Anti-arcing low-leakage-current switching circuit and sequential control method thereof

Abstract

The invention provides an anti-arcing low-leakage-current switching circuit and a sequential control method thereof, the switching circuit comprises electromagnetic switches S1 and S2 and an electronic switch S3, the S2 and the S3 are connected in parallel and then are connected in series with the S1, and a control part is integrated in an RTU and is controlled by an MCU. When the switch is switched on, S1 is switched off according to the sequence of S1 to S3-S2 and after S2 is switched on; and the turn-off is performed according to the sequence of S3-S2-S3-S1. S1 and S2 can be electromagnetic relays, and S3 consists of Q1 and Q2, can be an NMOS (N-channel Metal Oxide Semiconductor) tube or an IGBT (Insulated Gate Bipolar Translator), and can be connected with a diode in parallel. The time sequence control comprises the time delay of each turn-on and turn-off step. The method solves the problems of arc discharge of an electromagnetic switch and current leakage of an electronic switch, and can be applied to the fields of energy-saving control of urban pipe network flow storage type flow measurement equipment and the like.

Description

Technical Field

[0001] The invention relates to the technical field of electronic switches, and in particular to an arc-proof low-leakage current switch circuit and a timing control method thereof. Background Art

[0002] In the field of electronic applications, switch technology is widely used, among which electromagnetic switches and semiconductor electronic switches are two common types.

[0003] Electromagnetic switches have obvious defects when working under inductive loads. When the circuit is disconnected, arcing is likely to occur due to the characteristics of inductive loads. Arcing not only damages the switch itself and reduces its service life, but may also cause safety hazards, such as generating electric sparks that cause flammable materials in the surrounding environment to burn.

[0004] On the other hand, although conventional semiconductor electronic switches have advantages in some aspects, they also have the problem of leakage current. Leakage current may lead to waste of electric energy and may cause safety problems such as electric shock in some application scenarios with high safety requirements.

[0005] In order to solve the above problems, the present invention combines the characteristics of electromagnetic switches and electronic switches to design a low-leakage arc-resistant switch and a timing control method thereof, which is intended to be applied to fields such as energy-saving control of current storage type flow measuring equipment in urban pipeline networks, so as to achieve efficient and safe switching control of AC and DC power supplies and loads. Summary of the invention

[0006] The embodiment of the present invention provides an arc-proof and low-leakage current switch circuit and a timing control method thereof, in order to solve the problems that the electromagnetic switch in the current technology is prone to arcing when disconnected under an inductive load, and the conventional semiconductor electronic switch has a leakage current problem, which leads to reduced safety and reliability and energy waste.

[0007] The core technology of the present invention is mainly to combine the characteristics of electromagnetic switches and electronic switches, and realize arc prevention and low leakage current through a specific switch circuit composition and a timing control method performed by an MCU.

[0008] In a first aspect, the present invention provides an arc-proof and low-leakage current switch circuit, comprising: The switch part includes an electromagnetic switch S1 and an electromagnetic switch S2 with mechanical contacts and an electronic switch S3 without contacts. The electromagnetic switch S2 and the electronic switch S3 are connected in parallel and then in series with the electromagnetic switch S1. A control unit, integrated in the remote terminal unit, controls the on and off of each switch of the switch unit through the MCU of the control unit; Among them, the timing logic recorded inside the MCU includes: When turned on, after the electromagnetic switch S1 is turned on, the electronic switch S3 and the electromagnetic switch S2 are turned on in sequence, and when the electromagnetic switch S2 is turned on, the electromagnetic switch S1 is turned off; When shutting down, after the electronic switch S3 is closed, the electromagnetic switch S2, the electronic switch S3 and the electromagnetic switch S1 are opened in sequence.

[0009] Furthermore, the electromagnetic switch S1 and the electromagnetic switch S2 are electromagnetic relays.

[0010] Furthermore, the electronic switch S3 is composed of two transistors Q1 and Q2.

[0011] Furthermore, the two transistors of the electronic switch S3 are respectively connected in parallel with a body diode D1 and a body diode D2.

[0012] Furthermore, the two transistors are respectively an NMOS transistor Q1 and an NMOS transistor Q2 or an insulated gate bipolar transistor Q1 and an insulated gate bipolar transistor Q2.

[0013] In a second aspect, the present invention provides a timing control method for a switch circuit with arc protection and low leakage current, comprising the following steps: When turned on, the MCU controls the electromagnetic switch S1 to turn on, delaying ΔT ON 1. Then control the electronic switch S3 to turn on, delay ΔT ON 2. Continue to turn on the electromagnetic switch S2, delay ΔT ON 3. Finally, disconnect the electronic switch S3; When shutting down, MCU controls the electronic switch S3 to turn on, delaying ΔT OFF 1. Then control the electromagnetic switch S2 to disconnect, delay ΔT OFF 2. Continue to disconnect the electronic switch S3, delay ΔT OFF 3. Finally, disconnect the electromagnetic switch S1; Where, ΔT ON 1 is the establishment time of electromagnetic switch S1, ΔT ON 2 is the load stabilization time, ΔT ON 3 is the establishment time of electromagnetic switch S2, ΔT OFF 1 is the conduction time of the electronic switch S3, ΔT OFF 2 is the tripping time of electromagnetic switch S1, ΔT OFF 3 is the tripping time of electromagnetic switch S2.

[0014] The main contributions and innovations of the present invention are as follows: 1. Unique circuit structure design A new switch circuit structure composed of an electromagnetic switch and an electronic switch is proposed, that is, the electromagnetic switch S2 and the electronic switch S3 are connected in parallel and then connected in series with the electromagnetic switch S1. This structure fully utilizes the advantages of the electromagnetic switch and the electronic switch.

[0015] 2. Advanced timing control method A precise timing control method is designed by MCU to strictly control the switch on and off sequence and delay. When turning on, each switch is turned on in a specific order and some switches are turned off at the right time. When turning off, it is also operated in a specific order. This timing control method is the key to achieve arc prevention and low leakage current.

[0016] 3. Flexible device selection In the circuit implementation, there is flexibility in the selection of devices that constitute the electronic switch and the electromagnetic switch. The electronic switch can select NMOS tubes or IGBTs according to different application scenarios, and the electromagnetic switch can select electromagnetic relays. This flexible selection method can better adapt to various practical application requirements.

[0017] The details of one or more embodiments of the invention are set forth in the following drawings and description so that other features, objects, and advantages of the invention are more readily apparent. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings: Figure 1 is a schematic diagram of a switch circuit with arc-proof and low leakage current according to an embodiment of the present invention; Figure 2 is a circuit diagram of a switch portion of a switch circuit with arc-proof and low leakage current according to an embodiment of the present invention; Figure 3 It is a basic flow chart of a timing control method for a switch circuit with arc protection and low leakage current according to an embodiment of the present invention; Figure 4 It is a voltage waveform diagram between mechanical contacts when the prior art relay is directly used as a switch; Figure 5 It is a leading edge waveform diagram of S1 when the electromagnetic switch S1 in the embodiment of the present invention is turned off; Figure 6 It is a waveform diagram of the trailing edge of S1 when the electromagnetic switch S1 is turned on in the embodiment of the present invention; Figure 7 is a leading edge waveform diagram of S2 when the electromagnetic switch S2 in the embodiment of the present invention is turned off; Figure 8It is a waveform diagram of the trailing edge of S2 when the electromagnetic switch S2 is turned on in the embodiment of the present invention. DETAILED DESCRIPTION

[0019] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The implementations described in the following exemplary embodiments do not represent all implementations consistent with one or more embodiments of this specification. Instead, they are merely examples of devices and methods consistent with some aspects of one or more embodiments of this specification as detailed in the appended claims.

[0020] It should be noted that: in other embodiments, the steps of the corresponding method are not necessarily performed in the order shown and described in this specification. In some other embodiments, the steps included in the method may be more or less than those described in this specification. In addition, a single step described in this specification may be decomposed into multiple steps for description in other embodiments; and multiple steps described in this specification may be combined into a single step for description in other embodiments.

[0021] Electromagnetic switches are prone to arcing when disconnected under inductive loads, while conventional semiconductor electronic switches have leakage current problems, which in turn cause safety issues.

[0022] Based on this, the present invention solves the problems existing in the prior art based on the characteristics of mechanical contacts and contactless switches.

[0023] Embodiment 1 The present invention aims to provide a switch circuit with arc protection and low leakage current, specifically, referring to Figure 1 and Figure 2 , the circuit comprising: The switch part and the control part, wherein the control part can be integrated in the RTU (Remote Terminal Unit) and controlled by the MCU inside the RTU. The power module belongs to the existing technology and is used to provide electric energy, so it will not be described in detail.

[0024] The switch part consists of 2 electromagnetic switches (mechanical contacts) and 1 electronic switch (no contact), such as Figure 1 As shown, the electromagnetic switch S2 and the electronic switch S3 are connected in parallel, and the combination is connected in series with the electromagnetic switch S1. Figure 1 The part above the dotted line is the switch part, and the part below the dotted line is the control part, namely the RTU part and the power module. The purpose of the dotted line is to distinguish the two.

[0025] Among them, Figure 2In the application case shown, according to the load requirements, S1 and S2 are selected as electromagnetic relays, Q1 and Q2 are NMOS tubes with low on-resistance, and D1 and D2 can be realized by using the body diode inside the MOS tube under normal circumstances. In high-voltage and high-current applications, Q1 and Q2 can be realized by IGBT.

[0026] In this embodiment, the NMOS (N-Metal-Oxide-Semiconductor) tube is a metal-oxide-semiconductor field effect transistor. It is a voltage-controlled device that controls the current conduction between the source and the drain by applying a voltage to the gate. When a suitable positive voltage is applied to the gate, a conductive channel is formed on the semiconductor surface below the gate, allowing electrons to flow from the source to the drain, thereby achieving current conduction.

[0027] IGBT (Insulated Gate Bipolar Transistor) is an insulated gate bipolar transistor. It is a composite power semiconductor device that combines the advantages of MOSFET (metal-oxide-semiconductor field-effect transistor) and BJT (bipolar junction transistor). IGBT has both the high input impedance and voltage control characteristics of MOSFET and the low on-resistance and high current carrying capacity of BJT. It performs well in high-voltage and high-current applications, such as inverters, frequency converters, motor drives and other fields in power electronic equipment, and can achieve efficient power conversion and control.

[0028] In this embodiment, RTU is the abbreviation of Remote Terminal Unit, i.e., remote terminal unit. In the present invention, the control part can be integrated in the RTU and controlled by the MCU inside the RTU. It is a device that can receive remote control instructions and control and monitor local devices (such as the switch part in the present invention), and is commonly used in the fields of industrial automation, remote monitoring systems, etc. The RTU in this solution has a built-in MCU and a power module, and the various switches of the switch part are controlled by the timing control logic stored in the MCU.

[0029] In this embodiment, the characteristics of mechanical contacts and contactless switches are utilized, and the advantages of both are fully utilized through the timing control of on or off.

[0030] When opening, the opening sequence is controlled: S1-S3-S2, that is, S1 is opened first, then S3, after S3 is turned on, S2 is turned on, after S2 is turned on, S3 is disconnected to complete the opening action. Through the above actions, during the conduction stage, the damage to the contacts caused by the impact current during the establishment of the mechanical contacts is reduced. After steady state, the mechanical contact switch of the electromagnetic switch performs conduction, reducing the conduction loss.

[0031] When shutting down, the shutdown action is completed by controlling the shutdown sequence: first S3 is closed, and then S2, S3, and S1 are opened in sequence. Through the above actions, arcing caused by the disconnection of the switch under the inductive load is avoided.

[0032] The MCU works in a cyclic detection state. When a change in the switch control signal is detected, the on or off process is executed. The on and off delay sequence can be fixed in the MCU by software.

[0033] Embodiment 2 like Figure 3 As shown, based on the same concept, the present invention also proposes a timing control method for a switch circuit with arc protection and low leakage current, comprising: When turned on, the control relay K1 makes the normally open contact S1 conduct, delaying ΔT ON 1, the electronic switch S3 composed of Q1 and Q2 is controlled to conduct, delaying ΔT ON 2, the relay K2 is controlled to close the normally open contact S2, delaying ΔT ON 3. After that, the electronic switch is controlled to be turned off, and the load is completely powered by the mechanical contacts; When the shutdown command is executed, the electronic switch S3 composed of Q1 and Q2 is controlled to turn on, delaying ΔT OFF 1, control relay K2, make the normally open contact in the normally open state, delay ΔT OFF 2, the electronic switch S3 composed of Q1 and Q2 is controlled to turn off, delaying ΔT OFF 3, the relay K1 is controlled so that the normally open contact is in the normally open state, thus completing the shutdown operation.

[0034] Among them, the delay of the timing control can be selected according to the on-off characteristics of the selected device, and its purpose is to provide a stable switch establishment time, as shown in Table 1 below: Table 1

[0035] In this embodiment, during the actual implementation: In this case, in a 24V power supply system, the load uses a 1.2mH inductor and a 22 ohm capacitor in series. When the existing technology uses a relay as the switch, Figure 4 As shown in the figure, when the relay is turned off, oscillation occurs at both ends of the switch due to the inductive load, and the peak value reaches more than 400V.

[0036] Using the method of the present invention, under the same load condition, the voltage between the switch contacts S1 and S2 is monitored, such as Figure 5-Figure 8As shown in the figure, through experimental comparison, when using this method, no obvious peaks and oscillations appear during turn-on and turn-off, so this method can eliminate the voltage stress directly generated on the mechanical switch. (Note: Figure 5-Figure 8 The sawtooth voltage when the switch is turned off is generated when the two ends of the mechanical switch are suspended when the switch is turned off. This is convenient for observing the time points of opening and closing.)

[0037] In summary, the application scenarios of the present invention may include the following aspects: 1. Energy-saving control of flow storage flow measurement equipment in urban pipe networks The low leakage anti-arc switch designed by the present invention can be applied to energy-saving control of current storage type current measuring equipment in urban pipe networks. In such equipment, by controlling the switch action, the switch control of AC and DC power supply and load is realized, and the service life of the switch is increased, the maintenance cost is reduced, and the use scenarios of the switch are expanded at a low cost while ensuring the insulation requirements.

[0038] 2. Industrial automation For some equipment on industrial automation production lines, there may be inductive loads, such as motors, etc. The arc-proof low leakage current switch of this solution can be used for circuit control of these equipment to avoid switch arcing and leakage current problems, improve the safety and reliability of equipment operation, and reduce production line downtime caused by switch failures, thereby improving production efficiency.

[0039] 3. Intelligent building electrical system In smart buildings, there are many electrical devices that need to be switched on and off, such as lighting systems, air conditioning systems, etc. These devices may have inductive loads, and this switch solution can be applied to them to achieve efficient and safe switch control, reduce energy consumption, and improve the overall performance of the building electrical system.

[0040] 4. New energy power generation and energy storage system In the field of renewable energy power generation, such as solar photovoltaic power generation systems, wind power generation systems, and energy storage systems, a large number of circuit switch controls may be involved. The switch of this solution can effectively solve the problems of arcing and leakage current, improve the stability and safety of the system, and ensure the efficient use and storage of renewable energy.

[0041] Those skilled in the art should understand that the technical features of the above embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0042] The above embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present invention. It should be pointed out that, for those of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the attached claims.

Claims

1. A switch circuit with arc prevention and low leakage current, characterized in that: include: The switch part includes an electromagnetic switch S1 and an electromagnetic switch S2 with mechanical contacts and a contactless electronic switch S3, wherein the electromagnetic switch S2 and the electronic switch S3 are connected in parallel and then connected in series with the electromagnetic switch S1; A control unit, integrated in the remote terminal unit, controls the on and off of each switch of the switch unit through the MCU of the control unit; Among them, the timing logic recorded inside the MCU includes: When turned on, after the electromagnetic switch S1 is turned on, the electronic switch S3 and the electromagnetic switch S2 are turned on in sequence, and when the electromagnetic switch S2 is turned on, the electromagnetic switch S1 is turned off; During shutdown, after the electronic switch S3 is closed, the electromagnetic switch S2, the electronic switch S3 and the electromagnetic switch S1 are opened in sequence.

2. The arc-proof and low-leakage current switch circuit according to claim 1, characterized in that: The electromagnetic switch S1 and the electromagnetic switch S2 are electromagnetic relays.

3. The arc-proof and low-leakage current switch circuit according to claim 1 or 2, characterized in that: The electronic switch S3 is composed of two transistors Q1 and Q2.

4. The arc-proof and low-leakage current switch circuit according to claim 3, characterized in that: The two transistors of the electronic switch S3 are respectively connected in parallel with a body diode D1 and a body diode D2.

5. The arc-proof and low-leakage current switch circuit according to claim 4, characterized in that: The two transistors are respectively an NMOS transistor Q1 and an NMOS transistor Q2 or an insulated gate bipolar transistor Q1 and an insulated gate bipolar transistor Q2.

6. A timing control method for an arc-proof and low-leakage current switch circuit according to any one of claims 1 to 5, characterized in that: The following steps are involved: When turned on, the MCU controls the electromagnetic switch S1 to turn on, delaying ΔT ON 1. Then control the electronic switch S3 to turn on, delay ΔT ON 2. Continue to turn on the electromagnetic switch S2, delay ΔT ON 3. Finally, disconnect the electronic switch S3; When shutting down, MCU controls the electronic switch S3 to turn on, delaying ΔT OFF 1. Then control the electromagnetic switch S2 to disconnect, delay ΔT OFF 2. Continue to disconnect the electronic switch S3, delay ΔT OFF 3. Finally, disconnect the electromagnetic switch S1; Where, ΔT ON 1 is the establishment time of electromagnetic switch S1, ΔT ON 2 is the load stabilization time, ΔT ON 3 is the establishment time of electromagnetic switch S2, ΔT OFF 1 is the conduction time of the electronic switch S3, ΔT OFF 2 is the tripping time of electromagnetic switch S1, ΔT OFF 3 is the tripping time of electromagnetic switch S2.

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