JPH02177721A - Ac 2-wire type contactless switch - Google Patents

Abstract

PURPOSE:To prevent the increase in a leaked current when the operating voltage is increased by using a voltage of a constant voltage circuit so as to energize a sensor circuit when the sensor circuit does not detect a phenomenon and using the charge of a capacitor so as to energize a sensor circuit when the sensor circuit detects the phenomenon. CONSTITUTION:When the sensor circuit 10 does not detect the phenomenon, a voltage is applied to a base of a transistor(TR) 16 and a constant voltage circuit 8 and both TRs 5, 16 are turned on, Then the sensor circuit 10 is energized and a capacitor 12 is charged up. When the sensor circuit 10 detects the phenomenon, since the detection signal goes to a low level, the TR 16 is turned off and a thyristor 19 is turned on. Although the voltage of both the polarities of the power supply is nearly decreased to zero, the detection is continued while the sensor circuit 10 consumes the charge in the capacitor 12. Thus, although a main thyristor 4 turned on is once turned off at each zero point of the current with respect to the power frequency, they do not given effect on the circuit operation.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides an AC two-wire non-contact point that opens and closes a series circuit between an AC power source and a load using a sensor circuit such as a proximity switch driven by the AC power source. Regarding switches.

[Conventional technology]

When controlling a switching element such as a thyristor using a detection signal from a sensor circuit to open or close a series circuit between an externally connected AC power source and a load, the power source that drives the sensor circuit is not an independent power source, and the AC power source By simply connecting its output terminal across a series circuit between a general commercial power source and the load, the power to the load can be switched and controlled. A conventional example of such an AC two-wire non-contact switch is shown in FIG. At E in FIG. 2, the AC power supply 1 and the load 2 are connected in series, with terminals TI and TI connected at both ends.
Connected between T2. Both terminals TI.

The AC input end of the single-phase bridge rectifier circuit 3 is connected between 12 and the main thyristor 4 is connected to the DC output end (hereinafter referred to as the power output end). The series circuit of the AC power source 1 and the load 2 is opened and closed via the AC power source 1 and the load 2.

A series type constant voltage circuit 8 consisting of a transistor 5, a Zener diode 6, and a resistor 7 and a detection transistor 11 are connected in parallel with the main thyristor 4. Further, a parallel circuit of a sensor circuit 10 and a capacitor 12 is connected via a constant voltage circuit 8 and a diode 9. The constant voltage circuit 8 sets the Zener voltage of the Zener diode 6 as vzl, the voltage drop between the pace emitter of the transistor 5 as VBg1, and the collector voltage when a saturation current flows through the transistor 11.
If the voltage drop between emitters is VcΣ, then Vzl + Vc
A constant voltage of x-VBI+ is applied to the sensor circuit 10 via the diode 9. Further, when the sensor circuit 10 detects a target phenomenon, it changes the signal that had been at a high level to a low level, turns off the transistor 11, and disables the constant voltage function of the constant voltage circuit 8.

A gate circuit 15 consisting of a series circuit of a Zener diode 13 and a resistor 14 is connected to the connection point between the transistor 5 and the diode 9 and to one output terminal of the rectifier circuit 3, and the connection point between the Zener diode 13 and the resistor 14 is connected to the gate of the thyristor 4. It is connected. Zener voltage VZ2 of Zener diode 13
If the voltage between the gate and cathode of thyristor 4 is VGx, then VZ2 + Vox) Vzs +Vcz -Vn
g, and when the constant voltage function of the constant voltage circuit 8 is operating, the Zener diode 13 is not conductive and the gate current of the thyristor 4 does not flow, so the thyristor 4 is off.

Next, when the sensor circuit 10 detects a predetermined phenomenon, this detection signal changes to low level, and the transistor 11 turns off, so the function of the constant voltage circuit 8 is disabled, and the current flowing through the resistor 7 is transferred to the base of the transistor 5. Since it becomes a current, the voltage V across the capacitor 12 increases. Therefore, current flows through the Zener diode 13 of the gate circuit 15 to the gate of the thyristor 4, turning on the main thyristor 4 and energizing the load 2. When the main thyristor 4 is turned on, the voltage across it becomes approximately □v, and from the power supply 1 to the sensor circuit 1
The current supply to 0 is cut off, and the sensor circuit 10 continues the detection operation while consuming the charge of the capacitor 12. The main thyristor 4 that has been turned on is once turned off every time the current of the power supply frequency reaches zero, but this has no effect. Since the capacitor 12 is discharging by flowing current through the sensor circuit 10, the voltage V across it finally becomes lower than the Zener voltage Vzz of the Zener diode 13, and the Zener diode 13 becomes non-conducting, and the main thyristor 4 is turned off. becomes the state of However, as the voltage across the main thyristor 4 rises, the transistor 5 turns on, charging the capacitor 12, and when the voltage V reaches the Zener voltage of the Zener diode 13, the main thyristor 4 turns on again. . Thus, while the detection signal of the sensor circuit 10 is at a low level, the switch is turned off for a short time near the zero point of AC full-wave rectification, but the effect of the entire switch remains on.

[Problem to be solved by the invention]

In this type of AC two-wire type non-contact switch, it is particularly important that the leakage current is small because if the leakage current flows to the load when the switch is off, it will have an adverse effect on the load.

By the way, the leakage current when the switch shown in FIG. 2 is off is the sum of the current I flowing through the sensor circuit 10 and the current I flowing through the Zener diode 6. The current Il becomes smaller by increasing the impedance 2 of the sensor circuit 10, and the current Il becomes smaller by changing the resistance value R of the resistor 7 by a large amount. There is a limit to how much can be increased, and there is a drawback that leakage current increases as the operating voltage increases. Recently, with the development of electronic technology, the voltage range in which products can be used has expanded, and there has been a demand for AC two-wire type non-contact switches with even smaller leakage currents.

An object of the present invention is to provide an AC two-wire type non-contact switch that prevents an increase in leakage current when the operating voltage is increased.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides a rectifier circuit in which a series circuit of an AC power source and a load is connected between both input terminals, and a series circuit between both output terminals of this rectifier circuit. A main thyristor that is connected and has a gate circuit, a sensor circuit that detects a predetermined phenomenon and sends out a detection signal, a capacitor that is connected in parallel with this sensor circuit, and a capacitor that is connected between both output terminals of the rectifier circuit. The device includes a constant voltage circuit, and a transistor that switches the voltage of the constant voltage circuit and supplies power to the sensor circuit and the gate circuit according to a detection signal from the sensor circuit.

[Effect]

In order to achieve the above-mentioned object, when this AC two-wire type non-contact switch is off, that is, when a predetermined phenomenon is not detected, the leakage current at the terminals of the power supply is reduced. To achieve this, it is best to reduce the number of parts connected to the α source end as much as possible, or to connect parts with a small current.

Therefore, in the present invention, when the sensor circuit does not detect a phenomenon, only a constant voltage circuit is connected to the upper end of the power supply in addition to the sensor circuit, and the voltage of this constant voltage circuit is used to supply power to the sensor circuit, and when the sensor circuit detects a phenomenon, is switched to a gate circuit using a transistor, and power is supplied to the sensor circuit using the capacitor's charge.

〔Example〕

Embodiments of the present invention will be described below with reference to FIG. Here, parts and circuits that have the same role as in FIG. 2 are given the same reference numerals as in FIG. 2. At 8 in FIG. 1, an AC power source 1 and a load 2 are connected in series as before, and terminals T1.
It is connected between Tz.

An AC terminal of a single-phase bridge rectifier circuit 3 is connected between these terminals Tx and Tz. The main thyristor 4 is connected to the upper end of the power supply, and is equipped with a sensor circuit 101, a capacitor 12, a gate circuit 15, etc. as in the conventional one, but the constant voltage circuit 8 is powered by a series circuit of a Zener diode 6 and a resistor 7. This connection point is connected to the base of the transistor 5. The transistor 16 is connected to supply power to the sensor circuit 10 via its collector and emitter to charge the capacitor 12.

The base of this transistor 16 is connected to a connection point of a series circuit between a resistor 17 connected to the upper end of the power supply and the output end of the sensor circuit 10, and is turned off by a low level detection signal from the sensor circuit 10. The gate circuit 15 of the main thyristor 4 is
It consists of a thyristor 19, a Zener diode 13, a resistor 14, and a capacitor 20 connected in parallel with the resistor 14, and is connected to the upper end of the power supply, and one end of the capacitor 20 is connected to the gate of the main thyristor 4. Furthermore, thyristor 19
The gate of is connected to the connection point between both transistors 5 and 16, and the connection point between thyristor 19 and Zener diode 13 is connected to one end of capacitor 12. Note that when the amplification factor of the transistor 5 of the constant voltage circuit 8 is high, a resistor 21 as shown by a broken line may be connected in series to the collector of the transistor 5.

When the sensor circuit 10 does not detect a phenomenon, the signal is at a high level and the king thyristor 4 naturally does not turn on, so a voltage is applied to the constant voltage circuit 8 and the base of the transistor 16, turning on both transistors 5 and 16. When power is supplied to the sensor circuit 1o, the capacitor 12 is simultaneously charged. At this time, since the voltage across the sensor circuit 10 is set lower than the Zener voltage of the Zener diode 13, the Zener diode 13 is not conductive and the main thyristor 4 is off. When the sensor circuit 10 detects a phenomenon, the detection signal changes to low level, so the transistor 16 is turned off.
Thyristor 19 turns on. At this time, since the Zener diode 13 becomes conductive, the main thyristor 4 is turned on, and current flows through the load 2. At this time, the voltage at the upper end of the power supply drops to approximately O, but the sensor circuit 10 continues the detection operation while consuming the charge of the capacitor 12, and the main thyristor 4, which has been turned on, is turned off once at each zero point of the current at the power supply frequency. has no effect.

If the amplification factor of the transistor 5 constituting the constant voltage circuit is high, if a series lζ resistor 21 is connected to the collector of the transistor 5, a steep charging current will flow through the capacitor 12I when the external power supply 1 is applied. external load 2
can be prevented from malfunctioning.

〔Effect of the invention〕

According to the present invention, when this AC two-wire type non-contact switch is off, leakage current occurs only from the Zener diode of the constant voltage circuit connected to the upper end of the power supply, and the impedance of the sensor circuit is increased as much as possible. If the voltage is high, this current will not increase. Furthermore, the base current of the transistor connected in parallel between the gate and cathode of the thyristor flows through the emitter to the sensor circuit when this switch is off, so the current from the constant voltage circuit side can be small, so leakage current It is possible to construct small switches. In addition, by connecting a resistor in series with the collector of the transistor in the constant voltage circuit, a steep charging current is prevented from flowing to the smoothing capacitor when an external power supply is applied, and the external load is prevented from malfunctioning. be able to.

[Brief explanation of the drawing]

Figure 1 is a wiring diagram showing an embodiment of an AC 2a type non-contact switch according to the present invention, and Figure 2 is a wiring diagram showing an example of a conventional AC 2-wire type non-contact switch. 1: AC power supply, 2: load, 3: rectifier circuit, 4: main thyristor, 10: sensor circuit, 12: capacitor, 16: transistor, 21: resistor.

Claims (1)

[Claims] 1) A rectifier circuit in which a series circuit of an AC power source and a load is connected between both input terminals, a main thyristor connected between both output terminals of this rectifier circuit and having a gate circuit, and a predetermined phenomenon detected. A sensor circuit that sends a signal, a capacitor connected in parallel with this sensor circuit, a constant voltage circuit connected between both output terminals of the rectifier circuit, and a detection signal of the sensor circuit that connects the sensor circuit and the gate. An AC two-wire type non-contact switch, characterized in that the circuit includes a transistor that switches the voltage of the constant voltage circuit and supplies power.