Capacitive touch screen detection circuit and control method thereof

Abstract

The present invention discloses a capacitive touch screen detection circuit and a control method thereof, which belongs to the field of capacitive touch screen detection. The detection circuit includes a coding module, a timing detection module, a touch electrode, a switch module, a charge cancellation module, a charge-to-voltage module, a digital converter and a decoding module. The control method of the detection circuit includes the following steps: step one: generating a control timing; step two: detecting whether the control timing is abnormal; step three: controlling the on and off of each touch electrode in the circuit; step four: obtaining an external first charge; step five: redistributing the first charge to obtain a second charge; step six: converting the second charge into a voltage; step seven: converting the above voltage into a digital quantity; step eight: calculating the digital quantity to obtain a capacitance value. The present invention realizes multi-channel capacitance simultaneous detection with a single analog front end (AFE) through orthogonal coding and digital decoding, and further reduces the area of ​​the chip.

Description

Technical Field

[0001] The present invention relates to the field of capacitive touch screen detection, in particular to a capacitive touch screen detection circuit and a control method thereof. Background Art

[0002] Capacitive touch screens have been increasingly used in various electronic equipment fields due to their durability, fast response speed, space saving, and high light transmittance, and are becoming mainstream products in the market. Capacitive touch screens use transparent indium tin oxide (ITO) material to form an electrode array on the surface of a glass substrate. According to different detection principles, capacitive touch screens are divided into self-capacitive touch screens and mutual-capacitive touch screens: self-capacitive touch screens determine the touch position of the touch object on the touch screen by detecting the change in capacitance between the electrode and the ground before and after the touch; mutual-capacitive touch screens determine the touch position of the touch object on the touch screen by detecting the change in capacitance between the two groups of electrodes before and after the touch. That is, self-capacitive touch screens detect touch by detecting the change in capacitance between the electrode and the ground, while mutual-capacitive touch screens detect touch by detecting the change in capacitance between the two electrodes.

[0003] In the detection circuit of the self-capacitive touch screen, the change in capacitance is generally converted into the change in voltage, and the change in voltage is proportional to the change in capacitance. The voltage is converted into a digital quantity by the digital converter (ADC) and then transmitted to the microprocessor (MCU) for subsequent judgment and processing. Generally, in order to improve the signal-to-noise ratio (SNR), this process is repeated many times, and the multiple conversion results are accumulated and averaged. Every 4 accumulations can increase the SNR by 2 times.

[0004] From the working mode of the existing scheme, when there is an application scenario such as a capacitive touch screen where multiple touch electrodes need to be detected, there are only two ways:

[0005] 1. Use time-sharing detection to connect the touch electrodes to the AFE for detection in sequence through a multi-select switch. In order to ensure a sufficiently high SNR, it is necessary to ensure that the detection time of each channel is long enough. When there are more touch electrodes, the total detection time is lengthened, which severely limits the refresh rate.

[0006] 2. Each channel is equipped with an AFE, and all channels are tested simultaneously. Although this solution can also improve the refresh rate, since each channel needs to be equipped with an AFE, the area and power consumption are very high.

[0007] Both of the above methods have certain defects. Therefore, those skilled in the art provide a capacitive touch screen detection circuit and a control method thereof to solve the problems raised in the above background technology. Summary of the invention

[0008] The purpose of the present invention is to provide a capacitive touch screen detection circuit and a control method thereof, which realizes multi-channel capacitance simultaneous detection with a single AFE through orthogonal coding and digital decoding, and further reduces the chip area to solve the problems raised in the above background technology.

[0009] To achieve the above object, the present invention provides the following technical solutions:

[0010] A capacitive touch screen detection circuit, including an encoding module, a timing detection module, a touch electrode, a switch module, a charge cancellation module, a charge-to-voltage module, a digital converter, and a decoding module;

[0011] The encoding module is connected to the timing detection module and is used to generate control timings corresponding to the switch module, the charge compensation module, and the charge-to-voltage conversion module;

[0012] The timing detection module is connected to the switch module, the charge compensation module, and the charge-to-voltage module, and is used to detect whether the control timing generated by the encoding module is abnormal;

[0013] The switch module is connected to the charge compensation module and is used to control the charging and discharging of each touch electrode and the connection and disconnection between the touch electrode and the charge compensation module;

[0014] The touch electrode acquires an external first charge;

[0015] The first charges are redistributed between the touch electrodes and the charge cancellation module, and the charge cancellation module obtains the second charges;

[0016] The charge cancellation module is connected to the charge-to-voltage module, and is used to convert the second charge into a voltage; the charge-to-voltage module is connected to a digital converter, and is used to convert the voltage into a digital value;

[0017] The digital converter is connected to a decoding module, which includes a plurality of output traces configured in a matrix. The capacitance value of each touch electrode can be obtained by calculating the digital quantity according to the timing logic.

[0018] The present invention uses orthogonal coding and digital decoding to achieve simultaneous detection of multi-channel capacitance using a single AFE, and further reduces the chip area. In addition, by detecting whether the control timing generated by the coding module is abnormal, the accuracy of the detection is further improved.

[0019] As a further solution of the present invention, the specific detection process of the timing detection module is as follows:

[0020] S1: Build the detection model and import standard timing parameters;

[0021] S2: Input the control timing output by the encoding module into the detection model for detection. If the detection is qualified, the control timing is judged to be normal, and the control timing is transmitted to the switch module, the charge compensation module, and the charge-to-voltage module; if the detection is unqualified, the control timing is judged to be abnormal, and the next step is entered;

[0022] S3: Send an instruction to the encoding module. After receiving the instruction, the encoding module outputs the control timing again and repeats step S2. If the control timing output three times in a row is abnormal, an alarm is issued.

[0023] The alarm is triggered only when three abnormalities occur, which improves the reliability of the alarm.

[0024] As a further solution of the present invention: the standard timing parameters include the number of standard high levels and the number of standard low levels corresponding to the standard timing.

[0025] The number of standard high levels and the number of standard low levels facilitate comparison with the control timing generated by the encoding module later.

[0026] As a further solution of the present invention, the specific detection process of the detection model is:

[0027] S201: Compare the number of high levels of the control timing with the number of standard high levels. If the two are the same, output parameter P1=0; otherwise, take the absolute value of the difference between the number of high levels and the number of standard high levels, set it as n1, and output parameter P1=0.1*n1;

[0028] S202: Compare the number of low levels of the control timing with the number of standard low levels. If the two are the same, output parameter P2=0; otherwise, take the absolute value of the difference between the number of low levels and the number of standard low levels, set it as n2, and output parameter P2=0.1*n2;

[0029] S203: Let Pi = P1 + P2. If Pi is 0, the output detection is qualified, otherwise the output detection is abnormal.

[0030] The detection process is simple and efficient, and can quickly identify whether the control timing generated by the encoding module is abnormal.

[0031] As a further solution of the present invention: the alarm module is connected to the timing detection module, and is used to issue a graded alarm when the control timing is abnormal three times in a row.

[0032] The graded alarm makes it easy for the staff to understand the abnormal degree of the control timing generated by the encoding module.

[0033] As a further solution of the present invention: the graded alarm is specifically as follows: a preset value Qi is set, if the Pi corresponding to three abnormalities are all greater than Qi, a third-level alarm is issued; if the Pi corresponding to the three abnormalities is greater than Qi twice, a second-level alarm is issued; if the Pi corresponding to the three abnormalities is greater than Qi once, a first-level alarm is issued.

[0034] The staff can set the preset value Qi according to their needs, which is convenient for checking and distinguishing during later inspections.

[0035] As a further solution of the present invention: the alarm module is a display screen, and when an alarm is issued, the abnormal parameter Pi is displayed three times on the display screen, and when a third-level alarm is issued, the display screen frame flashes red light; when the display screen issues a second-level alarm, the display screen frame flashes yellow light; when the display screen issues a first-level alarm, the display screen frame flashes blue light.

[0036] This setting makes it easy for staff to identify the level of the alarm.

[0037] As a further solution of the present invention: the number of sampling pulses in a complete sampling cycle of the sequential logic is equal to the number of the touch electrodes, and when one of the touch electrodes is discharged in sequence according to the sampling pulse signal, the remaining electrodes are charged.

[0038] As a further solution of the present invention: the number of the touch electrodes is four, namely, Ctp1, Ctp2, Ctp3 and Ctp4. When the timing pulse signal is at the first high level, Ctp1, Ctp2, and Ctp3 are charged, and Ctp4 is discharged; when the timing pulse signal is at the second high level, Ctp1, Ctp2, and Ctp4 are charged, and Ctp3 is discharged; when the timing pulse signal is at the third high level, Ctp1, Ctp4, and Ctp3 are charged, and Ctp2 is discharged; when the timing pulse signal is at the fourth high level, Ctp4, Ctp2, and Ctp3 are charged, and Ctp1 is discharged.

[0039] As a further solution of the present invention: the encoding module can reduce low-frequency noise by changing the timing mode to achieve coherent double sampling.

[0040] As a further solution of the present invention: the number of sampling pulses in a complete sampling cycle of the coherent double sampling timing logic is twice the number of the touch electrodes, and when one of the touch electrodes is discharged sequentially according to the sampling pulse signal, the other electrodes are charged, or when one of the electrodes is charged sequentially according to the sampling pulse signal, the other electrodes are discharged, and the two are performed alternately.

[0041] As a further solution of the present invention: the number of the touch electrodes is four, namely, Ctp1, Ctp2, Ctp3 and Ctp4, when the timing pulse signal is at the first high level, Ctp1, Ctp2, Ctp3 are charged, and Ctp4 is discharged; when the timing pulse signal is at the second high level, Ctp1, Ctp2, Ctp3 are discharged, and Ctp4 is charged; when the timing pulse signal is at the third high level, Ctp1, Ctp4, Ctp2 are charged, and Ctp3 is discharged; when the timing pulse signal is at the fourth high level , Ctp1, Ctp4, Ctp2 discharge, and Ctp3 charges; when the timing pulse signal is at the fifth high level, Ctp1, Ctp4, Ctp3 charges, and Ctp2 discharges; when the timing pulse signal is at the sixth high level, Ctp1, Ctp4, Ctp3 discharges, and Ctp2 charges; when the timing pulse signal is at the seventh high level, Ctp2, Ctp4, Ctp3 charges, and Ctp1 discharges; when the timing pulse signal is at the eighth high level, Ctp2, Ctp4, Ctp3 discharges, and Ctp1 charges.

[0042] The control method of the capacitive touch screen detection circuit comprises the following steps:

[0043] Step 1: Generate control timing;

[0044] Step 2: Check whether the control timing is abnormal;

[0045] Step 3: Control the on and off of each touch electrode in the circuit;

[0046] Step 4: Obtaining an external first charge;

[0047] Step 5: redistribute the first charges to obtain second charges;

[0048] Step 6: Convert the second charge into voltage;

[0049] Step 7: Convert the voltage into a digital value according to the timing logic preset by the timing detection module;

[0050] Step 8: Calculate the digital quantity according to the timing logic to obtain the capacitance value of each touch electrode.

[0051] Compared with the prior art, the present invention has the following beneficial effects:

[0052] 1. Through orthogonal coding and digital decoding, a single AFE can be used to realize simultaneous detection of multi-channel capacitors, effectively improving the refresh rate and SNR, reducing the chip area, and reducing the chip operating power consumption; in the process of simultaneous detection, the characteristics of orthogonal coding can also be used to use channel capacitance for charge cancellation, effectively reducing the capacitance of the cancel capacitor, and further reducing the chip area.

[0053] 2. By setting up the timing detection module and building a detection model, it is possible to quickly and effectively detect whether the control timing generated by the encoding module is abnormal, and when an abnormality occurs, a graded alarm is issued according to its severity. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] The disclosure of the present invention is described with reference to the accompanying drawings. It should be understood that the drawings are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. In the accompanying drawings, the same reference numerals are used to refer to the same components. Among them:

[0055] Figure 1 It is a structural schematic diagram of a capacitive touch screen detection circuit according to an embodiment of the present invention;

[0056] Figure 2 is a timing detection flow chart of an embodiment of the present invention;

[0057] Figure 3 is a timing logic diagram of an embodiment of the present invention;

[0058] Figure 4 It is a timing logic diagram of coherent double sampling according to an embodiment of the present invention;

[0059] Figure 5 A schematic diagram of control timing orthogonal coding according to an embodiment of the present invention;

[0060] Figure 6 The figure is a flow chart of a control method of a capacitive touch screen detection circuit according to an embodiment of the present invention. DETAILED DESCRIPTION

[0061] It is easy to understand that according to the technical solution of the present invention, without changing the essential spirit of the present invention, a person skilled in the art can propose a variety of interchangeable structural modes and implementation modes. Therefore, the following specific implementation modes and drawings are only exemplary descriptions of the technical solution of the present invention, and should not be regarded as the whole of the present invention or as a limitation or restriction to the technical solution of the present invention.

[0062] According to one embodiment of the present invention, Figures 1 to 4The capacitive touch screen detection circuit includes an encoding module, a timing detection module, a touch electrode, a switch module, a charge cancellation module, a charge-to-voltage module, a digital converter and a decoding module;

[0063] The encoding module is connected to the timing detection module to generate control timings corresponding to the switch module, the charge compensation module, and the charge-to-voltage conversion module;

[0064] The timing detection module is connected with the switch module, the charge offset module and the charge-to-voltage module to detect whether the control timing generated by the encoding module is abnormal;

[0065] The switch module is connected to the charge compensation module and is used to control the charging and discharging of each touch electrode and the connection and disconnection between the touch electrode and the charge compensation module;

[0066] The touch electrode acquires an external first charge;

[0067] The first charge is redistributed between the touch electrode and the charge compensation module, and the charge compensation module obtains the second charge;

[0068] The charge cancellation module is connected to the charge-to-voltage module and is used to convert the second charge into a voltage;

[0069] The charge-to-voltage module is connected to the digital converter and is used to convert the above voltage into a digital quantity;

[0070] The digital converter is connected to the decoding module, which includes a plurality of output traces configured in a matrix. The capacitance value of each touch electrode can be obtained by calculating the digital quantity according to the timing logic.

[0071] The present invention uses orthogonal coding and digital decoding to achieve simultaneous detection of multi-channel capacitance using a single AFE. Orthogonal coding is a typical coding form with good noise resistance, which can effectively improve the accuracy during detection and further reduce the chip area. In addition, by detecting whether the control timing generated by the coding module is abnormal, the accuracy of the detection is further improved.

[0072] In this embodiment, if Figure 2 As shown, the specific detection process of the timing detection module is:

[0073] S1: Build the detection model and import standard timing parameters;

[0074] S2: Input the control timing output by the encoding module into the detection model for detection. If the detection is qualified, the control timing is judged to be normal, and the control timing is transmitted to the switch module, the charge compensation module, and the charge-to-voltage module; if the detection is unqualified, the control timing is judged to be abnormal, and the next step is entered;

[0075] S3: Send an instruction to the encoding module. After receiving the instruction, the encoding module outputs the control timing again and repeats step S2. If the control timing output three times in a row is abnormal, an alarm is issued.

[0076] The alarm is triggered only when three abnormalities occur, which improves the reliability of the alarm.

[0077] In this embodiment, the standard timing parameters include the number of standard high levels and the number of standard low levels corresponding to the standard timing, which are convenient for comparison with the control timing generated by the encoding module in the later stage.

[0078] In this embodiment, if Figure 2 As shown in the figure, the specific detection process of the detection model is as follows:

[0079] S201: Compare the number of high levels of the control timing with the number of standard high levels. If the two are the same, output parameter P1=0; otherwise, take the absolute value of the difference between the number of high levels and the number of standard high levels, set it as n1, and output parameter P1=0.1*n1;

[0080] S202: Compare the number of low levels of the control timing with the number of standard low levels. If the two are the same, output parameter P2=0; otherwise, take the absolute value of the difference between the number of low levels and the number of standard low levels, set it as n2, and output parameter P2=0.1*n2;

[0081] S203: Let Pi = P1 + P2. If Pi is 0, the output detection is qualified, otherwise the output detection is abnormal.

[0082] The detection process is simple and efficient, and can quickly identify whether the control timing generated by the encoding module is abnormal.

[0083] In this embodiment, the alarm module is connected to the timing detection module, and is used to generate a graded alarm when the control timing is abnormal three times in a row. The graded alarm facilitates the staff to understand the degree of abnormality of the control timing generated by the encoding module.

[0084] In this embodiment, the hierarchical alarm is specifically: a preset value Qi is set, if the Pi corresponding to the three abnormalities are all greater than Qi, a third-level alarm is issued; if the Pi corresponding to the three abnormalities is greater than Qi twice, a second-level alarm is issued; if the Pi corresponding to the three abnormalities is greater than Qi once, a first-level alarm is issued. The staff can set the preset value Qi according to their needs, so that they can check and distinguish it during the later detection.

[0085] In this embodiment: the alarm module is a display screen, and the abnormal parameter Pi is displayed three times on the display screen when an alarm is issued, and when a third-level alarm is issued, the display screen frame flashes red; when the display screen issues a second-level alarm, the display screen frame flashes yellow; when the display screen issues a first-level alarm, the display screen frame flashes blue. This setting makes it easy for staff to identify the level of the alarm.

[0086] In this embodiment: Figure 3 As shown, the number of sampling pulses in a complete sampling cycle of the sequential logic is equal to the number of touch electrodes, and when one of the touch electrodes is discharged in sequence according to the sampling pulse signal, the remaining electrodes are charged.

[0087] In this embodiment: Figure 5 As shown, there are four touch electrodes, namely, Ctp1, Ctp2, Ctp3 and Ctp4, and 4 samples are collected in each sampling cycle. The digital frequency of the calculated sampling sequence is π / 2, that is, the phase difference between every two sampling pulses is 90 degrees. Therefore, it is convenient to orthogonally encode the capacitance value of the touch electrode. When the timing pulse signal is at the first high level, Ctp1, Ctp2, and Ctp3 are charged, and Ctp4 is discharged; when the timing pulse signal is at the second high level, Ctp1, Ctp2, and Ctp4 are charged, and Ctp3 is discharged; when the timing pulse signal is at the third high level, Ctp1, Ctp4, and Ctp3 are charged, and Ctp2 is discharged; when the timing pulse signal is at the fourth high level, Ctp4, Ctp2, and Ctp3 are charged, and Ctp1 is discharged.

[0088] In this embodiment: the encoding module can reduce low-frequency noise by changing the timing mode to achieve coherent double sampling.

[0089] In this embodiment: Figure 4 As shown, in the timing logic of coherent double sampling, the number of sampling pulses in a complete sampling cycle is twice the number of touch electrodes, and when one of the touch electrodes is discharged in sequence according to the sampling pulse signal, the other electrodes are charged, or when one of the electrodes is charged in sequence according to the sampling pulse signal, the other electrodes are discharged, and the two are performed alternately.

[0090] In this embodiment, there are four touch electrodes, namely, Ctp1, Ctp2, Ctp3 and Ctp4. When the timing pulse signal is at the first high level, Ctp1, Ctp2 and Ctp3 are charged, and Ctp4 is discharged; when the timing pulse signal is at the second high level, Ctp1, Ctp2 and Ctp3 are discharged, and Ctp4 is charged; when the timing pulse signal is at the third high level, Ctp1, Ctp4 and Ctp2 are charged, and Ctp3 is discharged; when the timing pulse signal is at the fourth high level, Ctp 1. Ctp4 and Ctp2 discharge, and Ctp3 charges; when the timing pulse signal is at the fifth high level, Ctp1, Ctp4, and Ctp3 charge, and Ctp2 discharges; when the timing pulse signal is at the sixth high level, Ctp1, Ctp4, and Ctp3 discharge, and Ctp2 charges; when the timing pulse signal is at the seventh high level, Ctp2, Ctp4, and Ctp3 charge, and Ctp1 discharges; when the timing pulse signal is at the eighth high level, Ctp2, Ctp4, and Ctp3 discharge, and Ctp1 charges.

[0091] See also Figures 3 to 6 The present invention also discloses a control method for a capacitive touch screen detection circuit, comprising the following steps:

[0092] Step 1: Generate control timing;

[0093] Step 2: Check whether the control timing is abnormal, specifically:

[0094] Build a detection model and import standard timing parameters;

[0095] The control timing output by the encoding module is input into the detection model for detection. If the detection is qualified, the control timing is judged to be normal, and the control timing is transmitted to the switch module, the charge compensation module, and the charge-to-voltage module; if the detection is unqualified, the control timing is judged to be abnormal, and the next step is entered;

[0096] Send a command to the encoding module, and the encoding module outputs the control timing again after receiving the command, and repeats step S2; if the control timing output three times in a row is abnormal, an alarm is issued;

[0097] Step 3: Control the on and off of each touch electrode in the circuit;

[0098] Step 4: Obtain the external first charge, as follows:

[0099] At t0-t1, Cf is reset, the touch electrodes Ctp1, Ctp2, and Ctp3 are charged, and Ctp4 and the charge compensation capacitor Cc are discharged. The charges on each capacitor are:

[0100] Q Ctp1 =V DD Ctp1

[0101] Q Ctp2 =V DD C tp2

[0102] Q Ctp3 =V DD C tp3

[0103] Q Ctp4 =Q Cc =Q Cf =0

[0104] Wherein, VDD refers to the power supply voltage;

[0105] Step 5: redistribute the first charge between the touch electrode and the charge compensation module, and the charge compensation module obtains the second charge, as follows:

[0106] At time t2-t3, the charge of capacitor Cc is offset by that of Ctp1, Ctp2, Ctp3, and Ctp4, which is essentially a charge redistribution among Cc, Ctp1, Ctp2, Ctp3, and Ctp4.

[0107] Step 6: Convert the excess charge into voltage as follows:

[0108] At t4-t5, the excess charge is converted into voltage to facilitate ADC processing. In essence, the charge is redistributed among Cc, Ctp1, Ctp2, Ctp3, Ctp4, and Cf. According to the law of charge conservation, we have:

[0109] Q total，分配前 =Q total，分配后

[0110] V DD C tp1 +V DD C tp2 +V DD C tp3

[0111] =V CM (C tp1 +C tp2 +C tp3 +C tp4 +C c )+(V CM -V OUT1 )C f

[0112] The expression for VOUT can be calculated as:

[0113]

[0114] Set VCM = VDD / 2, and VOUT can be rewritten as:

[0115]

[0116] Step 7: Convert the voltage into a digital value according to the timing logic preset by the timing detection module, as follows:

[0117] Using the same method, VOUT2 at t10-t11, VOUT3 at t16-t17, and VOUT4 at t22-t23 can be written as follows:

[0118]

[0119]

[0120]

[0121] In the above formula, only Ctp1, Ctp2, Ctp3, and Ctp4 change, and the others are fixed. Therefore, in order to facilitate theoretical derivation, these fixed quantities are considered as fixed gains for normalization or fixed offsets for elimination after being converted into digital quantities by ADC. DOUT1~4 can be expressed as:

[0122] D OUT1 =C tp1 +C tp2 +C tp3 -C tp4

[0123] D OUT2 =C tp1 +C tp2 -C tp3 +C tp4

[0124] D OUT3 =C tp1 -C tp2 +C tp3 +C tp4

[0125] D OUT4 =-C tp1 +C tp2 +C tp3 +C tp4

[0126] Written in matrix form:

[0127]

[0128] Step 8: The capacitance value of each touch electrode can be obtained by calculating the digital quantity according to the sequential logic, as follows:

[0129] The decoding module generates a decoding matrix H according to the sequential logic -1

[0130]

[0131] Multiply by DOUT matrix

[0132]

[0133] Finally, the capacitance value of each touch electrode is obtained.

[0134] In this embodiment, the encoding module can reduce low-frequency noise by changing the timing mode to achieve coherent double sampling, such as Figure 4 As shown, the analysis method is similar to the above, the difference is that the data of every two ADCs need to be subtracted: the ADC data converted at t4~t5 is subtracted from the ADC data converted at t10~t11 to obtain DOUT1; the ADC data converted at t16~t17 is subtracted from the ADC data converted at t22~t23 to obtain DOUT2; the ADC data converted at t28~t29 is subtracted from the ADC data converted at t34~t35 to obtain DOUT3; the ADC data converted at t40~t41 is subtracted from the ADC data converted at t46~t47 to obtain DOUT4.

[0135] The present invention uses orthogonal coding and digital decoding to achieve multi-channel capacitor simultaneous detection with a single AFE, effectively improving the refresh rate and SNR, and reducing the chip area and chip operation power consumption; in the process of simultaneous detection, the characteristics of orthogonal coding can also be used to use channel capacitance to cancel the charge, effectively reducing the capacitance of the cancel capacitor, and further reducing the chip area. In addition, by setting the timing detection module and constructing a detection model, it is possible to quickly and effectively detect whether the control timing generated by the encoding module is abnormal, and when an abnormality occurs, a graded alarm is issued according to its severity.

[0136] What is described above is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. Capacitive touch screen detection circuit, characterized in that: It includes an encoding module, a timing detection module, a touch electrode, a switch module, a charge cancellation module, a charge-to-voltage module, a digital converter and a decoding module; The encoding module is connected to the timing detection module and is used to generate control timings corresponding to the switch module, the charge compensation module, and the charge-to-voltage conversion module; The timing detection module is connected to the switch module, the charge compensation module, and the charge-to-voltage module, and is used to detect whether the control timing generated by the encoding module is abnormal; The switch module is connected to the charge compensation module and is used to control the charging and discharging of each touch electrode and the connection and disconnection between the touch electrode and the charge compensation module; The touch electrode acquires an external first charge; The first charges are redistributed between the touch electrodes and the charge cancellation module, and the charge cancellation module obtains second charges; The charge cancellation module is connected to the charge-to-voltage module and is used to convert the second charge into a voltage; The charge-to-voltage module is connected to a digital converter and is used to convert the voltage into a digital value; The digital converter is connected to a decoding module, which includes a plurality of output traces configured in a matrix. The capacitance value of each touch electrode can be obtained by calculating the digital quantity according to the timing logic.

2. The capacitive touch screen detection circuit according to claim 1, characterized in that: The specific detection process of the timing detection module is as follows: S1: Build the detection model and import standard timing parameters; S2: Input the control timing output by the encoding module into the detection model for detection. If the detection is qualified, the control timing is judged to be normal, and the control timing is transmitted to the switch module, the charge compensation module, and the charge-to-voltage module; if the detection is unqualified, the control timing is judged to be abnormal, and the next step is entered; S3: Send an instruction to the encoding module. After receiving the instruction, the encoding module outputs the control timing again and repeats step S2. If the control timing output three times in a row is abnormal, an alarm is issued.

3. The capacitive touch screen detection circuit according to claim 2, characterized in that: The standard timing parameters include the number of standard high levels and the number of standard low levels corresponding to the standard timing.

4. The capacitive touch screen detection circuit according to claim 3, characterized in that: The specific detection process of the detection model is as follows: S201: Compare the number of high levels of the control timing with the number of standard high levels. If the two are the same, output parameter P1=0; otherwise, take the absolute value of the difference between the number of high levels and the number of standard high levels, set it as n1, and output parameter P1=0.1*n1; S202: Compare the number of low levels of the control timing with the number of standard low levels. If the two are the same, output parameter P2=0; otherwise, take the absolute value of the difference between the number of low levels and the number of standard low levels, set it as n2, and output parameter P2=0.1*n2; S203: Let Pi = P1 + P2. If Pi is 0, the output detection is qualified, otherwise the output detection is abnormal.

5. The capacitive touch screen detection circuit according to claim 4, characterized in that: It also includes an alarm module, which is connected to the timing detection module and is used to issue a graded alarm when the control timing is abnormal three times in a row.

6. The capacitive touch screen detection circuit according to claim 5, characterized in that: The hierarchical alarm is specifically as follows: a preset value Qi is set, and if the Pi corresponding to three abnormalities are all greater than Qi, a third-level alarm is issued; if the Pi corresponding to three abnormalities is greater than Qi twice, a second-level alarm is issued; if the Pi corresponding to three abnormalities is greater than Qi once, a first-level alarm is issued.

7. The capacitive touch screen detection circuit according to claim 6, characterized in that: The alarm module is a display screen. When an alarm is triggered, the abnormal parameter Pi is displayed three times on the display screen. When a third-level alarm is triggered, the display screen frame flashes red; when a second-level alarm is triggered, the display screen frame flashes yellow; when a first-level alarm is triggered, the display screen frame flashes blue.

8. The capacitive touch screen detection circuit according to claim 1, characterized in that: The number of sampling pulses in a complete sampling cycle of the sequential logic is equal to the number of the touch electrodes, and when one of the touch electrodes is discharged in sequence according to the sampling pulse signal, the remaining electrodes are charged.

9. The capacitive touch screen detection circuit according to claim 8, characterized in that: The number of touch electrodes is four, namely, Ctp1, Ctp2, Ctp3 and Ctp4. When the timing pulse signal is at the first high level, Ctp1, Ctp2, and Ctp3 are charged, and Ctp4 is discharged; when the timing pulse signal is at the second high level, Ctp1, Ctp2, and Ctp4 are charged, and Ctp3 is discharged; when the timing pulse signal is at the third high level, Ctp1, Ctp4, and Ctp3 are charged, and Ctp2 is discharged; when the timing pulse signal is at the fourth high level, Ctp4, Ctp2, and Ctp3 are charged, and Ctp1 is discharged.

10. The capacitive touch screen detection circuit according to claim 1, characterized in that: The encoding module can reduce low-frequency noise by changing the timing mode and thus realizing coherent double sampling.

11. The capacitive touch screen detection circuit according to claim 10, characterized in that: The number of sampling pulses in a complete sampling cycle of the coherent double sampling timing logic is twice the number of the touch electrodes, and when one of the touch electrodes is discharged in sequence according to the sampling pulse signal, the other electrodes are charged, or when one of the electrodes is charged in sequence according to the sampling pulse signal, the other electrodes are discharged, and the two are performed alternately.

12. The capacitive touch screen detection circuit according to claim 11, characterized in that: The number of the touch electrodes is four, namely, Ctp1, Ctp2, Ctp3 and Ctp4. When the timing pulse signal is at the first high level, Ctp1, Ctp2, and Ctp3 are charged, and Ctp4 is discharged; when the timing pulse signal is at the second high level, Ctp1, Ctp2, and Ctp3 are discharged, and Ctp4 is charged; when the timing pulse signal is at the third high level, Ctp1, Ctp4, and Ctp2 are charged, and Ctp3 is discharged; when the timing pulse signal is at the fourth high level, Ctp1, Ctp4 and Ctp2 discharge, and Ctp3 charges; when the timing pulse signal is at the fifth high level, Ctp1, Ctp4, and Ctp3 charge, and Ctp2 discharges; when the timing pulse signal is at the sixth high level, Ctp1, Ctp4, and Ctp3 discharge, and Ctp2 charges; when the timing pulse signal is at the seventh high level, Ctp2, Ctp4, and Ctp3 charge, and Ctp1 discharges; when the timing pulse signal is at the eighth high level, Ctp2, Ctp4, and Ctp3 discharge, and Ctp1 charges.

13. A control method for a capacitive touch screen detection circuit as claimed in any one of claims 1 to 12, characterized in that: The following steps are involved: Step 1: Generate control timing; Step 2: Check whether the control timing is abnormal; Step 3: Control the on and off of each touch electrode in the circuit; Step 4: Obtaining an external first charge; Step 5: redistribute the first charges to obtain second charges; Step 6: Convert the second charge into voltage; Step 7: Convert the voltage into a digital value according to the timing logic preset by the timing detection module; Step 8: Calculate the digital quantity according to the timing logic to obtain the capacitance value of each touch electrode.

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