JP3248623B2 - Non-contact switch - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-contact switch which has a semiconductor device such as a triac and drives a load by turning on / off a main circuit by controlling on / off of the semiconductor device.

[0002]

2. Description of the Related Art FIG. 2 shows a conventional example of a contactless switch. In FIG. 2, reference numeral 1 denotes an input terminal of an input voltage of an operation power supply such as AC 100 V or 200 V, 2 denotes a contactless switch, 3 denotes a main circuit power supply, and 4 denotes a load. The internal configuration of the contactless switch 2 includes an input circuit 2A, a firing circuit 2B, and a main circuit 2C.

The input circuit 2A includes a diode bridge circuit DB having an AC terminal connected to the input terminal 1 of the operation power supply, voltage-dividing resistors R ₁ and R ₂ connected to the DC terminals of the diode bridge circuit DB, and a voltage dividing circuit. A smoothing capacitor C ₁ connected in parallel with the resistor R ₂ , a constant voltage circuit 21 connected to the DC terminal of the diode bridge circuit DB, a voltage dividing resistor R _{4 for} dividing the output voltage of the constant voltage circuit 21, R
_{5. The} reference voltage divided by the voltage dividing resistors R ₄ and R ₅ and the resistor R divided by the voltage dividing resistors R ₁ and R _2.
Comparator 2 which compares the voltage supplied via ₃
2. The comparator 22 includes a feedback resistor R ₆ and fixed resistors R ₇ and R ₈ .

[0004] firing circuit 2B terms of the non-contact switch 2, the transistor Tr whose base is connected to the output of the comparator 22 through a fixed resistor R _8, which are connected in series with the collector-emitter path of the transistor Tr photodiode photocoupler PC consisting phototriac for receiving light emitted from the photo diode, fixed resistors R of the photo-coupler PC current limiting resistor connected in series with the triac R ₉ and ignition voltage for generating
_{Consists of ten} .

The main circuit 2C of the contactless switch 2 comprises a triac TRC inserted in series with the main circuit power supply 3.

In FIG. 2, when the voltage level of the input voltage of the operating power supply currently supplied to the input terminal 1 is low and the output of the comparator 22 is at "L" level, the transistor Tr
Is off, the photocoupler PC is off, and the triac TRC is also off. When the voltage level of the operation power supply rises and the voltage divided by the voltage dividing resistors R ₁ and R ₂ reaches the reference voltage divided by the voltage dividing resistors R ₄ and R ₅ , the comparator 22 is inverted. The output becomes “H” level, whereby the transistor Tr is turned on and the photocoupler PC is turned on.

[0007] triac TRC on the voltage drop across the fixed resistor R ₁₀ of the photocoupler PC is generated is turned on load is driven. Compared voltage output is "H" voltage to the comparison voltage side through a feedback resistor R ₆ to be a level is positive feedback configured comparator 22 rises as the voltage detection circuit, thereby the comparator 22 hysteresis operation The contactless switch 2 operates stably even if the voltage level of the operation power supply fluctuates.

[0008]

In the above-mentioned conventional example, the number of components such as a constant voltage circuit and a comparator is increased, and there is a disadvantage that the area of a printed circuit board for mounting this circuit is increased.

The constant voltage circuit is usually constituted by a transistor circuit.
In order to convert a voltage of 00V to, for example, about 10V DC,
A transistor with a high withstand voltage is required, and there is a problem that a large-sized and high-cost non-contact switch as a whole is obtained.

SUMMARY OF THE INVENTION An object of the present invention is to provide a small and inexpensive contactless switch which eliminates the above-mentioned conventional disadvantages.

[0011]

In order to achieve the above object, the present invention provides an input circuit connected to an operation power supply for determining a voltage level of an input voltage, and a main circuit having a semiconductor element connected in series to a load. And a non-contact switch including a firing circuit for providing a control signal to a main circuit according to an output from the input circuit, wherein the input circuit includes a thyristor element;
A first zener diode for determining an operation input voltage when the thyristor element is turned on, a second zener diode for determining an operation input voltage when the thyristor element is turned off, and the first and second zener diodes. And a voltage dividing resistor for determining a voltage to be applied to the second Zener diode, and energizes the ignition circuit in response to ON / OFF of the thyristor.

[0012]

A thyristor element, a first Zener diode for determining an operation input voltage when the thyristor element is turned on, and a second Zener diode for determining an operation input voltage when the thyristor element is turned off By configuring an input circuit with the voltage dividing resistor that determines the voltage applied to these two Zener diodes, a means for performing voltage detection and hysteresis operation in the input circuit of the contactless switch is achieved.

That is, by using a simple system using a thyristor as an input circuit for determining the input voltage level from the operation power supply, an inexpensive and small non-contact switch can be obtained.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a circuit diagram of a contactless switch according to an embodiment of the present invention. The same components as those in the conventional example shown in FIG. 2 are denoted by the same reference numerals, and detailed description is omitted. I do.

FIG. 1 differs from the conventional example in the input circuit 2 A of the contactless switch 2.

[0017] In the input circuit 2A, the input voltage V ₁ of the operation power source is divided by the circuit impedance of the resistor R ₁ and R ₁ after the input stage. When the input voltages V ₁ gradually increased from 0 volt, the circuit voltage V ₂ is determined by the voltage division ratio of the resistors R ₁ and R _2, increases with increasing input voltages V _1.

[0018] The circuit voltage V ₂ is a Zener diode ZD1
, The current is supplied to the gate of the thyristor THY, and the thyristor THY is turned on. The input voltage V ₁ at this time is V _ON.

When the thyristor THY is turned on, a current is supplied to the primary side of the phototriac coupler PC, and the main circuit triac TRC is turned on in the same manner as in the conventional example.
A current flows through the load 4.

Next, the main circuit triac TRC is from the on state, a case is described in which lower the operation input voltage V _1.

[0021] Since the thyristor THY is on, the impedance of the resistor R ₂ in parallel circuit is reduced, the circuit voltage V ₂ which is determined by the voltage division ratio of the resistors R _1, as compared with immediately before the triac TRC is turned on Lower. When lowering the operating input voltage V _1, will further circuit voltage V ₂ is reduced, when the V ₂ is below the sum of the Zener voltage and the thyristor THY ON voltage of the Zener diode ZD2, the current flowing through the resistor R ₄ is The thyristor THY decreases rapidly, becomes less than the holding current of the thyristor THY, and turns off.

When the thyristor THY is turned off, the current supply to the primary side of the phototriac coupler PC stops,
As a result, no current flows to the load 4. The operation input voltage V ₁ at this time is V _OFF. V _ON > V _OFF and the hysteresis operation becomes possible.

The values of V _ON and V _OFF are determined by the ratio of the divided impedance of the resistor R _{1 and the} like, and the Zener diode ZD
By appropriately setting the zener voltages of the ZD1 and ZD2, it is possible to determine the operating voltage and the return voltage that meet the specifications of the contactless switch.

Thus, by employing the circuit configuration of the present embodiment, the number of components can be reduced by about 40% as compared with the conventional example, and a semiconductor device having a high withstand voltage is not required.

[0025]

As described above, according to the present invention, since the input circuit for determining the input voltage level from the operation power supply has a simple configuration using a thyristor, the number of parts of the input circuit can be reduced. In addition, since it is not necessary to use a high breakdown voltage semiconductor, the contactless switch can be housed in a small case, and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a contactless switch according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a conventional technique.

[Explanation of symbols]

1 operation input signal 2 contactless switch 2A input circuit 2B firing circuit 2C main circuit DB diode bridge R ₁ to R ₆ resistor C _1, C ₂ capacitors ZD1, ZD2 a Zener diode THY thyristor PC photo-triac coupler TRC triac third main Circuit power supply 4 Load

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H03K 17/725

Claims (1)

(57) [Claims] An input circuit connected to an operation power supply for determining a voltage level of an input voltage; a main circuit having a semiconductor element connected in series to a load; and a control signal transmitted to the main circuit according to an output from the input circuit. Wherein the input circuit comprises a thyristor element, a first Zener diode for determining an operation input voltage when the thyristor element is turned on, and a thyristor element. A second Zener diode for determining an operation input voltage when the thyristor is turned off, and a voltage dividing resistor for determining a voltage to be applied to the first and second Zener diodes, and responding to ON / OFF of the thyristor. And a non-contact switch for energizing the ignition circuit.