CN113889363A

CN113889363A - Relay circuit device

Info

Publication number: CN113889363A
Application number: CN202110737964.4A
Authority: CN
Inventors: 伊藤孝典
Original assignee: JTEKT Corp
Current assignee: JTEKT Corp
Priority date: 2020-07-03
Filing date: 2021-06-30
Publication date: 2022-01-04
Also published as: DE102021116999A1

Abstract

The present invention provides a relay circuit device (10) which is provided with: mechanical relays (2A, 2B) having normally open contacts (23, 24); semiconductor relays (3A, 3B) connected in series to the mechanical relays (2A, 2B); and a control unit (5) that controls the mechanical relays (2A, 2B) and the semiconductor relays (3A, 3B). Load current (I) when both normally open contacts (23, 24) of mechanical relays (2A, 2B) and semiconductor relays (3A, 3B) are in an on state₁、I₂) And (4) flowing. At the time of energization of the load current (I)₁、I₂) In this case, the control unit (5) brings normally open contacts (23, 24) of the mechanical relays (2A, 2B) into a conductive state prior to the semiconductor relays (3A, 3B). In the case of cutting off the load current (I)₁、I₂) The control unit (5) causes the semiconductor relays (3A, 3B) to be in a cut-off state prior to the normally open contacts (23, 24) of the mechanical relays (2A, 2B).

Description

Relay circuit device

Technical Field

The present disclosure relates to a relay circuit device having a plurality of relays and a control unit that controls the relays.

Background

Conventionally, for example, a programmable controller for controlling a machine tool or other equipment uses a relay circuit device for turning on (conducting) and off (interrupting) a load current for operating an actuator of the machine tool to be controlled. In such a relay circuit device, there is a device in which a relay is duplicated (redundant) so as to reliably cut off a current when a load current is to be cut off.

Patent document 1 describes a relay circuit configured by connecting two mechanical relays in series, in which a common terminal (COM) and a normally open terminal (NO) are electrically connected by energizing a coil, and the common terminal (COM) and a normally closed terminal (NC) are electrically connected when the coil is not energized, and supplying a current to a load when both the common terminal (COM) and the normally open terminal (NO) of the two mechanical relays are in an on state. In the relay circuit, a read-back circuit including a photo coupler is provided in correspondence with each of the two mechanical relays, and the control unit can monitor (monitor) the operating state of each of the mechanical relays.

Patent document 1: japanese patent laid-open No. 2020 and 47556

The mechanical relay includes a fixed contact member and a movable contact member, and switches between an on state and an off state by the movable contact member contacting or separating from the fixed contact member in conjunction with an iron piece operated by a magnetic force generated by an electromagnet. In the mechanical relay, for example, a mechanical life (the number of times of a life when the relay is opened and closed in a state where no electric load is applied) of 1000 ten thousand times, and for example, an electrical life (the number of times of a life when the relay is opened and closed in a state where a rated load is applied) of 10 ten thousand times are defined. However, when arc discharge is generated between the contact members when the movable contact member is brought into contact with the fixed contact member or when the movable contact member is separated from the fixed contact member, even if the number of times is less than the number of times of the life, there is a case where deterioration of electrical characteristics, malfunction, or restoration failure of the contact members occurs.

Even if such a failure occurs, if the relay is duplicated as described above, it is possible to avoid a situation where the current is continuously supplied to the actuator when the equipment should be stopped urgently, for example, but there is a problem that the equipment needs to be stopped for replacing the relay or a cost for replacing the relay is incurred. In particular, in the case of a programmable controller configured by combining various modules, in order to replace a relay that has failed, it is necessary to replace the relay for each output module including a plurality of relay circuits including the relay, and therefore, the cost for replacement increases.

Disclosure of Invention

The present disclosure has been made in view of the above circumstances, and an object thereof is to provide a relay circuit device capable of suppressing generation of arc discharge between contact members of a mechanical relay and reducing a replacement frequency.

In order to achieve the above object, the present disclosure provides a relay circuit device including: a mechanical relay for switching the on state and the off state of the mechanical contact according to a relay control signal; a semiconductor relay connected in series to the mechanical contact; and a control unit that controls the mechanical relay and the semiconductor relay, wherein a load current flows when both the mechanical contact and the semiconductor relay are in an on state, the load current is cut off when at least one of the mechanical contact and the semiconductor relay is in an off state, the control unit brings the mechanical contact into the on state before the semiconductor relay when the load current is supplied, and the control unit brings the semiconductor relay into the off state before the mechanical contact when the load current is cut off.

In order to achieve the above object, the present disclosure provides a relay circuit device including: a first mechanical relay and a second mechanical relay each having a mechanical contact for switching between an on state and an off state according to a relay control signal; a semiconductor relay connected in series to the first mechanical relay and the second mechanical relay; and a control unit that controls the first mechanical relay, the second mechanical relay, and the semiconductor relay, wherein a load current flows when all of the mechanical contact of the first mechanical relay, the mechanical contact of the second mechanical relay, and the semiconductor relay are turned on, the load current is cut off when at least one of the mechanical contact of the first mechanical relay, the mechanical contact of the second mechanical relay, and the semiconductor relay is turned off, the control unit turns the mechanical contact of the first mechanical relay and the mechanical contact of the second mechanical relay on before the semiconductor relay on when the load current is supplied, and the control unit turns the semiconductor relay on before the mechanical contact of the first mechanical relay and the mechanical contact of the second mechanical relay on when the load current is cut off The mechanical contact of the device is in a disconnected state.

According to the relay circuit device of the present disclosure, it is possible to suppress the generation of arc discharge between contact members of a mechanical relay and reduce the replacement frequency.

Drawings

Fig. 1 is a circuit diagram showing an example of a configuration of a relay circuit device according to an embodiment of the present disclosure.

Fig. 2 is a schematic configuration diagram showing an example of a configuration of the input-side mechanical relay, where (a) shows a state where the electromagnet is not energized, and (b) shows a state where the electromagnet is energized.

Fig. 3 is a circuit diagram showing an example of a circuit configuration of the first semiconductor relay.

Fig. 4 is a timing chart showing an operation example of the relay circuit device.

Detailed Description

[ embodiment ]

Embodiments of the present disclosure will be described with reference to fig. 1 to 4. The embodiments described below are intended to be illustrative of preferred specific examples for carrying out the present disclosure, and some of the various technical matters that are technically preferred are also specifically exemplified, but the technical scope of the present disclosure is not limited to the specific examples.

Fig. 1 is a circuit diagram showing an example of a circuit configuration of a relay circuit device according to an embodiment of the present disclosure. The relay circuit device 10 is used for energizing and interrupting load currents to a first load 61 and a second load 62 in an output module 1 of a programmable controller that controls a machine tool or the like. The output module 1 has a plurality of relay circuit arrangements 10, of which one relay circuit arrangement 10 is shown in fig. 1.

The relay circuit device 10 includes: two

mechanical relays

2A, 2B, two

semiconductor relays

3A, 3B, first to sixth photocouplers 41 to 46, and a control unit 5 that controls the

mechanical relays

2A, 2B and the

semiconductor relays

3A, 3B. The control unit 5 outputs a first relay control signal 51 and a second relay control signal 52 to control the

mechanical relays

2A and 2B, and outputs a third relay control signal 53 and a fourth relay control signal 54 to control the

semiconductor relays

3A and 3B.

The control unit 5 simultaneously activates (activates) and deactivates (deactivates) the first relay control signal 51 and the second relay control signal 52, but the first relay control signal 51 and the third relay control signal 53, and the second relay control signal 52 and the fourth relay control signal 54 are respectively output from different control circuits in the control unit 5. That is, the control unit 5 is configured such that these control circuits are duplicated, and when at least one of the control circuits operates normally, the load current to the first load 61 and the second load 62 can be cut off.

The first load 61 and the second load 62 are, for example, electric actuators for operating electromagnetic switches and movable parts of the equipment. The first load 61 is connected to the positive electrode of the first dc power supply 71, and the second load 62 is connected to the positive electrode of the second dc power supply 72. The output module 1 has: a first input terminal 11 connected to the first load 61, a second input terminal 12 connected to the second load 62, a first output terminal 13 connected to the negative pole of the first direct current power supply 71, and a second output terminal 14 connected to the negative pole of the second direct current power supply 72. The output module 1 has a P terminal 15 and an N terminal 16, and the P terminal 15 and the N terminal 16 are connected to a control power supply 8 for operating the

mechanical relays

2A and 2B. The control power supply 8 generates a direct-current voltage of, for example, 24V between the P terminal 15 and the N terminal 16.

Hereinafter, of the two

mechanical relays

2A and 2B, the mechanical relay 2A on the first input terminal 11 and the second input terminal 12 side may be referred to as an input-side mechanical relay 2A, and the mechanical relay 2B on the first output terminal 13 and the second output terminal 14 side may be referred to as an output-side mechanical relay 2B. Among the

semiconductor relays

3A and 3B, the semiconductor relay 3A for turning on and off the load current of the first load 61 may be referred to as a first semiconductor relay 3A, and the semiconductor relay 3B for turning on and off the load current of the second load 62 may be referred to as a second semiconductor relay 3B.

The

mechanical relays

2A and 2B are forced-guided relays having an electromagnet 21, one normally closed contact 22, a first normally open contact 23, and a second normally open contact 24, respectively. When the electromagnet 21 is not energized, the normally closed contact 22 is in an on (conducting) state, and the first normally open contact 23 and the second normally open contact 24 are in an off (disconnecting) state. When the electromagnet 21 is energized, the normally closed contact 22 is turned off, and the first normally open contact 23 and the second normally open contact 24 are turned on. The normally closed contact 22 and the first and second normally

open contacts

23 and 24 are mechanical contacts that switch between an on state and an off state by mechanical contact/non-contact of contact members with each other, respectively.

Fig. 2 is a schematic configuration diagram showing a configuration example of the input-side mechanical relay 2A, where (a) shows a state where the electromagnet 21 is not energized, and (b) shows a state where the electromagnet 21 is energized. The normally-closed contact 22 includes a fixed contact member 221 attached to the fixed plate 201 and a movable contact member 222 attached to the movable plate 202. The first normally-open contact 23 includes a fixed contact member 231 attached to the fixed plate 203 and a movable contact member 232 attached to the movable plate 204. The second normally-open contact 24 includes a fixed contact member 241 attached to the fixed plate 205 and a movable contact member 242 attached to the movable plate 206.

The electromagnet 21, the normally closed contact 22, the first normally open contact 23, the second normally open contact 24, an iron piece 25 disposed to face the electromagnet 21, a return spring 26 for biasing the iron piece 25, and a guide plate 27 linked with the iron piece 25 are housed together in a resin frame 28. When the electromagnet 21 is switched between the energized state and the non-energized state, the iron piece 25 swings around the support shaft 251, and the guide plate 27 moves forward and backward. The iron piece 25 is biased to one side in the rotation direction by a return spring 26. The guide plate 27 connects the iron piece 25 and the

movable plates

202, 204, and 206, and the

movable plates

202, 204, and 206 flex with respect to the

fixed plates

201, 203, and 205, respectively, in conjunction with the movement of the iron piece 25.

When the electromagnet 21 is not energized, the fixed contact member 221 of the normally closed contact 22 is in contact with the movable contact member 222, and the fixed

contact members

231 and 241 of the first normally open contact 23 and the second normally open contact 24 are not in contact with the

movable contact members

232 and 242. When the electromagnet 21 is energized, the fixed contact member 221 of the normally closed contact 22 is separated from the movable contact member 222, and the fixed

contact members

231 and 241 of the first normally open contact 23 and the second normally open contact 24 are in contact with the

movable contact members

232 and 242, respectively. Although not shown, the mechanical relay 2B on the output side is similarly configured.

Fig. 3 is a circuit diagram showing an example of the circuit configuration of the first semiconductor relay 3A. The first semiconductor relay 3A is formed as an IC (Integrated Circuit) in which an IC chip is sealed with a sealing material made of resin or the like, and a Circuit configuration thereof is illustrated together with pin numbers (1 to 6) of the first semiconductor relay 3A in fig. 3.

The first semiconductor relay 3A has a photodiode 31, first and

second photo MOSFETs

32 and 33, and first and

second rectifier diodes

34 and 35. If a current flows from the first pin to the second pin and the photodiode 31 emits light, the first photo MOSFET32 and the second photo MOSFET33 are activated, and a current can flow from the sixth pin to the fourth pin through the first photo MOSFET32 and the second rectifying diode 35 or from the fourth pin to the sixth pin through the second photo MOSFET33 and the first rectifying diode 34. Although not shown, the second semiconductor relay 3B is also configured similarly.

The third relay control signal 53 is input from the control unit 5 to the first pin of the first semiconductor relay 3A. If the third relay control signal 53 is active, current flows from the sixth pin to the fourth pin of the first semiconductor relay 3A. The sixth pin is a current input terminal of the first semiconductor relay 3A, and the fourth pin is a current output terminal of the first semiconductor relay 3A. In addition, the fourth relay control signal 54 is input to the first pin of the second semiconductor relay 3B. If the fourth relay control signal 54 is active, current flows from the sixth pin to the fourth pin of the second semiconductor relay 3B. The sixth pin is a current input terminal of the second semiconductor relay 3B, and the fourth pin is a current output terminal of the second semiconductor relay 3B.

Hereinafter, in the first semiconductor relay 3A, a state in which a current can flow from the sixth pin to the fourth pin is referred to as an on state of the first semiconductor relay 3A, and a state in which a current is interrupted between the sixth pin and the fourth pin of the first semiconductor relay 3A is referred to as an off state of the first semiconductor relay 3A. In the second semiconductor relay 3B, a state in which a current can flow from the sixth pin to the fourth pin is referred to as an on state of the second semiconductor relay 3B, and a state in which a current is interrupted between the sixth pin and the fourth pin of the second semiconductor relay 3B is referred to as an off state of the second semiconductor relay 3B.

The first semiconductor relay 3A is connected in series between the first normally-open contact 23 of the input-side mechanical relay 2A and the first normally-open contact 23 of the output-side mechanical relay 2B. The second semiconductor relay 3B is connected in series between the second normally-open contact 24 of the input-side mechanical relay 2A and the second normally-open contact 24 of the output-side mechanical relay 2B.

When all of the first normally-open contact 23 of the input-side mechanical relay 2A, the first semiconductor relay 3A, and the first normally-open contact 23 of the output-side mechanical relay 2B are in the on state, the load current I is applied to the first load 61₁. The first normally open contact 23 of the input-side mechanical relay 2A, the first semiconductor relay 3A, and the first normally open contact 2 of the output-side mechanical relay 2B3 is turned off, the load current I is set to be the load current₁Is cut off.

When all of the second normally-open contact 24 of the input-side mechanical relay 2A, the second semiconductor relay 3B, and the second normally-open contact 24 of the output-side mechanical relay 2B are turned on, the load current I is supplied to the second load 62₂. When at least one of the second normally open contact 24 of the input-side mechanical relay 2A, the second semiconductor relay 3B, and the second normally open contact 24 of the output-side mechanical relay 2B is turned off, the load current I is applied₂Is cut off.

The first relay control signal 51 output from the control unit 5 is input to the anode terminal of the first photocoupler 41, and the second relay control signal 52 is input to the anode terminal of the second photocoupler 42. When both the first relay control signal 51 and the second relay control signal 52 are asserted, the phototransistors of the first photocoupler 41 and the second photocoupler 42 are both turned on, and the current supplied from the control power supply 8 flows through the electromagnets 21 of the

mechanical relays

2A and 2B, respectively. Thereby, the normally closed contact 22 of each of the

mechanical relays

2A and 2B is turned off, and the first normally open contact 23 and the second normally open contact 24 are turned on.

The current from the control power supply 8 is supplied to the anode terminal of the third photocoupler 43 via the normally closed contact 22 of the mechanical relay 2A on the input side. Further, the current from the control power supply 8 is supplied to the anode terminal of the fourth photocoupler 44 via the normally closed contact 22 of the output-side mechanical relay 2B. When the normally closed contact 22 of the input-side mechanical relay 2A is in an on state, the phototransistor of the third photocoupler 43 is in an on state, and when the normally closed contact 22 of the output-side mechanical relay 2B is in an on state, the phototransistor of the fourth photocoupler 44 is in an on state.

The output signal of the third photocoupler 43 is input to the control section 5 as a first read-back signal 55, and the output signal of the fourth photocoupler 44 is input to the control section 5 as a second read-back signal 56. The first read-back signal 55 and the second read-back signal 56 are pulled up by pull-up

resistors

91 and 92, respectively. The control unit 5 can confirm the operation state of the input-side mechanical relay 2A based on the first read-back signal 55, and can confirm the operation state of the output-side mechanical relay 2B based on the second read-back signal 56.

The sixth pin of the first semiconductor relay 3A is connected to the first normally-open contact 23 of the mechanical relay 2A on the input side, and the fourth pin is connected to the first normally-open contact 23 of the mechanical relay 2B on the output side. In addition, the sixth pin of the first semiconductor relay 3A is connected to the anode terminal of the fifth photocoupler 45 via a resistor 93. A cathode terminal of the fifth photocoupler 45 is connected to the fourth pin of the first semiconductor relay 3A.

In addition, the sixth pin of the second semiconductor relay 3B is connected to the second normally-open contact 24 of the mechanical relay 2A on the input side, and the fourth pin is connected to the second normally-open contact 24 of the mechanical relay 2B on the output side. In addition, the sixth pin of the second semiconductor relay 3B is connected to the anode terminal of the sixth photocoupler 46 via a resistor 94. A cathode terminal of the sixth photocoupler 46 is connected to the fourth pin of the second semiconductor relay 3B.

The output signal of the fifth photocoupler 45 is input to the control unit 5 as a first diagnostic signal 57, and the output signal of the sixth photocoupler 46 is input to the control unit as a second diagnostic signal 58. The first diagnostic signal 57 and the second diagnostic signal 58 are pulled up by pull-up

resistors

95, 96, respectively. The first diagnostic signal 57 is asserted when a potential difference equal to or greater than a predetermined value is generated between the fourth pin and the sixth pin of the first semiconductor relay 3A, and otherwise the first diagnostic signal 57 is de-asserted. When a potential difference equal to or greater than a predetermined value is generated between the fourth pin and the sixth pin of the second semiconductor relay 3B, the second diagnostic signal 58 is asserted, and otherwise the second diagnostic signal 58 is de-asserted.

The first output terminal 13 is connected to the movable contact member 232 of the first normally open contact 23 of the output-side mechanical relay 2B, and the load current I is output from the first output terminal 13₁. The second output terminal 14 is connected to the second constant of the mechanical relay 2B on the output sideThe movable contact member 242 of the open contact 24 outputs the load current I from the second output terminal 14₂。

Fig. 4 is a timing chart showing an operation example of the relay circuit device 10. In fig. 4, the voltage levels of the respective signals are shown by H (high) and L (low). In fig. 4, the first external output signal represents the voltage of the first input terminal 11. In addition, the second external output signal represents the voltage of the second input terminal 12.

When a load current I is supplied to each of the first load 61 and the second load 62₁、I₂At this time, the control unit 5 simultaneously asserts the first relay control signal 51 and the second relay control signal 52 (L → H). As a result, current flows into the electromagnets 21 of the

mechanical relays

2A and 2B, the normally closed contacts 22 of the

mechanical relays

2A and 2B are turned off, and the signal states of the first read-back signal 55 and the second read-back signal 56 change from L to H. Further, the first and second normally

open contacts

23 and 24 of the input-side mechanical relay 2A are turned on simultaneously with the change in the first and second read-

back signals

55 and 56, and the signal states of the first and second

diagnostic signals

57 and 58 are changed from H to L.

The control unit 5 can detect that the

mechanical relays

2A and 2B are operated, that is, the normally closed contact 22 is turned off and the first and second normally

open contacts

23 and 24 are turned on, based on changes in the signal states of the first and second read-

back signals

55 and 56. The control unit 5 can directly detect that the first normally-open contact 23 of the input-side mechanical relay 2A is in the on state from the change in the signal state of the first diagnostic signal 57, and can directly detect that the second normally-open contact 24 of the input-side mechanical relay 2A is in the on state from the change in the signal state of the second diagnostic signal 58.

The control unit 5 detects that the first normally open contact 23 of the input-side mechanical relay 2A is in the on state based on at least one of the first read-back signal 55 and the first diagnostic signal 57, and further detects that the first normally open contact 23 of the output-side mechanical relay 2B is in the on state based on the second read-back signal 56After the on state, the third relay control signal 53 is activated, and the first semiconductor relay 3A is turned on. That is, the load current I is applied to the first load 61₁At this time, the control unit 5 sets the first normally open contact 23 of each of the

mechanical relays

2A and 2B to the on state prior to the first semiconductor relay 3A.

Thus, at the time when the first normally open contact 23 of each of the

mechanical relays

2A and 2B is turned on, the load current I is applied₁Since these first normally open contacts 23 do not flow, the generation of arc discharge at the first normally open contacts 23 can be suppressed.

Further, the control unit 5 turns on the second normally open contact 24 of the input-side mechanical relay 2A based on at least one of the first read-back signal 55 and the second diagnostic signal 58, and turns on the second semiconductor relay 3B based on the fourth relay control signal 54 after detecting that the second normally open contact 24 of the output-side mechanical relay 2B is turned on based on the second read-back signal 56. That is, the load current I is applied to the second load 62₂At this time, the control unit 5 sets the second normally-open contact 24 of each of the

mechanical relays

2A and 2B to the on state before the second semiconductor relay 3B.

Thus, at the time when the second normally open contact 24 of each of the

mechanical relays

2A and 2B is turned on, the load current I is applied₂Since the arc does not flow through these second normally open contacts 24, the generation of arc discharge at the second normally open contacts 24 can be suppressed.

On the other hand, when the load current I is cut off₁、I₂At this time, the control section 5 simultaneously deactivates the first relay control signal 51 and the second relay control signal 52, and the third relay control signal 53 and the fourth relay control signal 54 (H → L). Since the first semiconductor relay 3A and the second semiconductor relay 3B have a higher response speed than the

mechanical relays

2A and 2B, the first relay control signal 51 to the fourth relay control signal 54 are all invalidated at the same time, so that the first semiconductor relay 3A and the second semiconductor relay 3B precede the first normally open contact of each of the mechanical relays 2A and 2B23 and the second normally-open contact 24 are turned off.

Thus, the first normally open contact 23 and the second normally open contact 24 of the

mechanical relays

2A and 2B are turned off prior to the turn-off of the load current I by the first semiconductor relay 3A and the second semiconductor relay 3B₁、I₂Therefore, when the first normally open contact 23 and the second normally open contact 24 are in a state where no current flows, the

movable contact members

232 and 242 are separated from the fixed

contact members

231 and 241. Therefore, the occurrence of arc discharge at the first normally-open contact 23 and the second normally-open contact 24 can be suppressed.

When the signal state of one or both of the first read-back signal 55 and the second read-back signal 56 does not change from L to H even when the first relay control signal 51 and the second relay control signal 52 are enabled, the control unit 5 determines that an abnormality has occurred in the circuit and disables all of the first relay control signal 51 to the fourth relay control signal 54. When the signal state of one or both of the first read-back signal 55 and the second read-back signal 56 is held at H, the control unit 5 determines that an abnormality has occurred in the circuit and disables all of the first relay control signal 51 to the fourth relay control signal 54.

In addition, the load current I is applied by enabling the first relay control signal 51 to the fourth relay control signal 54₁、I₂At this time, the control unit 5 momentarily invalidates the third relay control signal 53 to generate a test pulse, and determines whether or not the signal state of the first diagnostic signal 57 changes at that timing. In this determination, if the signal state of the first diagnostic signal 57 does not change, it is diagnosed that the sixth pin and the fourth pin of the first semiconductor relay 3A are in a short-circuited state. However, even in this case, the load current I can be switched on and off by the

mechanical relays

2A and 2B₁、I₂Therefore, the alarm is prevented from being sent out and the action is continued. The control unit 5 also generates a test pulse for the second semiconductor relay 3B, and diagnoses the operating state of the second semiconductor relay 3B based on the signal state of the second diagnostic signal 58.

(effects of the embodiment)

According to the embodiments of the present disclosure described above, the load current I can be suppressed from being turned on and off₁、I₂Arc discharge is generated in the first normally open contact 23 and the second normally open contact 24 of the

mechanical relays

2A and 2B, and the replacement frequency of the output module 1 can be reduced.

(appendix)

The present disclosure has been described above based on the embodiments, but the embodiments are not limited to the invention according to the claims. In addition, it should be noted that all combinations of the features described in the embodiments are not necessarily essential to means for solving the problems of the invention.

In addition, the present disclosure can be modified as appropriate without omitting a part of the configuration, or adding or replacing the configuration, within a range not departing from the gist thereof. For example, in the above embodiment, the load current I to the first load 61 is switched on and off₁And the load current I of the second load 62₂Although the case of (1) has been described, one of the first load 61 and the second load 62 may be omitted. In the above-described embodiment, the case where the semiconductor relays 3A and 3B are connected in series between the input-side mechanical relay 2A and the output-side mechanical relay 2B has been described, but one of the input-side and output-side

mechanical relays

2A and 2B may be omitted.

Description of the reference numerals

10 … relay circuit arrangement; 21 … an electromagnet; 22 … normally closed contact; 23. 24 … first and second normally open contacts; 2A, 2B … mechanical relays; 3A, 3B … semiconductor relays; 5 … control section; 51 … first relay control signal; 52 … second relay control signal; 53 … third relay control signal; 54 … fourth relay control signal; 55 … a first read-back signal; 56 … second read-back signal; 57 … a first diagnostic signal; 58 … second diagnostic signal; i is₁、I₂… load current.

Claims

1. A relay circuit device is provided with:

a mechanical relay for switching the on state and the off state of the mechanical contact according to a relay control signal;

a semiconductor relay connected in series to the mechanical contact; and

a control unit for controlling the mechanical relay and the semiconductor relay,

when the mechanical contact and the semiconductor relay are both turned on, a load current flows,

the load current is cut off when at least one of the mechanical contact and the semiconductor relay is in a cut-off state,

when a load current is applied, the control unit turns the mechanical contact into an on state prior to the semiconductor relay,

when the load current is cut off, the control unit causes the semiconductor relay to be in a cut-off state prior to the mechanical contact.

2. The relay circuit arrangement of claim 1,

the control unit turns the mechanical contact into a conductive state when a load current is applied, and turns the semiconductor relay into a conductive state after detecting that the mechanical contact is turned into the conductive state based on a change in an input signal.

3. A relay circuit device is provided with:

a first mechanical relay and a second mechanical relay each having a mechanical contact for switching between an on state and an off state according to a relay control signal;

a semiconductor relay connected in series to the first mechanical relay and the second mechanical relay; and

a control unit for controlling the first mechanical relay, the second mechanical relay and the semiconductor relay,

a load current flows when the mechanical contact of the first mechanical relay, the mechanical contact of the second mechanical relay, and the semiconductor relay are all turned on,

a load current is cut off when at least one of the mechanical contact of the first mechanical relay, the mechanical contact of the second mechanical relay, and the semiconductor relay is in a cut-off state,

the control unit turns on the mechanical contact of the first mechanical relay and the mechanical contact of the second mechanical relay prior to the semiconductor relay when a load current is applied,

when the load current is cut off, the control unit causes the semiconductor relay to be in a cut-off state prior to the mechanical contact of the first mechanical relay and the mechanical contact of the second mechanical relay.