JPH07295501A - Pilot lamp circuit - Google Patents

Abstract

PURPOSE:To prevent the dark illumination phenomenon of a light emitting diode from being caused when a multi-core cable becomes long. CONSTITUTION:When the multi-core cable 1 becomes long, coupling electrostatic capacity 5 is generated and a fine leak current is to flow to an LED 2B through the coupling electrostatic capacity 5 as shown by a dotted-line array although a contact point 3B OFF. A resistance 9B which has a resistance value less than the impedance value of the LED 2B is however connected to the LED 2b in parallel, so the majority of the leak current is bypassed through this resistance 9B. The compound resistance of the LED 2B and resistance 9B becomes less than that when only the LED 2B is used, so the voltage across the LED 2B becomes low. Therefore, even if the leak current flows to the LED 2B, the voltage across the LED 2B is lower than a working voltage and no dark illumination phenomenon is caused.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an indicator light circuit used in a switchboard or the like.

[0002]

2. Description of the Related Art In recent years, light emitting diodes (hereinafter referred to as LE
Abbreviated as D. ) Has been used a lot. This is because LEDs have several advantages such as lower power consumption and longer life. A multi-core cable is usually used as a cable for supplying electric power to a plurality of LEDs for the reason of easy wiring work.

FIG. 3 is a circuit diagram of an indicator light circuit constructed using such an LED and a multi-core cable. In this figure, one end of the multi-core cable 1 has two L
The EDs 2A and 2B are connected, and two contacts 3A and 3B corresponding to the LEDs 2A and 2B are connected to the other terminal portion.

These contacts 3A, 3B are controlled to be turned on / off by a control signal from a control circuit (not shown), and thereby the lighting operation of the LEDs 2A, 2B by the power supply from the AC power source 4 is controlled. It is supposed to be done. Then, the contacts 3A and 3B are designed so as to perform the opposite operations. Therefore, when the LED 2A is turned on, the LED 2B is turned off, and when the LED 2A is turned off, the LED 2B is turned on.

However, when the length of the multi-core cable 3 becomes longer than a certain length (for example, 200 m or more), a coupling capacitance 5 as shown in FIG. 4 is generated. Therefore, as a phenomenon peculiar to the AC circuit, a weak leak current from the contact 3A side flows to the LED 2B through the coupling capacitance 5 as shown by a dotted arrow, although the contact 3B is off. It will be.

In this case, since the LED has a higher impedance than the incandescent lamp, even if such a weak current flows, L
The voltage across ED2B tends to increase. Furthermore, L
The ED has a very low touching voltage as compared with the incandescent lamp (for example, the touching voltage of the 110V incandescent lamp is about 60V, whereas the touching voltage of the 110V LED is about 10V), and a small voltage. It has the property of lighting up. Therefore, as a result of the above-described synergistic effect of the LED having a high impedance and the low sensing voltage, the LED 2B is dimly lit by a weak leakage current.

The occurrence of such a dark lighting phenomenon causes a misjudgment or an operation error due to misrecognition of lighting, and various measures have been conventionally implemented in order to avoid this.

To give a representative one of them, the first method is to use an incandescent lamp instead of an LED when the multi-core cable is long. According to this, as described above, since the incandescent lamp has a lower impedance than the LED and has a high moving voltage, it is possible to prevent the decrease in dark lighting.

The second measure is to adopt a so-called buffer relay type circuit configuration as shown in FIG.
In the configuration of FIG. 5, buffer relays 6A and 6B are provided at the positions of the LEDs 2A and 2B in FIG. 3, and the contacts 2A and 7B are connected to the LEDs 2A and 2B.
The LEDs 2A and 2B are turned on by the DC power from the. The LEDs 2A and 2B in this case are DC circuit LEDs.

According to the structure shown in FIG. 5, the operating voltage of the buffer relays 6A and 6B is sufficiently high, so that it can be applied to the case of a long cable.
Since A and 2B are connected in the DC circuit, no leakage current flows, so that the dark lighting phenomenon can be prevented.

[0011]

However, as in the first measure, in order to return the use of the LED to the use of the incandescent lamp, the LED is adopted in consideration of the reduction in power consumption and the long life. Contrary to its purpose, it goes against the needs of users and the times. In addition, if the cables are long, incandescent lamps are used, and if they are not, LEDs are used in a mixed manner, which causes a problem in quality control.

On the other hand, according to the second measure, the problem as in the first measure does not occur. However, it is economically disadvantageous because the DC power supply and the buffer relay are provided separately from the AC power supply only for the purpose of lighting the indicator light, and the circuit configuration is complicated. It has the problem of becoming a thing.

The present invention has been made in view of the above circumstances and is premised on the use of an LED as an indicator lamp.
It is an object of the present invention to provide an indicator light circuit capable of effectively preventing the occurrence of a dark lighting phenomenon of an LED even when the cable becomes long.

[0014]

As a means for solving the above-mentioned problems, the invention according to claim 1 is to connect a plurality of light emitting diodes to one end of a multi-core cable and to connect the other end to the other end. Is a display lamp circuit that connects a plurality of contacts corresponding to each light emitting diode and controls the lighting operation of each light emitting diode by the power supply from an AC power source by controlling the ON / OFF of each contact. In addition, a dark lighting current bypass means having a lower impedance than this light emitting diode is connected.

According to a second aspect of the present invention, in the first aspect of the invention, the dark lighting current bypass means is capable of varying the impedance.

According to a third aspect of the present invention, in the first or second aspect of the invention, each of the light emitting diodes and each of the dark lamp current bypass means are integrated in a light emitting diode case. is there.

[0017]

In the structure according to the first aspect of the present invention, when the multi-core cable becomes long, a coupling capacitance is generated, so that a leakage current, that is, a dark lighting current tends to flow to the light emitting diode whose contact is off. However, since a dark lighting current bypass means having a lower impedance than this is connected in parallel to each light emitting diode, a large amount of leakage current flows to the dark lighting current bypass means.

Further, since the combined resistance of the light emitting diode and the dark lighting current bypass means is smaller than that of the light emitting diode alone, the voltage across it is lowered. As a result, even if a leak current flows through the light emitting diode, the voltage across the light emitting diode can be suppressed to the operating voltage or lower, and the dark lighting phenomenon can be prevented.

Further, the coupling capacitance changes according to the length of the multi-core cable, and the leakage current also changes. According to the invention of claim 2, the impedance of the dark lighting current bypass means is freely adjusted. Since it is possible, it is possible to easily deal with such a case.

According to the third aspect of the invention, since the dark lighting current bypass means is attached to each light emitting diode from the beginning and these are integrally housed in the light emitting diode case, the wiring work at the site is performed. Etc. can be performed easily.

[0021]

Embodiments of the present invention will be described below with reference to FIGS. 1 and 2. However, the same components as those in FIG. 3 to FIG.

FIG. 1 is a circuit diagram of an indicator light circuit according to this embodiment. In this figure, LEDs 2A and 2B are provided with resistors 9A and 9B as dark lighting current bypass means, respectively.
Are connected in parallel. The resistance values of the resistors 9A and 9B are lower than the impedance of the LEDs 2A and 2B. In this embodiment, for example, the LEDs 2A, 2B (A
The impedance of C110V) is set to 6.7 kΩ, and the resistance values of the resistors 9A and 9B are set to 1.2 kΩ.

Next, the operation of this embodiment having such a configuration will be described. When the multi-core cable 1 becomes long, a capacitance 5 is generated as shown in FIG. Contact 3A now
Considering the case where the contact is on and the contact 3B is off, the LED 2A
A current as indicated by a solid arrow flows through the resistor 9A. At this time, although a little extra power is consumed in the resistor 9A, the voltage of the AC power supply 4 of 100 V is applied to both ends of the LED 2A, so that the brightness of the LED 2A does not decrease and no inconvenience occurs.

On the other hand, the leakage current indicated by the dotted arrow flows into the LED 2B and the resistor 9B through the coupling capacitance 5. In this case, the shunting ratio of the leakage current to the LED 2B and the resistor 9B is the reciprocal ratio of the impedance value and the resistance value, so that a large leakage current flows in the resistor 9B.

Since the combined resistance of the LED 2B and the resistor 9B is smaller than that of the LED 2B alone, the voltage across the LED 2B when a leakage current flows is also reduced.

From the above, if the resistance value of the resistor 9B is appropriately selected according to the magnitude of the leakage current, the LED 2
The voltage between both ends of B can be suppressed to be equal to or lower than the sensing voltage, and the occurrence of the dark lighting phenomenon can be prevented.

In the above-mentioned embodiment, an example in which the resistance value is fixed to the resistors 9A and 9B is shown, but the resistance value can be freely variably adjusted. Good. According to this, when the indicator light circuit is applied to a switchboard or the like, even if the length of the multi-core cable 1 is variously changed and the leakage current is changed, it can be easily dealt with.

Further, in order to facilitate the wiring work, the LED
Each of 2A and the resistor 9A and the LED 2B and the resistor 9B may be integrated in the LED case.

Further, in the above-mentioned embodiment, the example in which the resistor is used as the bypass means for the dark lighting current is shown, but the reactor may be used.

[0030]

As described above, according to the present invention, the multi-core cable is made long by a simple structure in which the dark lighting current bypass means such as a resistor is connected in parallel to the light emitting diode. Even in this case, the dark lighting phenomenon of the light emitting diode can be prevented.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is an explanatory diagram of the operation of FIG.

FIG. 3 is a circuit diagram showing a configuration of a conventional example.

FIG. 4 is an explanatory diagram of the operation of FIG.

FIG. 5 is a circuit diagram showing the configuration of another conventional example.

[Explanation of symbols]

 1 Multi-core cable 2A, 2B LED (light emitting diode) 3A, 3B contact point 4 AC power supply 9A, 9B resistance (dark lighting current bypass means)

Claims (3)

[Claims] 1. A multi-core cable, wherein a plurality of light emitting diodes are connected to one end of the multi-core cable, and a plurality of contacts corresponding to the respective light emitting diodes are connected to the other end of the multi-core cable. In a display lamp circuit for controlling a lighting operation of each light emitting diode by power supply from a power source, a dark lighting current bypass means having an impedance lower than that of the light emitting diode is connected in parallel to each light emitting diode. Indicator light circuit. 2. The indicator light circuit according to claim 1, wherein the dark lighting current bypass means is capable of varying the impedance. 3. The indicator light circuit according to claim 1, wherein each of the light emitting diodes and each of the dark lamp current bypass means are integrally incorporated in a light emitting diode case.