JPS5885633A - Two-wire system alternating current switching contactless switch - Google Patents

Abstract

PURPOSE:To reduce a leakage current in case when a switching element is turned on and off, and a voltage drop, by simple constitution, by triggering an SCR by a current flowing to a Zener diode for constituting a series type constant-voltage circuit connected to a rectifying circuit. CONSTITUTION:A series circuit of an AC power supply 101 and a load 102 is connected to a rectifying circuit 103, and to an output of the circuit 103, an SCR104, and a sensor circuit 109 for detecting an object to be detected, through a series type constant-voltage circuit 108 are connected, and to both terminals of the circuit 109, a capacitor C110 is connected. When the circuit 109 is in an off- state, a controlling transistor TR107 is turned on, the gate and the cathode of the SCR104 are short-circuited, the SCR104 is turned off, a current is supplied to the circuit 109 through the circuit 108, and the C110 is charged. When the circuit 109 is on, the TR107 turns off, the gate of the SCR104 is triggered by a current flowing to a Zener diode 108B of the circuit 108, the SCR is turned on, and the circuit 109 is operated by charge of the C110.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention has a sensor circuit that operates in the first class, such as a high frequency oscillation type proximity switch circuit or a photoelectric switch circuit, and detects a load switching thyristor (
The present invention relates to a non-contact switch that controls a switching element such as an SCR (hereinafter referred to as SCR), turns on or off two AC lines as if it were a contact switch, and opens and closes an externally connected load.

The following performance is required for this type of non-contact switch.

(1) When the switching element is in the OFF state, the current for operating the sensor circuit is supplied via an external load, so it is desirable that the current be as small as possible.

That is, if this current is large, it may cause malfunction or release failure in the case of a load such as a relay.

(2) On the other hand, when the switching element is in the on state, it is desirable that the current supply for operating the sensor circuit does not cause a drop in the voltage applied to the external load or cause large heat generation in the components. In other words, as described later, methods have been devised to supply current by connecting a Zener diode in series with the switching element and supplying the current by the voltage drop that occurs between the two terminals. This not only reduces the voltage applied to the external load but also causes the Zener diode to generate heat.

As this type of non-contact switch, the ones shown in FIG. 1 and FIG. 2, respectively, have been devised.

In Figures 1 and 2, 1 is an AC power supply, 2 is a load, 8 is a rectifier circuit, 4 is a 5CR15 Zener diode, 6 is a resistor, 7 is a transistor for trigger control of 5CR4, 8 is a transistor 8A and a Zener Diode 8B
and a DC type constant voltage circuit consisting of a resistor 8C, 9 a sensor circuit, 10 a capacitor, 11.18 a resistor, 12.14
15 is a Zener diode, 16 is a resistor, and 17 is a capacitor.

In the method shown in FIG. 1, when 5CR4 is off, the current supply to the sensor circuit 8 is set in series. This is done by the pressure circuit 8. On the other hand, when 5CR4 is in the on state, current is supplied to sensor circuit 9 via resistor 11 and diode 12 due to a voltage drop occurring across Zener diode 5 connected in series with 5CR4. In such a configuration, when 5CR4 is on, most of the load current flows through the Zener diode 5, which generates a large amount of heat. For example, if the load current is 200 mA and the voltage of the Zener diode 5 is 7 V, heat corresponding to about 1.4 W of electrical energy will be generated, which has the disadvantage that it is not possible to miniaturize the components. On the other hand, a gate current for turning on 5CR4 is supplied via resistor 6, but when 5CR4 is off, transistor 7 is on and the current flowing through resistor 6 flows to the collector side of transistor 7. Therefore, in the circuit shown in FIG. 1, when sep, 4 is off, in addition to the current for operating sensor circuit 9,
4 is consumed through the resistor 6 and transistor 7, resulting in a large amount of leakage current.

The method shown in FIG. 2 was devised to remove the bald spots mentioned above with respect to the method shown in FIG.

In this system, when 5CR4 is off, current is supplied to the sensor circuit 9 by the series type constant voltage circuit 8, as described above. On the other hand, when 5CR4 is off, transistor 7 is turned on, and if the voltage between the anode and cathode of 5CR4 is as high as the voltage of Zener diode 15, gate current is supplied and 5CR4 is turned on. However, the method shown in FIG. 2 has a drawback that when transistor 7 is off, a voltage approximately the same as the voltage applied across 5CR4 is applied between the collector and emitter of transistor 7. For example, if the operating power supply 1 of this non-contact switch is AC 200v, the maximum value of this voltage will reach approximately 20 oxJTv,... Ru.

An object of the present invention is to provide a two-wire AC switching non-contact switch that eliminates the above-mentioned drawbacks with a simple circuit configuration and has a small leakage current when the switching element is off and a small voltage drop when the switching element is on. There is a particular thing.

The present invention includes a rectifier circuit in which a series circuit of an AC power source and a load is connected between its inner input terminals, a thyristor as a switching element connected between both output terminals of the rectifier circuit,
connected between the two output terminals via a series type constant voltage circuit consisting of a transistor, a Zener diode, and a resistor,
A sensor circuit that detects a detected object and outputs a detection output, a capacitor connected between both ends of this sensor circuit, and a control that is inserted into the anode side of the Zener diode and is turned off by a detection signal from the sensor circuit. The above object is achieved by providing a 2.W-type AC on/off switch which is equipped with a transistor for controlling the thyristor and a trigger control signal for the thyristor is taken out from a connection point between the Zener diode and the control transistor.

Next, the present invention will be explained in detail based on examples.

FIG. 4 shows an embodiment in which the present invention is applied to a proximity switch.

In FIG. 4, 101 is an AC power supply, 102 is a load, 1
03 is a rectifier circuit, 104 is S as a switching element
CR, 107 is a transistor for trigger control of the SCR 104, 108 is a series type constant voltage circuit consisting of transistors 108, 4, Zener diode 108B, and resistor 108C, 109 is a sensor circuit consisting of an oscillation circuit, an amplifier circuit, etc. 110 is a smoothing capacitor, 117
indicates the detection coil. Transistor 107 is connected to its base to receive the output signal of sensor circuit 109, and when sensor circuit 109 is off, it is turned on by being supplied with a base current. Note that T1 and T2 indicate output terminals of this non-contact switch.

With this configuration, when the sensor circuit 109 is off, the transistor 107 is on, and the 5CR104
is in an off state with the gate and cathode shorted. At this time, current is supplied to the sensor circuit 109 by the series type constant voltage circuit 108. That is, when the voltage across the SCR 108 is lower than the Zener voltage of the Zener diode 108B, all the current flowing through the resistor 108 (?) flows to the base of the transistor 108A, and the transistor 108A is almost in an on state, and the □ capacitor 11
0 is quickly charged. Next, when the voltage across the SCR 104 becomes higher than the Zener voltage of the Zener diode 108B, the series type constant voltage circuit acts, and the sensor circuit 109
The voltage across the Zener diode 108B is the Zener voltage fVz, and the voltage across the transistor 08. If the voltage between the base and emitter of (2VBE) is approximately Vz-J'BE
A constant voltage of is applied. On the other hand, at this time, the resistor 108
The current flowing through transistor 108. The current iB flowing to the base of the transistor 108A is divided into the base of the transistor 108A and the Zener diode 108B.
The current consumption of transistor 09 is +L.If the amplification factor of transistor 08A is AFK, then 1B=1+AFE. Generally, the current consumption of the sensor circuit 109 such as a proximity switch is about 1 mA, so if AFE is large enough, t
B only flows slightly and the rest is Zener diode 108
Flows to B.

Next, when the sensor circuit 109 is turned on, the resistance 10 is now 1.
8C, Zener diode 108B, ) transistor 10
When the transistor 107 is turned off, the current flowing through the transistor 107 flows to the gate of the 5CR 104, and the 5CR 104 is turned on, and the voltage across it becomes approximately OV. Therefore,
Current is not supplied to the sensor circuit 109 through the transistor 108Ak, and the sensor circuit 109 is connected to the capacitor 110.
continues to operate while consuming electric charge. The power supply 101 has a commercial frequency, and for example, when this frequency is 50H2, the SCR 104 that is turned on turns off once every 10 m5ec (half cycle).

At this time, since the capacitor 110 has been charged to a certain extent, 5CR104 is turned on again because the capacitor 110
is charged by the series constant voltage circuit as described above, and the resistor 1
This occurs when the current flowing through 08C is shunted to Zener diode 108B. Thereafter, this operation is repeated while the sensor circuit 109 is in the on state.

FIG. 4 shows another embodiment in which the present invention is applied to a proximity switch. In this FIG. 4, elements corresponding to those shown in FIG. 8 are designated by the same reference numerals as in FIG. 8, 118 being a transistor, 119 . ．． 120 each represents a resistance.

The configuration in FIG. 4 differs from that in FIG. 3 in that when the transistor 107 is off, the current flowing through the Zener diode 108B does not flow directly into the gate of the 5CR 104;
5CR1 after current amplification sound with transistor 118
The method was adopted to allow the water to flow through the 04 gate.

The collector of the transistor 118 is a current limiting resistor 12.
0 to the emitter of transistor 108/f, whose emitter is connected to the gate of SCR 104.

According to the configuration shown in FIG. 4, the 5CR 104 can be triggered even if the current flowing through the Zener diode 108B is small, so the value of the resistor 108C can be increased. In other words, transistor 108A turns on and SCR 104
It is possible to reduce the current in the entire circuit when the switch is off. On the other hand, when the transistor 108A turns off and the transistor 118 turns on, the gate current of the 5CR104 (or the device S formed from the emitter side of the transistor 108A)
When CR104 is turned on, the voltage across it is approximately Oν
Therefore, resistor 108C, Zener diode 108C
The current flowing through C' to the base of transistor 118 also disappears, and transistor 18 is turned off. Therefore, the current flowing to the gate of the SCR 104 is pulsed, hardly consuming the charge of the capacitor 10, and a transistor 118 having a low breakdown voltage can be used.

Note that in the embodiments shown in FIGS. 8 and 4, an NPN (NPN) transistor is used as the transistor 07, so
The anode of the Zener diode 108B in the series type constant voltage circuit was connected to the collector of the transistor 07, but it is clear that if a PNP transistor is used as the transistor 07, the anode of the Zener diode would be connected to the emitter of the same transistor. .

As described above, according to the present invention, S
Since the sensor circuit is configured to trigger the CR, (1) the circuit configuration is simple; (2) the SCR is triggered after the capacitor is charged to the desired voltage, so the sensor circuit can always operate stably. (q) Less heat generation (power loss) when S CR is on, (4) S CR17
Advantages such as less electric current can be obtained even when the hair is turned on.

The present invention can be applied to photoelectric switches and other detection switches in addition to the oscillation type proximity switch described above.

[Brief explanation of drawings]

Figures 1 and 2 show the conventionally proposed 2#, respectively.
! FIG. 8 shows one embodiment of the present invention, and FIG. 4 shows another embodiment of the present invention. 103: Rectifier circuit, 104: SCR. 108: Series constant pressure circuit, 108. f:) transistor, 108B: Zener diode, 1o8C: resistor, 1
09: Sensor circuit, 110 Nico/Densa, 107:
) Rigger control transistor, 118:) UZ transistor,
119,120:'Resistance. 1 fig. V 謬, 3 fig. 0 δ

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 thyristor connected between both output terminals of the rectifier circuit, and a transistor, a Zener diode, and a resistor between the two output terminals. a sensor circuit connected through a series constant voltage circuit consisting of a sensor circuit that detects an object to be detected and outputs a detection output, a capacitor connected between both ends of this sensor circuit, and an anode side of the Zener diode. 2, further comprising a control transistor inserted into the sensor circuit and turned off by a detection signal from the sensor circuit, and a trigger control signal for the thyristor is taken out from a connection point between the Zener diode and the control transistor. Wire type AC open/close contactless switch.