KR100448684B1 - A surge voltage suppressing circuit - Google Patents

Abstract

PURPOSE: An overvoltage protection circuit is provided to protect a measurement control circuit by suppressing spurious conductive noise of an overvoltage induced to a measurement line while transmitting physical parameter information by detecting a number of parameters to the measurement line. CONSTITUTION: The first protection circuit(201) suppresses the first intrusion of an overvoltage due to the ground of a commercial frequency AC voltage through a gas discharge tube. The second protection circuit(203) comprises a positive temperature coefficient resistor connected to each port of the line to prevent the self over-heating due to a residual over-current of the first protection circuit or over-heating state of the measurement control circuit. The third protection circuit(205) comprises a varistor connected to both ends of the line and between each port of the line and the earth ground to confine a residual over voltage of the first protection circuit and the second protection circuit within a fixed level. The fifth protection circuit(209) comprises an avalanche breakdown diode connected to both ends of the line and between each port of the line and the earth ground to prevent the inflow of a breakdown voltage by suppressing the residual voltage of the third protection circuit. And the fourth protection circuit(207) comprises a linear resistor to suppress the over current of the fifth protection circuit.

Description

Transient Voltage Protection Circuits {A SURGE VOLTAGE SUPPRESSING CIRCUIT}

The present invention relates to a transient voltage protection circuit, and more particularly, to a transient voltage protection circuit for detecting and suppressing a transient voltage of a current sensor and a measurement control circuit and measuring a coefficient for the transient voltage.

In general, the transmitter used for sensor input / output and measurement control circuit of DC 4 ~ 20mA transmits a large amount of physical quantity such as voltage, current, frequency, temperature, pressure, water level, quantity detected in outdoor field as current signal Since the physical information is transmitted to the receiving device through a medium-distance line over several kilometers, it is possible to mix with the transient voltage caused by internal factors such as switchable transient voltages, or with external transient voltages such as brain surges and low voltage AC circuits. Short circuit) or ground fault. In addition, when a signal is combined with a power line or a large current circuit during signal transmission, noise may be induced to distort the original measured amount.

Therefore, in order to improve the accuracy of the measurement, the transient voltage protection circuit is added to the line to increase the stability of the system. A conventional general transient voltage protection circuit is shown in FIG. 1A as shown in FIG. 1A. The voltage protection measures circuit 120, the line 130, the transient voltage protection measures circuit 140, the controller 150, and in particular the transient voltage protection measures circuit 140 is shown in Figure 1b A ceramic gas discharge tube 101 is connected between the input terminals T1 and T2, and a fuse and an RL series circuit are connected to one line T1. In addition, the avalanche diodes ZD1 and ZD2 are arranged in a reverse direction between the output terminals L1 and L2 of the line.

Here, the ceramic gas discharge tube 101 is used as a primary suppression circuit when a transient voltage invades, and the RL series circuit acts as an RLC low pass filter circuit based on the leakage capacitance of the avalanche diode and the RL value to suppress the primary suppression. It is a secondary suppression circuit that suppresses unwanted conductive noise of voltage. The avalanche diode circuit is a third suppression circuit of the transient voltage, and removes noise above a predetermined voltage to perform final filtering of the transient voltage.

In general, the transient voltage suppression circuit configured as described above suppresses the transient voltage of a predetermined value through the ceramic gas discharge tube and passes through the fuse. Therefore, when the fuse is blown and the circuit is opened, the protection circuit function is lost. It becomes impossible. In addition, when a transient voltage of high voltage and high current is applied to pass through the fuse through the ceramic gas discharge tube, when the fuse is not opened, breakage of the avalanche diode may occur, which may cause damage to the measuring device.

The present invention has been made to solve the above problems, and an object of the present invention is to control the measurement control circuit by suppressing the undesired conductive noise of the transient voltage flowing into the line during the transmission of physical quantity information through the detection of multiple parameters on the measurement line. In addition to the protection of the present invention, a transient voltage protection circuit for facilitating the cause and path tracking of the measurement control device through the coefficient of the transient voltage.

The transient voltage protection circuit according to the aspect of the present invention for achieving the above object is connected to both ends of the line, the first for suppressing the primary intrusion of the transient voltage by contact or ground fault of the commercial frequency AC voltage through the gas discharge tube Protection circuit; A second protection circuit composed of a positive temperature coefficient resistor connected in series on each terminal of the line to prevent self overheating due to the residual overcurrent of the first protection circuit or overheating of the measurement control circuit; A third protection comprising a varistor (Varistor: Resistor) connected to both ends of the line and between each terminal and the ground of the line to limit the residual transient voltages of the first protection circuit and the second protection circuit to a predetermined level. Circuit; A fifth protection circuit comprising an avalanche breakdown diode connected to both ends of the line and between each terminal and the ground of the line to suppress a residual voltage of the third protection circuit to prevent inflow of an insulation breakdown voltage; And a fourth protection circuit connected in series with each terminal of the line between the fifth protection circuit and the third protection circuit and configured with a linear resistor for suppressing overcurrent of the fifth protection circuit.

Specifically, the transient voltage counting unit is installed in close proximity to the gas discharge tube and includes a light receiving sensor for detecting a light emitting state, and counting the number of times of transient voltage intrusion based on the detection signal of the light receiving sensor; And a display portion for displaying the counting result of the transient voltage coefficient portion.

1A is a circuit diagram used for suppressing a transient voltage in the related art.

FIG. 1B is a detailed view of the transient voltage protection circuit of FIG. 1.

2 is a circuit diagram illustrating a transient voltage protection circuit according to the present invention.

3 is a diagram illustrating a fastening configuration between devices illustrating the first protection circuit of FIG. 2.

4 is a voltage waveform diagram showing the operation performance according to the present invention.

<Explanation of symbols for main drawings>

201: first protection circuit 203: second protection circuit

205: third protective circuit 207: fourth protective circuit

209: fifth protective circuit 211: display unit

213: three-pole gas discharge tube 215: counter

303: first fitting ring 305: tube

307: second fitting ring

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. 2 is a circuit diagram for preventing a transient voltage according to the present invention, a transient voltage protection circuit for protecting the measurement control circuit of 4 ~ 20mA. As shown, the transient voltage protection circuit according to the present invention is a first protection circuit 201 for gradually limiting the transient voltage invading on the lines (T1, T2) and the current generated from the transient voltage to a certain level And a second protection circuit 203, a third protection circuit 205, a fourth protection circuit 207, and a fifth protection circuit 209, and each protection circuit is connected in series with each other. In addition, a transient voltage counting unit 215 for interlocking with the first protection circuit 201 and detecting whether the transient voltage is invaded is provided, and displaying the counting result of the transient voltage counting unit 215. It includes a display unit 211 for.

The first protection circuit 201 primarily suppresses the transient voltage penetrating into the line, and comprises a three-pole gas discharge tube 213 and a light receiving sensor. As the light receiving sensor, a photo transistor, a photo diode, and a cadmium sensor (CDS) may be used. In addition, the three-pole gas discharge tube 213 discharges at a minimum of 800 V based on a standard brain impulse voltage, that is, a 1.2 / 50 Hz waveform, and a commercial frequency AC voltage of 50/60 Hz is mixed with a control circuit or a ground fault occurs in the vicinity. Discharge starts at least 130V. The discharge of the three-pole gas discharge tube 213 due to the transient voltage generates a light source, and the light source is detected by the light receiving sensor.

The three-pole gas discharge tube 213 is a commercially available device, and a detailed description thereof may deviate from the gist of the present invention, and thus description of the operation principle and shape will be omitted.

On the other hand, the light receiving sensor induces a change in resistance value or a change in conduction current by a light source generated at the time of discharge, and measures the intrusion coefficient of the transient voltage by switching through the transistor TR. The input port of the counter 215 is connected to the emitter terminal of the transistor TR and performs noise removal and shaping of the switching signal provided from the emitter terminal of the transistor TR. A count is performed based on the number of occurrences of the standardized switching signal (pulse), and the count result is displayed on the display unit 211.

The manager may measure the number of transient voltage intrusions in the corresponding area based on the display result of the display unit 211, and may contribute to maintenance of the facility based thereon. The transient voltage counting unit 215 holds a separate battery (B) power.

After performing the first suppression of the transient voltage through the first protection circuit 201, the measurement control circuit is protected from the high voltage which may occur after the first suppression of the transient voltage through the second protection circuit 203. do. The second protection circuit 203 is connected to the positive temperature coefficient resistors PTC1 and PTC2 on the respective lines, and the positive temperature constant resistances PTC1 and PTC2 are controlled by overheating or measurement control of the protection circuit itself due to an overcurrent in the case of an AC mixed accident. In order to prevent overheating of the circuit, it is preferable to use a PTC element which is a static thermistor.

Positive temperature coefficient resistance (PTC1, PTC2) suppresses overcurrent due to the proportional increase in resistance when temperature rises on the line due to intercalation accidents or intrusion of transient voltages. Normalization takes place.

The third protection circuit 205 is composed of a nonlinear resistor for limiting the residual transient voltage that is not sufficiently suppressed in the first and second protection circuits 201 and 203. The nonlinear resistor is preferably zinc oxide varistor (nonlinear resistor), and may be ZNR, INR, TNR, etc. according to the change of the circuit. In the varistors NR1, NR2, and NR3, a first varistor NR1 is connected between the lines T1 and T2 to simultaneously suppress transient voltages generated between the lines and the line-to-ground, and the second varistor NR2. ) And the third varistor NR3 form a structure in which the connection node is earthed after being connected in series with each other.

That is, when a transient voltage greater than or equal to the reference value between the lines T1 and T2 occurs, the resistance of the varistor is increased by the voltage rise across the first varistor NR1 to induce line insulation. When the transient voltage is generated between the ground and the line, the insulation between the ground and the line is transferred by the second varistor NR2 or the third varistor NR3, thereby suppressing the residual transient voltage nonlinearly.

The fourth protection circuit 207 connects the linear resistors R2 and R3 on each line to suppress overcurrent flowing into each line. In addition, since the fourth protection circuit 207 limits the input current of the fifth protection circuit 209, the fourth protection circuit 207 ensures stability such as short circuit protection of the fifth protection circuit 209.

The fifth protection circuit 209 is for ultimately suppressing residual transient voltages that are not suppressed in the third protection circuit 205. Similarly, the first Avalanche Breakdown Diode ZD1 is connected on the lines L1 and L2, and the second Avalanche Breakdown Diode ZD2 is connected between the one side L1 and the ground G. The third avalanche breakdown diode ZD3 is connected between the other line L2 and the ground G.

The first avalanche breakdown diode ZD1 suppresses a residual transient voltage between lines, and the second avalanche breakdown diode ZD2 and a third avalanche breakdown diode ZD3 suppress a residual transient voltage between the line and the ground. Therefore, a voltage of 100 V or more, which is the minimum dielectric breakdown voltage, does not enter the sensor or the measuring and control device.

3 is a configuration diagram illustrating a first protection circuit 201 according to the present invention. As described above, the three-pole gas discharge tube 213, the light receiving sensor 301 and the tube 305, the tube 305 is a rubber tube of an opaque material having a predetermined size of elasticity, the opening surface up and down Has In addition, the upper opening surface allows the first fitting ring 303 of a predetermined width to be fixed inlet, the outer peripheral surface of the three-pole gas discharge tube 213 to the inner circumferential surface of the first fitting ring 303, the lower side The second fitting ring 307 having a predetermined width is pulled in and fixed to the opening surface, and the outer circumferential surface of the light receiving sensor 301 is imparted to the inner circumferential surface of the second fitting ring 307.

Therefore, when the transient voltage is generated, the three-pole gas discharge tube 213 of the first protection circuit 201 is discharged, and the light source generated at this time is the first fitting ring 303, the tube 305, and the second fitting ring ( As it is not emitted to the outside by the 307, the light receiving rate of the light receiving sensor 301 can be increased.

4 is a voltage waveform diagram illustrating the operation performance of the transient voltage protection circuit according to the present invention. As shown, ⓐ is a 20 kV standard brain impulse voltage (1.2 / 50 kV) waveform diagram intruding onto the line. The waveform ⓑ is an experimental waveform diagram suppressed through the three-pole gas discharge tube 213 of the first protection circuit 201 when the standard brain impulse voltage invades between the line and the ground. In this experimental value, it is suppressed to 1.844kV.

The waveform ⓒ shows a voltage waveform diagram suppressed by passing through the second protection circuit 203 and the third protection circuit 205, which indicates the nonlinear resistance of the second protection circuit 203 and the third protection circuit ( It is shown that the high frequency conduction noise on the graph is effectively suppressed by the RC low pass filter characteristic due to the leakage capacitance between the varistors in 205). The ⓓ waveform is a voltage waveform finally induced by the fourth protection circuit and the fifth protection circuit to the input terminal of the measurement control device or the sensor unit, and the linear resistance of the fourth protection circuit 207 and the fifth protection circuit ( The high frequency conduction noise is suppressed by the RC low pass filter characteristic due to the leakage capacitance of the Avalanche breakdown diode of 209. The waveform of ⓓ maximum suppression voltage in this graph has a test result of 47V.

What has been described above is only one embodiment for preventing transient voltage and suppressing unwanted conductive noise according to the present invention, and the present invention is not limited to the above-described embodiment, and as claimed in the following claims, Without departing from the gist of the present invention, those skilled in the art to which the present invention pertains to the technical spirit of the present invention to the extent that various modifications can be made.

As described above, the transient voltage protection circuit according to the present invention implements a protection circuit for suppressing the transient voltage step by step, thereby increasing the transient voltage suppression performance on the line to secure the accuracy of signal transmission. By counting the number of occurrences of transient voltages, it is possible to easily trace the cause and path of the measurement control device and contribute to the maintenance of the facility. In addition, by using a temperature coefficient resistance circuit, the fuse is not opened when an overcurrent flows, thereby increasing the stability of the circuit. The side effect of further increasing the transient voltage suppression performance of the phase is obtained.

Claims (7)

A first protection circuit connected to both ends of the line for suppressing the first intrusion of the transient voltage due to the mixing or grounding of the commercial frequency AC voltage through the gas discharge tube; A second protection circuit composed of a positive temperature coefficient resistor connected in series on each terminal of the line to prevent self overheating due to the residual overcurrent of the first protection circuit or overheating of the measurement control circuit; A third protection comprising a varistor (Varistor: Resistor) connected to both ends of the line and between each terminal and the ground of the line to limit the residual transient voltages of the first protection circuit and the second protection circuit to a predetermined level. Circuit; A fifth protection circuit comprising an avalanche breakdown diode connected to both ends of the line and between each terminal and the ground of the line to suppress a residual voltage of the third protection circuit to prevent inflow of an insulation breakdown voltage; And And a fourth protection circuit connected in series with the respective terminals of the line between the fifth protection circuit and the third protection circuit and configured of a linear resistor for suppressing overcurrent of the fifth protection circuit. The apparatus of claim 1, further comprising: a light receiving sensor installed in proximity to the three-pole gas discharge tube and configured to detect a light emitting state, the transient voltage counting unit counting the number of times of transient voltage intrusion based on a detection signal of the light receiving sensor; And a display unit for displaying the counting result of the transient voltage counting unit. The transient voltage protection circuit according to claim 2, wherein the transient voltage counter performs a count using its own independent power source. The light receiving sensor of claim 2, wherein the light receiving sensor is any one of a photo transistor, a photo diode, and a cadmium sensor (CDS), and maintains a constant gap between the three-pole gas discharge tube and the light receiving sensor and prevents the light source from leaking. Transient voltage prevention circuit, characterized in that the tube of opaque material to be fixed. 2. The transient voltage protection circuit according to claim 1, wherein a current provided to the measurement control circuit through the fifth protection circuit is 4 to 20 mA. The transient voltage protection circuit according to claim 1, wherein the positive temperature coefficient resistance of the second protection circuit is a positive temperature coefficient (PTC) element which is a positive characteristic thermistor. The transient voltage protection circuit of claim 1, wherein the varistor of the third protection circuit is a zinc oxide varistor (nonlinear resistor).