WO2022109957A1 - Self-capacitance detection circuit, touch chip, and electronic device - Google Patents

Abstract

The present application provides a self-capacitance detection circuit, a touch chip, and an electronic device, capable of improving an anti-interference capability while improving self-capacitance detection sensitivity. The self-capacitance detection circuit is used for detecting a capacitor to be detected of a detection electrode in a screen. The self-capacitance detection circuit is used for receiving a touch signal inputted by the detection electrode. The self-capacitance detection circuit comprises: an amplifying circuit, the amplifying circuit comprising an operational amplifier and a T-shaped resistor network, a reverse input end of the operational amplifier receiving the touch signal, both ends of the T-shaped resistor network being respectively connected to the reverse input end and an output end of the operational amplifier, and the amplifying circuit being used for outputting a voltage signal according to the touch signal and a cancellation signal; a cancellation circuit for inputting a cancellation signal to the T-shaped resistor network, the cancellation signal being used for cancelling the magnitude of a basic capacitance of said capacitor; and a processing circuit for obtaining a change amount of said capacitor according to the voltage signal.

Description

Self-capacitance detection circuits, touch chips and electronic equipment technical field

The embodiments of the present application relate to the field of capacitance detection, and more particularly, to a self-capacitance detection circuit, a touch control chip, and an electronic device.

Background technique

Capacitive sensors are widely used in electronic products for touch detection. When a conductor such as a finger touches or approaches the detection electrode in the touch screen of the electronic device, the capacitance corresponding to the detection electrode will change. user's actions. However, electronic equipment is subject to display noise and common mode interference noise, which can affect the above detection results. Therefore, how to reduce the influence of noise on self-capacitance detection has become an urgent problem to be solved.

SUMMARY OF THE INVENTION

The embodiments of the present application provide a self-capacitance detection circuit, a touch control chip and an electronic device, which can improve the self-capacitance detection sensitivity and the anti-interference ability at the same time.

In a first aspect, a self-capacitance detection circuit is provided for detecting the capacitance to be measured of a detection electrode in a screen, and the self-capacitance detection circuit is used for receiving a touch signal input by the detection electrode, wherein the detection circuit includes :

an amplifying circuit, the amplifying circuit includes an operational amplifier and a T-shaped resistor network, the inverting input end of the operational amplifier receives the touch signal, and the two ends of the T-shaped resistor network are respectively connected to the inverting input of the operational amplifier terminal and output terminal, the amplifying circuit is used for outputting a voltage signal according to the touch signal and the cancellation signal;

a cancellation circuit for inputting the cancellation signal to the T-shaped resistor network, where the cancellation signal is used to cancel the size of the basic capacitance of the capacitance to be measured; and,

a processing circuit, configured to obtain the change amount of the capacitance to be measured according to the voltage signal;

Wherein, the parameters of the T-type resistor network and the cancellation signal are configured such that the voltage signal output by the amplifying circuit reaches a minimum value under the condition that the capacitance to be measured does not change relative to the basic capacitance , to cancel the base capacitance of the capacitor under test.

Based on the above technical solution, a cancellation signal is input to the T-type resistance network through the cancellation circuit to cancel the basic charge of the capacitor to be measured, so that the small capacitance change caused by touch is amplified and output by the amplifying circuit. The circuit design is simple, Fewer components reduce the noise floor of the components themselves, improve the signal-to-noise ratio and sensitivity of capacitance detection, and have better detection performance.

In a possible implementation manner, the T-type resistor network includes a first resistor, a second resistor and a third resistor, one end of the first resistor is connected to the inverting input end of the operational amplifier, and the first resistor The other end of the resistor is connected to one end of the second resistor and one end of the third resistor, the other end of the second resistor is connected to the cancellation circuit, and the other end of the third resistor is connected to the output end of the operational amplifier.

In a possible implementation manner, the resistance value of the first resistor is equal to the resistance value of the third resistor.

In a possible implementation manner, the amplifying circuit further includes an input resistor, and one end of the input resistor is connected to the inverting input end of the operational amplifier and one end of the first resistor.

In a possible implementation manner, the resistance value of the input resistor is related to the resistance value of the first resistor and the resistance value of the second resistor.

In a possible implementation manner, the resistance value of the input resistor satisfies the following relationship:

Rin=R1+2R2,

Wherein, Rin is the resistance value of the input resistor, R1 is the resistance value of the first resistor, and R2 is the resistance value of the second resistor.

In a possible implementation manner, the self-capacitance detection circuit further includes a drive circuit, the drive circuit includes a drive signal source and a drive resistor, the drive signal source is used to generate a drive signal and output it to the drive through the drive resistor detection electrode.

In a possible implementation manner, one end of the driving signal source is grounded, the other end of the driving signal source is connected to one end of the driving resistor, and the other end of the driving resistor is connected to the other end of the input resistor.

In a possible implementation manner, the resistance value of the driving resistor is:

Rtx2=1/SCx,

Wherein, Rtx2 is the resistance value of the driving resistor, S=j2πf, j is a complex unit, f is the frequency of the driving signal, and Cx is the capacitance value of the capacitor to be measured.

In a possible implementation manner, the resistance value of the input resistor is related to the resistance value of the driving resistor, so that when the screen is touched by a finger compared to when the screen is not touched by a finger, the operational amplifier The maximum output voltage change.

In a possible implementation manner, the resistance value of the input resistor is at least 10 times the resistance value of the driving resistor.

In a possible implementation manner, the cancellation signal is a sine wave signal. By cancelling the sine wave signal, the self-capacitance detection circuit is less affected by the interference frequency, which improves the anti-noise capability of the circuit.

In a possible implementation manner, the self-capacitance detection circuit further includes: a filtering circuit, connected to the amplifying circuit, and configured to perform filtering processing on the voltage signal output by the amplifying circuit.

In a possible implementation manner, the self-capacitance detection circuit further includes: an ADC circuit, connected to the filter circuit, for converting the filtered voltage signal into a digital signal.

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

Based on the above technical solutions, the touch control chip can improve the signal-to-noise ratio of self-capacitance detection, and has better detection performance.

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

Based on the above technical solution, the electronic device improves the signal-to-noise ratio of capacitance detection and has better detection performance.

Description of drawings

FIG. 1 is a schematic diagram of the principle of capacitance detection.

FIG. 2 is a self-capacitance detection circuit of the prior art.

FIG. 3 is another self-capacitance detection circuit in the prior art.

FIG. 4 is a schematic block diagram of a self-capacitance detection circuit according to an embodiment of the present application.

FIG. 5 is a possible specific implementation based on the self-capacitance detection circuit shown in FIG. 4 .

FIG. 6 is a schematic diagram of the connection between the driving circuit and the capacitor to be measured according to the embodiment of the present application.

Detailed ways

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

First, a schematic diagram of a possible application scenario of the capacitance detection circuit of the embodiment of the present application is described with reference to FIG. 1 .

Figure 1 shows the horizontal and vertical two-layer channels in the touch screen. A capacitive touch system using this pattern can usually use both self-capacitance and mutual-capacitance detection methods at the same time. When performing self-capacitance detection, the touch chip will scan the change of the self-capacitance to ground of each horizontal channel and vertical channel. When a finger approaches or touches, the self-capacitance of the channel near the finger becomes larger. For example, as shown in FIG. 1, the finger and its nearby lateral channel C _RXN-1 will generate capacitance Cs, and the finger and its nearby vertical channel C _TX1 will generate capacitance Cd. Since the human body is a conductor and is connected to the ground, the self-capacitance of the channel touched or approached by the finger will change. According to the change of the self-capacitance detected by the touch chip, the change of the self-capacitance can also be called the change of the capacitance to be measured here. The touch information of the finger can be obtained. Here, the horizontal channel in FIG. 1 is referred to as an RX channel, and the vertical channel is referred to as a TX channel, and the horizontal and vertical channels in the touch screen may also be referred to as detection electrodes or sensors.

FIG. 2 shows a self-capacitance detection circuit in the prior art. The self-capacitance detection circuit 200 is used to detect the change of the self-capacitance of the horizontal channel and/or the vertical channel to the ground, that is, the change of the capacitance to be measured of the detection electrode. . The driving signal source Vtx1 sends the driving signal to the detection electrode through the driving resistor Rtx1, and one end of the buffer 201 receives the detection channel and outputs the corresponding detection signal. The detection signal is input to the forward input terminal of the operational amplifier 203. Since the detection signal carries the display noise signal, a circuit is connected to the reverse input terminal of the operational amplifier 203, and the circuit is connected to the forward input terminal of the operational amplifier 203. The circuit is symmetrically arranged to cancel the noise components in the detection signal. The circuit includes a canceling signal source Vcan1, a buffer 202 and a canceling capacitor Cc. The canceling signal source Vcan1 is used to output the canceling signal through the canceling resistor Rc. The buffer 202 One end of the cancellation capacitor Cc and one end of the cancellation resistor Rc are connected, and the operational amplifier 203 outputs the voltage signal V _OUT according to the signals received by the forward input terminal and the reverse input terminal. The output voltage signal V _OUT can be used to determine the variation of the capacitor 210 under test. The capacitor to be measured 210 includes a base capacitance C _X and a capacitance change ΔC _{X relative to the base capacitance C X .} Wherein, when there is no finger touching or approaching, the detected capacitance to be measured is the basic capacitance C _X ; when there is a finger approaching or touching, the detected capacitance to be measured 210 will be at the basic capacitance C _X relative to the basic capacitance C _X Therefore, the detected capacitor 210 to be tested includes the basic capacitance C _X and the capacitance change ΔC _X , wherein the capacitance change ΔC _X actually reflects the user's touch information. Due to the introduction of the buffer, the noise floor of the circuit is high, which reduces the sensitivity of self-capacitance detection. The basic capacitance C _X is often relatively large, which will occupy a limited dynamic range of the circuit, that is, the basic capacitance C _X occupies a large proportion of the dynamic range of the self-capacitance detection circuit, and the capacitance change △C _X when the finger approaches or touches is small, and the modulus is small. The signal value received by a digital conversion circuit (Analog to Digital Conversion Circuit, ADC) is small, thus reducing the sensitivity of self-capacitance detection.

FIG. 3 shows another self-capacitance detection circuit in the prior art. The self-capacitance detection circuit 300 includes a control circuit 310 , a drive circuit 321 , a cancellation circuit 322 , a charge transfer circuit 323 and a processing circuit 330 . The control circuit 310 is used to control the switches K1-K4, so that in the first stage, the canceling circuit 322 charges the canceling capacitor Cc to Vcc and the driving circuit 321 charges the capacitor 210 to be tested to Vcc. In the second stage, the capacitor to be tested is 210 and the cancellation capacitor Cc are shorted to achieve charge cancellation. In the third stage, the charge transfer circuit 323 converts the charge into a voltage signal, so that the voltage signal output by the charge transfer module is 0 when there is no external object touching. In practice, due to the influence of the external environment, it is difficult for the output voltage to reach 0. In the fourth stage, the operational amplifier 3231 is reset. Although this scheme cancels out the size of the basic capacitance Cx in most of the capacitors to be measured 210, and has good sensitivity, but because the switch is continuously controlled to be closed in the detection circuit, the self-capacitance detection circuit is susceptible to a series of harmonic frequencies. Therefore, the self-capacitance detection circuit has poor anti-display noise and anti-common mode interference capabilities.

Therefore, the present application provides a self-capacitance detection circuit, which can improve the self-capacitance detection sensitivity and the anti-interference ability at the same time.

FIG. 4 is a schematic diagram of a self-capacitance detection circuit according to an embodiment of the present application. The self-capacitance detection circuit 400 is used to detect the change of the self-capacitance of the TX channel and/or the RX channel to ground. The self-capacitance detection circuit 400 includes:

Amplifying circuit 401, the amplifying circuit 401 is connected to detection electrodes in a touch screen (also called a touch screen). The amplifying circuit includes an operational amplifier 4011 and a T-type resistor network 4012. The inverting input terminal of the operational amplifier 4011 receives the touch signal, and two ends of the T-type resistor network 4012 are respectively connected to the inverting terminal of the operational amplifier 4011. To the input end and the output end, the amplifying circuit 401 is configured to output a voltage signal according to the touch signal and the cancellation signal.

The cancellation circuit 402 is used for inputting the cancellation signal to the T-type resistor network 4012, where the cancellation signal is used to cancel the size of the basic capacitance of the capacitance to be measured.

The processing circuit 403 is configured to obtain the capacitance change of the capacitor to be measured according to the voltage signal.

Wherein, the parameters of the T-type resistance network and the cancellation signal are configured such that the voltage signal output by the amplifying circuit reaches a minimum value under the condition that the capacitor to be measured does not change relative to the basic capacitance. , to cancel the base capacitance of the capacitor under test.

It should be understood that the touch screen described in the embodiments of the present application may be regarded as a touch layer in a screen of an electronic device. The screen of the circuit device usually includes a display layer and a touch layer, which are respectively used to realize the display function and the touch function. When the voltage signal output by the amplifying circuit reaches the minimum value, it can be understood that the output voltage of the amplifying circuit is the minimum value when there is no finger touch.

Usually, for single-finger touch, the ratio of capacitance change △C _X to the basic capacitance C _X is about 7:10000, and the ratio will be different for different screens, and the basic capacitance C _X will occupy the vast majority of the self-capacitance detection circuit. Part of the dynamic range limits the magnification of the amplifying circuit, thereby affecting the sensitivity of self-capacitance detection. For example, in the prior art, by adding buffers at both ends of the operational amplifier, the mutual interference between the front and rear circuits is reduced, and the anti-display noise and anti-common-mode interference capabilities of the circuit are improved, thereby improving the detection accuracy of the circuit. Complex, buffers add extra noise to the circuit. For example, in the prior art, the self-capacitance detection circuit is increased by adding an offset capacitor, and the offset capacitor is controlled by switching to offset the charge amount of the basic capacitor of the capacitor to be measured, so as to improve the sensitivity of self-capacitance detection. Because of the switch switching, the circuit is susceptible to the interference of a series of harmonic frequency points, which makes the anti-display noise and anti-common mode interference ability are relatively poor.

In the embodiment of the present application, since the T-type resistor network 4012 is used to receive the cancellation signal output by the cancellation circuit 402 to cancel the basic capacitance C _X of the capacitor under test, the voltage signal output by the amplifying circuit 401 and the capacitor under test are relative to the basic capacitance C X . The capacitance change ΔC _X of the capacitor C _X is related, that is, through the voltage signal output by the amplifying circuit 401, the capacitance change ΔC _X of the capacitor to be measured can be determined, thereby increasing the magnification of the amplifying circuit and improving the self-capacitance detection circuit. detection sensitivity. Compared with the prior art, the self-capacitance detection circuit of the present application has a simple design, fewer components and a low noise floor.

FIG. 5 is a possible specific implementation of the self-capacitance detection circuit in FIG. 4 . The self-capacitance detection circuit includes a drive circuit 510, the drive circuit 510 is used to generate a drive signal, the drive signal is input to the TX channel, and an induction signal is generated on the TX channel, the induction signal is input to the amplifier circuit 501, the The sensing signal may be called a touch signal or a detection signal. The voltage signal V _OUT output by the amplifying circuit 501 can be used to determine the capacitance change of the capacitor under test between the TX channel and the system ground. The drive circuit 510 includes a drive signal source Vtx2 and a drive resistor Rtx2, the drive signal source Vtx2 is used to generate a drive signal and output the drive signal to the detection electrode through the drive resistor Rtx2. One end of the drive signal source Vtx2 is grounded, the other end of the drive signal source is connected to one end of the drive resistor Rtx2 , and the other end of the drive resistor Rtx2 is connected to the other end of the input resistor Rin of the operational amplifier 5011 . Among them, the driving signal and the cancellation signal can be AC sine wave signals, so that the circuit is interfered by the frequency points of the sine wave in the band, and the interference frequency points are very few. The self-capacitance detection circuit can better resist display noise and common mode interference. ability.

The amplifier circuit 501 includes a T-type resistor network 5012, the T-type resistor network 5012 includes a first resistor R1, a second resistor R2 and a third resistor R3, one end of the first resistor R1 is connected to the inverting input end of the operational amplifier 5011, the first The other end of the resistor R1 is connected to one end of the second resistor R2 and one end of the third resistor R3, the other end of the second resistor R2 is connected to the cancellation circuit, the cancellation circuit includes a cancellation signal source Vcancel, and the other end of the third resistor R3 Connect to the output of the operational amplifier 5011. The resistance value of the first resistor R1 is equal to the resistance value of the third resistor R3. The T-type resistor network 5012 is used to adjust the amplification gain of the amplifying circuit 501 so as to use a small resistance to achieve a larger amplification factor. At the same time, the T-type resistor network 5012 is also used to receive the cancellation signal from the cancellation signal source Vcancel, the cancellation signal It is used to offset the size of the base capacitance Cx of the capacitor under test 210 .

The amplifying circuit 501 further includes an input resistor Rin, one end of the input resistor Rin is connected to the inverting input end of the operational amplifier 5011 and one end of the first resistor R1, and the resistance value of the input resistor Rin is connected to the first end of the first resistor R1. The resistance value of the resistor R1 and the resistance value of the second resistor R2 are related, so that when the screen is not touched or approached by a finger, the output voltage of the operational amplifier is close to or equal to 0. That is to say, the resistance values of the input resistor Rin, the first resistor R1 and the second resistor R2 in the amplifying circuit 501 are configured such that the capacitance of the capacitor under test 210 does not change relative to the base capacitance C _X , that is, ΔC _X In the case of =0, the voltage signal V _OUT output by the amplifying circuit 401 reaches a minimum value to cancel the basic capacitance C _X of the capacitor under test 210 . In a possible implementation manner, while the resistance value of the input resistor Rin is related to the resistance value of the first resistor R1 and the resistance value of the second resistor R2, the resistance value of the input resistor is also related to the resistance value of the input resistor Rin. The resistance values of the driving resistors are related, so that when the screen is touched by a finger compared to when the screen is not touched by a finger, the output voltage of the operational amplifier changes the most. Wherein, the resistance value of the input resistor is at least 10 times the resistance value of the driving resistor. Ideally, V _OUT can reach 0 in theory; but in practical applications, when V _OUT reaches the minimum value, that is, it is closest to 0, it can be considered that the cancellation circuit 4012 has achieved perfect cancellation, that is, it can cancel most of the basic capacitance C _X . Under the same conditions, for example, when there is no finger touch, find the optimal parameter configuration until the voltage signal V _OUT output by the amplifier circuit 330 reaches the minimum value, so as to cancel the basic capacitance Cx as much as possible. Preferably, the resistance values of the input resistor Rin, the first resistor R1 and the second resistor R2 are configured as: Rin=R1+2R2.

The self-capacitance detection circuit 500 amplifies the difference between the V1 and Vcancel signals. Using the superposition theorem, when Vtx2=0, the excitation signal source of the self-capacitance detection circuit 500 is Vcancel, and the output voltage of the amplifier circuit 5011 is Vcancel. Vout1:

When Vcancel=0, the excitation signal source of the self-capacitance detection circuit 500 is Vtx2, wherein I _R1 and I _R3 represent the current flowing through the resistor R1 and the resistor R3 respectively, V1 is the voltage between the driving resistor and the detection electrode, V2 is the voltage at the junction between resistors R1, R2 and R3. At this time, the output voltage of the self-capacitance detection circuit is Vout2:

Vout2=V2+I _R3 *R3,

Therefore, the voltage value Vout output by the amplifier circuit 501 is:

When the finger does not touch the screen, if Vout=0V or Vout is close to 0V, it means that the cancellation signal source Vcancel of the cancellation circuit perfectly cancels the size of the basic capacitance Cx of the capacitor to be measured 210 .

In the T-type resistance network, generally take the resistance R1 = R3, then there is the following formula:

Let Rin=R1+2R2, when V _cancel =V ₁ , Vout=0V, the size of the cancellation signal source Vcancel perfectly cancels the size of the basic capacitance Cx of the capacitor under test 210 .

When Rin=R1+2R2, R1=R3, the above formula is simplified as follows:

By designing the parameters of the resistor as Rin=R1+2R2, when the voltage signal Vout reaches the minimum value, that is, it is closest to 0, it can be considered that the cancellation circuit 5012 has achieved perfect cancellation, that is, it can cancel most of the basic capacitance C _X . Ideally, when the input resistor Rin, the first resistor R1 and the second resistor R2 of the amplifier circuit 501 are configured to satisfy: Rin=R1+2R2, and when the cancellation signal Vcancel and V1 are configured to have the same amplitude and opposite phase, the cancellation circuit The cancellation efficiency of 402 can reach 100%, that is, the base capacitance Cx is completely cancelled. Among them, the relationship between V1 and the driving signal Vtx2 satisfies:

V1=Vtx2*(1/jwCx)/[Rtx2+(1/jwCx)].

When the finger touches or approaches the screen, the capacitance of the capacitor 210 to be tested will increase by ΔCx, and the capacitance change ΔCx will cause the voltage V1 to change. In order to make the change of ΔCx, V1 has a significant change, take Rin>>Rtx2 and Rin> >R2, when Rtx2=1/(SCx), the voltage signal change ΔV1 generated by V1 is the largest, and the voltage signal change ΔVout corresponding to Vout is also the largest, where S=j2πf, j is a complex unit, and f is the The frequency of the driving signal, and Cx is the capacitance value of the capacitor to be measured. The voltage signal change amount ΔVout is:

When Rtx2=1/(SCx), the voltage signal change amount ΔV1 is the largest, as shown in Figure 6, the derivation process is as follows:

时，即

when

when, that is

At this time, when an external object (such as a finger) touches or approaches the screen, the voltage change of the output of the amplifier circuit is the largest, and the voltage change is the largest.

By configuring the parameters of the driving resistor as Rtx=1/(SCx), the voltage signal amount ΔV1 when V1 changes is the largest, and the voltage signal change amount ΔVout corresponding to Vout is also the largest, so that the capacitance change amount ΔCx is very small. can also be detected, improving the sensitivity of the self-capacitance detection circuit.

It should be understood that, in the embodiments of the present application, the described offsetting of the basic capacitance C _X of the capacitor to be measured includes partially canceling the basic capacitance C _X or completely canceling the basic capacitance C _X . Wherein, when the output voltage V _OUT of the amplifying circuit reaches the minimum value, that is, it is close to 0, it can be considered that the cancellation circuit 4012 has achieved perfect cancellation, that is, it can cancel most of the basic capacitance C _X . In an ideal situation, the cancellation efficiency when Vout=0 is 100%, and the basic capacitance C _X of the capacitor under test 100 is completely cancelled.

By using the self-capacitance detection circuit of the embodiment of the present application, the basic capacitance of the capacitor to be measured can be effectively offset, so that the voltage signal output by the amplifier circuit only reflects the capacitance change of the capacitor to be measured, so that the basic capacitance is occupied in the self-capacitance detection circuit. The ratio of the dynamic range of the sensor is reduced, the amplification factor of the amplifying circuit is increased, the sensitivity of self-capacitance detection is improved, and the detection performance of the self-capacitance detection circuit is improved. Compared with the prior art, the self-capacitance detection circuit of the present application has a simple design, fewer components and a low noise floor.

In a preferred implementation, it is configured that the waveform of the cancellation signal V _Cancel is the same as the waveform of the voltage signal V1, the amplitude of the cancellation signal V _Cancel is the same as the amplitude of the driving signal V1, and the phase of the cancellation signal Vcancel is the same as the phase of the voltage signal V12. The phase difference between V Cancel is within a preset range, eg, the phase difference is within 170° to 180°, in other words, the phase of the cancellation signal V _Cancel is within ±10° of the opposite phase of the voltage signal V1 .

As shown in FIG. 5 , the self-capacitance detection circuit 500 may include, for example, an analog antialiasing filter (Analog Antialiasing Filter, AAF) with low-pass characteristics, an ADC circuit, and the like. Wherein, the AAF circuit is connected with the amplifying circuit for filtering out the interference signal carried in the received electrical signal; the ADC circuit is connected with the AAF circuit for converting the analog signal into a digital signal.

The filter circuit 520 may be, for example, an analog anti-aliasing filter (AAF) with low-pass characteristics, so as to avoid aliasing of high-frequency signals or noise into the sampling circuit 530 . The sampling circuit 530 is, for example, an analog-to-digital converter (Analog-to-Digital Converter, ADC) circuit, which is used to convert the voltage signal into a digital signal so that the digital system can process it.

In the embodiment of the present application, by connecting the T-type resistance network with the cancellation circuit and the amplifier circuit respectively, and designing the resistance values of the resistances R1, R2, R3, the input resistance Rin, and the driving resistance Rtx of the T-type resistance network, the saturation of the amplifier circuit 401 is avoided. . In this way, the self-capacitance detection circuit 500 improves the signal-to-noise ratio of self-capacitance detection while ensuring the effective operation of the amplifying circuit 401, and has better detection performance.

Embodiments of the present application further provide a touch control chip, which includes the self-capacitance detection circuits in the various embodiments of the present application.

The embodiment of the present application further provides an electronic device, the electronic device includes: a touch screen; a display 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 embodiment 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 implementations 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 shall be subject to the protection scope of the claims.

Claims (16)

A self-capacitance detection circuit for detecting a capacitor to be tested of a detection electrode in a screen, the self-capacitance detection circuit for receiving a touch signal input by the detection electrode, wherein the detection circuit comprises: an amplifying circuit, the amplifying circuit includes an operational amplifier and a T-shaped resistor network, the inverting input end of the operational amplifier receives the touch signal, and the two ends of the T-shaped resistor network are respectively connected to the inverting input of the operational amplifier terminal and output terminal, the amplifying circuit is used for outputting a voltage signal according to the touch signal and the cancellation signal; a cancellation circuit for inputting the cancellation signal to the T-type resistance network, where the cancellation signal is used to cancel the size of the basic capacitance of the capacitor under test; and, a processing circuit, configured to obtain the change amount of the capacitance to be measured according to the voltage signal; Wherein, the parameters of the T-type resistor network and the cancellation signal are configured such that the voltage signal output by the amplifying circuit reaches a minimum value under the condition that the capacitance to be measured does not change relative to the basic capacitance , to cancel the base capacitance of the capacitor under test. The self-capacitance detection circuit according to claim 1, wherein the T-shaped resistor network comprises a first resistor, a second resistor and a third resistor, and one end of the first resistor is connected to the inverse of the operational amplifier Input terminal, the other end of the first resistor is connected to one end of the second resistor and one end of the third resistor, the other end of the second resistor is connected to the cancellation circuit, and the other end of the third resistor Connect the output of the operational amplifier. The self-capacitance detection circuit according to claim 2, wherein the resistance value of the first resistor is equal to the resistance value of the third resistor. The self-capacitance detection circuit according to claim 3, wherein the amplifying circuit further comprises an input resistor, and one end of the input resistor is connected to the inverting input end of the operational amplifier and one end of the first resistor. The self-capacitance detection circuit according to claim 4, wherein the resistance value of the input resistor is related to the resistance value of the first resistor and the resistance value of the second resistor. The self-capacitance detection circuit according to claim 5, wherein the resistance value of the input resistor satisfies the following relationship: Rin=R1+2R2, Wherein, Rin is the resistance value of the input resistor, R1 is the resistance value of the first resistor, and R2 is the resistance value of the second resistor. The self-capacitance detection circuit according to any one of claims 4-6, further comprising a driving circuit, the driving circuit comprising a driving signal source and a driving resistor, the driving signal source is used to generate a driving signal and It is output to the detection electrode through the drive resistor. The self-capacitance detection circuit according to claim 7, wherein one end of the drive signal source is grounded, the other end of the drive signal source is connected to one end of the drive resistor, and the other end of the drive resistor is connected to the the other end of the input resistor. The self-capacitance detection circuit according to claim 8, wherein the resistance value of the driving resistor is: Rtx2=1/SCx, Wherein, Rtx2 is the resistance value of the driving resistor, S=j2πf, j is a complex unit, f is the frequency of the driving signal, and Cx is the capacitance value of the capacitor to be measured. The self-capacitance detection circuit according to claim 9, wherein the resistance value of the input resistor is related to the resistance value of the driving resistor, so that the screen is touched by a finger compared with the screen that is not touched by a finger When touched, the output voltage of the operational amplifier varies the most. The self-capacitance detection circuit according to claim 10, wherein the resistance value of the input resistor is at least 10 times the resistance value of the driving resistor. The self-capacitance detection circuit according to claim 1, wherein the cancellation signal is a sine wave signal. The self-capacitance detection circuit according to claim 1, wherein the self-capacitance detection circuit further comprises: A filter circuit, connected to the amplifying circuit, is used for filtering the voltage signal output by the amplifying circuit. The self-capacitance detection circuit according to claim 13, wherein the self-capacitance detection circuit further comprises: An analog-to-digital conversion ADC circuit, connected to the filter circuit, is used for converting the filtered voltage signal into a digital signal. A touch control chip, characterized by comprising the self-capacitance detection circuit according to any one of claims 1 to 14. An electronic device, comprising: touch screen; display screen; and, The touch control chip according to claim 15 .

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