Anti-interference circuit of PWM signal, board card and vehicle

Abstract

The invention provides a PWM signal anti-interference circuit, a board card and a vehicle. The PWM signal anti-interference circuit comprises a monitoring module and a safety module. The monitoring module is used for converting the high-level duration of a PWM signal to be measured into a charging voltage amplitude to be measured based on an RC integrating circuit arranged in the monitoring module, converting the high-level duration of a reference PWM signal into a reference charging voltage amplitude, comparing the charging voltage amplitude to be measured with the reference charging voltage amplitude, and outputting the charging voltage amplitude to be measured. Determining a comparison result; and the safety module is used for receiving the comparison result and then determining whether to perform exception processing on the PWM signal to be detected. Through the monitoring module, the process of monitoring whether the PWM signal to be detected is abnormal or not is realized. According to the PWM signal circuit, the judgment is carried out based on the safety module to determine whether to automatically take countermeasures, so that the influence of interference can be prevented from being further expanded, the anti-interference capability of the PWM signal circuit is improved, and the safety and the stability of the PWM signal circuit are enhanced.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic circuits, and particularly to an anti-interference circuit, a board card, and a vehicle for PWM signals. Background Art

[0002] With the increasing innovation of electronic control technology, the electrification process of commercial vehicles is accelerating. As a transportation tool to promote social productivity, Pulse Width Modulation (PWM) technology can be applied to both sensor signal conditioning and load driving.

[0003] PWM signals are usually quite sensitive. In some extreme application scenarios such as strong magnetic environments, the interaction between magnetism and electricity will generate unknown induced currents, electromotive forces, and acting forces. If the magnetic field is time-varying, eddy current effects will also occur. These effects not only affect the movement trajectory and distribution of charges in the signal loop, but the eddy current effect will consume the electrical energy in the loop, resulting in signal attenuation and distortion, etc.; causing distortions in parameters such as the frequency, duty cycle, and amplitude of the PWM waveform, leading to control failures in related systems and thus affecting driving safety. How to improve the anti-interference ability of the PWM signal circuit and enhance the safety and stability of the PWM signal circuit is an important issue that the industry urgently needs to solve at present. Summary of the Invention

[0004] The present invention provides an anti-interference circuit, a board card, and a vehicle for PWM signals to improve the anti-interference ability of the PWM signal circuit and enhance the safety and stability of the PWM signal circuit.

[0005] The present invention provides an anti-interference circuit for PWM signals, including: a monitoring module and a safety module; The first input end of the monitoring module is connected to the PWM signal to be measured, and the second input end of the monitoring module is connected to the reference PWM signal. It is used to convert the high-level duration of the PWM signal to be measured into the amplitude of the charging voltage to be measured, and convert the high-level duration of the reference PWM signal into the amplitude of the reference charging voltage based on the RC integration circuit set in the monitoring module, and compare the amplitude of the charging voltage to be measured with the amplitude of the reference charging voltage to determine the comparison result; The safety module is connected to the output end of the monitoring module. After receiving the comparison result, it is used to determine whether to perform abnormal processing on the PWM signal to be measured based on the comparison result. The abnormal processing includes turning off the PWM signal to be measured or controlling the duty cycle of the PWM signal to a preset duty cycle value.

[0006] An anti-interference circuit for PWM signals provided by the present invention, the monitoring module includes a first RC integrating circuit, a second RC integrating circuit, a third RC integrating circuit, a fourth RC integrating circuit, and a comparison module; The first end of the first RC integrating circuit and the first end of the third RC integrating circuit serve as the first input end of the monitoring module, and the first end of the second RC integrating circuit and the first end of the fourth RC integrating circuit serve as the second input end of the monitoring module; The second end of the first RC integrating circuit is connected to the first input end of the comparison module, and is used to convert the high-level duration of the PWM signal to be measured into the first measured charging voltage amplitude; The first end of the second RC integrating circuit is connected to a first reference PWM signal, and the second end of the second RC integrating circuit is connected to the second input end of the comparison module, and is used to convert the high-level duration of the first reference PWM signal into the first reference charging voltage amplitude, and the first reference PWM signal is a PWM reference signal with a duty cycle of a preset upper limit value; The second end of the third RC integrating circuit is connected to the third input end of the comparison module, and is used to convert the high-level duration of the PWM signal to be measured into the second measured charging voltage amplitude; The first end of the fourth RC integrating circuit is connected to a second reference PWM signal, and the second end of the second RC integrating circuit is connected to the fourth input end of the comparison module, and is used to convert the high-level duration of the second reference PWM signal into the second reference charging voltage amplitude, and the second reference PWM signal is a PWM reference signal with a duty cycle of a preset lower limit value; The output end of the comparison module serves as the output end of the monitoring module, and is used to determine a comparison result based on the first measured charging voltage amplitude, the second measured charging voltage amplitude, the first reference charging voltage amplitude, and the second reference charging voltage amplitude.

[0007] An anti-interference circuit for PWM signals provided by the present invention, the comparison module includes a first window comparator, a second window comparator, and an OR gate; The first input end of the first window comparator serves as the first input end of the comparison module, the second input end of the first window comparator serves as the second input end of the comparison module, the first input end of the second window comparator serves as the third input end of the comparison module, and the second input end of the second window comparator serves as the fourth input end of the comparison module; The output end of the first window comparator is connected to the first input end of the OR gate, and is used to output a high level when the first measured charging voltage amplitude is less than the first reference charging voltage amplitude, otherwise, output a low level; The output terminal of the second window comparator is connected to the second input terminal of the OR gate, and is used to output a low level when the amplitude of the second charging voltage to be measured is greater than the amplitude of the second reference charging voltage, otherwise, output a high level; The output terminal of the OR gate serves as the output terminal of the comparison module, and is used to receive the outputs of the first window comparator and the second window comparator, and output a logical judgment result.

[0008] According to an anti-interference circuit for a PWM signal provided by the present invention, the monitoring module further includes: a signal protection circuit; The first terminal of the signal protection circuit serves as the first input terminal of the monitoring module, and the second terminal of the signal protection circuit is respectively connected to the first terminal of the second RC integration circuit and the first terminal of the fourth RC integration circuit, and is used to absorb the instantaneous high voltage or large current generated by the PWM signal due to strong magnetic interference.

[0009] According to an anti-interference circuit for a PWM signal provided by the present invention, the signal protection circuit includes a TVS tube, a first clamping diode, and a second clamping diode; The first terminal of the TVS tube serves as the first terminal of the signal protection circuit, the second terminal of the TVS tube is grounded, the first terminal of the second clamping diode is connected to the second terminal of the TVS tube, the second terminal of the second clamping diode is connected to the first terminal of the first clamping diode, the second terminal of the first clamping diode is connected to a reference voltage, and the first terminal of the first clamping diode serves as the second terminal of the signal protection circuit.

[0010] According to an anti-interference circuit for a PWM signal provided by the present invention, the monitoring module further includes: a discharging module; The discharging module is respectively connected to the first RC integration circuit, the second RC integration circuit, the third RC integration circuit, and the fourth RC integration circuit, and is used for the discharging process of the charges accumulated in the first RC integration circuit, the second RC integration circuit, the third RC integration circuit, and the fourth RC integration circuit.

[0011] According to an anti-interference circuit for a PWM signal provided by the present invention, the safety module is based on an optocoupler as an isolation medium to separately isolate the PWM signal to be measured, so as to turn off the PWM signal to be measured; The safety module is based on a T counter to control the duty cycle of the PWM signal to a preset duty cycle value.

[0012] According to an anti-interference circuit for a PWM signal provided by the present invention, the safety module further includes: a signal abnormality prompt module; The input end of the signal anomaly prompt module is connected to the output end of the monitoring module, and is used to receive the comparison result output by the monitoring module and perform anomaly prompting based on the comparison result.

[0013] The present invention also provides a board card, including an anti-interference circuit for any one of the above-mentioned PWM signals.

[0014] The present invention also provides a vehicle, including the board card as described above.

[0015] The anti-interference circuit for PWM signals, board card, and vehicle provided by the present invention provide a reliable reference standard for determining whether the PWM signal to be measured is normal by accessing the reference PWM signal. Based on the RC integration circuit provided in the monitoring module and based on the charge and discharge process of the PWM signal, the high-level duration of the PWM signal is converted into a voltage amplitude, realizing the monitoring process of whether the PWM signal to be measured is abnormal. Based on the judgment of the monitoring result by the security module, it is determined whether to automatically take countermeasures, which can timely process abnormal signals, avoid the further expansion of the influence of interference, improve the anti-interference ability of the PWM signal circuit, and enhance the security and stability of the PWM signal circuit. Description of the Drawings

[0016] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required to be used in the description of the embodiments or the prior art. Obviously, the drawings in the following description are 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.

[0017] Figure 1 It is the magnetic shielding effect diagram provided by the related method.

[0018] Figure 2 It is the schematic diagram of the main control chip's verification of the PWM signal provided by the related method.

[0019] Figure 3 It is the schematic diagram of three isolation circuit methods provided by the related method.

[0020] Figure 4 It is the structural schematic diagram of the anti-interference circuit for PWM signals provided by the present invention.

[0021] Figure 5 It is the schematic diagram of the RC integration circuit signal conversion waveform provided by the present invention.

[0022] Figure 6 It is the structural schematic diagram of the monitoring circuit provided by the present invention.

[0023] Figure 7It is a schematic diagram for judging fault signals during the charging process provided by the present invention.

[0024] Figure 8 It is a schematic diagram of the charge-discharge conversion waveform with frequency mutation provided by the present invention.

[0025] Figure 9 It is a schematic diagram of the PWM safety mechanism design provided by the present invention.

[0026] Figure 10 It is a schematic diagram of the waveform with duty cycle change provided by the present invention.

[0027] Figure 11 It is a schematic diagram of the circuit structure of the signal anomaly prompt module provided by the present invention.

[0028] Figure 12 It is a flowchart of the anti-interference PWM circuit design provided by the present invention. Specific embodiments

[0029] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions in the present invention will be clearly and completely described below with reference to the accompanying drawings in 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 in the present invention without making creative efforts fall within the scope of protection of the present invention.

[0030] The electrification process of commercial vehicles is accelerating. As a transportation tool to promote social productivity, PWM (pulse width modulation) technology can be applied to both sensor signal conditioning and load driving. However, PWM signals are usually quite sensitive. In some extreme application scenarios such as strong magnetic environments, the interaction between magnetism and electricity will generate unknown induced currents, electromotive forces and acting forces. If the magnetic field is time-varying, eddy current effects will also occur. And the above effects not only affect the charge movement trajectories and distributions in the signal loop, but also the eddy current effect will consume the electrical energy in the loop, resulting in signal attenuation and distortion, etc.; causing distortions in parameters such as the frequency, duty cycle and amplitude of the PWM waveform, leading to control failures in related systems and thus affecting driving safety.

[0031] The existing technologies for commercial vehicles to cope with strong magnetic field interference of PWM signals in related methods mainly include the following three aspects: One of the related methods is achieved by wrapping with magnetic shielding materials. The relevant electronic control systems are peripherally wrapped with magnetic shielding materials. The shielding principle is to reduce the magnetic induction lines passing through the internal circuit to weaken the strong magnetic interference. Commonly used ferromagnetic materials with high magnetic permeability such as soft iron, silicon steel, permalloy, etc. are used as the shielding layer to wrap the electronic control system and a cavity needs to be left inside, such as Figure 1As shown in the magnetic shielding effect diagram provided by the related method. Generally, ferromagnetic materials have a magnetic permeability thousands of times higher than that of air. Therefore, the magnetic resistance of ferromagnetic materials is much smaller than that of air. According to the characteristics of high magnetic permeability and low magnetic resistance, most of the magnetic induction lines in the magnetic field preferentially concentrate on the ferromagnetic materials. Most of the magnetic induction lines pass through the ferromagnetic materials, and very few magnetic induction lines enter the cavity. In this way, the strong magnetic field shielding of the electronic control system can be completed.

[0032] One of the defects of the related method is that: Ferromagnetic materials are only suitable for low-frequency magnetic fields, and the shielding effect is lost after the material is magnetically saturated; The implementation scope of this scheme is overall shielding, and the material cost is high; A cavity needs to be left for the shielding target, so it occupies a large amount of surrounding space and is not easy to be installed on a real vehicle.

[0033] The second related method is achieved by cutting off the PWM fault signal. The PWM signal is sampled in a strong magnetic field environment, and it is judged in real time whether the PWM signal fails. Commonly, the internal main control chip captures the rising / falling edges of the timer and counts the high level to obtain the duty cycle and frequency. As Figure 2 As shown in the schematic diagram of the PWM signal verification by the main control chip provided by the related method. The obtained duty cycle and frequency are compared and calculated with the set reference values inside the chip to judge whether the parameters of the actual PWM signal are reasonable. If there is a deviation, the relevant sampling and control of the PWM signal are cut off to achieve the self-protection of the system under strong magnetic field interference.

[0034] The defects of the second related method are that: It requires the system to have a main control unit and be able to process PWM signals, which increases the design cost of some simple sensors; The protection scope needs to cover the entire PWM signal processing link (including main control, power supply, etc.), resulting in an overabundance of signal protection resources; After being interfered, the main control chip may have incorrect operations, causing unknown faults and being unable to respond to the self-protection mechanism.

[0035] The third related method is achieved through circuit isolation. Circuit isolation can achieve signal isolation and transmission to protect the system from interference and faults and improve the safety and stability of the system. There are usually the following three isolation methods, such as Figure 3Schematic diagrams of three isolation circuit methods provided by related methods are shown. One is optocoupler isolation, which uses the optical principle and consists of an optocoupler and a photodiode to achieve electrical isolation in the signal transmission path. It has fast response and stable isolation performance, but usually has insufficient withstand voltage ability. The second is magnetic coupler isolation, which uses the principle of electromagnetic induction and consists of the input and output coils of a transformer to also achieve electrical isolation in the signal transmission path. It can be applied to high-voltage scenarios and has a high transmission rate, but is susceptible to external magnetic field interference. The third is capacitive coupler isolation, which uses the principle of high-frequency signal modulation (such as OOK modulation technology) and is composed of capacitors in series based on CMOS technology. It transmits information through the electric field change between two capacitor plates and has stable anti-interference ability, but does not achieve electrical isolation.

[0036] Among the above three isolation circuits, optocoupler and magnetic coupling achieve electrical isolation, and there will be no crosstalk between the input end and the output end. However, since magnetic coupler isolation itself applies the principle of electromagnetic induction, it is not suitable for strong magnetic field environments. Therefore, optocoupler isolation can be used as the preferred isolation circuit for strong magnetic anti-interference, but factors such as withstand voltage and signal frequency should be considered during design.

[0037] How to improve the anti-interference ability of the PWM signal circuit and enhance the safety and stability of the PWM signal circuit is an important issue that the industry urgently needs to solve at present.

[0038] Aiming at the defects of related methods, the present invention provides an anti-interference circuit for PWM signals. Figure 4 It is a schematic structural diagram of the anti-interference circuit for PWM signals provided by the present invention, as Figure 4 shown. The circuit includes a monitoring module 410 and a safety module 420.

[0039] The first input end of the monitoring module 410 is connected to the PWM signal to be measured, and the second input end of the monitoring module 410 is connected to a reference PWM signal. It is used to convert the high-level duration of the PWM signal to be measured into the amplitude of the charging voltage to be measured, and convert the high-level duration of the reference PWM signal into the amplitude of the reference charging voltage based on the RC integration circuit set in the monitoring module 410, and compare the amplitude of the charging voltage to be measured with the amplitude of the reference charging voltage to determine the comparison result. The safety module 420 is connected to the output end of the monitoring module 410. After receiving the comparison result, it is used to determine whether to perform abnormal processing on the PWM signal to be measured based on the comparison result. The abnormal processing includes turning off the PWM signal to be measured or controlling the duty cycle of the PWM signal to a preset duty cycle value.

[0040] Specifically, the monitoring module 410 includes two input terminals, which are respectively connected to the PWM signal to be measured and the reference PWM signal, and the judgment process is implemented based on the idea of comparison and reference. The reference PWM signal serves as a stable and known reference standard, representing the characteristics that the PWM signal should have under ideal conditions. The PWM signal to be measured is a signal that may be subject to various interferences in the actual operating environment, and parameters such as its high-level duration and duty cycle are likely to deviate from the normal range.

[0041] The RC integrating circuit set in the monitoring module 410 converts the high-level duration of the PWM signal to be measured into the amplitude of the charging voltage to be measured, and converts the high-level duration of the reference PWM signal into the amplitude of the reference charging voltage for the input PWM signal to be measured and the reference PWM signal.

[0042] Specifically, when the high level arrives, the capacitor starts to charge slowly through the resistor. Due to the time constant characteristics of the RC circuit, during the high-level duration, the voltage across the capacitor will rise according to an exponential law, and this rising voltage amplitude is closely related to the high-level duration, approximately in a proportional relationship. Therefore, through the RC integrating circuit, the high-level duration of the PWM signal, which is difficult to directly and accurately quantify and compare, can be converted into an intuitively measurable charging voltage amplitude. This conversion provides a high-precision quantization basis for subsequent comparison operations.

[0043] When it is determined that the PWM signal to be measured is severely interfered with and has a large deviation, which may pose an uncontrollable risk to subsequent electrical equipment or systems, the safety module takes decisive measures to directly turn off the PWM signal to be measured. Cut off the abnormal signal source in time to prevent the wrong instruction from being transmitted, and avoid the equipment from malfunctioning or being damaged due to receiving the wrong PWM signal, ensuring the safe and stable operation of the entire system.

[0044] In the case of relatively light interference, the safety module can choose to control the duty cycle of the PWM signal to the preset duty cycle value. This preset duty cycle value can be 50%. By forcibly adjusting the duty cycle of the possibly abnormal PWM signal to be measured to this preset duty cycle value, not only the certain operating function of the system is maintained, but also the unstable factors caused by the large fluctuation of the duty cycle are avoided, enabling the system to transition as smoothly as possible in the interference environment and waiting for the interference to be eliminated or further investigated and repaired.

[0045] The anti-interference circuit for PWM signals provided by the present invention provides a reliable reference standard for determining whether the PWM signal to be measured is normal by accessing the reference PWM signal. Based on the RC integration circuit set in the monitoring module, based on the charging and discharging process of the PWM signal, the high-level duration of the PWM signal is converted into a voltage amplitude, and the monitoring process of whether the PWM signal to be measured is abnormal is realized. Based on the judgment of the monitoring result by the security module, it is determined whether to automatically take countermeasures, which can timely process abnormal signals, avoid the further expansion of the influence of interference, improve the anti-interference ability of the PWM signal circuit, and enhance the security and stability of the PWM signal circuit.

[0046] In one embodiment, the monitoring module includes a first RC integration circuit, a second RC integration circuit, a third RC integration circuit, a fourth RC integration circuit, and a comparison module; the first ends of the first RC integration circuit and the third RC integration circuit serve as the first input end of the monitoring module, and the first ends of the second RC integration circuit and the fourth RC integration circuit serve as the second input end of the monitoring module; the second end of the first RC integration circuit is connected to the first input end of the comparison module, and is used to convert the high-level duration of the PWM signal to be measured into a first measured charging voltage amplitude; the first end of the second RC integration circuit accesses a first reference PWM signal, and the second end of the second RC integration circuit is connected to the second input end of the comparison module, and is used to convert the high-level duration of the first reference PWM signal into a first reference charging voltage amplitude; the second end of the third RC integration circuit is connected to the third input end of the comparison module, and is used to convert the high-level duration of the PWM signal to be measured into a second measured charging voltage amplitude; the first end of the fourth RC integration circuit accesses a second reference PWM signal, and the second end of the second RC integration circuit is connected to the fourth input end of the comparison module, and is used to convert the high-level duration of the second reference PWM signal into a second reference charging voltage amplitude; the output end of the comparison module serves as the output end of the monitoring module, and is used to determine the comparison result based on the first measured charging voltage amplitude, the second measured charging voltage amplitude, the first reference charging voltage amplitude, and the second reference charging voltage amplitude.

[0047] The first RC integration circuit, the second RC integration circuit, the third RC integration circuit, and the fourth RC integration circuit are set in the monitoring module. The first RC integration circuit.

[0048] The RC integration circuit can specifically be constructed based on a capacitor and a resistor. The RC integration circuit converts the high-level duration of the PWM signal into a charging process, specifically as shown in the schematic diagram of the signal conversion waveform of the RC integration circuit provided by the present invention. The mathematical model of this process is: Figure 5 As shown in the schematic diagram of the signal conversion waveform of the RC integration circuit provided by the present invention, the mathematical model of this process is: ; wherein is the voltage amplitude of RC charging, is the amplitude of the PWM signal, is the original voltage at the start of charging, generally 0 (amplitude unit: V). RC are the resistance and capacitance parameters of the integral circuit (R unit: Ω, C unit: F).

[0049] The reference PWM signal includes a first reference PWM signal and a second reference PWM signal. The first reference PWM signal is a PWM reference signal with a duty cycle of a preset upper limit value Vmax, and the second reference PWM signal is a PWM reference signal with a duty cycle of a preset lower limit value Vmin.

[0050] It can be understood that the PWM signal is usually represented by frequency and duty cycle, where the frequency is the reciprocal of the period in the mathematical model, and the duty cycle is the duration of the high level. Specifically, a comparator can be used to compare the duration of the high level. P1 represents the PWM signal to be measured, P2 and P3 are the first reference PWM signal and the second reference PWM signal of the system reference, Vmax represents the duty cycle upper limit, and Vmin represents the duty cycle lower limit. Therefore, it can be calculated and adjusted according to the actual signal to make its effective range Vmin% - Vmax%. If the actual duty cycle < Vmin% or the actual duty cycle > Vmax%, it can be considered that the actual PWM signal is incorrect.

[0051] Specifically, the comparison module includes a first window comparator, a second window comparator, and an OR gate; the first input terminal of the first window comparator serves as the first input terminal of the comparison module, the second input terminal of the first window comparator serves as the second input terminal of the comparison module, the first input terminal of the second window comparator serves as the third input terminal of the comparison module, and the second input terminal of the second window comparator serves as the fourth input terminal of the comparison module; the output terminal of the first window comparator is connected to the first input terminal of the OR gate, and is used to output a high level when the first measured charging voltage amplitude is less than the first reference charging voltage amplitude, otherwise, output a low level; the output terminal of the second window comparator is connected to the second input terminal of the OR gate, and is used to output a low level when the second measured charging voltage amplitude is greater than the second reference charging voltage amplitude, otherwise, output a high level; the output terminal of the OR gate serves as the output terminal of the comparison module, and is used to receive the outputs of the first window comparator and the second window comparator and output a logical judgment result.

[0052] Optionally, the schematic circuit diagram of the constructed monitoring module can be as Figure 6As shown in the schematic diagram of the monitoring circuit structure provided by the present invention. P1 is the incoming PWM signal to be measured, P2 is the first reference PWM signal, P3 is the second reference PWM signal, R1 and C1 form the first RC integrating circuit, R3 and C3 form the second RC integrating circuit, R2 and C2 form the third RC integrating circuit, and R4 and C4 form the fourth RC integrating circuit. The first window comparator U1, the second window comparator U2, and the OR gate U3 form the comparison module.

[0053] The parameters of R1~R4 and C1~C4 in the monitoring module are matched. Thus, the charging amplitude is determined by the duty cycle time. t is the duty cycle time (unit: s). According to the characteristic that the voltage across the capacitor cannot change suddenly, the influence of instantaneous pulses can be effectively avoided. As Figure 7 As shown in the schematic diagram of the discrimination of the charging process fault signal provided by the present invention, when the PWM signal is strongly magnetically interfered, it may cause a change in the duty cycle of the PWM signal, that is, the duty cycle < Vmin% and the charging time is shortened. Before the moment t1, the amplitude is less than the amplitude set by P3, so it can be recognized by the second window comparator U2 that the first reference charging voltage amplitude V1 is not reached 充 ; the duty cycle > Vmax% and the charging time is extended. After the moment t2, the amplitude is greater than the amplitude set by P2, and it can be recognized by the comparator U1 that it exceeds the second reference charging voltage amplitude V2 充 , and thus the range monitoring of the actual PWM signal duty cycle can be completed.

[0054] Specifically, the monitoring module further includes: a signal protection circuit. The signal protection circuit includes a TVS tube DT1, a first clamping diode D1, and a second clamping diode D2. The first end of the TVS tube serves as the first end of the signal protection circuit, the second end of the TVS tube is grounded, the first end of the second clamping diode is connected to the second end of the TVS tube, the second end of the second clamping diode is connected to the first end of the first clamping diode, the second end of the first clamping diode is connected to the reference voltage, and the first end of the first clamping diode serves as the second end of the signal protection circuit.

[0055] The TVS tube DT1 absorbs the instantaneous high voltage or large current that the PWM signal may bring due to strong magnetic interference, suppresses the transient impact of the signal, and avoids the damage of the subsequent circuit. The clamping diodes D1 and D2 clamp the PWM signal to the reference potential of the system, and complete the consistency of the system potential without changing the waveform of the original signal Furthermore, the monitoring module further includes: a discharging module; the discharging module is respectively connected to the first RC integrating circuit, the second RC integrating circuit, the third RC integrating circuit, and the fourth RC integrating circuit, and is used for the discharging process of the charges accumulated in the first RC integrating circuit, the second RC integrating circuit, the third RC integrating circuit, and the fourth RC integrating circuit.

[0056] The monitoring module can specifically be composed of inverters U7 and U8, NMOS transistors Q1, Q2, Q3, and Q4, and resistors R7, R8, R9, and R10, and can achieve rapid discharge of the charges accumulated in C1, C2, C3, and C4.

[0057] When the frequency of the PWM signal suddenly changes, the NMOS transistors are turned on by the inverter when the PWM is at a low level, and the charges accumulated in the capacitors in the integrating circuit are rapidly discharged, so that the charging process will not affect the signal monitoring in the next cycle. Set P2 and P3 as PWM reference signals with the same normal frequency. Compare the PWM signal with the normal frequency with the PWM signal with an increased frequency through U2, and the output of U2 is set high before time t; compare the PWM signal with the normal frequency with the PWM signal with a decreased frequency through U3, and the output of U2 is set high after time t. The result of the comparator can identify whether the PWM signal has changed suddenly. Among them, the charge-discharge conversion waveform with a sudden change in frequency in the PWM signal can be as Figure 8 shown in the schematic diagram of the charge-discharge conversion waveform with a sudden change in frequency provided by the present invention.

[0058] Further, after obtaining the judgment result output by the OR gate, it is used for the further processing process of the security module.

[0059] The security module is based on an optocoupler as an isolation medium to separately isolate the PWM signal to be measured, so as to turn off the PWM signal to be measured; the security module is based on a T counter to control the duty cycle of the PWM signal to a preset duty cycle value.

[0060] Specifically, for the strong magnetic interference of the electrical signal, the link isolation of the electrical signal is primarily completed. When a PWM signal failure occurs, the present invention provides a PWM signal security mechanism circuit, as Figure 9 shown in the schematic diagram of the PWM security mechanism design provided by the present invention. Among them, it is preferable to use an optocoupler as an isolation medium to separately isolate the PWM reference input and output power supply circuits. In this way, there is isolation at all positions where the voltage of the signal may change, and there is no loop circuit for the charges to avoid movement under strong magnetic interference. Considering that most of the used PWM duty cycles are 50%, using a T counter, set a PWM signal with twice the frequency as the trigger source, and trigger on the falling edge; the comparator U13 subtracts Q and ~Q. Regardless of what kind of sudden change occurs in the duty cycle, the final duty cycle of the PWM waveform remains 50% unchanged, as Figure 10 shown in the schematic diagram of the waveform with a changing duty cycle provided by the present invention. A certain security state can be set using this 50% PWM; or PWM control can be executed to turn off and stop the system operation.

[0061] Further, the security module further includes a signal anomaly prompting module; the input end of the signal anomaly prompting module is connected to the output end of the monitoring module, and is configured to receive the comparison result output by the monitoring module and perform anomaly prompting based on the comparison result.

[0062] The circuit structure schematic diagram of the signal anomaly prompting module can be as Figure 11 shown in the circuit structure schematic diagram of the signal anomaly prompting module provided by the present invention. When the actual PWM signal monitoring shows that the duty cycle is not within the threshold or the signal frequency suddenly changes, the U3 OR gate is set high. U4 is a D-type latch, which saves the fault signal by triggering on the rising edge. Since the set D port of this latch is pulled up to the power supply, as long as a rising edge comes, Q can output a high level and can turn on the backend security mechanism circuit through an optocoupler. At this time, a separate reference power supply VDD and a ground loop SGND need to be designed. When Q bar is at a low level, the LED lights up to remind the driver in time.

[0063] The present invention also provides a board card including the anti-interference circuit for any one of the above PWM signals.

[0064] The present invention also provides a vehicle including the above board card.

[0065] Among them, the schematic diagram of the PWM anti-interference circuit design process of the vehicle can be as Figure 12 shown in the anti-interference PWM circuit design flow chart provided by the present invention.

[0066] Specifically, it includes: PWM signal monitoring, which monitors the duty cycle of the PWM signal in real time and designs the upper and lower limit thresholds through the charge and discharge process.

[0067] Charge and discharge process conversion, based on the RC integration circuit, converts the high-level duration of the PWM signal into the amplitude of the charging voltage.

[0068] Upper and lower limit monitoring of the duty cycle and frequency mutation monitoring, which monitors the duty cycle of the PWM signal in real time, designs the upper and lower limit thresholds through the charge and discharge process, and based on the charge and discharge process of the PWM signal, can identify and report errors for signals with frequency mutations.

[0069] Based on the upper and lower limit monitoring of the duty cycle and frequency mutation monitoring, an abnormal alarm for the PWM signal is realized, and in the case of determining the PWM signal, a PWM signal security mechanism is adopted.

[0070] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed to multiple network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the solution of this embodiment. Those of ordinary skill in the art can understand and implement it without creative efforts.

[0071] Through the description of the above embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus a necessary general hardware platform, and of course, it can also be implemented by hardware. Based on this understanding, the essence of the above technical solution, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or some parts of the embodiments.

[0072] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments or equivalently replace some of the technical features. These modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An anti-interference circuit for PWM signals, characterized in that, Including: A monitoring module and a security module; The first input end of the monitoring module is connected to the PWM signal to be measured, and the second input end of the monitoring module is connected to the reference PWM signal. Based on the RC integration circuit set in the monitoring module, the high-level duration of the PWM signal to be measured is converted into the amplitude of the charging voltage to be measured, and the high-level duration of the reference PWM signal is converted into the amplitude of the reference charging voltage, and the amplitude of the charging voltage to be measured is compared with the amplitude of the reference charging voltage to determine the comparison result; The security module is connected to the output end of the monitoring module. After receiving the comparison result, it is used to determine whether to perform abnormal processing on the PWM signal to be measured based on the comparison result. The abnormal processing includes turning off the PWM signal to be measured or controlling the duty cycle of the PWM signal to a preset duty cycle value.

2. The anti-interference circuit for the PWM signal according to claim 1, characterized in that The monitoring module includes a first RC integration circuit, a second RC integration circuit, a third RC integration circuit, a fourth RC integration circuit, and a comparison module; The first end of the first RC integration circuit and the first end of the third RC integration circuit serve as the first input end of the monitoring module, and the first end of the second RC integration circuit and the first end of the fourth RC integration circuit serve as the second input end of the monitoring module; The second end of the first RC integration circuit is connected to the first input end of the comparison module, and is used to convert the high-level duration of the PWM signal to be measured into the first amplitude of the charging voltage to be measured; The first end of the second RC integration circuit is connected to a first reference PWM signal, and the second end of the second RC integration circuit is connected to the second input end of the comparison module, and is used to convert the high-level duration of the first reference PWM signal into the first amplitude of the reference charging voltage. The first reference PWM signal is a PWM reference signal with a duty cycle of a preset upper limit value; The second end of the third RC integration circuit is connected to the third input end of the comparison module, and is used to convert the high-level duration of the PWM signal to be measured into the second amplitude of the charging voltage to be measured; The first end of the fourth RC integration circuit is connected to a second reference PWM signal, and the second end of the second RC integration circuit is connected to the fourth input end of the comparison module, and is used to convert the high-level duration of the second reference PWM signal into the second amplitude of the reference charging voltage. The second reference PWM signal is a PWM reference signal with a duty cycle of a preset lower limit value; The output end of the comparison module serves as the output end of the monitoring module, and is used to determine the comparison result based on the first amplitude of the charging voltage to be measured, the second amplitude of the charging voltage to be measured, the first amplitude of the reference charging voltage, and the second amplitude of the reference charging voltage.

3. The anti-interference circuit of the PWM signal according to claim 2, characterized in that The comparison module includes a first window comparator, a second window comparator, and an OR gate; The first input terminal of the first window comparator serves as the first input terminal of the comparison module, the second input terminal of the first window comparator serves as the second input terminal of the comparison module, the first input terminal of the second window comparator serves as the third input terminal of the comparison module, and the second input terminal of the second window comparator serves as the fourth input terminal of the comparison module; The output terminal of the first window comparator is connected to the first input terminal of the OR gate, and is used to output a high level when the amplitude of the first measured charging voltage is less than the amplitude of the first reference charging voltage, otherwise, output a low level; The output terminal of the second window comparator is connected to the second input terminal of the OR gate, and is used to output a low level when the amplitude of the second measured charging voltage is greater than the amplitude of the second reference charging voltage, otherwise, output a high level; The output terminal of the OR gate serves as the output terminal of the comparison module, and is used to receive the outputs of the first window comparator and the second window comparator, and output a logical judgment result.

4. The anti-interference circuit for PWM signals according to claim 2, wherein The monitoring module further includes: a signal protection circuit; The first end of the signal protection circuit serves as the first input terminal of the monitoring module, and the second end of the signal protection circuit is respectively connected to the first ends of the second RC integration circuit and the fourth RC integration circuit, and is used to absorb the instantaneous high voltage or large current generated by the PWM signal due to strong magnetic interference.

5. The anti-interference circuit for the PWM signal according to claim 4, wherein, The signal protection circuit includes a TVS tube, a first clamping diode, and a second clamping diode; The first end of the TVS tube serves as the first end of the signal protection circuit, the second end of the TVS tube is grounded, the first end of the second clamping diode is connected to the second end of the TVS tube, the second end of the second clamping diode is connected to the first end of the first clamping diode, the second end of the first clamping diode is connected to a reference voltage, and the first end of the first clamping diode serves as the second end of the signal protection circuit.

6. The anti-interference circuit for the PWM signal according to claim 2, wherein The monitoring module further includes: a discharging module; The discharging module is respectively connected to the first RC integration circuit, the second RC integration circuit, the third RC integration circuit, and the fourth RC integration circuit, and is used for the discharging process of the charges accumulated in the first RC integration circuit, the second RC integration circuit, the third RC integration circuit, and the fourth RC integration circuit.

7. The anti-interference circuit for the PWM signal according to claim 1, wherein The safety module is based on an optocoupler as an isolation medium to separately isolate the measured PWM signal to turn off the measured PWM signal; The safety module is based on a T counter to control the duty cycle of the PWM signal to a preset duty cycle value.

8. The anti-interference circuit for the PWM signal according to claim 1, characterized in that, The safety module further includes: a signal anomaly prompt module; The input terminal of the signal anomaly prompt module is connected to the output terminal of the monitoring module, and is used to receive the comparison result output by the monitoring module and perform an anomaly prompt based on the comparison result.

9. A board card, characterized in that, It includes the anti-interference circuit of the PWM signal according to any one of claims 1-8.

10. A vehicle, characterized in that, It includes the board card according to claim 9.

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