JPS6192160A - Control circuit of induction load - Google Patents

Abstract

PURPOSE:To reduce the entire circuit of a circuit and the leakage current and to improve noise resistance by providing a zero crossing circuit in a control circuit of a thyristor energized by an induction load, and connecting a capacitor in parallel with both ends of the thyristor. CONSTITUTION:In a circuit in which an induction load 11 and a thyristor 13 are connected in series with an AC power source 12, a capacitor 16 is connected in parallel with both ends of the thyristor 13. A zero crossing circuit 14 is provided in a control circuit for applying a gate pulse to the thyristor 13, and a turn ON or OFF signal is supplied to the gate of the thyristor 13 with the zero crossing voltage immediately after a control signal is input to control input terminals 15, 15'. Thus, since a rush current is not flowed to the thyristor 13, it can be protected, and since the capacity of the capacitor 16 can be reduced, the size can be reduced, and the leakage current can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an inductive load control circuit, and more particularly to an inductive load control circuit in which power is supplied to the inductive load by switching a thyristor.

[Background technology]

Generally, when controlling an inductive load using a thyristor, in order to ensure the on/off operation of the thyristor,
A snubber circuit (=1) is added in parallel with the 9 load.

FIG. 4 shows such a conventional control circuit.

This control circuit is configured to supply or cut off power to an inductive load 4 connected to an AC power source 3 using a thyristor (TRIAC) 2 connected to a control input terminal 1.1. A snubber circuit 7 consisting of a resistor 5 and a capacitor 6 is connected in parallel.

This snubber circuit 7 is operated by a transient induced voltage generated in the inductive load 4 due to switching of the thyristor 2.
This thyristor 2 acts to prevent destruction or excessive rise in induced voltage.

However, in order to prevent such destruction of the thyristor and suppress the induced voltage, the capacitance of the capacitor 6 should be increased.
It is necessary to have a large time constant, which causes a large current to flow through the resistor 5 and capacitor 6, resulting in a large circuit configuration.

In other words, it has not been possible to sufficiently protect the thyristor by downsizing the control circuit for light loads, reducing the N current flowing through the circuit, and increasing noise resistance.

[Purpose of the invention]

An object of the present invention is to miniaturize the entire circuit, reduce leakage current, and obtain sufficient noise resistance in a circuit in which an alternating current circuit is controlled on and off by a thyristor.

[Summary of the invention]

The present invention has a configuration in which a zero cross circuit is connected in the control circuit of a thyristor connected in series with an AC power source together with an inductive load, and a capacitor is connected in parallel to both ends of the thyristor, so that the voltage across the capacitor is zero.
By turning on the thyristor near the voltage, the inrush current from the capacitor to the thyristor is eliminated,
41JX protection can be achieved. Further, the capacitor and the inductive load constitute a high-frequency attenuation filter of the LC circuit to prevent malfunction of the thyristor due to high frequency noise from the power supply side. Furthermore, by reducing the capacitance of the capacitor and not using a resistive element, leakage current can be suppressed and the entire circuit can be made smaller.

[Embodiment 1] FIG. 1 is a circuit diagram showing an embodiment of an inductive load control circuit according to the present invention.

In this embodiment, an AC power supply 11 is used together with an inductive load 11.
In the control circuit of thyristor 13 connected in series to g12,
A zero cross circuit 14 is connected.

15.15° is a control input terminal. Further, a high-frequency attenuation filter capacitor 16, which constitutes an LC time constant circuit together with an inductive load, is connected in parallel between the AC side terminals at both ends of the thyristor 130.

Here, the zero-cross circuit 14 acts to cause a gate current to flow through the thyristor 13 at the zero-cross voltage immediately after the input signal is input, and on the other hand, to cut off the gate current of the thyristor 13 immediately after the input signal is cut off. .

Figure 2 shows a solenoid valve 1 in which the above-mentioned inductive load 11 is a solenoid.
7, this electromagnetic valve 17 consists of a main valve part 17a and a solenoid part 17b that drives this main valve part 17a, and an inductive load control circuit part 17e of the present invention is attached to this solenoid part 17b. This is an example of a solenoid valve.

Next, the operation of the above-mentioned inductive load control circuit will be described.

First, a control signal is input to the control input terminal 15, 15', causing a turn-on current to flow through the gate.

When the voltage across the capacitor 16 reaches around 0 port immediately after it is turned on, the thyristor 13 is turned on. Therefore, a predetermined electric power is supplied to the guide ill, which is energized to operate the solenoid valve 17 of the above embodiment.

On the other hand, when the control input signal is cut off, the thyristor 13 is turned off by the zero cross current immediately after this cutoff, and the induction member r
Current supply to t111 is stopped.

Therefore, in this control circuit, since the thyristor 13 is operated at zero cross voltage, the inrush current of the capacitor 16 does not flow to the thyristor 13, and the use of the resistor 5 used in the conventional snubber circuit can be omitted. Omitting this resistor 5 lowers the impedance for high frequencies when considering the surge voltage caused by high-speed switching in the several Mk band, since the impedance capacity of the capacitor 16 is proportional to the reciprocal of the frequency.
Malfunctions due to dv/dt of 3 can be reduced.

In addition, since the resistor 5 can be omitted and the capacitor 16 can be made smaller, the control circuit can be made smaller, current leakage to the capacitor 16 can be reduced, and the capacitor 16 can be made smaller.
Damage to the thyristor 13 due to high-frequency noise can be prevented by the high-frequency attenuation filter effect formed by the LC time constant of the inductive load 11 and the inductive load 11.

[Embodiment 2] FIG. 3 shows another embodiment of the present invention.
1 is a battery, 22 is a switch, 23 is an input current limiting resistor, and 24 is a light emitting diode of a photocoupler 25, which are connected in series as shown. Furthermore, a protection diode 26 for the light emitting diode 24 is connected in parallel to the light emitting diode 24 .

On the other hand, numeral 12 is an AC 2Itit source similar to that shown in FIG.

Further, the thyristor 13 is connected in parallel to the capacitor 16 through a parallel circuit including a display light emitting diode 27 and a backflow path diode 28. 29 is a varistor connected in series to the AC power source 12 for blocking high voltage noise.

14A is a zero cross circuit that supplies a turn-on current to the gate of the thyristor 13, and a photocoupler 25 is installed in this circuit.
A phototransistor 30 is connected thereto. Note that the zero cross circuit 14A uses the voltage across the thyristor 13 as a power source.

The function of this second embodiment is basically that of the first embodiment shown in FIG.
It is the same as in the case of , when switch 22 is closed, resistor 2
A current limited by 3 flows through the light emitting diode 24, which lights up. Therefore, the phototransistor 30 outputs a signal. The zero-crossing circuit 14A detects the zero-crossing voltage immediately after this output, and causes a gate current to flow through the thyristor 13.

This gate current turns on the thyristor 13,
The light emitting diode 27 lights up, and the inductive load 11 is driven by the alternating current flowing through the parallel circuit of the light emitting diode 27 and the diode 28 .

Subsequently, when the switch 22 is opened, the light emitting diode 24 is turned off and the output of the phototransistor 30 is also stopped. Zero cross circuit 14A is immediately after thyristor 1
3, the thyristor 13 is turned off, the light emitting diode 27 is turned off, and the driving of the inductive load 11 is also stopped.

In the second embodiment, a DC input circuit and an AC load circuit are optically related, and if necessary, instead of the above method of inputting a control signal using the switch 22, a light emitting diode 24 and a phototransistor may be used. It is also possible to adopt a method in which a control shaft is moved in and out between the control shaft 30 and the control shaft 30.

〔effect〕

According to the present invention, by connecting a zero cross circuit in the control circuit of the thyristor and turning on the thyristor when the terminal voltage of the capacitor connected to the inductive load becomes 0 volts, inrush current from the capacitor to the thyristor is generated. In addition to eliminating the supply of thyristors, it is possible to protect the thyristor, eliminate the need to connect a resistor in the LC circuit, and configure the high-frequency attenuation filter of the LC circuit, thereby reducing the capacitance of the capacitor. In this way, various effects can be obtained, such as improved resistance to noise mixed into the power supply, miniaturization of the overall circuit configuration, and reduction in leakage current to the capacitor.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing one embodiment of an inductive load control circuit according to the present invention, FIG. 2 is a schematic diagram of an example of a solenoid valve to which the present invention is applied, and FIG. 3 is a circuit diagram showing another embodiment of the present invention. The circuit diagram shown in FIG. 4 is a circuit diagram of a conventional example. 11... Inductive load, 12... AC power supply, 13...
Thyristor, 14.14A...Zero cross circuit, 15
．． 1-5°...Control input terminal, 16...Capacitor, 21...Buffer battery, 22...Switch, 24...
...Light emitting diode, 27...Light emitting diode, 28
...Diode, 29...Varistor, 30...Phototransistor.

Claims (1)

[Claims] In the control circuit of the thyristor connected in series with an AC power supply together with an inductive load, a zero-cross circuit is connected to supply or cut off the gate current to the thyristor at the zero-cross voltage immediately after supplying or cutting off the control input, and a zero-cross circuit is connected to both ends of the thyristor. is an inductive load control circuit characterized by connecting a capacitor.