JPS6016054B2 - Relay drive circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a drive circuit for a relay used in electronic control equipment and the like.

Many ordinary relay drive circuits are configured to apply a sufficiently high voltage to allow a continuous current to flow during the relay drive period, but as is well known, 1/2 of the holding current required to maintain the operating state Considering this point, the conventional configuration described above wastes power during the continuous operation period.

A conventional laser drive circuit designed to reduce power consumption is shown in FIG.

In this circuit, a parallel circuit of a relay 1 and a surge absorbing diode 2, a parallel circuit of a capacitor 3 and a resistor 4, and a switching transistor 5 are connected in series between the DC power line Vo and GND. In this state, the capacitor 3 is not charged, and in that state, as shown in FIG. 2, when the input signals V and N applied to the base of the transistor 5 become high level, the transistor 5 is turned on. A driving current flows through the relay 1.At this time, the capacitor 3 is gradually charged, so the electronic voltage VR between the terminals of the relay 1 is initially set to a sufficiently high value V2, as shown in Figure 2. 1 is activated, and then gradually decreases to the low value V required to maintain the operating state of relay 1, thereby preventing unnecessary power consumption.However, in the circuit shown in Figure 1, for example, the input When the signals V and N become low level for a short period of time as shown in FIG. 2 due to some reason such as noise, and in response to this, the transistor 5 is turned off for a short period of time, the voltage VR between the terminals of the relay 1 becomes As shown in Figure 2,
When transistor 5 is turned off, it becomes almost OV, and even if transistor 5 is turned on immediately, its off time is short and capacitor 3 is hardly discharged, so voltage VR reaches voltage V2 required to operate relay 1. It doesn't rise.

Therefore, once the contact of the relay 1 is restored, even if the transistor 5 is turned on again immediately after that, the relay 1 will not operate. Such a malfunction also occurs when the contacts of the relay 1 are restored due to a momentary power outage of the entire circuit or a mechanical shock applied to the relay 1. This invention was made in view of the above-mentioned conventional problems, and its purpose is to provide a power-saving circuit that reduces the applied voltage after IJ relay operation, even if the relay drive is momentarily interrupted due to some malfunction. The object of the present invention is to provide a relay drive circuit that prevents relay contacts from remaining reset. Hereinafter, embodiments of the present invention will be described in detail based on the drawings. FIG. 3 is a block diagram showing a schematic configuration of a relay drive circuit according to the present invention, and FIG. 4 is a diagram showing an example of the circuit.

As shown in FIG. 3, the relay drive circuit of the present invention has a toe end connected to one pole Vo of a DC power source, and a voltage dividing element 1 connected in series to the end of the relay 10.
1 and connected in series between the other end of this voltage dividing element 11 and the other pole GND of the DC power supply, and relay drive input signals V,
A first switching element 12 that is turned on and off in response to N, a second switching element 13 connected in parallel with the voltage dividing element 11, and a second switching element 13 that oscillates when the first switching element 12 is turned on. and an oscillation circuit 14 that turns on the second switching element for a short period of time in a relatively long cycle with its oscillation output, and during the relay drive period when the first switching element 12 is turned on, the second switching element turns on. When the switching element 13 is off, a relatively small voltage is applied to the IJ relay 1, and the second switching element 13 is turned off.
This is characterized in that a relatively large voltage is applied to the overlay relay 10 when the switching element i3 is on.

In FIG. 4 showing a specific circuit example, a resistor 11 is used as the voltage dividing element, and NPN transistors 12 and 13 are used as the first and second switching elements, respectively.
``A relaxation oscillation circuit 14 centered around a PUT (programmerful unidirectional transistor) 15 is used as the oscillation circuit.

In addition, 16 is a diode for surge absorption of the relay 10,
17 and 18 are resistors for the base bias circuit of the transistor 12. In the relaxation oscillation circuit 14, PUT1
A constant voltage VG is applied to the gate of PUT 15 from the junction of resistors 19 and 20 connected in series between the DC power supply Vo and GND, and the anode of PUT 15 is applied to the gate of PUT 15, which is connected in series between the DC power supply Vo and GND. The voltage V^ at the connection point between the resistor 21 and the capacitor 22 is applied, and the cathode of the PUT 15 is connected to the first transistor 2 through the resistors 23 and 24 connected in series.
is connected to the collector side of the resistor 23, 24.
The oscillation output VK taken out from the connection point is applied to the base of the second transistor 13.

Next, the operation of the laser drive circuit constructed as described above will be explained with reference to FIG. 5, which shows operating waveforms of each part thereof.

In the non-drive state where the input signal V/N is at a low level, the transistor 12 is of course off, and not only one relay is not driven, but also the cathode circuit of the PUT 15 is cut off, so the oscillation circuit 14 is There is no operation, and capacitor 22 is fully charged. Therefore, the input signal VI
When N goes high and transistor 12 turns on,
The oscillation circuit 14 starts operating, and its oscillation output VK turns the transistor 13 on and off, and the transistor 1
When transistor 3 is on, the drive current for relay 10 flows through transistors 13 and 12, and when transistor 13 is off, the drive current for relay 10 flows through resistor 11 and transistor 12.

This will be explained together with the detailed operation of the oscillation circuit 14.

First, when the transistor 12 is turned on, the capacitor 0 capacitor 22
is already fully charged, so immediately PUT1 5
The cathode current flows through the resistors 23 and 24 and the transistor 12, and the PUT 15 is cut off after the oscillation pulse width Δt time. While the cathode current of PUT 15 is flowing, the oscillator output VK is at a high level, and at that time the transistor 13 is turned on. However, when PUT is cut off, the oscillation output VK becomes a low level, and at that time the transistor 13 is turned off. Further, when the PUT 15 is cut off, the capacitor 22 is gradually charged to 0, and when the anode voltage V^ reaches a constant value determined by the gate voltage VG, the PUT 15 is turned on again. In this way,
The oscillation circuit 14 turns on the transistor 13 for short periods of time Δt at a relatively long period. Relay 10 and resistor 1 1
As shown in FIG. 5, the voltage Vc at the connection point is low when the transistor 13 is on, and high when the transistor 13 is off.

Therefore, the voltage (V.-Vc) between the terminals of the relay 10 becomes a sufficiently high value V2 to operate the relay 10 when the transistor 13 is on, and maintains the operating state of the relay 10 when the transistor 13 is off. This results in a sufficiently low value V, which prevents the power consumption during the continuous driving period from increasing more than necessary.This power saving effect is sufficiently large even after subtracting the power consumption of the oscillation circuit 14. Furthermore, as shown in FIG. 5, even if, for example, a momentary power outage occurs during the relay drive period, and the drive of the relay 10 is cut off for a short time and the contacts are restored, if the drive is resumed, the oscillation circuit 14 will be activated. The oscillation operation is restarted, and the transistor 13 is turned on by the first pulse of the oscillation output VK after restarting, and a sufficiently high voltage V2 is applied to the relay 10, so the relay 10 is always operated and the contacts remain in the restored state. Note that the voltage dividing element 11 may be a constant voltage diode, etc., various types of switching elements 12 and 13 can be used, and the oscillation circuit 14 is not limited to the one shown in FIG. Of course.

As explained in detail above, according to the IJ drive circuit according to the present invention, it is possible to eliminate unnecessarily large power consumption during the continuous driving period of the relay, and also to prevent noise, instantaneous power outage, mechanical shock, etc. Even if the contact returns to a certain point during the relay drive period, the contact can be prevented from remaining in the reset state.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a conventional relay drive circuit, FIG. 2 is an operating waveform diagram of its main parts, FIG. 3 is a block diagram of the relay drive circuit of the present invention, and FIG. 4 is a diagram of the relay drive circuit of the present invention. FIG. 5, which is a diagram showing a specific embodiment, is an operation waveform diagram of the main part in FIG. 4. 10... Relay, 11... Voltage dividing element, 12
...First switching element, 13... Second switching element, 14... Oscillation circuit. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] 1. A series circuit consisting of a relay, a voltage dividing element, and a first switching element, a DC power supply to which this series circuit is connected, a second switching element connected in parallel to the molecular pressure element, and the first switching element. an oscillation circuit that derives an oscillation output that makes the second switching element conductive for a short period of time in a relatively long period when the first switching element is conductive.