CN216792859U

CN216792859U - Anti-power frequency interference receiving circuit and capacitance pen

Info

Publication number: CN216792859U
Application number: CN202123323573.2U
Authority: CN
Inventors: 丁新满; 李卓珺; 詹梓煜
Original assignee: Maxeye Smart Technologies Co ltd
Current assignee: Maxeye Smart Technologies Co ltd
Priority date: 2021-12-27
Filing date: 2021-12-27
Publication date: 2022-06-21
Anticipated expiration: 2031-12-27

Abstract

The utility model discloses a receiving circuit and a capacitance pen for resisting power frequency interference, wherein the receiving circuit for resisting power frequency interference comprises: the signal input end of the charge amplifying circuit receives a DSSS signal sent by the touch terminal, the charge amplifying circuit is used for amplifying charges of the DSSS signal and outputting the amplified DSSS signal, and the charge amplifying circuit is provided with a feedback branch; the first end of the resistor is connected with the first end of the feedback branch, and the second end of the resistor is connected with the second end of the feedback branch; the input end of the voltage amplifying circuit is connected with the output end of the charge amplifying circuit and is used for amplifying and outputting the input voltage; the utility model only converts the original charge amplifying circuit of the receiving circuit into the capacitance pen resisting the power frequency interference by adding the resistor without greatly changing the volume of the receiving circuit, thereby inhibiting the power frequency interference and simultaneously reducing the occupation of the internal space of the capacitance pen as much as possible.

Description

Anti-power frequency interference receiving circuit and capacitance pen

Technical Field

The utility model relates to the technical field of capacitance pens, in particular to a power frequency interference resistant receiving circuit and a capacitance pen.

Background

At present, a capacitance pen is generally powered by a battery without being grounded. When the capacitive pen is used for writing normally, a user holds the capacitive pen by hands, and the user can still transmit power frequency interference signals to the capacitive pen by the hands as a conductor with high impedance. The receiving circuit of the capacitance pen is normally coupled with the received modulation signal to be a DSSS modulation signal sent by a screen, the frequency range of the DSSS modulation signal is 50-200 KHz, and the voltage of the signal coupled to the pen point is within 1V. The frequency of the power frequency interference signal is generally about 50Hz, and when the oscilloscope probe is suspended, a strong power frequency signal can be measured; when the oscilloscope is used for measuring a human body, a power frequency interference signal with the waveform amplitude of dozens of volts can also be read from the oscilloscope.

When a user uses the capacitance pen, the power frequency interference signal can be transmitted to the capacitance pen through hands and is superposed with the DSSS signal to cover the DSSS signal, so that the demodulation of the RX signal by the capacitance pen is influenced. Because the space of the capacitance pen is very tight, the capacitance pen is not suitable for filtering power frequency interference signals by selecting an integrated device with a larger ceramic filter and the like, and the problem that how to reduce the occupation of the internal space of the capacitance pen as much as possible while inhibiting the power frequency interference becomes urgent to be solved.

SUMMERY OF THE UTILITY MODEL

The utility model mainly aims to provide a power frequency interference resistant capacitance pen, aiming at inhibiting power frequency interference by using a minimum volume circuit.

In order to achieve the above object, the present invention provides an anti-power frequency interference receiving circuit, which includes:

the signal input end of the charge amplification circuit is used for inputting a DSSS signal received by the capacitive pen and sent by the touch terminal, and outputting the DSSS signal after performing charge amplification, and the charge amplification circuit is provided with a feedback branch circuit;

the input end of the voltage amplifying circuit is connected with the output end of the charge amplifying circuit and is used for performing voltage amplification on the DSSS signal output by the charge amplifying circuit and then outputting the DSSS signal;

a resistor, a first end of the resistor being connected to the first end of the feedback branch, a second end of the resistor being connected to the second end of the feedback branch;

the resistor is connected in parallel at two ends of a feedback branch of the charge amplification circuit, and forms a high-pass filter circuit with the charge amplification circuit, so as to filter the DSSS signal received by the capacitance pen.

Optionally, the charge amplifying circuit includes a first operational amplifier and a second capacitor;

the inverting input end of the first operational amplifier is a signal input end of the charge amplifying circuit, the inverting input end of the first operational amplifier is connected with the first end of the second capacitor, the non-inverting input end of the first operational amplifier is connected with a first direct-current power supply, the first power supply end of the first operational amplifier and the second power supply end of the first operational amplifier are respectively connected with a second direct-current power supply, the output end of the first operational amplifier is a signal output end of the charge amplifying circuit, the output end of the first operational amplifier is connected with the second end of the second capacitor, and the ground end of the first operational amplifier is grounded.

Optionally, the voltage amplifying circuit includes a second operational amplifier, a second resistor, and a third resistor;

the first end of the second resistor is the input end of the voltage amplifying circuit, the second end of the second resistor is respectively connected with the inverting input end of the second operational amplifier and the first end of the third resistor, the non-inverting input end of the second operational amplifier is connected with a third direct current power supply, the first power end of the second operational amplifier and the second power end of the second operational amplifier are respectively connected with a fourth direct current power supply, the output end of the second operational amplifier is the output end of the voltage amplifying circuit, the output end of the second operational amplifier is connected with the first end of the third resistor, and the ground end of the second operational amplifier is grounded.

Optionally, the receiving circuit for resisting power frequency interference further includes a filter circuit;

the input end of the filter circuit is connected with the signal output end of the charge amplification circuit, and the output end of the filter circuit is connected with the input end of the voltage amplification circuit and is used for inhibiting a power frequency signal in the DSSS signals output by the charge amplification circuit;

optionally, the filter circuit is a second capacitor, a first end of the second capacitor is an input end of the filter circuit, and a second end of the second capacitor is an output end of the filter circuit.

The utility model also provides a receiving circuit for resisting power frequency interference, which is characterized by comprising the following components:

the signal input end of the charge amplification circuit receives a DSSS signal sent by the touch terminal, and the charge amplification circuit is used for performing charge amplification on the DSSS signal and outputting the DSSS signal;

the input end of the filter circuit is connected with the signal output end of the charge amplification circuit and is used for filtering interference signals;

and the input end of the voltage amplifying circuit is connected with the output end of the filter circuit and is used for amplifying and outputting the input voltage.

The utility model also provides a capacitance pen which is characterized by comprising the receiving circuit for resisting the power frequency interference; or, the receiving circuit comprises the anti-power frequency interference receiving circuit.

Optionally, the capacitance pen further comprises a demodulation unit;

the input end of the demodulation unit is connected with the output end of the voltage amplification circuit and used for demodulating the input DSSS signal and outputting the demodulated signal.

According to the technical scheme, the high-pass filter circuit is arranged, on the basis of the original charge amplification circuit, a feedback branch of the charge amplification circuit is connected with a resistor in parallel, so that the charge amplification circuit is changed into the high-pass filter circuit, the cut-off frequency of the high-pass filter circuit is in negative correlation with the resistance value of the resistor, and in the high-pass filter circuit, the smaller the resistance value of the resistor is, the higher the frequency of the DSSS signal is, the smaller the gain attenuation is, so that the low-frequency power frequency signal can be filtered under the condition that the gain attenuation of the high-frequency DSSS signal is smaller, and the suppression of power frequency interference is realized; according to the utility model, the high-pass filter circuit is arranged, so that when the capacitive pen receives the coupled DSSS signal, the gain attenuation degree of the charge amplification circuit can be reduced as much as possible under the condition of filtering the high-frequency power frequency signal, and therefore, the problem that when a user uses the capacitive pen, the power frequency signal in the environment is coupled into the receiving circuit of the capacitive pen by the pen point of the capacitive pen through hands and the DSSS signal, so that the DSSS signal coupled between the screen and the capacitive pen is submerged, and the capacitive pen fails is solved.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the structures shown in the drawings without creative efforts.

FIG. 1 is a block diagram of a capacitive stylus according to an embodiment of the present invention;

FIG. 2 is a block diagram of a capacitive stylus according to an embodiment of the present invention;

FIG. 3 is a schematic circuit diagram of a capacitive stylus according to an embodiment of the present invention;

fig. 4 is a schematic circuit diagram of a capacitance pen according to an embodiment of the utility model.

The reference numbers illustrate:

reference numerals	Name (R)	Reference numerals	Name (R)
				10	High-pass filter circuit	V1	Power frequency signal source
11	Charge amplification circuit	U1～U2	First to second inverting amplifiers
				12	Resistor with a resistor element	C1	Coupler
20	Voltage amplifying circuit	C2～C3	Second to third capacitors
				30	Filter circuit	R1～R4	First to fourth capacitorsCapacitor with a capacitor element
40	Demodulation circuit

The implementation, functional features and advantages of the objects of the present invention will be further explained with reference to the accompanying drawings.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It should be noted that, if directional indications (such as up, down, left, right, front, and back … …) are involved in the embodiment of the present invention, the directional indications are only used to explain the relative positional relationship between the components, the movement situation, and the like in a specific posture (as shown in the drawing), and if the specific posture is changed, the directional indications are changed accordingly.

In addition, if there is a description of "first", "second", etc. in an embodiment of the present invention, the description of "first", "second", etc. is for descriptive purposes only and is not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In addition, technical solutions between various embodiments may be combined with each other, but must be realized by a person skilled in the art, and when the technical solutions are contradictory or cannot be realized, such a combination should not be considered to exist, and is not within the protection scope of the present invention.

The utility model provides a power frequency interference resistant receiving circuit which is applied to a capacitance pen.

Referring to fig. 1 to 4, in an embodiment, the high-pass filter circuit 10 includes:

a signal input end of the charge amplifying circuit 11 is used for inputting a DSSS signal received by the capacitive pen and sent by the touch terminal, and outputting the DSSS signal after performing charge amplification, and the charge amplifying circuit 11 has a feedback branch;

the input end of the voltage amplifying circuit 20 is connected to the output end of the charge amplifying circuit 11, and is configured to amplify and output the DSSS signal output by the charge amplifying circuit 11;

a resistor 12, a first end of the resistor 12 being connected to a first end of the feedback branch, a second end of the resistor 12 being connected to a second end of the feedback branch;

the resistor 12 is connected in parallel to two ends of a feedback branch of the charge amplifying circuit 11, and forms a high-pass filter circuit 10 with the charge amplifying circuit 11, for filtering the DSSS signal received by the capacitance pen.

In this embodiment, when the capacitive pen is used, the touch screen terminal may implement operations such as screen and pen tip synchronization and command transmission by transmitting a DSSS signal to communicate with the active pen, when the capacitive pen is used, a coupling capacitor is formed between a pen tip of the capacitive pen and a terminal screen, the DSSS signal transmitted by the screen is input to a receiving circuit of the capacitive pen through coupling between the screen and the pen tip, the DSSS signal is amplified by the receiving circuit and then output, and the capacitive pen analyzes the amplified DSSS signal to obtain a corresponding DSSS code. The capacitive stylus can be an active capacitive stylus or a passive capacitive stylus. As shown in fig. 3, the coupling capacitor is a first capacitor C1; the DSSS signal is a DSSS signal of a screen to which a receiving circuit of the capacitive pen is coupled, and may be other signals requiring interference suppression in other embodiments.

It can be understood that the present invention converts the charge amplifying circuit 11 into the high-pass filter circuit 10 by providing the high-pass filter circuit 10 and connecting a resistor 12 in parallel to both ends of the feedback branch of the charge amplifying circuit 11. The charge amplifying circuit 11 has the capability of amplifying the electric charge of the DSSS signal, when the charge amplifying circuit 11 connects the resistors in parallel at two ends of the feedback branch, the formed capacitance pen 13 resisting the power frequency interference can filter the low-frequency signal and pass the high-frequency signal, and when the high-frequency signal passes through the high-frequency filter circuit 10, the high-frequency signal is amplified according to the transfer function.

In the high-frequency filter circuit 10, the cut-off frequency of the high-pass filter circuit 10 is inversely related to the resistance of the first resistor, and when the resistance of the first resistor is smaller, the cut-off frequency of the high-pass filter circuit 10 is larger, and the filtering effect on the low-frequency signal is better. In the high-pass filter circuit 10, when the resistance of the first resistor R1 is larger, the gain attenuation of the DSSS signal is smaller, and therefore, the resistance of the first resistor R1 exceeds a certain range, which may distort the DSSS signal because the resistance is too small. The resistance value of the first resistor R1 is kept within a certain range, so that the low-frequency power frequency signal can be filtered under the condition that the gain attenuation of the high-frequency DSSS signal is small, and the suppression of power frequency interference is realized; according to the utility model, the high-pass filter circuit 10 is arranged, so that when the capacitive pen receives the coupled DSSS signal, the gain attenuation degree of the charge amplification circuit 11 can be reduced as much as possible under the condition of filtering the high-frequency power frequency signal, and therefore, the problem that when a user uses the capacitive pen, the power frequency signal in the environment is coupled into the receiving circuit of the capacitive pen by the pen point of the capacitive pen through hands and the DSSS signal, the DSSS signal coupled between a screen and the capacitive pen is submerged, the capacitive pen is disabled is solved, and the function of inhibiting power frequency interference by using a circuit with the smallest volume is realized.

In one embodiment, the charge amplifying circuit 11 includes a first operational amplifier U1, a first capacitor C1, and a second capacitor C2;

an inverting input terminal of the first operational amplifier U1 is a signal input terminal of the charge amplifying circuit 11, an inverting input terminal of the first operational amplifier U1 is connected to a first terminal of the second capacitor C2, a non-inverting input terminal of the first operational amplifier U1 is connected to a first dc power supply, a first power terminal of the first operational amplifier U1 and a second power terminal of the first operational amplifier U1 are respectively connected to a second dc power supply, an output terminal of the first operational amplifier U1 is a signal output terminal of the charge amplifying circuit 11, an output terminal of the first operational amplifier U1 is connected to a second terminal of the second capacitor C2, and a ground terminal of the first operational amplifier U1 is grounded.

In this embodiment, the first dc power supply is a reference voltage for providing a reference voltage for the charge amplifying circuit 11, when a DSSS signal is input to the charge amplifying circuit 11, the charge amplifying circuit 11 amplifies the DSSS signal on the basis of the reference voltage, the second dc power supply is a capacitor pen supply voltage, and the first power supply terminal of the first operational amplifier U1 and the second power supply terminal of the first operational amplifier U1 are used for supplying power to the first operational amplifier U1; the second capacitor C2 is a feedback branch of the charge amplifying circuit 11.

Specifically, the gain of the charge amplification circuit 11 is

When a DSSS signal is input to the inverting input terminal of the first operational amplifier U1, the first operational amplifier U1 performs inverting amplification on the DSSS signal, wherein the transfer function of the high-pass filter circuit 10 is

ω ═ 2 π f. As can be seen from the transfer function, when the resistance value of the first resistor R1 is larger, the gain attenuation of the signal is smaller, and the amplification factor of the high-pass filter circuit 10 is closer to the amplification factor of the charge amplifier circuit 11The multiple is large, so that the resistance value of the first resistor R1 is kept within a certain range, and the low-frequency power frequency signal can be suppressed under the condition that the gain attenuation of the high-frequency DSSS signal is small, so that the suppression of power frequency interference is realized; moreover, the cut-off frequency of the high-pass filter circuit 10 is inversely related to the resistance of the first resistor R1, when the resistance of the first resistor R1 is smaller, the cut-off frequency of the high-pass filter circuit 10 is larger, the filtering effect on the low-frequency signal is better, and when the resistance of the first resistor R1 exceeds a certain range, the DSSS signal is distorted because the resistance is too small. Therefore, the high-pass filter circuit 10 can reduce the gain attenuation degree of the charge amplification circuit 11 as much as possible under the condition of filtering the high-frequency power frequency signal, so that the problem that when a user uses the capacitance pen, the power frequency signal in the environment is coupled into the receiving circuit of the capacitance pen by the pen point of the capacitance pen through the hand and the DSSS signal, the DSSS signal coupled between the screen and the capacitance pen is submerged, the capacitance pen is disabled is solved, and the function of inhibiting power frequency interference by using a minimum volume circuit is realized.

Referring to fig. 1 and 3, in an embodiment, the voltage amplifying circuit 20 includes a second operational amplifier U2, a second resistor R2, and a third resistor R3;

a first end of the second resistor R2 is an input end of the voltage amplifying circuit 20, a second end of the second resistor R2 is connected to an inverting input end of the second operational amplifier U2 and a first end of the third resistor R3, a non-inverting input end of the second operational amplifier U2 is connected to a third dc power supply, a first power end of the second operational amplifier U2 and a second power end of the second operational amplifier U2 are connected to a fourth dc power supply, an output end of the second operational amplifier U2 is an output end of the voltage amplifying circuit 20, an output end of the second operational amplifier U2 is connected to a first end of the third resistor R3, and a ground end of the second operational amplifier U2 is grounded.

In this embodiment, the third dc power supply is the same reference power supply as the first dc power supply and is configured to provide a reference voltage for the voltage amplifying circuit 20, when the DSSS signal amplified by the charge amplifying circuit 11 is input to the voltage amplifying circuit 20, the voltage amplifying circuit 20 amplifies the DSSS signal on the basis of the added reference voltage, and the fourth dc power supply is the same power supply as the second dc power supply and is configured to provide power for the second operational amplifier U2.

When a user uses the capacitive pen, the DSSS signal is coupled to the high-pass filter circuit 10 through the screen and the pen tip of the capacitive pen, the high-pass filter circuit 10 performs low-frequency filtering on the DSSS signal, and performs charge amplification on the input DSSS signal, so that the input DSSS signal is converted from weak charges into a larger voltage and output, the voltage amplifier circuit 30 performs secondary amplification on the input voltage by the second inverting amplifier U2 and outputs the amplified voltage, wherein the voltage amplification gain of the voltage amplifier circuit 30 is equal to

Therefore, the capacitance pen can eliminate the interference of the power frequency signal when receiving the DSSS signal.

The voltage amplifying circuit 30 amplifies the input voltage twice according to the transfer function thereof, so that the output end of the voltage amplifying circuit 30 outputs the amplified DSSS signal, and the input DSSS signal is converted from a weak charge amount to a voltage output that can be demodulated by a subsequent circuit. Therefore, by arranging the voltage amplifying circuit 30, the capacitive pen can perform interference suppression on the DSSS signal interfered by the low-frequency power frequency signal when being used, and filter the power frequency signal, so that the capacitive pen can accurately demodulate the DSSS signal.

In the capacitance pen, only the original charge amplifying circuit 11 of the receiving circuit is converted into the high-pass filter circuit 10 by adding the resistor 12, and the size of the receiving circuit is not greatly changed, so that the capacitance pen is prevented from power frequency interference by using a minimum-size circuit.

Referring to fig. 1 and 3, in an embodiment, the capacitance pen further includes a filter circuit 30;

the input end of the filter circuit 30 is connected to the output end of the high-pass filter circuit 10, and the output end of the filter circuit 30 is connected to the input end of the voltage amplifier circuit 30, and is configured to suppress a power frequency signal in the DSSS signal output by the charge amplifier circuit.

In this embodiment, the filter circuit 30 is a second capacitor C2, the first terminal of the second capacitor C2 is an input terminal of the filter circuit 30, and the second terminal of the second capacitor C2 is an output terminal of the filter circuit 30.

Specifically, after the DSSS signal is subjected to low-frequency filtering by the high-pass filtering circuit 10, there is still less low-frequency clutter interference, and the unfiltered clutter may interfere with the demodulation process of the DSSS signal when the user uses the capacitive pen, so that after the pen tip of the capacitive pen captures the DSSS signal emitted from the screen, the DSSS signal is submerged by the power frequency signal, and thus the capacitive pen cannot accurately demodulate the signal. Therefore, in order to enable the capacitance pen to accurately receive the command sent by the terminal, the input voltage, i.e., the input information subjected to charge amplification and power frequency suppression, needs to be subjected to secondary filtering, so as to obtain a pure DSSS signal. Therefore, the input voltage needs to be filtered twice. Because only the filter circuit 30, namely the second capacitor C2, which realizes simple functions is added in the capacitive pen, and the circuit of the capacitive pen for receiving the DSSS signals is not greatly changed in size, the capacitive pen is prevented from power frequency interference by using a minimum-size circuit.

The utility model also provides a receiving circuit for resisting power frequency interference, which is applied to the capacitance pen.

Referring to fig. 2 and fig. 3, in an embodiment, the receiving circuit for resisting power frequency interference includes:

a charge amplifying circuit 11, a signal input end of the charge amplifying circuit 11 receiving the DSSS signal sent by the terminal, and configured to perform charge amplification on the DSSS signal and output the DSSS signal;

the input end of the filter circuit 30 is connected with the signal output end of the charge amplifying circuit 11, and is used for filtering interference signals;

and an input end of the voltage amplifying circuit 20 is connected with an output end of the filter circuit 30, and is used for amplifying and outputting the input voltage.

In this embodiment, when the capacitive pen is used, the touch screen terminal may implement operations such as screen and pen tip synchronization and command transmission by transmitting a DSSS signal to communicate with the active pen, when the capacitive pen is used, a coupling capacitor is formed between a pen tip of the capacitive pen and a terminal screen, the DSSS signal transmitted by the screen is input to a receiving circuit of the capacitive pen through coupling between the screen and the pen tip, the DSSS signal is amplified by the receiving circuit and then output, and the capacitive pen analyzes the amplified DSSS signal to obtain a corresponding DSSS code. The capacitive pen can be an active capacitive pen or a passive capacitive pen, and can also be other intelligent pens such as a touch pen; the coupling capacitor is a first capacitor C1; the DSSS signal is a DSSS signal of a screen to which a receiving circuit of the capacitive pen is coupled, and may be other signals requiring interference suppression in other embodiments.

The filter circuit 30 is a second capacitor C2, a first terminal of the second capacitor C2 is an input terminal of the filter circuit 30, and a second terminal of the second capacitor C2 is an output terminal of the filter circuit 30.

Specifically, the present invention provides the filter circuit 30, and the charge amplification circuit 11 has the capability of performing charge amplification on the DSSS signal, and amplifies input weak charges to a larger voltage when the DSSS signal is input to the charge amplification circuit 11. After the electric charge amplification is carried out on the DSSS signal through the electric charge amplification circuit 11, a power frequency signal in the air is manually transmitted into the receiving circuit of the capacitance pen, the DSSS signal receives interference of the power frequency signal, and when a user uses the capacitance pen, the demodulation process of the DSSS signal is interfered. After a pen point of the capacitive pen captures a DSSS signal sent by a screen, the DSSS signal is submerged by a power frequency signal, so that the capacitive pen cannot accurately demodulate the signal. Therefore, in order to enable the capacitance pen to accurately receive the command sent by the terminal, the input voltage, i.e., the DSSS signal passing through the charge amplification circuit 11, needs to be filtered, so as to obtain a pure DSSS signal.

The voltage amplifying circuit 30 amplifies the input voltage twice according to the gain thereof, so that the output end of the voltage amplifying circuit 30 outputs the amplified DSSS signal, and the input DSSS signal is converted from a weak amount of electric charge to a voltage output that can be demodulated by a subsequent circuit.

In the capacitance pen, only the filter circuit 30, namely the third capacitor C3 is added between the charge amplifying circuit 11 and the voltage amplifying circuit 20 of the receiving circuit, and the size of the receiving circuit is not greatly changed, so that the capacitance pen is suppressed from power frequency interference by using a minimum-size circuit.

The utility model further provides a capacitance pen.

Referring to fig. 1 and 3, in an embodiment, a receiving circuit for resisting power frequency interference is included; or, another receiving circuit resisting power frequency interference is included.

The capacitance pen further comprises a demodulation unit 40;

the input end of the demodulating unit 40 is connected to the output end of the voltage amplifying circuit 20, and is configured to demodulate the input DSSS signal and output the demodulated signal.

In this embodiment, when the capacitive pen is used, a coupling capacitor is formed between a pen point of the capacitive pen and a terminal screen, and the pen point of the capacitive pen can accurately capture and couple small screen charges to obtain a DSSS signal and output the DSSS signal, which is obtained by coupling a receiving circuit of the capacitive pen with the screen.

Specifically, when the user uses the capacitive pen, the DSSS signal is coupled to the coupling module 20 through the screen and is input to the high-pass filter circuit 10, when the user passes through the high-pass filter circuit 10, the high-pass filter circuit 10 performs low-frequency filtering on the DSSS signal, and performs charge amplification on the input DSSS signal, so that the input DSSS signal is converted from weak charges into a larger voltage for output, and the voltage amplifier circuit 30 performs secondary amplification on the input voltage for output, so that the capacitive pen can eliminate interference of the power frequency signal and successfully demodulate the DSSS signal. The demodulation unit 40 demodulates an execution signal according to the input DSSS signal, and outputs the execution signal to the control part of the capacitive pen to control the capacitive pen to work. In addition, in the capacitance pen, only the original charge amplifying circuit 11 of the receiving circuit is converted into the high-pass filter circuit 10 by adding the resistor 12, and the size of the receiving circuit is not greatly changed, so that the capacitance pen is prevented from power frequency interference by using a minimum-size circuit.

The above description is only an alternative embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications and equivalents of the technical solutions of the present invention that are made by using the contents of the specification and the drawings or directly/indirectly applied to other related technical fields are included in the scope of the present invention.

Claims

1. The utility model provides an anti power frequency interference's receiving circuit for the electric capacity pen, its characterized in that, anti power frequency interference's receiving circuit includes:

2. The power frequency interference resistant receiving circuit according to claim 1, wherein the charge amplifying circuit comprises a first operational amplifier and a second capacitor;

3. The power frequency interference resistant receiving circuit according to claim 1, wherein the voltage amplifying circuit comprises a second operational amplifier, a second resistor and a third resistor;

4. The power frequency interference resistant receiving circuit according to claim 1, wherein the power frequency interference resistant receiving circuit further comprises a filter circuit;

the input end of the filter circuit is connected with the signal output end of the charge amplifying circuit, and the output end of the filter circuit is connected with the input end of the voltage amplifying circuit and used for inhibiting a power frequency signal in the DSSS signal output by the charge amplifying circuit.

5. The power frequency interference resistant receiving circuit according to claim 4, wherein the filter circuit is a second capacitor, a first terminal of the second capacitor is an input terminal of the filter circuit, and a second terminal of the second capacitor is an output terminal of the filter circuit.

6. The utility model provides an anti power frequency interference's receiving circuit, its characterized in that, anti power frequency interference's receiving circuit includes:

the signal input end of the charge amplifying circuit receives a DSSS signal sent by the touch terminal, and the charge amplifying circuit is used for amplifying charges of the DSSS signal and outputting the amplified DSSS signal;

7. A capacitance pen, characterized by comprising the receiving circuit of any one of claims 1-5 for resisting industrial frequency interference; or, include the anti-power frequency interference receiving circuit of claim 6.

8. The stylus according to claim 7, wherein the stylus further comprises a demodulation unit;