JPH03134928A - Relay driving circuit - Google Patents

Abstract

PURPOSE:To lessen the power consumption of a relay in its operation by changing over the voltage source for impressing a voltage on a relay coil when the relay contact is sensed being closed. CONSTITUTION:When a motion sensitive voltage or over it given by a DC source is impressed on a relay coil 5a, a contact 5b is shut, and when it is sensed by a sensor circuit 7, the output of an AND circuit 11 is also turned to L, and a transistor TR2 for impression of the motion sensitive voltage is put off while only a transistor TR4 for impression of the holding voltage is left as in continuity. Accordingly the holding voltage sunk by a resistance 3 is impressed on the relay coil 5a from the DC source 1. when the voltage of this DC source 1 has sunk momentarily while the condition is such that this holding voltage is being impressed on the relay coil 5a, the sensor circuit 7 senses that the contact 5b is open, and the transistor TR2 is put on immediately, and the contact 5b is returned to the closed condition.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a relay drive circuit that drives relay contacts to a closed state while a relay operation command signal is applied.

<Prior Art and Problems to be Solved by the Invention> FIG. 2 shows an in-shell relay drive circuit. Power supply E is connected to relay coil L through the emitter and collector of transistor Q. A relay operation command signal S can be applied to the base of the transistor Q.

According to this circuit, the power supply E is opened and closed by the transistor Q depending on the presence or absence of the relay operation command signal S, and the relay coil L
The drive can be controlled. However, with this method,
While the relay is being driven, the power supply voltage E is constantly applied to the relay coil.

Since the power supply voltage E is set to be higher than the relay voltage, it has a considerably large value. Therefore, the power consumption of the relay coil L becomes large and heat is generated, so that measures have to be taken against the heat.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a relay drive circuit that requires less power consumption of the relay during operation.

Means and Effects for Solving the Problems> A relay drive circuit of the present invention for achieving the above objects includes a first voltage source that applies a voltage higher than the relay's sensing voltage to the relay coil, and a relay contact point. A second voltage source that applies sufficient voltage to the relay coil for holding, a contact detection circuit that detects whether the relay contact is open or closed, and a voltage source that is applied to the relay coil when the contact detection circuit detects that the relay contact is closed. switching means for switching from the first voltage source to the second voltage source.

According to the relay drive circuit configured as described above, the opening and closing of the relay contact is constantly detected, and when the closing of the relay contact is detected, the voltage source applied to the relay coil is changed from the first voltage source to the second voltage source. Switch to

Therefore, only the minimum voltage required to maintain the relay contact can be applied to the relay coil, and power consumption can be reduced.

Furthermore, the relay drive circuit of the present invention switches the voltage source applied to the relay coil from the first voltage source to the second voltage source for the first time after a certain period of time Tl has passed when the contact detection circuit detects the closing of the relay contact. There may be.

According to this, a voltage higher than the relay voltage is applied until a certain period of time T has passed after the relay contact is closed, so even if the power supply voltage fluctuates slightly during this time, the relay contact will not be disconnected. be able to.

Further, the present invention may include a periodic voltage application means for applying the first voltage source to the relay coil at fixed time intervals T2 while receiving the relay operation command signal.

According to this, even if the power supply voltage is momentarily cut off during relay operation and the relay contacts are disconnected, and the original state cannot be restored, a voltage higher than the touching voltage will be generated after a certain time interval T2 at most. Since it is applied to the relay coil, the relay contact can be closed.

<Example> Embodiments will be described in detail below with reference to the accompanying drawings showing examples.

FIG. 1 is a circuit diagram showing an example of a relay drive circuit of the present invention. Reference numeral 1 denotes a DC power supply having a voltage higher than the voltage applied to the relay 5, and is connected to the relay coil 5a through the emitter and collector of the holding voltage application transistor 4 and the voltage drop resistor 3.

Further, the DC power source 1 is also connected to the relay coil 5a through the emitter and collector of the emotional voltage applying transistor 2. A reverse bypass diode 6 is connected to the relay coil 5a.

Opening/opening of the relay contact 5b is detected by the contact detection circuit 7. The contact detection circuit 7 outputs a high level signal 1 only when it detects that the relay is closed. Contact detection circuit 7
The output of is connected to one input terminal of an AND circuit 11 through a NOT circuit 10, and the other input terminal of the AND circuit 11 is connected to a relay operation command signal line 9. Further, the logic output terminal of the AND circuit 11 is connected to the base of the transistor 2 for applying a moving voltage, and the relay operation command signal line 9 is connected to the base of the transistor 4 for applying a holding voltage. The contact detection circuit 7, NOT circuit 10, and AND circuit 11 constitute a control circuit 8.

The operation of the above circuit will be explained. First, relay contact 5
Suppose that b is in the open state. When a command signal to close the relay contact 5b is input through the relay operation command signal line 9, a voltage is applied to the base of the holding voltage applying transistor 4, and the holding voltage applying transistor 4 becomes conductive. At the same time, the AND circuit 11 becomes conductive and a voltage is also applied to the base of the emotional voltage applying transistor 2. For this reason, both transistors 2.4 become conductive, but the voltage of the DC power supply 1 is applied to the relay coil 5a via the path on the side of the emotional voltage application transistor 2, which has less resistance. Therefore, a voltage equal to or higher than the impression voltage is applied to the relay coil 5a, and the contact 5b of the relay 5 is closed.

When the contact detection circuit 7 detects that the contact 5b is closed,
The logic output of the NOT circuit 10 becomes low level, and the logic output of the AND circuit 11 also becomes low level. Therefore, the moving voltage applying transistor 2 is cut off, and only the holding voltage applying transistor 4 remains conductive. Therefore, the holding voltage dropped by the voltage drop resistor 3 is applied from the DC power supply 1 to the relay coil 5a.

Now, if the voltage of the DC power supply 1 drops momentarily due to a mechanical shock or a momentary interruption of the commercial power supply while the holding voltage is applied to the relay coil 5a, the relay contact 5b may not be able to be held. . At this time, since the contact detection circuit 7 detects that the relay contact 5b is open, the moving voltage applying transistor 2 immediately becomes conductive, and the contact 5b is returned to the closed state.

As described above, according to the above embodiment, a voltage higher than the touching voltage is applied only when closing the relay, and after closing, sufficient voltage is applied to hold the relay contact, so the relay contact is held. Therefore, the power consumption of the relay is reduced. In addition, the amount of heat generated from the relay also decreases accordingly.

In the above embodiment, the detection signal of the contact detection circuit 7 is used to control the conduction/cutoff of the emotional voltage applying transistor 2 in real time. may be inserted, and when a detection signal from the contact detection circuit 7 is received, a signal of the same type as the detection signal may be output only after a certain period of time T1.

In this way, after the relay contact is made, the voltage is switched to the holding voltage after a while, so it is possible to prevent the relay contact from being disconnected even if the power supply voltage fluctuates slightly during time T1.

Furthermore, an emotional voltage periodic application circuit may be added that sends out a relay operation signal to the relay operation command signal line 9 at fixed time intervals T2 while receiving the relay operation command signal. In this way, even if the voltage of the DC power supply 1 drops due to a mechanical shock or a momentary interruption of the commercial power supply, and the relay contact opens, the relay contact can be closed after 12 hours at the most, so the relay can be closed. You will be able to return automatically.

Although the present invention has been described above based on the embodiments, the present invention is not limited to the above embodiments.

For example, the function of the control circuit 8 may be replaced by a microcomputer. Various design changes can be made without changing the gist of the invention.

<Effects of the Invention> As described above, according to the relay drive circuit of the present invention, only the minimum voltage for maintaining the relay contact is applied to the relay coil during relay operation, reducing power consumption. In addition to this, it is possible to suppress the generation of heat as much as possible.

In addition, by delaying the timing of switching the voltage applied to the relay coil (claim 2), and by providing a feature of touching voltage at regular intervals (claim 3), a relay drive circuit is realized that takes measures against instantaneous power interruptions. be able to.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an example of the relay drive circuit of the present invention, and FIG. 2 is a circuit diagram of a conventional relay drive circuit. 0 2... Transistor for impressing voltage application, 3... Voltage drop resistance, 4... Transistor for applying holding voltage, 5b... Relay contact, 5 a... Relay coil, 7... Contact detection Circuit, 10...N07 circuit, 11...AND circuit

Claims (1)

[Claims] 1. In a relay drive circuit that drives a relay contact to close while receiving a relay operation command signal, a first voltage source that applies a voltage higher than the relay's sensing voltage to the relay coil; a second voltage source that applies a voltage sufficient to hold the relay contacts to the relay coil; a contact detection circuit that detects whether the relay contacts are open or closed; 1. A relay drive circuit comprising: switching means for switching an applied voltage source from a first voltage source to a second voltage source. 2. In a relay drive circuit that drives relay contacts to close while receiving a relay operation command signal, a first voltage source that applies a voltage higher than the relay's sensing voltage to the relay coil and a voltage source that is sufficient to hold the relay contacts. a second voltage source that applies a certain voltage to the relay coil; a contact detection circuit that detects whether the relay contact is open or closed; A relay drive circuit comprising: switching means for switching from a first voltage source to a second voltage source. 3. The relay drive circuit according to claim 1 or 2, further comprising a voltage periodic applying means for applying the first voltage source to the relay coil at fixed time intervals while receiving the relay operation command signal.