JP2658195B2 - Solid state relay - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Application> The present invention relates to a motor for industrial equipment and general consumer equipment,
The present invention relates to a solid state relay (SSR) used when controlling power supply to a load such as a heater.

<Prior art and its problems> In some cases, it is necessary to apply a solid-state relay to control two loads to be in an opposite state, such as turning on one of the loads and turning off the other. For example,
This corresponds to the case where the motor is driven by switching between forward rotation and reverse rotation. In order to respond to such demands, conventionally, it has been attempted to combine a normally-on operation type and a normally-off operation type to facilitate operation switching control and to simplify a circuit configuration. I have.
Conventionally, a normally-on operation type solid state relay used for this purpose has a configuration shown in FIG.

In the figure, 2 ₀ input circuit to which a signal on-off operation control is entered, 4 ₀ in response to an input signal load power supply
An output-side circuit for turning on and off the AC, both circuits 2 _0, 4 ₀ are coupled via the photocoupler 6 _0. The input-side circuit 2 ₀
Consists emitting diode PD constituting a pair of input terminals I _1, I ₂ and the photocoupler 6 ₀ signal on-off operation control is input, a DC power source E to the input terminal I _1, I ₂ switch SW is connected. On the other hand, the output-side circuit 4 ₀ includes a THY (triac in this example) bidirectional switching element connected via a pair of output terminals P _1, P ₂ to the load power supply V,
Trigger circuit TC for turning on / off this triac THY
And a trigger circuit near the zero crossing point of the load power supply AC voltage
It includes a zero-cross detection circuit ZC ₀ to operate the TC, a photo-transistors T ₁ constituting the photocoupler 6 _0, and a snubber circuit SC for surge absorption. The zero-cross detection circuit ZC ₀ above is formed of switching transistor T ₂ and resistor R ₂ to R ₄ are connected to the photo transistor T _1,
The trigger circuit TC is set to a non-operating state when an input signal is applied. Note that RL is a load of a motor, a heater, and the like.

In the above configuration, when the switch SW is not the input signal is applied at off, the phototransistor T ₁ is off,
The switching transistor T ₂ also the base current is off state not flow. When the voltage of the load power supply AC is gradually dividing point voltage rises and the resistance R ₃ and R ₄ from 0V reaches the operating potential of the thyristor SCR trigger circuit TC, the thyristors S
CR turns on. Then, since the triac THY is triggered and turned on, the connection between the output terminals P ₁ and P ₂ is turned on,
Power is supplied to the load RL. On the other hand, when the input signal to the input side circuit 2 ₀ switch SW is turned on is applied, the phototransistor T ₁ is turned on, the voltage of the load power supply AC flows through the base current to the switching transistor T ₂ to the vicinity of 0V the switching transistor T ₂ is turned on. Thus, since the voltage applied to the gate of the thyristor SCR is equal to or less than the trigger voltage, the thyristor SCR is turned off, thus the triac THY also not triggered, the output terminal P _1, P ₂ between the load RL in the OFF state Is not energized.

However, by way of the above-mentioned conventional arrangement, since it was necessary to zero-cross detection circuit ZC ₀ and photo transistors T ₁ separately switching transistor T ₂ also provided, not only the circuit configuration becomes complicated, making it also cost increase Was.

<Object of the Invention> The present invention has been made in view of such circumstances, and in a normally-on operation type solid state relay, the circuit configuration is further simplified without impairing the function of a zero-cross detection circuit. The purpose is to do.

<Structure and Effect of the Invention> The present invention employs the following structure to achieve the above object.

That is, in the present invention, in the zero-cross detection circuit of the solid-state relay, there is provided a phototransistor with a base terminal coupled to a light emitting element provided in the input side circuit, and the base of this phototransistor is the base of the phototransistor. It is characterized in that it is connected via a diode to a connection point of a voltage dividing resistor for voltage setting.

According to the above configuration, since signal transmission and zero-cross detection can be shared by a single phototransistor, a conventional switching transistor can be omitted. Therefore, the circuit configuration can be simplified and the cost can be reduced.

Embodiment FIG. 1 is a circuit configuration diagram of a normally-on operation type solid state relay according to an embodiment of the present invention.

The solid state relay 1 of this embodiment has an input side circuit 2 to which an on / off operation control signal is input, and a load power supply AC (alternating current) which is turned on / off in response to an input signal to the input side circuit 2. And an output side circuit 4 that is turned off. Both circuits 2 and 4 are coupled via a photocoupler 6.

The input side circuit 2 includes a pair of input terminals I ₁ , I ₂ , a resistor R _0, and a light emitting element (a light emitting diode in this example) PD that constitutes the photocoupler 6 to which a signal for controlling on / off operation is input. The DC power supply E and the switch SW are connected to the input terminals I ₁ and I ₂ .

On the other hand, the output side circuit 4 includes a pair of output terminals connected to the load power supply AC.
A bidirectional switching element (in this example, a triac) THY connected via P ₁ and P ₂ and the triac THY
Circuit, a zero-crossing detection circuit ZC for detecting the zero-crossing point of the voltage of the load power supply AC and operating the triggering circuit TC, and a snubber circuit SC for surge absorption.

The above-mentioned zero-crossing detection circuit ZC has a phototransistor Tr with a base terminal coupled to the light emitting diode PD provided in the input side circuit 2, and the base of the phototransistor Tr is a voltage divider for setting a base voltage. Resistance R ₁ ,
It is connected to a first connection point f of R ₂ via diodes D ₁ and D ₂ . Further, the collector of the phototransistor Tr is connected to a second connection point g of the voltage dividing resistors R ₃ and R ₄ for setting the gate trigger voltage of the thyristor SCR described later. And
The photo-transistor Tr is off, so than the potential V ₁ of the first connection point f of the better potential V ₂ of the second connection point g decreases, the resistance R _1, R _2, R _3, The value of R ₄ is set. Trigger circuit TC is a thyristor SCR, consists bridge circuit DB and a resistor R ₆ for full-wave rectification, operating potential V ₀ thyristor SCR, the potential Va necessary for ON in a state in which the photo transistor Tr is not received It is set in advance so as to be smaller. The snubber circuit SC has a resistor R ₅
And a capacitor C ₁ Metropolitan. Note that RL is a load of a motor, a heater, and the like.

Next, the operation of the solid state relay having the above configuration will be described.
This will be described with reference to the timing chart shown in FIG. 2 and the waveform diagram of the load power supply shown in FIG.

(I) No input signal applied state (period indicated by reference symbol a in FIG. 2) In this state, the switch SW of the DC power supply E is off, and the light emitting diode PD of the input side circuit 2 is off. Therefore, as shown in FIG. 3, when the load power supply AC voltage gradually increases from 0V, than the potential V ₁ of the first connection point f reaches a potential Va necessary to turn on the photo transistor Tr First, the potential V ₂ of the second connection point g is set to the operating voltage V _{0 of the} thyristor SCR.
, The gate of the thyristor SCR turns on by the time the phototransistor Tr turns on, thereby turning on the triac THY. Therefore, the connection between the output terminals P ₁ and P ₂ is conducted, and the load RL is energized.

(Ii) State immediately after application of the input signal (period indicated by reference character b in FIG. 2) When the switch SW of the DC power supply E is turned on and the input signal is applied to the input side circuit 2, the light emitting diode PD emits light.
Accordingly, since the base current of the phototransistor Tr increases, the operating potential V ₀ which phototransistor Tr in the following thyristor SCR decreases relatively potential Vb necessary to turn on the photo transistor Tr is turned on . As a result, the potential V ₂ of the second connection point g becomes the operating potential V of the thyristor SCR.
₀ or less. However, the triac THY does not turn off immediately due to its characteristics, but keeps on until the holding current becomes equal to or less than the holding current. That is, the power supply to the load RL is performed until the load power supply AC voltage becomes close to 0 V. Only when the current becomes equal to or smaller than the holding current, the transistor is turned off.

(Iii) Input signal application continuation state (period indicated by reference symbol c in FIG. 2) In this state, a certain period of time has elapsed since the switch SW of the DC power supply E was turned on. Since the light from the light emitting diode PD is received, the potential Vb required to turn on the phototransistor Tr
Equal to or less than the operating potential V ₀ of the thyristor SCR is. Since the photo-transistor Tr potential of the second connection point g is below operating potential V ₀ thyristor SCR in the state of ON, the thyristor SCR can not be turned on, and therefore the triac THY is also in the OFF state. Therefore, the output terminals P ₁ and P ₂ are non-conductive, and no current is supplied to the load RL.

(Iv) State immediately after the input signal is turned off (period indicated by reference symbol d in FIG. 2) In this state, since the switch SW of the DC power supply E is off and no input signal is applied, the light emitting diode PD of the output side circuit 2 Turns off. Therefore, as shown in FIG. 3, the potential Va necessary for the photo transistor Tr is turned on, becomes larger than the potential V ₀ which required the thyristor SCR to operate, the voltage of the load power supply AC is photo When the potential is higher than the potential Va required to turn on the transistor Tr, the phototransistor Tr maintains the on state. Thus, the potential V ₂ of the second connection point g is as follows operating potential V ₀ thyristor SCR, thyristor SCR can not be turned on, the triac THY
Is also in the off state. Therefore, the output terminals P ₁ and P ₂ are non-conductive, and no current is supplied to the load RL. Then, in the next period indicated by reference symbol a in FIG.
When gradually increasing from 0V, the thyristor SCR is turned on before the phototransistor Tr is turned on, so that the triac THY is turned on.

[Brief description of the drawings]

1 to 3 show an embodiment of the present invention. FIG. 1 is a circuit configuration diagram of a normally-on operation type solid state relay. FIG. 2 is a timing chart of the solid state relay of FIG. FIG. 3 is an explanatory diagram showing the relationship between the operating potential of the phototransistor and the thyristor and the output waveform of the load power supply. FIG. 4 is a circuit configuration diagram of a conventional normally-on operation type solid state relay. 1 ... solid state relay, 2 ... input side circuit, 4 ... output side circuit, ZC ... zero cross detection circuit, Tr ... phototransistor, TC ... trigger circuit, THY ... triac.

Claims (1)

(57) [Claims] An input side circuit to which a signal for controlling on / off operation is input, and an output side circuit for turning on / off a load power supply in response to the input signal, wherein the output side circuit is A bidirectional switching element connected to the load power supply, a trigger circuit for turning on and off the switching element, and a zero cross detection circuit for detecting a zero cross point of the load power supply voltage and operating the trigger circuit. In the solid state relay including, the zero cross detection circuit has a phototransistor with a base terminal coupled to a light emitting element provided in the input side circuit, the base of the phototransistor is a base voltage setting of the phototransistor Solid state relay characterized in that it is connected via a diode to a connection point of a voltage dividing resistor.