JPH02161811A - Solid state relay - Google Patents

Abstract

PURPOSE:To automatically stop the signals of the output side with generation of an overload by preparing a circuit which turns off a main switch element with the output of a comparator via an output cut-off circuit when an overcurrent flows to a load current and at the same time actuates an overcurrent informing means set outside a relay. CONSTITUTION:A self-support circuit 14 which works with the output of a comparator 13 outputs no signal as long as the reference voltage is higher than the output voltage of a current transformer. Then an output cut-off circuit 3 is turned off when the output voltage of the current transformer is higher than the reference voltage. Thus an overcurrent informing means like an external buzzer, lamp, etc., connected to the output terminals 15 and 15 of the circuit 14 is actuated. Therefore, the output voltage of the current transformer increases and exceeds the reference voltage in case the load abnormality occurs and an overcurrent flows to a load current. Thus the circuit 14 turns off the circuit 3 and cuts the energization to a photocoupler 4 toturn off a triac 6 and to stop the deive of the load. At the same time, a buzzer or a lamp, etc., set outside a relay is actuated to inform the load abnormality.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a solid state relay, and more particularly to a solid state relay having an automatic detection function for overcurrent flowing through a load.

(b) Conventional technology Solid stay 1-relays, which are hybrid integrated circuits that utilize photocouplers, rectifiers, thyristors, etc., do not have overcurrent protection functions built into the relay body, and overcurrent protection There are relays with built-in temperature fuses for this reason, and when using relays with the same name, a fuse or breaker was attached to the outside of the relay.

(c) Problems to be Solved by the Invention However, if the fuse and breaker are separately installed outside the relay, it will take time for wiring, etc., and if the type has a built-in temperature fuse, then - When a fuse blows out, the fuse cannot be replaced because the relay is a hybrid integrated circuit, and the entire solid state relay must be replaced, which is wasteful.

In addition, since none of the above-mentioned types of solid state relays has a mechanism for notifying the outside of the occurrence of an overload, there is a drawback that load abnormalities cannot be detected immediately.

In view of the above-mentioned problems, the present invention aims to provide a solid-state relay that can automatically stop the signal on the output side when an overload occurs and also has a built-in function to notify the outside of a load abnormality.

(d) Means for Solving Problems This invention comprises a current transformer that detects a load current on the output side, a circuit that rectifies and smoothes the output current of this current transformer to convert it into a voltage, and a circuit that converts this converted voltage into a load. A circuit that compares with a reference voltage corresponding to the maximum allowable current value, and when an overcurrent flows in the load current, the output of the comparison circuit turns off the main switch element in the output cutoff circuit, and an overcurrent alarm external to the relay is provided. It features a solid-state relay with built-in circuitry for actuating the means.

<E) Function According to the present invention, when an input signal is supplied via the output cutoff circuit and current is flowing through the load by turning on the main switch element, the current flowing through the load is taken out by the current transformer, and the voltage is increased. It is compared with the reference voltage by conversion,
When an overcurrent flows in the load current due to a load abnormality, the output cutoff circuit is turned OFF by the output of the comparison circuit, and the current supply to the output side is automatically stopped, and the overcurrent notification means such as buzzer run 1 outside the relay is activated. A load abnormality is reported.

(f) Effects of the Invention Accordingly, since a load abnormality is immediately notified to the outside of the relay, the occurrence of an overload can be quickly known.

In addition, since the relay has a built-in overcurrent protection function,
It is possible to eliminate the trouble of wiring a fuse and a breaker to the relay, and since the overcurrent protection function is not a temperature fuse, there is no need to replace the relay even if an overcurrent occurs.

(g) Examples An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment circuit of a solid state relay according to the present invention, in which an input signal applied from input terminals 1 and 1 flows to a photocoupler 4 via an input circuit 2 and an output cutoff circuit 3. A trigger signal is generated by a trigger circuit 5, and the trigger signal is applied to the gate of a triac 6 to turn on the triac 6 and energize a load (not shown) connected to an output terminal 7.7. 8 is a snubber circuit.

A current transformer 9 is provided on the output side of the relay to take out the current flowing to the load by the triac 6, and the load current taken out by the current transformer is passed through a rectifier circuit 10 and a smoothing circuit 11.
After flowing through the current transformer, it is converted into a voltage using a load resistor 12, and this current transformer output voltage is applied to one input terminal of a comparator 13.

A reference voltage is applied to the other input terminal of the comparator 13 from the input circuit 2, and the magnitude of this reference voltage corresponds to the maximum allowable value of the load current.

A self-holding circuit 14 operated by the output of the comparator 13 does not output a signal while the reference voltage exceeds the current transformer output voltage, and shuts off the output when this relationship is reversed and the current transformer output voltage exceeds the current transformer output voltage. An external buzzer connected to the output terminal 15°15 of the self-holding circuit 14 turns off the circuit 3;
Activate overcurrent alarm means (not shown) such as a lamp.

Therefore, when no load abnormality occurs, the reference voltage is always higher than the current transformer output voltage, so the input signal flows to the photocoupler 4, and the photocoupler 4 connects to the trigger circuit 5.
The triac 6 is driven by this, and current continues to flow through the load. However, when a load abnormality occurs and an overcurrent flows in the load current, the current transformer output voltage increases and exceeds the reference voltage, so the self-holding circuit lI@14 turns off the output cutoff circuit 3 and passes it to the photocoupler 4. The TRIAC 6 is turned off by cutting off the power supply, and the load is stopped. At the same time, a buzzer, lamp, etc. outside the relay is activated to notify of load abnormality.

If a hybrid integrated circuit solid state relay is constructed using the circuit configuration shown in FIG. 1 as described above, it is possible to stop the load current supply when a load abnormality occurs and to notify the outside of the relay that the load abnormality has occurred.

In the correspondence between the configuration of the present invention and the embodiments described above, the output cutoff circuit of the present invention corresponds to the output cutoff rat path 3 of the embodiment, and similarly, the main switch elements correspond to l to RIAC 6. The current transformers correspond to currents 1 to lances 9, the circuits for rectifying and smoothing voltage conversion correspond to rectifier circuit 10, smoothing circuit 11, and load resistor 12, respectively, and the circuit for comparison corresponds to comparator 13. Correspondingly, the circuit that cuts off the current supply with the output cutoff circuit and activates the overcurrent alarm means outside the relay corresponds to the self-holding circuit 14. However, the present invention is limited to the configuration of the above-described embodiment. It is not something that will be done.

[Brief explanation of the drawing]

The drawings show a solid example of the invention, and FIG. 1 is a circuit diagram of a solid state relay. 3... Output cutoff circuit 6... Triac 9.
... Current transformer 11 ... Smoothing circuit 13 ... Comparator 10 ... Rectifier circuit 12 ... Load resistor 14 ... Self-holding circuit

Claims (1)

[Claims] (1) A solid-state relay that uses an input signal to turn on the main switch element via an output cutoff circuit to flow current to the load on the output side, and includes a current transformer that detects the load current on the output side, and this current transformer. A circuit that rectifies and smoothes the output current to convert it into a voltage, a circuit that compares this converted voltage with a reference voltage corresponding to the maximum allowable value of the load current, and a circuit that performs the above comparison when an overcurrent flows in the load current. A solid-state relay that includes a built-in circuit that turns off the main switch element using the output cutoff circuit according to the circuit output, and also activates an overcurrent alarm means external to the relay.