extinguishing circuit 13, its third end and fourth end are connected to the second end and third end of the load through a terminal block J1 correspondingly, and it is used to absorb the energy released when the switch unit 12 switches the switch state.

[0035] Specifically, Figure 1In it, when the switch circuit is in a humid environment, an induced electromotive force often occurs during the operation of the switch unit 12. Or when the switch unit 12 disconnects with a large current, the surrounding air will be ionized to generate an arc. To prevent the arc from melting the contacts of the switch unit 12, the arc extinguishing circuit 13 is used to absorb the arc energy released when the switch unit 12 operates, discharge quickly, and reduce the possibility of arc generation.

[0036] Figure 1 In it, when the voltage of the control signal is greater than the voltage of the ground point, the switch unit 12 switches the switch state, so that conduction is started between the first end and the second end of the load to start working; when the voltage of the control signal is less than or equal to the voltage of the ground point, the switch unit 12 switches the switch state, so that conduction is started between the first end and the third end of the load to stop working.

[0037] Specifically, Figure 1 In it, the load is connected to the switch circuit 1 through the terminal block J1. When the switch circuit 1 is applied to the control cabinet, the terminal block J1 can keep the control cabinet circuit tidy and facilitate the operator to wire or troubleshoot faults. The terminal block J1 has three connection points. When the voltage of the control signal is greater than the voltage of the ground point, the switch unit 12 switches the switch state, so that a path is formed between the first connection point and the second connection point inside the terminal block J1, so that conduction is started between the first end and the second end of the load, and the load starts to work. When the voltage of the control signal is less than or equal to the voltage of the ground point, the switch unit 12 switches the switch state, so that a path is formed between the first connection point and the third connection point inside the terminal block J1, so that the connection between the first end and the second end of the load is disconnected, and conduction is started between the first end and the third end of the load, and the load stops working.

[0038] For the switch circuit provided in this embodiment, the voltage stabilizing circuit can suppress the overvoltage across the switch unit and prevent the load from being damaged due to too high output voltage or too large voltage fluctuation range. The arc extinguishing circuit can provide a discharge path for the arc current generated between the switch contacts when the switch unit switches the switch state in a humid environment, weaken the arc energy, reduce the temperature of the switch unit, and reduce the possibility of the switch contacts melting and sticking.

[0039] In some alternative embodiments, such as Figure 2 shown, the voltage stabilizing circuit includes 11: a lightning protection circuit 111 and a zener diode D1. Among them, for the lightning protection circuit 111, its first end inputs a control signal, its second end is connected to the cathode of the zener diode D1 and the first end of the switch unit 12, and it is used to suppress the overvoltage in the circuit; for the zener diode D1, its anode is connected to the second end of the switch unit 12, and it is used to provide a discharge path for the overvoltage in the circuit.

[0040] Optionally, such as Figure 2As shown, the lightning protection circuit includes: a varistor RV1, with its first end inputting a control signal and its second end connected to the cathode of a zener diode D1.

[0041] Specifically, Figure 2 In [description], when the switch circuit 1 is applied in an environment with severe lightning strikes, the varistor RV1 is required to withstand the overcurrent of lightning strikes. When the voltage applied to the varistor RV1 is lower than the threshold value of the varistor RV1, the current flowing through the varistor RV1 is extremely small, and the varistor RV1 is equivalent to a resistor with an infinite resistance value; when the voltage applied to the varistor RV1 exceeds its threshold value, the current flowing through the varistor RV1 surges, and the varistor RV1 is equivalent to a resistor with an infinitesimal resistance value, thereby achieving the effect of blocking high voltage and passing low voltage.

[0042] Specifically, Figure 2 In [description], when the voltage of the control signal increases, the zener diode D1 utilizes the reverse breakdown characteristic of the PN junction to maintain a stable voltage output. When the reverse current exceeds a certain critical value, the electric field on the PN junction of the zener diode D1 will strengthen, forming a current breakdown, causing the current to increase rapidly, so that the voltage drop remains unchanged across the zener diode D1, achieving a stable voltage output.

[0043] In some alternative embodiments, as Figure 2 shown, the voltage regulation circuit 11 further includes: a lighting circuit 112, with its first end connected to the first end of the lightning protection circuit 111 and its second end connected to the anode of the zener diode D1, which is used to emit light or go out based on the voltage magnitude of the control signal.

[0044] Specifically, Figure 2 In [description], the lighting circuit 112 includes: a light-emitting diode LED1 and a chip resistor R1. Among them, for the light-emitting diode LED1, its anode is connected to the first end of the lightning protection circuit 111, and its cathode is connected to the first end of the chip resistor R1; for the chip resistor R1, its second end is connected to the anode of the zener diode D1; when the voltage of the control signal is greater than the ground voltage, the light-emitting diode LED1 emits light; when the voltage of the control signal is less than or equal to the ground voltage, the light-emitting diode LED1 goes out. The lighting or extinguishing of the light-emitting diode LED1 is used to indicate the working state of the switch circuit 1, and the operator can judge whether the switch circuit 1 is supplying power to the load by observing whether the light-emitting diode LED1 is lit.

[0045] In some alternative embodiments, as Figure 2As shown, the switch unit 12 includes: a double-pole double-throw relay relay, whose first end and second end are respectively connected to the first output end and the second output end of the voltage stabilizing circuit 11, whose third end and fourth end are both connected to the first end of the load, whose fifth end and sixth end are both connected to the first end of the arc extinguishing circuit 13, and whose seventh end and eighth end are both connected to the second end of the arc extinguishing circuit 13.

[0046] Specifically, Figure 2 in, when the voltage of the control signal is greater than the voltage of the ground point, the third end of the double-pole double-throw relay relay is connected to the fifth end, and the fourth end of the double-pole double-throw relay relay is connected to the sixth end; when the voltage of the control signal is less than or equal to the voltage of the ground point, the fourth end of the double-pole double-throw relay relay is connected to the seventh end, and the fifth end of the double-pole double-throw relay relay is connected to the eighth end.

[0047] Specifically, Figure 2 in, in order to increase the reliability of the switch circuit 1, the double-pole double-throw relay relay is a redundant structure with two sets of identical switches, and the contacts of the two switches are synchronously attracted or disconnected, so that when any one of the switches fails, the other switch can still operate reliably. When the voltage of the control signal is greater than the voltage of the ground point, the COM1 end of one switch is connected to the NO1 end, and the COM2 end of the other switch is connected to the NO2 end, so that the first end and the second end of the load are connected through the double-pole double-throw relay relay; when the voltage of the control signal is less than or equal to the voltage of the ground point, the COM1 end of one switch is connected to the NC1 end, and the COM2 end of the other switch is connected to the NC2 end, so that the first end and the third end of the load are connected through the double-pole double-throw relay relay.

[0048] It should be noted that the number of switches in the double-pole double-throw relay relay is set according to actual engineering requirements and is not limited here.

[0049] In some alternative embodiments, such as Figure 2 shown, the arc extinguishing circuit 13 includes: a first arc extinguishing unit 131 and a second arc extinguishing unit 132, wherein, the first arc extinguishing unit 131 is connected in series between the fourth end of the switch unit 12 and the second end of the load; the second arc extinguishing unit 132 is connected in series between the fifth end of the switch unit 12 and the third end of the load.

[0050] Specifically, both the first arc extinguishing unit 131 and the second arc extinguishing unit 132 include a first capacitor (C1 or C2) and a first resistor (R2 or R3) connected in series. To avoid the generation of arcs between the contacts when the contacts of the double-pole double-throw relay are closed or opened, the RC absorption circuit composed of the first capacitor (C1 or C2) and the first resistor (R2 or R3) consumes energy, forms a path to quickly discharge, rapidly weakens the arc energy, reduces the temperature, and reduces the possibility of contact melting and adhesion.

[0051] It should be noted that the specific structure of the arc extinguishing circuit 13 in this embodiment is only schematically illustrated and is not limited thereto. In other embodiments, a suitable circuit structure can be selected according to the actual application of the circuit.

[0052] Optionally, as Figure 2 shown, the switch circuit 1 further includes: a current limiting resistor F1, which is connected in series between the third terminal of the switch unit 12 and the first terminal of the load, and is used to limit the magnitude of the current flowing into the first terminal of the load.

[0053] This embodiment provides an output isolation board, as Figure 3 shown, including: a circuit board 2, a bus connector 3, and the switch circuit 1 of the above embodiments and any of its optional implementation manners. The circuit board 2 can be integrated in the control box. The operator connects each load to the control box through a terminal block, so that the load can work or stop working under the control of the PLC. Among them, the bus connector 3 and all the switch circuits 1 are integrated on the circuit board 2; the input end of each voltage stabilizing circuit 11 is connected to an output end of the PLC through the bus connector 3 to receive control signals (DO-1 to DO-n); the second end of each switch unit 12 is grounded through the ground point (i.e., the 0V point) on the bus connector 3. The power supply terminal VCC of the PLC is connected to each switch circuit 1 through the bus connector 3 to supply power to each load.

[0054] Specifically, Figure 3 in, when any voltage stabilizing circuit 11 receives a control signal and the voltage of the control signal is greater than the voltage of the ground point, the switch unit 12 connected to the voltage stabilizing circuit switches its switch state, so that the corresponding load starts to work; when any voltage stabilizing circuit 11 receives a control signal and the voltage of the control signal is less than or equal to the voltage of the ground point, the switch unit 12 connected to the voltage stabilizing circuit 11 switches its switch state, so that the corresponding load stops working.

[0055] The output isolation board provided by this embodiment integrates multiple switching circuits on a circuit board, realizes the modularization of the control circuit, and connects the input ends of multiple switching circuits to the PLC by using a bus connector. At the same time, the output isolation board has the functions of voltage stabilization and arc extinguishing, with stable output, and can be safely applied to humid environments. The grounding points of each switching circuit are not directly connected to the PLC, but are grounded together through the grounding point on the bus connector, thereby reducing the number of control lines between the PLC and the wiring circuit, making the wiring circuit simpler. Operators can troubleshoot wiring faults through the bus connector, reducing labor consumption and the complexity of fault troubleshooting, and realizing fast wire replacement and wiring.

[0056] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations fall within the scope defined by the appended claims.

Claims

1. A switching circuit, characterized in that: include: A voltage stabilizing circuit, a switch unit and an arc extinguishing circuit, wherein: A voltage stabilizing circuit, whose input terminal inputs a control signal, whose first output terminal and second output terminal are respectively connected to the first terminal and the second terminal of the switch unit, and whose second output terminal is also grounded, and is used to suppress the voltage between the first terminal and the second terminal of the switch unit; A switch unit, wherein a third end thereof is connected to a first end of the load, and a fourth end and a fifth end thereof are connected to a first end and a second end of the arc extinguishing circuit respectively; An arc extinguishing circuit, whose third and fourth ends are connected to the second and third ends of the load respectively, and is used to absorb energy released when the switch unit switches the switch state; When the voltage of the control signal is greater than the grounding point voltage, the switch unit switches the switch state so that the first end and the second end of the load are connected and start working; When the voltage of the control signal is less than or equal to the grounding voltage, the switch unit switches the switch state so that the first terminal and the third terminal of the load are connected and stop working.

2. The switch circuit according to claim 1, characterized in that: The voltage stabilizing circuit includes: a lightning protection circuit and a voltage stabilizing diode, wherein: A lightning protection circuit, a first end of which inputs a control signal, a second end of which is connected to the cathode of the voltage stabilizing diode and the first end of the switch unit, and is used to suppress overvoltage in the circuit; A voltage stabilizing diode, an anode of which is connected to the second end of the switch unit, is used to provide a discharge path for overvoltage in the circuit.

3. The switch circuit according to claim 2, characterized in that: The lightning protection circuit comprises: A varistor, a first end of which inputs a control signal, and a second end of which is connected to the cathode of the voltage-stabilizing diode.

4. The switch circuit according to claim 2, characterized in that: The voltage stabilizing circuit further includes: A light-emitting circuit, whose first end is connected to the first end of the lightning protection circuit and whose second end is connected to the anode of the voltage-stabilizing diode, is used to emit light or extinguish light based on the voltage of the control signal.

5. The switch circuit according to claim 4, characterized in that: The light emitting circuit includes: a light emitting diode and a chip resistor, wherein: A light emitting diode, an anode of which is connected to the first end of the lightning protection circuit, and a cathode of which is connected to the first end of the chip resistor; A chip resistor, a second end of which is connected to the anode of the voltage zener diode; When the voltage of the control signal is greater than the grounding point voltage, the light emitting diode emits light; When the voltage of the control signal is less than or equal to the ground point voltage, the light emitting diode is turned off.

6. The switch circuit according to claim 1, characterized in that: The switch unit comprises: A double-pole double-throw relay, wherein the first end and the second end are respectively connected to the first output end and the second output end of the voltage stabilizing circuit, the third end and the fourth end are both connected to the first end of the load, the fifth end and the sixth end are both connected to the first end of the arc extinguishing circuit, and the seventh end and the eighth end are both connected to the second end of the arc extinguishing circuit; When the voltage of the control signal is greater than the grounding point voltage, the third end of the double-pole double-throw relay is connected to the fifth end, and the fourth end of the double-pole double-throw relay is connected to the sixth end; When the voltage of the control signal is less than or equal to the grounding point voltage, the fourth terminal of the double-pole double-throw relay is connected to the seventh terminal, and the fifth terminal of the double-pole double-throw relay is connected to the eighth terminal.

7. The switch circuit according to claim 1, characterized in that: The arc extinguishing circuit comprises: a first arc extinguishing unit and a second arc extinguishing unit, wherein: The first arc extinguishing unit is connected in series between the fourth end of the switch unit and the second end of the load; The second arc extinguishing unit is connected in series between the fifth end of the switch unit and the third end of the load.

8. The switch circuit according to claim 7, characterized in that: The first arc extinguishing unit and the second arc extinguishing unit both include a first capacitor and a first resistor connected in series.

9. The switch circuit according to claim 1, characterized in that: Also includes: A current limiting resistor is connected in series between the third end of the switch unit and the first end of the load, and is used to limit the magnitude of the current flowing into the first end of the load.

10. An output isolation plate, characterized in that: include: A circuit board, a bus connector, and a plurality of switch circuits according to any one of claims 1 to 9, wherein: The bus connector and all the switch circuits are integrated on the circuit board; The input end of each voltage stabilizing circuit is connected to an output end of the PLC through the bus connector to receive a control signal; The second end of each switch unit is grounded via a grounding point on the bus connector; When any of the voltage stabilizing circuits receives the control signal and the voltage of the control signal is greater than the grounding voltage, the switch unit connected to the voltage stabilizing circuit switches the switch state so that the corresponding load starts working; When any of the voltage stabilizing circuits receives the control signal and the voltage of the control signal is less than or equal to the grounding voltage, the switch unit connected to the voltage stabilizing circuit switches the switch state so that the corresponding load stops working.

Images