Relay control circuit

Abstract

The utility model belongs to the technical field of control circuits, and provides a relay control circuit, which comprises a power supply, a relay, a first field effect transistor, a second field effect transistor, a first resistor, a second resistor and a capacitor, the power supply is connected with the capacitor which is connected with the first resistor which is connected with the input end of the first field effect transistor. The control end of the first field effect transistor is used for connecting a control chip, and the output end of the first field effect transistor is grounded; the power supply is also connected with a coil input end of the relay, a coil output end of the relay is respectively connected with input ends of the second resistor and the second field-effect tube, and output ends of the second resistor and the second field-effect tube are connected with an input end of the first field-effect tube; the control end of the second field effect transistor is connected between the capacitor and the first resistor. According to the utility model, small relay pull-in state holding current can be provided, and the power consumption and heating conditions of the relay are reduced.

Description

Technical Field

[0001] The utility model belongs to the technical field of control circuits, and more specifically, relates to a relay control circuit. Background Art

[0002] Since relays have an isolation function and their automatic switching elements and control drive circuits are relatively simple, they are widely used in electronic circuits.

[0003] For a relay, sufficient suction force must be generated to close the switch, which requires a relatively large current, while a small maintenance current is required to maintain the closed state. If a large current is continued to be used in the closed state, it will not only increase the power consumption of the relay and waste electricity, but also cause unnecessary heating of the coil, resulting in high temperature of the relay and reduced service life. Utility Model Content

[0004] The utility model aims to provide a relay control circuit, aiming to provide a smaller relay energized state maintaining current, and reduce the power consumption and heating of the relay.

[0005] To achieve the above object, the technical solution adopted by the utility model is: to provide a relay control circuit, including: a power supply, a relay, a first field effect transistor, a second field effect transistor, a first resistor, a second resistor and a capacitor;

[0006] The power supply is connected to the capacitor, the capacitor is connected to the first resistor, the first resistor is connected to the input end of the first field effect tube; the control end of the first field effect tube is used to connect to the control chip, and the output end of the first field effect tube is grounded;

[0007] The power supply is also connected to the coil input end of the relay, the coil output end of the relay is respectively connected to the second resistor and the input end of the second field effect tube, the output end of the second resistor and the second field effect tube is connected to the input end of the first field effect tube; the control end of the second field effect tube is connected between the capacitor and the first resistor.

[0008] Furthermore, the relay control circuit further includes:

[0009] diode;

[0010] The input end of the diode is connected to the coil output end of the relay, and the output end of the diode is connected to the coil input end of the relay.

[0011] Furthermore, the relay is a normally open relay or a normally closed relay.

[0012] Furthermore, if the relay is a normally open relay, the relay also includes a normally open contact; one end of the normally open contact is the input end of the relay, and the other end is the output end of the relay; the normally open contact is closed when the coil is energized and is opened when the coil is de-energized.

[0013] Furthermore, if the relay is a normally closed relay, the relay also includes a normally closed contact; one end of the normally closed contact is the input end of the relay, and the other end is the output end of the relay; the normally closed contact is opened when the coil is energized and closed when the coil is de-energized.

[0014] Furthermore, the first field effect transistor and the second field effect transistor are: N-channel field effect transistors or P-channel field effect transistors.

[0015] Furthermore, the resistance of the first resistor and the second resistor is 51KΩ, the capacitance of the capacitor is 4.7μF, and the supply voltage of the power supply is 12V.

[0016] Compared with the prior art, the embodiments of the present invention have the following beneficial effects:

[0017] The relay control circuit of the embodiment of the utility model includes: a power supply, a relay, a first field effect tube, a second field effect tube, a first resistor, a second resistor and a capacitor; the power supply is connected to the capacitor, the capacitor is connected to the first resistor, and the first resistor is connected to the input end of the first field effect tube; the control end of the first field effect tube is used to connect the control chip, and the output end of the first field effect tube is grounded; the power supply is also connected to the coil input end of the relay, the coil output end of the relay is respectively connected to the second resistor and the input end of the second field effect tube, and the output end of the second resistor and the second field effect tube is connected to the input end of the first field effect tube; the control end of the second field effect tube is connected between the capacitor and the first resistor. When the first field effect tube receives a control signal and turns on, the initial voltage across the capacitor is 0V, and the initial voltage across the first resistor is the power supply voltage. At this time, the second field effect tube is turned on, and the current flows from the power supply, the relay coil, the second field effect tube, and the first field effect tube to the ground, which can provide the large current required when the relay contact is actuated. As the capacitor charges, the voltage across the capacitor gradually rises to the power supply voltage, the voltage across the first resistor gradually decreases to 0V, the second field effect transistor is turned off, and the current flows from the power supply, the relay coil, the second resistor, the first field effect transistor to the ground. Due to the current limiting effect of the second resistor, the current in the coil is small at this time, thereby providing a smaller relay closure state maintenance current, reducing relay power consumption and heat generation, and increasing the life of the relay. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A schematic diagram of the structure of the relay control circuit provided in the embodiment of the utility model Figure 1 ;

[0019] Figure 2 A schematic diagram of the structure of the relay control circuit provided in the embodiment of the utility model Figure 2 . DETAILED DESCRIPTION

[0020] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0021] Relay is a very common device in control systems. It is used to control a variety of loads. It is simple and reliable to use. Relay consists of a coil and a contact structure. When current passes through the coil, it will generate electromagnetic attraction. This electromagnetic attraction can drive the contact structure to work.

[0022] Common relay control circuits in the prior art are as follows: Figure 1 As shown in the figure, the power supply voltage VCC of the relay coil P is 12V. When the control field effect tube Q1 is turned on, the current in the relay coil P is converted into a magnetic field, thereby controlling the relay contact JK1 to close or open. Generally, when the relay control contact JK1 is activated (closed or opened), a relatively large current is required in the coil, while a relatively small current is required in the holding stage. Figure 1 In the circuit, the current in the relay contact holding stage and the action stage is the same. Assuming the resistance of the coil is R, the current is 12 / R. This will cause a waste of energy, unnecessary heating of the coil, high temperature of the relay, and reduced service life.

[0023] In order to solve the above problems, the utility model provides a relay control circuit. Figure 2 As shown, it includes: a power supply VCC, a relay (including a coil P and an electric shock JK1), a first field effect transistor Q1, a second field effect transistor Q2, a first resistor R1, a second resistor R2 and a capacitor C. Among them, the resistance values ​​of the first resistor R1 and the second resistor R2, the capacitance value of the capacitor C, and the voltage of the power supply VCC can be set by yourself. For example, in this embodiment, the resistance values ​​of the first resistor and the second resistor are 51KΩ, the capacitance value of the capacitor is 4.7μF, and the power supply voltage of the power supply is 12V.

[0024] The power supply VCC is connected to the capacitor C, the capacitor C is connected to the first resistor R1, and the first resistor R1 is connected to the input terminal 3 of the first field effect transistor Q1. The control terminal 1 of the first field effect transistor Q1 is used to connect the control chip, and the output terminal 2 of the first field effect transistor Q1 is grounded. The power supply VCC is also connected to the coil P input terminal of the relay, and the coil P output terminal of the relay is respectively connected to the second resistor R2 and the input terminal 6 of the second field effect transistor Q2, and the output terminal 5 of the second resistor R2 and the second field effect transistor Q2 is connected to the input terminal 3 of the first field effect transistor Q1. The control terminal 4 of the second field effect transistor Q2 is connected between the capacitor C and the first resistor R1.

[0025] Furthermore, the relay control circuit further includes: a diode D1. The diode D1 is connected in parallel with the coil P, the input end of the diode D1 is connected to the output end of the coil P of the relay, and the output end of the diode is connected to the input end of the coil P of the relay.

[0026] In this embodiment, when the control terminal 1 of the first field effect tube Q1 receives the control signal of the control chip and controls the first field effect tube Q1 to be turned on, the initial voltage across the capacitor C is 0V, and the initial voltage across the first resistor R1 (i.e., the voltage of the control terminal 4 of the second field effect tube Q2) is 12V. At this time, the second field effect tube Q2 is turned on, and the current flows from the 12V power supply VCC, through the relay coil P, the second field effect tube Q2, and the first field effect tube Q1 directly to GND. According to circuit theory, the current value is 12 / R. Therefore, the large current required when the relay contact JK is actuated can be provided.

[0027] As the capacitor C is charged, the voltage across the capacitor C gradually rises to 12V, and the voltage across the first resistor R1 (i.e., the voltage of the control terminal 4 of the second field effect transistor Q2) gradually decreases to 0V, and the second field effect transistor Q2 is turned off. The current flows from the 12V power supply, through the relay coil P, the second resistor R2, the first field effect transistor Q1 to GND. Due to the current limiting effect of the resistor R2, the current in the coil is relatively small at this time, which is 12 / (R+R2). By adjusting the resistance value of R2, the current passing through the coil P can meet the need to maintain the relay contact JK1 without causing waste of electric energy and reducing heat generation.

[0028] It can be seen that the relay control circuit of the embodiment of the utility model includes: a power supply, a relay, a first field effect tube, a second field effect tube, a first resistor, a second resistor and a capacitor; the power supply is connected to the capacitor, the capacitor is connected to the first resistor, and the first resistor is connected to the input end of the first field effect tube; the control end of the first field effect tube is used to connect the control chip, and the output end of the first field effect tube is grounded; the power supply is also connected to the coil input end of the relay, the coil output end of the relay is respectively connected to the second resistor and the input end of the second field effect tube, and the output end of the second resistor and the second field effect tube is connected to the input end of the first field effect tube; the control end of the second field effect tube is connected between the capacitor and the first resistor. When the first field effect tube receives a control signal and turns on, the initial voltage across the capacitor is 0V, and the initial voltage across the first resistor is the power supply voltage. At this time, the second field effect tube is turned on, and the current flows from the power supply, the relay coil, the second field effect tube, and the first field effect tube to the ground, which can provide the large current required when the relay contact is actuated. As the capacitor charges, the voltage across the capacitor gradually rises to the power supply voltage, the voltage across the first resistor gradually decreases to 0V, the second field effect transistor is turned off, and the current flows from the power supply, the relay coil, the second resistor, the first field effect transistor to the ground. Due to the current limiting effect of the second resistor, the current in the coil is small at this time, thereby providing a smaller relay closure state maintenance current, reducing relay power consumption and heat generation, and increasing the life of the relay.

[0029] Optionally, the above-mentioned relay may be a normally open relay or a normally closed relay, which is not limited in this embodiment.

[0030] For a normally open relay, contact JK1 is a normally open contact, one end of which is the input end of the relay and the other end is the output end of the relay. The normally open contact is closed by the attraction of electromagnetic force when the coil P is energized, and is opened when the coil P is de-energized.

[0031] For a normally closed relay, contact JK1 is a normally closed contact, one end of which is the input end of the relay and the other end is the output end of the relay. The normally closed contact is opened by the attraction of electromagnetic force when the coil P is energized, and closed when the coil P is de-energized.

[0032] Whether a normally open relay or a normally closed relay is used, the relay in the relay control circuit of this embodiment can be replaced according to actual usage requirements.

[0033] Optionally, the first field effect transistor and the second field effect transistor are: N-channel field effect transistors or P-channel field effect transistors.

[0034] Field effect transistor is a semiconductor device used for amplification, switching and modulation in electronic devices. According to its conductivity type, field effect transistor can be divided into two basic types: N-channel field effect transistor or P-channel field effect transistor.

[0035] The channel in an N-channel field effect transistor is formed by electrons. A small amount of donor impurities, usually elements such as phosphorus or arsenic, are doped in the substrate of the N-channel field effect transistor. These donor impurities provide additional free electrons, and when a forward bias is applied to the gate of the N-channel field effect transistor, a negative bias electric field is formed, attracting free electrons into the channel. This allows the electrons in the channel to flow, thus forming a conductive path. When a forward bias is applied between the gate and the source, the electrons in the channel begin to conduct. When a negative bias is applied between the gate and the source, the electrons in the channel stop conducting.

[0036] In contrast, the channel of a P-channel field effect transistor is formed by holes. A small amount of acceptor impurities, usually elements such as boron or aluminum, are doped in the substrate of a P-channel field effect transistor. These acceptor impurities provide additional holes, and when a negative bias is applied to the gate of the P-channel field effect transistor, a positive bias electric field is formed, attracting holes into the channel. This allows the holes in the channel to flow, thus forming a conductive path. When a negative bias is applied between the gate and the source, the holes in the channel begin to conduct. When a forward bias is applied between the gate and the source, the holes in the channel stop conducting.

[0037] In this embodiment Figure 2 In the example, an N-channel field effect transistor is used, ports 1 and 4 of Q1 and Q2 are gates, ports 3 and 6 are sources, and ports 2 and 4 are drains.

[0038] The control circuit of this embodiment can not only meet the large current when the relay contacts are in action, but also limit the coil current during the relay contact holding stage, thereby reducing power consumption and heat generation.

[0039] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A relay control circuit, characterized in that: include: A power supply, a relay, a first field effect transistor, a second field effect transistor, a first resistor, a second resistor and a capacitor; The power supply is connected to the capacitor, the capacitor is connected to the first resistor, the first resistor is connected to the input end of the first field effect tube; the control end of the first field effect tube is used to connect to the control chip, and the output end of the first field effect tube is grounded; The power supply is also connected to the coil input end of the relay, the coil output end of the relay is respectively connected to the second resistor and the input end of the second field effect tube, the output end of the second resistor and the second field effect tube is connected to the input end of the first field effect tube; the control end of the second field effect tube is connected between the capacitor and the first resistor.

2. The relay control circuit according to claim 1, characterized in that: Also includes: diode; The input end of the diode is connected to the coil output end of the relay, and the output end of the diode is connected to the coil input end of the relay.

3. The relay control circuit according to claim 1, characterized in that: The relay is a normally open relay or a normally closed relay.

4. The relay control circuit according to claim 3, characterized in that: If the relay is a normally open relay, the relay further includes a normally open contact; One end of the normally open contact is the input end of the relay, and the other end is the output end of the relay; the normally open contact is closed when the coil is energized, and is opened when the coil is de-energized.

5. The relay control circuit according to claim 3, characterized in that: If the relay is a normally closed relay, the relay further includes a normally closed contact; One end of the normally closed contact is the input end of the relay, and the other end is the output end of the relay; the normally closed contact is opened when the coil is energized, and is closed when the coil is de-energized.

6. The relay control circuit according to claim 1, characterized in that: The first field effect transistor and the second field effect transistor are: N-channel field effect transistors or P-channel field effect transistors.

7. The relay control circuit according to claim 1, characterized in that: The resistance values ​​of the first resistor and the second resistor are 51KΩ, the capacitance value of the capacitor is 4.7μF, and the supply voltage of the power supply is 12V.

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