JPH09285004A - Reverse current blocking device through grounding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To block a reverse current from ground to the common grounding terminal of an apparatus or equipment and to prevent the failure of or damage to the apparatus or equipment caused by the reverse current. SOLUTION: A voltage detecting part 10 detects a forward voltage generated between a common grounding terminal and a grounding. When the detected voltage satisfies a voltage set by an operating voltage setting part 20 and exceeds an internal reference voltage, a control voltage is given from a control voltage generating part 30 to the Gate G of an SCR 4a in a switching part 40 to turn on the SCR 4a. This makes a current flow from the common grounding terminal to the grounding to protect an apparatus. If a current caused by a thunderbolt, etc., flows on the ground and a reverse voltage is applied between the common grounding terminal and the grounding, the control voltage is not applied to the Gate G of the SCR 4a and by making use of the phenomenon that a reverse voltage is applied between the anode A and cathode K, the SCR 4a is turned off to isolate the common grounding terminal and the grounding for the prevention of the phenomenon of the reverse current.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for preventing backflow of current through earth ground, and more specifically, in various equipment or facilities in which a common ground wire is connected to the earth ground, the current from the earth ground to the equipment or facility is reduced. The present invention relates to a device for preventing backflow of current through earth ground to prevent equipment or equipment from being damaged or damaged by backflow.

[0002]

2. Description of the Related Art Earth grounding used by connecting to various electronic / communication equipment or equipment is to connect a common ground wire of the equipment or equipment to the ground to prevent lightning (thunder) or abnormal voltage (noise component) from coming to the ground. It is for escape and removal. Such earth grounding is not limited to a single location, but in the case of equipment such as a telephone system that is used in a wide range, for example, in a nationwide range, the equipment or equipment is connected to each equipment individually and used. Will be provided with a grounding point.

In such a wide range of equipment, when each ground point is not maintained at the same potential, a phenomenon occurs in which a current flows from a ground point having a high potential to a ground point having a low potential in another region. Will be done.
When a current flows from a ground point with a high potential to a ground point with a low potential, at the ground point with a low potential, the device is grounded, as opposed to the normal current flow from the common ground line to the ground. Alternatively, a backflow phenomenon occurs in which a current flows to the common ground end of the equipment, and there is a risk of damaging the equipment or equipment or causing an inoperable state depending on the backflow current level. Other factors that cause the above-mentioned current backflow phenomenon include contact of the power transmission line with the ground due to a landfall or lightning strike,
Another example is when lightning strikes the ground.

[0004]

As described above, in the above-described conventional grounding of equipment or facilities, the emphasis is placed only on the point where abnormal current escapes from the common grounding end of the equipment or facility toward the ground. Because there was a lack of consideration to prevent backflow current to the common ground end of the equipment,
There is a problem that there is a high risk that the device or the equipment will be damaged or fall into an inoperable state due to the reverse current.

The present invention solves the above problems, and in various types of equipment or facilities, a current is quickly passed from the equipment or equipment side toward the ground, while a reverse current flowing from the ground to the equipment or equipment side is ensured. It is an object of the present invention to provide a device for preventing backflow of current through earth ground, which can prevent a failure or damage of equipment or facilities due to backflow current.

[0006]

SUMMARY OF THE INVENTION The present invention compares a voltage detection means for detecting a voltage generated at a common ground end of equipment or equipment with a detection voltage of the voltage detection means with a reference voltage,
Control voltage generating means for outputting a control voltage according to the comparison result, and a control voltage output from the control voltage generating means for a voltage drop in the forward direction in which the common ground terminal has a higher potential than the ground. Based on this, switching control is performed so as to connect between the common ground end and the earth ground, and the common ground end and the earth ground are cut off against a voltage drop in a direction opposite to the forward voltage drop. And a switching means that is switching-controlled.

Preferably, the present invention is characterized by further comprising operating voltage setting means for setting a threshold voltage for selecting the voltage detected by the voltage detecting means as a comparison voltage with the reference voltage.

In the present invention, the voltage detecting means is
Resistors (R12) and (R14) for limiting a current flowing between the common ground terminal and the earth ground;
12) and (R14), a diode (D3) connected in the forward direction, the diode (D3) and the resistor (R1).
4) Smoothing capacitors (C3) and (C) connected between
4).

Further, in the present invention, the switching means is connected between the common ground end and the earth ground and controls the forward voltage drop in which the common ground end is higher in potential than the earth ground. It is characterized in that it includes a high-speed switching element (4a) which is turned on based on the control voltage output from the voltage generating means, and turned off for the voltage drop in the direction opposite to the voltage drop in the forward direction.

The switching element (4a) is SC
It is characterized by being R.

In the present invention, the operating voltage setting means is composed of a variable resistor (VR) and a resistor (R1) which variably adjust the threshold voltage by dividing the detection voltage of the voltage detecting means. Characterize.

[0012]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a schematic configuration diagram of a communication system to which the current backflow prevention device according to the present invention is applied. As shown in the figure, regarding the operation of the current backflow prevention device of the present invention, the current backflow prevention devices 100a, 100b, ~, 100n are individually provided to each of the plurality of communication devices 200a, 200b, ~, 200n that are distributed. [See FIG. 1 (a)] and a method of arranging one current backflow prevention device 100 for the communication devices 200a, 200b, ..., 200n [see FIG. 1 (b)].
There is.

FIG. 2 is a block diagram showing a functional configuration of the current backflow prevention device of the present invention which is operated in each of the above arrangement modes. The current backflow prevention device 100 of the present invention includes a voltage detection unit 1.
0, an operating voltage setting unit 20, a control voltage generating unit 30, and a switching unit 40.
a, 200b, ..., 200n are connected and operated between the common ground terminal and the ground.

The voltage detector 10 detects the voltage generated at the common ground terminal. The operating voltage setting unit 20 includes the voltage detecting unit 1
For the voltage detected by 0, the operating voltage for determining whether to operate the device 100 is set. The control voltage generation unit 30 compares the detection voltage of the voltage detection unit 10 exceeding the operating voltage set by the operation voltage setting unit 20 with the internal reference voltage, and generates the control voltage according to the comparison result. The switching unit 40 includes a high-speed switching element connected between a common ground terminal and a ground, and ON / OFF-controls the high-speed switching element based on the control voltage output from the control voltage generating unit 30. Thus, it operates so as to connect or disconnect between the common ground end and the ground.

In the current backflow prevention device 100, when an abnormal voltage such as a noise voltage is generated at the common ground end of the communication device 200 and the potential at the common ground end side becomes higher than the ground side, that is, the common ground end. When a forward voltage is generated between the ground and the earth, this voltage is detected by the voltage detection unit 10, and if the detected voltage satisfies the set voltage of the operating voltage setting unit 20 and exceeds the internal reference voltage, By outputting the control voltage from the control voltage generation unit 30, the switching element of the switching unit 40 is turned on, whereby the current due to the abnormal voltage applied to the common ground terminal is quickly passed to the ground.

Further, when a power line comes into contact with the ground due to a landfall or a lightning strike, or a lightning strike flows to the ground and the ground potential becomes higher than the common ground end side, the common ground end and the ground are grounded. The switching element is turned off by utilizing the reverse voltage generated in the above, and the common ground end and the earth ground are cut off, thereby preventing the reverse flow of the current from the earth ground to the common ground end.

Next, a specific embodiment of the current backflow prevention device 100 of the present invention will be described. FIG. 3 is a communication system of the current backflow prevention device 100 according to the present invention (see FIG.
It is a circuit diagram which shows the example of application to (reference).

In the figure, the voltage detecting section 10 is a current limiting resistor R12, R1 forming a current circuit for limiting the current flowing between the common ground end of the communication device 200 and the ground.
4, a diode D3 connected in the forward direction with respect to the resistors R12 and R14, and smoothing capacitors C3 and C4 connected between the diode D3 and the resistor R14. The voltage detected by the voltage detecting unit 10 is supplied to the operating voltage setting unit 20 and the control voltage generating unit 30 as respective power supply voltages.

The operating voltage setting unit 20 is composed of a variable resistor VR and a resistor R1 for dividing the detection voltage of the voltage detecting unit 10 supplied as the power supply voltage to set the operating setting voltage of the apparatus 100. . The operating voltage setting unit 20 is provided for the device 100 with respect to a noise voltage (less than about 27 V) that often occurs during operation of the communication device 200.
In order not to operate, the value higher than the noise voltage level is set as the operation setting voltage.

The control voltage generator 30 includes an operating voltage setting unit 2
Transistors Q1 to Q4 for comparing and amplifying the detection voltage of the voltage detection unit 10 input through 0 to the reference voltage, reference voltage setting transistors Q7 and Q8, and transistor Q
1 to Q4 and transistors Q7 and Q8 are connected to the transistors Q9 to Q11, and the transistors Q1 to Q4 are ON / OFF controlled according to the comparison output of the switching unit 4
Switching transistors Q5 and Q6 that output a control voltage for 0, resistors R2 to R11, capacitors C1 and C
2. The reverse voltage prevention diodes D1 and D2. The control voltage generating unit 30 includes one IC (Integrat
ed Circuit) can be realized by the integrated circuit.

The switching section 40 comprises a control voltage generating section 3
The control voltage output from 0 is applied to the gate G, and the common ground end and the ground end are connected to the anode A and the cathode K, respectively, and the switching element SCR4a and the resistor R.
And 13. Further, as a circuit element other than the above, a Zener diode ZD is provided between the voltage detection unit 10 and the control voltage generation unit 30.

The operation of the current backflow prevention device 100 will be described below. In the current backflow prevention device 100,
Communication devices 200a, 200 to which the device 100 is connected
Due to an abnormal voltage or a lightning current flowing in at points b to 200n, a voltage of several volts to several thousand volts may be generated between the common ground end and the ground.

In the current circuit in the voltage detecting section 10 using the abnormal voltage generated at the unspecified timing as a power source, a current flows from the common ground end toward the ground to the ground through the resistor R12, the diode D3 and the resistor R14. At that time, the current flowing through the current circuit is equal to the resistances R12 and R12.
It is rectified by the diode D3 and charged in the smoothing capacitors C3 and C4 while being limited through 14.

The charging potentials of the smoothing capacitors C3 and C4 are supplied to the operating voltage setting section 20 and the control voltage generating section 30 as the detection voltage of the voltage detecting section 10 through the Zener diode ZD.

The detection voltage applied from the voltage detection unit 10 is the variable resistance VR and the resistance R1 in the operating voltage setting unit 20.
After being divided by, the voltage is applied to the transistor Q1 in the control voltage generator 30. The voltage division process in the operating voltage setting unit 20 is performed to set an operating setting voltage as a standard for determining whether to operate the device 100 with respect to the detection voltage of the voltage detecting unit 10.

In the device 100, the operation setting voltage can be variably set by appropriately adjusting the variable resistor VR, and can be expressed by the following equation (1).

Vref × [1 + VR (a−c) / VR (c−b) + R1] (1) where Vref is the detection voltage of the voltage detection unit 10 and VR (a−c) is the terminal of the variable resistor VR ( The resistance value VR (c-b) between a and c) is the resistance value between the terminals (c-b) of the variable resistance VR. In an actual setting, for example, in a device such as a telephone operated with a power supply voltage of 48V, Since a noise voltage of about 27 V can often occur, the operating setting voltage is higher than the noise voltage (less than about 27 V), for example 38 V ±, in order to avoid being sensitive to the noise voltage. It is desirable to set the voltage to about 3V and to set it so as to match the operating characteristics of the SCR 4a in the switching unit 40 described later.

The applied voltage detected by the voltage detection unit 10 and having cleared the set voltage level in the operating voltage setting unit 20 is input to the transistor Q1 in the control voltage generation unit 30 and the minute voltage change is amplified. Transistor Q7,
It is compared with an internal reference voltage set by a reference voltage setting circuit composed of Q8 and resistors R2 to R7.

This comparison output is the output of the transistors Q2 and Q.
Switching transistors Q5 and Q6 through 3 and Q4
ON / OFF is controlled, and the output when the transistor Q6 is turned on is supplied as a control voltage to the gate G of the SCR 4a in the switching section 40 through the current limiting resistor R13. The SCR 4a is a circuit element that "turns on" and becomes conductive when a control voltage is input to the gate G.

More specifically, in the control voltage generator 30, for example, while the output voltage of the transistor Q1 is smaller than the internal reference voltage, the transistors Q9, Q10, Q11 are provided.
The transistors Q2, Q3, and Q4 maintain the OFF state according to the OFF state of the switching transistor Q5.
As a result of Q6 also being kept in the OFF state, the control voltage is not applied to the gate G of the SCR 4a, and the SCR 4a remains non-conductive.

On the other hand, when the output voltage of the transistor Q1 exceeds the internal reference voltage, the transistors Q9, Q
10, Q11 is turned on, and the transistor Q
The switching transistors Q5 and Q6 are also controlled to be in the ON state by turning ON the transistors 2, Q3 and Q4, and the output of the transistor Q6 is SCR as a control voltage.
It is input to the gate G of 4a.

By inputting this control voltage, the SCR 4a
Is turned on, and the anode A connected to the common ground terminal and the cathode K connected to the ground are connected. At this time, an abnormal current due to the noise voltage or the like generated at the common ground end as described above flows to the ground through the anode A and the cathode K of the SCR 4a.

After that, when the power transmission line comes into contact with the ground due to a landfall or a lightning strike, or a current due to a lightning strike flows to the ground and the ground side voltage rises, the current backflow prevention device 100
In this case, a voltage in the opposite direction to that in the above operation is generated between the common ground terminal and the earth.

That is, when the potential on the ground side as viewed from the common ground end side reaches several volts to several thousand volts due to a ground drop or lightning strike, the diode D3 in the voltage detecting section 10 is
A voltage in the opposite direction to that during the above operation is applied to the capacitor via the resistor R12. As a result, the diode D3 is turned off, charging of the smoothing capacitors C3 and C4 is stopped, and the supply of the power supply voltage from the voltage detection unit 10 to the operating voltage setting unit 20 and the control voltage generation unit 30 is cut off.

Accordingly, in the switching section 40, the control voltage is not input from the control voltage generating section 30 to the gate G of the SCR 4a, and at the same time, the reverse voltage is applied between the anode A and the cathode K of the SCR 4a, SCR4
a “turns off”.

As a result, the common ground end and the earth ground are separated from each other, and the backflow phenomenon of the current from the earth ground to the common ground end due to the above-mentioned landfall or lightning strike is prevented, and the communication device is broken or damaged. Is avoided.

Thus, the current backflow prevention device 1 of the present invention
In 00, between the common ground and the ground, the voltage generated between the common ground and the ground is applied as a forward voltage when an abnormal voltage or a lightning voltage is applied to the common ground of the communication device 200. Switching element (SCR
4a) is connected, and when the abnormal voltage reaches or exceeds a specified value, the abnormal voltage is detected and the control voltage is input to the gate G of the SCR 4a to control the SCR 4a to "turn on" to cause the abnormal condition. Protect the equipment by quickly flowing the current that flows to the common ground by the voltage to the ground.

On the other hand, when the power transmission line comes into contact with the ground due to a landfall or a lightning strike, or when a current caused by a lightning strike flows to the ground and the potential on the ground side rises, the above-mentioned condition is applied between the common ground end and the ground. Utilizes the fact that a reverse voltage is generated, the diode D3 in the voltage detecting unit 10 is turned off, and the operating voltage setting unit 20 and the control voltage generating unit 30 are used.
To stop the supply of power supply voltage to. In addition, SCR4
a control voltage is not input to the gate G of a and the SCR4a
The reverse voltage is applied between the anode A and the cathode K of the SCR 4a so that the SCR 4a is controlled to be "turned off", and the common ground end and the ground are separated from each other. The backflow phenomenon of electric current is prevented, and the failure or damage of communication equipment is prevented.

Considering the above operation method, it is meaningless in the current backflow prevention device 100 of the present invention unless the operation of backflow of current from the ground to the common ground end is instantaneously performed. In order to satisfy such a demand, the switching element in the switching unit 40 is turned on / off by a control voltage input to the gate G, as disclosed in the present embodiment.
A high speed switching element controlled by FF, which has an internal impedance minimized and can be adapted to an operation without abnormality within an input voltage range of several volts to several thousand volts.
It is necessary to use switching elements such as.

In the circuit configuration according to the present embodiment, the sensitivity speed of the SCR 4a is assumed to be about 60 [ns], but a communication device operated according to the CCITT recommended communication protocol has a sensitivity of 600 [ns]. Sometimes speed is required.

In the above embodiment, the application example to the communication equipment is described in particular, but the current backflow prevention device of the present invention is not limited to this type of communication system, but can be applied to any equipment or facility having a ground ground. It goes without saying that it can be applied.

[0042]

As described above, according to the present invention,
Between the common ground end of the equipment or facility and the earth ground, there is provided a switching means for setting a state in which the common ground end side has a high potential with respect to the earth ground to a forward potential, and the switching means is provided with Since it is maintained in the ON state by the application of voltage, and the high-speed switching operation is performed to return to the OFF state in response to the application of the reverse voltage of a certain level or higher, an abnormality occurs from the common ground end of the equipment or facility to the ground through the ground. While allowing the current to flow smoothly, the backflow current from the ground to the common ground end when the ground side has a higher potential than the equipment or facility side can be blocked by the high-speed return operation of the switching means. , It becomes possible to safely protect various devices or equipment.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a communication system formed by applying a current backflow prevention device according to the present invention.

FIG. 2 is a block diagram showing a functional configuration of a current backflow prevention device according to the present invention.

FIG. 3 is a circuit diagram showing an embodiment of a current backflow prevention device according to the present invention.

[Explanation of symbols]

 100, 100a, ~, 100n Backflow prevention device 10 Voltage detection unit 20 Operating voltage setting unit 30 Control voltage generation unit 40 Switching unit 200a, ~, 200n Communication equipment

Claims (6)

[Claims] 1. A control for comparing a detection voltage of a voltage generated at a common ground terminal of an equipment or facility with a reference voltage and a control voltage according to a result of the comparison. A voltage generating means is connected between the common ground terminal and the earth ground based on a control voltage output from the control voltage generating means for a forward voltage drop in which the common ground terminal has a higher potential than the earth ground. Switching control so as to prevent the voltage drop in the forward direction and the voltage drop in the reverse direction from being cut off between the common ground terminal and the ground. A reverse current prevention device for the current through the characteristic earth ground. 2. The earth according to claim 1, further comprising: operating voltage setting means for setting a threshold voltage for selecting the voltage detected by the voltage detecting means as a comparison voltage with the reference voltage. Backflow prevention device for current through ground. 3. The voltage detecting means includes a resistor (R1) for limiting a current flowing between the common ground terminal and the ground.
2) and (R14), a diode (D3) connected in the forward direction with respect to the resistors (R12) and (R14), and a smoothing capacitor connected between the diode (D3) and the resistor (R14). The backflow prevention device for the current through the ground according to claim 1, characterized in that it is composed of (C3) and (C4). 4. The switching means is connected between the common ground end and the earth ground, and the control voltage generating means is provided for the forward voltage drop in which the common ground end has a higher potential than the earth ground. The earth ground according to claim 1, further comprising a high-speed switching element (4a) which is turned on based on the output control voltage and turned off against a voltage drop in a direction opposite to the voltage drop in the forward direction. Current backflow prevention device. 5. The device for preventing backflow of current through earth ground according to claim 4, wherein the switching element (4a) is an SCR. 6. The operating voltage setting means comprises a variable resistor (VR) and a resistor (R1) that variably adjust the threshold voltage by dividing the detection voltage of the voltage detecting means. Item 2. A device for preventing backflow of current through earth ground according to Item 2.