JPH0451710A - Contactless relay - Google Patents

Abstract

PURPOSE:To attain normal switching control even to a load such as an inductive load in which a phase difference is caused between a load voltage and a load current by providing a trigger signal circuit from which a trigger signal is continuously fed to a thyristor after the said thyristor is energized. CONSTITUTION:When a thyristor TY is energized, a capacitor C2 is charged up to a voltage depending on a Zener diode ZD. The charge charged in the capacitor C2 is discharged through the path of a diode D1-a photo transistor(TR) PT-a resistor R9-a resistor R4 for a period when a triac TR is energized and the thyristor TY is not energized to supply continuously a trigger signal to the thyristor TY. As soon as the triac TR is turned off when a load current passes its zero point after the triac TR is energized, the thyristor TY receiving a full wave rectified voltage +V is energized independently of ON/OFF of the transistor TR thereby allowing the triac TR to be triggered again.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a non-contact relay that controls opening and closing of a load near zero volts of power supply voltage.

[Conventional technology]

A conventional device of this type of non-contact relay is shown in FIG.

In Figure 2, TI, ? 2 is a control terminal to which a DC control input signal is applied, and a current limiting resistor RO and a light emitting diode PD of a photocoupler PC are connected in series to the control terminals TI and T2. T3. T4 is an output terminal to which the load and AC power source E are connected, and this output terminal T3. T4 is a semiconductor switching element that switches the load current, in this case a tria-shift T.
R is connected and the diode bridge rectifier circuit DB
AC input terminal is connected.

A resistor R6 and a capacitor C1 connected in parallel to the triac TR protect the triac TR from surge voltage, and the resistor R5 is a gate resistance of the triac TR. A voltage dividing circuit consisting of a thyristor TV and resistors R1 and R2 is connected to a DC output terminal of the diode bridge rectifier circuit DB, and a base of a transistor Tr is connected to a connection point between the resistors R1 and R2. A resistor R3 is connected to the collector of the transistor T, and the connection point between this resistor R3 and the collector of the transistor T is a photocoupler PC.
is connected to the gate of the thyristor TV via the phototransistor PT. R4 is the gate resistance of the thyristor TV. The resistors R1 to l'13 and the transistor T
r constitutes a pulse generation circuit.

The operation of the non-contact relay shown in FIG. 2 will be explained using the waveform diagram shown in FIG. 3. In Figure 3, e is AC type fg
, E voltage waveform, +V is diode bridge rectifier circuit D
B is the full-wave rectified voltage waveform, Vi is the control input signal waveform, v8
is the load voltage waveform.

In Fig. 2, when the control input signal voltage Vi is not applied to the control terminals TI and T2, the photocoupler PC is in an off state and the gate signal of the thyristor TV is cut off, so the thyristor TV is in a non-conducting state. As a result, the triac TR does not become conductive due to the current flowing through the gate resistor R5, and therefore the load is in an OFF state. When the control input signal voltage Vi is applied to the terminals Tl and T2 as shown in FIG. 3, the photocoupler PC is turned on. At this time, the transistor Tr is conductive because the full-wave rectified voltage +V of the diode bridge rectifier circuit circle is applied, so the gate signal of the thyristor TV is short-circuited by the transistor T.The full-wave rectified voltage (ν When becomes near zero volts and reaches the zero cross voltage determined by resistors R1 to R3, the transistor ↑r
is turned off, and as a result, a pulsed firing pulse is applied to the thyristor TV, thereby making the thyristor TV conductive.

When the thyristor TV becomes conductive, a gate signal of the triac P is generated in the gate resistor R5 of the triac TH, and the triac TR becomes conductive, whereby the load is applied at around zero volts of the power supply voltage.

When the load current flowing through the triac TR becomes zero after the load is applied, the triac TR turns off, but at this time, a pulse-like firing signal is applied to the thyristor ↑Y, so the thyristor TV conducts and the triac TR turns off again. Conducts and current continues to flow through the load. Control terminal T
1. When the control input signal voltage is no longer applied to T2, the photocoupler PC turns off, cutting off the firing signal of the thyristor T'/, and the triac TR turns off when the load current turns off, cutting off the load. do.

(ii!J to be solved by the invention) In the conventional device described above, when a resistive load is used as the load, the load can be normally controlled to open and close, but when an MH load is used as the load, Since a phase difference occurs between the load voltage and the load current due to the power factor relationship, it may become impossible to normally control the opening and closing of the load. To explain this using the waveform diagram shown in Fig. 4, as shown in Fig. 4 (^), the load voltage e and the load ti current i
If there is a phase difference with L, the triac TR must be turned off at the point where the load current is zero (time indicated by TO) and then immediately re-ignited. However, when the triac TR is turned off, the t source voltage E is in a high voltage phase, and the full-wave rectified voltage +V of the diode bridge rectifier circuit DB exceeds the zero cross voltage as shown in Figure 4 (B). If a pulsed firing signal is applied to the neck and the transistor Tr is turned on before the thyristor ↑Y becomes conductive, the firing signal will no longer be applied to the thyristor TV. For this reason, the triac TR has a load current iL
turns off at the zero point and is not immediately re-ignited, causing the voltage E
decreases, the full-wave rectified voltage +V drops below the zero-crossing voltage, and the thyristor TV becomes conductive before being re-ignited, so that the triac Tl? However, as shown in FIG. 4(C), the disadvantage is that phase loss occurs within a half cycle.

To solve this problem, when the full-wave rectified voltage of 10 V is applied in excess of the zero-cross voltage, the thyristor TV is activated via the phototransistor PT of the photocoupler PC. Although it is conceivable to select circuit elements so that the thyristor TV turns on quickly, this has the disadvantage that it is difficult to select elements that have the same characteristics with respect to the ambient temperature.

SUMMARY OF THE INVENTION Therefore, the purpose of the present invention is to eliminate the drawbacks of the conventional device described above, and to provide a simple structure that can normally control opening and closing even for loads where a phase difference occurs between the load voltage and the load current, such as an inductive load. Our goal is to provide contact relays.

[Means to solve the problem]

In order to achieve the above-mentioned object, the present invention provides an electric... A pulse generation circuit generates an ignition pulse near zero volts of the IIA voltage, a thyristor conducts by an AND signal of a pulse signal from this pulse generation circuit and a control input signal, and a gate signal is applied by the conduction of this thyristor. The non-contact relay is provided with a semiconductor switching element for driving a load, further comprising a firing signal circuit that continuously supplies a firing signal to the thyristor after the thyristor becomes conductive.

[For production]

In the non-contact relay of the present invention, once the thyristor is turned on to supply a gate signal to the semiconductor switching element that switches on and off the load current, the ignition signal is continuously supplied to the thyristor from the ignition signal circuit. As a result, the semiconductor switching element is turned off when the load current passes through the zero point of every half wave, and then the thyristor becomes conductive, so that the semiconductor switching element is immediately re-ignited.

[Example] Next, an example of the present invention will be described in detail based on the drawings. FIG. 1 is a circuit diagram of a non-contact relay showing an embodiment of the present invention. In the figure, the same components as those in the conventional device shown in FIG.

The differences in Fig. 1 from the conventional device shown in Fig. 2 are as follows.
Thyristor? A resistor R8 is connected in series with '/, a Zener diode ZD is connected in parallel with this resistor R8, and a diode 2 and a capacitor C2 are connected.
A resistor R7 is connected between the connection point between the resistor R7 and the collector of the transistor Tr and the phototransistor PT of the photocoupler PC, and the connection point between the resistor R7 and the phototransistor PT and the connection point between the diode D2 and the capacitor C2. This is the point where a diode Di is connected between them. The capacitor C2, diodes Di, D2, resistor R8, and Zener diode ZD form a firing signal circuit for the thyristor TY. Note that R9 is a discharge resistance of the capacitor C2.

Next, the operation of the embodiment of the present invention will be explained.

When the control input signal voltage Vi is not applied to the control terminal T1.72, the photocoupler PC is in an off state, and the thyristor TV and the liac Tll are also non-conductive. Control terminal TI,? When the control input signal voltage Vi is applied to 2, the photocoupler PC is turned on, and when the full-wave rectified voltage +V of the diode bridge rectifier circuit OB becomes less than the zero cross voltage, the transistor Tr is turned off and the thyristor ↑V is pulsed. An ignition signal is supplied, whereby a gate signal is applied to the triac TR, the tritic TR becomes conductive, and a load current flows. When the thyristor TV becomes conductive, the capacitor C2 is charged to a voltage determined by the Zener diode ZD. The charge stored in the capacitor C2 is transferred to the diode D during the period when the tritic TR is conductive and the thyristor TV is non-conductive.
It is discharging via 1-phototransistor PT-resistance R9-resistance R4, and continues to apply an ignition signal to thyristor TV. Therefore, after the triac TR conducts, when the load current passes through the zero point, the triac TR turns off and at the same time, the full-wave rectified voltage +V is applied to the thyristor ↑Y, which conducts regardless of whether the transistor Tr is on or off. Book TR is re-ignited. Control terminal ↑1. ? When the control input signal voltage Vi applied to the terminal 2 disappears, the photocoupler PC turns off, cutting off the path of the ignition signal circuit of the thyristor l, and the triac TR turns off when the load current passes through the zero point, reducing the load current. Cut off.

In the above-mentioned embodiment, a thyristor firing signal circuit using a capacitor has been described, but the present invention basically only needs to continuously supply a firing signal to a thyristor after the thyristor becomes conductive. This is not limited to examples.

〔Effect of the invention〕

As described above, according to the present invention, a pulse generation circuit that generates an ignition pulse near zero volts of the power supply voltage, a thyristor that is made conductive by an AND signal of a pulse signal from the pulse generation circuit and a control input signal, In a non-contact relay equipped with a semiconductor switching element that drives a load by applying a gate signal through conduction of this thyristor,
By providing a firing signal circuit that continuously supplies a firing signal to the thyristor after the thyristor becomes conductive,
Even when a load that causes a phase difference between the load voltage and load iii is used as an inductive load, the load can be normally controlled to open and close, and there is no need to limit the type of load used. It has this effect.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of a non-contact relay showing an embodiment of the present invention, Fig. 2 is a circuit diagram of a non-contact relay showing a conventional device, and Fig. 3 is a circuit diagram of a non-contact relay showing an embodiment of the present invention.
4 and 4 are waveform diagrams showing the operation of the circuit diagram shown in FIG. 2, respectively. TY: Thyristor, TR: Semiconductor switching element (TRIAC) T: Transistor, PC: Photo Fig. 112

Claims (1)

[Claims] 1) A pulse generation circuit that generates an ignition pulse near zero volts of a power supply voltage, a thyristor that is rendered conductive by an AND signal of a pulse signal from this pulse generation circuit and a control input signal, and this thyristor. A non-contact relay comprising a semiconductor switching element to which a gate signal is applied to drive a load upon conduction of the thyristor, further comprising a firing signal circuit that continuously supplies a firing signal to the thyristor after the thyristor is conductive. A non-contact relay characterized by: 2) The non-contact relay according to claim 1, wherein the firing signal circuit includes a capacitor that is charged to a predetermined voltage by conduction of the thyristor, and the discharge current of this capacitor is used as the firing signal of the thyristor. Non-contact relay.