JP2000209081A - Phase control type solid state relay - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a phase control type solid state relay eliminating the need of a large-sized component such as a transformer though it is a phase control type, making two input terminals and two output terminals sufficient for external terminals and hardly receiving the influence of noise or the like from the outside. SOLUTION: A reference resistor R0 connected to a positive input terminal 1 and a Zener diode ZD0 connected to a negative input terminal 1' are serially connected and the both-terminal voltage of the Zener diode ZD0 is used for the operation power source of a trigger pulse generation circuit composed of a CR charging circuit and comparators CMP1 and 2. Also, a main thyristor TAC and a zero voltage detection circuit ZV are parallelly connected to output terminals 2, 2', the signals of the zero voltage detection circuit are electrically insulated in a photocoupler PC1 and transmitted to an input side circuit and the charging and discharging of the charging capacitor of the CR charging circuit are controlled. The charging/discharging voltage and a voltage generated at both terminals of the reference resistor are compared in the comparator of the trigger pulse generation circuit and trigger pulses are generated. The trigger pulses are electrically insulated in a photo thyristor coupler PC2 and transmitted to the gate of the main thyristor on an output side and the main thyristor is controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase control type solid state relay for controlling the power of a heater and the rotation of a motor used in industrial equipment and the like.

[0002]

2. Description of the Related Art When performing power control using a thyristor, there are an on / off control type and a phase control type. The on / off control type has a simple structure like a solid state relay. However, there is a problem that precise control such as rotation control of a motor cannot be performed.

On the other hand, in the conventional phase control type, as shown in the conventional example shown in FIG. 3, a transformer T connected to an AC power supply AC is used.
And a signal obtained from the full-wave rectifier circuit DB and the zero-voltage detection circuit ZV to charge and discharge the charging capacitor C of the CR charging circuit CR in synchronization with the cycle of the AC voltage to generate a saw-tooth wave. The main thyristor TAC is controlled by generating a trigger pulse by comparing the sawtooth wave with the control current signal Ii converted into a voltage signal by the input amplifier AMP1 by the comparator CMP2, thereby controlling the value of the control current input signal Ii. , And controls the power of a load L such as a heater.
Therefore, it is possible to control the AC power more precisely than the on / off control type. However, in order to supply the operating power of the zero voltage detection circuit ZV, the input amplifier AMP1, and the comparator CMP2 from the AC side. A transformer T is required, and the size of the device is increased. In addition to the input terminals 1, 1 'and the output terminals 2, 2', power supply terminals 3,
There was a problem that the configuration was complicated, for example, 3 ′ was required.

In order to solve such a problem,
The present applicant has previously proposed a phase control type solid state relay disclosed in Japanese Patent Application Laid-Open No. 7-245939. In the phase control type solid state relay disclosed in Japanese Patent Application Laid-Open No. Hei 7-245939, a Zener diode and a reference resistor are connected in series to an input terminal of an input circuit for inputting a control current signal. The generated Zener voltage is used as an operation power supply of the trigger pulse generation circuit, and the voltage generated across the reference resistor is used as a control command voltage. Although this point is similar to the present invention, since the Zener diode is connected to the positive input terminal, the connection point between the Zener diode and the reference resistor becomes a reference point in the operation of the circuit, and this point must be used as a temporary ground point. Did not get. Therefore, a control command voltage is generated in the reference resistor so as to have a negative polarity with respect to the temporary ground point. Therefore, the control command voltage is shifted to the positive side from the tentative ground point by a resistor and input to the comparator, and a trigger pulse is generated in comparison with the charging voltage of the CR charging circuit. This trigger pulse is electrically insulated by a photothyristor coupler, transmitted to the gate of the main thyristor of the output side circuit, and configured to control (turn on) the main thyristor.

However, since the ground point exists only on the circuit, as described above, the control operation becomes unstable when a radio wave source such as a mobile phone is brought close to the apparatus. It was easy.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of such a problem, and is a phase control type capable of precisely controlling AC power, without requiring large components such as a transformer. And two external terminals and two input terminals.
An object of the present invention is to provide a phase control type solid state relay which requires only a plurality of output terminals and which is not easily affected by external noise or the like and performs a stable control operation.

[0007]

According to the present invention, there is provided a phase control type solid state relay according to the present invention, comprising a reference resistor connected to a positive input terminal for inputting a control current signal, and a Zener connected to a negative input terminal. A diode is connected in series, the voltage across the Zener diode is used as an operating power supply for a trigger pulse generation circuit including a CR charging circuit and a comparator, and a main thyristor and a zero voltage detection circuit are connected in parallel to an output terminal. The signal of the zero voltage detection circuit is electrically insulated by a photocoupler and transmitted to the input side to control the charging and discharging of the charging capacitor of the CR charging circuit,
The charge / discharge voltage is compared with a voltage generated at both ends of the reference resistor by a comparator of a trigger pulse generating circuit to generate a trigger pulse, and the trigger pulse is electrically insulated by a photothyristor coupler, and a main thyristor on the output side is generated. The main thyristor is controlled by transmitting the signal to the gate of the main thyristor.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A specific embodiment of the present invention will be described below with reference to the circuit diagram shown in FIG. The phase control type solid state relay according to the present invention mainly includes an input side circuit mainly including a CR charging circuit CR and a trigger pulse generation circuit including comparators CMP1 and CMP2, and a thyristor TAC and a zero voltage detection circuit ZV. The input side circuit and the output side circuit are electrically insulated from each other.

Then, a reference resistor R0 is connected to the positive input terminal 1 of the input side circuit for inputting the control current signal Ii, and a Zener diode ZD0 is connected to the negative input terminal 1 '. ZD0 is connected in series. The control current signal Ii is industrially 4 to 2
Since 0 mA is frequently used, description will be made here assuming that control is performed in the same range. However, the present invention is not limited to the above-described control current range, and the present invention is also applicable to other control current ranges. Needless to say, there is.

The control current signal I is supplied to the positive and negative input terminals 1, 1 '.
When i is input, the current mainly flows through the reference resistor R0 to the Zener diode ZD0, and a constant voltage, that is, a Zener voltage is generated across the Zener diode ZD0. This zener voltage is used as an operation power supply of a trigger pulse generation circuit including a CR charging circuit CR and comparators CMP1 and CMP2. Therefore, all the power supplies of these input side circuits are connected in parallel with the Zener diode ZD. Here, the circuit portion connected to the negative input terminal 1 'is a reference point in the operation of the trigger pulse generation circuit and serves as the ground line GND.

The control current signal Ii is applied to the reference resistor R0.
, A voltage V0 of [Ii × R0] is generated. The voltage V0 generated at both ends of the reference resistor R0 is input to the comparator CMP2 as a control command voltage V0 'that determines that the phase control output has a phase angle corresponding to the control current signal Ii.

When the input of the control current signal Ii is 4 mA, which is the minimum, the current consumed as the power supply is controlled not to exceed 4 mA at the maximum by using a low power consumption element or the like. To increase the current, the operation is normalized by adding a capacitor to the power supply circuit.

On the other hand, a main thyristor TAC and a zero voltage detection circuit ZV are connected in parallel to the output terminals 2 and 2 'of the output side circuit, and a load L and an AC power supply AC are externally connected in series. The load L is not limited to various electric devices such as a heater used for an electric furnace, a dryer, and the like, a lamp for an illumination device and an infrared device, and a motor used for an electric machine.

When the control current signal Ii is input to the load L and a phase control operation is performed, a voltage having a phase control waveform as shown in FIG. 2A is applied. Also, the main thyristor T
As shown in FIG. 2B, a voltage is applied to the AC to compensate for the voltage at the portion where the load voltage is phase-controlled.

The zero-voltage detecting circuit ZV includes a photodiode PC1 (D) of a photocoupler composed of two photodiodes PC1 (D) and a phototransistor PC1 (Tr) connected in anti-parallel, and current limiting resistors R9 and R10.
And connected in parallel with the main thyristor TAC. Accordingly, a current waveform as shown in FIG. 2C is generated in the photodiode PC1 (D), and the output terminals 2, 2 'are generated.
Is near zero voltage (generally less than ten volts, but not strictly defined), generates a zero voltage signal that turns off the photodiode PC1 (D), and a trigger pulse generating circuit on the input side. The zero voltage signal is transmitted to

Photodiode PC1 of photocoupler
When a current flows or turns off in (D), the signal of the zero voltage detection circuit is transmitted by light coupling despite being electrically insulated, and the corresponding phototransistor PC1 (Tr) is turned off. , An on / off operation as shown in FIG.

When a positive or negative voltage is applied, the zero voltage detection circuit ZV detects the photodiode PC1
Since the photodiode PC1 (D) only needs to be turned off when (D) is turned on and the voltage is near zero voltage, it is obvious that the same operation can be performed by using the full-wave rectifier circuit. Example anti-parallel connected photodiode PC
The present invention is not limited to the 1 (D) circuit system.

The phototransistor PC1 (Tr) corresponding to the photodiode PC1 (D) is connected in series with the resistor R4, and is connected to the power supply and the ground GND. The connection point between the phototransistor PC1 (Tr) and the resistor R4 is input to the comparator CMP1 together with the comparison voltage obtained by dividing the power supply by the resistors R2 and R3.
The transistor Tr1 is turned on / off by the output of 1. In the on / off operation of the transistor Tr1, the input polarity of the comparator CMP1 is determined so as to have the opposite polarity to the on / off operation of the phototransistor PC1 (Tr), and the AC power supply voltage as shown in FIG. To obtain an on / off waveform synchronized with the cycle.

The transistor Tr1 is connected in parallel so as to reset (discharge) the charging capacitor C1 of the CR charging circuit CR, and controls charging and discharging of the CR charging circuit CR. That is, the CR charging circuit CR includes a resistor R1,
R1 'and the charging capacitor C1 are connected in series. When the transistor Tr1 is on, the charging capacitor C1 is reset (discharged). When the transistor Tr1 is off, charging is performed through the resistors R1 and R1'. This charging / discharging operation has a sawtooth waveform as shown in FIG.

Here, since the reference resistor R0 is connected to the power supply by the Zener diode ZD0, the reference resistor R0
The control command voltage V0 generated at 0 is higher by the power supply voltage. Therefore, the Zener diode ZD1 and the resistor R
5 to the control command voltage V0 'by shifting to the ground GND side, and input to the comparator CMP2 which is the output part of the trigger pulse generation circuit together with the charging voltage of the charging capacitor C1 generated by the CR charging circuit CR. Compare and generate a trigger pulse.

FIG. 2F shows these control command voltages V
It also shows a pattern of comparison between 0 'and the charging voltage of the charging capacitor C1. FIG. 2G is a waveform showing the state of the trigger pulse output from the comparator CMP2 as a result of comparing the control command voltage V0 'with the charging voltage of the charging capacitor C1. When the voltage becomes lower than the control command voltage V0 ',
This indicates that a trigger pulse is generated.

In this manner, the trigger pulse generated from the trigger pulse generating circuit of the input side circuit is electrically insulated by the photothyristor coupler PC2, transmitted to the gate of the main thyristor TAC of the output side circuit, and transmitted to the main thyristor TAC. Is controlled (turned on).

The photothyristor coupler PC2 is similar to the photocoupler when a current flows through the photodiode.
The electrically insulated photothyristor is turned on by light coupling. The operation of the photo thyristor is a switching operation, like a general thyristor.
The operation is performed by an optical signal instead of an electric gate signal.

When the input control current signal Ii increases, the command voltage V0 further increases in the positive direction with respect to the power supply, so that the command voltage V0 'input to the comparator CMP2 also increases, and The pulse generation timing moves forward, and the conduction angle of the phase control increases. vice versa,
When the input control current input Ii decreases, the command voltage V0 decreases, the command voltage V0 ′ input to the comparator CMP2 also decreases, the timing of trigger pulse generation moves backward, and the conduction angle of phase control decreases. . Thus, the control output has a conduction angle corresponding to the input control current signal Ii, and it is possible to perform necessary phase control.

The basic elements that determine these input / output characteristics are determined by the time constant of the CR charging circuit CR, the value of the reference resistor R0, and the operating voltage of the Zener diode ZD0. , For example, 4 mA
, The conduction angle is 0 °, 12 mA is 90 °, 20
The conduction angle can be determined as 180 ° in the case of mA.

In the circuit diagram, the main thyristor TAC
The circuit GR composed of a resistor and a capacitor connected between the gate G and the output terminal 2 'is for preventing malfunction.

[0027]

According to the solid state relay of the present invention, the ground line GND connected to the negative input terminal 1 'serves as a reference point for the operation of the trigger pulse generating circuit. Thus, it is possible to realize a highly reliable device that does not easily malfunction even when a radio wave noise source due to such factors is nearby.

The element which determines the input / output characteristics is CR
It is determined by the time constant of the charging circuit, the value of the reference resistor, and the Zener diode voltage. All of these can be composed of parts with small inherent differences, so that it is a highly reliable device without quality variation. I can do it.

Moreover, the operating power supply is extracted from the control current signal on the input side, and the signal transfer between the input and output is electrically insulated by the photocoupler and the photothyristor coupler. Since insulation is provided and no transformer is required, the size of the device can be reduced.

In addition, despite the phase control system capable of precise AC power control, the main thyristor and the zero voltage detection circuit are connected in parallel and connected to the output terminal.
It is possible to provide a phase control type solid state relay having a simple configuration requiring only two input terminals and two output terminals, and having the same shape as the on / off control type solid state relay.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

FIG. 2 is a waveform chart showing the operation of each part on the circuit of FIG.

FIG. 3 is a circuit diagram showing a conventional example.

[Description of sign]

 1, 1 ': input terminal 2, 2': output terminal Ii: control current signal V0, V0 ': control command voltage L: load AC: AC power supply TAC: main thyristor ZV: zero voltage detection circuit PC1: photo coupler CMP1: Comparator PC2: Photothyristor coupler CMP2: Comparator ZD: Zener diode CR: CR charging circuit R0: Reference resistance R1 to R10: Resistance

Claims (1)

[Claims] 1. A reference resistor connected to a positive input terminal for inputting a control current signal and a Zener diode connected to a negative input terminal are connected in series, and a voltage across the Zener diode is supplied from a CR charging circuit and a comparator. A main thyristor and a zero voltage detection circuit are connected in parallel to the output terminal, and the signal of the zero voltage detection circuit is electrically isolated by a photocoupler and transmitted to the input side. Controlling the charging and discharging of the charging capacitor of the CR charging circuit, and comparing the charging and discharging voltage with the voltage generated across the reference resistor by a comparator of the trigger pulse generating circuit to generate a trigger pulse. The thyristor coupler is electrically insulated and transmitted to the gate of the main thyristor on the output side to control the main thyristor. A phase control type solid state relay characterized by the following.