CN111813271B

CN111813271B - Capacitance detection circuit, touch chip and electronic equipment

Info

Publication number: CN111813271B
Application number: CN202010955448.4A
Authority: CN
Inventors: 袁广凯; 蒋宏
Original assignee: Shenzhen Goodix Technology Co Ltd
Current assignee: Shenzhen Goodix Technology Co Ltd
Priority date: 2020-09-11
Filing date: 2020-09-11
Publication date: 2021-05-25
Anticipated expiration: 2040-09-11
Also published as: CN111813271A

Abstract

The application provides a capacitance detection circuit, a touch chip and an electronic device, which can reduce the influence of display screen noise on capacitance detection. The capacitance detection circuit includes: the amplifying circuit is connected with a detection capacitor in the touch screen and used for amplifying a capacitance signal of the detection capacitor and converting the capacitance signal into a voltage signal, wherein the voltage signal is used for determining the detection capacitor; and the control circuit is connected with the amplifying circuit and is used for controlling the amplification factor of the amplifying circuit, wherein the period in which one noise peak value of the noise signal of the display screen is positioned comprises N continuous sub-periods, the amplification factor of the amplifying circuit in the N sub-periods is in inverse proportion to the size of the noise signal in the N sub-periods, and N is more than 1.

Description

Capacitance detection circuit, touch chip and electronic equipment

Technical Field

The embodiment of the application relates to the field of capacitance detection, and more particularly to a capacitance detection circuit, a touch chip and an electronic device.

Background

Capacitive sensors are widely used in electronic products to implement touch detection. When a conductor such as a finger touches or approaches a detection electrode in a touch screen of the electronic device, capacitance corresponding to the detection electrode changes, and information that the finger approaches or touches the detection electrode can be acquired by detecting the change amount of the capacitance, so that the operation of a user is judged. However, noise generated from the display screen of the electronic device affects the detection result. Therefore, how to reduce the influence of the display screen noise on the capacitance detection becomes an urgent problem to be solved.

Disclosure of Invention

The embodiment of the application provides a capacitance detection circuit, a touch chip and an electronic device, which can reduce the influence of display screen noise on capacitance detection.

In a first aspect, a capacitance detection circuit is provided, which includes:

the amplifying circuit is connected with a detection capacitor in the touch screen and used for amplifying a capacitance signal of the detection capacitor and converting the capacitance signal into a voltage signal, wherein the voltage signal is used for determining the detection capacitor; and the number of the first and second groups,

the control circuit is connected with the amplifying circuit and used for controlling the amplification factor of the amplifying circuit, wherein the period where one noise peak value of the noise signal of the display screen is located comprises N continuous sub-periods, the amplification factor of the amplifying circuit in the N sub-periods is in inverse proportion to the size of the noise signal in the N sub-periods, and N is larger than 1.

In a possible implementation manner, the amplifying circuit includes an operational amplifier, an adjustable resistor is connected between an input end and an output end of the operational amplifier, and the control circuit is specifically configured to: and controlling the resistance value of the adjustable resistor so that the amplification factor of the amplifying circuit in the N sub-periods is in inverse proportion to the magnitude of the noise signal in the N sub-periods.

In a possible implementation manner, the operational amplifier is a differential operational amplifier, one adjustable resistor is connected between a first input end and a first output end of the differential operational amplifier, and one adjustable resistor is connected between a second input end and a second output end of the differential operational amplifier.

In one possible implementation, the amplification factor of the amplification circuit in a period in which a non-noise peak of the noise signal is located is a constant value.

In one possible implementation, the constant value is greater than or equal to a maximum amplification of the amplification circuit over the N sub-periods.

In one possible implementation, N =3 or N = 4.

In a possible implementation manner, the time period in which the noise peak of the noise signal is located is determined according to the scanning frequency of the line synchronization signal of the display screen.

In a possible implementation, one or two of the noise peaks are included in one scanning period of the line synchronization signal of the display screen.

In one possible implementation, the capacitance detection circuit further includes: and the filter circuit is connected with the amplifying circuit and is used for filtering the voltage signal output by the amplifying circuit.

In one possible implementation, the capacitance detection circuit further includes: and the ADC circuit is connected with the filter circuit and is used for converting the filtered voltage signal into a digital signal.

In a second aspect, a touch chip is provided, including: the capacitance detection circuit in the foregoing first aspect and any possible implementation manner of the first aspect.

In a third aspect, an electronic device is provided, including: a touch screen; a display screen; and a touch chip in any possible implementation manner of the second aspect and the foregoing second aspect.

Based on the technical scheme, the time interval of the noise peak value of the noise signal of the display screen is divided into N continuous sub-time intervals, and the amplification factor of the amplification circuit in the N sub-time intervals is controlled through the control circuit, so that the amplification factor of the amplification circuit in the N sub-time intervals is in inverse proportion to the size of the noise signal in the N sub-time intervals, and the amplification circuit is prevented from being saturated. The capacitance detection circuit improves the signal-to-noise ratio of capacitance detection and has better detection performance while ensuring the effective work of the amplification circuit.

Drawings

Fig. 1 is a schematic diagram of the capacitive detection principle.

FIG. 2 is a schematic block diagram of one possible capacitive sensing system according to an embodiment of the present application.

Fig. 3 is a schematic block diagram of a capacitance detection circuit of an embodiment of the present application.

Fig. 4 is a diagram showing the relationship between the noise level and the amplification factor.

Fig. 5 is a schematic diagram of the relationship between noise magnitude and amplification factor.

Fig. 6 is a schematic diagram of an amplifying circuit according to an embodiment of the present application.

Fig. 7 is a possible specific implementation of the capacitance detection circuit based on fig. 3.

Fig. 8 is a possible specific implementation of the capacitance detection circuit based on fig. 3.

Detailed Description

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

Fig. 1 is a schematic diagram of the principle of touch detection. While two layers of channels in the touch panel are shown in fig. 1, both horizontal and vertical channels are used, a capacitive touch system using such a pattern can typically employ both self-capacitance and mutual capacitance detection methods. During self-capacitance detection, the touch control chip scans the change condition of the self-capacitance of each transverse channel and each longitudinal channel to the ground. When a finger is close to or touching, the self-capacitance of the channel near the finger becomes large. When mutual capacitance detection is performed, one layer of channels is used as a driving channel (TX channel), the other layer of channels is used as a sensing channel (RX channel), and the touch chip detects the change condition of mutual capacitance between TX and RX. Such as the lateral channel C shown in FIG. 1, of a finger and its vicinity_RXN-1Will generate a capacitance Cs, a finger and a longitudinal channel C in the vicinity thereof_TX1A capacitance Cd is generated. Because the human body is a conductor and is connected with the ground, the self capacitance and the mutual capacitance of the channel touched or approached by the finger can be changed, and the touch position of the finger can be calculated by the touch chip according to the detected change of the self capacitance or the mutual capacitance.

FIG. 2 is a schematic block diagram of one possible capacitive sensing system to which the present application relates. As shown in fig. 2, the touch panel 210 is connected to a touch chip (touch IC) 220, wherein the touch IC 220 includes a synchronization control circuit 221, a driving circuit 222, and a capacitance detection circuit 223. The synchronization control circuit 221 is configured to receive a row synchronization signal (Hsync) and a field synchronization signal (Vsync) of the display, and generate a related trigger signal inside the capacitance detection system. The driving circuit 222 is used for generating a driving signal, or a code signal, which can be input to a TX channel of the touch pad. The capacitance detection Circuit 223 may include, for example, a Programmable Gain Amplifier (PGA), an Analog anti-aliasing Filter (AAF) having a low-pass characteristic, an Analog to Digital Conversion Circuit (ADC), and the like. The PGA circuit may be configured to receive a signal transmitted from an RX channel in the touch pad, and amplify the signal; the AAF circuit is connected with the PGA circuit and is used for filtering interference signals carried in the received electric signals; the ADC circuit is connected with the AAF circuit and used for converting the analog signal into a digital signal.

For screens of electronic devices, especially for Y-OCTA screens, since this type of screen differs from a conventional LCD On-cell screen in material, lamination and writing processes, major panel parameters are greatly changed, so that Display noise caused by a Display Driver Integrated Circuit (DDIC) in the screen is significantly increased. The display screen noise affects the capacitance detection circuit in the touch screen, so that the detection sensitivity of the capacitance detection circuit to the self capacitance and the mutual capacitance is obviously reduced.

Therefore, the application provides a capacitance detection circuit which can reduce the influence of display screen noise on capacitance detection of a touch screen.

Fig. 3 is a schematic block diagram of a capacitance detection circuit of an embodiment of the present application. As shown in fig. 3, the capacitance detection circuit 300 includes an amplification circuit 310 and a control circuit 320.

Amplifying circuit 310 and detection capacitor C in touch screen (also called touch screen)_XConnected to detect the capacitance C_XAmplifies the capacitance signal and converts it into a voltage signal. Wherein the voltage signal is used to determine the detection capacitance C_X。

The control circuit 320 is connected to the amplifying circuit 310 for controlling the amplification factor of the amplifying circuit 310. The time period of a noise peak of the noise signal of the display screen includes N consecutive sub-time periods, the amplification factor of the amplifying circuit 310 in the N sub-time periods is inversely proportional to the magnitude of the noise signal in the N sub-time periods, and N > 1.

It should be understood that the display screen and the touch screen described in the embodiments of the present application may be considered as a display layer and a touch layer in a screen of an electronic device, respectively. The screen of the circuit device generally includes a display layer and a touch layer for implementing a display function and a touch function, respectively.

When the display screen is scanned, a scanning signal, such as a line synchronization signal of the display screen, is correlated with a noise signal generated by the display screen. The line synchronization signal is changed according to a certain rule, for example, periodically, and the phase difference between the noise signal of the display screen and the line synchronization signal of the display screen is substantially unchanged, so that the noise signal generated by the display screen is also changed according to a certain rule.

In this embodiment, the noise signal generated by the display screen is divided in time, for example, the period of the noise peak of the noise signal is divided into N sub-periods, i.e., T1, T2, … …, Ti, … … T_N. In the N sub-periods, the noise signal is varied, and therefore, the control circuit may control the amplification factors of the amplification circuit 310 in the N sub-periods respectively according to the magnitude of the noise signal in the N sub-periods. Wherein, the larger the noise signal is, the smaller the amplification factor of the amplifying circuit is; the amplification factor of the amplification circuit is larger in the sub-period in which the noise signal is smaller.

In the capacitance detection, it is possible to determine which periods will generate noise signals based on, for example, transmission of a line synchronization signal of the display screen, so that the amplification factor of the amplification circuit 310 is adjusted according to the corresponding amplification factors set in advance for the different sub-periods.

It should be understood that the time period in which the noise peak is located in the embodiments of the present application refers to a time period between a start time when the noise of the display screen transitions from a low level to a high level and an end time when the noise transitions from the high level to the low level. For example, three noise peaks are shown in fig. 4, where each noise peak includes the period of T1-T6; also for example, fig. 5 shows three noise peaks, wherein the first noise peak and the third noise peak each include a period of time from T1 to T6, and the second noise peak includes a period of time from T8 to T12.

For example, as shown in fig. 4, it is assumed that N =6, a period in which a noise peak of a noise signal generated by a display screen is located is divided into sub-periods T1, T2, T3, T4, T5, and T6. Wherein, in one noise peak, the noise signal generated by the display screen in the sub-period T3 is the largest, and the noise signal generated in the sub-periods T1 and T6 is the smallest. The control circuit 320 controls the amplification factor of the amplification circuit 310 in the sub-periods T1, T2, T3, T4, T5, and T6 to be inversely proportional to the magnitude of the noise signal according to the magnitude of the noise signal generated by the display screen in the sub-periods T1, T2, T3, T4, T5, and T6, that is, the voltage magnitude of the noise signal. As shown in fig. 4, as an example, when the amplification factors of the amplification circuit 310 in the sub-periods T1, T2, T3, T4, T5, and T6 are a1, a2, A3, a4, a5, and A6, respectively, a1= A6 > a2= a5 > a4 > A3 may be controlled.

Fig. 4 shows a case where there is one noise peak in one line synchronization scanning period, in practical applications, there may also be two or more noise peaks in one line synchronization signal scanning period, and the variation of the noise signal in the period of each noise peak may be the same or different. Therefore, the period in which each noise peak is located may be divided into the same or different number N of sub-periods according to the characteristics of each noise peak. For example, a period in which the first noise peak in the scanning period of one row sync signal is included includes N1 sub-periods, and a period in which the second noise peak is included includes N2 sub-periods.

For example, as shown in fig. 5, there are two noise peaks within one line-synchronous scan period. The period in which the previous noise peak is located includes N1 sub-periods, N1=6, T1, T2, T3, T4, T5 and T6, respectively; the period in which the latter noise peak is located includes N2 sub-periods, N2=5, T8, T9, T10, T11 and T12, respectively. Similarly, the control circuit 320 controls the amplification factor of the amplification circuit 310 within the sub-periods T1, T2, T3, T4, T5, and T6 to be inversely proportional to the magnitude of the noise signal; and the control circuit 320 controls the amplification factor of the amplification circuit 310 within the sub-periods T8, T9, T10, T11, and T12 to be inversely proportional to the magnitude of the noise signal. As shown in fig. 5, as an example, when the amplification factors of the amplification circuit 310 in the sub-periods T1, T2, T3, T4, T5, and T6 are a1, a2, A3, a4, a5, and A6, respectively, a1= A6 > a2= a5 > a4 > A3 may be controlled; when the amplification factors A8, a9, a10, a11, and a12 of the amplification circuit 310 within the sub-periods T8, T9, T10, T11, and T12 may be satisfied, A8= a12 > a9 > a11 > a10 may be controlled.

It can be seen that the time period of the noise peak of the noise signal of the display screen is divided into N consecutive sub-time periods, and the control circuit 320 controls the amplification factor of the amplifying circuit 310 in the N sub-time periods, so that the amplification factor of the amplifying circuit 310 in the N sub-time periods is inversely proportional to the magnitude of the noise signal in the N sub-time periods, so as to avoid saturation of the amplifying circuit 310. Thus, the capacitance detection circuit 300 improves the signal-to-noise ratio of capacitance detection and has better detection performance while ensuring the effective work of the amplifying circuit 310.

In the embodiment of the present application, N > 1, so that the capacitance detection circuit 300 has a stronger adaptive ability to noise variation, and can be applied to a case where a plurality of noise peaks exist in a scan period of one line synchronization signal.

Where N is larger, the complexity is more achieved, and where N is smaller, the noise variation cannot be better adapted, so preferably N =3 or N = 4.

The embodiment of the present application does not limit how to determine the magnitude of the noise signal in each of the N sub-periods. For example, the noise level may be determined according to the magnitude of the noise signal at a certain time within the sub-period; also for example, the determination may be based on an average of the noise signals at a plurality of time instances within the sub-period. This is not limited in this application.

The relationship between the magnitude of the noise signal of the N sub-periods and the amplification factor of the amplifying circuit 310 in the N sub-periods may be an ideal reciprocal relationship, for example, in fig. 4, the magnitude of the noise signal of the sub-period T1 and the magnitude of the noise signal of the sub-period T2 may be equal to the ratio between the amplification factor a2 of the amplifying circuit 310 in the sub-period T2 and the amplification factor a1 of the amplifying circuit 310 in the sub-period T1, but the present application is not limited thereto, and in the case where the magnitude of the noise signal of the sub-period T1 is smaller than the magnitude of the noise signal of the sub-period T2, it is sufficient that a1 > a 2.

The amplification factor of the amplification circuit 310 in the period in which the non-noise peak of the noise signal of the display screen is present may be, for example, a constant value. The constant value may be, for example, greater than or equal to the maximum amplification of amplification circuit 310 for the N sub-periods. For example, in the period T7 where the non-noise peak is located in fig. 4 or fig. 5, the amplification factor of the amplification circuit 310 may be equal to the maximum amplification factor of the amplification circuit 310 within N sub-periods, that is, the amplification factors corresponding to the sub-periods T1 and T6 are equal; it may also be larger than the amplification factor of the amplifying circuit 310 in the N sub-periods, i.e., larger than the amplification factors corresponding to the sub-periods T1 and T6. For another example, in the period T13 where the non-noise peak is located in fig. 5, the amplification factor of the amplification circuit 310 may be equal to the maximum amplification factor of the amplification circuit 310 in N2 sub-periods, that is, the amplification factors corresponding to the sub-periods T8 and T12 are equal; it may also be larger than the amplification factor of the amplifying circuit 310 in N2 sub-periods, i.e. larger than the amplification factors corresponding to the sub-periods T8 and T12.

The embodiment of the present application does not set any limit on how to determine the noise peak. The period of the noise peak of the noise signal is determined according to the scanning frequency of the line synchronization signal of the display screen. For example, the phase relationship between the noise peak of the noise signal of the display screen and the line synchronization signal can be obtained by detecting the output signal of the capacitance detection circuit 300, and the magnitude of the noise peak can be further obtained. Thereby determining the amplification factor of the amplification circuit 310 corresponding to N sub-periods within the period of the noise peak.

The amplifier circuit 310 has an input terminal connected to the detection capacitance Cx and outputs a voltage signal associated with the detection capacitance Cx. After the amplification factor of the amplifying circuit 310 is adjusted, the amplified voltage signal may be output based on the amplification factor. Since the voltage signal output from the amplifier circuit 310 changes when the capacitance of the detection capacitance Cx changes, the magnitude or the amount of change of the detection capacitance Cx can be determined based on the magnitude of the voltage signal output from the amplifier circuit 310. That is, the amplification circuit 310 may convert the capacitance signal of the detection capacitance Cx into a voltage signal and amplify it, thereby achieving detection of the detection capacitance Cx.

The control circuit 320 is connected to the amplifying circuit 310 for controlling the amplification factor of the amplifying circuit 310. The amplifying circuit 310 has a relatively large amplification factor in the sub-period of the display screen with small noise, so as to improve the SNR of the capacitive detection; the amplifying circuit 310 has a relatively small amplification factor in the sub-period of the display screen with relatively large noise, so as to avoid saturation of the amplifying circuit 310 and ensure effective operation of the amplifying circuit 310. Therefore, the capacitance detection circuit 300 improves the signal-to-noise ratio of capacitance detection and has better detection performance while ensuring the effective operation of the amplifying circuit 310.

The capacitance detection circuit in the embodiment of the present application may be used for mutual capacitance detection or self-capacitance detection, and the detection capacitance Cx may be a self-capacitance of the TX channel or the RX channel to ground, or the detection capacitance Cx is a mutual capacitance between the TX channel and the RX channel. The TX channel is used to input the driving signal. The RX channel is used to sense the driving signal and generate a detection signal. The following description will be made only by taking mutual capacitance detection as an example.

Optionally, in one implementation, the amplifying circuit 310 includes an operational Amplifier, for example, the amplifying circuit 310 may be a Programmable Gain Amplifier (PGA). The operational amplifier is characterized in that an adjustable resistor, also called a variable resistor, is connected between an input end and an output end of the operational amplifier. Wherein the control circuit 320 is specifically configured to: the resistance of the adjustable resistor is controlled so that the amplification factor of the amplifying circuit 310 in the N sub-periods is inversely proportional to the magnitude of the noise signal in the N sub-periods.

For example, as shown in FIG. 6, the operational amplifier may be a differential operational amplifier that converts the capacitance signal of the detected capacitance Cx into a voltage signal V_OUTThe voltage signal V_OUTThe signal-to-noise ratio is better for differential signals. An adjustable resistor R is connected between the first input end and the first output end of the differential operational amplifier_f1An adjustable resistor R is connected between the second input end and the second output end of the differential operational amplifier_f2. Wherein, preferably, R_f1And R_f2Are equal.

R_f1And R_f2There may be a plurality of steps corresponding to a plurality of resistances, and the resistances are respectively used for matching the noise signals in the N sub-periods. Wherein, in the sub-period with larger noise signal, R_f1And R_f2Will be adjusted to a smaller resistance value so that the amplifying circuit 310 has a smaller amplification factor; and in the sub-period with smaller noise signal, R_f1And R_f2Is adjusted to a larger resistance value so that the amplifying circuit 310 has a larger amplification factor.

In this embodiment, feedback resistors R may be further disposed between the input terminal and the output terminal of the operational amplifier_f1And a feedback resistor R_f2Parallel feedback capacitor C_f1And a feedback capacitor C_f2。

Optionally, the capacitance detection circuit 300 further includes: the filter circuit 340 is connected to the amplifier circuit 310, and is configured to filter the voltage signal output by the amplifier circuit 310.

Optionally, the capacitance detection circuit 300 further includes: the ADC circuit 350 is connected to the filter circuit 340, and is configured to convert the filtered voltage signal into a digital signal.

Fig. 7 shows a possible implementation based on the circuit shown in fig. 3. Fig. 7 shows a driving circuit 330, a mutual capacitance model 360 of the touch screen, and an amplifying circuit 310, a control circuit 320, a filtering circuit 340 and a sampling circuit 350 in a capacitance detection circuit 300. The mutual capacitance model 360 of the touch screen is an equivalent diagram of a touch model in the screen, where Csg is an equivalent capacitance of an RX channel, Cdg is an equivalent capacitance of a driving channel TX, and a detection capacitance Cx is an equivalent capacitance between the RX channel and the TX channel. Rtx is the driving impedance of the driving

circuit

330, and 361 is the noise signal source in the display screen. One end of the detection capacitor Cx is connected to the system ground, and the other end is connected to the amplifying circuit 310. When a finger touches the touch panel, the mutual capacitance between the RX channel and the TX channel at the touch position becomes large, and the capacitance detection circuit 300 can acquire the touch information of the user by detecting the change of the mutual capacitance, that is, the capacitance of Cx.

The driving circuit 330 is used to generate a driving signal, which is input to the TX channel, and generate a sensing signal on the RX channel, which is input to the amplifying circuit 310. The voltage signal V output by the amplifying circuit 310_OUTCan be used to determine the mutual capacitance between the TX channel and the RX channel, i.e., C_XThe size of (2). Filter circuit340 may be, for example, an Analog anti-aliasing Filter (AAF) having a low-pass characteristic to avoid aliasing of high frequency signals or noise into sampling circuit 150. The sampling circuit 350 is, for example, an Analog-to-Digital Converter (ADC) circuit, and is used to convert the voltage signal into a Digital signal for processing by a Digital system. The control circuit 320 may control the position of the adjustable resistor in the amplifying circuit 310 such that the amplification factor of the amplifying circuit 310 has a larger amplification factor in the sub-period with less noise and a smaller amplification factor in the sub-period with more noise. In addition, the control circuit 320 may also control other parts in the capacitance detection circuit 300, such as the cut-off frequency of the filter circuit 340.

It should be understood that the adjustable resistor may be considered as a resistor network including a plurality of resistors having different values, and the control circuit 320 gates each resistor by controlling a switch in series with the resistor. For example, the amplifier circuit 310, feedback resistor R shown in FIG. 8_f1And R_fNAre different. It is understood that the control circuit 320 may control the switches K1 to K by control signals_NTo select the appropriate feedback resistance during the different subintervals to cause the amplification circuit 320 to have an amplification that matches the noise during the subintervals.

The embodiment of the present application further provides a touch chip, which includes the capacitance detection circuit in the various embodiments of the present application.

An embodiment of the present application further provides an electronic device, including: a touch screen; a display screen; and, the touch chip in the various embodiments of the present application described above.

By way of example and not 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, an in-vehicle electronic device, or a wearable smart device, and other electronic devices such as an electronic database, an automobile, and an Automated Teller Machine (ATM). This wearable smart machine includes that the function is complete, the size is big, can not rely on the smart mobile phone to realize complete or partial function, for example: smart watches or smart glasses and the like, and only focus on a certain type of application function, and need to be used in cooperation with other devices such as smart phones, such as various smart bracelets for physical sign monitoring, smart jewelry and other devices.

It should be noted that, without conflict, the embodiments and/or technical features in the embodiments described in the present application may be arbitrarily combined with each other, and the technical solutions obtained after the combination also fall within the protection scope of the present application.

It should be understood that the specific examples in the embodiments of the present application are for the purpose of promoting a better understanding of the embodiments of the present application, and are not intended to limit the scope of the embodiments of the present application, and that various modifications and variations can be made by those skilled in the art based on the above embodiments and fall within the scope of the present application.

The above description is only for the specific embodiments of the present application, but the scope of the present application is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present application, and shall be covered by the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. A capacitance detection circuit for detecting a detected capacitance in a touch screen of an electronic device, the capacitance detection circuit comprising:

the amplifying circuit comprises an operational amplifier, an adjustable resistor is connected between the input end and the output end of the operational amplifier, the input end of the operational amplifier is connected with the detection capacitor in the touch screen, the amplifying circuit is used for amplifying a capacitance signal of the detection capacitor and converting the capacitance signal into a voltage signal, and the voltage signal is used for determining the detection capacitor; and the number of the first and second groups,

the control circuit is connected with the amplifying circuit;

wherein, the time period of the noise signal generated by the display screen of the electronic device includes a time period of a noise peak value and a time period of a non-noise peak value, the time period of a noise peak value of the noise signal includes N consecutive sub-time periods, the control circuit is configured to control the resistance value of the adjustable resistor, so that the amplification factor of the operational amplifier in the N sub-time periods is inversely proportional to the magnitude of the noise signal in the N sub-time periods, so as to avoid saturation of the amplification circuit due to the influence of the noise signal generated by the display screen and improve the SNR of capacitance detection, the amplification factor of the amplification circuit in the time period of the non-noise peak value of the noise signal for amplifying the capacitance signal is a constant value, and the constant value is greater than or equal to the maximum amplification factor of the amplification circuit in the N sub-time periods, and the time period of the noise peak value is determined according to the scanning frequency of the line synchronization signal of the display screen, and N is greater than 1.

2. The capacitance detection circuit of claim 1, wherein the operational amplifier is a differential operational amplifier,

the adjustable resistor is connected between the first input end and the first output end of the differential operational amplifier, and the adjustable resistor is connected between the second input end and the second output end of the differential operational amplifier.

3. A capacitance detection circuit according to claim 1 or 2, wherein N =3 or N = 4.

4. A capacitance detection circuit according to claim 1 or 2, wherein one or both of the noise peaks are included in one scanning cycle of the line synchronisation signal of the display screen.

5. The capacitance detection circuit according to claim 1 or 2, further comprising:

and the filter circuit is connected with the amplifying circuit and is used for filtering the voltage signal output by the amplifying circuit.

6. The capacitance detection circuit of claim 5, further comprising:

and the analog-to-digital conversion ADC circuit is connected with the filter circuit and is used for converting the filtered voltage signal into a digital signal.

7. A touch chip comprising the capacitance detection circuit according to any one of claims 1 to 6.

8. An electronic device, comprising:

a touch screen;

a display screen; and the number of the first and second groups,

the touch chip of claim 7.