A motor speed control system

Abstract

The present invention discloses a motor speed regulation system. The pulse signal generation circuit in this application can generate a pulse signal corresponding to the target speed set by the user, and the solid-state relay can be turned on and off under the control of the pulse signal, so as to control the input voltage of the motor to be adjusted, and the motor speed can be controlled to the target speed. The speed selection device, the pulse signal generation circuit, and the solid-state relay circuit can all be composed of conventional electronic components. Therefore, the volume of the motor speed regulation system in this application is usually much smaller than that of the reactor, occupying less space and being convenient for transportation. In addition, the solid-state relay itself can achieve isolation between the control end and the load end, preventing the large current of the motor from affecting the control circuit, and has high safety.

Description

Technical Field

[0001] The present invention relates to the field of electric motors, and particularly to an electric motor speed regulation system. Background Art

[0002] In many scenarios, the speed of an electric motor needs to be adjusted through an electric motor speed regulation system. For example, the moving mechanism on some rehabilitation devices is controlled by the rotating shaft of the electric motor. By adjusting the speed of the electric motor, the movement speed of the moving mechanism can be controlled to meet the rehabilitation training needs of different patients. However, there is no mature electric motor speed regulation system in the prior art. Usually, the resistance value of the reactor set in the power supply circuit of the electric motor is adjusted to regulate the speed of the electric motor. However, the reactor is usually huge in volume, occupies a large space and is not convenient for transportation.

[0003] Therefore, how to provide a solution to the above technical problems is an issue that those skilled in the art need to solve currently. Summary of the Invention

[0004] The object of the present invention is to provide an electric motor speed regulation system that occupies a small space and is convenient for transportation. In addition, the solid-state relay itself can isolate the control end and the load end, preventing the large current of the electric motor from affecting the control circuit, and has high safety.

[0005] To solve the above technical problems, the present invention provides an electric motor speed regulation system, including:

[0006] A speed selection device for setting a target speed through it;

[0007] A pulse signal generation circuit connected to the speed selection device for generating a pulse signal corresponding to the target speed;

[0008] A solid-state relay circuit connected in series to the power supply circuit of the motor to be adjusted, with its control end connected to the pulse signal generation circuit, for performing on-off changes under the control of the pulse signal so as to control the input voltage of the motor to be adjusted.

[0009] Preferably, the pulse signal generation circuit is a monostable trigger circuit.

[0010] Preferably, the electric motor speed regulation system further includes:

[0011] A feedback voltage acquisition circuit arranged on the feedback line of the motor to be adjusted and connected to the monostable trigger circuit for sampling the voltage signal of the feedback voltage of the motor to be adjusted;

[0012] Then the monostable trigger circuit is further used to correct the pulse signal output by itself according to the voltage signal of the feedback voltage.

[0013] Preferably, the monostable trigger circuit includes a timer integrated circuit and its peripheral circuits.

[0014] Preferably, the motor speed regulation system further includes:

[0015] An opto-isolation circuit with its input terminal connected to the output terminal of the pulse signal generation circuit and its output terminal connected to the solid-state relay circuit, which is used to isolate digital signals and analog signals.

[0016] Preferably, the solid-state relay circuit includes:

[0017] A first solid-state relay sub-circuit with its output terminal connected to the forward rotation line of the motor to be adjusted, which is used to make on-off changes under the control of the pulse signal so as to control the input voltage for the forward rotation of the motor to be adjusted;

[0018] A second solid-state relay sub-circuit with its output terminal connected to the reverse rotation line of the motor to be adjusted, which is used to make on-off changes under the control of the pulse signal so as to control the input voltage for the reverse rotation of the motor to be adjusted;

[0019] The motor speed regulation system further includes:

[0020] A forward and reverse selection switch with its first terminal connected to the output terminal of the opto-isolation circuit and its second terminal respectively connected to the input terminals of the first solid-state relay sub-circuit and the second solid-state relay sub-circuit, which is used to connect the pulse signal to the first solid-state relay sub-circuit or the second solid-state relay sub-circuit through it.

[0021] Preferably, the motor speed regulation system further includes a spike and glitch elimination circuit with its input terminal connected to the forward and reverse selection switch and its output terminal respectively connected to the input terminals of the first solid-state relay sub-circuit and the second solid-state relay sub-circuit, which is used to eliminate spikes and glitches in the pulse signal.

[0022] Preferably, the spike and glitch elimination circuit is a NAND gate spike elimination circuit.

[0023] Preferably, the speed selection device is specifically a speed selection device based on a multiplexer.

[0024] Preferably, the speed selection device based on a multiplexer includes a variable resistor, a multiplexer, a power supply, and a single-pole double-throw switch;

[0025] The first end of the adjustable resistor is grounded, the second end of the adjustable resistor is connected to the input end of the multiplexer switch, the output end of the multiplexer switch is connected to the solid-state relay circuit, the power supply end of the multiplexer switch is respectively connected to the power supply and the first end of the single-pole double-throw switch, the fixed end of the single-pole double-throw switch is connected to the enable end of the multiplexer switch, and the second end of the single-pole double-throw switch is grounded.

[0026] The present invention provides a motor speed regulation system. The pulse signal generation circuit in this application can generate a pulse signal corresponding to the target speed set by the user, and the solid-state relay can be turned on and off under the control of the pulse signal, so as to control the input voltage of the motor to be adjusted, and the motor speed can be controlled to the target speed. The speed selection device, the pulse signal generation circuit and the solid-state relay circuit can all be composed of conventional electronic components. Therefore, the volume of the motor speed regulation system in this application is usually much smaller than that of the reactor, occupying less space and being convenient for transportation. In addition, the solid-state relay itself can realize the isolation between the control end and the load end, preventing the large current of the motor from affecting the control circuit, and has high safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the prior art and the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0028] Figure 1 It is a schematic structural diagram of a motor speed regulation system provided by the present invention;

[0029] Figure 2 It is a schematic structural diagram of a pulse signal generation circuit provided by the present invention;

[0030] Figure 3 It is a schematic structural diagram of a feedback voltage acquisition circuit provided by the present invention;

[0031] Figure 4 It is a schematic structural diagram of an optocoupler isolation circuit provided by the present invention;

[0032] Figure 5 It is a schematic structural diagram of a NAND gate spike elimination circuit provided by the present invention;

[0033] Figure 6 It is a schematic structural diagram of a speed selection device provided by the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] The core of the present invention is to provide a motor speed regulation system, which occupies less space and is convenient for transportation. In addition, the solid-state relay itself can isolate the control end and the load end, preventing the large current of the motor from affecting the control circuit, and has relatively high safety.

[0035] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0036] Please refer to Figure 1 , Figure 1 which is a schematic structural diagram of a motor speed regulation system provided by the present invention. The motor speed regulation system includes:

[0037] A speed selection device 1 for setting a target speed through it;

[0038] A pulse signal generation circuit 2 connected to the speed selection device 1 for generating a pulse signal corresponding to the target speed;

[0039] A solid-state relay circuit 3 connected in series to the power supply circuit of the motor to be adjusted, with its control end connected to the pulse signal generation circuit 2, for performing on-off changes under the control of the pulse signal so as to control the input voltage of the motor to be adjusted.

[0040] Specifically, considering the technical problems in the above background art, in order to avoid using a large-volume reactor, a new motor speed regulation system is provided in this application. Its core principle is to control the on-off of the solid-state relay circuit 3 to control the input voltage of the motor to be adjusted, thereby realizing the adjustment of the motor speed. Generally, the total volume of all components in this application is also smaller than that of the reactor, reducing the cost of the motor speed regulation system, reducing the occupied space and facilitating transportation. Moreover, considering that the motor is a large-current load, in order to prevent the large-current load from affecting and damaging the control circuit, in the embodiments of the present invention, the ability of the solid-state relay itself to isolate the control end and the load end is utilized, which can prevent the large current of the motor from affecting the control circuit and improve the safety of the motor speed regulation system.

[0041] Specifically, the pulse signal generation circuit 2 can generate a pulse signal for driving the solid-state relay circuit 3 to work, and when generating the pulse signal, it needs to be controlled by an analog signal corresponding to the target speed output by the speed selection device 1, and the user can set the target speed through the speed selection device 1.

[0042] Among them, the target rotation speed can be arbitrarily set through the rotation speed selection device 1, and the pulse signal generation circuit 2 can also generate a pulse signal corresponding to the target rotation speed to drive the solid-state relay circuit 3, so as to realize the regulation of voltage and rotation speed by controlling the duty cycle of the solid-state relay circuit 3.

[0043] Specifically, the motor to be regulated in the embodiment of the present invention can be various types of single-phase asynchronous motors. For example, it can be a single-phase asynchronous reduction motor, which can achieve a large torque output. The embodiment of the present invention does not make any limitation here.

[0044] The present invention provides a motor speed regulation system. The pulse signal generation circuit in the present application can generate a pulse signal corresponding to the target rotation speed set by the user, and the solid-state relay can be turned on and off under the control of the pulse signal, so as to control the input voltage of the motor to be regulated, and the motor speed can be controlled to the target rotation speed. The rotation speed selection device, the pulse signal generation circuit and the solid-state relay circuit can all be composed of conventional electronic components. Therefore, the volume of the motor speed regulation system in the present application is usually much smaller than that of the reactor, occupying less space and being convenient for transportation. In addition, the solid-state relay itself can realize the isolation between the control end and the load end, preventing the large current of the motor from affecting the control circuit, and having high safety.

[0045] For better illustration of the embodiments of the present invention, please refer to Figure 2 , Figure 2 which is a schematic structural diagram of a pulse signal generation circuit 2 provided by the present invention. On the basis of the above embodiments:

[0046] As a preferred embodiment, the pulse signal generation circuit 2 is a monostable trigger circuit.

[0047] Specifically, the monostable trigger circuit has the advantages of small volume, low cost and long service life. It can be composed of an NE555 chip and its peripheral circuit, and outputs a stable pulse signal under the participation of the analog signal A corresponding to the target rotation speed.

[0048] Of course, in addition to the monostable trigger circuit, the pulse signal generation circuit 2 can also be of other various types, and the embodiments of the present invention do not make any limitation here.

[0049] For better illustration of the embodiments of the present invention, please refer to Figure 3 , Figure 3 which is a schematic structural diagram of a feedback voltage acquisition circuit provided by the present invention. As a preferred embodiment, the motor speed regulation system further includes:

[0050] A feedback voltage acquisition circuit that is disposed on the feedback line of the motor to be adjusted and connected to the monostable trigger circuit, and is used to sample the voltage signal of the feedback voltage of the motor to be adjusted;

[0051] The monostable trigger circuit is further used to correct the pulse signal output by itself according to the voltage signal of the feedback voltage.

[0052] Specifically, in order to improve the accuracy of the output pulse signal, the monostable trigger circuit in the embodiment of the present invention can also correct the pulse signal output by itself based on the voltage signal of the feedback AC voltage output by the motor feedback line, realizing the closed-loop control of the pulse signal and improving the accuracy of the pulse signal and the accuracy of speed regulation.

[0053] Specifically, in Figure 3 , the feedback voltage acquisition circuit can rectify the feedback AC voltage and then sample it to obtain the sampled voltage signal B, and correct the pulse signal through B.

[0054] Of course, in addition to Figure 3 the specific structure of the feedback voltage acquisition circuit provided in

[0055] the feedback voltage acquisition circuit can also be of many other specific types, which are not limited in the embodiment of the present invention.

[0056] As a preferred embodiment, the monostable trigger circuit includes a time-base integrated circuit and its peripheral circuits. Figure 2 Specifically, the monostable trigger circuit with a time-base integrated circuit as the core has the advantages of simple structure, small volume and low cost. The time-base integrated circuit can be

[0057] the NE555D chip shown in

[0058] etc., which are not limited in the embodiment of the present invention. Figure 4 Figure 4 For better illustration of the embodiment of the present invention, please refer to

[0059] FIG.

[0060] which is a schematic structural diagram of an opto-coupler isolation circuit provided by the present invention. As a preferred embodiment, the motor speed regulation system further includes: An opto-coupler isolation circuit with an input end connected to the output end of the pulse signal generation circuit 2 and an output end connected to the solid-state relay circuit 3, which is used to isolate digital signals and analog signals.Specifically, considering that a part of the digital signals output by the pulse signal generation circuit 2 are signals after AC rectification, an optocoupler isolation circuit can be used for isolation in this application, and the optocoupler isolation circuit has the characteristics of low interference and good stability.

[0061] Of course, in addition to the optocoupler isolation circuit, other types of isolation circuits can also be used for isolation, and the embodiments of the present invention do not limit this here.

[0062] Specifically, Figure 4 the optocoupler isolation circuit in Figure 4 is an optocoupler isolation circuit with an optocoupler U7 as the core,

[0063] Of course, in addition to Figure 4 the optocoupler isolation circuit in

[0064] As a preferred embodiment, the solid-state relay circuit 3 includes:

[0065] a first solid-state relay sub-circuit with its output terminal connected to the forward rotation line of the motor to be adjusted, which is used to turn on and off under the control of the pulse signal so as to control the input voltage for the forward rotation of the motor to be adjusted;

[0066] a second solid-state relay sub-circuit with its output terminal connected to the reverse rotation line of the motor to be adjusted, which is used to turn on and off under the control of the pulse signal so as to control the input voltage for the reverse rotation of the motor to be adjusted;

[0067] This motor speed regulation system further includes:

[0068] a forward and reverse selection switch with its first end connected to the output terminal of the optocoupler isolation circuit and its second end respectively connected to the input terminals of the first solid-state relay sub-circuit and the second solid-state relay sub-circuit, which is used to connect the pulse signal to the first solid-state relay sub-circuit or the second solid-state relay sub-circuit through it.

[0069] Specifically, considering that some motors have both forward rotation and reverse rotation requirements during specific use, the solid-state relay circuit 3 of this application is specifically provided with a first solid-state relay sub-circuit and a second solid-state relay sub-circuit, which can be respectively used to control the power supply of the forward and reverse incoming lines, so as to achieve forward rotation speed regulation and reverse rotation speed regulation, and meet the speed regulation requirements of scenarios with forward and reverse rotation requirements.

[0070] Specifically, through the forward and reverse selection switch, it is possible to select whether to connect the pulse signal to the first solid-state relay sub-circuit or the second solid-state relay sub-circuit, so as to achieve the selection of forward and reverse rotation.

[0071] Among them, the forward and reverse selection switch can be of various types. For example, it can be a single-pole double-throw switch, etc. The embodiments of the present invention do not limit this here.

[0072] As a preferred embodiment, the motor speed regulation system further includes a spike and glitch elimination circuit with an input end connected to the forward and reverse selection switch and output ends respectively connected to the input ends of the first solid-state relay sub-circuit and the second solid-state relay sub-circuit, which is used to eliminate spikes and glitches in the pulse signal.

[0073] Specifically, considering that due to some electromagnetic interference and other reasons, the pulse signal may contain some spikes and glitches, which is not conducive to the stable operation of the circuit. Therefore, in the embodiments of the present invention, a spike and glitch elimination circuit is provided to eliminate the spikes and glitches in the pulse signal, which can make the circuit operation more stable.

[0074] For better illustration of the embodiments of the present invention, please refer to Figure 5 , Figure 5 which is a schematic structural diagram of a NAND gate spike elimination circuit provided by the present invention. As a preferred embodiment, the spike and glitch elimination circuit is a NAND gate spike elimination circuit.

[0075] Specifically, in Figure 5 , the switch S2 is the above-mentioned forward and reverse selection switch, and U5 is the above-mentioned NAND gate spike elimination circuit. The NAND gate elimination circuit can make the pulse signal reverse twice to smooth the pulse signal, improving the stability of the pulse signal. Figure 5 The NAND gate spike elimination circuit in has the advantages of simple structure, small volume and low cost.

[0076] Of course, in addition to the specific structure in Figure 5 , the NAND gate spike elimination circuit can also be other various specific structures. The embodiments of the present invention do not limit this here.

[0077] Specifically, the NAND gate spike and glitch elimination circuit has the advantages of simple structure and low cost.

[0078] Of course, in addition to the NAND gate spike elimination circuit, the spike and glitch elimination circuit can also be of other various types. The embodiments of the present invention do not limit this here.

[0079] For better illustration of the embodiments of the present invention, please refer to Figure 6 , Figure 6 which is a schematic structural diagram of a speed selection device 1 provided by the present invention. As a preferred embodiment, the speed selection device 1 is specifically a speed selection device 1 based on a multiplexer.

[0080] Specifically, the multiplexer has the advantages of small volume, low cost and long service life.

[0081] Of course, in addition to the rotation speed selection device 1 based on the multiplexer, the rotation speed selection device 1 can also be of many other types, which are not limited in the embodiments of the present invention.

[0082] As a preferred embodiment, the rotation speed selection device 1 based on the multiplexer includes a variable resistor, a multiplexer, a power supply, and a single-pole double-throw switch;

[0083] The first end of the variable resistor is grounded, the second end of the variable resistor is connected to the input end of the multiplexer, the output end of the multiplexer is connected to the solid-state relay circuit 3, the power supply end of the multiplexer is respectively connected to the power supply and the first end of the single-pole double-throw switch, the fixed end of the single-pole double-throw switch is connected to the enable end of the multiplexer, and the second end of the single-pole double-throw switch is grounded.

[0084] Specifically, Figure 6 The multiplexer in Figure 6 is a single-ended 8-channel multiplexer CD4051. When INH (pin 6) is at a high level, the input-output channel switch is closed, and no output appears at pin 3 regardless of whether the logic states of the three pins C (pin 9), B (pin 10), and A (pin 11) are high or low. When INH (pin 6) is at a low level, the input-output channel switch is open, and according to the high and low levels of the three pins C (pin 9), B (pin 10), and A (pin 11), a judgment is made according to the logic truth table, and the input value of the corresponding input channel will be transmitted to pin 3.

[0085] Through Figure 6 The rotation speed selection device 1 in Figure 6 can perform two mode selections: stepless speed regulation mode and stepped speed regulation mode. Among them, in the stepless speed regulation mode, the SA, SB, and SC switches are set to any level combination. First, the corresponding input channel is determined according to the logic truth table. Secondly, the variable resistor (one corresponding to P1~P8) of this channel is welded, and the ordinary resistor is not welded. Finally, the variable resistors and ordinary resistors of the other 7 input channels are not welded. At this time, it is the stepless speed regulation mode of adjusting only one variable resistor. In the stepped speed regulation mode, first, all the variable resistors (P1~P8) are welded only; secondly, the levels of the three switches SA, SB, and SC are set, and 8 speed gears required according to one's own needs are debugged; then the resistance values of P1~P8 are measured, and resistors with the same equivalent size are welded at the positions of 16 ordinary resistors (RN1~RN8, RQ1~RQ8); finally, all the variable resistors are removed. At this time, it is the stepped speed regulation mode with 8 gears. When selecting a gear, the levels of the switch S1 and the three switches SA, SB, and SC are set, and then a matching selection is made according to the logic truth table of CD4051.

[0086] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. For the same or similar parts among the various embodiments, reference can be made to each other. It should also be noted that in this specification, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variation thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising an..." does not exclude the presence of additional identical elements in the process, method, article or device comprising the element.

[0087] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A motor speed regulation system, characterized in that, Comprising: A rotation speed selection device for setting a target rotation speed through it; A pulse signal generation circuit connected to the rotation speed selection device for generating a pulse signal corresponding to the target rotation speed; A solid-state relay circuit connected in series to the power supply circuit of the motor to be adjusted, with its control end connected to the pulse signal generation circuit, for performing on-off changes under the control of the pulse signal so as to control the input voltage of the motor to be adjusted; The rotation speed selection device is specifically a rotation speed selection device based on a multiplexer; The rotation speed selection device based on a multiplexer includes a variable resistor, a multiplexer, a power supply, and a single-pole double-throw switch; The first end of the variable resistor is grounded, the second end of the variable resistor is connected to the input end of the multiplexer, the output end of the multiplexer is connected to the solid-state relay circuit, the power supply end of the multiplexer is respectively connected to the power supply and the first end of the single-pole double-throw switch, the fixed end of the single-pole double-throw switch is connected to the enable end of the multiplexer, and the second end of the single-pole double-throw switch is grounded; The multiplexer is a single-ended 8-channel multiplexer, the variable resistor includes a total of eight adjustable sub-resistors P1 - P8, the first end of the adjustable sub-resistor is grounded, and the second end is connected to the input channels of the multiplexer one by one; The rotation speed selection device based on a multiplexer further includes: a first switch SA, a second switch SB, a third switch SC, ordinary resistors RN1 - RN8, and RQ1 - RQ8; The first switch SA is connected to the control end A of the multiplexer, the second switch SB is connected to the control end B of the multiplexer, the third switch SC is connected to the control end C of the multiplexer, the ordinary resistors RN1 - RN8 and RQ1 - RQ8 with the same serial number are connected in series, and the first end of any two serially connected ordinary resistors is grounded, and the second end is connected to the input channel of the multiplexer with the same serial number; The rotation speed selection device performs two mode selections: stepless speed regulation mode and stepped speed regulation mode.

2. The motor speed regulation system according to claim 1, wherein The pulse signal generation circuit is a monostable trigger circuit.

3. The motor speed regulation system according to claim 2, wherein This motor speed regulation system further includes: A feedback voltage acquisition circuit disposed on the feedback line of the motor to be adjusted and connected to the monostable trigger circuit for sampling the voltage signal of the feedback voltage of the motor to be adjusted; Then the monostable trigger circuit is further used to correct the pulse signal output by itself according to the voltage signal of the feedback voltage.

4. The motor speed regulation system according to claim 2, wherein The monostable trigger circuit includes a time-base integrated circuit and its peripheral circuit.

5. The motor speed control system according to claim 3, characterized in that, This motor speed regulation system further includes: An opto-isolation circuit with its input end connected to the output end of the pulse signal generation circuit and its output end connected to the solid-state relay circuit for isolating digital signals and analog signals.

6. The motor speed regulation system according to claim 5, wherein The solid-state relay circuit includes: A first solid-state relay sub-circuit with its output end connected to the forward rotation line of the motor to be adjusted, for performing on-off changes under the control of the pulse signal so as to control the input voltage for the forward rotation of the motor to be adjusted; A second solid-state relay sub-circuit with its output terminal connected to the reverse rotation wire of the motor to be adjusted, which is used to perform on-off changes under the control of the pulse signal so as to control the input voltage for the reverse rotation of the motor to be adjusted; The motor speed regulation system further includes: A forward and reverse selection switch with its first terminal connected to the output terminal of the opto-isolator circuit and its second terminal respectively connected to the input terminals of the first solid-state relay sub-circuit and the second solid-state relay sub-circuit, which is used to connect the pulse signal to the first solid-state relay sub-circuit or the second solid-state relay sub-circuit through it.

7. The motor speed regulation system according to claim 6, characterized in that, The motor speed regulation system further includes a spike and glitch elimination circuit with its input terminal connected to the forward and reverse selection switch and its output terminals respectively connected to the input terminals of the first solid-state relay sub-circuit and the second solid-state relay sub-circuit, which is used to eliminate spikes and glitches in the pulse signal.

8. The motor speed control system according to claim 7, characterized in that, The spike and glitch elimination circuit is a NAND gate spike elimination circuit.

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