A relay drive control circuit

Abstract

The present invention relates to a relay drive control circuit, comprising a grounding terminal switch tube connected between a second node at one end of a relay coil and the ground and turned on when a relay drive signal is at a high level, a high voltage power supply for providing the relay with the voltage required for the pull-in action, a low voltage power supply for providing the relay with the voltage required for maintaining the pull-in action, a driving delay circuit for outputting the relay drive signal after delay, a power supply terminal switch tube turned on when the relay drive signal after the delay is at a high level, a current limiting resistor, an energy storage capacitor, and a blocking voltage-stabilizing tube, a high voltage power supply, a power supply terminal switch tube, and a current limiting resistor are connected in series to a first node, a low voltage power supply is connected to a first node at the other end of the relay coil, an energy storage capacitor is connected between the first node and the ground, and a driving delay circuit is connected to the power supply terminal switch tube. The present invention can realize the rapid conversion of high and low drive voltages and achieve the purpose of reducing coil heating.

Description

Technical Field

[0001] The invention belongs to the field of relay drive control, and in particular relates to a drive control circuit which can reduce coil heating and realize fast on-off switching of a relay. Background Art

[0002] The relay is composed of a coil and contacts, and its working process can be divided into two stages: one is the contact closing process, and the other is the contact holding process after closing. The contact closing process requires a higher voltage to provide greater energy, while a lower voltage is required to maintain the closed state after the contact is closed. If a single driving voltage is used, in order to ensure the reliable closing of the relay, only a high driving voltage can be selected. In this way, during the long-term working process after the relay is closed, the relay coil will seriously heat up and consume energy. To solve this problem, there are currently two existing methods:

[0003] The first method is Figure 1 :Adopting dual voltage drive, the high drive voltage 12V is connected to a larger energy storage capacitor C1 through the current limiting resistor R2, and the low drive voltage 7V is connected to this energy storage capacitor C1 through the diode D2. When the relay is not working, the capacitor C1 is charged to the high drive voltage 12V, so as to provide greater energy for the contact of the relay to be attracted; when the relay is attracted, due to the action of the current limiting resistor R2 of the high drive voltage, it will be continuously powered by the low drive voltage 7V. The advantage of doing this is that when the relay is attracted and continues to work, it is powered by the low drive voltage, which can reduce the heating of the relay coil and save energy. At the same time, the blocking effect of the voltage regulator tube ZD3 ensures that the flyback voltage of the relay coil will not be too high when Q2 is turned off, while limiting the follow-flow of the relay coil to make the relay turn off faster.

[0004] The second method is Figure 2 : Utilizing the principle of short-term continuous current of the coil when the relay is closed, PWM drive is adopted. When the relay starts to be closed, the high level lasts for several seconds to ensure the reliable closing of the relay. After the relay is closed, it is driven by the PWM wave. During the trough of the PWM wave, the relay contacts remain closed due to the continuous current of the coil. The advantage of this is that after the relay is closed, it is driven by PWM when it continues to work, which can reduce the heating of the relay coil, save energy, and does not require dual voltage.

[0005] The above two methods have the following defects respectively:

[0006] In the first method, in order to switch to low-voltage drive after the relay is attracted, the current limiting resistor R2 has a larger value. At the same time, in order to ensure that the relay is reliably attracted, the energy storage capacitor C1 has a larger value, which results in a longer time for the high voltage to charge the energy storage capacitor. Since the high voltage takes a long time to charge the energy storage capacitor, it takes a while to recharge the energy storage capacitor after the relay is disconnected. Only when the voltage on the energy storage capacitor is charged to a high voltage can it be attracted again. In some applications, the relay needs to be re-driven and attracted immediately after it is disconnected. At this time, the relay cannot be quickly switched on and off, resulting in it being unusable.

[0007] The second method uses PWM drive, so the coil's freewheeling function must be retained. No reverse freewheeling blocking Zener diode is used, which causes a delay in relay shutdown. This is disadvantageous in some situations, such as when a fault occurs, because the relay cannot be shut down quickly. Summary of the invention

[0008] The object of the present invention is to provide a relay drive control circuit which can solve the problem of rapid closing and disconnecting of a relay and the problem of loss and heating of a relay coil.

[0009] In order to achieve the above object, the technical solution adopted by the present invention is:

[0010] A relay drive control circuit is used to drive and control a relay with a first node and a second node formed at two ends of a coil, respectively. The relay drive control circuit includes a grounding end switch tube connected between the second node and ground and turned on when the relay drive signal is at a high level. The relay drive control circuit also includes a high-voltage power supply for providing the relay with a voltage required for a pull-in action, a low-voltage power supply for providing the relay with a voltage required for maintaining the pull-in action, a drive delay circuit for outputting the relay drive signal after delay, a power supply end switch tube turned on when the relay drive signal after the delay is at a high level, a current limiting resistor, an energy storage capacitor, and a blocking voltage regulator tube. The high-voltage power supply, the power supply end switch tube, and the current limiting resistor are connected in series to the first node, the low-voltage power supply is connected to the first node, the energy storage capacitor is connected between the first node and ground, the drive delay circuit is connected to the power supply end switch tube, the positive electrode of the blocking voltage regulator tube is connected to the first node, and the negative electrode of the blocking voltage regulator tube is connected to the second node.

[0011] Preferably, the power supply end switch tube adopts a triode, the base of the triode is connected to the driving delay circuit, the emitter of the triode is connected to the high voltage power supply, and the collector of the triode is connected to the current limiting resistor.

[0012] Preferably, the output end of the driving delay circuit is connected to the base of the transistor via a first resistor, and a second resistor is connected between the base and emitter of the transistor.

[0013] Preferably, the relay driving circuit further includes a power supply end diode, and the low voltage power supply is connected to the first node via the power supply end diode.

[0014] Preferably, the relay drive control circuit further includes a freewheeling diode, and the positive electrode of the blocking Zener diode is connected to the first node via the freewheeling diode.

[0015] Preferably, the ground-end switch tube is a field effect tube, the gate of the field effect tube is connected to the relay drive signal, the drain of the field effect tube is connected to the second node, and the source of the field effect tube is grounded.

[0016] Preferably, the relay driving signal is connected to the gate of the field effect tube after passing through the third resistor, and a fourth resistor is connected between the gate and source of the field effect tube.

[0017] Preferably, in the driving delay circuit, delay times are set for the high level and the low level of the relay driving signal respectively, and the delay time for the high level of the relay driving signal is greater than the time required for the pull-in action of the relay.

[0018] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art: the present invention can effectively control the action time of the high driving voltage of the relay, realize the rapid conversion of high and low driving voltages, ensure that the relay can be quickly switched on and off while achieving the purpose of reducing the heating of the coil, and reduce the capacity and volume of the energy storage capacitor, saving PCBA space. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Attached Figure 1 It is a schematic diagram of the first existing relay drive control circuit.

[0020] Attached Figure 2 It is a schematic diagram of the second existing relay drive control circuit.

[0021] Attached Figure 3 Schematic diagram of the relay drive control circuit of the present invention. DETAILED DESCRIPTION

[0022] The present invention will be further described below in conjunction with the embodiments shown in the accompanying drawings.

[0023] Embodiment 1: A relay includes a coil and a contact that is actuated by the coil, wherein the circuit where the coil is located is connected to the relay drive signal, and the two ends of the coil form a first node and a second node respectively. When the relay action signal is at a high level, the circuit where the coil is located is connected, so that the coil is energized and the contact is attracted; and when the relay action signal is at a low level, the circuit where the coil is located is disconnected, the coil loses power, and the contact is disconnected.

[0024] As attached Figure 3 As shown, a relay drive control circuit for driving and controlling the above-mentioned relay mainly includes a high-voltage power supply, a low-voltage power supply, a power supply end switch tube, a current limiting resistor R5, an energy storage capacitor C1, a blocking voltage regulator tube ZD3 and a ground end switch tube.

[0025] The high-voltage power supply is used to provide the voltage required for the relay to be pulled in (i.e., the high driving voltage), and a 12V power supply is used in this embodiment. The low-voltage power supply is used to provide the voltage required for the relay to remain pulled in (and the low driving voltage), and a 7V power supply is used in this embodiment. The high-voltage power supply, the power-end switch tube, and the current-limiting resistor R5 are connected in series and connected to the first node, and the low-voltage power supply is also connected to the first node. A power-end diode D2 can also be provided so that the low-voltage power supply is connected to the first node via the power-end diode D2. The energy storage capacitor C1 is connected between the first node and the ground. The driving delay circuit for delaying the output of the relay driving signal is connected to the power-end switch tube, and the power-end switch tube is turned on when the delayed relay driving signal output by the driving delay circuit is at a high level. The positive electrode of the blocking voltage regulator tube ZD3 is connected to the first node, and the negative electrode of the blocking voltage regulator tube ZD3 is connected to the second node; a freewheeling diode D1 can also be provided, and the positive electrode of the blocking voltage regulator tube ZD3 is connected to the first node via the freewheeling diode D1, and the positive electrode of the freewheeling diode D1 is connected to the positive electrode of the blocking voltage regulator tube ZD3. The grounding switch tube that is turned on when the relay drive signal is at a high level is connected between the second node and the ground.

[0026] The power supply end switch tube adopts transistor Q1. The base of transistor Q1 is connected to the driving delay circuit, the emitter of transistor Q1 is connected to the high voltage power supply, and the collector of transistor Q1 is connected to the current limiting resistor R5. The output end of the driving delay circuit is connected to the base of transistor Q1 through the first resistor R1, and the second resistor R2 is connected between the base and emitter of transistor Q1.

[0027] The grounding switch tube uses a field effect tube Q2, the gate of the field effect tube Q2 is connected to the relay drive signal, the drain of the field effect tube Q2 is connected to the second node, and the source of the field effect tube Q2 is grounded. The relay drive signal is connected to the gate of the field effect tube Q2 after passing through the third resistor R3, and a fourth resistor R4 is connected between the gate and source of the field effect tube Q2.

[0028] In the drive delay circuit, delay times are set for the high level and low level of the relay drive signal respectively. Usually, the delay time for the high level of the relay drive signal is greater than the time required for the relay's pull-in action, while the delay time for the low level of the relay drive signal is set to 0, that is, there is no delay for the low level.

[0029] The above relay drive control circuit connects transistor Q1 in series in the high voltage charging circuit, uses the relay drive signal to control the on and off of the transistor Q1, and adds a delay circuit between the relay drive signal and the control electrode of the transistor Q1. The delay time of the high and low levels of the relay drive signal can be controlled separately. The current limiting resistor R5 and the energy storage capacitor C1 are both small in value. In this way, the high voltage drive duration can be delayed and controlled to ensure that the transistor Q1 is quickly closed after the relay is reliably attracted, and the low voltage is used to maintain the attracted state of the relay. At the same time, the blocking function of the blocking voltage regulator ZD3 on the freewheeling is retained, so that the relay can be quickly turned off.

[0030] The specific working process of the above relay drive control circuit is as follows:

[0031] When the power is initially turned on, the relay drive signal is at a low level, the field effect tube Q2 is turned off, the relay is in the off state, the drive delay circuit is invalid for the low-level relay drive signal and does not have a delay effect (the delay time is adjustable), the base of the transistor Q1 is at a low level, and the transistor Q1 is in the on state. At this time, the voltage across the energy storage capacitor C1 starts to rise from 0V. The 12V high-voltage power supply and the 7V low-voltage power supply simultaneously quickly charge the energy storage capacitor C1 to 7V, and then the 12V high-voltage power supply continues to charge the energy storage capacitor C1 to 12. The current direction in this process is as follows Figure 3 As marked by I1, prepare for relay driving. This charging time is extremely short, shorter than the mechanical action time of the relay, so it is considered that there is no need to wait for this charging time.

[0032] When the relay drive signal is high and drives the relay, the field effect tube Q2 is turned on and the relay operates. Due to the delay effect of the drive delay circuit on the high level of the relay drive signal, the base of the transistor Q1 is low level during the entire process of the field effect tube Q2 being turned on and the relay mechanically operating. During the entire process, the 12V high voltage power supply continuously supplies power to the relay to ensure reliable operation of the relay. This current is Figure 3 The duration marked by I2 is the delay time of the driving delay circuit to the high level of the driving signal (the delay time is adjustable, generally adjusted to be greater than the mechanical action time of the relay).

[0033] When the relay is finished, the delay of the driving delay circuit is reached. At this time, the base of transistor Q1 turns to high level, transistor Q1 is turned off, and the relay is powered by energy storage capacitor C1 until the voltage on energy storage capacitor C1 drops to 7V. The current flows as follows Figure 3 Marked by I4 (this time is shorter).

[0034] When the voltage across the energy storage capacitor C1 drops to 7V, the relay is powered by a 7V low-voltage power supply and is in a hold state. The current flows to Figure 3 Marked by I3.

[0035] When the relay drive signal changes from high level to low level and the field effect transistor Q2 is turned off, the relay is disconnected and the transistor Q1 is quickly turned on to charge the energy storage capacitor C1. The process is similar to the initial charging process mentioned above and will not be repeated. The difference is that this is not the initial power-on and the voltage on the energy storage capacitor C1 starts to rise from 7V to 12V instead of from 0V to 12V.

[0036] When the FET Q2 is turned off, the relay coil senses a reverse voltage, and only when the voltage is greater than the threshold of the blocking zener diode ZD3 will it enter the freewheeling state. Figure 3 As marked by I5, the blocking voltage regulator ZD3 blocks the coil flow when the relay is closed, which speeds up the closing speed of the relay. At the same time, there is no need to wait for the charging time of the energy storage capacitor C1 when opening, so the on-off switching speed of the relay in this scheme is faster, and its on-off switching time is essentially determined by the mechanical action time of the relay itself.

[0037] The present invention solves the problem that the relay cannot be quickly closed after being disconnected in the first relay control driving method, and the problem that the relay cannot be quickly disconnected in the second relay control driving method, while ensuring that the power supply voltage maintains a high voltage value during the initial time of relay closing, and the power supply voltage is low during the holding time after the relay is fully closed, so as to reduce the loss and heat generation of the coil.

[0038] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A relay drive control circuit, used for driving and controlling a relay having a first node and a second node formed at two ends of a coil, the relay drive control circuit comprising a grounding switch connected between the second node and ground and turned on when the relay drive signal is at a high level, characterized in that: The relay drive control circuit also includes a high-voltage power supply for providing the relay with a voltage required for a pull-in action, a low-voltage power supply for providing the relay with a voltage required for maintaining a pull-in action, a drive delay circuit for outputting the relay drive signal after delay, a power supply end switch tube that is turned on when the relay drive signal after the delay is at a high level, a current limiting resistor, an energy storage capacitor, and a blocking voltage regulator tube. The high-voltage power supply, the power supply end switch tube, and the current limiting resistor are connected in series and connected to the first node, the low-voltage power supply is connected to the first node, the energy storage capacitor is connected between the first node and the ground, the drive delay circuit is connected to the power supply end switch tube, the positive electrode of the blocking voltage regulator tube is connected to the first node, and the negative electrode of the blocking voltage regulator tube is connected to the second node; in the drive delay circuit, delay times are set for the high level and the low level of the relay drive signal respectively, the delay time for the high level of the relay drive signal is greater than the time required for the pull-in action of the relay, and the delay time for the low level of the relay drive signal is set to 0.

2. A relay drive control circuit according to claim 1, characterized in that: The power supply end switch tube adopts a triode, the base of the triode is connected to the driving delay circuit, the emitter of the triode is connected to the high voltage power supply, and the collector of the triode is connected to the current limiting resistor.

3. A relay drive control circuit according to claim 2, characterized in that: The output end of the driving delay circuit is connected to the base of the transistor via a first resistor, and a second resistor is connected between the base and emitter of the transistor.

4. A relay drive control circuit according to claim 1, characterized in that: The relay driving circuit further includes a power supply end diode, and the low voltage power supply is connected to the first node via the power supply end diode.

5. A relay drive control circuit according to claim 1, characterized in that: The relay drive control circuit further includes a freewheeling diode, and the positive electrode of the blocking Zener diode is connected to the first node via the freewheeling diode.

6. A relay drive control circuit according to claim 1, characterized in that: The grounding switch tube is a field effect tube, the gate of the field effect tube is connected to the relay drive signal, the drain of the field effect tube is connected to the second node, and the source of the field effect tube is grounded.

7. A relay drive control circuit according to claim 6, characterized in that: The relay driving signal is connected to the gate of the field effect tube after passing through the third resistor, and a fourth resistor is connected between the gate and the source of the field effect tube.

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