JP5920193B2 - Relay drive circuit - Google Patents

Description

  The present invention has a first switch for energizing the relay coil to activate the relay contact, a resistor connected in series, and a second switch for energizing the relay coil to maintain the operating state of the relay contact, And a holding circuit connected in parallel to the first switch. The relay driving circuit turns on only the second switch after the relay contact is activated.

FIG. 3 is a block diagram showing a configuration example of a conventional relay drive circuit.
This relay drive circuit drives the relay 2, the power supply device 1 such as an in-vehicle battery is connected to one terminal of the coil 3 of the relay 2, and the drain is connected to the other terminal of the coil 3. An N-channel MOSFET (Metal Oxide Semiconductor Field Effect Transistor) 7 is provided. The transistor 7 has a parasitic diode, and the source of the transistor 7 is grounded.

The relay drive circuit also includes a capacitor 6 having one terminal connected to the gate of the transistor 7, a resistor 5 having one terminal connected to the other terminal of the coil 3, and a resistor 5 having the other terminal connected to the other terminal. And an N-channel MOSFET 8 having a drain connected thereto. The transistor 8 has a parasitic diode, and the source of the transistor 8 is grounded.
In this relay drive circuit, a path C2 to the gate of the transistor 8 is connected to a path C1 to the other terminal of the capacitor 6, and a control signal is input to the paths C1 and C2.
The relay contact 4 turns on or off a power supply to a load (not shown), for example.

  In the relay drive circuit having such a configuration, when an ON signal for instructing ON of the relay 2 is input to the paths C1 and C2 as a control signal, the voltage at one terminal of the capacitor 6 temporarily rises, and the transistor 7 is turned on, and current begins to flow through the coil 3, and the transistor 8 is also turned on, so that the relay contact 4 is activated. At this time, since the transistor 7 is on, almost no current flows on the transistor 8 side.

  The voltage at one terminal of the capacitor 6 decreases as the charging of the capacitor 6 proceeds, whereby the transistor 7 is turned off. As the transistor 7 is turned off, the voltage value applied to the series circuit of the resistor 5 and the transistor 8 increases, the current flowing through the resistor 5 and the transistor 8 increases, and the current flowing through the coil 3 flows through the relay contact 4. Hold the activated state. Since the current that flows in this holding state flows through the resistor 5, it is smaller than the current that flows when the transistor 7 is kept on, thereby realizing power saving.

  Patent Document 1 discloses a relay drive circuit that applies a voltage equal to or higher than an operating voltage to a coil portion by a collector current when a semiconductor switching element is turned on and causes a relay to perform an on operation. The circuit is configured such that the voltage applied to the coil section when the relay is kept on after the relay is turned on is equal to or lower than the operating voltage and equal to or higher than the return voltage.

Japanese Patent Laid-Open No. 11-306943

  In the conventional relay drive circuit that realizes power saving as described above, the coil current is reduced by resistance after the relay is turned on. There is a problem that it becomes impossible to hold the relay with a voltage of a driving power source higher than that of a relay driving circuit that does not have the above-described resistance or the like.

  The present invention has been made in view of the circumstances as described above, and is similar to a relay drive circuit that does not include a resistor for power saving even when the voltage of the drive power supply decreases after the relay is turned on. It is an object of the present invention to provide a relay drive circuit that can hold a relay and can save power.

The relay drive circuit according to the present invention includes a first switch for energizing a relay coil to which a varying voltage is applied and actuating a relay contact, a resistor connected in series, and an energization for the relay coil. A holding circuit connected in parallel to the first switch, and after energizing the relay coil to activate the relay contact, only the second switch is provided. In the relay drive circuit configured to be turned on, detection means for detecting a terminal voltage on the voltage side of the relay coil that fluctuates, and whether or not the voltage value detected by the detection means is lower than a predetermined voltage value and a determining means, said when the determining means determines that low, the first Ri configured tear so as to turn on the switch, said determining means determine a lower than said predetermined voltage value Then, it is determined whether or not the voltage value detected by the detection means is higher than a second voltage value higher than the predetermined voltage value. When the determination means determines that the voltage value is higher, the first switch wherein the configuration tare Rukoto to turn off.

In this relay drive circuit, the first switch, the resistor and the second switch are connected in series, and the holding circuit connected in parallel to the first switch energizes the relay coil and can operate the relay contact. Through the relay coil. After the relay contact is activated, only the second switch is turned on, so that the current flowing through the relay coil is suppressed to a current that can maintain the operation state of the relay contact by a resistor, thereby saving Realize power.
The detection means detects the terminal voltage on the voltage side where the relay coil fluctuates, and the determination means determines whether or not the voltage value detected by the detection means is lower than a predetermined voltage value. When the determination means determines that the voltage is lower than the predetermined voltage value, the first switch is turned on. As a result, the voltage applied to the relay coil decreases, and the current flowing through the relay coil cannot be maintained in the relay contact operating state. Can be prevented.
Further, the determination means determines that the voltage value is lower than the predetermined voltage value, and as a result, after stopping the power saving operation, whether or not the voltage value detected by the detection means is higher than a second voltage value higher than the predetermined voltage value. Determine. When it is determined that the determination means is high, the first switch is turned off and the power saving operation is resumed.

  According to the relay drive circuit according to the present invention, even when the voltage of the drive power supply drops after the relay is turned on, the relay can be held in the same manner as the relay drive circuit that does not include a resistor for power saving. Thus, a relay drive circuit capable of saving power can be realized.

It is a block diagram which shows schematic structure of embodiment of the relay drive circuit based on this invention. It is a flowchart which shows operation | movement of embodiment of the relay drive circuit based on this invention. It is a block diagram which shows the structural example of the conventional relay drive circuit.

Hereinafter, the present invention will be described with reference to the drawings illustrating embodiments thereof.
(Embodiment)
FIG. 1 is a block diagram showing a schematic configuration of an embodiment of a relay drive circuit according to the present invention.
This relay drive circuit drives the relay 2, a positive electrode of the power supply device 1 such as an in-vehicle battery is connected to one terminal of the coil 3 of the relay 2, and a drain is connected to the other terminal of the coil 3. A connected N-channel MOSFET (Metal Oxide Semiconductor Field Effect Transistor) 7 is provided. The transistor 7 has a parasitic diode, and the source is grounded.

This relay drive circuit also includes a resistor 5 having one terminal connected to the other terminal of the coil 3 and an N-channel MOSFET 8 having a drain connected to the other terminal of the resistor 5. The transistor 8 has a parasitic diode, and the source is grounded.
This relay drive circuit includes a control device 9 that receives a control signal from an operation unit (not shown) and controls the transistors 7 and 8 to be turned on or off. The control device 9 is connected to the gate of the transistor 7 through a path C1. Are connected to the gate of the transistor 8 through the path C2. The control device 9 includes a voltage detector 10 that detects the voltage value of one terminal of the coil 3.
The relay contact 4 turns on or off a power supply to a load (not shown), for example.

Hereinafter, the operation of the relay drive circuit having such a configuration will be described with reference to the flowchart of FIG.
The control device 9 stands by until a control signal for instructing to turn on the relay 2 is input (S1). When the control signal for instructing to be on is input, an on signal is output to the paths C1 and C2. Then, the transistors 7 and 8 are turned on (S3).
After turning on the transistors 7 and 8 (S3), the control device 9 waits for a time t1 sufficient for the current to flow through the coil 3 and the relay contact 4 to operate (S5).

After waiting for time t1 (S5), the control device 9 determines whether or not the input of the control signal for instructing to turn on the relay 2 is continued (S7). The detected voltage value V of one terminal of the coil 3 is read (S9).
Next, the control device 9 determines whether or not the read voltage value V is equal to or greater than the predetermined voltage value V1 (S11), and if not, the control signal that instructs the relay 2 to be turned on. It is determined whether or not the input is continued (S7). The predetermined voltage value V1 is determined based on a voltage value at which the relay contact 4 can operate.

If the read voltage value V is equal to or greater than the predetermined voltage value V1 (S11), the control device 9 has confirmed that the relay contact 4 has been operated, and therefore outputs an OFF signal to the path C1 to turn on the transistor 7. It is turned off (S13), and the power saving operation is started. Next, it is determined whether or not the input of the control signal that instructs to turn on the relay 2 is continued (S15). The resistance value of the resistor 5 is such that when the read voltage value V is equal to or higher than the predetermined voltage value V1, the current flowing through the path of the coil 3, the resistor 5 and the transistor 8 determines the operating state of the relay contact 4. It is determined so that it can be held.
If the input of the control signal instructing ON is continued (S15), the control device 9 reads again the voltage value V of one terminal of the coil 3 detected by the voltage detector 10 (S17), and reads it. It is determined whether or not the voltage value V is equal to or greater than the predetermined voltage value V1 (S19).

If the read voltage value V is equal to or higher than the predetermined voltage value V1 (S19), the control device 9 determines whether or not the input of the control signal for instructing the relay 2 to be turned on continues (S15).
If the read voltage value V is not greater than or equal to the predetermined voltage value V1 (S19), the control device 9 outputs an ON signal to the path C1, turns on the transistor 7 (S21), and the current flowing through the coil 3 To stop the power saving operation. As a result, almost no current flows through the transistor 8.

  Next, the control device 9 determines whether or not the input of the control signal for instructing to turn on the relay 2 is continued (S23), and if the input of the control signal for instructing the on is continued, again, The voltage value V of one terminal of the coil 3 detected by the voltage detector 10 is read (S25). Next, it is determined whether or not the read voltage value V is higher than the voltage value V2 (> V1) (S27). The voltage value V2 is set slightly higher than the voltage value V1 in order to prevent chattering.

If the read voltage value V is higher than the voltage value V2 (S27), the control device 9 outputs an off signal to the path C1, turns off the transistor 7 (S13), and restarts the power saving operation.
If the read voltage value V is not higher than the voltage value V2 (S27), the control device 9 determines whether or not the control signal for instructing the relay 2 to be turned on continues (S23).

  The control device 9 outputs an off signal to the paths C1 and C2 and turns off the transistors 7 and 8 unless the control signal for instructing the relay 2 to be turned on continues (S7, 15, 23). Next, the process waits until a control signal instructing to turn on the relay 2 is input (S1).

In the present embodiment, the configuration in which current is passed from the positive electrode of the power supply device 1 to the coil 3 has been described. However, even in the configuration in which current is passed from the coil 3 to the negative electrode of the power supply device 1, If the polarities of the circuit elements and the like are taken into consideration, it is naturally possible to obtain the same operation, action and effect.
Needless to say, even when the power supply from the power supply device 1 is an alternating current and the relay is an alternating current relay, the same operation can be performed.

1 power supply device 2 relay 3 coil (relay coil)
4 Relay contact 7, 8 Transistor (Switch, N-channel MOSFET)
9 Control device (determination means)
10 Voltage detector (detection means)

Claims (1)

A first switch for energizing a relay coil to which a varying voltage is applied to activate a relay contact, a resistor connected in series, and a second for energizing the relay coil and maintaining the operating state of the relay contact And a holding circuit connected in parallel to the first switch, and configured to turn on only the second switch after energizing the relay coil to activate the relay contact. In the relay drive circuit,
A detecting means for detecting a terminal voltage on the voltage side of the relay coil, and a determining means for determining whether or not a voltage value detected by the detecting means is lower than a predetermined voltage value; when it is determined, the Ri configured tear so as to turn on the first switch, wherein the determining means, after determining that less than the predetermined voltage value, the voltage value detected by the detection means is the predetermined and determines whether higher than the second voltage value higher than the voltage value, when it is determined that the higher the determination means is characterized in configuration tare Rukoto to turn off the first switch Relay drive circuit.

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