JP3703959B2 - Relay control circuit - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a relay control circuit for driving a relay contact by zero point control while detecting a zero point of an AC power supply with a microcomputer.
[0002]
[Prior art]
In general, a technique for controlling the zero point of the load of the AC power source with the contact of the relay is known, for example, as shown in Japanese Patent Publication No. 3-3325, and the contact point of the relay is controlled by the microcomputer as shown in FIG. It was something to do. That is, 1 is an AC power supply, 2 is a DC power supply, 3 is a load, 4 is a contact of a relay provided in series with the load 3, 5 is a power supply synchronization generating means for generating a signal synchronized with the zero point of the AC power supply 1, Opening / closing phase detecting means for detecting the phase at which the contact 4 of the relay is opened / closed, 7 is a control circuit section comprising a microcomputer, and 8 is a driving means for driving the relay by an output signal from the control section 7.
[0003]
Here, the power supply synchronizing signal generating means 5 is composed of a diode bridge 9, resistors 10 and 11, and a photocoupler 12, and the open / close phase detecting means 6 is composed of a diode bridge 13, resistors 14 and 15 and a photocoupler 16. The relay driving means 8 includes a relay coil 17, a transistor 18, a diode 19, and a resistor 20.
[0004]
The control unit 7 includes a CPU, a ROM, a RAM input / output port, and the like, and inputs a power supply synchronization signal from the power supply synchronization signal generating unit 5 and an open / close signal from the open / close phase detection unit 6 into the ROM. A time difference measuring means (not shown) for measuring the time difference and a driving phase determining means (not shown) for determining the driving phase of the relay based on a measurement signal from the time difference measuring means are provided.
[0005]
An operation example in which the relay is simply controlled and the contact is closed will be described with reference to the flowchart shown in FIG.
[0006]
When the contact 4 of the relay is closed, the measurement of the time (phase) t0 is started when the falling edge of the power supply synchronization signal is input (step 1), and the time t0 stored in the RAM in step 2 is the time ton. The relay drive signal is output with the matched phase. When the relay contact is closed, the fall of the open / close signal is input in step 3, and the measurement of time t0 is stopped. Only when the time t0 and the period T1 of the power supply synchronizing signal are not equal, the difference between the time t0 and the period T1 is added to the time ton, and the value is stored in the RAM as a new time ton (step 4).
[0007]
When the contact 4 is opened, when the rising edge of the power supply synchronizing signal is input, the measurement of the time t0 is started (step 5), and the relay drive signal has a phase that coincides with the time toff stored in the RAM. Is stopped (step 6). Thus, the contact of the relay is controlled at the zero point of the AC power supply, and the on control is performed when the zero point synchronization signal falls and the off control is performed when the zero point synchronization signal rises.
[0008]
[Problems to be solved by the invention]
It is known that the contact life is extended when the contact is opened and closed near the zero point of the AC power supply as in the conventional example. However, since a small relay may rebound immediately after the contact is opened, if the relay contact is opened and closed near the zero point, a fatal arc discharge may occur due to rebound immediately after the break and the contact life may be shortened remarkably. is there.
[0009]
This rebound is a transient response that causes the open contact to reclose (contact is turned on again even if there is no relay coil signal) due to the bouncing phenomenon caused by the armature backstop collision when the contact of the relay is released. (This phenomenon is expressed as rebound below.) The influence of this on the contact life is particularly serious when a contact zero-point control method as in the conventional example is adopted, and a safety problem remains in a device that controls a heater load or the like.
[0010]
In other words, when rebound occurs, strong inter-contact arc discharge occurs during the half cycle of AC power supply immediately after the zero point control of the contact, and if it continues, rocking due to welding or transition of contact metal occurs due to abnormal heating of the contact surface Had.
[0011]
The present invention is to solve such a problem in advance, and provides a relay control circuit that detects a rebound occurrence and can perform a maintenance alarm and a safety stop before contact welding (including locking) occurs. It is for the purpose.
[0012]
[Means for Solving the Problems]
In order to solve this problem, there is provided a relay control circuit controlled by a load driven by an AC power source and a contact of the relay, a zero point detecting unit for detecting a zero point of the AC power source, and the zero point detecting unit Control means for opening and closing the contact of the relay near the zero point of the AC power source based on the signal of the contact, contact opening and closing detection means for detecting the opening and closing of the contact of the relay, and immediately after the opening of the contact of the relay The relay control circuit includes a rebound detecting means for detecting a rebound generated during a half cycle.
[0013]
According to this configuration, when driving the relay, it is possible to detect rebound that occurs immediately after the opening of the contact, so if a predetermined number of occurrences occur, a warning signal is issued, and if it occurs continuously, the contact is welded ( By adding a function of forcibly stopping the driving of the relay before locking (including locking), safety can be ensured and the object of the present invention can be achieved.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
According to a first aspect of the present invention, the control means, the contact with one of the signal of the rectangular wave rising signal or falling signal is the output signal of the power-supply sync generating means synchronized to the zero potential of an AC power source It has a processing switching software algorithm that performs zero-point calculation control of contacts as an open / close detection input and detects rebound with the other signal. According to this configuration, rebound detection can always be detected every time the relay contacts are opened or closed. It is what has.
[0015]
The invention according to claim 2 of the present invention, the control means, when the predetermined number of times counted number of occurrences of the rebound, Rutotomoni drives the alarm means for abnormality notification relay, the operation of the relay if the continued According to such a configuration, the problem of contact welding due to rebound or locking phenomenon that hinders the extension of the contact life of the relay can be avoided , and the contact life can be extended .
[0018]
(Embodiment 1)
FIG. 1 shows the configuration of a relay control circuit according to the first embodiment of the present invention. In FIG. 1, 1 is an AC power source, 2 is a DC power source for circuit driving, and 3 is a load connected to the AC power source 1. 4 is a relay contact for controlling the load 3, 5 is a zero point detection means for generating a signal synchronized with the zero point of the AC power supply, and 6 is also used as a contact open / close detection means for detecting the phase at which the contact 4 of the relay 17 is opened and closed. It is a rebound detection means. Reference numeral 7 denotes a control unit composed of a microcomputer, and 8 denotes relay drive means for driving the relay 17 by an output signal from the control unit 7.
[0019]
Here, the zero point detection means 5 includes a transistor 9, a base-emitter protection diode 10 of the transistor, a base resistor 11, and a collector resistor 12. The rebound detecting means 6 also serving as the contact opening / closing detecting means includes a transistor 13, a base-emitter protective diode 14, a base resistor 15, and a collector resistor 16. Further, the control unit 7 is constituted by a microcomputer, and the rebound detection is also used as the zero point detection input a of the zero point detection means 5 and the contact opening / closing detection input obtained from the rebound detection means 6 which is also used as the contact opening / closing detection means. It has an input b (herein expressed as a contact open / close detection input b) and an alarm output d that issues an alarm when rebound occurs a predetermined number of times. Reference numeral 21 denotes the alarm means, 22 an LED display element for alarm, and 23 a current limiting resistor. The relay driving means 8 is driven by the relay driving output c, and includes a relay 17, a transistor 18, a base resistor 19, and a back electromotive force absorption diode 20 of the relay 17. VR represents the voltage across the contact 4 of the relay 17.
[0020]
The operation will be described below with reference to the timing chart of FIG. 2 based on the configuration of FIG. In order to distinguish from the rebound detection mode, which will be described later, FIG. 2 illustrates the operation mode for taking in the contact opening / closing detection input b.
[0021]
Now, when the contact 4 is in the ON state (the voltage VR between the contact points of the relay has no signal), T1 from the rising signal (A) point of the zero detection input a obtained from the waveform of the AC power supply 1 by the zero detection means 5 The relay drive means 8 is turned off with the relay drive output c measured and calculated by the control unit 7 later. The relay 17 has the coil signal cut off at this point (B), and the contact 4 of the relay 17 is turned OFF at the point (c) after T2. Here, the contact opening / closing detection input b is taken into the microcomputer of the control unit 7, T3 up to the falling point (d) of the zero point detection input a of the AC power supply 1 is measured, and is reflected in the next calculation control.
[0022]
Next, the capture mode of the rebound detection input b will be described with reference to the timing chart of FIG. The circuit has a contact opening / closing detection input b which is also used as a contact opening / closing detection input 6 which is also used as a contact opening / closing means 6 (represented as a rebound detection input b here). Now, when the contact point 4 is in the ON state, from the falling signal (e) point of the zero point detection input a obtained from the waveform of the AC power source 1 by the zero point detection means 5, T2 measured by the control unit 7 last time after T4 and The relay drive means 8 is turned off with the same relay drive output c. In the relay 17, the coil signal is cut off at this point (f), and the contact 4 of the relay 17 is turned off at the point (g) after T5.
[0023]
Here, the difference from the contact open / close detection input b capture mode is that no signal is output to the rebound detection input b between this point (g) and the rising signal (h) point of the zero detection input a of the AC power supply 1. is there. This is because the zero point detection input a is at the LOW level and the contact open / close detection input b is not captured on the circuit. In normal operation, no signal is received after the rebound detection input b. However, as described above, the rebound phenomenon is caused by bouncing caused by the collision of the contact point once turned off to the back stop of the armature. ) The point at which the contact 4 turned off after T7 from the point is closed again (expression that the contact is turned on again by rebound) is the (re) point.
[0024]
Since the T7 is a mechanical armature collision rebound, the structural influence is strong and may be within the range of T6. In this case, since the voltage of the AC power supply 1 is also close to the zero point, there is no influence of contact deterioration, so it does not matter if it cannot be detected. However, if the AC power supply 1 is re-closed at a point slightly beyond the zero point (H), the arc discharge is stopped from the arc generation voltage VA point (generally said to be generated from about 15 V in normal air). During T8 up to the point (V) of the voltage VB, a strong arc discharge occurs between the contacts. If rebound occurs at a point where the zero point of the AC power source 1 is exceeded, the rebound detection input b is detected at the (re) point and is taken into the microcomputer of the control unit 7.
[0025]
Next, the processing algorithm of the signal taken into the microcomputer of the control unit 7 will be described with reference to FIG.
[0026]
FIG. 4 is an operation flowchart in the microcomputer in which the contact open / close detection input and the rebound detection input can be switched in the signal processing algorithm.
[0027]
(1) is a part for switching to the contact opening / closing detection input mode if there is a rising signal in the negative half cycle zero point detection input of the AC power supply, and to the rebound detection input mode if there is no rising signal. Therefore, the zero detection input a described with reference to FIG. 2 enters the contact open / close detection input mode from the rise of the zero detection input (YES in the flowchart).
[0028]
(2) shows the switching part of the contact operation mode (ON or OFF). Here, the operation mode from the ON state of the contact, which is the above condition, corresponds to the part (3), and constitutes the T1 timer shown in FIG. (4) is a part for measuring a time T2 from when the relay drive output c is turned off until the contact is opened. The above flow is the processing part of the contact open / close detection input mode.
[0029]
(5) is the processing part of the mode in which the contact is turned from OFF to ON, and is not related to the current rebound, so the explanation is omitted.
[0030]
Next, the rebound detection input mode of the falling part of the positive half cycle of the AC power supply 1 (NO at the zero detection input a) will be described. (6) shows a contact operation switching (turning ON or OFF) part. (7) is a part for generating T4 by the driving timer set with the previous measurement DATA (T2) from the relay driving output c described in FIG.
[0031]
(8) is a part for detecting whether the zero point detection input a of the AC power source 1 is in a high level state. (9) is a part for discriminating whether or not there is a timer unit for determining a rebound detection period and a subsequent rebound detection input b based on the high level state. (10) shows a counter unit for counting the number of occurrences of rebound, and an alarm function unit for turning on the alarm output b when a predetermined count is reached. Further, when the rebound continues and another counter unit reaches a predetermined count, the relay drive output c is turned OFF, and the relay indicates a safety stop function unit that is forcibly stopped.
[0032]
(11) is an operation flow for turning on the contact of the relay and is not related to the rebound, so the description is omitted.
[0033]
In this embodiment, the negative half cycle of the AC power supply is used as contact open / close detection and the positive half cycle is used as rebound detection. However, the negative half cycle is used as rebound detection, and the positive half cycle is used as contact open / close detection. The effect is obtained. The circuit configuration is shown in FIG. 6 is the contact open / close detecting means shown in FIG. 1, but it is well known that 24 transistors can be realized by adopting a PNP type (of course, FIGS. 2 to 4 are also changed). Reference numeral 25 denotes a protective diode, 26 denotes a base resistance, and 27 denotes a collector resistance.
[0034]
In addition, an alarm means is provided to display an alarm, but by connecting an element that can be isolated (such as a relay) such as a photocoupler to this part, information can be transmitted to the future security system, and maintenance alarms can be used. Useful effects are obtained.
[0035]
【The invention's effect】
The relay control circuit obtained as described above has a fatal contact deterioration (contact point) in a system in which contact reclosing due to rebound from the armature backstop when the relay contact point is OFF is controlled by the zero point of the contact point. (Welding and locking) is a problem, but by providing the rebound detection means, an effect of avoiding this can be obtained.
[0036]
Furthermore, the present invention does not provide this rebound detection means specially, but also provides an algorithm for switching by means of software processing, which is shared with the circuit of the contact open / close detection means essential for zero point control. The effect that it can be realized is obtained.
[0037]
Yet another effect is to provide a software process that counts the results obtained by the rebound detection means, alerting the relay to abnormalities, and if further continued, the contact stops operating before welding or locking occurs. An effective effect is also obtained from the aspect of ensuring safety.
[Brief description of the drawings]
FIG. 1 is a circuit configuration diagram according to a first embodiment of the present invention. FIG. 2 is a timing chart for explaining a contact opening / closing operation according to the embodiment. FIG. 3 is a timing chart for explaining a rebound detection operation according to the embodiment. FIG. 4 is a flowchart showing a contact opening / closing operation and a rebound detection switching software algorithm according to the embodiment. FIG. 5 reverses rising and falling of a zero detection input signal obtained from the AC power supply zero synchronization signal of FIGS. Circuit diagram of the used example [FIG. 6] Circuit diagram of the conventional example [FIG. 7] Operation flowchart of the conventional example [Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 AC power source 2 Circuit drive DC power source 3 Load 4 Relay contact 5 Zero point detection means 6 Rebound detection means 7 Control unit 8 Relay drive means 9 Transistor 10 Protection diode 11 Base resistance 12 Collector resistance 13 Rebound detection means transistor 14 Protection Diode 15 Base resistance 16 Collector resistance 17 Relay coil 18 Transistor 19 Base resistance 20 Back electromotive force absorption diode 21 Alarm means 22 LED display element 23 Current limiting resistance of LED display element

Claims (2)

A load driven by an AC power supply, a relay control circuit for controlling energization of the load at a contact of the relay, a power supply synchronization generating means for generating a rectangular wave synchronized with a zero point of the AC power supply, and the power supply phenomenon and control means for opening and closing the contacts of the relay based on the signal of the synchronous generator at the zero point vicinity of the alternating current power supply, the contact and detects the opening and closing of the contacts of the relay is re-closed immediately after separable (hereinafter, Rebound detection means for detecting ) ,
A relay control circuit in which the control means switches between contact opening / closing detection and rebound detection based on a rising signal or a falling signal of the power supply synchronization generating means . Control means, based on a detection signal from the rebound detection means and for counting the number of occurrences of rebound, the control circuit of the relay according to claim 1, wherein the driving the alarm means upon a predetermined number of times counted.

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