Capacitive touch detection device

Abstract

The application relates to a capacitive touch detection device, which comprises a capacitive touch device and a touch detection chip connected with the capacitive touch device; the touch detection chip comprises a capacitance detection module and a calculation unit connected with the capacitance detection module; the capacitive touch device is configured to convert a touch action into a signal of capacitance change and send the signal to the touch detection chip; the touch detection chip is configured to perceive the capacitance change amount of the capacitive touch device through the capacitance detection module, and then obtain a final capacitance value through the calculation unit. The application discharges self-capacitance twice through two resistors, the discharge resistors of the two times of discharge are different, thereby two different discharge curves are obtained, and the relative value of the ground sub-capacitance is obtained through the difference of the two discharge curves. The scheme of the two resistors is simple in structure and simple in control timing; through the difference between the front and rear discharge curves, low-frequency noise (such as flicker noise) can be effectively inhibited.

Description

Technical Field

[0001] This invention relates to the field of capacitive touch, and more particularly to a capacitive touch detection device. Background Technology

[0002] Currently, capacitive touch devices need to overcome significant common-mode interference, leading to a reduced signal-to-noise ratio. This is especially true after the widespread adoption of flexible displays, where resolving common-mode interference caused by the display beneath the touch layer has become a major challenge for the touch industry. Therefore, how to reduce common-mode interference in touch devices while preserving and amplifying the useful signal is a key issue that needs to be addressed at this stage. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a capacitive touch detection device that solves the deficiencies of the prior art.

[0004] The objective of this invention is achieved through the following technical solution: a capacitive touch detection device, comprising a capacitive touch device and a touch detection chip connected thereto; the touch detection chip comprises a capacitance detection module and a computing unit connected thereto; The capacitive touch device is configured to convert touch actions into signals of capacitance changes and send them to the touch detection chip. The touch detection chip is configured to sense the capacitance change of the capacitive touch device through the capacitance detection module, and then obtain the final capacitance value through the calculation unit.

[0005] The capacitive touch device includes multiple conductive patterns, which are connected to a capacitance detection module via wires. Each conductive pattern consists of a series of repeating patterns with a point-to-ground area connected together. Each repeating pattern forms a small capacitor to ground, and all the small capacitors are connected in parallel to form a self-capacitance to ground.

[0006] The capacitance detection module includes a switch array and a detection unit connected thereto; each conductive pattern is connected to a switch in the switch array via a wire, and by controlling the conduction state of each switch, the corresponding conductive pattern is connected to the detection unit for detection of self-capacitance to ground.

[0007] The detection unit includes an analog-to-digital converter, switches K1, K2 and K3, a main discharge resistor R1 and a secondary discharge resistor R2; the signal selected from the switch array is connected to the analog-to-digital converter, switch K3 and switch K1 respectively; the other end of switch K3 is connected to the VDD voltage terminal, switch K1 is connected to the main discharge resistor R1 and switch K2 respectively, and switch K2 is connected to the secondary discharge resistor R2.

[0008] The working process of the detection unit includes: Turning on switch K3 and turning off switches K1 and K2 raises the voltage at the input port of the analog-to-digital converter to VDD voltage. When switch K3 is turned off, switch K1 is turned on, and switch K2 remains off, the self-capacitance to ground discharges to the main discharge resistor R1. This process is the main discharge process. The analog-to-digital converter records the voltage value. When the charge on the self-capacitor to ground is discharged by the main discharge resistor R1, switch K1 is turned off and switch K3 is turned on again, raising the voltage at the input port of the analog-to-digital converter back to VDD voltage. When switch K3 is turned off and switches K1 and K2 are turned on, the self-capacitance to ground discharges to the main discharge resistor R1 and the auxiliary discharge resistor R2. This process is the auxiliary discharge process, and the analog-to-digital conversion unit records the voltage value.

[0009] The calculation unit performs a subtraction operation on the ADC curves of the main discharge process and the auxiliary discharge process in the digital domain, and integrates the difference in the time domain, specifically including: Align the ADC sample values ​​of the main discharge process and the auxiliary discharge process to the same starting point; At each moment, the ADC sampled values ​​of the discharge process and the auxiliary discharge process are subtracted one by one and stored; Integrate the differences one by one to obtain a summation value, which is the relative capacitance value of this sample.

[0010] During the sampling process, a bias voltage is superimposed on the sampled value of the analog-to-digital conversion unit. This bias voltage is superimposed on both the main discharge process and the auxiliary discharge process curves. When the two discharge curves are subtracted, they are canceled out, and a relative value of self-capacitance that suppresses low-frequency noise is still obtained, thereby suppressing the noise.

[0011] This invention has the following advantages: A capacitive touch detection device, through a switch array, time-division switching of different acquisition channels, requires only one acquisition unit to obtain multiple sampling results of the self-capacitance to ground, significantly reducing the number of acquisition units and effectively lowering costs; by using two resistors to discharge the self-capacitance twice, with different discharge resistances in the two discharges, two different discharge curves are obtained, and the relative value of the self-capacitance to ground is obtained by the difference between the two discharge curves. The two-resistor scheme has a simple structure and simple control timing; by subtracting the two discharge curves, low-frequency noise (such as flicker noise) can be effectively suppressed. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 This is a detailed structural diagram of the present invention; Figure 3 This is a schematic diagram of the conductive pattern. Figure 4 This is a schematic diagram of the detection unit. Figure 5 To control the timing diagram; Figure 6 These are schematic diagrams of waveforms for two discharge stages; Figure 7 This is a schematic diagram of waveform data processing during the discharge phase; Figure 8 Acquire waveforms of noisy signals for the ADC; Figure 9 This is a schematic diagram of waveform data processing for noisy signals; In the diagram: 101-Capacitive touch device, 102-Wire, 103-Touch detection chip, 104-Capacitance detection module, 105-Computation unit, 201-Conductive pattern, 202-Self-capacitance to ground, 204-Detection unit, 205-Switch array, 210-Small capacitor, 301-Analog-to-digital conversion unit, 302-K1 switch, 303-K2 switch, 304 Secondary discharge resistor, 305-Main discharge resistor, 306-K3 switch, 501-Discharge curve obtained by only turning on switch K1 during the discharge phase, 502-Discharge curve obtained by turning on both switches K1 and K2 during the discharge phase. Detailed Implementation

[0013] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the detailed description of the embodiments of this application provided below with reference to the accompanying drawings is not intended to limit the scope of protection of the claimed application, but merely represents selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application. The present invention will be further described below with reference to the accompanying drawings.

[0014] like Figure 1 As shown, this invention specifically relates to a capacitive touch detection device, mainly applied in the detection of capacitive touch devices, and can be used in touch detection chips. It includes a touch detection chip 103 and a capacitive touch device 101, which are connected by a wire 102. The capacitive touch device 101 is the unit being detected, a conversion device that transforms touch actions into capacitance changes. The touch detection chip 103 is the main detection component, used to sense the capacitance change of the capacitive touch device, and obtains the final capacitance value through an internal calculation unit 105.

[0015] like Figure 2 and Figure 3 As shown, the internal circuit structure of the capacitive touch device 101 is a conductive pattern 201. The conductive pattern 201 consists of a series of repeating patterns with a point-to-ground area. These repeating patterns have conductive properties and form a connected complete pattern. Each repeating pattern forms a small capacitor 210 to ground. Because one of the plates of these small capacitors 210 is conductive, they are connected in parallel to form a larger self-capacitance 202 to ground. Each conductive pattern 201 forms a self-capacitance 202 to ground. The main focus of this invention is to detect the capacitance values ​​C_s0…C_sn of these self-capacitances to ground 202. The conductive pattern 201 is connected to the capacitance detection module 104 via wires 102. The capacitance detection module 104 mainly consists of a switch array 205 and a detection unit 204.

[0016] By turning on one of the switches S0-Sn, CH0-CHN can be connected to the detection unit 204 to detect the self-capacitance to ground 202.

[0017] like Figure 4 As shown, the detection unit 204 internally consists of an analog-to-digital converter (ADC) unit 301, a K1 switch 302, a K2 switch 303, a K3 switch 306, a main discharge resistor 305 (R1), and a secondary discharge resistor 304 (R2). The signal selected from the switch array 205 is connected to the ADC unit 301, the K3 switch 306, and the K1 switch 302. The specific workflow is as follows: (1) First turn on switch K3 306, turn off switch K1 302 and switch K2 303, and raise the voltage of the input port of analog-to-digital converter 301 to VDD voltage. VDD voltage is a voltage higher than 0V above ground plane.

[0018] (2) Turn off switch K3 306 and turn on switch K1 302, while keeping switch K2 303 off. At this time, since the capacitor has the charge injected in step (1), the capacitor discharges to the main discharge resistor 305.

[0019] (3) The voltage value recorded by the analog-to-digital conversion unit 301 throughout the process.

[0020] (4) After the charge on the self-capacitor to ground is completely discharged by the main discharge resistor 305, disconnect switch K1 302 and switch K2 303, and turn switch K3 306 on again to raise the voltage at the input port of analog-to-digital converter unit 301 to VDD voltage. VDD voltage is a voltage higher than 0V above the ground plane.

[0021] (5) Turn off switch K3 306 and turn on switch K1 302 and switch K2 303. At this time, since there is injected charge on the capacitor, the capacitor discharges to the main discharge resistor 305 and the auxiliary discharge resistor 304.

[0022] (6) During step (5), the voltage value recorded by the analog-to-digital conversion unit 301.

[0023] like Figure 5 As shown, each charging of switch K3 306 and each discharging of switch K1 302 / K1 switch 302+K2 switch 303 is recorded as one cycle. Figure 4 The first cycle is denoted as the main discharge process, and the second cycle as the secondary discharge process. Comparing the main and secondary discharge processes in a single graph reveals a slight difference in the waveforms. This difference primarily stems from the addition of the secondary discharge resistor 304 to the discharge resistor during the secondary discharge process, which slows down the discharge rate and causes a slight upward shift in the discharge curve. By subtracting the ADC values ​​of the two discharge curves, a difference is obtained. The area formed by this difference is related to the ratio of the self-capacitance of Cs to ground 202 to the secondary discharge resistor 304. A larger Cs will result in a smaller area; a smaller secondary discharge resistor will also result in a smaller area. With the secondary discharge resistor fixed, the size of C_sn is directly proportional to the area of ​​this difference. Therefore, by subtracting the ADC curves of the main and secondary discharge processes and calculating the area, the relative size of C_sn can be obtained.

[0024] like Figure 6 and Figure 7 As shown, the function of calculation unit 105 is to subtract the ADC curves of the main and auxiliary discharge processes in the digital domain and integrate the difference in the time domain. Curve 501 is the discharge curve obtained when only switch K1 is turned on during the discharge phase (but not when switch K2 is turned on). Curve 502 is the discharge curve obtained when both switches K1 and K2 are turned on during the discharge phase. Because the discharge resistance is smaller, the discharge speed is faster, hence it is slightly lower than curve 501. The calculation process is as follows: (1) Align the ADC sampling values ​​of the main and auxiliary discharge processes to the same starting point; (2) At each moment, the ADC sampled values ​​of the main and auxiliary discharge processes are subtracted one by one and stored; (3) Integrate the differences obtained in (2) one by one to get a summation value, which is the relative capacitance value of this sampling.

[0025] like Figure 8 and Figure 9As shown, during the sampling process, some low-frequency noise is introduced, such as noise from the ground plane or flicker noise. The reduced frequency of this noise can be considered as superimposing a bias voltage onto the sampled value of the analog-to-digital converter 301. This bias voltage is simultaneously superimposed on the main and auxiliary discharge curves, and the difference between the two discharge curves cancels each other out, still yielding a self-capacitance relative value that suppresses low-frequency noise, effectively suppressing the noise.

[0026] The above description is merely a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and improvements, and can be altered within the scope of the concept described herein through the above teachings or related technologies or knowledge. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims.

Claims

1. A capacitive touch detection device, characterized in that: It includes a capacitive touch device and a touch detection chip connected thereto; the touch detection chip includes a capacitance detection module and a computing unit connected thereto; The capacitive touch device is configured to convert touch actions into signals of capacitance changes and send them to the touch detection chip. The touch detection chip is configured to sense the capacitance change of the capacitive touch device through the capacitance detection module, and then obtain the final capacitance value through the calculation unit. The capacitive touch device includes multiple conductive patterns, which are connected to a capacitance detection module via wires. Each conductive pattern consists of a series of repeating patterns with one point to ground. Each repeating pattern forms a small capacitor to ground, and all the small capacitors are connected in parallel to form a self-capacitance to ground. The capacitance detection module includes a switch array and a detection unit connected thereto; each conductive pattern is connected to a switch in the switch array via a wire, and by controlling the conduction state of each switch, the corresponding conductive pattern is connected to the detection unit for detection of self-capacitance to ground; The calculation unit performs a subtraction operation on the ADC curves of the main discharge process and the auxiliary discharge process in the digital domain, and integrates the difference in the time domain, specifically including: Align the ADC sample values ​​of the main discharge process and the auxiliary discharge process to the same starting point; At each moment, the ADC sampled values ​​of the discharge process and the auxiliary discharge process are subtracted one by one and stored; Integrate the differences one by one to obtain a summation value, which is the relative capacitance value of this sample.

2. The capacitive touch detection device according to claim 1, characterized in that: The detection unit includes an analog-to-digital converter, switches K1, K2 and K3, a main discharge resistor R1 and a secondary discharge resistor R2; the signal selected from the switch array is respectively connected to the analog-to-digital converter, switch K3 and switch K1; The other end of switch K3 is connected to the VDD voltage terminal. Switch K1 is connected to the main discharge resistor R1 and switch K2 respectively. Switch K2 is connected to the auxiliary discharge resistor R2.

3. The capacitive touch detection device according to claim 2, characterized in that: The working process of the detection unit includes: Turning on switch K3 and turning off switches K1 and K2 raises the voltage at the input port of the analog-to-digital converter to VDD voltage. When switch K3 is turned off, switch K1 is turned on, and switch K2 remains off, the self-capacitance to ground discharges to the main discharge resistor R1. This process is the main discharge process. The analog-to-digital converter records the voltage value. When the charge on the self-capacitor to ground is discharged by the main discharge resistor R1, switch K1 is turned off and switch K3 is turned on again, raising the voltage at the input port of the analog-to-digital converter back to VDD voltage. When switch K3 is turned off and switches K1 and K2 are turned on, the self-capacitance to ground discharges to the main discharge resistor R1 and the auxiliary discharge resistor R2. This process is the auxiliary discharge process, and the analog-to-digital conversion unit records the voltage value.

4. The capacitive touch detection device according to claim 3, characterized in that: During the sampling process, a bias voltage is superimposed on the sampled value of the analog-to-digital conversion unit. This bias voltage is superimposed on both the main discharge process and the auxiliary discharge process curves. When the two discharge curves are subtracted, they are canceled out, and a relative value of self-capacitance that suppresses low-frequency noise is still obtained, thereby suppressing the noise.

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