A reverse electromotive force active discharge protection circuit and active arc extinguishing method

Abstract

The present invention relates to the field of DC system protection, and specifically to a reverse electromotive force active discharge protection circuit, including a signal processing circuit, a discharge drive circuit, a discharge resistor and a polarity switching circuit, one end of the discharge resistor is electrically connected to the polarity switching circuit, and the other end is electrically connected to the discharge drive circuit, the polarity switching circuit and the signal processing circuit are both electrically connected to the discharge drive circuit, the polarity switching circuit is provided with two discharge interfaces for parallel DC loads, and the signal processing circuit outputs a load drive signal for controlling the DC load and a discharge control signal for controlling the discharge drive circuit. The present invention provides a reverse electromotive force active discharge protection circuit, which can actively extinguish arcs and solve the problem of damage to switch or relay contacts caused by the reverse electromotive force generated by an inductive device, and also provides an active arc extinguishing method based on the reverse electromotive force active discharge protection circuit, which processes the reverse electromotive force that harms the circuit in an active and early intervention manner.

Description

Technical Field

[0001] The present invention relates to the technical field of direct current system protection, and in particular to a reverse electromotive force active discharge protection circuit and an active arc extinguishing method. Background Art

[0002] When a switch or relay cuts off the power supply to an inductive device such as a motor or electromagnet, the reverse electromotive force often causes arcing on the contacts, causing the contacts to burn and eventually causing circuit failure.

[0003] The existing solution is to connect "resistance-capacitance absorption circuit", "thermistor", "instantaneous voltage regulator" and other components in parallel at both ends of the switch or relay contact to absorb the reverse electromotive force, but these passive components have limited protection effects, or too high residual voltage, or limited absorption, or slow speed, etc., each with its own disadvantages. In view of the above defects, the present invention has made improvements. Summary of the invention

[0004] In order to overcome the shortcomings of the background technology, the present invention provides a reverse electromotive force active discharge protection circuit, which can actively extinguish arcs and solve the problem of damage to switch or relay contacts caused by the reverse electromotive force generated by the inductive device.

[0005] The technical solution adopted by the present invention is: a reverse electromotive force active discharge protection circuit, including a signal processing circuit, a discharge drive circuit, a discharge resistor and a polarity switching circuit, one end of the discharge resistor is electrically connected to the polarity switching circuit, and the other end is electrically connected to the discharge drive circuit, the polarity switching circuit and the signal processing circuit are both electrically connected to the discharge drive circuit, the polarity switching circuit is provided with two discharge interfaces for parallel DC loads, and the signal processing circuit outputs a load drive signal for controlling the DC load and a discharge control signal for controlling the discharge drive circuit.

[0006] Preferably, the polarity switching circuit adopts a rectifier circuit, and the signal processing circuit adopts a processor.

[0007] Preferably, the discharge drive circuit includes a first NMOS tube, a second resistor, a fourth resistor, a fifth resistor, a first capacitor, a voltage regulator and a photoelectric coupler, the positive output end of the rectifier circuit is electrically connected to one end of the discharge resistor, the negative output end is electrically connected to the S pole of the first NMOS tube, the D pole of the first NMOS tube and one end of the second resistor are electrically connected to the other end of the discharge resistor, the other end of the second resistor is electrically connected to the negative pole of the voltage regulator tube, one end of the fifth resistor and one end of the first capacitor are electrically connected to the G pole of the first NMOS tube, the positive pole of the voltage regulator tube, the other end of the fifth resistor and the other end of the first capacitor are electrically connected to the S pole of the first NMOS tube, the first input pin of the photoelectric coupler is electrically connected to one end of the fourth resistor, the other end of the fourth resistor is electrically connected to the output end of the processor, the second input pin of the photoelectric coupler is grounded, the first output pin of the photoelectric coupler is electrically connected to the negative pole of the voltage regulator tube, and the second output pin of the photoelectric coupler is electrically connected to the G pole of the first NMOS tube.

[0008] Preferably, the rectifier circuit adopts a rectifier bridge stack.

[0009] Preferably, the photoelectric coupler is LTV-357T.

[0010] An application circuit of the reverse electromotive force active discharge protection circuit based on the above technical solution, the application circuit also includes a load control circuit, the load control circuit includes an ordinary relay, the ordinary relay has a relay coil and a relay contact, the signal processing circuit outputs a load drive signal to turn on and off the relay coil, the two ends of the DC load are respectively electrically connected to the two discharge interfaces of the polarity switching circuit, and the DC load is also connected in series with the relay contact.

[0011] Preferably, the DC load is a high-voltage DC motor, and the load control circuit includes a first common relay and a second NMOS tube, the first common relay has a first relay coil and a first relay contact, the first relay contact is a normally open contact, one end of the first relay coil is connected to DC12V, and the other end is electrically connected to the D pole of the second NMOS tube, the S pole of the second NMOS tube is grounded, and the G pole of the second NMOS tube is electrically connected to the output end of the signal processing circuit, the positive terminal of the high-voltage DC motor is electrically connected to the positive pole of the DC220V power supply, the negative terminal of the high-voltage DC motor is electrically connected to one end of the first relay contact, and the other end of the first relay contact is electrically connected to the negative pole of the DC220V power supply.

[0012] An active arc extinguishing method of the reverse electromotive force active discharge protection circuit based on the above technical solution comprises the following steps:

[0013] (1) When the processor receives a load shutdown request from an external source, the processor outputs a discharge control signal;

[0014] (2) Delay, wait for the first NMOS tube to be turned on, after which the first NMOS tube, the discharge resistor, the rectifier circuit, and the DC load form a discharge loop;

[0015] (3) The processor outputs a load drive signal to control the switch or relay to turn off the load and delay waiting for the discharge to end;

[0016] (4) The processor stops outputting the discharge control signal, and the first NMOS tube is turned off to disconnect the discharge circuit, completing the load shutdown action.

[0017] In summary, the beneficial effects of the present invention are:

[0018] 1. The present invention incorporates a discharge resistor in advance on the load when the contact needs to be disconnected, and then disconnects the contact. The discharge resistor is removed after the reverse electromotive force is discharged to a safe voltage range or discharged. The above technical solution handles the reverse electromotive force that is harmful to the circuit in an active and early intervention manner, which can better meet the actual needs;

[0019] 2. The application circuit based on the reverse electromotive force active discharge protection circuit is designed to replace the high-voltage DC relay with a cheap ordinary relay adding the reverse electromotive force active discharge protection circuit, which can effectively save the actual installation space and reduce the cost, and is conducive to better meeting the actual needs;

[0020] 3. An active arc extinguishing method based on a reverse electromotive force active discharge protection circuit. This method handles the reverse electromotive force that is harmful to the circuit in an active and early intervention manner. Its advantage is that the reverse electromotive force can be completely discharged without residual pressure problems, and there is no speed problem due to early intervention.

[0021] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0023] Figure 1 is a circuit block diagram of the present invention;

[0024] Figure 2A circuit diagram of a first embodiment of an application circuit of the present invention;

[0025] Figure 3 is a circuit diagram of a second embodiment of the application circuit of the present invention;

[0026] Figure 4 A schematic diagram of a workflow of the present invention. DETAILED DESCRIPTION

[0027] The following will be combined with the embodiments of the present invention Figures 1 to 4 , the technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] In order to make the purpose, technical solution and advantages of the implementation of the present invention clearer, the technical solution in the embodiment of the present invention will be described in more detail below with reference to the accompanying drawings in the embodiment of the present invention.

[0029] like Figures 1 to 4 As shown, a reverse electromotive force active discharge protection circuit disclosed in this embodiment includes a signal processing circuit, a discharge drive circuit, a discharge resistor R1 and a polarity switching circuit, one end of the discharge resistor R1 is electrically connected to the polarity switching circuit, and the other end is electrically connected to the discharge drive circuit, the polarity switching circuit and the signal processing circuit are both electrically connected to the discharge drive circuit, the polarity switching circuit is provided with two discharge interfaces for parallel DC loads, and the signal processing circuit outputs a load drive signal for controlling the DC load and a discharge control signal for controlling the discharge drive circuit. In the above technical solution, the circuit is mainly composed of four parts: signal processing circuit, discharge drive circuit, discharge resistor R1 and polarity switching circuit. The signal processing circuit is responsible for outputting the load drive signal used to control the start and stop of the DC load, and is responsible for outputting the discharge control signal before the DC load is disconnected. The discharge drive circuit is controlled by the discharge control signal. After receiving the discharge control signal, the discharge resistor R1 is promptly connected in parallel to the DC load. The discharge resistor R1 is responsible for discharging the residual electric energy on the DC load to a safe voltage as soon as possible. The discharge resistor R1 can convert the residual electric energy into heat energy. The polarity switching circuit is used to switch the DC load of unknown polarity to the polarity required by the circuit. In specific implementation, the DC load is mainly inductive devices such as motors and electromagnets.

[0030] As a preferred technical solution, the polarity switching circuit adopts a rectifier circuit, and the signal processing circuit adopts a processor. The polarity switching circuit adopts a rectifier circuit to conveniently switch the DC load of unknown polarity to the polarity required by the circuit. The signal processing circuit adopts a processor. In specific implementation, the processor adopts a single-chip microcomputer, which receives control demand signals such as forward, reverse and stop of the motor from the outside, and then drives the motor control circuit to work according to the demand. When receiving the commutation or stop signal, it outputs a discharge control signal in advance to discharge the reverse electromotive force of the motor to reduce the arcing phenomenon of the relay caused by the reverse electromotive force. The processor belongs to the prior art and will not be described in detail here.

[0031] As a preferred technical solution, the discharge drive circuit includes a first NMOS tube Q1, a second resistor R2, a fourth resistor R4, a fifth resistor R5, a first capacitor C1, a voltage regulator tube D1 and a photoelectric coupler OP1, the positive output end of the rectifier circuit is electrically connected to one end of the discharge resistor R1, the negative output end is electrically connected to the S pole of the first NMOS tube Q1, the D pole of the first NMOS tube Q1 and one end of the second resistor R2 are electrically connected to the other end of the discharge resistor R1, the other end of the second resistor R2 is electrically connected to the negative electrode of the voltage regulator tube D1, one end of the fifth resistor R5 and one end of the first capacitor C1 are electrically connected to the negative electrode of the voltage regulator tube D1, and the positive output end of the rectifier circuit is electrically connected to the S pole of the first NMOS tube Q1. The first and second ends of the photoelectric coupler OP1 are electrically connected to the G pole of the first NMOS tube Q1, the positive pole of the voltage regulator tube D1, the other end of the fifth resistor R5 and the other end of the first capacitor C1 are electrically connected to the S pole of the first NMOS tube Q1, the first input pin of the photoelectric coupler OP1 is electrically connected to one end of the fourth resistor R4, the other end of the fourth resistor R4 is electrically connected to the output end of the processor, the second input pin of the photoelectric coupler OP1 is grounded, the first output pin of the photoelectric coupler OP1 is electrically connected to the negative pole of the voltage regulator tube D1, and the second output pin of the photoelectric coupler OP1 is electrically connected to the G pole of the first NMOS tube Q1. In the above technical solution, the first NMOS tube Q1 is a switch tube, which is used to connect the discharge resistor R1 to the discharge circuit for discharge; the second resistor R2 is a current limiting resistor, the voltage regulator tube D1 adopts a 10V voltage regulator tube D1, and the second resistor R2 and the voltage regulator tube D1 form a 10V voltage regulator circuit; the fourth resistor R4 is a current limiting resistor of the photoelectric coupler OP1, which is used to protect the photoelectric coupler OP1; the role of the fifth resistor R5 is to ensure the rapid shutdown of the first NMOS tube Q1; the first capacitor C1 plays a role in stabilizing the gate voltage of the first NMOS tube Q1; the photoelectric coupler OP1 plays a role in isolating a high and low voltage circuit, and controls the first NMOS tube Q1 to be turned on or off. The NMOS tube, resistor, capacitor, voltage regulator tube D1 and photoelectric coupler OP1 are all existing technologies and will not be described in detail here.

[0032] As a preferred technical solution, the rectifier circuit adopts a rectifier bridge stack BD1. The rectifier circuit adopts a rectifier bridge stack BD1, which is composed of four diodes and has four lead pins, and can well switch a DC load of unknown polarity to the polarity required by the circuit. The rectifier bridge stack BD1 belongs to the prior art and is not described in detail here.

[0033] As a preferred technical solution, the photoelectric coupler OP1 adopts LTV-357T. In the specific implementation, the photoelectric coupler OP1 includes but is not limited to adopting LTV-357T, which can well play the role of optical coupling isolation of high and low voltage circuits, and can control the first NMOS tube Q1 to conduct when the processor outputs a discharge control signal, thereby forming a discharge loop. The LTV-357T belongs to the prior art and will not be further explained here.

[0034] An application circuit based on a reverse electromotive force active discharge protection circuit, the application circuit adds a load control circuit on the basis of the reverse electromotive force active discharge protection circuit, the load control circuit includes an ordinary relay, the ordinary relay has a relay coil and a relay contact, the signal processing circuit outputs a load drive signal to turn on and off the relay coil, the two ends of the DC load are respectively electrically connected to the two discharge interfaces of the polarity switching circuit, and the DC load is also connected in series with the relay contact. The reverse electromotive force active discharge protection circuit is an active arc extinguishing circuit, the load control circuit uses an ordinary relay to realize the shutdown of the DC load, when the ordinary relay shuts off the power supply of the DC load, the reverse electromotive force often causes arcing on the contact, causing the contact to burn, which is easy to cause circuit failure, by applying the reverse electromotive force active discharge protection circuit, this active arc extinguishing circuit, can be timely incorporated into the DC load before the DC load is shut down, the discharge resistor R1 can discharge the reverse electromotive force to a safe voltage range, so that it can effectively play an active arc extinguishing role, which is conducive to better protection of the circuit. The design of the above application circuit is to replace the high-voltage DC relay with a cheap common relay and a reverse electromotive force active discharge protection circuit, which can effectively save the actual installation space and reduce the cost. The above high-voltage DC relay uses permanent magnet arc extinguishing technology or inert gas to extinguish the arc, which is large in size and high in cost. The above common relay and high-voltage DC relay are both existing technologies and are not described in detail here.

[0035] As an embodiment of the above-mentioned application circuit, the DC load is a high-voltage DC motor, and the load control circuit includes a first common relay J1 and a second NMOS tube Q2. The first common relay J1 has a first relay coil and a first relay contact. The first relay contact is a normally open contact. One end of the first relay coil is connected to DC12V, and the other end is electrically connected to the D pole of the second NMOS tube Q2. The S pole of the second NMOS tube Q2 is grounded, and the G pole of the second NMOS tube Q2 is electrically connected to the output end of the signal processing circuit. The positive terminal of the high-voltage DC motor is electrically connected to the positive pole of the DC220V power supply, and the negative terminal of the high-voltage DC motor is electrically connected to one end of the first relay contact, and the other end of the first relay contact is electrically connected to the negative pole of the DC220V power supply. This embodiment is used to protect the high-voltage DC motor start-stop control circuit. The processor receives the motor start-stop control signal from the outside. When the motor needs to be started, the processor sends a load drive signal to turn on the second NMOS tube Q2. After the second NMOS tube Q2 is turned on, the first relay coil is energized. When the coil is energized, the first relay contact is closed to connect the negative terminal of the high-voltage DC motor to the negative pole of the DC220V power supply. At this time, the motor starts to run. When the processor receives an external motor stop request, the processor outputs a discharge control signal to turn on the first NMOS tube Q1. The first NMOS tube Q1 After being turned on, the first NMOS tube Q1, the discharge resistor R1, the rectifier bridge stack BD1, and the motor form a discharge circuit, which can eliminate the damage to the relay contacts caused by arcing. Then, the processor sends a load drive signal to cut off the second NMOS tube Q2. When the second NMOS tube Q2 is cut off, the first relay coil is powered off. When the coil is powered off, the first relay contact is disconnected. In this way, the negative terminal of the high-voltage DC motor is disconnected from the negative pole of the DC220V power supply, and the motor stops. Due to the addition of an active arc extinguishing circuit, the discharge resistor R1 can completely discharge the reverse electromotive force, which can better protect the circuit. The high-voltage DC motor described belongs to the prior art and will not be described in detail here. For details of this embodiment, please refer to Figure 2 .

[0036] The present invention also provides another embodiment of the above-mentioned application circuit, which is used to protect the forward and reverse control circuit of the high-voltage DC motor. During implementation, the load control circuit uses two ordinary relays to realize the forward and reverse control. The two ordinary relays are the second ordinary relay J2 and the third ordinary relay J3. The relay coils of the second ordinary relay J2 and the third ordinary relay J3 are electrically connected to the output end of the processor. The processor receives the motor start and stop and steering control signals from the outside, and outputs the load drive signal to the second ordinary relay J2 and the third ordinary relay J3 respectively. Due to the addition of the active arc extinguishing circuit, in the process of controlling the high-voltage DC motor to realize forward and reverse rotation, the discharge resistor R1 can completely discharge the reverse electromotive force generated when the motor stops, so as to better protect the circuit. This embodiment can be specifically referred to Figure 3 .

[0037] This embodiment takes motor control as an example to provide an active arc extinguishing method based on a reverse electromotive force active discharge protection circuit, comprising the following steps:

[0038] (1) When the processor receives a request to stop the external motor, the processor outputs a discharge control signal to the discharge drive circuit;

[0039] (2) Delay, wait for the first NMOS tube Q1 to be turned on, after which the first NMOS tube Q1, the discharge resistor R1, the rectifier bridge stack BD1, and the motor form a discharge circuit, eliminating the damage to the relay contacts caused by the arc;

[0040] (3) The processor outputs a load drive signal to control the relay to disconnect the contacts and delay waiting for the discharge to end;

[0041] (4) The processor stops outputting the discharge control signal, and the first NMOS tube Q1 is turned off to disconnect the discharge circuit, completing the motor stop action.

[0042] The present invention handles the reverse electromotive force that is harmful to the circuit in an active and advance intervention manner. The specific steps are to incorporate a discharge resistor R1 into the load in advance when the contacts need to be disconnected, and then disconnect the contacts, and wait for the discharge resistor R1 to discharge the reverse electromotive force to a safe voltage range, or remove the discharge resistor R1 after it is discharged. The above steps are all completed by the pre-stored program code of the single-chip computer. In specific implementation, the discharge resistor R1 can be connected to the discharge circuit in a continuous or intermittent manner to meet different discharge speed requirements. The advantage of this method is that the reverse electromotive force can be completely discharged, there is no residual pressure problem, and there is no speed problem due to advance intervention.

[0043] Technical personnel should note that: Although the present invention has been described according to the above specific implementation methods, the inventive concept of the present invention is not limited to this invention, and any modification using the inventive concept will be included in the scope of protection of this patent right.

Claims

1. A reverse electromotive force active discharge protection circuit, characterized in that: The invention comprises a signal processing circuit, a discharge driving circuit, a discharge resistor and a polarity switching circuit, wherein one end of the discharge resistor is electrically connected to the polarity switching circuit, and the other end is electrically connected to the discharge driving circuit, the polarity switching circuit and the signal processing circuit are both electrically connected to the discharge driving circuit, the polarity switching circuit is provided with two discharge interfaces for parallel DC loads, the signal processing circuit outputs a load driving signal for controlling the DC load and a discharge control signal for controlling the discharge driving circuit, the polarity switching circuit adopts a rectifier circuit, the signal processing circuit adopts a processor, the discharge driving circuit comprises a first NMOS tube, a second resistor, a fourth resistor, a fifth resistor, a first capacitor, a voltage regulator tube and a photoelectric coupler, the positive output end of the rectifier circuit is electrically connected to one end of the discharge resistor, and the negative output end The S pole of the first NMOS tube is electrically connected, the D pole of the first NMOS tube and one end of the second resistor are electrically connected to the other end of the discharge resistor, the other end of the second resistor is electrically connected to the negative pole of the voltage regulator tube, one end of the fifth resistor and one end of the first capacitor are electrically connected to the G pole of the first NMOS tube, the positive pole of the voltage regulator tube, the other end of the fifth resistor and the other end of the first capacitor are electrically connected to the S pole of the first NMOS tube, the first input pin of the photocoupler is electrically connected to one end of the fourth resistor, the other end of the fourth resistor is electrically connected to the output end of the processor, the second input pin of the photocoupler is grounded, the first output pin of the photocoupler is electrically connected to the negative pole of the voltage regulator tube, and the second output pin of the photocoupler is electrically connected to the G pole of the first NMOS tube.

2. The reverse electromotive force active discharge protection circuit according to claim 1, characterized in that: The rectifier circuit adopts a rectifier bridge stack.

3. The reverse electromotive force active discharge protection circuit according to claim 2, characterized in that: The photoelectric coupler is LTV-357T.

4. An application circuit based on the reverse electromotive force active discharge protection circuit according to any one of claims 1 to 3, characterized in that: It also includes a load control circuit, which includes an ordinary relay, the ordinary relay has a relay coil and a relay contact, the signal processing circuit outputs a load drive signal to turn on and off the relay coil, the two ends of the DC load are respectively electrically connected to the two discharge interfaces of the polarity switching circuit, and the DC load is also connected in series with the relay contact.

5. An application circuit according to claim 4, characterized in that: The DC load is a high-voltage DC motor, and the load control circuit includes a first common relay and a second NMOS tube. The first common relay has a first relay coil and a first relay contact. The first relay contact is a normally open contact. One end of the first relay coil is connected to DC12V, and the other end is electrically connected to the D pole of the second NMOS tube. The S pole of the second NMOS tube is grounded, and the G pole of the second NMOS tube is electrically connected to the output end of the signal processing circuit. The positive terminal of the high-voltage DC motor is electrically connected to the positive pole of the DC220V power supply, the negative terminal of the high-voltage DC motor is electrically connected to one end of the first relay contact, and the other end of the first relay contact is electrically connected to the negative pole of the DC220V power supply.

6. An active arc extinguishing method based on the reverse electromotive force active discharge protection circuit according to any one of claims 1 to 3, characterized in that: The following steps are involved: (1) When the processor receives a load shutdown request from an external source, the processor outputs a discharge control signal; (2) Delay, wait for the first NMOS tube to be turned on, after which the first NMOS tube, the discharge resistor, the rectifier circuit, and the DC load form a discharge loop; (3) The processor outputs a load drive signal to control the switch or relay to turn off the load and delay waiting for the discharge to end; (4) The processor stops outputting the discharge control signal, and the first NMOS tube is turned off to disconnect the discharge circuit, completing the load shutdown action.

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