WO2022198600A1

WO2022198600A1 - Pressure detection device, active pen chip, and active pen

Info

Publication number: WO2022198600A1
Application number: PCT/CN2021/083103
Authority: WO
Inventors: 谢浩
Original assignee: 深圳市汇顶科技股份有限公司
Priority date: 2021-03-25
Filing date: 2021-03-25
Publication date: 2022-09-29

Abstract

A pressure detection device, an active pen chip, and an active pen. The device comprises: a variable capacitor, which comprises a first plate and a second plate, the first plate being connected to a tip of the active pen and being movable in response to an external pressure received by the tip of the active pen to cause a capacitance value of the variable capacitor to vary in response to the external pressure; a transformer, which comprises a first coil and a second coil, the first coil being connected to the variable capacitor, and the second coil being connected to a control module; and the control module, configured to input an excitation signal to the second coil, and receive an output signal of the second coil to obtain the external pressure. According to the present application, an external pressure on a tip of an active pen is detected by means of the resonant frequency of a resonant circuit, and the sensitivity and detection precision of the pressure detection device are improved.

Description

Pressure detection device, active pen chip and active pen

technical field

The present application relates to the field of touch control, and more particularly, to a pressure detection device, an active pen chip and an active pen.

Background technique

With the development of touch technology, more and more terminals use touch to perform human-computer interaction, and an active pen is a common tool used for human-computer interaction.

The function of the active pen on the touch screen and other terminals to generate different handwriting due to different pressures is realized by the pressure sensor in the active pen. Common pressure sensors include capacitive pressure sensors and resistive pressure sensors. The pressure detection principle of the capacitive pressure sensor is that the change of pressure causes the change of the distance between the two polar plates of the variable capacitor and thus the change of the capacitance. In the application scenario, the active pen can obtain the pressure information of the pen tip by detecting and analyzing the capacitance change. The active pen can send the pressure information of the pen tip to the mobile device, and then the writing effect of different thickness notes can be realized by applying different pressures to the active pen. or application functions.

SUMMARY OF THE INVENTION

Embodiments of the present application provide a pressure detection device, an active pen chip, and an active pen, which can improve the linearity and sensitivity of pressure detection of the active pen.

In a first aspect, a pressure detection device is provided, characterized in that it is used for an active pen, comprising:

a variable capacitor, the variable capacitor includes a first electrode plate and a second electrode plate, the first electrode plate is connected to the tip of the active pen and can be moved in response to external pressure received by the tip of the active pen , so that the capacitance value of the variable capacitor changes in response to the external pressure;

a transformer, the transformer includes a first coil and a second coil, the first coil is connected to the variable capacitor, and the second coil is connected to a control module;

a control module, which is used for inputting an excitation signal to the second coil and receiving an output signal of the second coil to obtain the external pressure.

In the embodiment of the present application, a transformer is introduced into the pressure detection device of the capacitive active pen, which is connected with the variable capacitor of the capacitive active pen to form a resonant circuit, and the external pressure is obtained by detecting the output signal of the resonant circuit. The resonant circuit has a signal amplification effect, The signal close to the resonant frequency will be amplified, and the amplification degree of the signal can reflect the magnitude of the capacitance change, which improves the situation that the external pressure cannot be detected when the pressure on the active pen tip is small and the capacitance change is not obvious, and the pressure detection device is improved. detection sensitivity.

In a possible implementation manner, the receiving the output signal of the second coil to obtain the external pressure includes: demodulating the output signal from the output signal, which is composed of the first coil and the variable capacitor The resonant frequency of the resonant circuit corresponds to the resonant signal to obtain the external pressure. In this embodiment, the external pressure applied to the pen tip of the active pen is detected by detecting the resonant frequency of the resonant circuit, which avoids the inconsistent sensitivity in different pressure ranges caused by the nonlinear relationship between the capacitance and the voltage when the pressure is detected by the capacitance of the variable capacitor. question. Since the resonance frequency of the resonance circuit has an almost linear relationship with the external pressure applied to the tip of the active pen, the linearity and sensitivity of the pressure detection device are effectively improved, and the user experience is improved.

In a possible implementation manner, the receiving the output signal of the second coil to obtain the external pressure includes: demodulating a capacitance signal corresponding to the variable capacitor from the output signal to obtain the external pressure.

In a possible implementation manner, the excitation signal includes multiple segments of periodic signals with different frequencies.

In a possible implementation manner, the control module is connected to the second coil through a single-pole double-throw switch, so as to respectively input the excitation signal and the second coil to the second coil in different connection states of the single-pole double-throw switch The output signal is received.

In the embodiment of the present application, the control module is connected to the second coil of the transformer through a single-pole double-throw switch, and the single-pole double-throw switch is controlled by the control module to be connected to different functional units in the control module in a time-sharing manner. The function of the coil inputting the excitation signal and receiving the output signal from the second coil simplifies the circuit structure of the pressure detection device and improves the working efficiency of the pressure detection device.

In a possible implementation manner, the transformer includes: a first coil, a second coil and a third coil; the second coil and the third coil are connected to a control module, and the control module is used for sending all The second coil inputs excitation signals of multiple frequencies, and demodulates a resonance signal corresponding to the resonance frequency of the resonance circuit from the output signal of the third coil to obtain the external pressure.

In a possible implementation, the device further includes a reference capacitor connected in parallel with the variable capacitor.

In the embodiment of the present application, the capacitance of the reference capacitor is equal to the capacitance of the pressure sensor capacitance when there is no external force, and is connected in parallel with the pressure sensor capacitance, which can be used as a reference value of the capacitance value when there is no external force. By connecting the reference capacitance in parallel with the variable capacitor, The detection error caused by the tolerance of the variable capacitor in the production process can be effectively avoided, and the detection accuracy of the pressure detection device can be improved.

In a possible implementation manner, the control module includes: a signal generator for generating the excitation signal; and a signal demodulator for demodulating the output signal.

In a possible implementation manner, the control module further includes: a filter, the filter is arranged between the second coil and the signal demodulator, and is used for demodulating the output signal before demodulating the output signal. The output signal is filtered.

Before demodulating the resonance signal, the filter in the control module filters out the interference signal, such as environmental noise and electrical noise with a frequency similar to the output signal, which can reduce the interference of the environment on the resonance signal and further improve the active pen pressure detection device. accuracy.

In a possible implementation manner, the control module is configured to: determine through the signal demodulator that the signal with the largest amplitude in the output signal is the resonance signal.

In the embodiment of the present application, the signal demodulator determines the output signal with the largest amplitude as the resonant signal by judging the amplitudes of the output signals of different frequencies, thereby determining the resonant frequency and obtaining the external pressure received by the active pen tip.

In a possible implementation manner, the signal demodulator is a quadrature IQ demodulator, used for:

The signal I1 of the first direction of the output signal and the signal Q1 of the second direction of the output signal are demodulated according to the output signal, wherein,

Wherein, ω is the angular velocity, β is the phase, t is the time, A cos(ωt-β) is the output signal of frequency f, and cosωt and sinωt are the directions sent by the signal generator to the IQ demodulator signal, ω=2πf, A is the amplitude of the output signal, and the first direction is orthogonal to the second direction.

In a possible implementation, the control module is used to:

Determine the amplitude of the output signal according to the following formula,

Wherein, n is the number of cycles of the output signal, and T is the cycle time of the output signal.

In the embodiment of the present application, the signal demodulator performs quadrature IQ demodulation on the output signal, which can demodulate the output signal within a narrow bandwidth range near the output signal bandwidth, avoiding unnecessary interference to some interference signals or noise signals. Demodulation can also filter out some unnecessary signals without a filter, which improves the detection performance and work efficiency of the pressure detection device.

In a possible implementation manner, the circuit of the IQ demodulator includes: a first circuit and a second circuit connected in parallel, and both the first circuit and the second circuit at least include multipliers, Low-pass filters, integrators, and analog-to-digital signal converters.

In a possible implementation manner, the excitation signal is a periodic sine wave or cosine wave signal.

In a second aspect, an active pen chip is provided for detecting the external pressure of the tip of the active pen, wherein the active pen includes a variable capacitor and a transformer; the variable capacitor includes a first electrode plate and a second electrode plate, so The first electrode plate is connected with the pen tip of the active pen and can move in response to the external pressure received by the pen tip of the active pen, so that the capacitance value of the variable capacitor changes in response to the external pressure; The transformer includes a first coil and a second coil, the first coil is connected to the variable capacitor, and the second coil is connected to a control module; the active pen chip includes: a control module for sending the first coil to the first coil. The second coil inputs the excitation signal and receives the output signal of the second coil to obtain the external pressure.

In a possible implementation manner, the receiving the output signal of the second coil to obtain the external pressure includes: demodulating the output signal from the output signal, which is composed of the first coil and the variable capacitor The resonant frequency of the resonant circuit corresponds to the resonant signal to obtain the external pressure.

In a possible implementation manner, the control module is connected to the second coil at a first time for inputting the excitation signal to the second coil, and the control module is connected to the second coil at a second time The second coil is connected for receiving the output signal of the second coil.

In a possible implementation manner, the control module is connected to the second coil and the third coil of the transformer, and is configured to input the excitation signal to the second coil and receive the signal of the third coil. An output signal is coupled to the third coil via the first coil.

In a possible implementation, the control module is configured to input an excitation signal to the second coil, and the excitation signal is configured to be coupled to the first coil of the transformer through the second coil to be used in the second coil. An output signal is generated in a circuit formed by the first coil and the variable capacitor and in parallel with the reference capacitance of the variable capacitor.

In a possible implementation, the control module further includes:

and a filter, which is arranged between the second coil and the signal demodulator, and is used for filtering the output signal before the control module demodulates the output signal.

In a possible implementation manner, the control module is further configured to: determine, by the signal demodulator, the signal with the largest amplitude in the output signal as the resonance signal.

In a possible implementation manner, the signal demodulator is a quadrature IQ demodulator, and the IQ demodulator is connected to the signal generator for:

In a possible implementation manner, the control module is configured to: determine the amplitude of the output signal according to the following formula:

In a possible implementation manner, the circuit of the IQ demodulator includes: a first circuit and a second circuit connected in parallel, and the first circuit and the second circuit include multipliers, low-pass Filters, integrators and analog-to-digital signal converters.

In a third aspect, an active pen is provided, comprising: a casing for accommodating functional components in the active pen, a top end of the casing is provided with an opening; a pen tip disposed inside the casing and passing through all the The opening extends to the outside of the housing, and is used to simulate the external pressure received by the real pen tip; and the pressure detection device according to any possible implementation manner of the first aspect.

In a fourth aspect, an active pen chip is provided for detecting the external pressure of the active pen tip, wherein the active pen includes a variable capacitor and a transformer; the variable capacitor includes a first electrode plate and a second electrode plate, The first electrode plate is connected to the tip of the active pen and can move in response to external pressure received by the tip of the active pen, so that the capacitance value of the variable capacitor changes in response to the external pressure; The transformer includes a first coil and a second coil, the first coil is connected to the variable capacitor, and the second coil is connected to a control module; the active pen chip includes: a control module for sending the The second coil inputs an excitation signal and receives an output signal from the second coil to obtain the external pressure.

In a possible implementation manner, the control module is connected to the second coil and the third coil of the transformer, so that the control module inputs the excitation signal to the second coil and receives the An output signal of a third coil coupled to the third coil via the first coil.

In a possible implementation manner, the control module further includes: a filter, the filter is arranged between the second coil and the signal demodulator, and is used for demodulating the signal in the control module. The output signal is filtered before the output signal.

In a possible implementation manner, the signal demodulator is a quadrature IQ demodulator, and the IQ demodulator is connected to the signal generator for: demodulating the output signal according to the output signal The signal I1 of the first direction of the output signal and the signal Q1 of the second direction of the output signal, wherein,

A fifth aspect provides a method for pressure detection, characterized in that, when applied to an active pen, the method includes:

According to the excitation signal, an output signal is generated based on the resonant circuit. The excitation signal is a periodic wave signal of multiple stages of different frequencies. The output signal is a periodic wave signal corresponding to multiple stages. The resonant circuit includes a variable capacitor and a transformer. coil;

The output signal is demodulated, and a resonance signal corresponding to the resonance frequency of the resonance circuit is demodulated according to the output signal to obtain the external pressure received by the tip of the active pen.

Based on the above solution, the present application detects the external pressure of the active pen tip through the resonant frequency of the resonant circuit by introducing a transformer into the active pen. Since the resonant frequency has an almost linear relationship with the pressure, the sensitivity of pressure detection is almost the same in any pressure range. , which can effectively improve the problem that the external pressure cannot be effectively detected by detecting the capacitance caused by the small change of the capacitance, which improves the sensitivity of the capacitive active pen pressure detection or induction, and improves the working efficiency of the active pen.

Description of drawings

FIG. 1 is a schematic diagram of an external structure of an active pen according to an embodiment of the present application.

FIG. 2 is a schematic diagram of an application scenario of an active pen according to an embodiment of the present application.

FIG. 3 is a schematic diagram of a normalized curve of capacitance and pressure according to an embodiment of the present application.

FIG. 4 is a schematic diagram of a pressure detection device according to an embodiment of the present application.

FIG. 5 is a schematic diagram of another pressure detection device according to an embodiment of the present application.

FIG. 6 is a schematic diagram of a quadrature IQ demodulator according to an embodiment of the present application.

FIG. 7 is a schematic diagram of a normalized curve of resonance frequency and pressure according to an embodiment of the present application.

FIG. 8 is a schematic diagram of an active pen according to an embodiment of the present application.

FIG. 9 is a schematic diagram of an active pen chip according to an embodiment of the present application.

Detailed ways

In order to make the technical problems, technical solutions and beneficial effects to be solved by the embodiments of the present application more clear, the technical solutions of the present application will be described clearly and completely below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present application, but not to limit the present application.

FIG. 1 is a schematic diagram of an external structure of an active pen according to an embodiment of the present application. The active pen 100 includes a pen tip 101 , a pen barrel 102 , a pen clip 103 , and a pen cap 104 . The pen holder 102 is distributed with functional components such as a pen holder 105, a button 106, a light emitting diode (LED) indicator light 107, and the like. In the application scenario of the active pen as shown in FIG. 2 , the active pen 100 can work with a device with a touch screen: the tip electrode of the pen tip 101 of the active pen can send coding signals, and the touch screen is generally distributed with horizontal and vertical Interleaved detection electrodes, the detection electrodes generate corresponding detection signals when triggered by the coding signal of the active pen, and the touch chip in the touch screen can calculate the two-dimensional position coordinates of the active pen according to the detection signals to realize the writing function. The pen tip 101 of the active pen is also connected to a pressure sensor, which can detect the pressure information at the pen tip 101, and the active pen transmits the pressure information to the touch screen through the wireless communication module, so the touch screen can realize the change of the handwriting effect during writing or the change of the handwriting effect according to the different pressure information. perform different functions.

It should be understood that the active pen pressure, the pressure generated by the active pen, and the external pressure received by the active pen tip described in the embodiments of the present application are the pressure output by the user through the active pen, that is, the user's writing pressure. The user can apply pressure to the touch screen through the active pen. According to different pressures, the touch screen can display different notes of the active pen or perform different functions. For example, the pressure of the active pen is related to the thickness of the notes displayed on the screen. Pressure sensor detection in the pen. It should be understood that the pen holder 102 of the active pen may also have a ring electrode, which can also implement the function of the above-mentioned pen tip electrode, which is not limited in this embodiment of the present application.

At present, according to the different pressure sensors used, active pens can be divided into two categories: resistive active pens and capacitive active pens. The tip of a resistive active pen generally uses a special pressure-changing material to detect the pressure by converting it into the resistance of the pressure-changing material. The control module analyzes the detected resistance information to obtain the corresponding pressure information. Capacitive active pens generally use variable capacitors, use the capacitance corresponding to the distance between the plates of the variable capacitors to represent the pressure, and convert the pressure changes into capacitance changes for detection. The control module analyzes the detected capacitance information to obtain the corresponding pressure information. The pressure sensor in the capacitive active pen is directly connected with the control module, and the control module detects the variable capacitance of the pressure sensor to obtain pressure information. 3 is a schematic diagram of a normalized curve between the variable capacitance of the pressure sensor in the capacitive active pen and the pressure of the active pen according to the first embodiment of the present application. Due to the nonlinear relationship between the capacitance and the distance between the electrodes, the relationship between the capacitance and the pressure is also nonlinear. The sensitivity is different within the range. When the pressure is small, the capacitance change is not sensitive, and when the pressure is large, the capacitance change is sensitive, so that the active pen user must apply a large pressure to obtain a better writing experience; on the other hand, when the pressure is small Within the range of the variable capacitor, due to the large distance between the plates of the variable capacitor and the small capacitance of the variable capacitor, in the application scenario where the pressure of the active pen tip is small, there may be cases where the active pen cannot obtain pressure information due to the undetectable capacitance value. situation, which greatly affects the performance and user experience of the active pen.

In view of this, the present application provides a pressure detection device and an active pen, which can overcome the sensitivity problem of the capacitive pressure sensor and effectively improve the linearity and accuracy of pressure detection.

As shown in FIG. 4 , FIG. 4 is a schematic diagram of a pressure detection device according to an embodiment of the present application.

A pressure detection device 400 for an active pen includes:

Variable capacitor 401, the variable capacitor includes a first electrode plate and a second electrode plate, the first electrode plate is connected to the tip of the active pen and moves in response to external pressure received by the tip of the active pen , so that the capacitance value of the variable capacitor 401 changes in response to the external pressure;

The transformer 402 includes a first coil L1 and a second coil L2, the first coil L1 is connected to the variable capacitor 401, and the second coil L2 is connected to the control module 403;

The control module 403 is configured to input the excitation signal to the second coil L2, and receive the output signal of the second coil to obtain the external pressure received by the tip of the active pen.

Optionally, the control module 403 demodulates a resonance signal corresponding to the resonance frequency of the resonance circuit formed by the first coil and the variable capacitor from the output signal to obtain the external pressure.

Specifically, the first coil L1 is connected to the variable capacitor 401 to form a resonance circuit. In the resonant circuit, when the frequency of the external input signal is equal to the resonant frequency of the resonant circuit, the signal will generate resonance and be amplified, that is, the resonant signal, and the frequency of the resonant signal is equal to the resonant frequency of the resonant circuit. The resonant frequency of the resonant circuit is only related to the components that make up the resonant circuit, that is, related to the first coil L1 of the transformer and the variable capacitor 401. Since the intrinsic properties of the transformer coil will not change, when an external force acts on the pressure sensor , the change of the resonant frequency is only related to the variable capacitor 401, and the change of the capacitance of the variable capacitor 401 is related to the pressure detected by the variable capacitor 401. Therefore, the pressure information detected by the pressure sensor can be obtained by demodulating the resonance signal.

In the device 400, the variable capacitor 401 and the first coil L1 of the transformer form a resonant circuit, the control module 403 inputs an excitation signal to the second coil L2 of the transformer, and the excitation signal is coupled to the first coil L1 through the second coil L2 of the transformer , an output signal is generated in the resonant circuit, the output signal is coupled to the second coil L2 through the first coil L1 of the transformer, and the resonant signal is demodulated from the output signal by the control module 403 connected to the second coil.

In the embodiment of the present application, a transformer is introduced into the pressure detection device of the capacitive active pen to form a resonant circuit with the variable capacitor of the capacitive active pen, and the external pressure applied to the tip of the active pen is detected by the resonant frequency of the resonant circuit, thereby avoiding the need to pass When the capacitance of the variable capacitor detects pressure, the non-linear relationship between capacitance and voltage causes the problem of inconsistent sensitivity in different pressure ranges. Since the resonance frequency of the resonance circuit has an almost linear relationship with the external pressure applied to the tip of the active pen, the linearity and sensitivity of the pressure detection device are effectively improved, and the writing experience of the user is improved.

Exemplarily, in the resonant circuit, when no pressure acts on the variable capacitor 401, the capacitance C ₀ of the variable capacitor 401 and the inductance L ₀ of the first coil L1 of the transformer 402 determine the resonant frequency of the resonant circuit to be f ₀ ,

When multiple excitation signals of different frequencies are coupled to the resonant circuit to generate resonance, only the excitation signal with frequency f ₀ is amplified due to the resonance effect of the resonant circuit. Correspondingly, in the output signal coupled to L2 through L1, only The output signal with frequency f ₀ is amplified, and the control module can determine the resonant frequency of the resonant circuit to be f ₀ by receiving and demodulating the returned resonant signal, thereby determining that no pressure acts on the pressure sensor at this time;

When an external force acts on the pressure sensor, the capacitance of the variable capacitor becomes C ₁ , the inductance of the first coil is still L ₀ , and the resonance frequency of the resonant circuit is f ₁ at this time,

Similarly, at this time, only the excitation signal with frequency f ₁ can be amplified by the LC circuit, and only the part of the output signal coupled to L2 with frequency f ₁ is amplified. The control module receives and demodulates the resonant signal to determine this time. The resonant frequency of the resonant circuit is f ₁ , and accordingly, the magnitude of the pressure acting on the pressure sensor can be determined.

Optionally, the control module 403 demodulates the capacitance signal corresponding to the capacitance value of the variable capacitor from the output signal to obtain the external pressure.

Specifically, the output signal coupled from the first coil L1 to the second coil L2 carries a capacitance signal corresponding to the capacitance value of the variable capacitor. Due to the signal amplification effect of the resonant circuit, the control module 403 demodulates the amplified output signal. The output capacitance signal can obtain the external pressure, which can improve the situation that the control module cannot detect the pressure change due to the insensitive capacitance change when the pressure is small.

Optionally, in a possible embodiment, the excitation signal includes a plurality of periodic signals with different frequencies.

Specifically, the frequency range of the excitation signal covers the resonance frequency of the resonance circuit. The control module 403 couples excitation signals of different frequencies to the resonant circuit through the second coil L2, receives the output signal coupled from the first coil L1 through the second coil L2, and demodulates the resonance by analyzing the output signals of multiple frequencies signal to obtain the pressure of the active pen tip.

Optionally, the control module 403 is connected to the second coil L2 through a SPDT switch 406 to respectively input the excitation signal and receive the output signal to the second coil in different connection states of the SPDT switch.

Specifically, in a possible embodiment, when the control module inputs the excitation signal to the second coil L2, as shown in FIG. 4, the SPDT switch 406 is connected to the port S1, and when the control module receives the output signal from the second coil L2 , the SPDT switch 406 is connected to the port S2 , and the connection state of the SPDT switch is controlled by the control module 403 .

In this embodiment, the control module and the second coil of the transformer are connected by a SPDT switch, and the SPDT switch is controlled by the control module to be connected to different functional units in the control module in a time-sharing manner. The function of inputting the excitation signal and receiving the output signal from the second coil simplifies the circuit structure of the pressure detection device and improves the working efficiency of the pressure detection device. FIG. 5 is a schematic diagram of another pressure detection device according to an embodiment of the present application.

Optionally, in a possible embodiment, as shown in FIG. 5 , the pressure detection device further includes a reference capacitor connected in parallel with the variable capacitor.

There are tolerances in the manufacturing process of pressure sensors, and the initial capacitance of the same batch of pressure sensors may be different, that is, the capacitance values of the same batch of pressure sensors when no pressure is applied are different. The capacitance of the reference capacitor is equal to the capacitance of the pressure sensor capacitance when there is no external force, and it is connected in parallel with the pressure sensor capacitance, which can be used as the reference value of the capacitance value when there is no external force. The problem that the measurement accuracy is affected by the manufacturing tolerance of the pressure sensor is improved, and the measurement performance of the pressure detection device is optimized.

In this embodiment, by connecting the reference capacitor 407 in parallel with the variable capacitor 401, the detection error caused by the tolerance of the variable capacitor in the production process can be effectively avoided, and the detection accuracy of the pressure detection device can be improved.

Optionally, as shown in FIG. 4 , the control module 403 includes: a signal generator 404 for generating the excitation signal; and a signal demodulator 405 for demodulating the output signal.

Optionally, the control module 403 is configured to: determine according to the signal demodulator 405 that the signal with the largest amplitude in the output signal is the resonance signal.

Specifically, in a possible implementation manner, the control module determines that the output signal with the largest amplitude is the resonant signal by judging the amplitudes of the output signals of different frequencies, thereby determining the resonant frequency, and obtaining the external pressure accepted by the active pen tip, That is, in the embodiment of the present application, the control module analyzes and determines the resonance signal according to the signal demodulated by the signal demodulator to obtain pressure information.

Optionally, the transformer includes: a first coil, a second coil and a third coil; the second coil and the third coil are connected to a control module, and the control module is used for inputting input to the second coil The excitation signal of multiple frequencies is obtained, and the resonance signal corresponding to the resonance frequency of the resonance circuit is demodulated from the output signal of the third coil to obtain the external pressure.

Specifically, the control module 403 is respectively connected to the second coil and the third coil, wherein the second coil is connected to the signal generator 404, so that the control module 403 can input excitation signals to the second coil; The coil is connected to a signal demodulator 405 so that the control module 403 can receive the output signal from the third coil.

Optionally, the excitation signal is a periodic sine wave or cosine wave.

It should be understood that all periodic signals capable of generating resonance in the resonant circuit can be used as excitation signals, and the embodiments of the present application use sine waves and cosine waves as examples rather than limitations.

Optionally, the signal demodulator 405 is a quadrature IQ demodulator for:

The signal I1 of the first direction of the output signal and the signal Q1 of the second direction of the output signal are demodulated according to the output signal, wherein

Among them, ω is the angular velocity, β is the phase, t is the time, A cos(ωt-β) is the wave signal with frequency f in the resonant signal, cosωt and sinωt are the signal generator to the IQ demodulator For the transmitted direction signal, ω=2πf, A is the amplitude of the wave signal, and the first direction is orthogonal to the second direction.

Specifically, the IQ demodulator is connected to the signal generator, and when the SPDT switch 406 is connected to the port S2, the signal generator can send a direction signal to the IQ demodulator. A multiplier is further included in the IQ demodulator, so that the output signal is multiplied by the direction signal, represented as a signal I1 of a first direction and a signal Q1 of a second direction whose directions are orthogonal, the first direction and the second direction being out of phase 90 degrees. The frequency of the direction signal is the same as the frequency of the output signal.

Optionally, in a possible implementation manner, the control module 403 is configured to:

The amplitude of the wave signal is determined according to the following formula,

Wherein, n is the number of cycles of the wave signal, and T is the cycle time of the wave signal.

Specifically, the processing process and principle of the output signal by the control module are as follows:

First, integrate I1 and Q1 to get I2 and Q2:

Square I2 and Q2 to get I3 and Q3:

The amplitude of the wave signal is obtained by the square root after the addition operation, namely:

Specifically, when the active pen is working, the signal generator 404 in the control module 403 sends out periodic sine waves or cosine waves of different frequencies as excitation signals, and the excitation signals are coupled to the first coil L1 by the second coil L2 of the transformer 402 and pass through the The resonant circuit generates corresponding periodic sine waves or cosine waves of different frequencies as output signals, and the output signals return to the signal demodulator 405 in the control module 403 through the inductive coupling between the coils of the transformer 402 .

In the IQ demodulator, circuit elements such as logic circuits and adders are further included, and the integral operation is performed on the output signals expressed as I1 and Q1.

FIG. 6 is a schematic diagram of an IQ demodulator according to an embodiment of the present application.

Optionally, in a possible implementation manner, the circuit of the IQ demodulator at least includes: a first circuit and a second circuit connected in parallel, and both the first circuit and the second circuit are connected to each other in sequence. multipliers, low-pass filters, integrators, and analog-to-digital signal converters.

Specifically, as shown in FIG. 6 , the IQ demodulator 600 includes at least:

The first circuit and the second circuit are connected in parallel, wherein the first circuit and the second circuit both include: a multiplier 601, a low-pass filter 602, an integrator 603, and an analog-to-digital signal converter 604. The following connections are based on the first circuit As an example,

The multiplier 601 is connected to the S2 port of the SPDT switch to receive the output signal coupled back to the second coil L2 from the transformer 402, and the multiplier 601 is also connected to the signal generator 404 to obtain the direction signal;

The low-pass filter 602 specifically includes: a first resistor, a second resistor, a first amplifier and a first capacitor, the first amplifier has a first input terminal, a second input terminal and an output terminal, the first resistor and the multiplier connected in series with the first input terminal of the first amplifier, the second resistor and the first capacitor are both connected in parallel with the first input terminal and the output terminal of the first amplifier, and the second input terminal of the first amplifier is grounded.

The integrator 603 specifically includes: a third resistor, a second amplifier, a second capacitor and a switch, the second amplifier has a first input end, a second input end and an output end, and one end of the third resistor is connected to the output end of the first amplifier The other end is connected to the first input end of the second amplifier, the third resistor and the second capacitor are connected in parallel with the first input end and the output end of the second amplifier, and the second input end of the first amplifier is grounded.

An analog-to-digital signal converter 604 is connected to the output of the second amplifier for further processing of the output signal.

In the multiplier 601, the output signal is multiplied by the direction signal from the signal generator. Exemplarily, in the first circuit, the output signal is multiplied by the direction signal sinωt to obtain the signal I1 of the first direction, and I1 is subjected to a low pass After the filter 602 filters out some interference signals from the environment, in the integrator 603 , the signal I1 in the first direction of the output signal is integrated to obtain I2 , and the signal I2 is converted into a digital signal in the analog-to-digital signal converter 604 . Similarly, in the second circuit, the output signal and the direction signal cosωt are converted into the digital signal of Q2 through the same process.

The two mutually orthogonal digital signals are converted into I3 and Q3 by a multiplier (not shown in the figure) in the control module 403 , and finally I3 and Q3 are combined and calculated by the control module to form the amplitude A corresponding to the output signal.

In this embodiment, the IQ demodulator is used to perform quadrature demodulation on the output signal, and when the excitation signal is a periodic sine wave or cosine wave, the amplitude of the output signal can be quickly analyzed and calculated to determine the resonance signal , and then use the resonance frequency to detect the external pressure of the active pen tip.

Further, since the IQ demodulator can demodulate the output signal within a narrow bandwidth range near the bandwidth of the output signal, it avoids unnecessary demodulation of some interference signals or noise signals, and can also be used without a filter. Some unnecessary signals are filtered out, which improves the detection performance and work efficiency of the pressure detection device.

Optionally, in a possible implementation manner, the control module further includes: a filter, the filter is arranged between the second coil and the signal demodulator, and is used for demodulating the output The output signal is filtered before the signal.

Before demodulating the resonant signal, the filter in the control module filters out the noise near the frequency range of the resonant signal, such as electrical noise, environmental noise, etc., which can reduce the interference of environmental noise on the resonant signal and further improve the accuracy of pressure detection. sex.

FIG. 7 is a schematic diagram of a normalized curve between the resonance frequency of the pressure sensor in the capacitive active pen and the pressure of the active pen. Figure 7 shows the relationship between the resonance frequency and the pressure of the active pen after the parameters are cured. It can be seen from the figure that the relationship between the resonance frequency and the pressure of the active pen is almost linear. The embodiment of the present application effectively improves the capacitive active pen when the pressure of the active pen is small. When the sensitivity is low or the pressure cannot be detected, the detection performance and detection accuracy of the pressure detection device are improved.

The embodiment of the present application further provides an active pen, as shown in FIG. 8 , which includes the pressure detection device described in the embodiment of the present application.

Illustratively, active pen 800 includes:

A casing 801 is used for accommodating the functional components in the active pen, and the top of the casing is provided with an opening;

A pen tip 802, which is arranged in the housing and extends out of the housing through the opening, for simulating a real pen tip and transmitting pressure;

The variable capacitor 803 includes a first electrode plate and a second electrode plate. The first electrode plate is connected to the pen tip 802 and is used to generate movement in response to the external pressure received by the pen tip of the active pen, so that the capacitance value of the variable capacitor responds to the external pressure. change with pressure

The transformer 805 includes a first coil and a second coil, the first coil is connected to the variable capacitor, and the second coil is connected to the control module;

The control module 806 is configured to input an excitation signal to the second coil and receive an output signal of the second coil to obtain the external pressure.

Specifically, the variable capacitor can be connected in parallel or in series with the first coil through a lead wire to form a resonant circuit; the excitation signal can be a periodical signal with multiple segments of different frequencies.

Optionally, the active pen 800 further includes a reference capacitor 804, the reference capacitor is connected in parallel with the variable capacitor through a lead;

Optionally, the control module 806 includes: a signal generator and a signal demodulator arranged in the control module, respectively used for generating the excitation signal and demodulating the output signal.

Optionally, the control module 806 further includes: a filter disposed between the second coil and the signal demodulator for filtering the output signal before demodulating the output signal.

Optionally, the signal demodulator is an IQ demodulator, and the IQ demodulator includes at least:

The first circuit and the second circuit are connected in parallel, wherein the first circuit and the second circuit both include: a multiplier, a low-pass filter, an integrator, and an analog-to-digital signal converter.

Specifically, taking the first circuit as an example, the multiplier is connected with the SPDT switch to receive the output signal coupled back to the second coil from the transformer, and the multiplier is also connected with the signal generator to obtain the direction signal;

The low-pass filter specifically includes: a first resistor, a second resistor, a first amplifier and a first capacitor, the first amplifier has a first input end, a second input end and an output end, and the first resistor is connected to the multiplier It is connected in series with the first input end of the first amplifier, the second resistor and the first capacitor are both connected in parallel with the first input end and the output end of the first amplifier, and the second input end of the first amplifier is grounded.

The integrator specifically includes: a third resistor, a second amplifier, a second capacitor and a switch, the second amplifier has a first input end, a second input end and an output end, and one end of the third resistor is connected to the output end of the first amplifier , the other end is connected to the first input end of the second amplifier, the third resistor and the second capacitor are connected in parallel with the first input end and the output end of the second amplifier, and the second input end of the first amplifier is grounded.

The analog-to-digital signal converter is connected to the output end of the second amplifier to further process the output signal to obtain the signal I1 in the first direction.

The present application further provides an active pen chip, and FIG. 9 is a schematic diagram of an active pen chip according to an embodiment of the present application.

The active pen chip 900 is used to detect the external pressure of the active pen tip, wherein the active pen includes a variable capacitor and a transformer; the first electrode plate and the second electrode plate of the variable capacitor, the first electrode plate is connected with the tip of the active pen and can respond The movement is generated by the external pressure received by the tip of the active pen, so that the capacitance value of the variable capacitor changes in response to the external pressure; the transformer includes a first coil and a second coil, the first coil is connected with the variable capacitor, and the second coil is connected to the variable capacitor. The coil is connected with the control module of the active pen chip.

The active pen chip 900 includes:

The control module 901 is configured to input an excitation signal to the second coil, and receive an output signal of the second coil to obtain the external pressure.

Optionally, the control module 901 can demodulate a resonance signal corresponding to the resonance frequency of the resonance circuit composed of the first coil and the variable capacitor from the output signal to obtain the external pressure.

The embodiment of the present application detects the external pressure applied to the tip of the active pen by detecting the resonant frequency of the resonant circuit, avoiding the problem of inconsistent sensitivity in different pressure ranges caused by the nonlinear relationship between capacitance and voltage when the pressure is detected by the capacitance of the variable capacitor. . Since the resonance frequency of the resonance circuit has an almost linear relationship with the external pressure applied to the tip of the active pen, the linearity and sensitivity of the pressure detection device are effectively improved, and the user experience is improved.

The active pen chip can implement the functions of the control module in the pressure detection device in any possible implementation manner of the embodiments of the present application, and details are not described herein again.

The embodiment of the present application also provides a method for pressure detection, which is characterized in that, when applied to an active pen, the method includes:

In the embodiment of the present application, a transformer is introduced into the active pen, and the external pressure of the active pen tip is detected by the resonant frequency of the resonant circuit. Since the resonant frequency has an almost linear relationship with the pressure, the sensitivity of the pressure detection in any pressure range is almost the same, which can Effectively improve the problem that the external pressure cannot be effectively detected by detecting the capacitance caused by the small change of the capacitance, the sensitivity of pressure detection or induction of the capacitive active pen is improved, and the working efficiency of the active pen is improved.

In the description of this application, it is to be understood that the terms "center", "length", "thickness", "upper", "lower", "top", "bottom", "inner", "outer", " The orientation or positional relationship indicated by "axial", "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that The device or element must have a specific orientation, be constructed and operate in a specific orientation, and therefore should not be construed as a limitation of the present application. Furthermore, features defined as "first" and "second" may expressly or implicitly include one or more of that feature. In the description of this application, unless stated otherwise, "plurality" means two or more.

In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it may be a fixed connection or a detachable connection Connection, or integral connection; can be mechanical connection, can also be electrical connection; can be directly connected, can also be indirectly connected through an intermediate medium, can be internal communication between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood in specific situations.

The above are only specific embodiments of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art can easily think of various equivalents within the technical scope disclosed in the present application. Modifications or substitutions shall be covered by the protection scope of this application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

A pressure detection device, characterized in that it is used for an active pen, comprising:

a variable capacitor, the variable capacitor includes a first electrode plate and a second electrode plate, the first electrode plate is connected to the tip of the active pen and can be moved in response to external pressure received by the tip of the active pen , so that the capacitance value of the variable capacitor changes in response to the external pressure;

a transformer, the transformer includes a first coil and a second coil, the first coil is connected to the variable capacitor, and the second coil is connected to a control module;

a control module, which is used for inputting an excitation signal to the second coil and receiving an output signal of the second coil to obtain the external pressure.
The device according to claim 1, wherein the receiving the output signal of the second coil to obtain the external pressure comprises: demodulating the output signal from the output signal and the first coil and the The resonant signal corresponding to the resonant frequency of the resonant circuit formed by the variable capacitor is used to obtain the external pressure.
The device according to claim 1, wherein the excitation signal comprises a plurality of periodic signals with different frequencies.
The device according to claim 1, wherein the control module and the second coil are connected through a single-pole double-throw switch, so as to respectively input the information to the second coil in different connection states of the single-pole double-throw switch. the excitation signal and receive the output signal.
The apparatus of claim 1, wherein the transformer comprises;

the first coil, the second coil and the third coil;

The second coil and the third coil are respectively connected to the control module, and the control module is used for inputting the excitation signal to the second coil and demodulating the output signal from the third coil The resonance signal corresponding to the resonance frequency of the resonance circuit is obtained to obtain the external pressure.
The apparatus of claim 1, further comprising a reference capacitance in parallel with the variable capacitor.
The device according to claim 1, wherein the control module comprises:

a signal generator for generating the excitation signal;

a signal demodulator for demodulating the output signal.
The device according to claim 7, wherein the control module further comprises:

and a filter, which is arranged between the second coil and the signal demodulator, and is used for filtering the output signal before the control module demodulates the output signal.
The device according to any one of claims 1 to 8, wherein the control module is used for:

It is determined by the signal demodulator that the signal with the largest amplitude in the output signal is the resonance signal.
The device according to claim 9, wherein the signal demodulator is a quadrature IQ demodulator, and the IQ demodulator is connected to the signal generator for:

The signal I1 of the first direction of the output signal and the signal Q1 of the second direction of the output signal are demodulated according to the output signal, wherein,

Wherein, ω is the angular velocity, β is the phase, t is the time, A cos(ωt-β) is the output signal of frequency f, and cosωt and sinωt are the directions sent by the signal generator to the IQ demodulator signal, ω=2πf, A is the amplitude of the output signal, and the first direction is orthogonal to the second direction.
The device according to claim 10, wherein the control module is used for:

Determine the amplitude of the output signal according to the following formula,

Wherein, n is the number of cycles of the output signal, and T is the cycle time of the output signal.
The apparatus according to claim 10, wherein the circuit of the IQ demodulator comprises:

A first circuit and a second circuit in parallel, the first circuit and the second circuit including a multiplier, a low-pass filter, an integrator and an analog-to-digital signal converter connected to each other in sequence.
The device according to claim 1, wherein the excitation signal is a periodic sine wave or cosine wave signal.
An active pen, characterized in that, comprising:

a casing for accommodating the functional components in the active pen, the top of the casing is provided with an opening;

A pen tip, arranged inside the casing and extending to the outside of the casing through the opening, for simulating a real pen tip and receiving external pressure;

and the pressure detection device according to any one of claims 1 to 13.
An active pen chip, characterized in that it is used to detect the external pressure of the tip of an active pen, wherein the active pen includes a variable capacitor and a transformer; the variable capacitor includes a first pole plate and a second pole plate, and the The first electrode plate is connected with the tip of the active pen and can move in response to external pressure received by the tip of the active pen, so that the capacitance value of the variable capacitor changes in response to the external pressure; the The transformer includes a first coil and a second coil, the first coil is connected to the variable capacitor, and the second coil is connected to a control module;

The active pen chip includes:

The control module is used for inputting an excitation signal to the second coil and receiving the output signal of the second coil to obtain the external pressure.
The chip according to claim 15, wherein the receiving the output signal of the second coil to obtain the external pressure comprises:

A resonance signal corresponding to the resonance frequency of the resonance circuit composed of the first coil and the variable capacitor is demodulated from the output signal to obtain the external pressure.
The chip according to claim 15, wherein the excitation signal comprises a plurality of periodic signals with different frequencies.
The chip according to claim 15, wherein the control module is connected to the second coil at the first time for inputting the excitation signal to the second coil, and the control module is connected to the second coil at the second time. The time is connected to the second coil for receiving the output signal of the second coil.
The chip according to claim 15, wherein the control module is connected to the second coil and the third coil of the transformer, so that the control module inputs the excitation signal to the second coil And receive the output signal of the third coil, the output signal is coupled to the third coil through the first coil.
The chip according to claim 15, wherein the control module is configured to input an excitation signal to the second coil, and the excitation signal is configured to be coupled to the first coil of the transformer via the second coil An output signal is generated in a circuit formed by the first coil and a variable capacitor and a reference capacitance connected in parallel with the variable capacitor.
The chip according to claim 15, wherein the control module comprises:

a signal generator for generating the excitation signal;

a signal demodulator for demodulating the output signal.
The chip according to claim 21, wherein the control module further comprises:

and a filter, which is arranged between the second coil and the signal demodulator, and is used for filtering the output signal before the control module demodulates the output signal.
The chip according to claims 15-22, wherein the control module is further used for:

It is determined by the signal demodulator that the signal with the largest amplitude in the output signal is the resonance signal.
The chip according to claim 23, wherein the signal demodulator is a quadrature IQ demodulator, and the IQ demodulator is connected to the signal generator for:

The signal I1 of the first direction of the output signal and the signal Q1 of the second direction of the output signal are demodulated according to the output signal, wherein,

Wherein, ω is the angular velocity, β is the phase, t is the time, A cos(ωt-β) is the output signal of frequency f, and cosωt and sinωt are the directions sent by the signal generator to the IQ demodulator signal, ω=2πf, A is the amplitude of the output signal, and the first direction is orthogonal to the second direction.
The chip according to claim 24, wherein the control module is used for:

Determine the amplitude of the output signal according to the following formula,

Wherein, n is the number of cycles of the output signal, and T is the cycle time of the output signal.
The chip according to claim 24, wherein the circuit of the IQ demodulator comprises:

A first circuit and a second circuit in parallel, the first circuit and the second circuit including a multiplier, a low-pass filter, an integrator and an analog-to-digital signal converter connected to each other in sequence.
The chip according to claim 15, wherein the excitation signal is a periodic sine wave or cosine wave signal.