JPH0629804A - Zero cross switching relay - Google Patents

Abstract

PURPOSE:To obtain the zero cross switching relay with less heat evolution from which noise hardly takes place with simple configuration. CONSTITUTION:A contact 20 of an electromagnetic relay and a 2-way thyristor 21 of light trigger type are connected in parallel, and after the contact 20 is opened, the thyristor 21 is subject to zero cross turn-off. When the thyristor is turned on and a voltage between output terminals 3,4 is dropped, an optical signal of light emitting diodes 18,19 is lost, a photo transistor(TR) 14 is turned off and power is supplied to a coil 15 of an electromagnetic relay and a light emitting diode 16 to allow the thyristor 21 to be in zero cross turn-on. As a result, since a main current is obtained via a contact of the electromagnetic relay, heat evolution is less and since turning-on and turning-off are implemented in the vicinity of a zero cross point, noise production is less and the relay is manufactured inexpensively with simple configuration.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zero-cross switching relay that fires only near the zero-cross point of an AC power supply.

[0002]

2. Description of the Related Art Conventionally, semiconductor relays have been widely used for switching large electric power with a small electric power control signal. Compared with electromagnetic relays, semiconductor relays have the advantage that they have a long life because they have no contacts, but on the other hand,
There is a drawback that a large amount of heat is generated due to a voltage drop during energization. Therefore, as shown in FIG. 3, the relay output terminals 3, 4
In the meantime, a contact 7 of the electromagnetic relay and a semiconductor switching element 8 (for example, a bidirectional thyristor) are connected in parallel, and energization is performed by the contacts 6 and 7 of the electromagnetic relay. There is a relay. However, there is a problem that noise is likely to occur when the energizing operation is performed at a timing when the rate of change in voltage or current is large.

In order to reduce the above-mentioned generated noise, Japanese Patent Publication No. Sho 60-1782 discloses a three-terminal thyristor.
A switching circuit composed of front-stage, middle-stage, and rear-stage contacts that operate at different timings according to an input signal and a zero-cross trigger circuit is disclosed, but a zero-cross that generates a trigger signal near the zero-cross point of the load current is disclosed.・ Since the trigger circuit is required, the actual circuit configuration is complicated.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and it is an object of the present invention to reduce heat generation by conducting a main current through a contact of an electromagnetic relay. At the same time, it is another object of the present invention to provide a zero-cross switching relay having a simple structure, which reduces noise generation by the zero-cross switching.

[0005]

In order to solve the above-mentioned problems, in the zero-cross switching relay of the present invention, as shown in FIG. 1, a contact 20 of a normally open type electromagnetic relay and light irradiation are used. The firing bidirectional thyristor 21 and the first light emitting diodes 18 and 19 are connected in parallel between the relay output terminals 3 and 4, and the second light emitting diode 11 is connected between the relay input terminals 1 and 2. First
And the collectors of the second phototransistors 13 and 14 are connected to the first DC power supply terminal 22 via the resistor 12,
Of the phototransistor 13 is optically coupled to the second light emitting diode 11, and the emitter of the phototransistor 13 is optically coupled to the exciting coil 15 of the normally open electromagnetic relay and the bidirectional thyristor 21. Diode 1
6 are connected in series to the second DC power supply terminal 23, the second phototransistor 14 is optically coupled to the first light emitting diodes 18 and 19, and the emitter thereof is the second DC power supply. It is characterized in that it is connected to the terminal 23.

[0006]

The operation of the circuit shown in FIG. 1 will be described below. First, when no input signal is applied between the relay input terminals 1 and 2, no current flows in the phototransistor 13,
Therefore, neither the relay contact 20 nor the light-ignition bidirectional thyristor 21 is in a conductive state, and the relay output terminals 3 and 4 are in an off state. At this time, the light emitting diodes 18 and 19 emit light by the AC voltage applied between the output terminals 3 and 4 via the load, and the phototransistor 14
A current as represented by an AC full-wave rectified waveform is flowing through.

Next, when an input signal is applied between the relay input terminals 1 and 2, a current flows through the phototransistor 13, but at a timing when the current flowing through the phototransistor 14 is large, that is, between the relay output terminals 3 and 4. Since the coil 15 and the light emitting diode 16 are connected to the emitter side of the phototransistor 13 at the timing when the voltage is high, the value of the current flowing through the phototransistor 13 is small, and the contact 20 of the electromagnetic relay and the bidirectional thyristor for the light ignition. All 21 are off. When the voltage between the relay output terminals 3 and 4 decreases, the current flowing through the phototransistor 14 decreases. As a result, the current flowing through the phototransistor 13 increases, the contact 20 of the electromagnetic relay and the bidirectional thyristor 21 for light ignition are turned on, the relay output terminals 3 and 4 are turned on, and the zero-cross turn-on operation is performed. I do. When the relay output terminals 3 and 4 are turned on, no current flows in the light emitting diodes 18 and 19,
No current flows through the phototransistor 14.

When the input signal between the relay output terminals 1 and 2 is cut off, no current flows in the phototransistor 13. At this time, the contact 20 of the electromagnetic relay immediately becomes non-conductive, but the light-ignition bidirectional thyristor 21 maintains the conductive state for up to half a cycle until the value of the flowing current becomes almost zero, and then becomes non-conductive. Become, zero cross
Turn off operation is performed.

[0009]

FIG. 1 is a circuit diagram of an embodiment of the present invention. The circuit configuration will be described below. A light emitting diode 11 is connected between the relay input terminals 1 and 2.
Between the relay output terminals 3 and 4, a contact 20 of a normally open type electromagnetic relay, a bidirectional thyristor 21 ignited by light irradiation, and two light-emitting diodes 18 and 19 connected in anti-parallel to a resistor 17 Are connected in parallel with a circuit in which is connected in series. Two phototransistors 13 and 14
The collector of is connected to the DC power supply terminal 22 via the resistor 12. One phototransistor 13 is optically coupled to the light emitting diode 11 between the relay input terminals 1 and 2. The emitter of the phototransistor 13 has an exciting coil 15 of the normally open electromagnetic relay.
Is connected to the light emitting diode 16 optically coupled to the bidirectional thyristor 21, and the light emitting diode 16 is connected to the DC power supply terminal 23. The other phototransistor 14 is optically coupled to the light emitting diodes 18 and 19 between the relay output terminals 3 and 4, and its emitter is connected to the DC power supply terminal 23.

FIG. 2 is an operation waveform diagram of this embodiment. In the figure, (a) is a load voltage waveform, (b) is an input signal waveform, (c) is a current waveform of the light emitting diodes 18, 19,
(D) is a waveform of current flowing through the exciting coil 15 and the light emitting diode 16, (e) is a waveform of current flowing through the contact 20 of the electromagnetic relay, (f) is a waveform of current flowing through the bidirectional thyristor 21, and (g) is It is a waveform of a load current.

The operation of this embodiment will be described below.
First, when the input signal is not applied between the relay input terminals 1 and 2, the light emitting diode 11 does not emit light, and the current does not flow in the phototransistor 13. Therefore, the relay contact 20 and the light ignition type bidirectional Neither of the thyristors 21 is conductive, and the relay output terminals 3 and 4 are off. At this time, due to the AC voltage applied between the relay output terminals 3 and 4 via the load, the light emitting diode 1
8 and 19 emit light, and a current as represented by an AC full-wave rectified waveform flows through the phototransistor 14.

Next, when an input signal is applied between the relay input terminals 1 and 2, the light emitting diode 11 emits light and a current flows through the phototransistor 13, but the phototransistor 1
At the timing when the current flowing through 4 is large, that is, when the voltage between the relay output terminals 3 and 4 is large, since the exciting coil 15 and the light emitting diode 16 are connected to the emitter side of the phototransistor 13, the current flows through the phototransistor 13. The current value is small and the contact 2 of the electromagnetic relay
0, the light-ignition type bidirectional thyristors 21 are all off. When the voltage between the relay output terminals 3 and 4 decreases, the current flowing through the phototransistor 14 decreases,
The current flowing through the phototransistor 13 increases, and the contact 20 of the electromagnetic relay and the light ignition type bidirectional thyristor 21 become conductive. That is, the zero-cross turn-on operation is performed between the relay output terminals 3 and 4. Relay output terminals 3, 4
When the interval is turned on, no current flows in the light emitting diodes 18 and 19, and no current flows in the phototransistor 14.

Next, when the input signal between the relay input terminals 1 and 2 is cut off, the optical signal of the light emitting diode 11 disappears and the current stops flowing through the phototransistor 13. At this time, the contact 20 of the electromagnetic relay immediately becomes non-conductive, but the light-ignition bidirectional thyristor 21 maintains the conductive state for up to half a cycle until the value of the flowing current becomes almost zero, and then becomes non-conductive. Then, the zero-cross turn-off operation is performed.

In the circuit shown in FIG. 1, two light firing type reverse blocking three-terminal thyristors may be connected in antiparallel instead of the light firing type bidirectional thyristor 21.

[0015]

As described above, in the zero-cross switching relay of the present invention, since the main current is passed through the contact of the electromagnetic relay, the heat generation is small, and the turn-on operation and the turn-off operation are at the zero-cross point. Since it is performed in the vicinity, there is little noise generation, and a zero-cross switching relay can be realized simply by combining a normally open type electromagnetic relay and a light ignition type thyristor with a phototransistor and a light emitting diode, so the configuration is simple. There is an effect that it can be manufactured at low cost.

[Brief description of drawings]

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

FIG. 2 is an operation waveform diagram of an embodiment of the present invention.

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

[Explanation of symbols]

 1, 2 Relay input terminal 3, 4 Relay output terminal 11 Light emitting diode 12 Resistor 13 Phototransistor 14 Phototransistor 15 Excitation coil of electromagnetic relay 16 Light emitting diode 17 Resistor 18 Light emitting diode 19 Light emitting diode 20 Electromagnetic relay contact 21 Light firing type Bidirectional thyristor

 ─────────────────────────────────────────────────── ─── Continued front page (72) Inventor Hideki Kurizumi 1048, Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Works, Ltd. (72) Masahisa Niwa, 1048, Kadoma, Kadoma, Osaka Prefecture, Matsushita Electric Works, Ltd.

Claims (1)

[Claims] 1. A normally open electromagnetic relay contact, and a bidirectional thyristor ignited by light irradiation.
Connecting the first light emitting means in parallel between the relay output terminals,
The second light emitting means is connected between the relay input terminals, and the collectors of the first and second phototransistors are connected to the first via the resistor.
Of the first phototransistor, and the first phototransistor is optically coupled to the second light emitting means, and its emitter is optically coupled to the exciting coil of the normally open electromagnetic relay and the bidirectional thyristor. The third light emitting means is connected in series and connected to the second DC power supply terminal.
A zero-cross switching relay characterized in that the phototransistor is optically coupled to the first light emitting means and the emitter thereof is connected to the second DC power supply terminal.