JPH08171842A - Relay controlling circuit - Google Patents

Abstract

PURPOSE: To extend the life of a relay circuit whose on/off frequency is high by making a relay controlling circuit select the relay control signal sending timing randomly to the phase of an a.c. electric power source. CONSTITUTION: An initial setting is carried out, and as a result, a relay contact point 4a of a relay circuit 4 is set in open state. Then, a time series data of a half cycle of an a.c. electric power source is detected. In the detection, signals sent out to a contact point of the collector terminal of a photo Tr 8b in the output side of a photo coupler circuit 8 and a load resistor 10 are conformed to the zero-crossing timing of a.c. electric power and becomes H. The gap between the spike-like pulse signals is detected and the time series data of obtained half cycle of a.c. power source is stored in a register 13. Next, a prescribed number of phases of phase dividing points are computed and these phases are stored in a register 15. When a demand to send a control signal from a microcomputer 5, the computer 5 generates random number and randomly selects one of the phase dividing points. The timing to sent a relay control signal from the phase dividing point is computed and stored in the register 15 and a relay control signal is sent at the timing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a relay control circuit capable of extending the life of a relay circuit by preventing deterioration of relay contacts of the relay circuit. In particular, the present invention relates to a relay control circuit for a heater such as a bread maker, which is an electric device, and a motor such as a motor, which is frequently turned on and off.

[0002]

2. Description of the Related Art When an inductance load or a large current load is opened / closed by a relay circuit which is frequently used for turning on / off an AC power supply of an electric device, particularly a relay circuit having a mechanical contact, the contact between both electrodes Gas discharge generated in the gap between the electrodes due to the potential difference, such as glow discharge or arc discharge, causes contact welding or contact failure, which is a cause of shortening the life of the relay contact. Further, also in a relay control circuit such as a microcomputer or a sequencer for controlling the opening / closing of such a relay circuit, the timing for controlling the opening / closing of the relay circuit should be a necessary operation required for the electric device by a program. It has only been decided to do so. That is, the life of the relay circuit is not taken into consideration.

[0003]

Therefore, when turning on / off the AC power supply of an electric device, the ON / OFF timing of a relay circuit for executing the ON / OFF control is set so that the phase of the input voltage wave of the AC power supply is just a zero cross point. It was considered to drive the relay control circuit to turn on / off when passing. It has been considered that in this way, no gas discharge is generated in the electrode gap of the relay circuit which is turned on / off, and therefore the life is not shortened.

The conventional relay control circuit is constructed as described above. However, in reality, the relay circuit is turned on /
In many cases, the off timing does not match the zero cross point of the phase of the AC voltage wave. The reason for this will be described below. In order to match the on / off timing of a conventional relay circuit with the zero cross point, first, the phase of an AC voltage wave is input from an AC power supply circuit from an input port in the control unit or the like to detect the zero cross point, and the control unit The relay circuit is turned on / off according to the zero cross point time.
Send the drive signal to turn off to the circuit that relays. However, there is a mechanical time delay of about several ms between sending a drive signal for turning on / off to the relay circuit and actually turning on / off the relay circuit (even if relay circuits with the same specifications have The time delays are not the same, each with its own value). Half cycle of voltage phase is 8.3 ~ 1
Since it is 0 ms (60 to 50 cycles), the on / off timing deviates from the zero cross point and the probability of shortening the life increases. The time delay is a constant value that is unique to each relay circuit and is a value that does not change with each ON / OFF. Therefore, as described above, in the case of a control system that detects a zero cross point and sends a drive signal for turning on / off the relay circuit in accordance with it, the timing phase at which the relay circuit is actually turned on / off is It is always turned on / off at the same timing phase position. Therefore, if the timing phase is away from the zero cross point, it is always turned on / off at the same inconvenient position, and the life is likely to be shortened. As described above, it is a problem that the relay circuit is always turned on / off at the same timing phase position so that the life is easily shortened.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is an AC power source phase position with a constant sending time for generating and sending a relay control signal for driving a relay circuit. It is an object of the present invention to provide a relay control circuit that can prolong the life of the relay circuit by making it random so as not to cause the above problem.

The relay control circuit according to the present invention has a relay circuit for turning on / off the AC power supply load, and a zero cross point detecting means for detecting the phase of the AC power supply and detecting the zero cross point time of the phase. In the relay control circuit for turning on / off the relay circuit based on the time, the zero cross point detecting means divides the phase between the zero cross points by an integer value of 2 or more and passes through the phase division points. A phase dividing point calculating means for calculating each time and a relay control signal for turning on / off the relay circuit are randomly generated and generated in the relay circuit. And a relay control signal transmitting means for transmitting.

[0007]

In the relay control circuit according to the present invention, the phase division point calculation means detects the zero cross points of the AC power supply input phase before the relay control and divides the phase between the zero cross points by an integer of 2 or more, When there is a relay control signal for instructing switching from ON to OFF or from OFF to ON of the relay contact of the relay circuit, calculate each time passing through those phase division points and store them By the control signal sending means,
For randomly selecting one of the time groups passing through the phase division point, generating a relay control signal at the randomly selected time, and for switching the relay circuit from on to off or from off to on By sending the relay circuit control signal and driving the opening and closing of the relay contacts of the relay circuit, the timing of opening and closing the relay contacts is limited within a certain phase angle range of the AC power supply for each relay circuit. By avoiding, the opening and closing of the relay contact is driven randomly at any of the phase angles, and the gas discharge generation at the relay contact due to the opening and closing of the relay contact is dispersed over time, and averaged to create a relay circuit. Extend the life of.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an electric circuit diagram showing the configuration of the relay control circuit of this embodiment. In the figure, 1 and 2 are terminals connected to an AC power source, and 3 is an AC load. As the AC load, for example, a load and a number of fluctuations due to ON / OFF of a heater or a motor of a bread maker which is an electric device are large. Four
Is a relay circuit and has a relay contact 4a that is opened and closed and an exciting coil 4b. One end of the exciting coil 4b is connected to the ground, and the other end is connected to the output port 6 of the microcomputer 5 which is the system controller of the electric device. Reference numeral 7 is a rectifying circuit for rectifying the AC voltage across the relay contact 4a, 8 is a photocoupler circuit, 8a is a light emitting diode on the input side of the photocoupler circuit 8, and 8b is a phototransistor on the output side of the photocoupler circuit 8. The series circuit of the light emitting diode 8a and the current limiting resistor 9 is connected to the DC output terminal of the rectifier circuit 7 that outputs the rectified DC voltage. Reference numeral 10 is a load resistance, which is connected between the collector terminal of the phototransistor 8b on the output side of the photocoupler circuit 8 and the DC power supply of the microcomputer 5. The connection point between the load resistor 10 and the collector terminal of the phototransistor 8b is connected to the input port 11 of the microcomputer 5. A RAM 12 is provided in the microcomputer 5, and the RAM 12
Are set to registers 13, 14, and 15. The register 13 stores time data indicating a half cycle of the AC power source, and the register 14 stores a predetermined number of phase division point data of the transmission timing of the relay control signal for controlling the relay circuit 4. Further, the register 15 stores the value of the randomly selected time when the relay control signal is transmitted to the relay circuit 4. The microcomputer 5 is also provided with a ROM (not shown) and the like.
A program for generation processing of relay control signal transmission time data shown in is stored. In addition, it has a random number generator for randomly selecting the phase division points.

Next, the relay control signal transmission time data generation processing operation of this relay control circuit will be described with reference to the flow chart of FIG. 2 and the timing chart of FIG. First, in step S1, initial settings are made and the input / output ports and registers of the microcomputer 5 are reset. As a result, the relay contact 4a of the relay circuit 4
Is initially set to the open state. Next, step S2
Then, the time data of the half cycle of the AC power supply is detected. The half cycle time data of the AC power supply is detected by detecting that the signal output to the connection point between the collector terminal of the phototransistor 8b on the output side of the photocoupler circuit 8 and the load resistor 10 is at the zero-cross timing of the AC power supply. Since it is a spike-shaped pulse signal as shown in (b) of FIG. 3 which becomes "H" level, it is obtained by detecting the interval of this spike-shaped pulse signal. As a result, the obtained half cycle time data of the AC power supply is stored in the register 13 in step S3.

Next, in step S4, the phases of a predetermined number of phase division points are calculated. 6 in the example shown in FIG.
In other words, the phase angle is divided into 30 degrees. It stores them in the phase register 15. Here, a request for sending a relay control signal for driving a relay circuit on / off of a heater or a motor is issued in association with a bread making process program from a microcomputer 5 which is a system controller of an electric device such as a bread maker. If there is (step S
5) Proceeding to the next step S6, a random number is generated by a random number generating section or a random number generating program provided in the microcomputer 5 which is the control section, and one of the phases of the phase dividing points stored in the register 15 is set. Select at random. Next, in step S7, the time that matches the selected phase is calculated, the time is stored, compared with a timer clock, and a relay control signal is sent at that time. FIG.
(D) shows the case where the selected phase time is t5.

[0011]

Therefore, in the conventional relay control circuit, the AC power supply phase of the relay contact ON / OFF of each of the relay circuits is opened and closed at the same timing phase, whereas the relay control circuit of the present invention performs relay control. Since the signal transmission timing is performed randomly with respect to the AC power supply phase, the open / close operation time of the relay contact with respect to the AC power supply phase is not constant, and it is locked by contact welding or contact transfer due to gas discharge occurring between the relay contacts. The ON phenomenon is dispersed to reduce the probability of gas discharge, which has the effect of extending the life of the relay circuit.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a relay control circuit according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a relay control signal transmission time data generation processing operation of a relay control circuit according to an embodiment of the present invention.

3 is a timing chart for explaining a processing operation of the relay control circuit of FIG. 2 according to an embodiment of the present invention.

[Explanation of symbols]

3 AC load 4 Relay circuit 4a Relay circuit 4b Excitation coil 5 Microcomputer (Phase division point calculation means, relay control signal transmission means) 6 Output port 8 Photocoupler circuit 11 Input port 12 RAM A1 Relay contact

Claims (1)

[Claims] 1. A relay circuit for turning on / off an AC power supply load, and a zero cross point detecting means for detecting a phase of the AC power supply and detecting a zero cross point time of the phase, and based on the time. In a relay control circuit for driving a relay circuit on / off, a phase for dividing the phase between the zero cross points by an integer value of 2 or more by the zero cross point detection means and calculating each time passing through those phase division points. Split point calculation means and relay control signal transmission for randomly generating and transmitting to the relay circuit any one of times when the relay control signal for driving the relay circuit on / off is passed. And a relay control circuit.