JPS6359569B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a solid state relay that can be easily deployed in both AC and DC output circuits.

FIG. 1 shows a conventional solid state relay circuit. In the conventional circuit shown in the figure, a light emitting element 1 made of a light emitting diode is constantly emitted by an input signal, and a load circuit is switched through a photothyristor 2 ignited by the light from the light emitting element 1. However, since such a conventional circuit always causes the light emitting element 1 on the input side to emit light, there is a problem in terms of power consumption when using a power source with a limited capacity such as a storage battery or dry cell battery. Even when there is no power supply, there is wasteful power consumption, which is uneconomical. Note that 3 in the figure is a drive circuit for the photothyristor 2.

The present invention was made in view of the above-mentioned problems, and its purpose is to provide a solid state relay that has extremely low input power consumption and can be easily applied to both AC output and DC output circuits. is to provide.

The present invention will be explained below with reference to Examples. FIG. 2 shows an embodiment of a DC output type circuit, where A is an input circuit and B is an output circuit. Input circuit A includes a capacitor C ₁ between signal input terminals Ia and Ib, a first light emitting element LED ₁ consisting of a light emitting diode, and a diode D ₁ .
At the same time, a second light emitting element LED ₂ consisting of a light emitting diode in the opposite direction to the first light emitting element LED ₁ is connected in parallel to the first light emitting element LED ₁ , and a transistor Tr ₁ is connected in parallel to the first light emitting element LED 1. the capacitor
It is connected in parallel to the second light emitting element LED ₂ via C ₁ . In the figure, _R1 is the base resistance. On the other hand, output circuit B has a photothyristor between output terminals Oa and Ob.
SCR is connected, and a phototransistor Ph is connected between the gate and cathode of the photothyristor SCR.
Furthermore, a parallel circuit consisting of a resistor R ₂ and a capacitor C ₂ is connected to the phototransistor Ph. The photothyristor SCR constitutes a photocoupler with the first light emitting element LED ₁ , and the phototransistor
Ph constitutes a photocoupler with the second light emitting element LED ₂ , and the driving power for these is supplied from the DC power supply DE connected between the output terminals Oa and Ob via a load RL.

Now, when the input signal Vi is connected between the input terminals Ia and Ib as shown in Fig. 3a, the capacitor C ₁ ,
A charging current i of the capacitor C ₁ flows instantaneously through the circuit of the first light emitting element LED ₁ and the diode D ₁ as shown in FIG. 3b, and the light emitting element LED ₁ instantaneously emits light. The photothyristor SCR is ignited and turned on by this light emission, and a current flows through the photothyristor SCR to the load RL as shown in FIG. 3c. The photothyristor SCR is kept on from then on.

Next, when the input signal Vi is no longer input, the discharge current of the capacitor C ₁ flows through the base resistor R ₁ to the base of the transistor Tr ₁ , and the transistor Tr ₁
turns on. This turns on capacitor C ₁ ,
The discharge current of the capacitor C ₁ flows through the closed circuit of the transistor Tr ₁ and the light emitting element LED ₂ , the light emitting element LED ₂ emits light, and the phototransistor Ph is turned on. Due to this turning on, the gate and cathode of the photothyristor SCR are short-circuited, and the photothyristor SCR is turned off, cutting off the load R _L.

FIG. 4 shows an example circuit of an AC output type, in which a capacitor _C3 for holding current compensation is connected in parallel to a photothyristor SCR of an output circuit B.
Furthermore, this circuit differs from the circuit in Figure 2 in that the output end of the diode bridge DB is connected between both ends of the photothyristor SCR, and the input end of the diode bridge DB is connected to the output ends Oa and Ob.
An AC power supply AE is connected between Oa and Ob via a load R _L , and the driving power for the photothyristor SCR and phototransistor Ph is obtained via a diode bridge DB. The circuit input signal Vi, the charging current i of the capacitor _C1 , and the load current are shown, respectively.

As described above, in the present invention, when a signal is input, a charging current of the capacitor flows through the series circuit of the capacitor and the first light emitting element, so that the output circuit is optically coupled by the instantaneous light emission of the first light emitting element. As a result, the driving power of the input circuit is extremely small. Therefore, it is very effective when using a power supply, dry batteries, or storage batteries, and has the effect that it can be used for a long time with batteries. play.

Furthermore, the output circuit can be easily modified from a DC output type to an AC output type by simply adding a diode bridge and a capacitor for compensating the holding current of the photothyristor, making it possible to easily develop both orthogonal output types. play.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of a conventional example, Fig. 2 is a circuit diagram of an embodiment of the present invention, Figs. 3 a to c are time charts for explaining the operation of the same, and Fig. 4 is another embodiment of the present invention. The example circuit diagram, Figures 5 a to 5 c, are time charts for explaining the operation of the above, where A is the input circuit, B is the output circuit, LED ₁ and LED ₂ are light emitting elements, Ph is a phototransistor, and C ₁ is a Capacitor, SCR is photothyristor, _C3 is holding current compensation capacitor, DB
is a diode bridge, DE is a DC power supply, AE is an AC power supply, R _L is a load, and Tr ₁ is a transistor.

Claims (1)

[Claims] 1. When a signal is input, a charging current of the capacitor is caused to flow through a series circuit of the capacitor and the first light emitting element,
an input circuit that causes a current of discharge from the capacitor to flow through a closed circuit of a transistor, a second light emitting element, and a capacitor that are turned on by the current of discharge when a signal is cut off;
It consists of a photothyristor optically coupled to the first light emitting element and a phototransistor optically coupled to the second light emitting element and connected between the gate and cathode of the photothyristor, and when the photothyristor is turned on, the load is connected to the power supply. and an output circuit that disconnects the load from the power supply when turned off. 2. The solid state relay according to claim 1, characterized in that the load is connected to a DC power source via a photothyristor. 3. A holding current compensation capacitor is connected between both ends of the photothyristor, the output end of a diode bridge is connected, and an AC power source is connected between the input ends of the diode bridge via a load. A solid state relay according to claim 1.