JPH11134992A - Relay switching circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably operate a circuit while improving lifetime of a contact of a relay by connecting a semi-conductor relay to a relay circuit for switching a mechanical relay in series to each other. SOLUTION: A reed relay 2 is connected to a semi-conductor relay 11, which is connected to a load 1, in series to each other, and a load side measuring circuit 12 having a control circuit for switching the reed relay 2 after opening the semi-conductor relay 11 inside thereof is connected in series. In the condition that the semi-conductor relay 11 is opened, contact current of the reed relay 2 is cut, and the reed relay 2 is switched so as to limit the current to the only current flowing during the time when the semi-conductor relay 11 is opened. Consequently, since the contact current at the time of switching the reed relay 2 can be made remarkably small, lifetime can be improved. Since the leaked current generated from the semi-conductor 11 is cut by the reed relay 2, even in an electrical circuit having a trouble of current leakage, a characteristic of the electrical circuit is satisfied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a relay switching circuit, and more particularly, to a relay switching circuit capable of extending a switching life of a mechanical relay.

[0002]

2. Description of the Related Art Hitherto, a switching circuit using a relay has been used for switching a circuit to be measured or switching a signal inside a circuit by opening and closing a mechanical relay such as a mechanical relay or a reed relay.

FIG. 2 is a block diagram showing a conventional relay switching circuit. In the figure, reference numeral 1 denotes a load, 2 is connected to a load 1, and the lead 1 (electric contact) is opened and closed to open and close the load 1 from the load 1. A reed relay 3 for interrupting the current is a load measuring circuit connected to the reed relay 2 and measuring the electrical characteristics of the load 1. In this relay switching circuit,
The reed relay 2 is opened and closed to interrupt the current from the load 1, and the electrical characteristics of the load 1 are measured by the load measuring circuit 3.

Generally, a relay used in an electric circuit has a life. Particularly, in a mechanical relay such as the above-described reed relay 2 and mechanical relay, the life is extended due to the magnitude of a current (contact current) flowing through an electric contact. It is known to change. FIG. 3 is a DC load life characteristic diagram showing the relationship between the contact switching current and the number of life operations at each switching DC voltage of the contacts when the relay is opened and closed. FIG. FIG. 4 is an AC load life characteristic diagram showing a relationship between a contact switching current at a voltage and the number of life operations. In these figures, the time constant or the power factor and the load voltage are used as parameters for the inductive load.

From these FIGS. 3 and 4, it is understood that the life of the relay tends to be shorter as the contact switching current at the time of opening and closing the relay is larger. The life of the relay is preferably reduced with the contact switching current as small as possible. It is clear that it will extend.

[0006]

Incidentally, a conventional relay may be used with a contact current flowing depending on the circuit configuration. In this case, there is a problem that the life of the relay becomes extremely short, and the failure rate of the entire circuit is determined by the life of the relay.

For example, in the above-described relay switching circuit, when the reed relay 2 is closed, a contact current is flowing through the reed relay 2, and when the reed relay 2 is opened and closed in this state, 3 and 4
As shown in the load life characteristics, the contact current shortens the life. As an example, when the reed relay 2 has the life curve of FIG. 5, if the magnitude of the contact current is 2 A at 24 VDC, the life is about 100,000 times.

On the other hand, the life of a semiconductor relay is generally said to be semi-permanent, and when the reed relay 2 is replaced with a semiconductor relay, the life becomes semi-permanent, but a leakage current flows when the semiconductor relay is opened. For this reason, the load measuring circuit 3 causes a measurement error due to the leakage current of the semiconductor relay in the load measuring circuit 3, for example, when several loads are switched and measured by a relay. Therefore, in a circuit where leakage current is a problem, semiconductor relays cannot be used because the characteristics cannot be satisfied, and a reed relay in which leakage current does not flow is used in the circuit, knowing that the life will be shortened. There was a problem that it had to be used.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a relay switching circuit which can extend the contact life of a relay and can stably operate the circuit for a long period of time. And

[0010]

In order to solve the above problems, the present invention provides the following relay switching circuit.
That is, the relay switching circuit according to claim 1 is a relay switching circuit that switches a circuit, a signal, and the like by opening and closing a mechanical relay, wherein a semiconductor relay is connected in series to the mechanical relay. It is.

According to a second aspect of the present invention, in the relay switching circuit, the mechanical relay and the semiconductor relay are provided with a control circuit that opens and closes the mechanical relay after the semiconductor relay is opened.

In the relay switching circuit of the present invention, a semiconductor relay having a semi-permanent life is connected in series to a mechanical relay through which no leakage current flows, and the contact of the mechanical relay is opened by opening the semiconductor relay. After interrupting the current,
Open and close the mechanical relay. Here, since the semiconductor relay is opened first, the current that flows when the mechanical relay is opened and closed is only the leakage current that flows when the semiconductor relay is opened. Since this leakage current is a very small current, opening and closing the mechanical relay in this state extends the life of the mechanical relay.

[0013] Further, by cutting off the leakage current generated from the semiconductor relay by the mechanical relay, it is possible to satisfy the characteristics even in an electric circuit in which the leakage current becomes a problem.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a relay switching circuit according to the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram showing a relay switching circuit according to an embodiment of the present invention. In the figure, reference numeral 11 denotes a semiconductor relay connected to a load 1 and 2 denotes a reed relay (mechanical relay) connected in series to the semiconductor relay 11. And 12 are load measuring circuits connected to the reed relay 2 and measuring the electrical characteristics of the load 1.

As the semiconductor relay 11, a photo MOS relay or the like is preferably used. The reed relay 2 can be replaced with a mechanical relay such as another mechanical relay. The load measuring circuit 12 has a semiconductor relay 1 therein.
A control circuit is provided for opening and closing the reed relay 2 after opening the first relay 1.

In this relay switching circuit, when the reed relay 2 and the semiconductor relay 11 are closed, a contact current flows through the reed relay 2 and the semiconductor relay 11 due to the load 1. Here, when the reed relay 2 is opened and closed, first, the contact current of the reed relay 2 is set to only the leakage current of the semiconductor relay 11 by opening the semiconductor relay 11. Next, after the semiconductor relay 11 is opened, the reed relay 2 is opened and closed. Thereby, the contact life of the reed relay 2 can be extended, and the circuit can be operated stably for a long time.

For example, when the reed relay 2 has the life curve shown in FIG. 5, the magnitude of the contact current of the reed relay 2 after opening the semiconductor relay 11 is several μA or less. Therefore, the life is extended 100 times or more as compared with the case where the contact current of the reed relay 2 of the conventional relay switching circuit is DC 24V, 2A.

According to the relay switching circuit of the present embodiment, the reed relay 2 is connected in series to the semiconductor relay 11 connected to the load 1, and after the semiconductor relay 11 is opened inside, the reed relay 2 is opened and closed. Since the load measurement circuit 12 provided with a control circuit for controlling the reed relay 2 is connected in series, the contact current of the reed relay 2 is cut off with the semiconductor relay 11 opened, and the reed relay 2 is opened and closed. The current flowing through the semiconductor relay 11
Can be limited to the leakage current flowing when the reed relay 2 is opened, the contact current when the reed relay 2 is opened and closed can be made extremely small, and the life of the reed relay 2 can be extended.

Further, since the reed relay 2 blocks the leakage current generated from the semiconductor relay 11, the characteristics of the electric circuit can be satisfied even in an electric circuit in which the leakage current is a problem.

In the relay switching circuit of the present embodiment, a control circuit for opening and closing the reed relay 2 after opening the semiconductor relay 11 in the load measuring circuit 12 is provided. Is a semiconductor relay 11
In addition, any configuration may be used as long as it controls the reed relay 2, and may be provided separately outside the load measurement circuit 12.

[0021]

According to the relay switching circuit of the present invention,
Since a semiconductor relay was connected in series with a mechanical relay,
When the semiconductor relay is opened and the mechanical relay contact current is cut off, the mechanical relay is opened and closed. Only, the contact current when opening and closing the mechanical relay can be made very small, and the life of the mechanical relay can be extended.

Further, since the leakage current generated by the semiconductor relay is interrupted by the mechanical relay, the characteristics can be satisfied even in an electric circuit in which the leakage current is a problem.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating a relay switching circuit according to an embodiment of the present invention.

FIG. 2 is a configuration diagram showing a conventional relay switching circuit.

FIG. 3 is a DC load life characteristic diagram showing a relationship between a contact switching current and a life operation count at each switching DC voltage of a relay contact.

FIG. 4 is an AC load life characteristic diagram showing a relationship between a contact switching current and a life operation count at each switching AC voltage of a relay contact.

FIG. 5 is a life characteristic diagram showing a relationship between a contact current and a life of a reed relay in a DC and AC resistive load.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Load 2 Reed relay 3 Load measurement circuit 11 Semiconductor relay 12 Load measurement circuit

Claims (2)

[Claims] 1. A relay switching circuit for switching a circuit or a signal by opening and closing a mechanical relay, wherein a semiconductor relay is connected in series to the mechanical relay. 2. The relay switching circuit according to claim 1, wherein the mechanical relay and the semiconductor relay are provided with a control circuit for opening and closing the mechanical relay after opening the semiconductor relay.