WO2022061832A1

WO2022061832A1 - Touch-control chip, processing method for touch-control detection signal, and electronic device

Info

Publication number: WO2022061832A1
Application number: PCT/CN2020/118171
Authority: WO
Inventors: 沈海明; 包宇洋
Original assignee: 深圳市汇顶科技股份有限公司
Priority date: 2020-09-27
Filing date: 2020-09-27
Publication date: 2022-03-31

Abstract

Provided are a touch-control chip, a processing method for a touch-control detection signal, and an electronic device, which can reduce the impact of the jitter, in a time domain, of a line synchronization signal of a display layer on the touch-control detection of a touch-control layer, and can improve the signal-to-noise ratio of a touch-control detection system. The touch-control chip comprises a driving circuit for outputting a coding signal to a touch-control layer of a screen according to a line scanning cycle of a line synchronization signal of a display layer of the screen; a detection circuit for receiving a detection signal output by the touch-control layer; a sampling circuit for sampling the detection signal to obtain sampling data, wherein the line scanning cycle is variable, and the number of sampling points in different line scanning cycles is a preset value; and a demodulation circuit for performing quadrature demodulation according to the sampling data, so as to obtain a demodulation result of the detection signal.

Description

Touch chip, touch detection signal processing method and electronic device

technical field

The embodiments of the present application relate to the field of information technology, and more particularly, to a touch control chip, a method for processing a touch detection signal, and an electronic device.

Background technique

As the screen of electronic equipment becomes thinner and thinner, the distance between the touch layer and the display layer in the screen is getting closer and closer, and there is mutual influence between the display layer and the touch layer. The control detection signal is synchronized with the line scan period of the line synchronization signal of the display layer, so as to reduce the noise influence of the display layer on the touch layer. However, when the line scanning period of the line synchronization signal of the display layer is unstable, the corresponding touch detection signal collected by the touch chip is also unstable, and the demodulation result obtained after sampling and demodulating the touch detection signal includes additional noise. In this way, the instability of the line synchronization signal of the display layer brings additional noise to the touch detection of the touch layer, reduces the signal-to-noise ratio of the touch detection system, and affects the result of the touch detection.

SUMMARY OF THE INVENTION

Embodiments of the present application provide a touch chip, a method for processing a touch detection signal, and an electronic device, which can reduce the influence of the jitter of the line synchronization signal of the display layer in the time domain on the touch detection of the touch layer, and improve the touch control performance. The signal-to-noise ratio of the detection system.

In a first aspect, a touch control chip is provided, including:

a driving circuit for outputting a coding signal to the touch layer of the screen according to the line scanning period of the line synchronization signal of the display layer of the screen;

a detection circuit for receiving the detection signal output by the touch control layer;

a sampling circuit, configured to sample the detection signal according to the line scan period to obtain sampled data, wherein the line scan period varies, and the number of sampling points in different line scan periods is a preset value; as well as,

and a demodulation circuit, configured to perform quadrature demodulation according to the sampled data to obtain a demodulation result of the detection signal.

Based on the above technical solution, when the line scanning period of the line synchronization signal of the display layer is unstable, since the touch detection signals collected in each line scanning period are sampled according to the same number of sampling points in different line scanning periods, the touch detection signal collected in each line scanning period is sampled. The demodulation result obtained from the sampling data of the control detection signal is also stable, which reduces the influence of the jitter of the line synchronization signal of the display layer in the time domain on the touch detection of the touch layer, and reduces the noise in the detection result. , which improves the signal-to-noise ratio of the touch detection system.

In a possible implementation manner, the sampling circuit is specifically configured to: from the time of the rising edge of the line synchronization signal in the line scanning period, perform the detection on the detection signal in the line scanning period sampling.

In a possible implementation manner, the preset value is an integer less than or equal to F1/F2, where F1 is a sampling frequency used for sampling the detection signal, and F2 is an or the frequency of the detection signal.

In a possible implementation manner, the preset value is the largest integer less than or equal to F1/F2.

In a possible implementation manner, the sampling circuit is specifically configured to: sample the detection signal within a valid time interval of the line scan period, wherein the valid time interval is the detection signal when there is a touch signal The time interval during which the amplitude of the detection signal changes.

Because touch detection, such as capacitance detection of a finger or a pen, usually includes the process of charging and discharging the touch electrodes in the touch layer, the process of canceling the basic capacitance of the touch electrodes, and the touch after canceling the basic capacitance. The process of transferring the amount of charge on the electrode. However, only in the process of charge transfer, the data collected by the sampling circuit reflects the touch condition on the touch electrodes. Therefore, in the line scan period, the sampling circuit can only collect the valid time interval corresponding to the charge transfer process. data, thereby improving the efficiency of data collection.

In a possible implementation manner, the sampling circuit is further configured to: according to the same frequency as the sampling frequency in the effective time interval, in the line scanning period other than the effective time interval, inactive In the time interval, a fixed value is filled as the sampling data in the non-valid time interval.

A fixed value such as 0 can be filled in the non-valid time interval as sampling data, so there is no noise in the non-valid time interval, thereby reducing the proportion of noise in the entire cycle, which is equivalent to eliminating the noise floor in the detection signal.

In a possible implementation manner, the sampling circuit is further configured to: splicing the sampled data obtained in multiple line scanning periods; wherein the demodulation circuit is specifically configured to: according to the spliced sampling data Perform quadrature demodulation, wherein the sampling period of the spliced sampling data is equal to the product of the number of sampling points in each line scanning period and 1/F1, where F1 is used for sampling the detection signal. Sampling frequency.

When processing the sampled data, it is necessary to splicing the data obtained by sampling according to the preset number of sampling points in each cycle.

In a second aspect, a method for processing a touch detection signal is provided, including:

outputting a coding signal to the touch layer of the screen according to the line scan period of the line synchronization signal of the display layer of the screen, and receiving the detection signal output by the touch layer;

According to the line scanning period, the detection signal is sampled to obtain sampled data, wherein the line scanning period varies, and the number of sampling points in different line scanning periods is a preset value;

Perform quadrature demodulation according to the sampled data to obtain a demodulation result of the detection signal.

Based on the above technical solution, since the detection signals collected in each line scanning period are sampled according to the same number of sampling points in different line scanning periods, the demodulation result obtained based on the sampling data of the detection signals in the line scanning period is obtained. That is, it is stable, thereby reducing the noise impact of the jitter of the horizontal synchronization signal of the display layer in the time domain on the touch detection of the touch layer, and improving the signal-to-noise ratio of the touch detection system.

In a possible implementation manner, the sampling of the detection signal includes: starting from the time of the rising edge of the line synchronization signal in the line scan period, sampling all the lines in the line scan period The detection signal is sampled.

In a possible implementation manner, the sampling the detection signal includes: sampling the detection signal within a valid time interval of the line scan period, wherein the valid time interval is a touch The time interval during which the amplitude of the detection signal changes.

In a possible implementation manner, the method further includes: according to the same frequency as the sampling frequency in the valid time interval, in the line scanning period, in the non-valid time interval except the valid time interval In the non-valid time interval, a fixed value is filled as the sampled data in the non-valid time interval.

A fixed value such as 0 can be filled in the non-valid time interval as sampling data, so there is no noise in the non-valid time interval, thereby reducing the proportion of noise in the entire cycle, which is equivalent to reducing the noise floor in the detection signal.

In a possible implementation manner, the method further includes: splicing the sampled data obtained in multiple line scanning periods; wherein the performing orthogonal demodulation according to the sampled data includes: according to the splicing The obtained sampling data is subjected to quadrature demodulation, wherein the sampling period of the spliced sampling data is equal to the product of the number of sampling points in each line scanning period and 1/F1, and F1 is used for the The sampling frequency at which the detection signal is sampled.

In a third aspect, an electronic device is provided, including the touch control chip in the first aspect or any possible implementation manner of the first aspect.

Description of drawings

FIG. 1 is a schematic diagram of a screen module.

FIG. 2 is a schematic diagram of the relationship among the line synchronization signal, pixel data, display layer noise and touch detection signal.

FIG. 3 is a schematic diagram illustrating the influence of the jitter of the horizontal synchronization signal on the touch detection signal.

FIG. 4 is a schematic block diagram of a touch control chip according to an embodiment of the present application.

FIG. 5 is a schematic diagram of sampling timing based on the touch chip shown in FIG. 4 .

FIG. 6 is a schematic diagram of sampled data under ideal conditions.

FIG. 7 is a schematic diagram of sampling data splicing according to an embodiment of the present application.

FIG. 8 is a schematic diagram of a valid time interval of an embodiment of the present application.

FIG. 9 is a schematic diagram of sampling data splicing according to an embodiment of the present application.

FIG. 10 is a schematic diagram of filling sampling data according to an embodiment of the present application.

FIG. 11 is a schematic flowchart of a method for processing a touch detection signal according to an embodiment of the present application.

detailed description

The technical solutions in the present application will be described below with reference to the accompanying drawings.

Nowadays, the screens of electronic devices are designed to be thinner and thinner, in order to reduce the thickness of the electronic device, or to allow more space in the electronic device to accommodate other internal components within the same thickness. Among them, the conversion of the type of the screen from a liquid crystal display (LCD) to an organic light emitting diode (Organic Light Emitting Diode, OLED) display is a typical trend. However, after the OLED screen becomes thinner, the basic capacitance of the touch electrodes in the touch layer of the screen increases, and the noise coupled from the display layer to the touch layer increases, which directly affects the performance and sensitivity of touch detection. .

Figure 1 shows a schematic diagram of the screen module. The touch layer and the display layer in the screen module are usually two independent and separate systems. In theory, there may be no or little interference between them. However, as today's screens are getting thinner and thinner, the touch electrodes in the touch layer are closer to the system ground, so that the self-capacitance of the touch electrodes to the system ground has increased from about 100pF before to about 500pF now. As a result, the interaction between the touch layer and the display layer cannot be ignored.

As shown in Figure 1, the signal generated by the display driver chip is transmitted to the display layer of the screen module, and is coupled to the system ground between the touch layer and the display layer through the parasitic capacitance _CD of the trace, and then passes through the touch layer. The ground capacitances C _sg and C _dg of the touch electrodes are coupled to the touch layer, so that display layer noise is formed on the touch layer, and finally coupled to the touch chip, thereby affecting the performance of touch detection.

The display driving chip generates a line synchronization signal (referred to as Hsync signal) as a clock to update pixel data (or called display data) of pixels in each row of the display layer. Since the basic capacitance of the touch electrodes of the touch layer becomes larger, when the pixel data of each row of pixels is refreshed, the signal input to the display layer will be coupled from the common cathode between the touch layer and the display layer to the touch electrodes of the touch layer. , and ultimately affect touch detection. That is, there is synchronization between the display layer noise coupled from the display layer to the touch layer and the Hsync signal of the display layer.

FIG. 2 shows the relationship among the line synchronization signal, the pixel data, the noise of the display layer, and the touch detection signal (hereinafter also referred to as the detection signal for short). As shown in Figure 2, the display driver chip uses the Hsync signal as the clock to update the pixel data (or display data) of each row of pixels in the display layer, and the display layer noise is generated when the pixel data is refreshed, so the display layer noise is synchronized with the Hsync signal . In order to solve the influence of display layer noise on the touch detection of the touch layer, the touch coding signal (also referred to as coding signal or driving signal) output during touch detection can be synchronized with the Hsync signal, so that the The detection signal is also synchronized with the Hsync signal, that is, a constant phase difference is maintained, thereby reducing the interference of display layer noise on touch detection to a certain extent. For example, as shown in FIG. 2 , the detection signal is acquired during the low noise period in the line scanning period, and the detection signal is synchronized with the Hsync signal. Based on the detection signal, the user's touch information, such as touch position, touch pressure, etc., can be obtained.

It should be understood that the touch coding signal described in the embodiments of the present application refers to the coding signal output by the touch control chip during the touch detection, including the coding signal input to the touch layer; it also includes the output during the touch detection. The control signal used to control other circuits in the touch detection, such as the trigger signal that triggers the sampling circuit to sample the detection signal, etc.

The display driver chip generates the Hsync signal through the internal RC oscillator circuit. Because the clock of the RC oscillator circuit itself has poor precision and large temperature drift, the generated Hsync signal has jitter, which is manifested in that the line scanning period of the Hsync signal may change slightly, so the display layer noise coupled to the touch layer There is also jitter. When an edge of a certain Hsync signal triggers the sampling circuit in the touch chip to collect the detection signal, the jitter of the line scan period will be transferred from one line scan period to the next line scan period in the time domain and superimposed. The longer the continuous sampling time, the greater the jitter of the collected detection signal.

When the noise of the display layer coupled from the display layer to the touch layer becomes larger, the detection signal still needs to have a certain signal-to-noise ratio. Synchronization, thereby eliminating the interference of display layer noise on touch detection to a certain extent.

However, when the line scanning period of the Hsync signal of the display layer is unstable, the detection signal collected by the touch chip is also unstable, and the demodulation result after sampling and demodulating the detection signal is also unstable. The tuning result jitters within a certain range. In this way, the instability of the line scanning period will bring additional noise to the touch detection, which affects the result of the touch detection.

For example, as shown in FIG. 3 , one line synchronization scanning period of the Hsync signal is ideally stable without jitter. Assuming that the line scanning period is stable at 10us under ideal conditions, the jitter value of the line scanning period in practical applications is ±10ns, as shown in the first row of FIG. 3 . The sampling circuit in the touch chip is triggered by the rising edge of a certain Hsync signal, and continuously samples the detection signal of 1ms, as shown in the second row of FIG. 3 . In an ideal situation, the line scanning period is stable, and the sampling circuit samples the detection signal for a total of 100 periods, as shown in the third row of FIG. 3 . However, due to the jitter of the line scanning period in practical applications, the actual sampling period of the sampling circuit is 99.9 to 100.1. The jitter in the time domain is as high as ±10ns×100=±1us in the last line scanning period relative to the sampling trigger time. In this way, for the sampling frequency of 2MHz, the detection signal in the last cycle has an error of 1us/(1/2MHz)=±2 sampling points. Due to the instability of the line scanning period, the detection signal may be under-sampled or the data of two sampling points may be over-sampled, as shown in the fourth row and the fifth row of FIG. 3 respectively.

Usually, in touch detection, the sampling data collected by the sampling circuit is first subjected to quadrature demodulation (also called IQ demodulation or quadrature IQ demodulation) to obtain the demodulation result of the detection signal, and then sent to the The processor performs the calculation of touch coordinates. The last row of FIG. 3 shows the sine signal (Sin signal) used to demodulate the sampled data. Since the cosine signal (Cos signal) and the sine signal are processed in the same way in the embodiment of the present application, the sine signal is used as an example below. describe. In this case, the detection signal has jitter in the time domain but the sinusoidal signal used for quadrature demodulation does not have jitter in the time domain. Therefore, in the process of quadrature demodulation, when the detection signal and the sinusoidal signal sum After the cosine signal is dot-multiplied, the demodulation result is also jittered, which is embodied in the jitter of the signal amplitude obtained by demodulation. For the valid signal in the detection signal, the jitter of the demodulation result is the noise superimposed on the valid signal. In FIG. 3, the noise floor of the circuit system is ignored, and it is assumed that no external object touches the touch electrodes to change the amplitude of the detection signal. When the jitter of the line scanning period is not considered, there is only one demodulation result; when the jitter of the line scanning period is considered, the demodulation result will shake within a certain range. Jitter is noise.

In order to reduce the influence of the Hsync signal of the display layer on the touch detection, the present application proposes a solution for processing the detection signal, which can reduce the influence of the Hsync signal of the display layer on the touch detection result and improve the signal-to-noise ratio of the touch detection system . A detailed description will be given below with reference to FIGS. 4 to 11 .

FIG. 4 is a schematic block diagram of a touch control chip according to an embodiment of the present application. As shown in FIG. 4 , the touch chip 400 includes a driving circuit 410 , a detection circuit 420 , a sampling circuit 430 and a demodulation circuit 440 .

The driving circuit 410 is used for outputting a coding signal to the touch layer of the screen according to the line scanning period of the line synchronization signal of the display layer of the screen.

The detection circuit 420 is configured to receive the detection signal output by the touch layer.

The sampling circuit 430 is configured to sample the detection signal according to the line scanning period to obtain sampled data.

Wherein, the line scanning period varies, but the number of sampling points in different line scanning periods is equal to a preset value.

The demodulation circuit 440 is configured to perform quadrature demodulation according to the sampled data to obtain a demodulation result of the detection signal.

The demodulation result mentioned here, for example, refers to the signal amplitude of the detection signal obtained by demodulating the detection signal.

It should be understood that, during the touch detection period, the driving circuit 410 outputs the coding signal and the detection circuit 420 receives the corresponding detection signal, which may be performed synchronously. Generally, while the driving circuit 410 outputs the coding signal, the detection circuit 420 receives the detection signal output from the touch layer. The detection signal carries the user's touch information, such as the capacitance change of the touch electrode caused by the user's touch. After subsequent processing of the detection signal, the user's touch information can be obtained.

It should also be understood that the line scanning period described here is varied, which means that the line scanning period or the line scanning signal has jitter in the time domain. That is, the output of the line synchronization signal of the display layer is unstable in the time domain, or the line scanning period is unstable in the time domain. For example, ideally, the line scanning period is stable in the time domain, and the length of each line scanning period is 10us; and when the line scanning period is unstable in the time domain, its length is 10us±10ns, and there is a range of 10ns Vibration within.

When the line scanning period changes, the number of sampling points corresponding to the sampled data in different line scanning periods may be the same or different.

It can be seen that when the line scan period of the line synchronization signal of the display layer is unstable, since the touch detection signals collected in each line scan period are sampled according to the same number of sampling points in different line scan periods, the touch detection signal is based on the touch detection signal. The demodulation result obtained from the sampled data is stable, which reduces the influence of the jitter of the line synchronization signal of the display layer in the time domain on the touch detection of the touch layer, reduces the noise in the detection result, and improves the The signal-to-noise ratio of the touch detection system.

In the embodiment of the present application, the number of sampling points in each line scan period is a preset value, and the preset value is, for example, an integer less than or equal to F1/F2, where F1 is the sampling frequency used for sampling the detection signal , F2 is the frequency of the line synchronization signal or the detection signal. Preferably, the preset value is the largest integer less than or equal to F1/F2.

The sampling circuit 430 may be, for example, an ADC circuit, and the sampling circuit 430 acquires data on each sampling point of the detection signal according to a certain sampling frequency based on the sampling clock. As shown in FIG. 5 , when a certain line synchronization signal is triggered, the sampling circuit 430 will perform continuous sampling for a period of time. Based on the foregoing description, it can be known that when the continuous sampling time is long, the jitter of the line scanning period will be transmitted in turn, so that The detection signal in the next few line scanning periods has obvious jitter in the time domain, which causes the result after quadrature demodulation to follow the jitter.

As shown in the trigger signal 0 and the sampling clock 0 in FIG. 5 , based on the sampling clock 0, the detection signal is sampled according to a certain sampling frequency. When there is jitter in the line scanning period, the detection signal in each line scanning period is sampled. The number of sampling points is constantly changing. Since the quadrature demodulated sine signal and cosine signal are generated at a fixed frequency in each sampling length, the jitter of the line scanning period makes the sine signal and cosine signal also jitter relative to the sampled data, so based on the sine signal and cosine The demodulation result obtained after the signal is subjected to quadrature demodulation also follows the jitter. For the valid signal in the detection result, the jitter of the demodulation result is noise.

In the embodiment of the present application, since the touch detection signals collected in each line scanning period are sampled according to the same number of sampling points in different line scanning periods, the demodulation result obtained based on the sampling data of the touch detection signal is It is stable, thereby reducing the influence of the line synchronization signal on the touch detection.

In an implementation manner, the sampling circuit 430 samples the detection signal within the line scanning period from the time of the rising edge of the line synchronization signal within the line scanning period. The line scanning period described in the embodiments of the present application takes the period between the rising edges of the pulses of two adjacent line synchronization signals as a line scanning period as an example, as shown in FIG. From the time of the rising edge of the horizontal synchronization signal in the cycle, the detection signal in the horizontal scanning cycle is sampled. However, it should be understood that when the period between the falling edges of the pulses of two adjacent line synchronization signals is taken as a line scanning period, the time period of the falling edge of the line synchronization signal in the previous line scanning period can be The detection signal in the line scan period is sampled. This embodiment of the present application does not limit how to divide the line scan period, and the sampling circuit 430 starts sampling the detection signal in the line scan period from the start time of the line scan period.

As shown in the trigger signal 1 and the sampling clock 1 in Figure 5, after a certain line scan signal, namely the trigger signal 1, triggers sampling, the detection signal is sampled according to the fixed number of sampling points in each line scan period based on the sampling clock 1 , that is, the number of sampling points in each line scanning period is equal to the preset value. Wherein, the total sampling time does not exceed the duration of a single line scan period, and no sampling is performed if the clock length is less than one sampling point. In FIG. 5, based on the sampling clock 1, sampling starts at the rising edge of the line synchronization signal in each line scan period, and 6 sampling points are sampled in each line scan period according to the sampling frequency until the specified sampling time is reached.

In this way, the data collected by the sampling circuit 430 is stable. Since each sampling period is synchronized with the line scanning period, the jitter of the detection signal caused by the jitter of the line scanning period is eliminated. In addition, since the sampling time in each line scanning period is less than the duration of the line scanning period, the influence of the jitter of the line scanning period on the detection signal is eliminated, and the influence of the jitter of the line scanning period on the touch detection performance is eliminated.

The data obtained based on sampling clock 0 in Figure 5 is the detection signal itself, which can be directly used for subsequent orthogonal demodulation and coordinate calculation; while the data sampled based on sampling clock 1 needs to be further processed before it can be used for subsequent orthogonal solutions. Harmonic Coordinate Calculation.

In an implementation manner, the sampling circuit 430 splices the sampling data obtained in multiple line scanning periods. At this time, the demodulation circuit 440 performs quadrature demodulation according to the spliced sample data.

The sampling period of the spliced sampling data is equal to the product of the number of sampling points in each line scanning period and 1/F1, where F1 is the sampling frequency for sampling the detection signal.

Assume that the frequency of the line scanning signal and the detection signal is F2=300KHz, and the sampling frequency F1=2MHz. For sampling clock 0, the collected signal frequency is also 300KHz. The frequencies of the sine signal and the cosine signal used in the subsequent quadrature demodulation are also 300KHz, as shown in FIG. 6 .

For the data sampled based on the sampling clock 1 in FIG. 5 , the signals collected in multiple line scanning periods need to be spliced end to end to form a new signal, followed by quadrature demodulation and the like.

Theoretically, the number of sampling points in each line scan period is 2MHz/300KHz=6.67. In actual sampling, the number of sampling points in each line scanning period is an integer less than or equal to 6.67, for example, 6 sampling points are selected, as shown in the sampling clock 1 of FIG. 5 . Therefore, after splicing the sampled data in multiple line scanning periods sampled based on the sampling clock 1, the sampling period of the obtained sampled data becomes (1/2MHz)×6=3us, and the corresponding actual frequency is 333.33KHz, The frequencies of the sine and cosine signals used in the subsequent quadrature demodulation also need to be adjusted to the actual frequencies of the signals.

As shown in FIG. 7 , the number of sampling points sampled in each line scan cycle based on the sampling clock 1 is 6, and the data collected in each line scan cycle is spliced to obtain the sampling clock shown by the sampling clock 1 ′ and Sampling data 1 that matches this sampling clock.

For touch detection, such as capacitance detection of a finger or an active pen, it usually includes the process of charging and discharging the touch electrodes in the touch layer, the process of canceling the basic capacitance of the touch electrodes, and the process of canceling the basic capacitance of the touch electrode. The process of transferring the charge on the control electrode. These processes can finally obtain the capacitance change of the touch electrode's capacitance relative to its base capacitance caused by the touch of a finger or an active pen. According to the capacitance change, the touch information of the finger or the active pen can be obtained.

However, only in the process of charge transfer, the data collected by the sampling circuit 430 reflects the touch condition on the touch electrodes. Therefore, in the line scan period, the sampling circuit 430 can only collect valid data corresponding to the charge transfer process. Data within the time interval, thereby improving the efficiency of data collection.

The improvement of the efficiency of data collection mentioned here refers to using as few sampling points as possible to obtain the signal variation on the touch electrodes, saving the sampling power consumption and the sampling time of the line scanning period, on the other hand, it refers to the touch When a signal change amount is generated on the electrode, the corresponding signal change amount on the touch electrode obtained based on the new sampling data formed by splicing the sampling data in the valid time interval is larger.

The valid time interval is a time interval in which the amplitude of the detection signal changes when there is a touch signal. That is to say, when the capacitance of the touch electrode changes due to the touch of the finger or the active pen, the interval in which the amplitude of the detection signal changes correspondingly is the valid time interval. The amplitude change mentioned here may mean that the amount of change in the amplitude is greater than 0 or exceeds a certain threshold. At this time, the sampling circuit 430 may only sample the detection signal within the valid time interval of the line scanning period.

As shown in FIG. 8 , in one line scanning period, time T0 is an effective time interval. Since the amplitude of the detection signal within the valid time interval will change significantly, the sampling circuit 430 samples the detection signal within the time T0. During the other time periods Δt1 and Δt2, the sampling circuit 430 can also sample, but the collected signals only include the circuit noise floor and other interference signals. In theory, after touching the touch electrodes, within Δt1 and Δt2 The amplitude of the detected signal is basically unchanged.

As shown by the trigger signal 2 and the sampling clock 2 in FIG. 5 , the initial delay of the sampling triggered by the horizontal synchronization signal of a certain horizontal scanning period, that is, the trigger signal 2 can be adjusted, so that sampling is only performed within the valid time interval. It can be seen that by adjusting the initial delay of trigger sampling and the number of sampling points, so that only data of a fixed number of sampling points is collected within the valid time interval of the detection signal, the influence of the jitter of the line scanning period on the touch detection can be avoided.

Similarly, when this sampling method is adopted, the sampling circuit 430 can also splicing the sampling data obtained in the valid time interval of multiple line scanning periods. At this time, the demodulation circuit 440 performs quadrature demodulation according to the spliced sample data.

The sampling period of the spliced sampling data is equal to the product of the number of sampling points in each valid time interval and 1/F1, and F1 is the sampling frequency for sampling the detection signal in the valid time interval.

As shown in FIG. 9 , it is assumed that the frequency of the line scanning signal and the detection signal is F2=300KHz, and the sampling frequency F1=2MHz. Based on the number of sampling points sampled by the sampling clock 2 in the valid time interval of each line scanning period is 3, the data collected in the valid time interval of each line scanning period is spliced to obtain the sample clock 2' as shown in The sampling clock and the sampling data 2 corresponding to the sampling clock. Similarly, it can be known that the signal frequency formed by splicing the sampled data in the valid time interval of each line scanning period is 666.67KHz. Likewise, the frequencies of the sine and cosine signals used for quadrature demodulation need to be adjusted accordingly.

For the sampling clock 1 and sampling clock 2 shown in FIG. 5 , the number of sampling points in each line scan period of the sampling clock 2 is reduced, the resulting signal period is shortened, and the effective time interval and the touch electrodes are touched. The amplitude of the detection signal in the effective time interval before and after remains unchanged, which is equivalent to increasing the proportion of the effective signal in the entire period. Therefore, the amplitude of the signal before and after the touch obtained after demodulation changes more.

It can be found that the smaller the number of sampling points in each line scanning period, the greater the difference between the frequency of the finally obtained signal and the frequency of the original detection signal. In order to make the frequency of the finally obtained signal as consistent as possible with the frequency of the actual detection signal, the sampling points can be supplemented in the time period when no data is collected in each line scan period, and the data corresponding to the supplemented sampling points can be set as fixed value, for example set to 0.

For example, for the solution of sampling only within the valid time interval, since the frequency difference between the finally obtained detection result and the actual detection signal is relatively large, in one implementation manner, the sampling circuit 430 may At the same frequency as the sampling frequency of , in each line scan period except the valid time interval in the inactive time interval, fill 0 as the sampling data in the inactive time interval.

As shown in Fig. 10, fill 0 in the non-valid time interval of each line scan period as the sampling data in the non-valid time interval, and based on the data collected by the sampling clock 2 in the valid time interval of each line scan period. By splicing end to end, a sampling clock shown as sampling clock 3' and sampling data 3 conforming to the sampling clock are obtained.

Compared with the sampling data sampled based on sampling clock 1 in Figure 5, the sampling data obtained based on sampling clock 3' in the non-valid time interval is 0, indicating that there is no noise, thereby reducing the proportion of noise in the entire cycle, reducing the noise floor of the detection signal. The sampling data obtained based on the sampling clock 1 in the inactive time represents the noise floor of the system, and may also include interference signals of the display layer and other alien crosstalk signals coupled to the system.

Compared with the data sampled based on the sampling clock 2 in FIG. 5 , after obtaining the sampling data based on the sampling clock 3 ′ and filling the sampling data 0 in the non-valid time interval, the final detection result can be closer to the actual detection signal frequency. .

It should be understood that the examples of this application are filled with 0 as an example, but in practical applications, other values such as 0.01, 1, 50 and other fixed values can also be filled, as long as the purpose of making the noise in the non-valid time interval 0 can be achieved That's it. This is equivalent to giving a DC bias to the entire sampling signal, so that the signal variation on the touch electrodes obtained after quadrature demodulation is finally unchanged, and has no impact on the performance of the entire touch detection system. Taking the filling of 0 in the non-valid time interval as an example is only to facilitate the understanding of the solution of the present application, but as long as the data to be filled is the same, the same purpose can be achieved.

In particular, in the case that the sampling clock of the sampling circuit 430 is synchronized with the clock of the line synchronization signal, and each line scanning period always includes an integer number of sampling points, by filling the unsampled time period with sampling data 0, it is possible to The frequency of the processed detection signal is restored to the frequency of the original detection signal. However, it is difficult for the sampling clock of the touch chip 430 to be specifically synchronized with the display driver chip, so that the main clocks of the two are completely consistent, and it is difficult to include exactly an integer number of sampling points in one line scan period. Only in some special applications, such as the touch display driver integration (Touch Display Driver Integration, TDDI) technology, since the touch chip and the display driver chip are integrated together, the processed The frequency of the detection signal is restored to the frequency of the original detection signal.

Table 1 shows the touch detection results obtained when the detection signal processing method according to the embodiment of the present application is adopted. Assuming that the touch detection time is 500us, the touch detection is self-capacitance detection. As shown in Table 1, when the solution of the present application is not adopted, the signal-to-noise ratio (SNR) of the detection results are 7.69, 4.2 and 2.82 respectively when the test images are low-noise, medium-noise and high-noise respectively; In the solution of the present application, when the test images are low-noise, medium-noise and high-noise respectively, the signal-to-noise ratios of the detection results are 9.84, 5.92 and 4.83 respectively. Therefore, using the solutions of the embodiments of the present application, the performance of touch detection can be improved to 1.28, 1.41, and 1.71 times the original in low-noise, medium-noise, and high-noise scenarios, respectively.

Table I

It can be seen from Table 1 that the signal processing method of the present application can effectively reduce the influence of the jitter of the line scanning period on the detection result, and improve the signal-to-noise ratio of the touch detection system. Among them, for the screen of the electronic device tested in Table 1, the larger the display layer noise is, the more serious the jitter of the line scanning period is, and the signal-to-noise ratio of the touch detection system is improved by using the signal processing method of the present application. The more obvious, can improve 28-71%.

Table 2 shows the influence of the number of sampling points on the result of touch detection. It is assumed that the test picture is a high-noise picture, the touch detection is self-capacitance detection, and the sampling clock is set in the valid time interval, that is, the time period during which the amplitude of the detection signal changes before and after the touch. It can be seen from Table 2 that the less the number of sampling points in each line scan period, the closer the sampling position is to the moment when the signal amplitude changes the most, the greater the change in the voltage of the detection signal obtained before and after the touch electrode is touched. However, the smaller the number of sampling points, the closer the sampling position is to the moment when the signal amplitude changes the most, and the larger the noise signal. For example, in Table 2, when the number of sampling points is 6, the signal-to-noise ratio is the highest, which is 4.83. Therefore, when determining the effective time interval T0 and the number of sampling points shown in Figure 8, it is necessary to conduct an actual test, and scan the relationship between the signal-to-noise ratio and the number of sampling points and the sampling position Δt1 to find the best configuration.

Table II

It can be seen that the present application eliminates or weakens the influence of the jitter of the line scanning period on the detection result from the perspective of signal sampling. The line scanning period jitter causes the line scanning period later in the sampling time to have obvious left and right jitter in the time domain, which causes the signal amplitude of the back-end digital demodulation to change. The amplitude of this change is noise for the effective signal. That is, the jitter of the line scan period will bring additional noise to the touch detection. However, using the solution of the present application eliminates or weakens the extra noise caused by the jitter of the line scanning period to the touch detection system.

The present application also provides a method for processing a touch detection signal. As shown in FIG. 11 , the method 1100 may be performed by the above-mentioned touch control chip 600 . The method 1100 includes some or all of the following steps.

In step 1110, according to the line scanning period of the line synchronization signal of the display layer of the screen, a coding signal is output to the touch layer of the screen, and a detection signal output by the touch layer is received.

In step 1120, the detection signal is sampled according to the line scan period to obtain sample data, wherein the line scan period is variable, and the number of sampling points in different line scan periods is a preset value.

In step 1130, quadrature demodulation is performed according to the sampled data to obtain a demodulation result of the detection signal.

Optionally, in an implementation manner, the sampling the detection signal includes: starting from the time of the rising edge of the line synchronization signal in the line scanning period, sampling the detection signal within the line scanning period The detection signal is sampled.

Optionally, in an implementation manner, the preset value is an integer less than or equal to F1/F2, where F1 is the sampling frequency for sampling the detection signal, and F2 is the line scan signal. or the frequency of the detection signal.

Optionally, in an implementation manner, the preset value is the largest integer less than or equal to F1/F2.

Optionally, in an implementation manner, the sampling the detection signal includes: sampling the detection signal within a valid time interval of the line scan period, wherein the valid time interval is The time interval during which the amplitude of the detection signal changes when there is a touch signal.

Optionally, in an implementation manner, the method further includes: according to the same frequency as the sampling frequency in the valid time interval, in each line scanning period except the valid time interval In the non-valid time interval, a fixed value is filled as the sampled data in the non-valid time interval.

Optionally, in an implementation manner, the method further includes: splicing the sampled data obtained in multiple line scanning periods; wherein the performing orthogonal demodulation according to the sampled data includes: Perform quadrature demodulation according to the spliced sampling data, wherein the sampling period of the spliced sampling data is equal to the product of the number of sampling points in each line scanning period and 1/F1, and F1 is the The sampling frequency for sampling the detection signal.

It should be understood that, for the specific description of the method 1100 , reference may be made to the foregoing related description of the touch control chip 600 , which is not repeated here for brevity.

The embodiment of the present application further provides an electronic device, the electronic device includes: a screen; and the touch chip in the above-mentioned various embodiments of the present application.

As an example and not a limitation, the electronic device in the embodiments of the present application may be a portable or mobile computing device such as a terminal device, a mobile phone, a tablet computer, a notebook computer, a desktop computer, a game device, a vehicle-mounted electronic device, or a wearable smart device, and Electronic databases, automobiles, bank ATMs (Automated Teller Machine, ATM) and other electronic devices. The wearable smart device includes full functions, large size, and can realize complete or partial functions without relying on smart phones, such as smart watches or smart glasses, etc., and only focus on a certain type of application function, which needs to cooperate with other devices such as smart phones. Use, such as various types of smart bracelets, smart jewelry and other equipment for physical monitoring.

It should be noted that, on the premise of no conflict, each embodiment described in this application and/or the technical features in each embodiment can be arbitrarily combined with each other, and the technical solution obtained after the combination should also fall within the protection scope of this application .

It should be understood that the specific examples in the embodiments of the present application are only to help those skilled in the art to better understand the embodiments of the present application, rather than limiting the scope of the embodiments of the present application, and those skilled in the art can Various improvements and modifications can be made, and these improvements or modifications all fall within the protection scope of the present application.

The above are only specific embodiments of the present application, but the protection scope of the present application is not limited to this. should be covered within the scope of protection of this application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

A touch chip, characterized in that it includes:

a driving circuit for outputting a coding signal to the touch layer of the screen according to the line scanning period of the line synchronization signal of the display layer of the screen;

a detection circuit for receiving the detection signal output by the touch control layer;

a sampling circuit, configured to sample the detection signal according to the line scan period to obtain sampled data, wherein the line scan period varies, and the number of sampling points in different line scan periods is a preset value; as well as,

and a demodulation circuit, configured to perform quadrature demodulation according to the sampled data to obtain a demodulation result of the detection signal.
The touch control chip according to claim 1, wherein the sampling circuit is specifically used for:

The detection signal within the line scanning period is sampled from the time of the rising edge of the line synchronization signal within the line scanning period.
The touch control chip according to claim 1 or 2, wherein the preset value is an integer less than or equal to F1/F2, wherein F1 is a sampling frequency for sampling the detection signal, and F2 is the frequency of the line scan signal or the detection signal.
The touch control chip according to claim 3, wherein the preset value is a maximum integer less than or equal to F1/F2.
The touch control chip according to any one of claims 1 to 4, wherein the sampling circuit is specifically used for:

The detection signal is sampled in the valid time interval of the line scanning period, wherein the valid time interval is a time interval in which the amplitude of the detection signal changes when there is a touch signal.
The touch control chip according to claim 5, wherein the sampling circuit is further used for:

Fill in the non-valid time interval other than the valid time interval in the line scanning period with the same frequency as the sampling frequency in the valid time interval as the sampling in the inactive time interval data.
The touch control chip according to any one of claims 1 to 6, wherein the sampling circuit is further used for:

splicing the sampled data obtained in multiple line scan periods;

Wherein, the demodulation circuit is specifically used for:

Perform quadrature demodulation according to the spliced sampling data, wherein the sampling period of the spliced sampling data is equal to the product of the number of sampling points in each line scanning period and 1/F1, where F1 is used for The sampling frequency at which the detection signal is sampled.
A method for processing a touch detection signal, comprising:

outputting a coding signal to the touch layer of the screen according to the line scan period of the line synchronization signal of the display layer of the screen, and receiving the detection signal output by the touch layer;

According to the line scanning period, the detection signal is sampled to obtain sampled data, wherein the line scanning period varies, and the number of sampling points in different line scanning periods is a preset value;

Perform quadrature demodulation according to the sampled data to obtain a demodulation result of the detection signal.
The method according to claim 8, wherein the sampling the detection signal comprises:

The detection signal within the line scanning period is sampled from the time of the rising edge of the line synchronization signal within the line scanning period.
The method according to claim 8 or 9, wherein the preset value is an integer less than or equal to F1/F2, wherein F1 is a sampling frequency for sampling the detection signal, and F2 is the The frequency of the scanning signal or the detection signal.
The method according to claim 10, wherein the preset value is the largest integer less than or equal to F1/F2.
The method according to any one of claims 8 to 11, wherein the sampling the detection signal comprises:

Sampling the detection signal in the valid time interval of the line scanning period, wherein the valid time interval is a time interval in which the amplitude of the detection signal changes when there is a touch signal.
The method of claim 12, wherein the method further comprises:

Fill in the non-valid time interval other than the valid time interval in the line scanning period with the same frequency as the sampling frequency in the valid time interval as the sampling in the inactive time interval data.
The method according to any one of claims 8 to 13, wherein the method further comprises:

splicing the sampled data obtained in multiple line scan periods;

Wherein, performing quadrature demodulation according to the sampled data includes:

Perform quadrature demodulation according to the spliced sampling data, wherein the sampling period of the spliced sampling data is equal to the product of the number of sampling points in each line scanning period and 1/F1, where F1 is used for The sampling frequency at which the detection signal is sampled.
An electronic device, comprising the touch control chip according to any one of claims 1 to 7.