JP2629842B2 - 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 use a solid state relay to control one of two loads to be on and the other to be off so as to be in a state in which the two loads are contradictory to each other. For example, this corresponds to a case where the motor is driven by switching between forward rotation and reverse rotation. In such a case, for example, a circuit shown in FIG. 3 is conventionally used. This circuit is equipped with two solid-state relays SSR1 and SSR2 of normal off operation type.
The input circuits of SSR1 and SSR2 are connected to the control circuit shown in FIG.
The output side circuits are connected to the motors M as shown in FIG. 3b. Further, on the control circuit side, interlock relay circuits X1, X2 and time lag circuits T1, T2 are provided corresponding to the solid state relays SSR1, SSR2 individually. One solid state relay, for example, SSR1 is used for normal rotation, and the other solid state relay SSR2 is used for reverse rotation. In FIG. 3A, the symbol TH is a thermal relay that stops the control circuit when an overload or phase loss of the motor M is detected, PB1 and PB2 are push button switches for normal rotation and reverse rotation, and PB3 is This is a push button switch for stopping the motor. Also, in the same figure, a white mark of each contact indicates a normally open contact, and a black mark indicates a normally closed contact. In the above configuration, for example, when the motor M is driven forward, when the forward push button switch PB1 is pressed, the thermal relay TH → stop push button switch PB3 → forward push button switch PB1 → normally closed contact X2 → Interlock relay circuit X1 coil Current flows in sequence, the normally open contact X1 of the relay is turned on, and the normally closed contact X1 is turned off. Is started. And a predetermined time has passed and the timer When the time is up, the normally open contact T1 of the time lag circuit is turned on, power is supplied to the solid state relay SSR1 for normal rotation, the relay is turned on, and the motor M is rotated forward.

On the other hand, when the motor M is rotated in the reverse direction, when the reverse rotation push button switch PB2 is pressed, the thermal relay TH → the stop button switch PB3 → the reverse rotation push button switch PB2 →
Normally closed contact X1 → coil of interlock relay circuit X2 The normally open contact X2 of the relay is turned on and the normally closed contact X2 is turned off, so that the timer of the time lag circuit T2 Is started. And a predetermined time has passed and the timer When the time is up, its normally open contact T2 turns on,
Electric power is supplied to the solid state relay SSR2 for reverse rotation, the relay is turned on, and the motor M is reversed.

In this circuit, the time lag circuits T1 and T2 and the interlock relay circuits X1 and X2 are provided for the following reason.

DC / AC type solid state relays are usually configured so that the AC voltage is turned on when the phase is “0” and the current is turned off when the current is “0” to reduce the effect of high frequency noise on many circuits. Can be Therefore, the return time of the solid state relay is at most a half cycle of the power supply frequency. Therefore, one solid state relay, for example, SSR1 is not turned off and the other solid state relay SS
When R2 turns on, the discharge current of the capacitor C flows to both output circuits of both relays, and as a result, both relays are destroyed. Therefore, each relay is switched with a certain time difference.

As described above, when switching between normal rotation and reverse rotation of the motor, conventionally, two solid state relays SSR1 and SS
R2 was required, and time lag circuits T1 and T2 and interlock relay circuits X1 and X2 had to be provided for each relay individually to prevent the destruction of each solid state relay SSR1 and SSR2. . This not only complicates the circuit configuration as a whole, but also increases the cost.

<Object of the Invention> The present invention has been made in view of such circumstances, and uses a relatively simple circuit configuration to control one of two loads to be on and the other to be off so as to be in an opposite state. It is another object of the present invention to be able to perform switching with a constant time difference.

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

That is, the solid state relay of the present invention has a single input side circuit to which an output side circuit switching signal is input,
For this input side circuit, a normally-off operation type output side circuit and a normally-on operation type output side circuit which operate in opposition to each other in response to the output side circuit switching signal are respectively shared by a pair of photocouplers. The input side circuit is connected to a reference voltage setting circuit that sets two different reference voltages, a time constant circuit that operates in response to the input of the output side circuit switching signal, and an output of the time constant circuit. A comparison circuit for individually outputting an output-side circuit drive signal having a time difference corresponding to a difference between the reference voltages set by the reference voltage setting circuit to each of the photocouplers.

According to the above configuration, the input side circuit is unified for the normally-off output side circuit and the normally-on input side circuit. In addition, a signal that causes one of the two output circuits to be turned on and the other to be turned off is output with a predetermined time difference from the comparison circuit provided in the input circuit, so that the two output circuits do not operate simultaneously. . Therefore, there is no need to separately provide a conventional time lag circuit, and the overall circuit configuration can be simplified. In addition, the operation switching always involves a certain time difference, so that the destruction of the relay can be reliably prevented.

<Example> FIG. 1A is a configuration diagram of an input side circuit of a solid state relay, FIG. 1B is a configuration diagram of a normally-off operation type output side circuit of the same relay, and FIG. 1C is a normal diagram of the same relay. FIG. 3 is a configuration diagram of an output circuit of an ON operation type.

The solid state relay of this embodiment has a single input-side circuit 1 to which an output-side circuit switching signal is input, and the input-side circuit 1 operates reciprocally in response to the output-side circuit switching signal. Normally-off operation type output side circuit 2
And a normally-on operation type output side circuit 4 are commonly connected via first and second photocouplers PHC1 and PHC2, respectively.

The input side circuit 1 includes a switch SW for generating an output side circuit switching signal, a DC power supply E, two different reference voltages V1,
A reference voltage setting circuit 6 that sets V2, a time constant circuit 8 that operates in response to the input of the output side circuit switching signal, and outputs of the time constant circuit 8 are set to the respective reference voltages V1 and V2 set by the reference voltage setting circuit 6. The output side circuit drive signal having a time difference corresponding to the difference between the two reference voltages is compared with the first and second photocouplers PHC1,
It mainly includes a comparison circuit 10 that individually outputs to each of the light emitting diodes PD1 and PD2 of the PHC2. In the case of this example, the reference voltage setting circuit 6 includes voltage dividing resistors R3, R4, R5, R8 and a Zener diode ZD2 for holding a reference voltage. The time constant circuit 8 includes a resistor R1 for determining a charging time constant,
It comprises a charge / discharge capacitor C1, a resistor R2 for determining a discharge time constant, a Zener diode ZD1 for holding a constant voltage, and a resistor R6 for limiting current. The comparison circuit 10 includes a first comparator COM1 and a second comparator COM2, and the first comparator CO
M1 has its positive input (+) connected to the time constant circuit 8, its negative input (-) connected to the middle point between the resistors R3 and R4 of the reference voltage setting circuit 6, and its output connected to the light emitting diode PD1. Have been. The second comparator COM2 has a positive input terminal (+) connected to the time constant circuit 8, a negative input terminal (-) connected to the middle point between the resistors R4 and R5 of the reference voltage setting circuit 6, and an output terminal emitting light. Each is connected to a diode PD2. D1 is a diode for preventing backflow, C2 is a capacitor for holding a reference voltage after power is turned off, R7 is a resistor for limiting discharge current, R9 and R1
0 is a current limiting resistor.

On the other hand, the normally-off operation type output circuit 2
Phototransistor PT1, which constitutes the light receiving portion of photocoupler PHC1, first zero-crossing detection circuit 12, first trigger circuit 1
4. The first triac THY1 and the first for inductive load countermeasures
A snubber circuit 16 is provided. In the case of the present example, the first zero-crossing detection circuit 12 includes a diode D2, resistors R11 to R14, a transistor TR, and capacitors C3 and C4. Also, the first
The trigger circuit 14 includes a thyristor SCR1, a bridge circuit DB1 for full-wave rectification, and a resistor R16. Further, the first snubber circuit 16 includes a resistor 15 and a capacitor C16. Note that P
1 is an output terminal for an AC load.

On the other hand, a normally-on operation type output circuit 4
Includes a phototransistor PT2, a second zero-cross detection circuit 18, a second trigger circuit 20, a second triac THY2, and a second snubber circuit 22 which constitute a light receiving section of the second photocoupler PHC2. In the case of this example, the second zero-cross detection circuit
18 is the phototransistor PT2, diode D3, resistor R17
~ R20 and capacitor C5. Also, the second trigger circuit 2
0 includes a thyristor SCR2, a bridge circuit DB2 for full-wave rectification, and a resistor R22. Further, the second snubber circuit 22
It comprises a resistor 21 and a capacitor C7. P2 is an output terminal for an AC load.

Next, the operation of the solid state relay having the above configuration will be described.
A case where the motor is used for switching between forward rotation and reverse rotation of the motor will be described with reference to a timing chart shown in FIG. In this example, the normally-off operation type output side circuit 2 is used for reverse rotation, and the normally-on operation type output side circuit 4 is used for normal rotation.

In the input side circuit 1, when the switch SW of the DC power supply E is off, the light emitting diodes PD1 and PD2 of the first and second photocouplers PHC1 and PHC2 are both off.

At this time, in the normally-off operation type output circuit 2, the phototransistor PT1 is off, so that the current from the load power supply connected to the motor (not shown)
Base of transistor TR through P1, each resistor R15, R11
It flows between the emitters, and as a result, the voltage between the collector and the emitter of the transistor TR becomes lower than the gate trigger voltage of the thyristor SCR1. Therefore, the thyristor SCR1 is turned off. In this state, since no signal is applied to the gate of the first try-up THY1, the first triac THY1 is also turned off,
The state between the output terminals P1 and P1 is turned off.

On the other hand, the normally-on operation type output side circuit 4
Indicates that the current from the load power supply connected to the motor (not shown) is supplied to the phototransistor PT2 even when the light emitting diode PD2 is in the light-off state.
7. The current flows between the base and the emitter via the diode D3 sequentially. For this reason, the collector /
The emitter-to-emitter voltage is lower than the gate trigger voltage of the thyristor SCR2, but since the gate of the thyristor SCR turns on faster than the phototransistor PT2 turns on,
The second triac THY2 turns on, and as a result, the output terminal P
2. The area between P2 is turned on. Therefore, the motor can rotate forward.

To reverse the motor from this state, the switch SW of the DC power supply E is turned on. Then, the current of the DC power supply E is supplied to the reference voltage setting circuit 6 as an output-side circuit switching signal, and the negative input terminals (-) of the first and second comparators COM1 and COM2 are divided by the voltage dividing resistors R3, R4 and R5. Are set to predetermined reference voltages V1 and V2 (where V1> V2). Further, since the capacitor C1 of the time constant circuit 8 is also charged by the DC power supply E, the voltage applied to the positive input portions (+) of the first and second comparators COM1 and COM2 gradually increases. in this case,
Since the reference voltage V2 of the second comparator COM2 is set lower than the reference voltage V1 of the first comparator COM1,
First, the voltage of the positive input portion (+) of the second comparator COM2 reaches the reference voltage V2 (time t ₁ ), and its output becomes low level, and the corresponding light emitting diode PD2 emits light. After a certain period of time has elapsed, the voltage of the positive input portion (+) of the first comparator COM2 is changed to the reference voltage V1.
(Time t ₂ ), and its output goes low,
The corresponding light emitting diode PD1 emits light.

Normal ON operation type output side circuit 4, the light emitting diode PD2 emits light at time t _1, the phototransistor PT2 is turned on corresponding thereto, current from an unillustrated load power supply, the output terminal P2, the resistor R21, It flows between the collector and the emitter of the phototransistor PT2 via R17 and R19 in order. For this reason, the collector-emitter voltage is
The voltage drops below the gate trigger voltage of SCR2, and the thyristor SCR2 is turned off. In this state, since no signal is applied to the gate of the second triac THY2, the output terminals P2 and P2 are turned off when the voltage V of the load power supply becomes zero.

On the other hand, the normally-off operation type output circuit 2
, When emitting the first light emitting diode PD1 time t _2, the phototransistor PT1 is turned on corresponding thereto. Then, the current from the load power supply (not shown) is output from the output terminal P1 and the resistor R1.
The current flows between the collector and the emitter of the phototransistor PT1 via 5, R11, and R12 in order. Because of this, the transistor
The base voltage of TR decreases, and the voltage V of the load power supply is turned off near 0. As a result, a voltage is applied to the gate of the thyristor SCR1, and the thyristor SCR1 is turned on. Then, a signal is applied to the gate of the first triac THY1, the first triac THY1 is turned on, and the state between the output terminals P1 and P1 is turned on. For this reason, the motor can be rotated in the reverse direction.

Next, when the motor is rotated forward from this state, the switch SW of the DC power supply E is turned off. Then, by the charging voltage of the capacitor C2 and the current limiting resistor R7, the first,
Each negative input terminal (-) of the second comparator COM1 and COM2
Is maintained at the reference voltages V1 and V2 (V1> V2) for a certain period of time, but since the capacitor C1 of the time constant circuit 8 starts discharging immediately, each positive electrode of the first and second comparators COM1 and COM2 The voltage applied to the positive input (+) gradually decreases. In this case, the reference voltage V1 of the first comparator COM1
From being set higher than the reference voltage V2 of the comparator COM2, previous to the voltage of the positive input of the first comparator COM1 (+) the reference voltage V1 or less and becomes (time t _3), is the output of the high level The light emitting diode PD1 turns off. After a lapse of a certain time, the voltage of the positive input portion (+) of the second comparator COM2 is changed to the reference voltage V2.
Then, at time t ₄ , the output goes high and the light emitting diode PD2 goes out.

Normal OFF operation type output side circuit 2, the light emitting diode PD1 is turned off at time t _3, which the phototransistor PT1 is turned off corresponds, as described above, the voltage V of a non-illustrated load power becomes 0 At this point, the output terminals P1 and P1 are turned off.

Moreover, normal ON operation type output side circuit 4, the light emitting diode PD2 is turned off at time t _4, the phototransistor PT2 is load supply voltage is turned off in the vicinity of 0, Write gate of the thyristor SCR is turned on , The triac THY2 is turned on, and as a result, the output terminals P2 and P2 are turned on. Therefore, the motor can rotate forward.

As described above, the outputs of the normally-off operation type output side circuit 2 and the normally-on operation type output side circuit 4 are always switched with a fixed time difference Δta, Δtb.

In this embodiment, the motor is used for normal rotation and reverse rotation. However, the present invention is widely applied to the case where one of the two loads needs to be controlled to be in an opposite state to ON and the other to OFF. Of course, the invention can be applied.

[Brief description of the drawings]

1 and 2 show an embodiment of a solid-state relay according to the present invention. FIG. 1a is a configuration diagram of an input side circuit of the relay, and FIG. 1b is a normally-off operation type output of the relay. FIG. 1c is a block diagram of a normally-on operation type output side circuit of the relay, and FIG. 2 is a timing chart of the solid state relay of FIG. FIG. 3 is a circuit diagram of a conventional solid state relay. 1 ... input side circuit, 2 ... normal off operation type output side circuit, 4 ... normal on operation type output side circuit, 6 ... reference voltage setting circuit, 8 ... time constant circuit, 10 ... comparison Circuit, PHC1, PHC2 ... Photocoupler.

Claims (1)

(57) [Claims] An output side circuit switching signal is input to a single input side circuit, and the input side circuit has a normal input circuit which operates reciprocally in response to the output side circuit switching signal.
An OFF operation type output side circuit and a normally ON operation type output side circuit are commonly connected via a pair of photocouplers, respectively, the input side circuit includes a reference voltage setting circuit for setting two different reference voltages, A time constant circuit that operates in response to the input of the output-side circuit switching signal, and compares the output of the time constant circuit with each reference voltage set by the reference voltage setting circuit to determine a difference between the two reference voltages. A comparison circuit for individually outputting an output-side circuit drive signal having a time difference to each of the photocouplers.