JP2006294539A - Relay control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a relay control device user-friendly for a user by extending the service life of a relay by suppressing heat generation of a relay contact even when commercial A.C. power is failed and by bringing it back to a state before the power failure after restoration of the commercial A.C. power. <P>SOLUTION: This relay control device is provided with: a relay 8 having a relay coil 8a and a relay contact 8b; a relay drive unit 6 having a microcomputer 6a and a first transistor 6b; a voltage monitor 5 having a diode 5a, a first resistor 5b and a second resistor 5c; and a relay holding device 7 having a second transistor 7b and a third resistor 7a. The relay control device is so structured that, when it is detected by the voltage monitor 5 that the voltage of the commercial A.C. power 1 is set below a certain value in feeding the commercial A.C. power 1, the control of the relay 8 executed through the relay drive unit 6 is changed over to the control executed through the relay holding device 7. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a relay control device for a device having a relay.

  Conventionally, the relay control apparatus of the apparatus which has a relay was comprised as shown in FIG. In FIG. 3, when the first transistor 6b connected to the output terminal B of the microcomputer (hereinafter referred to as a microcomputer) 6a is turned on, a current is passed through the relay coil 8a and the relay contact 8b is closed. At this time, a relay coil current required for driving the relay contact 8b is allowed to flow through the relay coil 8a. Here, the power source of the microcomputer 6a and the relay coil 8a is driven by the output DC power source of the switching power source 4 having the diode 2 and the capacitor 4a connected to the commercial AC power source 1.

Alternatively, after a necessary current is supplied to the relay coil 8a and the relay contact 8b is closed, the relay drive current is reduced to a holding current at which the relay contact 8b is not opened (see, for example, Patent Document 1).
JP-A-2-244532

  However, in such a conventional configuration, a current necessary for driving the relay contact 8b (hereinafter, this current is referred to as a rated current) flows through the relay coil 8a of the relay 8, and the commercial AC power source 1 has caused a power failure. In this case, once the relay contact 8b is turned on, the load of the DC power source driven by the relay contact 8b is heavier than that of the holding current method in which the current is decreased and then the relay contact 8b is kept closed. Will fall quickly. When the relay contact 8b is driven with a current required for driving, and once the relay contact 8b is closed, the current is decreased and the holding current method is maintained to keep the relay contact 8b closed. Since the current flowing through the relay coil 8a is small, the DC power supply voltage is lowered for a long time. However, since the AC power supply is normally supplied, when the contact is pulled by the holding current, the force for pulling the contact is weak. There is a problem that the pressure between the contacts is weakened, and therefore the resistance between the contacts may be increased, and the heat generated at the relay contact 8b is increased.

  The present invention solves the above-described conventional problems, and even when the commercial AC power supply fails, the relay contact heat generation is suppressed, the life of the relay is lengthened, and the state before the power failure is restored after the commercial AC power supply is restored. The purpose is to obtain a relay control device that is convenient for the user.

  In order to achieve the above object, the relay control device of the present invention includes a relay having a relay coil and a relay contact, the relay contact being connected to a load, a microcomputer, and a first transistor. A relay driving device in which a collector of a first transistor is connected to one end of the relay coil; a diode, a first resistor, and a second resistor; and a connection point between the first resistor and the second resistor A voltage monitoring device connected to a microcomputer, and a relay holding device having a second transistor and a third resistor, one end of the third resistor being connected to one end of the relay coil together with a collector of the first transistor The microcomputer is configured to ensure that the voltage of the commercial AC power source is not more than a predetermined value by the voltage monitoring device when the commercial AC power source is energized. Upon detecting, in which the energization of the relay coil which has gone through the relay driving apparatus to switch to perform via the relay holding device.

  As a result, when supplying power to the commercial AC power supply, it is possible to prevent the contact from being damaged by increasing the pressure of the relay contact, and to extend the voltage drop time of the DC power supply during a power failure. After a power failure recovery, it is possible to return to the state before the power failure and provide a user-friendly relay control device.

  The relay control device according to the present invention closes the relay contact with the current necessary for driving the relay when the power is supplied from the AC power source, and keeps the relay driving to the holding current when the AC power source fails. By reducing the current of the relay drive, the circuit can maintain the operating state for a longer time until the power failure is resolved at the time of power failure.

  Further, when the time during which the circuit keeps operating in the power outage need not be changed, the capacity of the capacitor constituting the DC power supply can be reduced. As a result, it is possible to reduce the size of the component and reduce the price.

  Also, when alternating current flows through the relay contacts, there is no current flowing between the relay contacts at the time of a power failure, so the contact pressure is lowered, and at the time of a non-power failure, the relay contact pressure is increased to reduce damage to the relay contacts. It becomes possible.

  According to a first aspect of the present invention, there is provided a relay having a relay coil and a relay contact, the relay contact being connected to a load, a microcomputer and a first transistor, and a collector of the first transistor at one end of the relay coil. A connected relay driving device; a voltage monitoring device having a diode, a first resistor, and a second resistor; and a connection point of the first resistor and the second resistor connected to the microcomputer; And a relay holding device having one end of the third resistor connected to one end of the relay coil together with a collector of the first transistor, and the microcomputer includes a commercial AC power source. When the voltage monitoring device detects that the voltage of the commercial AC power source has become a certain value or less during energization of the power supply, it is performed via the relay driving device. By switching so that the relay coil is energized via the relay holding device, the relay contact is kept at a high level and when the commercial AC power supply fails, the relay holding device By reducing the current flowing through the power supply and reducing the load current of the DC power supply, it is possible to maintain the operating state of the circuit for a longer period of time against a power failure, and to maintain the operating state for the same time with a small capacity capacitor be able to.

  According to a second aspect, in the first aspect, when the voltage of the commercial AC power supply returns to a predetermined value or more, the microcomputer energizes the relay coil, which has been performed via the relay holding device, via the relay driving device. Therefore, when the power failure is resolved, it is possible to return to the state before the power failure again and increase the press of the relay contact.

  In the third aspect of the invention, the other end of the relay coil is connected to a switching power supply output higher than the voltage of the switching power supply output for the microcomputer, so that the pressing of the relay contact can be further increased.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, the thing of the same structure as a prior art example attaches | subjects the same code | symbol, and abbreviate | omits description. Further, the present invention is not limited by this embodiment.

(Embodiment 1)
FIG. 1 is a circuit diagram of a relay control device according to the first embodiment of the present invention.

  In FIG. 1, a first diode 2 and a first capacitor 3 are connected in series at both ends of an AC power source 1. A switching power supply 4 is configured between both terminals of the first capacitor 3 using the first capacitor 3 as an input capacitor. The second capacitor 4 a is an output capacitor of the switching power supply 4.

  The voltage monitoring device 5 has a second diode 5a, a first resistor 5b, and a second resistor 5c connected in series to both ends of the commercial AC power supply 1, and obtains the output from the connection point of the two resistors. Yes.

  The relay driving device 6 includes a microcomputer 6 a and a first transistor 6 b, and the microcomputer 6 a is operated by the switching power supply 4. The voltage information of the commercial AC power supply 1 from the voltage monitoring device 5 is input to the input terminal A of the microcomputer 6a, and the microcomputer 6a reads the voltage information of the commercial AC power supply 1 and determines the supply state of the commercial AC power supply 1. The first transistor 6b is turned on / off.

  The microcomputer 6a detects the voltage of the commercial AC power supply 1 by setting the resistance values of the first resistor 5b and the second resistor 5c of the voltage monitoring device 5 appropriately.

  The emitter of the first transistor 6b is connected to the negative terminal of the switching power supply 4, and the base of the first transistor 6b is connected to the output terminal B of the microcomputer 6a.

  The relay holding device 7 includes a second transistor 7b whose base is connected to the output terminal C of the microcomputer 6a, and a third resistor 7a connected to the collector of the second transistor 7b. The emitter of the second transistor 7 b is connected to the negative terminal of the switching power supply 4. The second transistor 7b is ON / OFF controlled according to voltage information at the input A terminal of the microcomputer 6a.

  One end of the relay coil 8a of the relay 8 is connected to the collector of the first transistor 6b and the other end of the resistor 7a. The other end of the relay coil 8 a is connected to the plus terminal of the switching power supply 4. The relay contact 8b is connected to a load (not shown). The load is driven by the commercial AC power source 1.

  The operation of the above configuration will be described.

  When electric power is supplied from the commercial AC power supply 1, in order to drive the load connected to the relay contact 8b in accordance with the program of the microcomputer 6a, the output terminal B of the microcomputer 6a is set high so that the relay coil 8a is driven, the relay contact 8b is closed, and the load is driven. In this case, the current flowing through the relay coil 8a is determined by only the DC resistance of the relay coil 8a.

  The relay 8 driven by the relay driving device 6 is driven by the rated current of the relay coil 8a determined by the specification or the like. At this time, the contact pressure of the relay contact 8b is a contact pressure corresponding to the rated current of the relay coil 8a.

  Next, when a power failure occurs in the commercial AC power supply 1 while the load is being driven, the voltage at the connection point between the first resistor 5b and the second resistor 5c, which is the output of the voltage monitoring device 5, decreases. This information can be obtained from the input terminal A to detect that a power failure has occurred.

  At this time, the microcomputer 6a sets the output terminal B to low after setting the output terminal C to high. Thus, after the second transistor 7b of the relay holding device 7 is turned on, the first transistor 6b of the relay driving device 6 is turned off. As a result, the current flowing through the relay coil 8a of the relay 8 decreases to a current value determined by the DC resistance of the relay coil 8a and the series resistance of the resistor 7a. This is called a holding current. At this time, the contact pressure of the relay contact 8b is a contact pressure corresponding to the holding current, and is a contact pressure weaker than that at the rated current.

  When the commercial AC power supply 1 fails, the power supply is lost, so the voltage of the first capacitor 3 and the second capacitor 4 gradually decreases. That is, when the first capacitor 3 is at a certain voltage or higher, the switching operation of the switching power supply 4 continues, power is supplied to the second capacitor 4a and the load of the switching power supply 4, and the second capacitor 4a Although the constant voltage is maintained, if the supply of current to the switching power supply 4 is stopped due to a power failure of the commercial AC power supply 1, the switching operation of the switching power supply 4 cannot be performed, so the voltage of the second capacitor 4a gradually decreases. Eventually, the microcomputer 6a can no longer operate.

  At this time, the speed at which the voltage of the first capacitor 3 and the second capacitor 4a decreases depends on the value of the load current, but when the commercial AC power supply 1 is interrupted, the current supplied to the relay coil 8a is reduced. By reducing to the holding current, the rate of voltage drop of the second capacitor 4a can be slowed down, and the time until the microcomputer 6a becomes inoperable can be made longer.

  In addition, when a power failure occurs as described above and the operation of holding the relay 8 with the holding current by the relay holding device 7 is started, when the power failure is resolved, the output of the voltage monitoring device 5 corresponds to this. When the voltage is generated, the microcomputer 6a detects that the power failure has been canceled. When it is detected that the power failure has been released, the microcomputer 6a sets the output terminal B to high, then sets the output terminal C to low, and performs an operation of returning the current flowing through the relay coil 8a from the holding current to the rated current. As a result, the relay contact becomes a contact pressure generated at the rated current, and the load is driven in this state.

  As described above, when a power failure occurs in the commercial AC power supply 1, the supply current to the relay coil 8a of the relay 8 is set as the holding current, thereby maintaining the voltage of the second capacitor 4a longer than when the holding current is not used. Since the microcomputer 6a can withstand the power failure time and the sequence operation can be performed again after the power failure is resolved, the relay control device can be easily used for the user.

  Further, during a power failure, the contact pressure of the relay contact 8b may decrease and the contact resistance may increase with respect to a load connected to the relay contact 8b and driven by the commercial AC power supply 1. Since no current flows through the relay contact 8b, even if the contact pressure of the relay contact 8b decreases, the temperature rises due to the increase of the contact resistance of the relay contact 8b, or the relay It is possible to prevent the contact 8b from being damaged and to extend the life of the relay contact 8b.

  In addition, according to the present embodiment, since the load current at the time of power failure is reduced, it is possible to reduce the capacity of the capacitor constituting the DC power supply in order to withstand the same time of power failure compared to when the load current is large It becomes. This makes it possible to reduce the component price and the mounting area by reducing the size of the component. In addition, when capacitors of the same capacity are used, the operation guarantee time against power failure can be extended.

  Furthermore, after the power failure is resolved, a current flows to the load via the relay contact 8b. At this time, since the current of the relay coil 8a is increased, the contact pressure of the relay contact 8b is increased and the contact resistance is also increased. Since it is lowered, the contact is not damaged even if the current of the commercial AC power supply 1 flows.

(Embodiment 2)
FIG. 2 is a circuit diagram of the relay control device according to the second embodiment of the present invention.

  In FIG. 2, D of the switching power supply 4 is an output of the switching power supply 4 higher than the output voltage of the switching power supply 4 for the microcomputer 6a.

  In the configuration as described above, the operation is the same as that of the first embodiment, but the power supply voltage connected to the relay coil 8a is higher in the second embodiment, and therefore flows in the relay coil 8a. The current is higher than the rated current. As a result, the contact pressure of the relay contact 8b can be higher than that of driving at the rated current, and the contact resistance between the contacts can be further reduced. As a result, it is possible to extend the contact life due to a decrease in heat generation at the contact of the relay contact 8b.

  Further, since the force for pulling the contact of the relay contact 8b becomes strong, the time for the operation of closing the contact from the opening is shortened, and at that time, the time for the arc to fly between the contacts of the relay contact 8b is shortened or the arc is blown. Since it becomes difficult, the damage of the contact of the relay contact 8b can also be reduced.

  As described above, the relay control device according to the present invention increases the pressure between the contacts of the relay when the commercial AC power supply 1 is energized, and reduces the relay coil current during the power failure of the commercial AC power supply 1 to extend the circuit operation. Since it is designed to withstand a time interruption, the life of the relay can be extended, so that it can be used for all electronic devices that use the relay.

1 is a circuit diagram of a relay control device according to a first embodiment of the present invention. Circuit diagram of relay control apparatus according to second embodiment of the present invention Circuit diagram of conventional relay control device

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Commercial AC power supply 4 Switching power supply 5 Voltage monitoring apparatus 5a 2nd diode (diode)
5b 1st resistance 5c 2nd resistance 6 Relay drive device 6a Microcomputer (microcomputer)
6b 1st transistor 7 relay holding device 7a 3rd resistor 7b 2nd transistor 8 relay 8a relay coil 8b relay contact

Claims (3)

A relay having a relay coil and a relay contact, the relay contact being connected to a load, and a relay driving device having a microcomputer and a first transistor, the collector of the first transistor being connected to one end of the relay coil A voltage monitoring device having a diode, a first resistor, and a second resistor and having a connection point between the first resistor and the second resistor connected to the microcomputer, a second transistor, and a third resistor A relay holding device having a resistor and one end of the third resistor connected to one end of the relay coil together with a collector of the first transistor; When it is detected by the monitoring device that the voltage of the commercial AC power supply has become a certain value or less, the relay that has been performed via the relay driving device is performed. Relay controller energization of the coil to switch to perform via the relay holding device. 2. The microcomputer according to claim 1, wherein when the voltage of the commercial AC power supply returns to a certain value or more, the relay coil is switched to energize the relay coil which has been performed via the relay holding device. Relay control device. 2. The relay control device according to claim 1, wherein the other end of the relay coil is connected to a switching power supply output higher than a voltage of the switching power supply output for the microcomputer.