A high efficiency touch detection circuit

Abstract

The application discloses a touch detection circuit, comprising: a touch channel equivalent capacitor Cx, an external anti-interference resistor Rx, an internal matching capacitor Cs, a first equivalent resistor Rs, a second equivalent resistor Rf, an internal regulating capacitor Cf, an analog-to-digital converter ADC, a first switch K1, a second switch K2, a third switch K3, a fourth switch K4, a fifth switch K5, and a sixth switch K6, wherein the first equivalent resistor Rs is an equivalent series resistor of the internal matching capacitor Cs to a working power supply VDD, and the second equivalent resistor Rf is an equivalent resistor between the Cf and the Cs. The application can solve the slow response of multiple keys caused by long scanning time, improve the sensitivity, be suitable for wider touch applications, have strong anti-interference ability, and have a good mass production prospect.

Description

Technical Field

[0001] The present invention relates to touch detection technology, and particularly to a high-efficiency touch detection circuit. Background Art

[0002] In a traditional touch detection system, generally, the equivalent capacitance Cx of a touch channel is fully charged, and then the internal matching capacitance Cs is discharged to voltage balance; according to the relationship between this voltage and the voltage Vcm at the A end of the adjustment capacitance Cf, the adjustment capacitance Cf charges Cx and Cs, or Cx and Cs charge the adjustment capacitance Cf; the voltage at the B end of Cf is used as the output of the touch detection result.

[0003] Its principle block diagram is as Figure 1 shown, and the specific working process is as follows:

[0004] Stage 1: The equivalent capacitance Cx of the touch channel is charged completely alone until its voltage reaches VDD (Cx is in the order of pF);

[0005] Stage 2: The charge of the equivalent capacitance Cx of the touch channel is transferred to the internal matching capacitance Cs, making the voltages of Cx and Cs the same (the voltage is Vcs at this time);

[0006] [[ID=2,2]]Stage 3: Charge transfer is performed according to the relationship between the voltage Vcm at the A end of the adjustment capacitance Cf and the voltage V

[0010] of Cs (if V Cs > Vcm, the charges of Cx and Cs are transferred to Cf; if V Cs < Vcm, Cf transfers charges to Cx and Cs); finally, the voltages at the Cx and Cs ends are Vcm; the change in the charge of Cf is manifested as the change in the voltage at the B end of Cf;

[0007] Stage 4: The voltage at the B end of Cf is collected through an analog-to-digital converter and converted into a digital quantity. The digital quantity corresponding to the voltage at the B end of Cf is recorded as the characterization value of the touch key.

[0008] When a finger presses down, the capacitance of Cx increases (the equivalent capacitance of the finger is added), and the amount of charge stored in Cx increases during Stage 1, resulting in an increase in the balance voltage V Cs in Stage 2. More charges are absorbed by Cf or fewer charges are released by Cf, resulting in an increase in the voltage at the B end of Cf, thereby determining whether a key is pressed.

[0009] Generally, the anti-interference ability of touch is improved by multiplying the anti-interference resistors Rx connected in series in the channel; using this touch detection method, Rx increases exponentially, causing the time required for the complete charge and discharge of Cx to increase exponentially, and the scanning time of a single touch channel to increase; when there are many touch keys, it will affect the response speed of the keys, and the customer experience effect is greatly reduced. [[ID=,40]]

[0010] In this method, the equivalent capacitance Cx of the touch channel participates in the entire touch scanning process. External interference, such as electromagnetic interference, enters the chip through the touch pin, affecting the touch scanning and thus affecting the final judgment result of the button, leading to false triggering or missed detection.

[0011] When the touch panel is thick or the touch contact area is small, the equivalent parasitic capacitance Cp when a finger touches a button is small. Using this scanning method, it is difficult to detect whether a button has been pressed.

[0012] In summary, there is an urgent need for a touch detection method that features fast touch scanning speed, high signal-to-noise ratio, and strong anti-interference capabilities. Summary of the Invention

[0013] This invention provides a high-efficiency touch detection circuit that can solve the problem of sluggish response to multiple buttons caused by long scanning time, improve sensitivity, be applicable to a wider range of touch applications, and has strong anti-interference ability, showing good prospects for mass production.

[0014] The touch detection circuit of the present invention includes: a touch channel equivalent capacitance Cx, an external anti-interference resistor Rx, an internal matching capacitor Cs, a first equivalent resistance Rs, a second equivalent resistance Rf, an internal adjustment capacitor Cf, an analog-to-digital converter (ADC), a first switch K1, a second switch K2, a third switch K3, a fourth switch K4, a fifth switch K5, and a sixth switch K6, wherein the first equivalent resistance Rs is the equivalent series resistance of the internal matching capacitor Cs to the operating power supply VDD, and the second equivalent resistance Rf is the equivalent resistance between Cf and Cs.

[0015] The first terminal of the equivalent capacitance Cx of the touch channel is grounded. The second terminal of the equivalent capacitance Cx is coupled to the first terminal of the anti-interference resistor Rx. The second terminal of the anti-interference resistor Rx is coupled to the first terminal of the fourth switch K4, and the second terminal of the fourth switch K4 is grounded. The first terminal of the second switch K2 is coupled to the first terminal of the fourth switch K4. The second terminal of the second switch K2 is coupled to the first terminal of the internal matching capacitor Cs. The first terminal of the internal matching capacitor Cs is coupled to the second terminal of the first switch K1, and the second terminal of the internal matching capacitor Cs is grounded. The first terminal of the first switch K1 is coupled to the second terminal of the first equivalent resistor Rs, and the first terminal of the first equivalent resistor Rs is coupled to the operating power supply VDD. The third switch K3 and the second equivalent resistor Rf are connected in series between the first terminal of the internal matching capacitor Cs and the first terminal of the internal adjustment capacitor Cf. The sixth switch K6 is connected in parallel with the internal adjustment capacitor Cf. The fifth switch K5 is connected in series between the second terminal of the internal adjustment capacitor Cf and the analog-to-digital converter (ADC).

[0016] In one embodiment, the touch detection circuit is configured to perform the following operations:

[0017] a. Keep the first terminal voltage Vcm of the internal regulating capacitor Cf constant, and the charging or discharging action of the internal regulating capacitor Cf is manifested as a change in the second terminal voltage of the internal regulating capacitor Cf;

[0018] b. By charging the internal matching capacitor Cs, the effect of the extended charging time caused by the external anti-interference resistor Rx with a large series resistance value of the equivalent capacitance Cx of the touch channel is eliminated. The external anti-interference resistor Rx with a large resistance value refers to the external anti-interference resistor Rx with a resistance value exceeding a preset threshold.

[0019] c. During the high-efficiency charging and discharging time of the equivalent capacitance Cx of the touch channel, the internal matching capacitor Cs discharges the equivalent capacitance Cx of the touch channel, reducing the time required for the equivalent capacitance Cx of the touch channel to charge or the internal matching capacitor Cs to discharge when the external anti-interference resistor Rx is large.

[0020] d. Based on the voltage relationship between the internal matching capacitor Cs and the first terminal voltage Vcm of the internal regulating capacitor Cf, the internal matching capacitor Cs charges or discharges the internal regulating capacitor Cf;

[0021] e. The voltage change at the second terminal of the internal regulating capacitor Cf, caused by the change in the charge of the internal regulating capacitor Cf, is converted into a digital touch signal through the analog-to-digital converter ADC.

[0022] f. By comparing the touch digits when a finger is pressed and when no finger is pressed, it can be determined whether a button has been pressed.

[0023] g. When the difference in the digital touch value obtained during process f is less than a preset value, processes b to d are executed repeatedly. The change in charge of the internal regulating capacitor Cf is integrated before action e is performed, thereby increasing the amount of finger touch change, reducing the influence of environmental noise, and improving the touch anti-interference capability.

[0024] In one embodiment, the equivalent capacitance Cx of the touch channel only participates in the scanning during process c, while other processes are all internal chip operations, which are unrelated to the outside world. This can greatly reduce the impact of the external environment and interference on the touch and improve the touch anti-interference capability.

[0025] In one embodiment, the first equivalent series resistance Rs is configured to be less than a preset value, so that the internal matching capacitor Cs is quickly charged during process b, thereby eliminating the impact of the increased charging time caused by the exponential increase of the external anti-interference resistor Rx, and reducing the impact of external interference entering the chip through the touch channel pin on touch scanning.

[0026] In one embodiment, the second equivalent resistance Rf is configured to be less than a preset value, so that the voltage of the internal matching capacitor Cs quickly reaches the first terminal voltage Vcm of the internal regulating capacitor Cf during the d process, thereby eliminating the impact of the significant increase in charging time caused by the external anti-interference resistor Rx increasing exponentially; at the same time, it also reduces the impact of external interference entering the chip through the touch channel pin and affecting touch scanning.

[0027] In one embodiment, by utilizing the high-efficiency phase of capacitor charging and discharging, the time required for the equivalent capacitance Cx of the touch channel to charge or the internal matching capacitor Cs to discharge when the external anti-interference resistor Rx is large is reduced, thereby lowering the touch scanning time.

[0028] The present invention also provides a touch detection circuit, comprising: a touch channel equivalent capacitance Cx, an external anti-interference resistor Rx, an internal matching capacitor Cs, a first equivalent resistance Rs, a second equivalent resistance Rf, an internal adjustment capacitor Cf, an analog-to-digital converter ADC, a first switch K1, a second switch K2, a third switch K3, a fourth switch K4, a fifth switch K5, and a sixth switch K6, wherein the first equivalent resistance Rs is the equivalent series resistance of the internal matching capacitor Cs to ground, and the second equivalent resistance Rf is the equivalent resistance between Cf and Cs.

[0029] The first terminal of the equivalent capacitance Cx of the touch channel is grounded. The second terminal of the equivalent capacitance Cx is coupled to the first terminal of the external anti-interference resistor Rx. The second terminal of the external anti-interference resistor Rx is coupled to the first terminal of the fourth switch K4. The second terminal of the fourth switch K4 is connected to the first reference voltage Vref1. The first terminal of the second switch K2 is coupled to the first terminal of the fourth switch K4. The second terminal of the second switch K2 is coupled to the first terminal of the internal matching capacitor Cs. The first terminal of the internal matching capacitor Cs is coupled to the second terminal of the first switch K1. The second terminal of the internal matching capacitor Cs is connected to the second reference voltage Vref2. The first terminal of the first switch K1 is coupled to the second terminal of the first equivalent resistor Rs. The first terminal of the first equivalent resistor Rs is coupled to ground. The third switch K3 and the second equivalent resistor Rf are connected in series between the first terminal of the internal matching capacitor Cs and the first terminal of the internal adjustment capacitor Cf. The sixth switch K6 is connected in parallel with the internal adjustment capacitor Cf. The fifth switch K5 is connected in series between the second terminal of the internal adjustment capacitor Cf and the analog-to-digital converter (ADC).

[0030] In one embodiment, the touch detection circuit is configured to perform the following operations:

[0031] a. Keep the first terminal voltage Vcm of the internal regulating capacitor Cf constant, and the charging or discharging action of the internal regulating capacitor Cf is manifested as a change in the second terminal voltage of the internal regulating capacitor Cf;

[0032] b. During the high-efficiency charging time of the equivalent capacitance Cx of the touch channel, the first reference voltage Vref1 charges the equivalent capacitance Cx of the touch channel to reduce the charging time required for the equivalent capacitance Cx of the touch channel when the external anti-interference resistor Rx is large; wherein, the external anti-interference resistor Rx being large means that the resistance value of the external anti-interference resistor Rx exceeds a preset threshold.

[0033] c. During the high-efficiency charging and discharging time of the equivalent capacitance Cx of the touch channel, the internal matching capacitor Cs discharges the equivalent capacitance Cx of the touch channel or the equivalent capacitance Cx of the touch channel discharges the internal matching capacitor Cs, thereby reducing the time required for the equivalent capacitance Cx of the touch channel or the internal matching capacitor Cs to charge when the external anti-interference resistor Rx is large.

[0034] d. Based on the voltage relationship between the internal matching capacitor Cs and the first terminal voltage Vcm of the internal regulating capacitor Cf, the internal matching capacitor Cs charges or discharges the internal regulating capacitor Cf;

[0035] e. The voltage change at the second terminal of the internal regulating capacitor Cf, caused by the change in the charge of the internal regulating capacitor Cf, is converted into a digital touch signal through the analog-to-digital converter ADC.

[0036] f. By comparing the touch digits when a finger is pressed and when no finger is pressed, it can be determined whether a button has been pressed.

[0037] g. When the difference in the digital touch value obtained during process f is less than a preset value, processes b to d are executed repeatedly. The change in charge of the internal regulating capacitor Cf is integrated before action e is performed, thereby increasing the amount of finger touch change, reducing the influence of environmental noise, and improving the touch anti-interference capability.

[0038] In one embodiment, the equivalent capacitance Cx of the touch channel only participates in scanning during processes b and c, while other processes are all internal chip operations, which are unrelated to the outside world. This can reduce the impact of the external environment and interference on the touch and improve the touch anti-interference capability.

[0039] In one embodiment, by utilizing the high-efficiency phase of capacitor charging and discharging, the time required for the equivalent capacitance Cx of the touch channel or the internal matching capacitor Cs to charge when the external anti-interference resistor Rx is large is reduced, thereby lowering the touch scanning time.

[0040] In one embodiment, the second equivalent resistance Rf is configured to be less than a preset value, so that the voltage of the internal matching capacitor Cs quickly reaches the first terminal voltage Vcm of the internal regulating capacitor Cf during the d process, thereby eliminating the impact of the significant increase in charging time caused by the external anti-interference resistor Rx increasing exponentially; at the same time, it also reduces the impact of external interference entering the chip through the touch channel pin and affecting touch scanning.

[0041] Compared with existing touch detection solutions, the present invention has the following advantages:

[0042] The scan time is very short, and the amount of touch change meets the needs of most touch applications, supporting more touch button applications;

[0043] When the touch panel is thick or the contact area is small, resulting in a small amount of touch change, the amount of touch change can be increased by increasing the number of cycles N in the charge integration process, thereby increasing the charge change of the internal regulating capacitor Cf.

[0044] Multiple charge integration processes can reduce the impact of random environmental interference, thereby improving the touch signal-to-noise ratio and enhancing the touch anti-interference capability.

[0045] Because the equivalent capacitance Cx of the touch channel only participates in the scanning during process c or processes b and c, and the scanning time is very short, the other processes are all internal chip operations and are not related to the outside world. This can greatly reduce the impact of the external environment and interference on the touch and improve the touch anti-interference capability. Attached Figure Description

[0046] The above-described invention and the following detailed description will be better understood when read in conjunction with the accompanying drawings. It should be noted that the drawings are merely examples of the claimed invention. In the drawings, the same reference numerals represent the same or similar elements.

[0047] Figure 1 This demonstrates a traditional touch detection method;

[0048] Figure 2 A touch detection circuit according to an embodiment of the present invention is shown;

[0049] Figure 3 A touch detection circuit according to an embodiment of the present invention is shown;

[0050] Figure 4 A scanning flowchart of a touch detection circuit according to an embodiment of the present invention is shown;

[0051] Figure 5 A schematic diagram of the initial state of a touch detection circuit according to an embodiment of the present invention is shown;

[0052] Figure 6A schematic diagram of Cs charging and Cx discharging in a touch detection circuit according to an embodiment of the present invention is shown;

[0053] Figure 7 A schematic diagram showing a comparison of charging time between the touch detection method of the present invention and the traditional touch detection method is provided.

[0054] Figure 8 A schematic diagram of Cs charging Cx in a touch detection circuit according to an embodiment of the present invention is shown;

[0055] Figure 9 The graph shows the change of voltage Cx over time in a touch detection circuit according to an embodiment of the present invention.

[0056] Figure 10 A schematic diagram is shown of Cf absorbing or releasing charge in a touch detection circuit according to an embodiment of the present invention;

[0057] Figure 11 When Vcm is greater than V Cs At that time, the existing technical solution and the present invention in step 3 V Cs A comparison diagram showing the time required to charge to Vcm;

[0058] Figure 12 The graph shows the change in the voltage Vout at the B terminal of Cf during the 5-cycle execution of the Cf charge integration operation.

[0059] Figure 13 A schematic diagram of ADC sampling according to an embodiment of the present invention is shown;

[0060] Figure 14 A schematic diagram of ADC conversion according to an embodiment of the present invention is shown;

[0061] Figure 15 This is a comparison of the time required for existing touch solutions and the present invention in a single scan process;

[0062] Figure 16 The curves showing the change in voltage Vout at terminal B of Cf with and without finger touch are displayed. Detailed Implementation

[0063] The following detailed description of the features and advantages of the present invention is sufficient to enable any person skilled in the art to understand the technical content of the present invention and implement it accordingly. Furthermore, based on the specification, claims and drawings disclosed herein, those skilled in the art can easily understand the related objects and advantages of the present invention.

[0064] Most existing touch detection principles rely on charging and discharging capacitors for touch detection. During this process, the charging / discharging time of the capacitor is extended to ensure complete charging and discharging. However, sometimes, to improve touch interference immunity, the interference-resistant resistor Rx connected in series with the touch channel is increased exponentially. This increases the time required for the parasitic capacitance Cx of the touch channel to fully charge and discharge, thus increasing the scanning time of a single touch channel. When there are many buttons, this affects the button response speed and significantly reduces the user experience. This invention improves the touch scanning circuit and utilizes the high-efficiency portion of the capacitor charging and discharging process for touch detection, greatly shortening the touch detection time and improving the touch response speed.

[0065] In some touch detection principles, the touch channel participates in the entire touch scanning process. When external interference is significant, it can enter the chip through the touch pins, affecting the touch scanning and causing incorrect touch button recognition. In this invention, by improving the touch scanning circuit and incorporating a high-efficiency capacitor charging and discharging mechanism, the touch channel only participates in a portion of the scanning process, reducing the impact of external interference entering the chip through the touch channel pins and affecting the touch scanning.

[0066] In some touch applications, due to the thickness of the panel, the large external parasitic capacitance, or the small touch contact area, the amount of touch change when a finger touches a button is small. If traditional methods are used, it is difficult to detect whether there is a touch change. In this invention, a high-efficiency touch detection mechanism is adopted to achieve multiple touch detections in the same time period. By integrating the extremely small touch change, the touch change is amplified. While increasing the amount of touch change, the influence of random environmental interference on the touch is reduced, thereby improving the signal-to-noise ratio and the touch anti-interference capability.

[0067] Figure 1 This is a traditional touch detection method (hereinafter referred to as the existing technical solution). Figure 1 In this method, touch detection is achieved through processes such as "VDD fully charging Cx (time T1)," "Cx discharging Cs until voltage balance (time T2)," "Cf charging Cx and Cs or Cx and Cs charging Cf (time T3)," and "ADC voltage acquisition and conversion (time t4+t5)." In this method, Cx and Rx participate in the entire detection process.

[0068] This approach has the following drawbacks:

[0069] First, when there is significant external interference, the touch channel in this traditional solution participates in the entire touch detection process. Interference can easily enter the chip through the touch pins, affecting the entire touch detection and causing touch button recognition errors.

[0070] Secondly, to reduce the impact of external interference, the anti-interference resistor Rx connected in series with the touch channel is typically increased several times, from a few kΩ to tens or even hundreds of kΩ. With this detection scheme, to ensure complete charging and discharging of Cx, the time for each touch scanning process increases several times due to the significantly increased series resistance Rx. This means that the time for one round of touch scanning increases exponentially. When there are many touch buttons in a practical application, this significantly increased touch scanning time can cause sluggish touch button response, affecting the user experience.

[0071] Furthermore, when the touch panel is thick or the touch contact area is small, the equivalent parasitic capacitance Cp when a finger touches a button is small, making it difficult to detect whether a button has been pressed using this scanning method.

[0072] To reduce the impact of increased series resistance Rx in the touch channel on touch scanning time, improve the touch signal-to-noise ratio, and enhance anti-interference capability, this invention improves upon the aforementioned detection method. The improved touch detection circuit is as follows: Figure 2 As shown.

[0073] like Figure 2 As shown, the touch detection circuit of the present invention includes a touch channel equivalent capacitance Cx, an external anti-interference resistor Rx, an internal matching capacitor Cs, a first equivalent resistance Rs, a second equivalent resistance Rf, an internal adjustment capacitor Cf, an analog-to-digital converter (ADC), a first switch K1, a second switch K2, a third switch K3, a fourth switch K4, a fifth switch K5, and a sixth switch K6, wherein the first equivalent resistance Rs is the equivalent series resistance of the internal matching capacitor Cs to the working power supply VDD, and the second equivalent resistance Rf is the equivalent resistance between Cf and Cs.

[0074] The first terminal of the touch channel equivalent capacitance Cx is grounded. The second terminal of the touch channel equivalent capacitance Cx is coupled to the first terminal of the anti-interference resistor Rx. The second terminal of the anti-interference resistor Rx is coupled to the first terminal of the fourth switch K4, and the second terminal of the fourth switch K4 is grounded. The first terminal of the second switch K2 is coupled to the first terminal of the fourth switch K4. The second terminal of the second switch K2 is coupled to the first terminal of the internal matching capacitor Cs. The first terminal of the internal matching capacitor Cs is coupled to the second terminal of the first switch K1, and the second terminal of the internal matching capacitor Cs is grounded. The first terminal of the first switch K1 is coupled to the second terminal of the first equivalent resistor Rs, and the first terminal of the first equivalent resistor Rs is coupled to the operating power supply VDD. The third switch K3 and the second equivalent resistor Rf are connected in series between the first terminal of the internal matching capacitor Cs and the first terminal (terminal A) of the internal regulating capacitor Cf. The sixth switch K6 is connected in parallel with the internal regulating capacitor Cf. The fifth switch K5 is connected in series between the second terminal (terminal B) of the internal regulating capacitor Cf and the analog-to-digital converter (ADC).

[0075] The touch detection circuit is configured to perform the following actions:

[0076] a. Keep the first terminal voltage Vcm of the internal regulating capacitor Cf constant, and the charging or discharging action of the internal regulating capacitor Cf is manifested as a change in the second terminal voltage of the internal regulating capacitor Cf;

[0077] b. By charging the internal matching capacitor Cs, the effect of the extended charging time caused by the external anti-interference resistor Rx with a large series resistance value of the equivalent capacitance Cx of the touch channel is eliminated. The external anti-interference resistor Rx with a large resistance value refers to the external anti-interference resistor Rx with a resistance value exceeding a preset threshold.

[0078] c. During the high-efficiency charging and discharging time of the equivalent capacitance Cx of the touch channel, the internal matching capacitor Cs discharges the equivalent capacitance Cx of the touch channel, reducing the time required for the equivalent capacitance Cx of the touch channel to charge or the internal matching capacitor Cs to discharge when the external anti-interference resistor Rx is large.

[0079] d. Based on the voltage relationship between the internal matching capacitor Cs and the first terminal voltage Vcm of the internal regulating capacitor Cf, the internal matching capacitor Cs charges or discharges the internal regulating capacitor Cf;

[0080] e. The voltage change at the second terminal of the internal regulating capacitor Cf, caused by the change in the charge of the internal regulating capacitor Cf, is converted into a digital touch signal through the analog-to-digital converter ADC.

[0081] f. By comparing the touch digits when a finger is pressed and when no finger is pressed, it can be determined whether a button has been pressed.

[0082] g. When the difference in the digital touch value obtained during process f is less than a preset value, processes b to d are executed repeatedly. The change in charge of the internal regulating capacitor Cf is integrated before action e is performed, thereby increasing the amount of finger touch change, reducing the influence of environmental noise, and improving the touch anti-interference capability.

[0083] Specifically, Figure 2 The scanning flowchart of the touch detection circuit is as follows: Figure 4 As shown in Table 1:

[0084] Table 1 Internal Switching Sequence for Each Stage of Touch Control

[0085]

[0086]

[0087] Combining the switching timing in Table 1 and Figure 4 The scanning process at each stage will be described in detail below.

[0088] The touch detection method of the present invention includes:

[0089] 401: Initial state;

[0090] 402:Cf charge collection;

[0091] 403:Cf charge integral;

[0092] 404: Analog-to-digital converter sampling and conversion;

[0093] 405: One channel scan completed.

[0094] Initial state 401 includes the following steps:

[0095] Step 0: Initial state before the touch channel begins scanning. K6 is closed, other switches are open, ensuring a consistent voltage across Cf, with no charge. Figure 5 As shown.

[0096] The Cf charge acquisition process 402 includes the following steps 1 to 3:

[0097] Step 1: K1 and K4 are closed, other switches are open: Utilizing the small equivalent series resistance Rs of the internal matching capacitor Cs to VDD (circuit design implementation), VDD rapidly charges Cs, and within time t1, the voltage at the Cs terminal eventually reaches VDD; simultaneously, Cx discharges to GND; the scanning circuit is as follows... Figure 6 As shown.

[0098] Compared to existing touch detection circuits, this step has the following advantages:

[0099] Because the equivalent series resistance Rs of the internal matching capacitor Cs to VDD is very small (e.g., less than a preset value), the voltage of Cs can be charged to VDD within a very short time t1, eliminating the effect of a significant increase in charging time caused by the external anti-interference resistor Rx increasing exponentially.

[0100] It also reduces external interference from entering the chip through the touch channel pins and affecting touch scanning.

[0101] Figure 7 This is a comparison of the charging time in step 1 between the present invention and the prior art, where t1 is the charging time required in step 1 of the present invention, and T1 is the charging time required in step 1 of the prior art; from Figure 7 It is evident that the present invention can significantly reduce scanning time in step 1.

[0102] Step 2: K2 is closed, and other switches are open: Cs charges Cx. When the charging is complete, the voltage at the Cs terminal drops from VDD to V. Cs The voltage at terminal Cx rises from 0V to V. Cx;like Figure 8 As shown.

[0103] During this process, Rx participates in charge transfer, and Cs discharges to Cx until "V" is reached. Cx =V Cs "The required time is at least 5Rx*C (C is the equivalent capacitance of the discharge circuit); because the resistance of Rx is relatively large, the time required for this process to reach equilibrium is relatively long."

[0104] According to the characteristics of RC charging, the charging efficiency gradually decreases with time, and the charge absorbed by Cx gradually decreases. Taking advantage of the gradually decreasing charging and discharging efficiency of Cx, Cs charges Cx during the high-efficiency stage t2 (t2=t1+t3), as follows: Figure 9 As shown: 0~T` is the high-efficiency charging stage of the capacitor, and T`~T`` is the low-efficiency charging stage. The scan time t2 in step 2 should be within 0~T` as much as possible.

[0105] Step 3: K3 / K4 closed, other switches open: disconnect Cx and Cs, Cx discharges to GND; according to V Cs The relationship between Cf and the voltage Vcm at terminal A is such that Cf charges Cs or Cs charges Cf; the amount of charge released or absorbed by Cf is Q. Because of the change in the charge of Cf, the voltage at terminal B of Cf increases or decreases by Q / Cf. The scanning circuit is as follows... Figure 10 As shown.

[0106] Compared to existing touch detection circuits, this step has the following advantages:

[0107] Because the equivalent resistance Rf between Cf and Cs is very small (in circuit design implementation, for example, less than a preset value), the voltage of Cs can reach Vcm voltage within a very short time t3, eliminating the impact of a significant increase in charging time caused by the external anti-interference resistor Rx increasing exponentially; at the same time, it also reduces the impact of external interference entering the chip through the touch channel pin and affecting touch scanning.

[0108] Figure 11 When Vcm is greater than V Cs At that time, the existing technical solution and the present invention in step 3 V Cs Comparison of charging time to Vcm: t3 is the charging time required in step 3 of this invention. Cs The time required to reach Vcm, T3 is the time required for V in step 3 of the existing technical solution. Cs The time required to reach Vcm. As can be clearly seen from the figure, the present invention can significantly reduce the scanning time in step 3.

[0109] Cf charge integration 403 includes the following steps:

[0110] Step 4: Repeat steps 1 to 3 N times to perform N charge integration operations on the internal regulating capacitor Cf.

[0111] In step 2, Cx is charged from 0V to V. Cx The time is t2 = t1 + t3. Starting from step 3, Cx discharges to GND until the end of step 1. The time is t1 + t3. The charging time and discharging time of Cx are the same. Thus, Cx is completely discharged after the end of step 1, and the voltage is 0V.

[0112] Since the voltage at terminal A of Cf remains constant (Vcm), steps 1 to 3 are repeated cyclically to perform charge integration on Cf, resulting in the final charge change Q of Cf. 总 as follows:

[0113] Where N represents the number of cycles, Q represents the charge change per cycle, and the voltage change at terminal B of Cf, Vout, is Q. 总 / Cf.

[0114] Figure 12 The graph shows the change in voltage Vout at terminal B of Cf during the 5-cycle execution of the Cf charge integration operation. Cs >Vcm).

[0115] advantage:

[0116] Performing N charge integration operations on Cf can eliminate the problem of reduced touch change caused by incomplete charging of Cx;

[0117] Compared with the prior art, in the entire charge integration process, the charging of Cx is in a high-efficiency stage. The total amount of charge acquired by Cx in the same time period increases, the amount of charge affected by the finger capacitance Cp increases, and ultimately the voltage change at the B terminal of Cf increases, resulting in a larger change in touch intensity.

[0118] Meanwhile, multiple integration actions effectively reduce the impact of external environmental noise on touch and improve the touch signal-to-noise ratio.

[0119] The analog-to-digital converter (ADC) sampling and conversion 404 includes the following steps:

[0120] Step 5: K4 / K5 are closed, and other switches are open; within time t4, the analog-to-digital converter (ADC) acquires the voltage at the sensitivity capacitor CfB; simultaneously, Cx continues to discharge GND. The scanning circuit is as follows: Figure 13 As shown.

[0121] Step 6: K4 / K6 closes, other switches open; within time t5, the analog-to-digital converter (ADC) converts the voltage acquired in step 5 into a digital value; simultaneously, Cx continues to discharge GND, and Cf discharges until Cf is free of charge; one touch channel scan ends 405. The scanning circuit is as follows... Figure 14 As shown.

[0122] Figure 15 This compares the time required for a single scan between existing touch solutions and the present invention. The total scan time for the existing solution is T = T1 + T2 + T3 + t4 + t5, while the total scan time for the present invention is t = t1 + t2 + t3 + t4 + t5. Figure 15 It is evident that this invention can significantly reduce touch scanning time.

[0123] When a finger touches the screen, the equivalent parasitic capacitance Cx of the touch channel increases to Cx+Cp, causing V in step 2 of the touch scanning phase. Cs A decrease in voltage affects the amount of charge released or absorbed by Cf.

[0124] The button press is detected by detecting the voltage change corresponding to this charge amount, such as... Figure 16 Vout is the final voltage (V) when no finger is pressed down. Cs >Vcm), Vout1 is the final voltage under finger touch, and the voltage change ΔV shown by finger touch is: Vout1-Vout.

[0125] Compared with existing touch detection solutions, the present invention has the following advantages:

[0126] The scan time is very short, and the amount of touch change meets the needs of most touch applications, supporting more touch button applications;

[0127] When the touch panel is thick or the contact area is small, resulting in a small amount of touch change, the amount of touch change can be increased by increasing the number of cycles N in the charge integration process, thereby increasing the charge change of the internal regulating capacitor Cf.

[0128] Multiple charge integration processes can reduce the impact of random environmental interference, thereby improving the touch signal-to-noise ratio and enhancing the touch anti-interference capability.

[0129] Because the equivalent capacitance Cx of the touch channel only participates in the scanning process in step 2 (process c), and the scanning time is very short, the other processes are all internal chip operations and are not related to the outside world. This can greatly reduce the impact of the external environment and interference on the touch and improve the touch anti-interference capability.

[0130] Figure 3A touch detection circuit according to another embodiment of the present invention is shown. It should be noted that the touch detection circuit of the present invention is not limited to... Figure 2 and Figure 3 As shown. The touch detection circuit of the present invention can also have various variations.

[0131] like Figure 3 As shown, the touch detection circuit includes a touch channel equivalent capacitance Cx, an external anti-interference resistor Rx, an internal matching capacitor Cs, a first equivalent resistance Rs, a second equivalent resistance Rf, an internal adjustment capacitor Cf, an analog-to-digital converter (ADC), a first switch K1, a second switch K2, a third switch K3, a fourth switch K4, a fifth switch K5, and a sixth switch K6. The first equivalent resistance Rs is the equivalent series resistance of the internal matching capacitor Cs to ground, and the second equivalent resistance Rf is the equivalent resistance between Cf and Cs.

[0132] Specifically, the first terminal of the equivalent capacitance Cx of the touch channel is grounded, the second terminal of the equivalent capacitance Cx is coupled to the first terminal of the external anti-interference resistor Rx, the second terminal of the external anti-interference resistor Rx is coupled to the first terminal of the fourth switch K4, and the second terminal of the fourth switch K4 is connected to the first reference voltage Vref1; the first terminal of the second switch K2 is coupled to the first terminal of the fourth switch K4, the second terminal of the second switch K2 is coupled to the first terminal of the internal matching capacitor Cs, the first terminal of the internal matching capacitor Cs is coupled to the second terminal of the first switch K1, the second terminal of the internal matching capacitor Cs is connected to the second reference voltage Vref2, the first terminal of the first switch K1 is coupled to the second terminal of the first equivalent resistor Rs, and the first terminal of the first equivalent resistor Rs is coupled to ground; the third switch K3 and the second equivalent resistor Rf are connected in series between the first terminal of the internal matching capacitor Cs and the first terminal of the internal adjustment capacitor Cf; the sixth switch K6 is connected in parallel with the internal adjustment capacitor Cf; and the fifth switch K5 is connected in series between the second terminal of the internal adjustment capacitor Cf and the analog-to-digital converter (ADC).

[0133] The touch detection circuit of the present invention is configured to perform the following operations:

[0134] a. Keep the first terminal voltage Vcm of the internal regulating capacitor Cf constant, and the charging or discharging action of the internal regulating capacitor Cf is manifested as a change in the second terminal voltage of the internal regulating capacitor Cf;

[0135] b. During the high-efficiency charging time of the equivalent capacitance Cx of the touch channel, the first reference voltage Vref1 charges the equivalent capacitance Cx of the touch channel, reducing the charging time required for the equivalent capacitance Cx of the touch channel when the external anti-interference resistor Rx is large; wherein, the external anti-interference resistor Rx being large means that the resistance value of the external anti-interference resistor Rx exceeds a preset value.

[0136] c. During the high-efficiency charging and discharging time of the equivalent capacitance Cx of the touch channel, the internal matching capacitor Cs discharges the equivalent capacitance Cx of the touch channel or the equivalent capacitance Cx of the touch channel discharges the internal matching capacitor Cs, thereby reducing the time required for the equivalent capacitance Cx of the touch channel or the internal matching capacitor Cs to charge when the external anti-interference resistor Rx is large.

[0137] d. Based on the voltage relationship between the internal matching capacitor Cs and the first terminal voltage Vcm of the internal regulating capacitor Cf, the internal matching capacitor Cs charges or discharges the internal regulating capacitor Cf;

[0138] e. The voltage change at the second terminal of the internal regulating capacitor Cf, caused by the change in the charge of the internal regulating capacitor Cf, is converted into a digital touch signal through the analog-to-digital converter ADC.

[0139] f. By comparing the touch digits when a finger is pressed and when no finger is pressed, it can be determined whether a button has been pressed.

[0140] g. When the difference in the digital touch value obtained during process f is less than a preset value, processes b to d are executed repeatedly. The change in charge of the internal regulating capacitor Cf is integrated before action e is performed, thereby increasing the amount of finger touch change, reducing the influence of environmental noise, and improving the touch anti-interference capability.

[0141] The terminology and expressions used herein are for descriptive purposes only, and the invention should not be limited to these terms and expressions. The use of these terms and expressions does not imply the exclusion of any illustrative and descriptive equivalents (or parts thereof), and it should be recognized that various modifications that may exist should also be included within the scope of the claims. Other modifications, variations, and substitutions may also exist. Accordingly, the claims should be considered to cover all such equivalents.

[0142] Similarly, it should be noted that although the present invention has been described with reference to the specific embodiments described above, those skilled in the art should recognize that the above embodiments are only used to illustrate the present invention, and various equivalent changes or substitutions can be made without departing from the spirit of the present invention. Therefore, any changes or modifications to the above embodiments within the scope of the essential spirit of the present invention will fall within the scope of the claims of this application.

Claims

1. A touch detection circuit, characterized in that, include: The circuit includes a touch channel equivalent capacitance Cx, an external anti-interference resistor Rx, an internal matching capacitor Cs, a first equivalent resistance Rs, a second equivalent resistance Rf, an internal adjustment capacitor Cf, an analog-to-digital converter (ADC), a first switch K1, a second switch K2, a third switch K3, a fourth switch K4, a fifth switch K5, and a sixth switch K6. The first equivalent resistance Rs is the equivalent series resistance of the internal matching capacitor Cs to the operating power supply VDD, and the second equivalent resistance Rf is the equivalent resistance between Cf and Cs. The first terminal of the equivalent capacitance Cx of the touch channel is grounded; the second terminal of the equivalent capacitance Cx is coupled to the first terminal of the anti-interference resistor Rx; the second terminal of the external anti-interference resistor Rx is coupled to the first terminal of the fourth switch K4, and the second terminal of the fourth switch K4 is grounded; the first terminal of the second switch K2 is coupled to the first terminal of the fourth switch K4; the second terminal of the second switch K2 is coupled to the first terminal of the internal matching capacitor Cs; the first terminal of the internal matching capacitor Cs is coupled to the second terminal of the first switch K1, and the second terminal of the internal matching capacitor Cs is grounded; the first terminal of the first switch K1 is coupled to the second terminal of the first equivalent resistor Rs, and the first terminal of the first equivalent resistor Rs is coupled to the operating power supply VDD; the third switch K3 and the second equivalent resistor Rf are connected in series between the first terminal of the internal matching capacitor Cs and the first terminal of the internal adjustment capacitor Cf; the sixth switch K6 is connected in parallel with the internal adjustment capacitor Cf; the fifth switch K5 is connected in series between the second terminal of the internal adjustment capacitor Cf and the analog-to-digital converter ADC. The touch detection circuit is configured to perform the following operations: a. Keep the first terminal voltage Vcm of the internal regulating capacitor Cf constant, and the charging or discharging action of the internal regulating capacitor Cf is manifested as a change in the second terminal voltage of the internal regulating capacitor Cf; b. By charging the internal matching capacitor Cs, the effect of the extended charging time caused by the external anti-interference resistor Rx with a large series resistance value of the equivalent capacitance Cx of the touch channel is eliminated. The external anti-interference resistor Rx with a large resistance value refers to the external anti-interference resistor Rx with a resistance value exceeding a preset threshold. c. During the high-efficiency charging and discharging time of the equivalent capacitance Cx of the touch channel, the internal matching capacitor Cs discharges the equivalent capacitance Cx of the touch channel, reducing the time required for the equivalent capacitance Cx of the touch channel to charge or the internal matching capacitor Cs to discharge when the external anti-interference resistor Rx is large. d. Based on the voltage relationship between the internal matching capacitor Cs and the first terminal voltage Vcm of the internal regulating capacitor Cf, the internal matching capacitor Cs charges or discharges the internal regulating capacitor Cf; e. The voltage change at the second terminal of the internal regulating capacitor Cf, caused by the change in the charge of the internal regulating capacitor Cf, is converted into a digital touch signal through the analog-to-digital converter ADC. f. By comparing the touch digits when a finger is pressed and when no finger is pressed, it can be determined whether a button has been pressed. g. When the difference in the digital touch value obtained during process f is less than a preset value, processes b to d are executed repeatedly. The change in charge of the internal regulating capacitor Cf is integrated before action e is performed, thereby increasing the amount of finger touch change, reducing the influence of environmental noise, and improving the touch anti-interference capability.

2. The touch detection circuit as described in claim 1, characterized in that, The equivalent capacitance Cx of the touch channel only participates in the scanning during process c. All other processes are internal chip operations and are unrelated to the outside world. This can greatly reduce the impact of the external environment and interference on the touch and improve the touch anti-interference capability.

3. The touch detection circuit as described in claim 1, characterized in that, The first equivalent series resistance Rs is configured to be less than a preset value, so that the internal matching capacitor Cs is quickly charged during process b, thereby eliminating the impact of the increased charging time caused by the external anti-interference resistor Rx increasing exponentially, and reducing the impact of external interference entering the chip through the touch channel pin on touch scanning.

4. The touch detection circuit as described in claim 1, characterized in that, The second equivalent resistance Rf is configured to be less than a preset value, so that the voltage of the internal matching capacitor Cs quickly reaches the first terminal voltage Vcm of the internal regulating capacitor Cf during the d process, thereby eliminating the impact of the significant increase in charging time caused by the external anti-interference resistor Rx increasing exponentially; at the same time, it also reduces the impact of external interference entering the chip through the touch channel pin and affecting touch scanning.

5. The touch detection circuit as described in claim 1, characterized in that, By utilizing the high-efficiency phase of capacitor charging and discharging, the time required for the equivalent capacitance Cx of the touch channel to charge or the internal matching capacitor Cs to discharge when the external anti-interference resistor Rx is large is reduced, thereby lowering the touch scanning time.

6. A touch detection circuit, characterized in that, include: The circuit includes a touch channel equivalent capacitance Cx, an external anti-interference resistor Rx, an internal matching capacitor Cs, a first equivalent resistance Rs, a second equivalent resistance Rf, an internal adjustment capacitor Cf, an analog-to-digital converter (ADC), a first switch K1, a second switch K2, a third switch K3, a fourth switch K4, a fifth switch K5, and a sixth switch K6. The first equivalent resistance Rs is the equivalent series resistance of the internal matching capacitor Cs to ground, and the second equivalent resistance Rf is the equivalent resistance between Cf and Cs. The first terminal of the equivalent capacitance Cx of the touch channel is grounded; the second terminal of the equivalent capacitance Cx is coupled to the first terminal of the external anti-interference resistor Rx; the second terminal of the external anti-interference resistor Rx is coupled to the first terminal of the fourth switch K4; the second terminal of the fourth switch K4 is connected to the first reference voltage Vref1; the first terminal of the second switch K2 is coupled to the first terminal of the fourth switch K4; the second terminal of the second switch K2 is coupled to the first terminal of the internal matching capacitor Cs; the first terminal of the internal matching capacitor Cs is coupled to the second terminal of the first switch K1; the second terminal of the internal matching capacitor Cs is connected to the second reference voltage Vref2; the first terminal of the first switch K1 is coupled to the second terminal of the first equivalent resistor Rs; the first terminal of the first equivalent resistor Rs is coupled to ground; the third switch K3 and the second equivalent resistor Rf are connected in series between the first terminal of the internal matching capacitor Cs and the first terminal of the internal adjustment capacitor Cf; the sixth switch K6 is connected in parallel with the internal adjustment capacitor Cf; the fifth switch K5 is connected in series between the second terminal of the internal adjustment capacitor Cf and the analog-to-digital converter (ADC). The touch detection circuit is configured to perform the following actions: a. Keep the first terminal voltage Vcm of the internal regulating capacitor Cf constant, and the charging or discharging action of the internal regulating capacitor Cf is manifested as a change in the second terminal voltage of the internal regulating capacitor Cf; b. During the high-efficiency charging time of the equivalent capacitance Cx of the touch channel, the first reference voltage Vref1 charges the equivalent capacitance Cx of the touch channel to reduce the charging time required for the equivalent capacitance Cx of the touch channel when the external anti-interference resistor Rx is large; wherein, the external anti-interference resistor Rx being large means that the resistance value of the external anti-interference resistor Rx exceeds a preset threshold. c. During the high-efficiency charging and discharging time of the equivalent capacitance Cx of the touch channel, the internal matching capacitor Cs discharges the equivalent capacitance Cx of the touch channel or the equivalent capacitance Cx of the touch channel discharges the internal matching capacitor Cs, thereby reducing the time required for the equivalent capacitance Cx of the touch channel or the internal matching capacitor Cs to charge when the external anti-interference resistor Rx is large. d. Based on the voltage relationship between the internal matching capacitor Cs and the first terminal voltage Vcm of the internal regulating capacitor Cf, the internal matching capacitor Cs charges or discharges the internal regulating capacitor Cf; e. The voltage change at the second terminal of the internal regulating capacitor Cf, caused by the change in the charge of the internal regulating capacitor Cf, is converted into a digital touch signal through the analog-to-digital converter ADC. f. By comparing the touch digits when a finger is pressed and when no finger is pressed, it can be determined whether a button has been pressed. g. When the difference in the digital touch value obtained during process f is less than a preset value, processes b to d are executed repeatedly. The change in charge of the internal regulating capacitor Cf is integrated before action e is performed, thereby increasing the amount of finger touch change, reducing the influence of environmental noise, and improving the touch anti-interference capability.

7. The touch detection circuit as described in claim 6, characterized in that, The equivalent capacitance Cx of the touch channel only participates in scanning during processes b and c. The other processes are all internal chip operations and are not related to the outside world. This can reduce the impact of the external environment and interference on the touch and improve the touch anti-interference capability.

8. The touch detection circuit as described in claim 6, characterized in that, By utilizing the high-efficiency phase of capacitor charging and discharging, the time required for the equivalent capacitance Cx of the touch channel or the internal matching capacitor Cs to charge when the external anti-interference resistor Rx is large is reduced, thereby lowering the touch scanning time.

9. The touch detection circuit as described in claim 6, characterized in that, The second equivalent resistance Rf is configured to be less than a preset value, so that the voltage of the internal matching capacitor Cs quickly reaches the first terminal voltage Vcm of the internal regulating capacitor Cf during the d process, thereby eliminating the impact of the significant increase in charging time caused by the external anti-interference resistor Rx increasing exponentially; at the same time, it also reduces the impact of external interference entering the chip through the touch channel pin and affecting touch scanning.

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