JPS5811774B2 - Switching Souch - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a switching device that is turned on and off by a detection signal from a detection circuit.

A switching device that is turned on and off by a detection signal from a detection circuit requires power to operate the detection circuit.

In a three-wire switching device, a separate circuit is provided to supply power to the detection circuit, so the current flowing to the load is intermittent when the switch is turned off and on, and the detection circuit is always in an operating state.

In a two-wire switching device that supplies power to a detection circuit through a load, it is inevitable that current flows through the load even when the switch is off.

Therefore, it is required to minimize the current flowing through the load when the switch is turned off, that is, a switching device that operates with a minute current is required.

This is because the function of the switching device is to energize the load when it is on and not to energize the load when it is off.

Conventionally, three-wire switching devices have been widely used because of the difficulty in technically solving the contradictory demands of minimizing the current flowing through the load during off-state and operating the detection circuit.

By the way, many switching devices are used, for example, as proximity switches, photoelectric switches, etc., in belt conveyor systems, various control systems, and the like.

The more switching devices installed, the more complicated the wiring becomes.

This is especially true when the wiring distance is long.

Therefore, a two-wire switching device that performs its function with two wires and is easy to handle is desired.

In addition, switching devices are required to be downsized in order to secure an installation location and to facilitate handling.

Furthermore, one switching device can be applied to a wide range of applications even when the operating voltage changes (for example, from 100V to
400V) Those that operate normally have higher utility value.

In order to achieve miniaturization, it is necessary to design the circuit so as to avoid heat generation in the switching device itself and heat generation due to load current, and to eliminate the need for heat dissipation means.

In order to withstand a wide range of operating voltages, it is necessary to incorporate a constant voltage circuit to ensure stable operation of the detection circuit.

Further, it is preferable that the switching device performs a zero-voltage switching operation of turning on and off at a voltage zero point.

This is because if the power supply voltage is turned on at a time when it is not zero, a steep current flows through the load, which not only adversely affects the load, but also causes inconveniences such as generation of surge voltage, which becomes a source of noise.

The present invention was made in view of this situation, and an object of the present invention is to provide a switching device that has a constant voltage circuit with few power contacts, extremely reduces unnecessary power consumption, performs zero-voltage switching operation, and operates with a minute current. With the goal.

In order to achieve this object, the present invention includes a first three-terminal switching element for switching a load connected in series with a load to a power supply, and a detection circuit for controlling the first three-terminal switching element. A switching device configured such that the first three-terminal switching element is controlled on and off by a control signal from the detection circuit, a second three-terminal switching element for control to be connected in series to a power supply line; A voltage detection element that detects that the output voltage of the second three-terminal switching element exceeds a predetermined value near zero voltage and generates an output; an open/close type constant voltage circuit consisting of a third three-terminal switching element that shuts off a control signal applied to the terminal switching element and turns off the second three-terminal switching element; a fourth three-terminal switching element that, when controlled and turned on, prevents the output of the voltage detection element from being sent to the third three-terminal switching element and sends this output to the first three-terminal switching element; The second three-terminal switching element and the detection circuit are connected in series, and the series circuit is connected between both ends of the first three-terminal switching element.

EMBODIMENT OF THE INVENTION Hereinafter, an embodiment in which the present invention is applied to a two-wire reflective optical switch will be described in detail with reference to the drawings.

FIG. 1 shows an electrical circuit diagram of one embodiment.

In this figure, a load 11 and a switching circuit are connected to an AC power source.

The switching circuit includes a full-wave rectifier circuit 12, a 5CR13 as a three-terminal switching element for load switching, a detection circuit,
It consists of a constant voltage circuit, a smoothing circuit, etc.

The detection circuit includes an oscillation circuit 24, a light emitting diode 25 as a light emitting means, and a phototransistor 26 as a light receiving means.
, and a signal processing circuit 27.

The oscillation circuit 24 is composed of, for example, a multivibrator circuit, and sends a pulse output to the light emitting diode 25.

The reason why the light emitting diode 25 is lit in pulses is to instantaneously emit a large amount of light energy and reduce average current consumption.

Further, noise resistance can also be improved.

The light reflected by the object to be detected 28 is received by the phototransistor 26 and converted into an electrical signal.

The signal processing circuit 27 generates a detection signal (control signal) "1" based on the output of the phototransistor 26, and is composed of, for example, a detection circuit, a level discrimination circuit, and the like.

Furthermore, in order to reduce current consumption, a resistor with a high resistance value is used.

The detection signal "1" from the signal processing circuit 27 is sent to the base of the transistor 29 through a light emitting diode 30 and a resistor 33 as operation display means.

The light emitting diode 30 emits light only when the detection signal "1" is sent.

The constant voltage circuit uses transistor 1 as a switching element.
5, 16, Zener diode 20 as a constant voltage element
, a 5CR 19 for controlling transistors 15 and 16, a capacitor 21, and the like.

The transistors 15 and 16 control the conduction of the full-wave rectification input, and the reason why the two transistors are connected in series is to increase the withstand voltage.

That is, a resistor 17 is connected to the base terminal of the transistor 15.
The voltage at point b divided by and 18 is
Its emitter voltage, and therefore the collector voltage of transistor 16, is now also equal to the base voltage of transistor 15.

By making the values of resistors 17 and 18 equal, a voltage that is half the voltage at point b is applied to the collector of transistor 16.

Therefore, operation is possible even with a power supply voltage twice the allowable applied voltage of these transistors.

For example, if the breakdown voltage of the transistors 15 and 16 is 200V, it is possible to use a power supply voltage of up to 400V.

If more transistors are connected in series, a switching element with even higher breakdown voltage can be obtained.

Assuming that the detection signal "0" is now being sent from the signal processing circuit 27 to the base of the transistor 29, the transistor 29 is in an off state.

In this case, 5CR19 is controlled by the voltage at the 0 point.

That is, when the transistors 15 and 16 are on, the full-wave rectified input is charged to the capacitor 21 via the resistor 14 and the transistors 15 and 16.

If the breakdown voltage of the Zener diode 20 is Vz, then 0
When the voltage at the point reaches Vz, since the transistor 29 is off, a gate current flows to the gate of 5CR19.
19 is turned on.

When 5CR19 is turned on, the base voltages of transistors 15 and 16 become zero, and transistors 15 and 16 are turned off.

The detection signal “1” from the signal processing circuit 27 is sent to the transistor 2.
9, the transistor 29 is in an on state, so the current flowing through the Zener diode 20 flows to the transistor 29, and no gate current flows to the gate of 5CRI9.

Therefore, 5CR19 is not turned on by the voltage at the 0 point.

Therefore, transistors 15 and 16 are in the on state, but as will be described later, when 5CR13 is on, 5CR1
Since the capacitor 3 is energized, the capacitor 21 is charged only when the capacitor 5CR13 is off.

Note that the resistor 14 is a protective resistor that limits a sudden increase in charging current at the moment when the transistors 15 and 16 are turned on, and may be replaced by a choke coil.

When a choke coil is used, power loss is extremely low.

The Zener diode 20 provides a reference voltage, and it is more preferable to use a temperature compensated voltage regulator diode.

5CRI9 can also be used with other three-terminal switching elements, such as programmable unijunction transistors (
PUT) etc. may be substituted.

The smoothing circuit is composed of a resistor 22 and a capacitor 23.

A choke coil may be used in place of the resistor 22, and when a choke coil is connected, a π-type filter is formed and the ripple rate is reduced.

The three-terminal switching element 5CR13 for load switching has its gate terminal connected to the cathode terminal of the Zener diode 20 via the diode 32, and is controlled by the zero point voltage and the transistor 29.

That is, when the detection signal "0" is sent from the signal processing circuit 2γ, a current flows through the Zener diode 20 when the voltage at the 0 point exceeds Vz as described above.

Here, since the voltage drop vR due to the resistor 31 and the voltage drop VD due to the diode 32 are selected so that VR<VD, 5CR1
Only 9 is turned on, and 5CR13 remains off.

If the detection signal “1” is sent, transistor 2
9 is in the on state, when the voltage at point 0 reaches VZ+VD, gate current flows to the gate of 5CR13 and 5C
R13 is turned on.

However, if 5CR19 is on when the detection signal "1" is sent, transistors 15 and 16 are off, and discharge is occurring from capacitor 21 through resistor 22, so the voltage at point 0 is less than VZ+VD. Low, 5CR1
3 is not turned on.

In this case, after the power supply voltage becomes zero and 5CR19 is turned off, 5CR13 is turned on when the voltage at the 0 point reaches VZ+VD.

Next, the operation of the circuit shown in FIG. 1 will be described in detail for the cases where the detection signal is "0" and the case where the detection signal is "1", with reference to the operational waveform diagram shown in FIG.

FIGS. 2a to 2d and g show voltage waveforms at each connection point a to d and g in FIG. 1, and e and f.

h indicates the current waveforms at points e, f, and h, respectively.

First, when the detection signal from the signal processing circuit 27 is "0",
That is, during the time between t1 and t4, the voltage at point a is zero, and the transistor 29 is in an off state.

A full-wave rectified waveform of the power supply voltage is shown at point b.

Transistors 15 and 16 until the voltage at point c reaches VZ
is on, and as the power supply voltage increases, the capacitor 21 is charged.

When the voltage at point 0 reaches VZ at time t2, since the transistor 29 is off, a gate current flows to the gate of 5CR19 through the Zener diode 20.
9 turns on.

Therefore, the potential at point d becomes zero and the transistor 15°1
6 is off.

Further, the charge stored in the capacitor 21 is discharged through the resistor 22.

This state continues until time t3 when the voltage at point b becomes zero, that is, half a cycle of the power supply voltage.

At time t3, 5CR19 is turned off, transistors 15 and 16 are turned on, and charging of capacitor 21 is started again.

When the voltage at the 0 point reaches vz, the 5CR19 is turned on again and the transistors 15 and 16 are turned off.

Since the above operation is repeated, the voltage waveform at point 0 is a repeating waveform of charging and discharging, and the voltage at point g is the waveform of the resistor 22.
The voltage is smoothed by the capacitor 23 and becomes a stable constant voltage.

Therefore, stable power is supplied to the detection circuit regardless of fluctuations in the power supply voltage.

Further, even if the voltage of the power source used is changed (for example, from 100 V AC power source to 200 V AC power source), the voltage supplied to the detection circuit remains constant.

A voltage is applied to point d for the time T1 when 5CR19 is off.

Further, the gate current of 5CR19 is a pulse current as shown in e, and since no current flows through the gate of 5CR13, 5CR13 is naturally in an off state.

The current flowing through the load 11, that is, the current at point h, flows slightly only when the transistors 15 and 16 are on, and becomes as shown in the second diagram.

This minute instantaneous current supplies power to the detection circuit, and since the time T1 during which the transistors 15 and 16 are on is short and the average current is minute, the effect on the load 11 can be ignored.

Now, when the detection signal "1" is sent from the signal processing circuit 27 at time t4, the potential at point a rises rapidly.

If 5CR19 is in the on state at this time, the voltage at point d is zero, so the transistors 15 and 16 remain in the off state.

Therefore, the power at point 0 is lower than VZ+VD, 5CR1
No gate current flows to the gate of 3 and 5CR13 is off.

Furthermore, the voltages at the connection points S, C, D, and G are also the same as in the state of the detection signal "0", and energization to the load 11 through the 5CR13 has not yet started.

When the power supply voltage becomes zero at time t5, 5CR19 is turned off and transistors 15 and 16 are turned on.

Therefore, charging of the capacitor 21 via the resistor 14 and transistors 15 and 16 is started.

At time t6 after time T3, the voltage at point 0 is VZ+VD
When the voltage reaches 50, a gate current flows through the diode 32 to the 5CR13, and the SCRI3 turns on as shown in FIG. 2 (f).

Therefore, the load 11 is energized through the 5CR13.

At this time, 5CR19 is still off and transistors 15 and 16 are on, but since the voltage at point b becomes zero, capacitor 21 is not charged.

The charge on capacitor 21 is discharged through resistor 22.

The voltage waveform at point 0 is a charging/discharging waveform, and points b and d are t5 to t6.
The voltage is applied only at time T3.

Although the voltage at point g becomes slightly higher after time t6, a stable constant voltage is applied and does not affect the operation of the detection circuit.

As shown in the second diagram, the current at point h has a waveform that supplies power to the detection circuit during time T3 and supplies power to the load 11 at other times.

Note that time T3 is slightly longer than time T0.

When the detection signal "1" is sent in this manner, power is supplied to the detection circuit and at the same time, sufficient current is applied to the load 11.

Furthermore, energization to the load 11 is started at the voltage zero point.

Of course, even if the detection signal "1" is sent when the 5CR19 is in the off state, the same operation as in the above case is performed.

Further, the light emitting diode 30 emits light in response to the detection signal "1", and displays the detection signal "1".

When the detection signal of the signal processing circuit changes from "1" to "0" at time t7, the state returns to the state from t1 to t4 described above, but it goes without saying that the current to the load 11 stops at the voltage zero point at this time as well. be.

As described above, according to the present invention, the power supplied to the detection circuit is controlled by turning on and off the switching element of the constant voltage circuit, and the load is controlled near the zero point of the power supply voltage based on the output voltage of the constant voltage circuit. Since the 3-terminal switching element for opening/closing is turned on to start energizing the load, power consumption is extremely low, it can be made smaller, it can be operated with a very small current, and it can withstand a wide range of operating voltages. Zero-voltage switching realizes a switching device that does not cause malfunctions.

It goes without saying that the present invention is not limited to the above embodiments, as it may be applied to many other switching devices such as proximity switches, touch switches, non-contact microswitches, etc.

[Brief explanation of the drawing]

FIG. 1 is an electric circuit diagram showing one embodiment of the present invention, and FIG. 2 is an operating waveform diagram of the above embodiment. 11...Load, 12...Full wave rectifier circuit, 13゜19...5CR114, 17, 18,
22,31゜33...Resistance, 15,16,29
...Transistor, 20...Zener diode, 21, 23...Capacitor, 24
......-Oscillation circuit, 25,30...Light-emitting diode, 26...Phototransistor, 2
7...Signal processing circuit, 28...Detected object, 32...Diode.

Claims (1)

[Claims] 1 Consisting of a first three-terminal switching element for switching the load, which is connected in series with the load to the power supply, and a detection circuit that controls the first three-terminal switching element, and a control signal from the detection circuit. In the switching device in which the first three-terminal switching element is controlled to turn on and off, a second three-terminal switching element for control is connected in series to the power supply line, and an output of this second three-terminal switching element. A voltage detection element that detects that the voltage has exceeded a predetermined value near zero voltage and generates an output, and a control signal that is turned on by the output of this voltage detection element and is applied to the second three-terminal switching element is cut off. and a third three-terminal switching element that turns off the second three-terminal switching element, and a switching type constant voltage circuit that is controlled to be turned on and off by a control signal from the detection circuit, and when turned on, the voltage is a fourth three-terminal switching element that prevents the output of the detection element from being sent to the third three-terminal switching element and sends this output to the first three-terminal switching element; A switching device characterized in that a terminal switching element and the detection circuit are connected in series, and the series circuit is connected between both ends of the first three-terminal switching element.