JPH1050453A - Circuit protection instrument and printed substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To protect electronic circuit parts highly reliably, without using an arrester such as a varistor. SOLUTION: A circuit protection instrument 1 consists of a pair of conductive terminals T, connected with an electric power source node 5 of an electric circuit to which electricity is supplied from an outside electric power source and an earth node 6, respectively, and set on the opposite to each other while their tip end parts 3 are kept at a space. Spark is generated in the air gap formed between the tip end parts of the conductive terminals T and a current is carried between the electric power source node 5 and the earth 6 so that the number of allowable times of sparking can be significantly increased, as compared with that of a conventional pattern gap.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit protection device for protecting an electric circuit component from a surge caused by a lightning or the like on a power supply path from an external power supply.

[0002]

2. Description of the Related Art Conventionally, in order to protect electric circuit components on a printed circuit board P as shown in FIG. 1 from such a surge, a power supply line of the printed circuit board P connected to an external power supply and a ground are conventionally used. A so-called lightning arrester such as a varistor or an arrester may be mounted between the lines.

However, since a plurality of lightning arresters are usually mounted on a printed circuit board in order to comply with safety standards, there has been a problem that the printed circuit board after mounting is very expensive.

In addition, as shown in FIG. 5, a power supply line 5 and a ground line 6 of a printed circuit board P are brought close to each other when forming a printed wiring pattern without using a lightning arrester. . In this way, when a high voltage is applied between the power supply line 5 and the ground line 6 due to a surge, a spark is generated between the side surfaces of the conductors forming the lines 5 and 6, and the power flows to the ground, and 5,6
Since the voltage between them decreases, the electric circuit component D on the printed circuit board P is protected.

However, when a spark is generated on the printed board P, the conductor forming the wiring pattern and the epoxy resin between the conductors are carbonized, so that the printed board P becomes black, and the spark is repeated many times. In addition, since the insulation between the power supply line 5 and the ground line 6 is broken, the allowable number of sparks is limited, and the life and reliability of the printed circuit board P are deteriorated.

Accordingly, an object of the present invention is to provide a device which can protect an electric circuit component with high reliability without using an arrester.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention is directed to a power supply node and a ground node of an electric circuit supplied from an external power supply, and the front ends thereof are opposed to each other with a space therebetween. A set of conductive terminals constituted a circuit protection device. This circuit protection device is preferably mounted on a printed circuit board together with electric circuit components.

[0008] In the circuit protection device according to the present invention,
When a surge occurs on the power supply path from the external power supply, a spark is generated in an air gap formed between the tips of a pair of conductive terminals, and current flows to the ground, and a current flows between the two lines. The voltage will drop.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a circuit protection device according to the present invention will be described with reference to the accompanying drawings, taking a case of mounting on a printed circuit board as an example.

A conductive terminal T shown in FIG. 2 is mounted on a printed circuit board P on which an electric circuit component D as shown in FIG. 1 is implemented.

The conductive terminal T is formed by bending a T-shaped metal plate to protrude downward from the flat plate portion 2, a front end portion 3 bent downward from the flat plate portion 2, and both rear ends of the flat plate portion 2. The side plate portion 4 is formed.

As shown in FIGS. 3 (a) and 3 (b), the conductive terminal T is provided with a side plate portion 4 in a through hole 7 formed in a power supply line 5 and a ground line 6 pattern-wired on a printed circuit board P. It is mounted on the printed circuit board P by inserting and soldering. Reference numeral 12 indicates a ground resistance.

These conductive terminals T are opposed in a through hole 8 formed in the power supply line 5 and the ground line 6 of the printed circuit board P, with the leading end portions 3 spaced apart from each other. Is composed. When a voltage equal to or higher than a predetermined voltage is applied between the power supply line 5 and the ground line 6, the circuit protection device 1
Sparks are generated between the distal end portions 3 of the conductive terminals T and are conducted to each other, and a current flows from the power supply line 5 to the ground via the ground line 6, so that a high voltage between the power supply line 5 and the ground line 6 instantaneously increases. Since the voltage is relaxed, a high voltage is not applied to the electric circuit component D by the bypass capacitor or the like on the printed circuit board P. Therefore, the electric circuit component D on the printed circuit board P can be protected, and when the electric circuit component D is a tantalum capacitor or a CMOS device, the explosion or latch-up of the electric circuit component D is prevented, and
Safety can be improved.

An example in which this circuit protection device is applied to an AC adapter circuit will be described below. In the AC adapter circuit shown in FIG. 4, the circuit protection device 1
It is provided in the primary side circuit of the circuits classified into the secondary side, and is located between the power supply line 5 to which a household power supply is connected and supplied with 100 volts AC and the ground line 6.

In a household power supply (outlet), a surge of about 10,000 volts may occur momentarily due to lightning because the power line is outside. If 10,000 volts is applied to the AC adapter circuit in FIG. Coupler 10
Is destroyed because it has a withstand voltage of only about 5000 volts. If the operational amplifier IC11 is manufactured by a CMOS process, it causes a latch-up and emits smoke.
Since the circuit protection device 1 is provided at the connection point between the AC adapter circuit and the household power supply, if a voltage exceeding a predetermined level is applied between the power supply line 5 and the ground line 6 due to a surge, a spark is generated between the conductive terminals T. As a result, the power supply line 5 and the ground line 6 are instantaneously energized, so that the bypass capacitor on the printed circuit board P cannot be charged, and a high voltage reaches the electric circuit components D such as the photocoupler 10 and the operational amplifier IC 11. It does not take. For this reason, the destruction of the electric circuit component D can be prevented, and the safety and reliability of the AC adapter board can be improved.

In this circuit protection device 1, since the spark is generated in the air gap, the allowable number of sparks is remarkably improved as compared with the conventional case where the wiring pattern is brought close. In the experiment, it was confirmed that there was no change in the printed circuit board P or the electric circuit component D even after the spark was applied 1,000 times, and the durability was remarkably improved as compared with the related art. Further, since no lightning arrester such as an arrester or a varistor is used, it is very advantageous in terms of cost.

By changing the distance between the distal ends 3 of the conductive terminals T, the spark generation voltage is appropriately set, and the sensitivity of the circuit protection device 1 to surges is adjusted so as to meet a desired safety standard. Good. Further, a plurality of the circuit protection devices 1 may be provided on the printed circuit board P so that a larger current can flow to the ground. further,
One of the conductive terminals T may be a heat sink or a jumper wire mounted on the printed circuit board P. In this case, the metal end surface of the heat sink or the jumper wire faces the other conductive terminal T.

[0018]

The circuit protection device according to the present invention is configured as described above, so that the allowable number of sparks is greatly improved as compared with the conventional one, so that the electric circuit components can be protected with high reliability at low cost. can do.

[Brief description of the drawings]

FIG. 1 is a perspective view of a printed circuit board on which electric circuit components are mounted.

FIG. 2 is a perspective view of a conductive terminal.

3A is a plan view of the circuit protection device. FIG. 3B is a cross-sectional view of the circuit protection device taken along line bb in FIG.

FIG. 4 is a circuit diagram illustrating one embodiment.

FIG. 5 is a plan view of a conventional circuit protection device.

[Explanation of symbols]

 P Printed circuit board D Electric circuit component T Conductive terminal 1 Circuit protection device 2 Flat plate part 3 Tip part 4 Side plate part 5 Power supply line 6 Ground line 7 Through hole 8 Through hole 9 Transformer 10 Photocoupler 11 Operational amplifier IC 12 Ground resistance

Claims (5)

[Claims] 1. A circuit protection device comprising a pair of conductive terminals connected to a power supply node and a ground node of an electric circuit supplied from an external power supply and having leading ends facing each other with a space therebetween. 2. A printed circuit board in which a pair of conductive terminals whose leading ends face each other with a space therebetween are connected to a power supply line and a ground line supplied from an external power supply. 3. The printed circuit board according to claim 2, wherein a plurality of sets of the conductive terminals are provided. 4. The printed circuit board according to claim 2, wherein a through hole is formed in a portion between the power supply line and the ground line, and a tip end of the conductive terminal is opposed in the through hole. . 5. The printed circuit board according to claim 2, wherein at least one of said conductive terminals is formed integrally with a heat sink.