JPH0645903A - Two-wire electronic switch - Google Patents

Abstract

PURPOSE:To obtain a two-wire electronic switch to be used even when either of DC and AC is used as a power supply. CONSTITUTION:A diode bridge 5 is connected between 1st and 2nd terminals 1, 2. A constant voltage circuit 12 and a thyristor 6 are connected to the positive pole terminal of the bridge 5. The cathod terminal of the thyristor 6 is connected to the output terminal of the circuit 12 through a resistor R2 so as to be connected to a reference circuit 10 in a DC two-wire electronic switch. When a transistor (TR) 11 in the electronic switch is turned on, the thyristor 6 is triggered through the resistor R2, and when the TR 11 is turned off, the thyristor 6 is immediately turned off. Thereby either of DC and AC can be connected as a power supply 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-wire type electronic switch which can be used with both AC and DC.

[0002]

2. Description of the Related Art As a conventional two-wire type electronic switch, as shown in, for example, JP-A-60-36655, either an AC two-wire type electronic switch or a DC two-wire type electronic switch is used. Is used. In the AC two-wire electronic switch, a load and an AC power source are connected in series to a pair of terminals. A diode bridge is connected between the terminals, and a switching element such as a thyristor and a sensor circuit are connected in parallel with the diode bridge. A capacitor is connected in parallel to the sensor circuit in order to supply a constant power.When the detection circuit is on, the thyristor is turned on, power is supplied to the load at a specified conduction angle, and when non-conduction, the capacitor is charged. Power to the sensor circuit.

A direct current two-wire type electronic switch has a constant voltage circuit and a load switching element connected between a pair of terminals so that the constant voltage circuit suppresses a large fluctuation in voltage to operate a sensor circuit. There is.

[0004]

However, such a conventional DC two-wire type electronic switch is manufactured independently for DC or AC, and these cannot be shared.

The present invention has been made in view of such conventional problems, and can be used for both direct current and alternating current without changing the basic circuit of the direct current two-wire type electronic switch. An object is to provide a two-wire electronic switch.

[0006]

The present invention is a two-wire type electronic switch in which a load and a power source are connected in series between first and second terminals, which is connected between the first and second terminals. Direct current having a diode bridge, a switching element for short-circuiting a pair of terminals of positive and negative ends, a sensor circuit for giving a switching signal to the switching element, and a first constant voltage circuit for supplying a constant voltage to the sensor circuit Two-wire electronic switch basic circuit, a thyristor connected between the positive terminal of the diode bridge and the positive terminal of the DC two-wire electronic switch basic circuit, a second constant voltage circuit connected to the diode bridge, and a constant voltage One end is commonly connected to the output end of the circuit and the gate of the thyristor, and the other end is connected to the positive end of the direct current two-wire type electronic switch, and a resistor is provided.

[0007]

According to the present invention having such a feature, when a DC or AC power source and a load are connected in series between the first and second terminals, they are rectified by the diode bridge and the DC voltage is fed through the constant voltage circuit. Power is supplied to the basic circuit of the two-wire electronic switch. When the sensor circuit of the DC two-wire type electronic switch turns on the switching element therein, the current flowing through the resistor increases and the thyristor is triggered. After that, the alternating current causes the thyristor to turn off at each zero-cross point, but immediately turns on, so that power is continuously supplied. When the power source is DC, the thyristor continuously turns on without repeating turn-on and turn-off at each zero-cross point. When the output of the basic circuit of the DC two-wire type electronic switch is turned off, the switching element therein is also turned off, so that the thyristor can be immediately turned off.

[0008]

1 is a block diagram showing the overall construction of a two-wire type electronic switch according to an embodiment of the present invention. In the figure, a load 3 and an AC or DC power supply 4 are connected in series between the first terminal 1 and the second terminal 2. Now this terminal 1,
A diode bridge 5 is connected between the two as shown in the figure, and the anode of the thyristor 6, the drain of the power MOSFET 7 and the resistor R1 are connected to the positive terminal thereof.
The gate terminal of the thyristor 6 is commonly connected to one end of the resistor R2 and the source end of the power MOSFET 7, and further connected to the gate terminal of the FET 7 via the Zener diode 8. The other end of the resistor R1 is connected to the gate terminal of the FET 7, and further connected to the negative end of the diode bridge 5 via the Zener diode 9. This power MOSFET 7
Has a withstand voltage corresponding to the power supply voltage. For example, when a commercial AC power supply is connected, it has a withstand voltage of several hundreds of volts. The FET 7, the resistor R1, and the Zener diode 9 constitute a second constant voltage circuit.
The Zener diode 8 is a protection diode for the power MOSFET 7.

The common connection end of the cathode of the thyristor 6 and the resistor R2 is connected to the positive end 10a of the basic circuit 10 of a normal DC two-wire electronic switch. This basic circuit 10 is, for example, as shown in FIG. 1, a transistor 11 which is a switching element, a first constant voltage circuit 12 and a sensor circuit 1.
3 is included. The sensor circuit 13 is composed of, for example, an oscillation circuit, a detection circuit for detecting a decrease in the oscillation amplitude thereof, a comparison circuit, and the like, and supplies a switch signal to the transistor 11. The negative terminal 10b of the basic circuit 10 of the direct current two-wire type electronic switch is connected to the negative terminal of the diode bridge 5 and the anode terminal of the Zener diode 9 constituting the constant voltage circuit.

Next, the operation of this embodiment will be described. For example, when an AC power source is connected as the power source 4, the voltage at the positive terminal A with respect to the negative terminal G of the diode bridge 5 undergoes full-wave rectification and changes as shown in FIG. This voltage becomes a constant voltage substantially determined by the Zener diode 9, and a pulsating voltage as shown in FIG. 2B is supplied to the basic circuit 10 of the DC two-wire electronic switch via the power MOSFET 7 and the resistor R2. It As a result, almost DC voltage is also supplied to the basic circuit 10 of the DC two-wire electronic switch. Since the constant voltage circuit 12 is provided in the basic circuit 10 of the direct current two-wire type electronic switch, the voltage is further stabilized in the basic circuit 10 to a predetermined voltage and applied to the sensor circuit 13. It should be noted that the period T1 shows a state in which the object is not approaching.

Now, during the period T2 when an object or the like approaches the vicinity of the sensor circuit 13, the sensor circuit 13 detects the object and a switch signal is given to the transistor 11.
Therefore, the switch 11 is turned on and the current flows through the resistor R2. When the voltage drop of the resistor R2 becomes large, the thyristor 6 is triggered, and the load current of the load 3 flows through the diode bridge 5, the thyristor 6, and the switching transistor 11 in the basic circuit 10. The voltage between the gate of the thyristor 6 and the positive terminal of the DC two-wire basic circuit 10 increases, and the thyristor 6 turns off at every zero cross, but the voltage of the resistor R2 increases as the voltage increases, so the thyristor 6 triggers. It will be turned on immediately after the zero cross.

When the object is separated from the sensor circuit 13, the output from the sensor circuit 13 is stopped and the transistor 11 is turned off. Therefore, the thyristor 6 immediately turns off before reaching the zero cross point, that is, the holding current or less. Therefore, the time until turn-off is shortened as compared with the conventional AC two-wire type electronic switch, and the responsiveness can be improved. Also, when a DC power source is connected as the power source 4, a constant voltage is supplied to the positive end of the diode bridge 5 instead of the pulsating current as shown in FIG. 2 (a). Is exactly the same as when AC power is connected. Therefore, either AC or DC power source can be used as the power source 4.

[0013]

As described in detail above, according to the present invention, the basic circuit of a direct current two-wire type electronic switch is used as it is, and an additional circuit is connected to the basic circuit to supply power to both direct current and alternating current. It can be a two-wire type electronic switch for both AC and DC that can be connected as. Also, the basic circuit of a normal DC 2-wire electronic switch is an IC.
Since it is realized, it is possible to configure by connecting a few additional circuits without changing the IC circuit itself. In addition, since a switching element is provided in the basic circuit of the DC two-wire type electronic switch and the element is turned on immediately by turning off this element, the response of the electronic switch can be improved even when an AC power source is used. Can also be obtained.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration of a two-wire electronic switch according to an embodiment of the present invention.

FIG. 2 is a time chart showing the operation of this embodiment.

[Explanation of symbols]

 1, 2 terminals 3 load 4 power supply 5 diode bridge 6 thyristor 7 power MOSFET 8, 9 Zener diode 10 DC two-wire type electronic switch basic circuit 11 transistor 12 constant voltage circuit 13 sensor circuit

Claims (2)

[Claims] 1. A two-wire type electronic switch in which a load and a power supply are connected in series between first and second terminals, and a diode bridge connected between the first and second terminals, DC two-wire electronic switch basic having a switching element for short-circuiting a pair of terminals of a positive electrode end and a negative electrode end, a sensor circuit for giving a switch signal to the switching element, and a first constant voltage circuit for supplying a constant voltage to the sensor circuit A circuit, a thyristor connected between the positive terminal of the diode bridge and the positive terminal of the DC two-wire electronic switch basic circuit, a second constant voltage circuit connected to the diode bridge, and a constant voltage circuit A resistor, one end of which is commonly connected to the output end and the gate of the thyristor, and the other end of which is connected to the positive end of the DC two-wire electronic switch. Child switch. 2. The second constant voltage circuit is a power MOS
The two-wire electronic switch according to claim 1, further comprising an FET and a Zener diode for stabilizing the gate voltage.