JP2882014B2 - Switch drive circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive circuit of a switch having a main contact for frequently opening and closing a current, such as a temperature controller.

[Conventional technology]

It is well known that two contacts facing each other to open and close DC current have a transfer phenomenon in which a part of one contact melts or evaporates and moves to the other contact side. Even when an AC current flows through a load, such as an electromagnetic switch, the same effect as switching DC current occurs if the direction of current when switching the current is always constant, and the transfer phenomenon of contacts between the two contacts that contact each other Occurs, and the contact surfaces of the two contacts have irregularities, the contact surfaces are roughened, the contact resistance increases, and finally the irregularities are fitted and the two contacts are locked in a closed state. . In order to prevent this, a contact material which does not easily cause the transfer phenomenon is usually employed, but is not always sufficient, and there is a disadvantage that the contact resistance is still increased even if the transfer phenomenon is reduced.

Therefore, an input signal circuit for half-wave rectifying the voltage of the AC power supply and a Schmitt circuit for determining the voltage of the input signal circuit and outputting an output signal are provided, and the switch is driven by the output signal of the Schmitt circuit. In a switch drive circuit, an oscillator that outputs a signal having a frequency lower than the frequency of the voltage of the AC power supply is provided, and the switch is driven by a logical output of a signal of the oscillator and an output signal of the Schmitt circuit. A drive circuit for such a switch has been disclosed (JP-A-63-94522). The switching circuit of this switch uses the logic output of the output signal of the oscillator and the output signal of the Schmitt circuit to randomly change the timing of opening and closing the contacts due to the suction and release of the drive circuit with respect to the phase of the voltage of the AC power supply. And to extend the life of the contacts.

[Problems to be solved by the invention]

Even in such a conventional configuration, the energizing direction at the time of opening / closing the contact may be biased to one side, which is not sufficient.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a switch drive circuit that more reliably prevents a contact transfer phenomenon and prolongs a contact life as compared with a conventional one.

[Means for solving the problem]

In order to solve the above-described problems, the present invention provides a drive circuit for a switch that opens and closes a main contact by turning on and off a drive contact, wherein the switching phase of the main contact is set, and the switching phase is set to a positive phase for each switching. And a phase control unit for switching to a negative phase, wherein the phase control unit generates a square wave voltage that generates a square wave voltage having a 180 ° phase difference from a half-wave voltage obtained by rectifying a power supply to be opened and closed by the switch. An integrating circuit for integrating the square wave voltage generated by the square wave generating circuit, a first differentiating circuit for differentiating the output of the integrating circuit via an inverting circuit, and a voltage obtained by inverting the output of the integrating circuit. A second differentiating circuit for differentiating through an inverting circuit, and a flip-flop that uses the output of the first and second differentiating circuits as a clock input and switches the output level every time the drive contact is turned on and off. Flip-flop output A drive output is obtained by embedding the logical product of the force and the outputs of the first and second differentiating circuits. Further, the integration circuit is composed of a capacitor and a resistor, and the resistor is a variable resistor having a resistance value capable of changing its output phase sufficiently.

[Action]

Contact wear is related to the contact bounce time at closing. The contact bounce time is related to the repulsive force of the movable iron core when the electromagnetic coil of the drive unit is energized and the movable iron core is attracted to the fixed iron core. Furthermore, since the repulsive force of the movable core is related to the phase of the current flowing through the electromagnetic coil, it is desirable that the closing phase of the switch be closed with the phase with the shortest bounce time, and this switching phase is set by the variable resistor of the integrating circuit, Further, the opening / closing phase is switched between a positive phase and a negative phase each time the main contact is opened / closed by the phase control unit, thereby preventing the contact from shifting to one side. The switching phase can be manually adjusted by changing the variable resistance of the integration circuit.

〔Example〕

FIG. 1 is a block diagram showing an embodiment of a switch driving circuit according to the present invention. Here, the drive circuit of the switch includes an input unit 1, a phase control unit 2, an output unit 3, and a power supply unit 4. The input unit 1 is connected to input a contact signal of a drive contact 5 to the phase control unit 2, The output terminal of the phase control unit 2 is connected to the output unit 3, and the output unit 3 includes an AC power supply 7 and a main contact 6 connected in series with a load 8. The input unit 1, the phase control unit 2, and the output unit 3 rectify and smooth the AC power supply 7 to a control power supply Vcc.
Signal voltage V _A that is driven by
Are connected so as to be applied to the phase control unit 2.

When the drive contact 5 is closed, this signal is input to the phase control unit 2 via the input unit 1, and the phase control unit 2 closes the main contact 6 of the output unit 3 at a preset voltage phase and energizes the load 8.
When the drive contact 5 is opened, this signal is input to the phase control unit 2 via the input unit 1, and the phase control unit 2 opens the main contact 6 of the output unit 3 with the same phase as when the power is turned on, and cuts off the current of the load 8. . Next, when the drive contact 5 is closed, this signal is input to the phase control unit 2 via the input unit 1, and the phase control unit 2 outputs the main contact of the output unit 3 at a phase shifted by 180 ° from the previously closed voltage phase. 6 is closed and the load is energized. When the drive contact 5 opens again, the main contact 6 opens at a phase shifted by approximately 180 ° from the previously opened phase and cuts off the current of the load 8. In this way, the phase control unit 2 opens and closes the opening / closing phase by shifting the opening / closing phase by approximately 180 degrees every time the main contact is opened / closed at the already set opening / closing phase.

FIG. 2 shows an example of a connection diagram of the input unit 1 and the phase control unit 2 in FIG. Here, the input unit 1 includes a series circuit of the resistor 9 and the drive contact 5 connected to the control power supply Vcc and an inverter connected to a connection point between the resistor 9 and the drive contact 5 of the series circuit.
Consists of ten. The phase control unit 2 includes a square wave generating circuit 11, an integrating circuit 12, two differentiating circuits 13, 14, and a logic circuit 15. In the square wave generation circuit 11, a series circuit of a resistor 16 and a collector / emitter of a transistor 17 is connected to a control power supply Vcc, and a half-wave rectified voltage _{VA of the} power supply section 4 is connected to a base of the transistor 17 via a resistor 18. Connected to be applied. The integrating circuit 12 is configured by connecting a capacitor 23 in series to a parallel circuit of a series circuit of a variable resistor 19 and a diode 20 connected to the collector of a transistor 17 and a series circuit of a variable resistor 21 and a diode 22. The differentiating circuit 13 outputs the output of the integrating circuit 12 to a capacitor 25 via an inverter 24.
And a resistor 26 connected in series with a resistor 27 and a diode 27
Are connected in parallel. The differentiating circuit 14 is configured such that the output terminal of the inverter 24 is further connected to a series circuit of a capacitor 29 and a resistor 30 via an inverter 28, and a diode 31 is connected in parallel with the resistor 30. The logic circuit 15 has one input terminal connected to the output terminal of the differentiating circuit 13 and the other input terminal connected to the output terminal Q of a D-type flip-flop (hereinafter abbreviated as FF) 36. The output terminal of the differentiating circuit 14 is connected to the input terminal, the other input terminal is connected to the output terminal of the FF36 and the input terminal D, the AND gate 33, and the output terminals of both AND gates 32, 33 are connected to the respective input terminals. The OR terminal whose output terminal is connected to the clock terminal T of FF35
The gate 34 and the output terminal of the inverter 10 are connected to the input terminal D, the clock terminal T is connected to the output terminal of the OR gate 34, the output terminal is connected to the clock terminal T of the FF 36, and the output terminal Q is connected to the first terminal.
FF 35 and AND gate 32 connected to output unit 4 shown in the figure
The other input terminal of the AND gate 32 is connected to the input terminal D and the output terminal, the output terminal of the FF 35 is connected to the clock terminal T, and the other input terminal of the AND gate 32 is connected to the output terminal Q.

The operation of the input unit 1 and the phase control unit 2 will be described with reference to a time chart shown in FIG. In FIG.
_VA is a half-wave voltage input from the power supply unit 4 to the base of the transistor 17, and S is a signal indicating opening and closing of the drive contact 5. When transistor 17 is off, point a (transistor 17
The voltage at the connection point between the collector and the resistor 16) is almost the control power
It is equal to the voltage of Vcc, but drops to almost 0 when the transistor 17 is turned on, and the square wave voltage V is 180 ° out of phase with the half wave voltage _VA.
a. The capacitor 23 is charged with the square-wave voltage Va via the resistor 19 and discharged via the resistor 21, so that the voltage at the point b obtained by inverting the voltage of the capacitor 23 by the inverter 24 becomes a square-wave voltage Vb. The rising and falling phases of the wave voltage Vb are determined by the resistors 19 and 21 and the capacitor 23, and can be adjusted by making the resistors 19 and 21 variable. The voltage Vc at the point C obtained by differentiating the voltage Vb is the voltage Vb
Is generated as a narrow pulse wave at the time of each rise. The voltage Vd at the point d obtained by inverting the voltage at the point b by the inverter 28 and differentiating it is generated as a narrow pulse wave when the voltage Vb falls. When the output Ve of the output terminal of the FF 36 is at a low level (hereinafter abbreviated as L), the pulse wave voltage Vc is output from the AND gate 32, O
After passing through the R gate 34, the clock terminal T
To enter. Further, the pulse wave voltage Vd passes through the AND gate 33 and the OR gate 34 when the output Ve at the output terminal of the FF 36 is at a high level (hereinafter abbreviated as H), and is input to the clock terminal T of the FF 35 as the voltage Vf.

When the output terminal of FF36 is H and the drive contact 5 is off, FF35
Is low, the output of the two FFs 35 and 36 does not fluctuate and the output of the output terminal Q of the FF 35 is low. At this time, when the drive contact 5 is turned on, the input terminal D of the FF35 changes to H. Therefore, when the voltage Vf of the clock terminal T rises, the output of the FF35 is inverted, the output terminal changes to L, and the output terminal Q changes to H. Turn output unit 4
To close the main contact 6. Here, when the drive contact 5 is turned off, the input terminal D of the FF35 changes to L, so that the output of the FF35 is inverted at the rise of the voltage Vf following the clock terminal T, the output of the output terminal Q of the FF35 changes to L, and the output unit 4 The main contact 6 is opened via the switch. At this time, the output of the output terminal of the FF35 turns to H, and this H
Is input to the clock terminal T of the FF36, the output Ve of the output terminal of the FF36 changes to L. The output Ve of this output terminal is L
The voltage Vf at the clock end T of the FF35 becomes a pulse wave voltage
Since it changes to Vc, the output of the output terminal Q of the FF35 switches between the positive and negative phases of the output terminal Q of the FF35 every time the drive contact 5 is turned on / off. It has been stated that the phase of the square wave voltage Vb can be adjusted. However, by adjusting the phase of the square wave voltage Vb, the phase of both pulse waves Vc and Vd can be adjusted and the switching phase of the main contact 6 can be optimized. Can be.

In the above-described embodiment, the first operation of the switch has a positive phase for closing and opening the main contact, and the second operation has a negative phase for closing and opening the main contact. In the second operation, the closing and opening of the main contact are made positive and negative, respectively, and the positive and negative phases can be changed for each opening and closing.

〔The invention's effect〕

As described above, according to the present invention, the opening / closing phase of the main contact is set, and the opening / closing phase is switched each time the main contact is opened / closed since the phase control unit is provided for switching the opening / closing phase between the positive phase and the negative phase for each opening / closing. Switching between the positive phase and the negative phase prevents the transfer phenomenon of the contact. Further, the closed phase can be adjusted to the point where the contact bounce is the smallest, and from this point the contact life can be prolonged.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a switch driving circuit according to the present invention, FIG. 2 is a connection diagram showing an example of an input section and a phase control section in FIG. 1, and FIG. 6 is a time chart showing a waveform of a point. 1: input unit, 2: phase control unit, 11: square wave generation circuit, 12: integration circuit, 13, 14: differentiation circuit, 35, 36: D-type flip-flop.

Claims (2)

(57) [Claims] In a switch drive circuit for opening and closing a main contact by turning on and off a drive contact, an open / close phase of the main contact is set, and the open / close phase is switched between a positive phase and a negative phase for each open / close operation. A phase control unit is provided. The phase control unit generates a square wave voltage that generates a square wave voltage having a 180 ° phase difference from a half-wave voltage obtained by rectifying a power supply to be opened and closed by the switch, and a square wave generation circuit that generates the square wave voltage. An integrating circuit that integrates the obtained square wave voltage, a first differentiating circuit that differentiates the output of the integrating circuit through an inverting circuit, and a first differential circuit that differentiates the voltage obtained by inverting the output of the integrating circuit through an inverting circuit. A second differential circuit, and a flip-flop that uses the outputs of the first and second differential circuits as a clock input and switches the output level each time the drive contact is turned on and off. , The second derivative Driving circuit of the switch, characterized in that the logical product to the drive output of the output. 2. The switch driving circuit according to claim 1, wherein the integrating circuit comprises a capacitor and a resistor, and the resistor is a variable resistor having a resistance value capable of changing its output phase sufficiently. And a switch drive circuit.