JPH09266052A - Surge absorber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surge absorber which can even deal with low-voltage surges which conventional gas arrestors cannot deal with. SOLUTION: In a first surge absorber 10, in which a pair of discharge electrodes 16, 16 are oppositely arranged at a predetermined distance to each other inside an airtight container 26 filled with a discharge gas with a discharge gap 18 formed between the end discharge parts 16a, 16a of the discharge electrodes and with lead terminals 24, 24 brought out, a CR connection 20 in which a ceramic capacitor 40 is integrated with a ceramic resistance 42 via a conductive adhesive is connected between recesses 16b, 16b in the discharge electrodes and thereby connected in parallel with the discharge gap 18.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surge absorber which is inserted in a front stage of an electronic device in order to protect an electronic circuit of the electronic device from an overvoltage such as a surge which intrudes along a power line or a communication line. The present invention relates to an element, and more particularly, to a discharge type surge absorbing element having a mechanism for absorbing a surge or the like by utilizing a discharge phenomenon in a discharge gap.

[0002]

2. Description of the Related Art Conventionally, a gas arrester, which is a kind of a discharge type surge absorbing element, or a voltage non-linear characteristic is provided between lines such as a power supply line and a communication line leading to an electronic circuit of an electronic device or between each line and the ground. A surge absorbing element such as a varistor, which is a high resistance element provided, is connected to protect an electronic circuit from a surge. FIG. 6 shows an example of such a protection circuit. A surge absorbing element 52 is connected between a pair of power supply lines L1 and L2 leading to an electronic circuit 50 of an electronic device, and a power supply line L1, L2 and ground (GND)
Other surge absorbing elements 54, 54 are also inserted and connected between and. A fuse 56 for shutting off overcurrent is connected to the power line L1.

When a normal mode surge voltage that reciprocates between the power lines L1 and L2 is applied, the surge absorbing element 52 between the lines operates to absorb the surge voltage. When a common-mode surge voltage that propagates between the line and ground is applied, the surge absorbing element 54,
54 operates and lets this escape to the ground side.

A varistor is often selected as the surge absorbing element 52 inserted between the lines, and a gas arrester is generally selected as the surge absorbing elements 54, 54 inserted between the line and the ground.

FIG. 7 shows the structure of the gas arrester 60, in which a discharge gas such as an inert gas is enclosed in an airtight container 62 formed by melting and sealing the upper and lower ends of a glass tube, and a pair of them is formed. The discharge electrodes 64, 64 are arranged so as to face each other with a constant distance, and a discharge gap 66 is formed between the discharge electrodes 64, 64. The discharge electrodes 64, 64 are formed by forming emitter layers 72, 72 made of lanthanum hexaboride or the like on the surface of rod-shaped electrode base bodies 70, 70 made of nickel with lead wires 68, 68 connected to their lower ends. The lower ends of the lines 68 and 68 are the lower end sealing portion 62 of the airtight container 62.
It passes through a and is led to the outside.

However, when a common mode surge voltage higher than the operating voltage of the gas arrester 60 is applied to the power supply lines L1 and L2 from the input side, arc discharge is generated through glow discharge in the discharge gap 66, Due to the large current of the arc discharge, the surge is released to the ground side, and the electronic circuit 50 of the electronic device is protected from the surge. When the gas arrester 60 is used, the resistors 74, 74, etc. are connected in series as shown in FIG. As described above, since the gas arrester 60 absorbs a surge through a large current of arc discharge in the discharge gap 66, it has a relatively large current withstand capability and can be said to be suitable as a surge absorbing element to be inserted between the line and the ground. .

[0007]

The performance characteristics of this gas arrester are generally indicated by the DC discharge inception voltage (Ez). For example, if the element has an Ez value of 90V, 90
When an overvoltage of V or more is applied, it is turned on and absorbed. By the way, this gas arrester has a structural limitation that the Ez value cannot be set to 80 V or less because it has a mechanism of absorbing a surge by utilizing a gas discharge phenomenon. For this reason, when an overvoltage of 80 V or less is applied to the protection circuit incorporating the gas arrester, it cannot be effectively absorbed, and there is a problem that the electronic circuit of the electronic device cannot be completely protected.

The present invention has been made in view of the above problems, and an object of the present invention is to realize a surge absorbing element which can cope with a low voltage surge which cannot be dealt with by a conventional gas arrester.

[0009]

In order to achieve the above object, a surge absorbing element according to the present invention has a plurality of discharge electrodes arranged facing each other at a predetermined distance in an airtight container filled with discharge gas. In a surge absorbing element formed by forming a discharge gap between each discharge electrode and leading a lead terminal connected to each discharge electrode out of an airtight container, a CR connection body in which a capacitor and a resistor are connected in series The feature is that they are connected in parallel to the gap. For example, a pair of discharge electrodes are arranged to face each other with a predetermined distance, and a discharge gap is formed between the tip discharge parts of both discharge electrodes, and the other parts of both discharge electrodes are connected via the CR connector. That is applicable. Further, as the CR connection body, it is desirable to use a ceramic capacitor and a ceramic resistor integrated via a conductive adhesive.

The surge absorbing element is inserted and connected between the line and the ground by connecting one lead terminal of the surge absorbing element to a power supply line or the like communicating with an electronic circuit of an electronic device and grounding the other. Then, when a common mode surge voltage is applied from the input side through the power supply line or the like, the CR connection body first functions as a filter and immediately starts the surge attenuation operation. When the surge is equal to or higher than the preset operating voltage (Ez value) of the discharge gap, after a certain period of time, an arc discharge as a main discharge is generated through a glow discharge in the discharge gap, and a large arc discharge is generated. Surge absorption is started through the electric current. On the other hand, when the applied surge voltage is less than the operating voltage of the discharge gap, no discharge is generated in the discharge gap and the surge absorption by the arrester operation is not performed, but the surge by the CR connector is not generated. Since the damping operation is performed, it is possible to effectively prevent the electronic circuit of the electronic device from being damaged.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION As shown in FIG. 1, a first surge absorbing element 10 according to the present invention has a cylindrical body 12 made of ceramic such as forsterite, and 426 for closing both end openings of the cylindrical body 12. Conductive cover members 14, 14 made of an alloy or the like,
Discharge electrodes 16 and 16 made of iron, nickel or the like connected to the inner surfaces of the lid members 14 and tip discharge parts of both discharge electrodes 16 and 16.
Discharge gap 18 formed between 16a and 16a and both discharge electrodes 1
CR connector 20 sandwiched between 6 and 16 recesses 16b and 16b
And lead terminals 24, 24 connected to the outer surface center of the lid member via solders 22, 22. The cylindrical body 12
The opening and the lid member 14 are airtightly connected via a sealing material 25, and as a result, an airtight container 26 is formed. The airtight container 26 is filled with a discharge gas such as an inert gas. Although not shown, the discharge electrodes 16 and 16 are coated on their surfaces with an emitter material made of lanthanum hexaboride, gadolinium hexaboride, yttrium hexaboride, or the like.

Further, as shown in FIG. 2, the second surge absorbing element 30 is filled with a discharge gas such as an inert gas in an airtight container 32 formed by melting and sealing both ends of a glass tube. At the same time, a pair of discharge electrodes 34, 34 made of 42 alloy, nickel or the like are arranged to face each other to form a discharge gap 18 between the tip discharge parts 34a, 34a, and the recesses 34b, 34 of the discharge electrodes 34, 34 are formed.
b is connected via a CR connector 20. Dumet wires 36, 36 as lead terminals are connected to the respective end faces of the discharge electrodes 34, 34 via solders 22, 22, and the other ends of the dumet wires 36, 36 are sealed with an airtight container 32. It is led out through the part. Although not shown, the discharge electrode
The same emitter material as described above is also deposited on the surfaces of 34 and 34.

The CR connecting body 20 is one end surface 40a of a ceramic capacitor 40 which is processed into a cylindrical shape as shown in FIG.
And one end face of the ceramic resistor 42, which is also processed into a cylindrical shape
42a is connected via a conductive adhesive 44, and an insulating layer (not shown) made of lead-free bismuth glass or the like on the surface
Both ends 20a, 20b of the CR connector 20.
Is fixed between the recesses 16b, 16b (34b, 34b) of the discharge electrode via a conductive adhesive (not shown).

As a result of the above, as shown in the equivalent circuit diagram of FIG. 4, the first surge absorbing element 10 and the second surge absorbing element 10
30 has a structure in which the discharge gap 18 and the CR connection body 20 are connected in parallel, and the same configuration as that in which a series circuit of a capacitor and a resistor is connected in parallel to the gas arrester is realized.

As shown in FIG. 6, two first surge absorbing elements 10 or second surge absorbing elements 30 are used, one end of each lead terminal is connected to the power supply lines L1 and L2, and
By grounding the other end, the first surge absorbing element 10 or the second surge absorbing element 30 becomes the surge absorbing element 54,
54 is inserted between each power supply line L1 and L2 and the ground (GND). When a common mode surge voltage is applied from the input side through the power lines L1 and L2, the first
The CR connection body 20 of the surge absorbing element 10 or the second surge absorbing element 30 functions as a filter and promptly starts the surge damping operation.

FIG. 5 is a graph showing the effect of damping the surge by the CR connector 20, showing that the attenuation waveform shown by the solid line is extremely small compared with the waveform of the original surge shown by the two-dot chain line. As can be seen, the original surge is reliably damped by the CR connector 20. Between the respective values of the ceramic capacitor 40 and the ceramic resistor 42 forming the CR connection and the above-mentioned attenuation waveform, the peak height h decreases as the capacitance of the ceramic capacitor 40 increases, and the ceramic resistor 42 There is a relation that the peak width w becomes narrower as the resistance value becomes higher. Therefore, it can be said that it is desirable to set each value of the ceramic capacitor 40 and the ceramic resistor 42 as large as possible for the purpose of damping the surge voltage, but if the value of the ceramic capacitor 40 is set too large, There is a problem that the impedance decreases and the value of the leakage current increases. Maximum allowable leakage current during normal use of electronic equipment is 1 m
Considering A, it is practically desirable to set the value of the ceramic capacitor 40 to 0.022 μF or less. For the ceramic resistor 42, 10 to 15
It is desirable to select a value of 0Ω and a rated power of 0.5 to 10W.

When the applied surge voltage is equal to or higher than the Ez value in the discharge gap 18, an arc discharge as a main discharge is generated through a glow discharge in the discharge gap 18 after a certain period of time, and thereafter. Surge absorption due to arrester operation is realized. In order to prevent follow current, it is desirable to connect a resistor or a varistor in series to the first surge absorbing element 10 or the second surge absorbing element 30. If the applied surge voltage is less than the Ez value of the discharge gap 18, no discharge is generated in the discharge gap 18 and the surge is not absorbed by the arrester operation, but Since the attenuation is performed, it is possible to prevent the surge voltage from being directly applied to the electronic circuit of the electronic device.

[0018]

In the surge absorbing element according to the present invention, since the CR connecting body is connected in parallel to the discharge gap, even if no discharge is generated in the discharge gap, the CR connecting body prevents surges or the like. The overvoltage can be attenuated, and it is possible to sufficiently cope with the application of a surge voltage below the DC discharge starting voltage in the discharge gap.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first surge absorbing element according to the present invention.

FIG. 2 is a sectional view showing a second surge absorbing element according to the present invention.

FIG. 3 is a perspective view showing a CR connection body related to a first surge absorbing element and a second surge absorbing element.

FIG. 4 is an equivalent circuit diagram of a first surge absorbing element and a second surge absorbing element.

FIG. 5 is a graph showing how surges are attenuated by a CR connector.

FIG. 6 is a circuit diagram showing a connection example of a surge absorbing element.

FIG. 7 is a sectional view showing a conventional gas arrester.

[Explanation of symbols]

 10 First surge absorber 16 Discharge electrode 16a Discharge electrode tip discharge part 16b Discharge electrode recess 18 Discharge gap 20 CR connector 24 Lead terminal 26 Airtight container 30 Second surge absorber 32 Airtight container 34 Discharge electrode 34a Discharge Electrode tip Discharge part 34b Discharge electrode recess 36 Dumet wire 40 Ceramic capacitor 42 Ceramic resistance L1 power line L2 power line GND ground

Claims (3)

[Claims] 1. A lead terminal connected to each discharge electrode, wherein a plurality of discharge electrodes are arranged facing each other with a predetermined distance in an airtight container filled with discharge gas to form a discharge gap between the discharge electrodes. In a surge absorbing element obtained by deriving the element outside the airtight container, a CR connecting body in which a capacitor and a resistor are connected in series is connected in parallel to the discharge gap. 2. A pair of discharge electrodes are arranged so as to face each other with a predetermined distance, a discharge gap is formed between the tip discharge parts of both discharge electrodes, and the CR connection body is provided between the other parts of both discharge electrodes. The surge absorbing element according to claim 1, wherein the surge absorbing element is connected via the surge absorbing element. 3. The surge absorbing element according to claim 1, wherein the CR connection body is formed by integrating a ceramic capacitor and a ceramic resistor via a conductive adhesive.