A circuit and method for safe static discharge and applications thereof

Abstract

The application relates to the technical field of static electricity release elimination, in particular to a circuit for safely releasing static electricity and application thereof. The circuit comprises a voltage detection unit, a calculation unit and a voltage-controlled resistance unit. The resistance value between the voltage-controlled resistance unit is controlled by the voltage on the control electrode G. One end of the voltage-controlled resistance unit is grounded, and the other end is a static electricity release end. When the static electricity release end touches a static electricity body, the voltage detection unit detects the voltage of the static electricity body. The calculation unit calculates the resistance value according to the detected voltage according to the set parameters. The resistance value is realized by the voltage-controlled resistance unit, so that the static electricity of the static electricity body is safely released quickly under the condition of limited discharge power, or the static electricity of the static electricity body is safely released quickly under the condition of limited discharge current. The beneficial effect is that the static electricity of the static electricity body is safely released quickly under the condition of limited discharge current, so that the requirement of an intrinsically safe product is realized, or the static electricity of the human body is safely released quickly under the condition of limited discharge current, so that the electric shock of the static electricity on the human body is avoided.

Description

Technical Field

[0001] This invention relates to the technical field of static electricity discharge and elimination, and in particular to a circuit for safely discharging static electricity and its application. Background Technology

[0002] Static electricity includes static electricity generated by human movement and static electricity generated by the movement of materials and oils during production. For static electricity from the human body, static discharge balls are used in flammable, explosive, and anti-static environments. Existing static discharge balls are made of stainless steel, with the ball (the touch ball) connected to the ground. When a hand touches the ball, the static electricity from the human body is quickly conducted to the ground. During this process, a discharge spark may be generated the instant the hand touches the ball. This spark is unsafe in flammable and explosive environments, and the human body may also experience an electric shock, causing discomfort. For static electricity generated during production, such as when a fully loaded tanker truck is unloading oil, it carries approximately 2-3 kV of static electricity (tanker trucks typically have a ground capacitance of around 1500 pF, generated through friction between the wheels and the ground). Therefore, static grounding clamps must be used to connect and release the static electricity before unloading. A static spark may be generated the instant the clamps engage the conductor, and this spark can cause harm in an explosive zone.

[0003] To prevent the sudden release of static electricity from a charged object or human body, a resistor can be connected between the charged object and the ground wire. However, the static voltage and capacitance of the charged object are uncertain, so it is difficult to use a fixed resistor to meet the requirements for safe discharge. Summary of the Invention

[0004] Intrinsic safety stems from the fact that, according to the GB3836.4-201 standard, explosion-proof electrical appliances are classified into flameproof, increased safety, and intrinsically safe types. The characteristic of intrinsically safe electrical equipment is that all its circuits are intrinsically safe circuits, meaning that the electrical sparks and thermal effects generated under normal operation or specified fault conditions cannot ignite a specified explosive mixture. In other words, this type of electrical appliance is not protected by its casing or filling material; rather, the energy of the electrical sparks or thermal effects generated by its circuits during normal use or when a fault occurs is less than 0.28 mJ, which is the minimum ignition energy at a gas concentration of 8.5% (the most easily explosive concentration).

[0005] The purpose of this invention is to provide a circuit for safely releasing static electricity. For static electricity release in the human body, the requirement is that it does not produce an electric shock sensation. For static electricity release in safe production, it must meet the intrinsic safety requirements of GB3836.4—201 standard. The energy of the electric spark or thermal effect generated during normal use or in the event of a malfunction is less than 0.28 mJ. This standard only provides the energy value but does not consider the energy release time. The actual process is that the energy released by a unit thermal effect heats a unit mass of substance, Q = C * M * ΔT, where Q is the energy of the thermal effect, M is the mass of the substance, C is the specific heat of the substance, and ΔT is the temperature change. When the maximum value of the temperature change reaches the ignition point of the substance, an explosion occurs. During this process, heat dissipation also occurs (neglected here). Therefore, the indicator for igniting a substance is the energy released per unit time. This invention introduces the concept of ignition power P, which is the instantaneous energy release not exceeding 0.28 mJ, converted to P = 0.28 mJ / s. Through experimental testing, the current that does not produce an electric shock sensation in the human body is not greater than 1 mA. Two parameters are set as follows: 1. The electrostatic discharge current of the human body I <= 1mA. According to Ohm's law, the overcurrent resistance R is R = U / I; the overcurrent resistance in safe production is R = U 2 / P, P <= 0.28 mJ / s (derived from GB3836.4—201 standard, intrinsic safety requires a single discharge energy of less than 0.28 mJ, and the discharge time is less than 1 second, so P <= 0.28 mJ / s is sufficient to cover the intrinsic requirement of a single discharge energy of less than 0.28 mJ). Since the electrostatic voltage and capacitance of the static body are uncertain, and its voltage decreases as the static charge is released (U=Q / C), it is difficult to use a fixed resistance to meet the requirements of safe discharge. Therefore, this case uses a real-time dynamically changing resistance to meet the safe discharge requirements at any given moment, that is, continuously tracking the real-time voltage of the static body and calculating the real-time resistance value that meets the requirements of safe discharge, thus achieving the requirement of rapid and safe release of static electricity.

[0006] The technical solution of this invention is: A circuit for safely releasing static electricity is characterized by comprising a voltage detection unit, a calculation unit, and a voltage-controlled rheostat (VCR) unit. The resistance value across the VCR unit is controlled by the voltage on the control electrode G. One end of the VCR unit is grounded, and the other end is the static electricity release terminal. When the static electricity release terminal touches the static electricity body, the voltage detection unit detects the voltage of the static electricity body, and the calculation unit calculates the resistance value according to the detected voltage and set parameters. The resistance value is realized by the VCR unit, thereby achieving rapid and safe release of static electricity from the static electricity body under a limited discharge power condition, or rapid and safe release of static electricity from the static electricity body under a limited discharge current condition.

[0007] A circuit for safely releasing static electricity is characterized by being made of semiconductor material and including a source (S), a gate (G), a drain (D), a voltage detection unit, and a calculation unit. When the static discharge terminal touches an electrostatic object, the voltage detection unit detects the voltage of the electrostatic object, and the calculation unit calculates the resistance value according to the detected voltage and set parameters. The resistance value is achieved by the gate (G) controlling the resistance between the drain (D) and the source (S). This circuit enables rapid and safe release of static electricity from the electrostatic object under a limited discharge power condition, or rapid and safe release of static electricity from the electrostatic object under a limited discharge current condition.

[0008] A circuit for safely releasing static electricity is characterized by comprising a field-effect transistor, a voltage detection unit, and a calculation unit. When the static discharge terminal touches an electrostatic body, the voltage detection unit detects the voltage of the electrostatic body, and the calculation unit calculates the resistance value according to the detected voltage and set parameters. The resistance value is achieved by controlling the resistance between the drain D and the source S of the field-effect transistor through the gate G. This circuit enables rapid and safe release of static electricity from the electrostatic body under a limited discharge power condition, or rapid and safe release of static electricity from the electrostatic body under a limited discharge current condition.

[0009] The circuit for safely releasing static electricity is characterized in that: the static electricity source is the human body, the calculated resistance value is R=U / I, I<=1mA, U is the real-time voltage of the human body, and I is the set current.

[0010] The circuit for safely releasing static electricity is characterized in that: the static electricity collector is a manufactured object, and the calculated resistance value is R = U. 2 / P, P <= 0.28 mJ / s, U is the real-time voltage of the produced object, and P is the set discharge power.

[0011] The circuit for safely releasing static electricity is characterized in that a resistor of 100 megohms to 1000 megohms is connected between D and S.

[0012] The application of the electrostatic discharge circuit is characterized in that: the electrostatic discharge circuit is installed on the outer casing of the fuel dispenser to release static electricity from the human body.

[0013] The application of the electrostatic discharge circuit is characterized in that: the electrostatic discharge circuit is installed on the nozzle of the fuel dispenser to release static electricity from the human body.

[0014] The application of the electrostatic discharge circuit is characterized in that: the electrostatic discharge circuit is installed on the handle of the refueling nozzle to release static electricity from the human body.

[0015] The application of the electrostatic discharge circuit is characterized in that: the electrostatic discharge circuit is installed on the door handle to release static electricity from the human body.

[0016] The application of the electrostatic discharge circuit is characterized in that: the electrostatic discharge circuit is set in the electrostatic discharge ball circuit to release static electricity from the human body.

[0017] The application of the electrostatic discharge circuit is characterized in that: the electrostatic discharge circuit is installed in the electrostatic grounding clamp to release the static electricity of the production object.

[0018] A method for safely releasing static electricity via a circuit, characterized by comprising the following steps: Set parameter I, (1) The voltage detection unit detects the real-time voltage U of the human body; (2) The calculation unit performs resistance calculation, R=U / I, where U is the real-time voltage of the human body and I is the set current; (3) The voltage-controlled variable resistor unit realizes the resistance value R; (4) Execute steps (1) to (3) continuously with a period of T.

[0019] Furthermore, the parameter I is set to be less than or equal to 1 mA.

[0020] A method for safely releasing static electricity via a circuit, characterized by comprising the following steps: Set parameter P, (1) The voltage detection unit detects the real-time voltage U of the electrostatic body; (2) The calculation unit performs the resistance calculation, R = U 2 / P, U is the real-time voltage of the electrostatic body, and P is the set power; (3) The voltage-controlled variable resistor unit realizes the resistance value R; (4) Execute steps (1) to (3) continuously with a period of T.

[0021] Furthermore, the parameter P is set to be less than or equal to 0.28 mJ / s.

[0022] The beneficial effects of this invention are: to quickly and safely release the static electricity of the electrostatic body under limited discharge power conditions to achieve the requirements of intrinsically safe products, or to quickly and safely release the static electricity of the human body under limited discharge current conditions to avoid electric shock to the human body. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the invention.

[0024] Figure 2 This is a circuit diagram of the field-effect transistor used in this invention.

[0025] Figure 3 This is a schematic diagram illustrating the time-varying electrostatic discharge voltage of the present invention.

[0026] Figure 4 This is a flowchart of the present invention.

[0027] Figure 5 This is an embodiment of the present invention applied to electrostatic grounding clamps.

[0028] Figure 6 This is an implementation scheme of the present invention applied to a gas station.

[0029] Figure 7 This is an embodiment of the invention applied to a refueling nozzle.

[0030] Figure 8 This is an embodiment of the invention applied to a door handle.

[0031] Figure 9 This is an embodiment of the present invention applied to an electrostatic release ball. Detailed Implementation

[0032] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0033] Figure 1 The schematic diagram of this invention shows that circuit 1000 includes a voltage-controlled rheostat 101, a voltage detection unit 103, and a calculation unit 104. The resistance across the voltage-controlled rheostat 101 is controlled by the voltage on the control electrode G. One end of the voltage-controlled rheostat is grounded, and the other end is an electrostatic discharge terminal 102. When an electrostatic object (an object or person carrying static electricity) touches the electrostatic discharge terminal 102, the voltage detection unit continuously detects the voltage U of the electrostatic object at a period T. The calculation unit 104 calculates the resistance value R of the voltage-controlled rheostat 101 based on the real-time voltage U. The resistance value R is determined by set parameters. When the electrostatic object is a human body, to avoid the electric shock sensation caused by electrostatic current, the resistance value is R = U / I, where I <= 1mA, U is the real-time voltage of the human body, and I is the set current. When the electrostatic object is a production object, to avoid the explosion of flammable gas caused by electrostatic energy, the resistance value is R = U / I. 2 / P, P ≤ 0.28 mJ / s, U is the real-time voltage of the produced object, P is the set power, and the electrostatic discharge is achieved through the voltage-controlled rheostat device 101 to quickly and safely release the electrostatic charge under a limited discharge current condition, or to quickly and safely release the electrostatic charge under a limited discharge power condition. The present invention can be implemented at the chip level or as a device. Chip-level implementation means directly fabricating a voltage-controlled rheostat module or chip using semiconductor technology.

[0034] Figure 2The circuit diagram of this invention using a field-effect transistor includes a field-effect transistor, a voltage detection unit 103, and a calculation unit 104. The voltage detection unit 103 continuously detects the charged voltage U of the electrostatic material at a period T. The calculation unit 104 calculates the resistance value R of the field-effect transistor based on the real-time voltage U. The resistance value R is determined by set parameters. When the electrostatic material is a human body, to avoid the electric shock sensation caused by electrostatic current, the resistance value is R = U / I, where I <= 1mA, U is the real-time voltage of the human body, and I is the set current. When the electrostatic material is a production object, to avoid the explosion of flammable gas caused by electrostatic energy, the resistance value is R = U / I. 2 / P, P <= 0.28 mJ / s, U is the real-time voltage of the produced object, P is the set power, and the electrostatic discharge is achieved through the field-effect transistor to quickly and safely release the electrostatic charge under a limited discharge current condition, or under a limited discharge power condition. The figure shows an N-MOS transistor, and the same logic can be applied to a P-MOS transistor. When the source metal of the field-effect transistor is connected to the substrate, the source and drain can be used interchangeably with little change in characteristics. The source and drain of the field-effect transistor are symmetrical in structure and can be used interchangeably. The gate-source voltage of a depletion-type MOS transistor can be positive or negative.

[0035] Figure 3 This diagram illustrates the voltage-time variation of the electrostatic discharge system according to the present invention. The electrostatic discharge follows an RC discharge curve. Assuming constant resistance, the curve conforms to curve a, where the initial current is high, the voltage drops rapidly, and then the discharge remains stable for a relatively long period. If the variable resistance discharge of the present invention is used, the curve conforms to curve b. Assuming the resistance in the first cycle is R1, the voltage detected by the voltage detection unit in the second cycle is always lower than the voltage in the first cycle. Therefore, the resistance R2 in the second cycle is always lower than R1. After multiple cycles, the electrostatic voltage drops rapidly, ideally to zero. For example, the capacitance of a human body is typically 200pF. Assuming the static electricity of a human body is 10000V, to avoid electric shock, we take I = 1mA, R = U / I = 10000V / 1mA = 10 megohms. According to the RC discharge curve, it takes more than 8 seconds to completely release the human body voltage (with residual voltage). If the variable resistance discharge of the present invention is used, the static electricity can be completely released in 2 seconds.

[0036] Figure 4 The flowchart of this invention, for which there is no electric shock-inducing discharge requirement for the human body, includes the following steps: Set parameter I <= 1mA, (1) The voltage detection unit detects the real-time voltage U of the human body; (2) The calculation unit performs resistance calculation, R=U / I, where U is the real-time voltage of the human body and I is the set current; (3) The voltage-controlled variable resistor unit realizes the resistance value R; (4) Execute steps (1) to (3) continuously with a period of T.

[0037] The discharge requirements for explosion-proof and safe production include the following steps: Set parameter P <= 0.28 mJ / s. (1) The voltage detection unit detects the real-time voltage U of the electrostatic body; (2) The calculation unit performs the resistance calculation, R = U 2 / P, U is the real-time voltage of the electrostatic body, and P is the set power; (3) The voltage-controlled variable resistor unit realizes the resistance value R; (4) Execute steps (1) to (3) continuously with a period of T.

[0038] The choice of period T: A smaller period T is closer to the ideal value for electrostatic discharge, but a smaller period T also consumes more computational resources and places higher demands on the specifications of the circuit components. For electrostatic bodies with larger capacitance, a longer period T can be used due to the larger amount of static electricity carried, where 0 seconds < T <= 5 seconds. Of course, this period cannot limit the technical features of this application.

[0039] Figure 5 This invention relates to an implementation scheme for an electrostatic grounding clamp. One application case for production safety is the electrostatic grounding clamp. Before loading and unloading oil in oil tankers and oil depots, a grounding connection must be performed between the two parties. Existing grounding clamps have safety hazards because electric sparks may be generated when the grounding clamp engages the conductor, which is unsafe in explosion-proof areas. Therefore, one application of this invention is to connect the circuit 1000 of this invention in series between the oil tanker and the oil depot through the electrostatic grounding clamp. When the electrostatic grounding clamp engages the oil tanker, the circuit 1000 of this invention detects the electrostatic voltage of the oil tanker, calculates the safe overcurrent resistance of the electrostatic discharge after obtaining the electrostatic voltage value, and performs electrostatic discharge. This process is continuously and dynamically performed to achieve rapid and safe discharge of electrostatic discharge.

[0040] Figure 6 In an embodiment of the invention applied to a gas station, 801 is a fuel dispenser, and 803 is a fuel nozzle. The device 802 of the invention is installed on the metal casing of the fuel dispenser to release static electricity from the human body. Additionally, existing self-service fuel dispensers have a grounded metal keyboard 804; static sparks may occur when fingers touch the keyboard. Therefore, the device of the invention can be installed on this keyboard. Of course, the product of the invention can be made into a chip or embedded in a circuit.

[0041] Figure 7 In an embodiment of the present invention applied to a refueling nozzle, the circuit or chip 1000 of the present invention is provided on the refueling nozzle 803, which can be provided on the nozzle 902 or on the handle 901.

[0042] Figure 8In the embodiment of the present invention applied to door handles, considering that people's hands are often shocked by static electricity when touching door handles in winter, the circuit 1000 of the present invention is set on the door handle 1001 to prevent people from being shocked by static electricity. Door handles naturally include car door handles.

[0043] Figure 9 In the embodiment of the present invention applied to the electrostatic release ball, 2000 is the touch ball of the electrostatic release ball, and the electrostatic release terminal 102 of the circuit 1000 of the present invention is connected to the touch ball, so that human body static electricity is released by touching it with a human hand.

[0044] Currently, static electricity elimination in the human body uses static discharge balls. However, since these balls are made of metal, touching them with a finger may generate static sparks, posing a safety hazard in flammable and explosive environments, and also causing an electric shock. Other methods use touch balls made of sub-conductive materials (industry standard SY / T7354-2017, resistance 10 megohms to 1000 megohms) to reduce the instantaneous static discharge energy and decrease the electric shock sensation. However, this requires extending the static discharge time, and due to the resistance, it cannot completely release the static electricity carried by the human body. The circuit of this invention can achieve complete static electricity discharge from the human body without static sparks or electric shock sensation.

[0045] The circuit of this invention can be installed in any place where static electricity needs to be released, such as car doors, explosion-proof equipment, instruments, etc.

[0046] In addition, a glow discharge tube can be installed in the electrostatic discharge circuit to indicate the electrostatic discharge process (if explosion-proof requirements are met, such as using an explosion-proof neon bubble).

[0047] The above application modes and rules do not limit the basic features of the method and application of the present invention, nor do they limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A circuit for safely releasing static electricity, characterized in that: It includes a voltage detection unit, a calculation unit, and a field-effect transistor (FET). The resistance value across the FET is controlled by the voltage on the control electrode G. One end of the FET is grounded, and the other end is an electrostatic discharge terminal. When the electrostatic discharge terminal touches an electrostatic object, the voltage detection unit detects the voltage of the electrostatic object, and the calculation unit calculates the resistance value according to the detected voltage and set parameters. The resistance value is realized by the FET, enabling rapid and safe release of the electrostatic object under a limited discharge power condition, or rapid and safe release of the electrostatic object under a limited discharge current condition.

2. The circuit for safely releasing static electricity according to claim 1, characterized in that: The electrostatic body is the human body, and the calculated resistance value is R=U / I, I≤1mA, where U is the real-time voltage of the human body and I is the set current.

3. The circuit for safely releasing static electricity according to claim 1, characterized in that: The calculated resistance value is R = U 2 / P, P≤0.28mJ / s, U is the real-time voltage of the electrostatic body, and P is the set discharge power.

4. The application of the circuit for safely releasing static electricity according to any one of claims 1 to 3 in the safe release of static electricity, characterized in that: An electrostatic discharge circuit is installed on the outer casing of the fuel dispenser to discharge static electricity from the human body. Alternatively, an electrostatic discharge circuit may be installed on the nozzle of the fuel dispenser to release static electricity from the human body. Alternatively, an electrostatic discharge circuit may be installed on the handle of the fuel nozzle to release static electricity from the human body; Alternatively, an electrostatic discharge circuit may be installed on the door handle to release static electricity from the human body; Alternatively, an electrostatic discharge circuit may be installed in the electrostatic discharge ball circuit to release static electricity from the human body; Alternatively, an electrostatic discharge circuit may be installed in the electrostatic grounding clamp to release the static electricity of the object.

5. A method for safely releasing static electricity, comprising employing the circuit for safely releasing static electricity as described in any one of claims 1-2, characterized in that, Includes the following steps: Set parameter I≤1mA, (1) Detect the real-time voltage U of the human body; (2) Calculate the resistance value: R=U / I, where U is the real-time voltage of the human body and I is the set current; (3) The voltage-controlled variable resistor unit realizes the resistance value R; (4) Execute steps (1) to (3) continuously with a period of T.

6. The method for safely releasing static electricity according to claim 5, characterized in that: 0 seconds < T ≤ 5 seconds.

7. A method for safely releasing static electricity, comprising employing the circuit for safely releasing static electricity as described in any one of claims 1-2, characterized in that, Includes the following steps: Set parameter P≤0.28mJ / s, (1) Detect the real-time voltage U of the electrostatic body; (2) Calculate the resistance value, R = U 2 / P, U is the real-time voltage of the electrostatic body, and P is the set power; (3) The voltage-controlled variable resistor unit realizes the resistance value R; (4) Execute steps (1) to (3) continuously with a period of T.

8. The method for safely releasing static electricity according to claim 7, characterized in that: 0 seconds < T ≤ 5 seconds.

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