CN114371791A - System and method for realizing stable touch protection of interactive intelligent blackboard - Google Patents

System and method for realizing stable touch protection of interactive intelligent blackboard Download PDF

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Publication number
CN114371791A
CN114371791A CN202110437729.5A CN202110437729A CN114371791A CN 114371791 A CN114371791 A CN 114371791A CN 202110437729 A CN202110437729 A CN 202110437729A CN 114371791 A CN114371791 A CN 114371791A
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capacitor
voltage
upe
touch
interference
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封宛昌
潘宇
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Jiangsu Xiaoniu Electronic Technology Co ltd
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Jiangsu Xiaoniu Electronic Technology Co ltd
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    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
    • G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
    • G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
    • G06F3/041—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
    • G06F3/0416—Control or interface arrangements specially adapted for digitisers
    • G06F3/0418—Control or interface arrangements specially adapted for digitisers for error correction or compensation, e.g. based on parallax, calibration or alignment
    • G06F3/04182—Filtering of noise external to the device and not generated by digitiser components
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
    • G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
    • G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
    • G06F3/041—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
    • G06F3/0412—Digitisers structurally integrated in a display
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
    • G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
    • G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
    • G06F3/041—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
    • G06F3/044—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means by capacitive means

Abstract

The invention discloses a system and a method for realizing stable touch protection of an interactive intelligent blackboard, and belongs to the technical field of intelligent blackboards. The method comprises the following steps: judging whether a protective ground wire is normally arranged or not, and executing the following steps if the protective ground wire is judged to be abnormally arranged; the effective value of the induced voltage between the protective ground wire and the outer frame of the touch display screen is measured to be U1And calculating the peak value Uind =2 of the induction voltage
Figure DEST_PATH_IMAGE002
U1(ii) a The induction voltage Uind is superposed with an interference signal induction voltage Uint; an anti-interference capacitor C is additionally arranged between the touch display screen and a city line zero line N to inhibit an interference signal induction voltage Uint; the effective value of the induction voltage between the protective ground wire and the outer frame of the touch display screen is measured again to be U2The maximum leakage current generated at this time is IL，IL＜10mA。According to the invention, the anti-interference capacitor CANT1 is additionally arranged between the outer frame of the touch screen and the zero line of the commercial power, so that interference is eliminated, normal touch is realized, the cost is reduced, and the touch screen is simple and reliable.

Description

System and method for realizing stable touch protection of interactive intelligent blackboard
Technical Field
The invention belongs to the technical field of intelligent blackboards, and particularly relates to a system and a method for realizing stable touch protection of an interactive intelligent blackboard.
Background
The commercial power is mostly provided with a TN-C-S pseudo three-phase five-wire system or TN-S three-phase five-wire system power supply system. At the transformer end, the working neutral (neutral) lines N of both systems are directly grounded at the transformer end to form a ground line PEN. The TN-C-S system is additionally provided with a ground wire PE for protection at the distribution room, and after entering a user, the TN-C-S system is divided into five wires to reach electric equipment, so that a section of connecting wire from a transformer end to the distribution room can be saved. And the TN-S system directly transmits the La, Lb, Lc, N and PEN formed by the transformer end to the electric equipment after passing through the distribution room. Because the PEN wire and the PE wire are connected with the outer frame of the electric equipment, the TN-C-S system and the TN-S system are equal from the safety aspect of electricity utilization, and the use quality of the electricity consumers can be relatively kept low. When the TN-C-S system normally operates, no current exists on the special protection line PE, and only when unbalanced current exists on the working zero line, a certain potential difference is formed between the special protection line PE and the working zero line (neutral line) N. But the PE wire has no voltage to the ground, so the metal shell of the electrical equipment is connected to the special protection wire PE for zero connection protection, and the safety and the reliability are realized.
Normally (mains protection earth PE connected to the device housing) this problem does not normally occur. However, in some working sites, because the power system configuration of the using unit is incomplete, the protection ground wire PE is not really connected with the ground or is not connected with the ground at all, and the problem of irregular jumping points (lines) of the capacitive touch blackboard can occur in the site; the source of the interference signal is not tied to ground with the backlight and the touch frame, and is not related to the reference level. When the interference signal exists, the noise displayed by the touch measurement software is larger when the touch measurement software is not touched; when touching, the noise around the touch point increases rapidly and causes irregular jumping points.
Disclosure of Invention
The invention provides a system and a method for realizing stable touch control protection of an interactive intelligent blackboard, which solve the problem that touch control is interfered when a non-protected area is not protected. (ii) a
The invention adopts the following technical scheme: a method for realizing stable touch protection of an interactive intelligent blackboard specifically comprises the following steps:
judging whether a protective ground wire is normally arranged or not, and executing the following steps if the protective ground wire is judged to be abnormally arranged;
the effective value of the induced voltage between the protective ground wire and the outer frame of the touch display screen is measured to be U1And calculating the peak value of the induced voltage
Figure BDA0003033799250000021
The induction voltage Uind is superposed with an interference signal induction voltage Uint;
an anti-interference capacitor C is additionally arranged between the touch display screen and a city line zero line N to inhibit an interference signal induction voltage Uint;
the effective value of the induction voltage between the protective ground wire and the outer frame of the touch display screen is measured again to be U2The maximum leakage current generated at this time is IL，IL＜10mA。
In a further embodiment, the capacity of the interference rejection capacitor C is 0.1uF, and the withstand voltage is 1000V.
In a further embodiment, the criterion for determining whether the protection ground is set normally is as follows: under the condition of normally connecting a protective earth wire PE, the preset voltage value of an alternating voltage phase line is set to be UPE-L1The predetermined voltage value of the working zero line is UPE-N1；
Detecting the actual voltage value of the AC voltage phase line as UPE-L in working state2The voltage value of the working zero line is UPE-N2；
If UPE-L2＝UPE-L1±UPE-L1X 10%, and UPE-N2≈UPE-N1(ii) a The protective earth wire is set normally;
if UPE-L2≠UPE-L1±UPE-L1X 10%, or UPE-N2Up to 70V or more, the protective earth PE is not normally set or is not set.
In a further embodiment, comprising:
the filtering and rectifying branch is connected with the live wire and the zero line;
the anti-surge branch is connected with the filtering and rectifying branch;
the LCC voltage reduction circuit is connected to the rectifying branch; the voltage drop after being processed by the rectifying circuit and the PFC power factor correction circuit is changed into 24v direct current voltage to supply power for the weak current circuit board and the touch control panel, and the circuit has the characteristics of high transient response and low power consumption.
The interface branch circuit is connected in anti-surge branch circuit, filtering rectification branch circuit and touch-control display screen, the interface branch circuit is equipped with electric capacity CANT 1.
By adopting the technical scheme: the anti-interference capacitor CANT1 with the capacity of 0.1uf is connected between the outer frame of the touch screen and the zero line N of the commercial power, the capacitance is very low in capacitance resistance to the interference signal, the interference signal is guided into the ground due to the bypass effect of CANT1, the effective value of the induction voltage Uind of the alternating current commercial power (50Hz) is reduced, the peak value of the interference signal voltage Uint is reduced at the same time, and the interference is eliminated.
In a further embodiment, the filter rectification branch comprises:
the direct current input end of the sorting bridge D3 is respectively connected with the live wire and the zero wire;
a capacitor C47, one end of which is connected to one end of the capacitor C49, the other end of which is connected to one of the ac input terminals of the trimming bridge D3, and the other end of the capacitor C49 is connected to the other ac input terminal of the trimming bridge D3;
a pin 2 of the common-mode inductor L5 is connected to the other end of the C49, and a pin 3 of the common-mode inductor L5 is connected to the other end of the capacitor C47; pin No. 1 of the common mode inductor L5 is connected to one end of C51 and C10, and pin No. 4 of the common mode inductor L5 is connected to the other end of C51 and C10.
By adopting the technical scheme: the capacitor C10 and the capacitor C51 are connected in parallel and play a role in preventing voltage from suddenly changing and absorbing overvoltage in a peak state; the capacitor C47 and the capacitor C49 are connected in series, the withstand voltage of the two capacitors after being connected in series is the sum of the withstand voltages of the two capacitors, the damping effect is achieved, the resistor consumes the energy of overvoltage, the oscillation of the circuit is restrained, and meanwhile, the filtering effect is achieved, and high-frequency and low-frequency interference is filtered; d3 is a rectifier bridge for rectifying voltage; l5 is a common mode inductor, which is connected in series in the circuit, when a common mode interference current flows through the coil, due to the isotropy of the common mode interference current, a magnetic field in the same direction is generated in the coil to increase the inductive reactance of the coil, so that the coil exhibits high impedance and generates a strong damping effect, thereby attenuating the common mode interference current and achieving the purpose of filtering.
In a further embodiment, the anti-surge branch comprises:
a pin 1 of the common-mode inductor L3 is connected to one end of a capacitor C52, a capacitor C9, an overvoltage resistor RV1 and one end of a capacitor C6; a No. 4 pin of the common-mode inductor L3 is connected to the other ends of the capacitor C52, the capacitor C9, the overvoltage resistor RV1 and the capacitor C11;
the other end of the capacitor C6 is connected to one end of the capacitor C11.
By adopting the technical scheme: the voltage-dependent resistor RV1 is matched with a capacitor to form a similar detection voltage, when the input voltage is below the threshold voltage, the resistance value of the voltage-dependent resistor RV1 is very high, so that almost no current flows, if the input voltage exceeds the threshold voltage, the resistance value of the voltage-dependent resistor RV1 is sharply reduced, and large current can be discharged; the function of the four capacitors is the same as that of the capacitors of the filter rectification branch, and the protection and filtering functions are achieved.
In a further embodiment, the interface branch comprises:
one end of the fault current limiter FCL1 is connected to the touch display screen;
one end of the CANT1 is connected to the touch display screen and the anti-surge branch, and the other end is connected to the N line.
By adopting the technical scheme: the FCL1 protects the external fuse from being broken when the current is too high, thereby stopping the power supply.
The invention has the beneficial effects that: an anti-interference capacitor CANT1 is additionally arranged between the touch screen outer frame and the zero line of the commercial power, so that the induced voltage Uind of the commercial power (50Hz) and the voltage Uint of the interference signal (65KHz) flowing on the touch screen outer frame are greatly inhibited under the condition that the outer frame is not connected with the protective ground wire, and stable and effective touch control is realized.
Drawings
Fig. 1 is a connection structure diagram of embodiment 1.
Fig. 2 is a circuit diagram of embodiment 1.
Fig. 3 is a connection structure diagram of the LCC step-down circuit.
Detailed Description
In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the present invention. It will be apparent, however, to one skilled in the art, that the present invention may be practiced without one or more of these specific details. In other instances, well-known features have not been described in order to avoid obscuring the invention.
Normally, the outer frame PE' of the touch screen must be connected to the protective ground PE, which is a basic requirement for the safety of users and electric devices, and a necessary measure for reducing interference.
Under the condition that the outer frame PE 'of the touch screen is connected with the protective ground wire PE, no matter the induced voltage (50Hz) of alternating current commercial power or the interference voltage radiated by the backlight power supply is 0 between the two points of the PE', and therefore stable and effective touch control can be achieved.
However, in some specific cases, the outer frame PE' of the touch screen cannot be connected to the protective ground line PE, and when performing touch control, the related signal interference Uint will act on the receiving line RX at the touch position through a human body, so that an irregular "jumping point" appears at the touch position. In this case, changing the signal voltage frequency of the touch control transmission line TX is also "no complement", and it is difficult to adjust the frequency to a good effect by a software algorithm, because the input port of the reception signal RX is in a broadband high-impedance form, and no touch signal filter is provided in the related touch control panel.
The method for realizing stable touch protection of the interactive intelligent blackboard specifically comprises the following steps:
step one, judging whether a protective ground wire is normally arranged or not, and executing the following steps two to four if the protective ground wire is judged to be abnormally arranged;
step two, measuring the effective value of the induced voltage between the protective ground wire and the outer frame of the touch display screen to be U1And calculating the peak value of the induced voltage
Figure BDA0003033799250000041
The induction voltage Uind is superposed with an interference signal induction voltage Uint;
thirdly, an anti-interference capacitor C is additionally arranged between the touch display screen and a city line zero line N to suppress an interference signal induction voltage Uint;
step four, measuring the effective value of the induced voltage between the protective ground wire and the outer frame of the touch display screen again to be U2The maximum leakage current generated at this time is IL，ILLess than 10mA, which is the maximum current that the human body can bear.
In a further embodiment of the method of the invention,
the first step specifically comprises the following judgment method: setting a predetermined voltage value of an AC voltage phase line to UPE-L1The predetermined voltage value of the working zero line is UPE-N1(ii) a In this embodiment, UPE-L1＝220V，UPE-N1＝0V；
The protection ground wire PE is taken as a public end, and the actual voltage value of an alternating voltage phase line is UPE-L when the working state is detected by using the alternating voltage gear of a common digital multimeter2The voltage value of the working zero line is UPE-N2；
If UPE-L2＝UPE-L1±UPE-L1X 10%, and UPE-N2≈UPE-N1(ii) a The protective earth wire is set normally; for example, when UPE-L2236V/210V, UPE-N2When the voltage is equal to 0.5V/0V, the protection ground PE of the power supply system is set normally.
If UPE-L2≠UPE-L1±UPE-L1X 10%, or UPE-N2To 70 volts, the protective earth line PE is not set properly or is not set. If the measured voltage value deviates greatly, especially the voltage UPE-N of the working neutral line (neutral line) N2When the voltage reaches more than 80V, the setting of the protection ground wire PE of the power supply system is abnormal (no PE or PE interruption is set), and the voltage is recorded as the induction voltage U1。
In a further embodiment, the second step is embodied as: induced voltage U1For disconnecting capacitive contactsControlling the connection between the outer frame PE 'of the display screen and the protective earth PE, measuring the voltage value between the two points PE' and PE by using the AC voltage level of a common digital multimeter, in this embodiment, U1Is 106.5V.
Induced voltage U1It is essentially the induced voltage Uind between the electronic blackboard outer frame PE' and the protective earth PE. The alternating voltage measured by the digital multimeter is an effective value U1(Root Mean Square) means an integration of signals squared in one period, followed by Square averaging.
The definition of valid values is: the amount of work done in one cycle is equal to the amount of work done by a dc voltage equal to this value. For a sinusoidal signal, the peak value Uind is the effective value U1√ 2 times (1.414); the peak value Uind is the effective value U 12 √ 2 times (2.828).
Therefore, the peak induced voltage Uind measured by an oscilloscope displaying the instantaneous value of the signal is 2.828 × 106.5V — 301.2V.
The period of the approximately sinusoidal peak induced voltage Uind is 20ms (50Hz mains waveform), and the induced voltage Uint of the interference signal is also superimposed on the peak induced voltage Uind. The sources of the interference signals are related to the backlight: when the interference signal exists, the noise displayed by the touch measurement software is larger when the touch measurement software is not touched; when touching, the noise around the touch point increases rapidly and causes irregular jumping points. After the Uind voltage is subjected to high-pass filtering by adding 3.13KHz, the maximum amplitude of the induced voltage Uint of the interference signal filtered from the 50Hz sinusoidal peak induced voltage Uind is about 15V, and the frequency of the induced voltage Uint of the interference signal is about 65 KHz.
At this time, step three is executed: an anti-interference capacitor C is additionally arranged between the touch display screen and a city line zero line N to inhibit an interference signal induction voltage Uint; the capacity of the anti-interference capacitor C is 0.1uF, and the withstand voltage is 1000V. For a 65KHZ interference signal, the capacitive reactance of the 0.1uf capacitor is very low, which is equivalent to that the signal is directly connected to the zero line.
The scheme of the above embodiment is next verified:
the calculation formula according to the capacitance reactance Xc is as follows:
Figure BDA0003033799250000061
where f is the frequency of the loading signal, in units: hz (hertz) C is the capacity of the capacitor used, unit: f (farad). When the capacity of the capacitor is 0.1uF, the capacitive reactance Xc of the commercial power with the frequency f of 50Hz is 32K omega; if the frequency f of the interference signal is 50KHz, the corresponding capacitive reactance Xc is 32 Ω. The higher the frequency f, the smaller the capacitive reactance Xc, so the capacitive reactance will be lower for a 65khz interference signal. Therefore, when the touch screen outer frame PE 'is not connected to the protection ground PE, no matter the commercial power has a frequency f of 50Hz or the interference signal has a frequency f of 65KHz, the impedance between PE' and PE is ∞ Ω, and the interference cannot be introduced into the ground for elimination.
After an anti-interference capacitor CANT1 with the capacity of 0.1uF is connected between an outer frame PE' of the touch screen and a zero line N of a mains supply, the capacitance of the capacitor is very low for an interference signal, the interference signal is guided into the ground due to the bypass effect of CANT1, the effective value of the induction voltage Uind of the alternating-current mains supply (50Hz) is reduced, and the peak value of the voltage Uint of the interference signal (65KHz) is reduced at the same time, so that interference is eliminated. The value of the capacitance Canti is obtained by measuring the frequency of the interference signal, and the capacitance reactance is required to be below 30 Ω for the interference, so that the capacitance value of the capacitance is calculated by reverse calculation after the frequency of the interference signal is known, and the value of the capacitance is 0.1uf in the embodiment; some try to shield interference by software algorithm, but this increases computational complexity, so a higher-end CPU needs to be selected to process touch data, which increases a large cost, and reduces touch speed and sensitivity, because some effective data may be lost while shielding interference, interference is not eliminated, and it is only attempted to avoid the past by a computational method, which obviously has an unsatisfactory effect; in the embodiment, a capacitor CANTI is added to the power input terminal, as shown in fig. 2.
Realize touch-control protection system is stabilized to interactive wisdom blackboard, include: the device comprises a filtering rectification branch, an anti-surge branch and an interface branch. The filtering and rectifying branch is connected with the live wire and the zero wire; the anti-surge branch is connected with the filtering rectification branch; the interface branch circuit is connected in anti-surge branch circuit, filtering rectification branch circuit and touch-control display screen, the interface branch circuit is equipped with electric capacity CANT 1.
In a further embodiment, the filter rectification branch comprises: the capacitor comprises a trimming bridge D3, a capacitor C47, a capacitor C49, a common mode inductor L5, a capacitor C51 and a capacitor C10. The concrete connection mode is as follows: the input ends of the sorting bridge D3 are connected to the live wire and the neutral wire respectively. One end of the capacitor C47 is connected to one end of the capacitor C49, the other end of the capacitor C3578 is connected to one of the alternating current input ends of the tidying bridge D3, and the other end of the capacitor C49 is connected to the other input end of the tidying bridge D3. Pin 2 of the common mode inductor L5 is connected to the other end of the C49, and pin 3 of the common mode inductor L5 is connected to the other end of the capacitor C47; pin No. 1 of the common mode inductor L5 is connected to one end of the capacitor C51 and one end of the capacitor C10, and pin No. 4 of the common mode inductor L5 is connected to the other end of the capacitor C51 and the other end of the capacitor C10. The capacitor C10 and the capacitor C51 are connected in parallel and play a role in preventing voltage from suddenly changing and absorbing overvoltage in a peak state; the capacitor C47 and the capacitor C49 are connected in series, the withstand voltage of the two capacitors after being connected in series is the sum of the withstand voltages of the two capacitors, the damping effect is achieved, the resistor consumes the energy of overvoltage, the oscillation of the circuit is restrained, and meanwhile, the filtering effect is achieved, and high-frequency and low-frequency interference is filtered; d3 is a rectifier bridge for rectifying voltage; the L5 transformer consists of two inductors and has the function of changing alternating current into direct current.
In a further embodiment, the anti-surge branch comprises: common mode inductance L3, capacitor C52, capacitor C9 are over-voltage sensing resistor RV1, capacitor C6 and capacitor C11. The No. 1 pin of the common-mode inductor L3 is connected to one end of a capacitor C52, a capacitor C9, an overvoltage resistor RV1 and a capacitor C6; a No. 4 pin of the common-mode inductor L3 is connected to the other ends of the capacitor C52, the capacitor C9, the overvoltage resistor RV1 and the capacitor C11; pin 3 of the common mode inductor L3 is connected to one end of the capacitor C10, and pin 2 of the common mode inductor L3 is connected to the other end of the capacitor C10. The other end of the capacitor C6 is connected to one end of the capacitor C11. The voltage-dependent resistor RV1 is matched with a capacitor to form a similar detection voltage, when the input voltage is below the threshold voltage, the resistance value of the voltage-dependent resistor RV1 is very high, so that almost no current flows, if the input voltage exceeds the threshold voltage, the resistance value of the voltage-dependent resistor RV1 is sharply reduced, and large current can be discharged; the function of the four capacitors is the same as that of the capacitors of the filter rectification branch, and the protection and filtering functions are achieved.
In a further embodiment, as shown in fig. 3, the voltage reduction circuit of the LCC voltage reduction circuit adjusts output to convert ac voltage into dc 24V when input voltage and load change in a large range, and the change of switching frequency is relatively small, which is beneficial to improving electromagnetic compatibility of the system and improving efficiency;
the left side of the transformer is provided with a resonant capacitor, an inductor and an isolation transformer form an lc resonant circuit, an lc controller controls the turn-off and turn-on of 2 MOS tubes on the left side, a voltage reference is provided by an optocoupler through the voltage reference, and a diode is replaced by n-MOS on the right side of the transformer, so that the turn-on voltage is reduced, and the efficiency is further improved; the rectification controller controls the diode switch, and the rear end is provided with the filter capacitor to further filter out ripples and interference.
In a further embodiment, the interface branch comprises: a fault current limiter FCL1 and an anti-interference capacitor can 1. One end of the fault current limiter FCL1 is connected to the touch display screen; one end of the CANT1 is connected to the touch display screen and the anti-surge branch, and the other end is connected to the anti-surge branch and the filtering rectification branch.
The FCL1 protects the external fuse from being broken when the voltage is too high, and thus the power supply is stopped.
For the leakage current I in the above systemLAnd (3) calculating: after an anti-interference capacitor CANT1 with the capacity of 0.1uF is connected between an outer frame PE' of the touch screen and a zero line N of commercial power, due to the bypass effect of CANT1, the effective value of the alternating current commercial power (50Hz) induced voltage Uind measured by the multimeter is reduced to 7.1V, and the corresponding peak value is Vx √ 2 ═ 10V. According to ohm's law, after the 0.1uF anti-interference capacitor CANT1 is connected, the maximum leakage current I possibly generated by the 50Hz alternating current commercial powerLThe current is 10Vp/32K omega which is 0.313mA, and even if the current passes through the human body and is grounded, the relevant electric or human hazard can not be generated.
Meanwhile, the withstand voltage of the anti-interference capacitor CANT1 is calculated, and according to the corresponding relation between the effective value and the peak value of the alternating voltage, the effective value is that the peak value of 220V alternating current commercial power is V2 times (2.828) of the effective value, namely 311V.
According to the fluctuation specification of the alternating mains voltage +/-10% in China, the maximum allowable effective value of the alternating mains voltage is 242V, the corresponding peak value is 342V, and a series of nonpolar safety-type capacitors with withstand voltage of 1000V are recommended to be selected.
In this embodiment, a capacitor is added to connect with the N line, and for a 65KHZ interference signal, the capacitive reactance of the 0.1uf capacitor is very low, which is equivalent to that this signal is directly connected to the zero line, as described above, the zero line N is an interference signal connected to the ground at the transformer end, which is equivalent to that the signal is connected to the ground, so that interference is eliminated, and the touch is normal, and only one capacitor solves the problem, thereby reducing the cost, and being simple and reliable.
As noted above, while the present invention has been shown and described with reference to certain preferred embodiments, it is not to be construed as limited thereto. Various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (7)

1. A method for realizing stable touch protection of an interactive intelligent blackboard is characterized by comprising the following steps:
judging whether a protective ground wire is normally arranged or not, and executing the following steps if the protective ground wire is judged to be abnormally arranged;
the effective value of the induced voltage between the protective ground wire and the outer frame of the touch display screen is measured to be U1And calculating the peak value of the induced voltage
Figure FDA0003033799240000011
The induction voltage Uind is superposed with an interference signal induction voltage Uint;
an anti-interference capacitor C is additionally arranged between the touch display screen and a city line zero line N to inhibit an interference signal induction voltage Uint;
the effective value of the induction voltage between the protective ground wire and the outer frame of the touch display screen is measured again to be U2The maximum leakage current generated at this time is IL，IL＜10mA。
2. The method for realizing stable touch protection of the interactive intelligent blackboard according to claim 1, wherein the capacity of the anti-interference capacitor C is 0.1uF, and the withstand voltage is 1000V.
3. The method of claim 1, wherein the interactive intelligent blackboard is capable of stable touch protection,
the judgment standard for judging whether the protection ground wire is normally set is as follows: under the condition of normally connecting a protective earth wire PE, the preset voltage value of an alternating voltage phase line is set to be UPE-L1The predetermined voltage value of the working zero line is UPE-N1；
Detecting the actual voltage value of the AC voltage phase line as UPE-L in working state2The voltage value of the working zero line is UPE-N2；
If UPE-L2＝UPE-L1±UPE-L1X 10%, and UPE-N2≈UPE-N1(ii) a The protective earth wire is set normally;
if UPE-L2≠UPE-L1±UPE-L1X 10%, or UPE-N2Up to 70V or more, the protective earth PE is not normally set or is not set.
4. The system for realizing stable touch protection of an interactive intelligent blackboard according to any one of claims 1 to 3, comprising:
the filtering and rectifying branch is connected with the live wire and the zero line;
the anti-surge branch is connected with the filtering and rectifying branch;
the LCC voltage reduction circuit is connected to the rectifying branch;
the interface branch circuit is connected in anti-surge branch circuit, filtering rectification branch circuit and touch-control display screen, the interface branch circuit is equipped with electric capacity CANT 1.
5. The system for realizing stable touch protection of interactive intelligent blackboard according to claim 4,
the filtering rectification branch circuit comprises:
the input end of the sorting bridge D3 is respectively connected with the live wire and the zero wire;
a capacitor C47, one end of which is connected to one end of the capacitor C49, the other end of which is connected to one of the ac input terminals of the trimming bridge D3, and the other end of the capacitor C49 is connected to the other input terminal of the trimming bridge D3;
a pin 2 of the common-mode inductor L5 is connected to the other end of the C49, and a pin 3 of the common-mode inductor L5 is connected to the other end of the capacitor C47; pin No. 1 of the common mode inductor L5 is connected to one end of the capacitor C51 and one end of the capacitor C10, and pin No. 4 of the common mode inductor L5 is connected to the other end of the capacitor C51 and the other end of the capacitor C10.
6. The system for realizing stable touch protection of interactive intelligent blackboard according to claim 4,
the surge protection branch includes:
a pin 1 of the common-mode inductor L3 is connected to one end of each of capacitors C52, C9, a piezoresistor RV1 and a capacitor C6; the No. 4 pin of the common-mode inductor L3 is connected to the other ends of the resistors C52, C9, the overvoltage resistor RV1 and the resistor C11;
the other end of the capacitor C6 is connected to one end of C11.
7. The system for realizing stable touch protection of interactive intelligent blackboard according to claim 4,
the interface branch comprises:
one end of the fault current limiter FCL1 is connected to the touch display screen;
one end of the CANT1 is connected to the touch display screen and the anti-surge branch, and the other end is connected to the N line.
CN202110437729.5A 2021-04-22 2021-04-22 System and method for realizing stable touch protection of interactive intelligent blackboard Pending CN114371791A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202110437729.5A CN114371791A (en) 2021-04-22 2021-04-22 System and method for realizing stable touch protection of interactive intelligent blackboard

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202110437729.5A CN114371791A (en) 2021-04-22 2021-04-22 System and method for realizing stable touch protection of interactive intelligent blackboard

Publications (1)

Publication Number Publication Date
CN114371791A true CN114371791A (en) 2022-04-19

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Family Applications (1)

Application Number Title Priority Date Filing Date
CN202110437729.5A Pending CN114371791A (en) 2021-04-22 2021-04-22 System and method for realizing stable touch protection of interactive intelligent blackboard

Country Status (1)

Country Link
CN (1) CN114371791A (en)

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