Bidirectional high-speed pulse input circuit and device with current-limiting protection function

Abstract

The invention discloses a bidirectional high-speed pulse input circuit and device with a current-limiting protection function, and the circuit comprises a pre-stage anti-interference rectifier bridge circuit which is used for receiving a source-type or drain-type high-speed pulse signal, and carrying out the rectification processing of the received high-speed pulse signal; the high-speed optocoupler isolation acquisition and transmission circuit is connected with the preceding-stage anti-interference rectifier bridge circuit and is used for acquiring an external high-speed pulse signal, converting the external high-speed pulse signal into a current signal and shunting the current signal; the current-limiting protection circuit is used for carrying out current-limiting protection on the whole circuit when a high-level high-speed pulse signal is externally input; and the post-stage level comparator circuit is connected with the high-speed optocoupler isolation acquisition and transmission circuit and is used for shaping, filtering and outputting the high-speed pulse signals, so that the defect that the existing digital quantity input circuit cannot acquire bidirectional high-speed pulse signals is overcome, the digital quantity input circuit has current-limiting protection and relatively high anti-interference capability, and more complicated industrial field requirements are met.

Description

Technical Field

[0001] The present invention relates to the technical field of sampling circuits, and in particular to a bidirectional high-speed pulse input circuit and a device with a current limiting protection function. Background Art

[0002] In common industrial control, the control protection of digital switch quantity and pulse quantity signal is to add fuses, thermistors and other means in series in the input channel. If they fail, they need to be replaced. It is very troublesome to replace and repair the on-site control, especially when there are multiple points and multiple channels of input, there will be a lot of heat loss, and the current limiting protection of multiple channels is very important. Conventional industrial sites require both source access and drain access. Conventional bidirectional optocoupler isolators can only collect and transmit low-speed pulse signals.

[0003] The patent with publication number CN205788001U and name "A digital input circuit overcurrent protection circuit" proposes a digital input circuit overcurrent protection circuit, which provides a transistor protection circuit directly connected in front of the digital input circuit. Its defects are: the current limiting resistor connected in series with the channel will divide the voltage and affect the signal input threshold standard required in the actual field, and can only connect to unidirectional signals, without solving the problem of connecting both source and drain types.

[0004] The publication number is CN209545415U, and the name is a wide voltage digital quantity input interface circuit. A wide voltage digital quantity input interface circuit is proposed. Its defects are: the circuit has the obvious disadvantage of being unable to distinguish the high and low states of the voltage of ordinary digital quantity signals input in industry, the PLC cannot realize logical control, and it is even more unable to collect high-speed pulse signals.

[0005] The publication number is CN216596001U, and the name is a digital quantity input circuit and device. The proposed digital quantity input circuit and device have the following defects: only a method for limiting the loop circuit is provided, and the subsequent circuit has a trigger inverter and shift register components. First, the cost of use is higher, and second, there is a level delay, and high-speed pulse signals cannot be collected.

[0006] In view of the above shortcomings and considerations, it is necessary to propose a design scheme for collecting and transmitting high-speed pulse signals, which can be effectively applied to multi-channel current limiting protection when transmitting high levels, and prevent loss when transmitting high-speed pulse signals to ensure signal quality. Summary of the invention

[0007] The purpose of the present invention is to provide a bidirectional high-speed pulse input circuit and device with current limiting protection function, which solves the defect that the existing digital input circuit cannot collect bidirectional high-speed pulse signals, and also has current limiting protection and strong anti-interference ability, thus meeting more complex industrial site needs.

[0008] The present invention provides a bidirectional high-speed pulse input circuit with a current limiting protection function, comprising a front-stage anti-interference rectifier bridge circuit, a high-speed optical coupling isolation acquisition transmission circuit, a current limiting protection circuit and a rear-stage level comparator circuit; The front-stage anti-interference rectifier bridge circuit is used to receive a source-type or sink-type high-speed pulse signal, and rectify the received high-speed pulse signal to obtain a stable DC wave signal; The high-speed optical coupling isolation acquisition transmission circuit is connected to the front-stage anti-interference rectifier bridge circuit, and is used to collect external high-speed pulse signals, convert them into current signals, and perform shunting processing on the current signals; The current limiting protection circuit is connected to the front-stage anti-interference rectifier bridge circuit and the high-speed optocoupler isolation acquisition transmission circuit, and is used to perform current limiting protection on the entire circuit when a high-level high-speed pulse signal is input externally; The post-stage level comparator circuit is connected to the high-speed optical coupler isolation acquisition transmission circuit, and is used to shape and filter the high-speed pulse signal output by the high-speed optical coupler isolation acquisition transmission circuit and output it.

[0009] Preferably, the front-stage anti-interference rectifier bridge circuit includes a TVS diode and a universal rectifier bridge, the two ends of the TVS diode are respectively connected to the two ends of the AC input end of the rectifier bridge, the positive pole of the DC output end of the rectifier bridge is connected to the input end of the high-speed optocoupler isolation acquisition transmission circuit, and the negative pole of the DC output end of the rectifier bridge is connected to the current limiting protection circuit.

[0010] Preferably, the high-speed optocoupler isolation acquisition and transmission circuit includes a high-speed optocoupler U1, a current limiting resistor R1, a shunt resistor R3, a sampling resistor R6 and a resistor R7; one end of the current limiting resistor R1 is connected to the output end of the front-stage anti-interference rectifier bridge circuit, and the high-speed pulse signal output by the front-stage anti-interference rectifier bridge circuit generates a current signal after passing through the current limiting resistor R1; the other end of the current limiting resistor R1 is divided into two paths, one path is connected to an input end of the high-speed optocoupler U1 through the shunt resistor R3, and the other path is directly connected to the other input end of the high-speed optocoupler U1, an output end of the high-speed optocoupler U1 is grounded, the other output end of the high-speed optocoupler U1 is connected to one end of the sampling resistor R6 and connected to the power supply Vdd, and the other output end of the high-speed optocoupler U1 and the resistor R7 are connected to the post-stage level comparator circuit.

[0011] Preferably, the magnitude of the current I1 on the output side of the high-speed optocoupler is controlled by controlling the magnitude of the current Id flowing through the input side of the high-speed optocoupler U1; wherein, the magnitude correspondence between Id and I1 is determined by the characteristics of the high-speed optocoupler U1 itself, and the magnitude of the level at the positive input end of the input post-stage level comparator circuit is V1=Vdd-I1*R6; when the input high-speed pulse signal level Vpi≥the preset high level threshold, the level signal is shunted by the current limiting resistor R1 to ensure that the current flowing through the input side of the high-speed optocoupler U1 is sufficient to turn on the optocoupler without damage, thereby completing the protection of the input high-voltage signal circuit; when the input high-speed pulse signal level Vpi≤the preset low level threshold, the level signal is shunted by the current limiting resistor R1 to ensure that the current flowing through the input side of the high-speed optocoupler U1 is insufficient to turn on the optocoupler, thereby completing the filtering of low-voltage clutter, wherein, the input threshold requirements of the digital input high level and low level are achieved by adjusting the resistance values ​​of the current limiting resistor R1, the shunt resistor R3, and the sampling resistor R6.

[0012] Preferably, the current limiting protection circuit includes a resistor R2, a resistor R4, a resistor R5, a resistor R, a transistor Q1 and a transistor Q2, the collector of the transistor Q1 is connected to the high-speed optocoupler isolation collection and transmission circuit, the base of the transistor Q1 is connected to one end of the resistor R2, the other end of the resistor R2 is respectively connected to the high-speed optocoupler isolation collection and transmission circuit and the front-stage anti-interference rectifier bridge circuit, one end of the resistor R2 is connected to the collector of the transistor Q2, the emitter of the transistor Q2 is connected to the emitter of the transistor Q1 with the resistor R and the resistor R5 connected in series, and the base of the transistor Q2 is connected to the base of the transistor Q1 with the capacitor C1 and the resistor R4 connected in parallel.

[0013] Preferably, when the input signal level is greater than the level threshold, Ub1>Ue1 of transistor Q1, then transistor Q1 is turned on and transistor Q1 is in a saturation state; When the voltage is transmitted to the base of transistor Q2, Ub2>Ue2, then transistor Q2 is turned on. As the signal level increases, transistor Q2 changes from the amplification state to the saturation state. When transistor Q2 enters the saturation state, the voltage U2be across the base emitter of transistor Q2 approaches 0.6~0.7V. When the signal level of the external input is greater than the preset value, the current flowing through the main circuit of the circuit is limited to U2be / R; Among them, the current flowing through the transistor Q1 is the sum of the current flowing through the resistor R3 and the input side of the high-speed optocoupler U1; the current flowing through the resistor R is I=U2be / R, which is approximately equal to the current flowing through the emitter collector of the transistor Q1, that is, the sum of the current flowing through R3 and the input side of the high-speed optocoupler U1, Ub1 refers to the voltage between the base and emitter of the transistor Q1, Ue1 refers to the voltage between the emitter of the transistor Q1 to the ground or the reference point, Ub2 refers to the voltage between the base and the emitter of the transistor Q2, Ue2 refers to the voltage between the emitter of the transistor Q2 to the ground or the reference point, and U2be refers to the voltage difference between the base and the emitter of the transistor Q2, that is, the difference between Ub2 and Ue2.

[0014] Preferably, the post-stage level comparator circuit includes resistors R8, R9, R10 and a comparator U2, the positive input terminal of the comparator U2 is connected to the level V1 output by the high-speed optocoupler isolation transmission acquisition circuit, and the positive input terminal of the comparator U2 is connected to the output terminal of the comparator U2 through the resistor R10, the negative input terminal of the comparator U2 is connected to the resistor R8 and the resistor R9 connected in series, and the output terminal of the comparator U2 outputs a logic level signal for comparing the level V1 output by the high-speed optocoupler isolation transmission acquisition circuit obtained through the positive input terminal of the comparator U2 with the reference level Vref at the negative input terminal of the comparator U2, wherein the reference level Vref=Vdd*R9 / (R8+R9).

[0015] Preferably, when the level output by the high-speed optocoupler isolation transmission acquisition circuit is greater than the reference level, the output end of the comparator U2 outputs a high logic level; when the level output by the high-speed optocoupler isolation transmission acquisition circuit is less than the reference level, the output end of the comparator U2 outputs a low logic level.

[0016] The present invention further provides a bidirectional high-speed pulse input device with a current limiting protection function, the device comprising a bidirectional high-speed pulse input circuit with a current limiting protection function as described in an embodiment of the present invention.

[0017] The present invention further provides a control system, which includes a bidirectional high-speed pulse input circuit with a current limiting protection function as described in an embodiment of the present invention.

[0018] With respect to the prior art, the present invention has the following beneficial effects: The present invention discloses a bidirectional high-speed pulse input circuit and device with a current limiting protection function, including: a front-stage anti-interference rectifier bridge circuit, a current limiting protection circuit, a high-speed optocoupler isolation acquisition and transmission circuit, and a rear-stage level comparator circuit. The front-stage anti-interference rectifier bridge circuit receives a source-type or a drain-type high-speed pulse signal, then performs rectification processing and outputs a signal. The input end of the high-speed optocoupler isolation acquisition and transmission circuit is connected to the output end of the front-stage anti-interference rectifier bridge circuit. The high-speed optocoupler isolation acquisition and transmission circuit collects external high-speed pulse signals, converts them into current signals, and performs shunt processing on the current signals. The current limiting protection circuit is connected to the front-stage anti-interference rectifier bridge circuit and the high-speed optocoupler isolation acquisition and transmission circuit. When a high-level high-speed pulse signal is input externally, it plays a role in current limiting protection of the overall circuit. The input end of the post-stage level comparator circuit is connected to the output end of the high-speed optocoupler isolation acquisition and transmission circuit, which is used to shape, filter and output the high-speed pulse signal output by the high-speed optocoupler isolation acquisition and transmission circuit, solving the defect that the existing digital input circuit cannot collect bidirectional high-speed pulse signals. It also has current limiting protection and strong anti-interference ability, meeting more complex industrial site needs.

[0019] The present invention can collect and transmit high-speed pulse signals up to 200KHZ, and the signal quality is complete. It can meet the two wiring access modes of source type and drain type in industrial field, and in multi-channel input applications, it has strong anti-interference and current limiting protection capabilities, the components are simple and universal, and the cost of use is low. It well realizes the requirements of domestic automation and independent control of PLC products in the field of high-frequency pulse quantity input collection and control. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of a bidirectional high-speed pulse input circuit with current limiting protection function described in an embodiment of the present invention. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. 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.

[0022] In the actual implementation of this embodiment, it is assumed that the input high-speed pulse signal level is Vpi. According to the programmable controller industry standard GBT15969 and actual requirements, when Vpi≥4V, it is recognized by the subsequent digital control circuit as a high level, and the signal logic is "1". When Vpi≤1V, it is recognized by the subsequent digital control circuit as a low level, and the signal logic is "0". Among them, PLC: Programmable Logic Controller, a digital operation electronic system specially designed for application in industrial environments. It uses a programmable memory to store instructions for performing logical operations, sequential control, timing, counting and arithmetic operations, and controls various types of mechanical equipment or production processes through digital or analog input and output. High-speed pulse input: the process of inputting very fast pulse signals into the PLC (programmable logic controller) through external sensors or devices; the PLC accurately captures these pulse signals and converts them into data that can be used for control. Switch quantity: also called logic quantity, it has only two values, namely 0 or 1, on or off. Pulse quantity: A digital quantity whose value is always changing between 0 (low level) and 1 (high level). The number of pulse changes per second is called frequency.

[0023] like Figure 1 As shown, the present invention provides a bidirectional high-speed pulse input circuit with a current limiting protection function, which is suitable for a PLC controller, including a front-stage anti-interference rectifier bridge circuit, a high-speed optical coupler isolation acquisition and transmission circuit, a current limiting protection circuit and a rear-stage level comparator circuit; the front-stage anti-interference rectifier bridge circuit is used to receive a source-type or a drain-type high-speed pulse signal, and rectify the received high-speed pulse signal to obtain a stable DC wave signal; the high-speed optical coupler isolation acquisition and transmission circuit is connected to the front-stage anti-interference rectifier bridge circuit, and is used to collect external high-speed pulse signals and convert them into current signals, and rectify the received high-speed pulse signals. The current signal is shunted; the current limiting protection circuit is connected to the front-stage anti-interference rectifier bridge circuit and the high-speed optocoupler isolation acquisition and transmission circuit, and is used to perform current limiting protection on the overall circuit when a high-level high-speed pulse signal is input from the outside; the post-stage level comparator circuit is connected to the high-speed optocoupler isolation acquisition and transmission circuit, and is used to shape, filter and output the high-speed pulse signal output by the high-speed optocoupler isolation acquisition and transmission circuit, which solves the defect that the existing digital quantity input circuit cannot collect bidirectional high-speed pulse signals, and has current limiting protection and strong anti-interference ability, realizing more complex industrial site needs.

[0024] Specifically, the front-stage anti-interference rectifier bridge circuit includes a TVS diode and a general rectifier bridge, which is used to rectify and process complex industrial field signals to obtain a stable DC wave signal, compatible with both high-speed pulse signal source input and drain input, and also has a protective function to prevent high voltage from damaging the device port. The two ends of the TVS diode are respectively connected to the two ends of the AC input end of the rectifier bridge, the positive pole of the DC output end of the rectifier bridge is connected to the input end of the high-speed optocoupler isolation collection and transmission circuit, and the negative pole of the DC output end of the rectifier bridge is connected to the current limiting protection circuit.

[0025] Specifically, the high-speed optocoupler isolation acquisition and transmission circuit includes a universal unidirectional high-speed optocoupler U1, a current limiting resistor R1, a shunt resistor R3, a sampling resistor R6 and a resistor R7; one end of the current limiting resistor R1 is connected to the output end of the front-stage anti-interference rectifier bridge circuit, and the high-speed pulse signal output by the front-stage anti-interference rectifier bridge circuit generates a current signal after passing through the current limiting resistor R1; the other end of the current limiting resistor R1 is divided into two paths, one path is connected to an input end of the high-speed optocoupler U1 through the shunt resistor R3, and the other path is directly connected to the other input end of the high-speed optocoupler U1, an output end of the high-speed optocoupler U1 is grounded, the other output end of the high-speed optocoupler U1 is connected to one end of the sampling resistor R6 and connected to the power supply Vdd, and the other output end of the high-speed optocoupler U1 and the resistor R7 are connected to the post-stage level comparator circuit. The principle is: by controlling the size of the current Id flowing through the input side of the high-speed optocoupler U1, the size of the current I1 on the output side of the high-speed optocoupler is controlled. It can be understood that when the high-speed pulse signal output by the front-stage anti-interference rectifier bridge circuit passes through R1, a part of the current signal flows through the input side of the high-speed optocoupler U1, and the other part flows through R3. By controlling the size of the current Id flowing through the input side of the high-speed optocoupler, the size of the current I1 on the output side of the high-speed optocoupler is controlled; wherein, the size correspondence between Id and I1 is determined by the characteristics of the high-speed optocoupler U1 itself, and the level size of the positive input end of the input back-stage level comparator circuit is V1=Vdd-I1*R6; when the input high-speed pulse signal level Vpi≥preset high level threshold value such as 4V, the level signal After the signal is shunted by the current limiting resistor R1, it is ensured that the current flowing through the input side of the high-speed optocoupler U1 is sufficient to turn on the optocoupler without being damaged, thereby completing the protection of the input high-voltage signal circuit; when the input high-speed pulse signal level Vpi≤the preset low-level threshold value such as 1V, after being shunted by the current limiting resistor R1, it is ensured that the current flowing through the input side of the high-speed optocoupler U1 is insufficient to turn on the optocoupler, thereby completing the filtering of low-voltage clutter, wherein, by adjusting the resistance values ​​of the current limiting resistor R1, the shunt resistor R3, and the sampling resistor R6, the input threshold requirements of the high and low levels of the digital input are realized, that is, in actual use, according to the industrial requirements of the digital input logic "1" and logic "0" input threshold requirements, it can be achieved by adjusting the resistance values ​​of the three general resistors R1, R3, and R6.

[0026] Specifically, the current limiting protection circuit includes a resistor R2, a resistor R4, a resistor R5, a resistor R, a transistor Q1 and a transistor Q2, wherein Q1 is a main circuit power transistor and must be selected with a large package and high power, Q2 is a general-purpose transistor, the collector of the transistor Q1 is connected to the high-speed optocoupler isolation collection and transmission circuit, the base of the transistor Q1 is connected to one end of the resistor R2, the other end of the resistor R2 is respectively connected to the high-speed optocoupler isolation collection and transmission circuit and the front-stage anti-interference rectifier bridge circuit, one end of the resistor R2 is connected to the collector of the transistor Q2, the emitter of the transistor Q2 is connected to the emitter of the transistor Q1 with the resistor R and the resistor R5 connected in series, and the base of the transistor Q2 is connected to the base of the transistor Q1 with the capacitor C1 and the resistor R4 connected in parallel.

[0027] In the above current limiting protection circuit, the high-speed pulse signal input output by the front-stage anti-interference rectifier bridge circuit will divide a part of the entire circuit loop current. The current flowing through Q1 is the sum of the current flowing through the R3 resistor and the high-speed optocoupler input side. When the input signal level is greater than the level threshold, Ub1>Ue1 of transistor Q1, then transistor Q1 is turned on and transistor Q1 is in a saturated state; when the voltage is transmitted to the base of transistor Q2, Ub2>Ue2, then Q2 transistor is turned on. As the signal level increases, transistor Q2 changes from the amplification state to the saturation state. When transistor Q2 enters the saturation state, the voltage U2be across the base emitter of transistor Q2 approaches 0. 6~0.7V; when the signal level of the external input is greater than the preset value, the current flowing through the main circuit of the circuit is limited to U2be / R; among them, the current flowing through the resistor R is I=U2be / R, which is approximately equal to the current flowing through the emitter collector of the transistor Q1, that is, the sum of the currents flowing through R3 and the input side of the high-speed optocoupler U1, Ub1 refers to the voltage between the base and emitter of the transistor Q1, Ue1 refers to the voltage between the emitter of the transistor Q1 and the ground or reference point, Ub2 refers to the voltage between the base and emitter of the transistor Q2, Ue2 refers to the voltage between the emitter of the transistor Q2 and the ground or reference point, and U2be refers to the voltage difference between the base and emitter of the transistor Q2, that is, the difference between Ub2 and Ue2.

[0028] Specifically, the post-stage level comparator circuit includes resistors R8, R9, R10 and comparator U2. Mainly due to the discrete distribution characteristics of the transmission ratio CTR parameter of the high-speed optocoupler itself, in the actual application of multi-channel digital input, the threshold voltage threshold value window is expanded, the logic level certainty is increased, and the risk of false triggering is reduced. Therefore, a level comparator is used to transmit the level V1 output by the high-speed optocoupler isolation transmission acquisition circuit. The positive input terminal of the comparator U2 is connected to the level V1 output by the high-speed optocoupler isolation transmission acquisition circuit. , and the positive input terminal of the comparator U2 is connected to the output terminal of the comparator U2 through the resistor R10, the negative input terminal of the comparator U2 is connected to the resistor R8 and the resistor R9 connected in series, and the output terminal of the comparator U2 outputs a logic level signal, which is used to compare the level V1 output by the high-speed optical coupling isolation transmission acquisition circuit obtained through the positive input terminal of the comparator U2 with the reference level Vref of the negative input terminal of the comparator U2, wherein the reference level Vref=Vdd*R9 / (R8+R9).

[0029] During implementation, when the level output by the high-speed optocoupler isolation transmission acquisition circuit is greater than the reference level, the output end of the comparator U2 outputs a high logic level; when the level output by the high-speed optocoupler isolation transmission acquisition circuit is less than the reference level, the output end of the comparator U2 outputs a low logic level.

[0030] When implementing, the specific description is as follows in conjunction with the accompanying drawings: When the input signal voltage is within the logic "1" range, when the external high-speed pulse signal is input, after passing through the anti-interference rectifier bridge circuit, when the external voltage is abnormally too large, it exceeds the preset threshold, the current flowing through the Q1 transistor increases, the current flowing through R increases, and the voltage across R increases, that is, the voltage across the base emitter of Q2 increases, and the conduction degree of Q2 increases. At this time, Q2 works in the amplification state, the voltage difference across the emitter and collector of Q2 decreases, the base voltage of Q1 decreases, and the conduction degree of Q1 decreases, then the current flowing through Q1 decreases, that is, the current flowing through R and the diode end on the input side of the optocoupler decreases, so that the circuit is maintained in a dynamic balance process. When the external voltage increases, within the design requirements, the current flowing through Q2 is large enough, and Q2 changes from the amplification state to the saturation state. At this time, the current flowing through R, Q1 main circuit is constant, about I=U2be / R; when the input signal voltage is within the logic "0" range, the main circuit current is shunted by D1, and the current flowing through R1 is shunted by resistor R3. The current flowing through the input side of the high-speed optocoupler is not enough to conduct. The level of the high-speed optocoupler output side is processed by the post-stage comparator level circuit and sent to the digital control processor to realize the high and low level recognition of logic "1" and "0". Due to the complex process environment of the actual industrial site, it is easy to have abnormal conditions such as excessive access level. Therefore, this solution solves the problem of collecting bidirectional high-speed pulse signals and takes into account the role of circuit protection when the higher level is turned on.

[0031] The present invention further provides a bidirectional high-speed pulse input device with a current limiting protection function, the device comprising a bidirectional high-speed pulse input circuit with a current limiting protection function as described in an embodiment of the present invention.

[0032] The present invention further provides a control system, which includes a bidirectional high-speed pulse input circuit with a current limiting protection function as described in an embodiment of the present invention.

[0033] The functional principles thereof are as described in the above embodiments of the present invention, and will not be described in detail here. For the parts not described in detail in the device, equipment or system embodiments, reference may be made to the description of the relevant parts in the circuit embodiments.

[0034] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A bidirectional high-speed pulse input circuit with current limiting protection function, characterized in that: It includes a front-stage anti-interference rectifier bridge circuit, a high-speed optocoupler isolation acquisition transmission circuit, a current limiting protection circuit and a rear-stage level comparator circuit; The front-stage anti-interference rectifier bridge circuit is used to receive a source-type or sink-type high-speed pulse signal, and rectify the received high-speed pulse signal to obtain a stable DC wave signal; The high-speed optical coupling isolation acquisition transmission circuit is connected to the front-stage anti-interference rectifier bridge circuit, and is used to collect external high-speed pulse signals, convert them into current signals, and perform shunting processing on the current signals; The current limiting protection circuit is connected to the front-stage anti-interference rectifier bridge circuit and the high-speed optocoupler isolation acquisition transmission circuit, and is used to perform current limiting protection on the entire circuit when a high-level high-speed pulse signal is input externally; The post-stage level comparator circuit is connected to the high-speed optical coupler isolation acquisition transmission circuit, and is used to shape and filter the high-speed pulse signal output by the high-speed optical coupler isolation acquisition transmission circuit and output it.

2. A bidirectional high-speed pulse input circuit with current limiting protection function as claimed in claim 1, characterized in that: The front-stage anti-interference rectifier bridge circuit includes a TVS diode and a universal rectifier bridge, the two ends of the TVS diode are respectively connected to the two ends of the AC input end of the rectifier bridge, the positive pole of the DC output end of the rectifier bridge is connected to the input end of the high-speed optocoupler isolation collection and transmission circuit, and the negative pole of the DC output end of the rectifier bridge is connected to the current limiting protection circuit.

3. A bidirectional high-speed pulse input circuit with current limiting protection function as claimed in claim 1, characterized in that: The high-speed optocoupler isolation acquisition transmission circuit includes a high-speed optocoupler U1, a current limiting resistor R1, a shunt resistor R3, a sampling resistor R6 and a resistor R7; One end of the current limiting resistor R1 is connected to the output end of the front-stage anti-interference rectifier bridge circuit, and the high-speed pulse signal output by the front-stage anti-interference rectifier bridge circuit generates a current signal after passing through the current limiting resistor R1; the other end of the current limiting resistor R1 is divided into two paths, one path is connected to an input end of the high-speed optocoupler U1 through the shunt resistor R3, and the other path is directly connected to the other input end of the high-speed optocoupler U1, an output end of the high-speed optocoupler U1 is grounded, the other output end of the high-speed optocoupler U1 is connected to one end of the sampling resistor R6 and connected to the power supply Vdd, and the other output end of the high-speed optocoupler U1 and the resistor R7 are connected to the post-stage level comparator circuit.

4. A bidirectional high-speed pulse input circuit with current limiting protection function as claimed in claim 3, characterized in that: By controlling the magnitude of the current Id flowing through the input side of the high-speed optocoupler U1, the magnitude of the current I1 on the output side of the high-speed optocoupler is controlled; Among them, the corresponding relationship between Id and I1 is determined by the characteristics of the high-speed optocoupler U1 itself, and the level of the positive input end of the input post-level comparator circuit is V1=Vdd-I1*R6; When the input high-speed pulse signal level Vpi ≥ the preset high-level threshold, the level signal is shunted by the current-limiting resistor R1 to ensure that the current flowing through the input side of the high-speed optocoupler U1 is sufficient to turn on the optocoupler without damage, thereby completing the protection of the input high-voltage signal circuit; When the input high-speed pulse signal level Vpi ≤ the preset low-level threshold, after being shunted by the current-limiting resistor R1, the current flowing through the input side of the high-speed optocoupler U1 is ensured to be insufficient to turn on the optocoupler, thereby completing the filtering of low-voltage clutter. The input threshold requirements of the high level and low level of the digital input are achieved by adjusting the resistance values ​​of the current limiting resistor R1, the shunt resistor R3, and the sampling resistor R6.

5. A bidirectional high-speed pulse input circuit with current limiting protection function as claimed in claim 1, characterized in that: The current limiting protection circuit includes a resistor R2, a resistor R4, a resistor R5, a resistor R, a transistor Q1 and a transistor Q2, the collector of the transistor Q1 is connected to the high-speed optocoupler isolation collection and transmission circuit, the base of the transistor Q1 is connected to one end of the resistor R2, the other end of the resistor R2 is respectively connected to the high-speed optocoupler isolation collection and transmission circuit and the front-stage anti-interference rectifier bridge circuit, one end of the resistor R2 is connected to the collector of the transistor Q2, the emitter of the transistor Q2 is connected to the emitter of the transistor Q1 with the resistor R and the resistor R5 connected in series, and the base of the transistor Q2 is connected to the base of the transistor Q1 with the capacitor C1 and the resistor R4 connected in parallel.

6. A bidirectional high-speed pulse input circuit with current limiting protection function as claimed in claim 5, characterized in that: When the input signal level is greater than the level threshold, Ub1>Ue1 of transistor Q1, then transistor Q1 is turned on and transistor Q1 is in saturation state; When the voltage is transmitted to the base of transistor Q2, Ub2>Ue2, then transistor Q2 is turned on. As the signal level increases, transistor Q2 changes from the amplification state to the saturation state. When transistor Q2 enters the saturation state, the voltage U2be across the base emitter of transistor Q2 approaches 0.6~0.7V. When the signal level of the external input is greater than the preset value, the current flowing through the main circuit of the circuit is limited to U2be / R; Among them, the current flowing through the transistor Q1 is the sum of the current flowing through the resistor R3 and the input side of the high-speed optocoupler U1; the current flowing through the resistor R is I=U2be / R, which is approximately equal to the current flowing through the emitter collector of the transistor Q1, that is, the sum of the current flowing through R3 and the input side of the high-speed optocoupler U1, Ub1 refers to the voltage between the base and emitter of the transistor Q1, Ue1 refers to the voltage between the emitter of the transistor Q1 to the ground or the reference point, Ub2 refers to the voltage between the base and the emitter of the transistor Q2, Ue2 refers to the voltage between the emitter of the transistor Q2 to the ground or the reference point, and U2be refers to the voltage difference between the base and the emitter of the transistor Q2, that is, the difference between Ub2 and Ue2.

7. A bidirectional high-speed pulse input circuit with current limiting protection function as claimed in claim 1, characterized in that: The post-stage level comparator circuit includes resistors R8, R9, R10 and a comparator U2, wherein the positive input terminal of the comparator U2 is connected to the level V1 output by the high-speed optocoupler isolation transmission acquisition circuit, and the positive input terminal of the comparator U2 is connected to the output terminal of the comparator U2 through the resistor R10, the negative input terminal of the comparator U2 is connected to the resistor R8 and the resistor R9 connected in series, and the output terminal of the comparator U2 outputs a logic level signal for comparing the level V1 output by the high-speed optocoupler isolation transmission acquisition circuit obtained through the positive input terminal of the comparator U2 with the reference level Vref at the negative input terminal of the comparator U2, wherein the reference level Vref=Vdd*R9 / (R8+R9).

8. A bidirectional high-speed pulse input circuit with current limiting protection function as claimed in claim 7, characterized in that: When the level output by the high-speed optocoupler isolation transmission acquisition circuit is greater than the reference level, the output end of the comparator U2 outputs a high logic level; when the level output by the high-speed optocoupler isolation transmission acquisition circuit is less than the reference level, the output end of the comparator U2 outputs a low logic level.

9. A bidirectional high-speed pulse input device with current limiting protection function, characterized in that: The device comprises a bidirectional high-speed pulse input circuit with a current limiting protection function as claimed in any one of claims 1 to 8.

10. A control system, characterized in that: The control system includes a bidirectional high-speed pulse input circuit with a current limiting protection function as claimed in any one of claims 1 to 8.

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