CN113064524B - Touch detection system and method and display module - Google Patents
Touch detection system and method and display module Download PDFInfo
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- CN113064524B CN113064524B CN202110396883.2A CN202110396883A CN113064524B CN 113064524 B CN113064524 B CN 113064524B CN 202110396883 A CN202110396883 A CN 202110396883A CN 113064524 B CN113064524 B CN 113064524B
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
- G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
- G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
- G06F3/041—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
- G06F3/0416—Control or interface arrangements specially adapted for digitisers
- G06F3/04166—Details of scanning methods, e.g. sampling time, grouping of sub areas or time sharing with display driving
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F1/00—Details not covered by groups G06F3/00 - G06F13/00 and G06F21/00
- G06F1/26—Power supply means, e.g. regulation thereof
- G06F1/32—Means for saving power
- G06F1/3203—Power management, i.e. event-based initiation of a power-saving mode
- G06F1/3234—Power saving characterised by the action undertaken
- G06F1/325—Power saving in peripheral device
- G06F1/3262—Power saving in digitizer or tablet
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
- G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
- G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
- G06F3/041—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
- G06F3/044—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means by capacitive means
Abstract
The invention belongs to the field of touch detection, and particularly discloses a touch detection system and a method thereof and a display module, wherein the touch detection system comprises a sending end TX, a receiving end RX, an amplifying unit, an analog-to-digital conversion unit, a digital end and a time sequence control unit; the transmitting end TX is used for transmitting a square wave signal; the receiving terminal RX is used for receiving the square wave signal sent by the sending terminal TX; the receiving terminal RX is connected with the amplifying unit, and the amplifying unit is used for amplifying signals received by the receiving terminal RX; the analog-to-digital conversion unit is used for receiving the amplified voltage and outputting a conversion result; the digital end is used for receiving the conversion result and carrying out subsequent judgment and processing; the time sequence control unit is used for controlling the working time sequence of the amplifying unit. By using the touch detection system provided by the invention, the scanning time and the power consumption loss of the system can be reduced on the premise of ensuring the finger detection precision.
Description
Technical Field
The invention belongs to the technical field of touch detection, and particularly discloses a touch detection system and method and a display module.
Background
With the continuous progress of the times, especially the continuous progress of intelligent equipment, people put higher requirements on the precision and timeliness of touch detection. In the prior art, the mutual capacitance type touch detection technology is widely applied to various application fields. Mutual capacitance touch detection requires a group of signal transmitting terminals TX for signal transmission and another group of signal receiving terminals RX for signal reception. Because a parasitic capacitor CM exists between the signal sending terminal TX and the signal receiving terminal RX, the signal quantity received by the RX signal receiving terminal always maintains a stable value, and when a finger touches the signal, the capacitance value of the parasitic capacitor CM is reduced, so that the signal quantity received by the RX signal receiving terminal RX is changed, and when the signal variation exceeds a certain threshold, it is determined that the finger touches the signal.
However, the capacitance variation of the parasitic capacitor CM is usually smaller when the finger touches the cover plate, and the capacitance variation of the parasitic capacitor CM is smaller when the cover plate is thicker, so that the variation of the received moral signal at the signal receiving end is also reduced, thereby increasing the difficulty and accuracy of touch detection.
The principle of the conventional mutual capacitance type touch detection is that two sets of signal input ends TX and signal output ends RX which are crossed in the forward direction are used for detecting finger touch, and when the touch detection is started, the finger touch is detected. TX may sequentially transmit a square wave signal, RX may detect the signal transmitted by TX in real time, and determine whether a finger touches the signal according to the magnitude of the detected semaphore, fig. 1 shows an architecture schematic diagram of a conventional mutual capacitance type touch detection, as shown in fig. 1, n TX sequentially transmit a square wave signal, m RX simultaneously perform signal acquisition, where a parasitic capacitance between TX1 and RX1 is named as CM11, a parasitic capacitance between TX1 and RX2 is named as CM12, and so on. n TX and m RX form n m intersection points on the touch screen, m RX acquires signals simultaneously, when no finger touches, the signal quantity acquired by m RX always keeps a fixed value, namely, the signal quantity acquired for multiple times has too large difference, and when the finger touches, for example, at the intersection position of TX1 and RX2, the capacity value of CM12 is reduced due to the finger touch, so that after TX1 generates a square wave signal, the signal quantity received by RX2 is smaller than that received without the finger touch, and thus the signal quantity difference is generated.
The conventional touch mutual capacitance detection adopts a bilateral sampling detection mode to process signals, and fig. 2 shows an architecture diagram of the conventional touch mutual capacitance detection. As shown in fig. 2, CM is a parasitic capacitance between TX and RX, CMB is a BASE capacitance used for compensating the CM capacitance internally, and the capacitance of CMB is usually adjustable, in practical application, the capacitance of CMB needs to be adjusted to be equivalent to the capacitance of CM capacitance, and the detection principle of the conventional capacitance is as follows:
when mutual capacitance detection is started, the TX continuously sends square wave signals, the RX receives the square wave signals transmitted by the TX, VOUT voltage is generated through subsequent circuit processing, then an analog-to-digital conversion unit performs analog-to-digital conversion on the VOUT voltage, and corresponding conversion code values are generated and transmitted to a digital terminal for subsequent judgment and processing. The conventional mutual capacitance detection usually adopts a bilateral sampling detection mode, and the corresponding timing control diagrams thereof are shown in fig. 3 and fig. 4. The voltage change of RX without finger touch is shown in fig. 3. As shown in fig. 3, when there is no finger touch, in a scanning period of a TX, the analog-to-digital conversion unit samples VOUT voltage twice, the sampled voltages are positive edge sampled voltage VOUT1 and negative edge sampled voltage VOUT2, the analog-to-digital conversion unit converts two analog signals into CODE1 and CODE2, and then performs a difference between the two sets of digital CODE values at the digital end to obtain Δ CODE and store the Δ CODE, and when the signal sampling is repeated N times, the analog-to-digital conversion unit also repeats data processing N times, so as to obtain N times of summation value N × CODE. As shown in fig. 4, when a finger touches, in a TX period, the positive edge sampling voltage changes from VOUT1 to VOUT1 ', and the negative edge sampling voltage changes from VOUT2 to VOUT2 ', so that after being processed by the analog-to-digital conversion unit, the two analog signals are converted into two corresponding sets of digital CODE values CODE1 ' and CODE2 ', and then the two sets of digital CODE values are subtracted at the digital end to obtain Δ CODE ' for storage. After the signal sampling is repeated N times, the analog-to-digital conversion unit also repeats the data conversion N times, so that the summation value N × Δ CODE' can be obtained N times. When N ([ delta ] CODE' - [ delta ] CODE) is greater than a set detection threshold, it is determined that a finger touches, and otherwise, it is determined that no finger touches.
The conventional mutual capacitance detection method needs to sample the VOUT voltage for multiple times, and the difference between sampled positive edge data and sampled negative edge data needs to be processed at a digital terminal each time. When the capacitance value of the capacitor of the CM capacitor caused by finger touch changes slightly, the variation of the corresponding VOUT voltage correspondingly becomes smaller, and thus, the single code value difference after analog-to-digital processing also becomes smaller. Therefore, in order to improve the detection accuracy, when the capacitance variation of the CM capacitor caused by the finger touch is small, especially under the application condition of the back cover plate, the conventional mutual capacitance detection method needs to increase the sampling number N of the VOUT voltage, so as to amplify the difference of N × Δ CODE' - Δ CODE to correctly determine whether the finger touches, which undoubtedly increases the scanning time and power loss of the system.
In order to solve the problem, a new mutual capacitance detection architecture is urgently needed, and the scanning time and the power consumption loss of a system can be reduced on the premise of ensuring the finger detection precision.
Disclosure of Invention
The invention discloses a touch detection system, which comprises a sending end TX, a receiving end RX, an amplifying unit, an analog-to-digital conversion unit, a digital end and a time sequence control unit, wherein the sending end TX is connected with the receiving end RX;
the transmitting end TX is used for transmitting a square wave signal;
the receiving terminal RX is used for receiving the square wave signal sent by the sending terminal TX;
the receiving terminal RX is connected with the amplifying unit, and the amplifying unit is used for amplifying signals received by the receiving terminal RX;
the analog-to-digital conversion unit is used for receiving the amplified voltage and outputting a conversion result;
the digital end is used for receiving the conversion result and carrying out subsequent judgment and processing;
the time sequence control unit is used for controlling the working time sequence of the amplifying unit.
Further, a parasitic capacitance CM exists between the transmitting end TX and the receiving end RX, and a capacitance value of the parasitic capacitance changes when a finger touch is detected.
Further, the amplifying unit includes a first amplifying unit, a second amplifying unit, and a third amplifying unit, the first amplifying unit processes the signal received by the receiving terminal RX to generate a voltage V1, and the second amplifying unit and the third amplifying unit perform subsequent processing on the voltage V1 under the control of the timing control unit to generate a voltage V3.
Further, the voltage V3 has a value equal to (V2-V1) × (R2/R1) + V1;
wherein R2 is an adjustable resistor, and R1 is a constant value resistor.
Further, the first amplifying unit comprises a first operational amplifier OP1, the second amplifying unit comprises a second operational amplifier OP2, and the third amplifying unit comprises a third operational amplifier OP3;
the negative input end of the first operational amplifier OP1 is connected with the output end of the receiving end RX, the reference voltage VREF is input to the positive input end of the first operational amplifier OP1, and the output end of the first operational amplifier OP1 outputs the voltage V1;
the positive input end of the second operational amplifier OP2 is connected with the output end of the first operational amplifier OP1, a first switch P1 is arranged in the connecting line, the reference voltage VREF is input into the positive input end of the second operational amplifier OP2, and whether the reference voltage VREF is connected or not is controlled by the second switch P2;
the output end of the first operational amplifier OP1 is further connected with the negative input end of the third operational amplifier OP3, a resistor R1 is connected in series between the connections, the negative input end and the output end of the second operational amplifier OP2 are short-circuited, the output end of the second operational amplifier OP2 outputs a voltage V2, the output end of the second operational amplifier OP2 is connected with the positive input end of the third operational amplifier OP3 and is connected in series with a resistor R1, and an adjustable capacitor R2 is connected in series between the negative input end and the output end of the third operational amplifier OP3; the output end of the third operational amplifier OP3 outputs a voltage V3, and is connected to the analog-to-digital conversion unit ADC.
Further, in the case of no finger touch, the control logic of the timing control unit is as follows:
v1= V2= V3= VREF at time t1;
at the time t2, the voltage of V1 changes from VREF to generate a corresponding positive edge voltage, and the voltages of V2 and V3 change along with the voltage of V1;
at the time of t3, the voltage of V1 changes to VOUT1, and the voltage of V2 and V3 changes to VOUT1 along with the voltage of V1;
at time t4, the voltage V1 is reset to VREF again, the voltage V2 continues to maintain the voltage VOUT1, and the voltage V3 is maintained at an intermediate voltage value (VOUT 1-VREF) × (R2/R1) + VREF;
at the time of t5, the voltage V1 continuously changes from the voltage VREF to generate a corresponding negative edge voltage, the voltage V2 continuously keeps the voltage VOUT1, and the voltage V3 continuously increases along with the gradual decrease of the voltage V1;
the V1 voltage changes to VOUT2 at the time of t6, the V2 voltage keeps the VOUT1 voltage, the V3 voltage changes to (VOUT 1-VOUT 2) × (R2/R1) + VOUT1, at the moment, the ADC _ SH samples and keeps the V3 voltage at the time of t6, then the ADC starts analog-to-digital conversion, the voltage value is converted into a corresponding digital CODE value CODE, and after the signal sampling is repeated for N times, the ADC also correspondingly repeats data processing for N times, so that an accumulated value N × CODE of the N times can be obtained;
at the time t7, the voltage V1 is reset to VREF again, the voltage V2 is also reset to VREF again, and the voltage V3 is also reset to the VREF again;
keeping the state of t7 at the time t 8;
the TX scan of the next cycle starts again after time t9, and the cycle is repeated.
Further, in the case of finger touch, the control logic of the timing control unit is as follows:
v1= V2= V3= VREF at time t1;
at the time t2, the voltage of V1 changes from VREF to generate a corresponding positive edge voltage, and the voltages of V2 and V3 change along with the voltage of V1;
at the time of t3, the voltage of V1 changes to VOUT1 ', and the voltage of V2 and V3 changes to VOUT 1' along with the voltage of V1;
at time t4, the voltage V1 is reset to VREF again, the voltage V2 continues to maintain the voltage VOUT1 ', and the voltage V3 is maintained at an intermediate voltage value (VOUT 1' -VREF) × (R2/R1) + VREF;
at the time of t5, the voltage V1 continuously changes from the voltage VREF to generate a corresponding negative edge voltage, the voltage V2 continuously keeps the voltage VOUT 1', and the voltage V3 continuously increases along with the gradual reduction of the voltage V1;
when the voltage V1 at the time of t6 changes to VOUT2 ', the voltage V2 keeps on keeping VOUT 1', the voltage V3 changes to (VOUT 1 '-VOUT 2') × (R2/R1) + VOUT1 ', at this time, ADC _ SH samples and keeps the voltage V3 at the time of t6, then ADC starts analog-to-digital conversion, the voltage value is converted into a corresponding digital CODE value CODE', when the signal sampling is repeated N times, the ADC also correspondingly repeats data processing N times, thus N times of accumulation value N × CODE 'can be obtained, when the value N × (CODE' -CODE) is more than a set detection threshold value, the finger touch is judged, otherwise, no finger touch is judged;
at the time t7, the voltage V1 is reset to VREF again, the voltage V2 is also reset to VREF again, and the voltage V3 is also reset to the VREF again;
keeping the state of t7 at the time t 8;
the TX scanning of the next period starts again after the time t9, and the cycle is repeated.
Further, the invention also discloses a control method of the touch detection system, and the sensitivity of the touch detection is adjusted by adjusting the resistance value of the adjustable resistor R2.
Furthermore, the invention also discloses a display module, which comprises the touch detection system and a touch display panel, wherein the parasitic capacitance CM of the touch detection system is uniformly distributed below the touch display panel, and the digital end is connected with the touch display panel.
The invention has the advantages that: according to the invention, by amplifying the signal received by the receiving terminal RX, the situation that repeated operation is required for ensuring the detection accuracy can be effectively reduced, the power consumption of the system is effectively reduced and the scanning time is reduced on the premise of ensuring the accuracy.
Drawings
FIG. 1 illustrates an architectural diagram of mutual capacitance touch detection;
FIG. 2 is a diagram illustrating the architecture of a conventional mutual capacitance detection touch test;
fig. 3 shows the voltage variation of RX when no finger touches the capacitive touch sensing system in the prior art;
fig. 4 shows the voltage variation of RX when a finger touches in a mutual capacitance touch detection system in the prior art;
FIG. 5 is a diagram illustrating a mutual capacitance detection circuit architecture in an embodiment of the present invention;
FIG. 6 is a diagram showing a timing diagram of voltage change when there is no finger touch in the embodiment of the present invention;
FIG. 7 is a diagram illustrating a timing diagram of voltage variation when a finger touches the touch panel according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, belong to the protection scope of the present invention.
The invention discloses a touch detection system which comprises a sending end TX, a receiving end RX, an amplifying unit, an analog-to-digital conversion unit, a digital end and a time sequence control unit. The transmitting terminal TX is configured to transmit a square wave signal, and the receiving terminal RX is configured to receive the square wave signal transmitted by the transmitting terminal TX. Specifically, a parasitic capacitance CM exists between the transmitting end TX and the receiving end RX, a capacitance value of the parasitic capacitance CM changes when a finger touch is detected, and a signal received by the receiving end RX also changes along with the capacitance value transmission change of the parasitic capacitance CM. Further, an internal compensation capacitor CMB is further present between the receiving terminal RX and the transmitting terminal RX, for example, the internal compensation capacitor CMB is a BASE capacitor, and is used for performing charge balance with an external CM capacitor, and a capacitance value thereof is adjustable.
The receiving terminal RX is connected with the amplifying unit, and the amplifying unit amplifies signals received by the receiving terminal RX.
Specifically, the amplifying unit includes a first amplifying unit, a second amplifying unit, and a third amplifying unit, the first amplifying unit processes the signal received by the receiving terminal RX to generate a voltage V1, and the second amplifying unit and the third amplifying unit perform subsequent processing on the voltage V1 under the control of the timing control unit to generate a voltage V3.
And the analog-to-digital conversion unit performs analog-to-digital conversion on the amplified signal. Specifically, the analog-to-digital conversion unit performs analog-to-digital conversion on the voltage V3, and sends the converted code value to the digital terminal for subsequent judgment and processing.
According to the invention, the amplifying unit is added between the receiving end RX and the analog-to-digital conversion unit, so that the condition that whether finger touch exists can be correctly judged only by sampling the signal of the receiving end RX for multiple times when the capacitance value variation of the parasitic capacitor CM is small can be avoided, the scanning time of a system is saved, the power consumption is greatly reduced, meanwhile, the touch is more accurately and rapidly detected, and the detection is more accurate.
Illustratively, fig. 5 shows a mutual capacitance detection circuit architecture diagram in an embodiment of the present invention. As shown in fig. 5, the parasitic capacitor CM is located between the transmitting terminal TX and the receiving terminal RX. Furthermore, the parasitic capacitor CM is connected in parallel with an internal compensation capacitor BASE capacitor, and the capacitance value of the BASE capacitor CMB is adjustable, and at this time, the capacitance value of the CMB is the same as that of the CM. And a diode is also connected in series on the CMB capacitance branch, the anode of the diode is close to the transmitting end TX, and the cathode of the diode is close to the amplifying unit.
The first amplifying unit comprises a first amplifying operational unit OP1, a reset assembly RST and a feedback capacitor CF, wherein the first amplifying operational unit OP1, the reset assembly RST and the feedback capacitor are all connected in parallel, the reset assembly RST is used for resetting the first operational amplifier OP1, the feedback capacitor CF is used for adjusting a charge amplification coefficient of CA, a negative input end of the first operational amplifier OP1 is connected with an output end of the receiving end RX, a reference voltage VREF is input to a positive input end of the first operational amplifier OP1, and a voltage V1 is output from an output end of the first operational amplifier OP 1. The second amplifying unit comprises a first switch P1, a second switch P2, a holding capacitor CH and a second operational amplifier OP2. Specifically, the positive input terminal of the second operational amplifier is connected to the output terminal of the first operational amplifier OP1, and a first switch P1 is provided in the connection. The holding capacitor CH is provided between the first switch P1 and the second operational amplifier, and is grounded. The positive input end of the second operational amplifier OP2 is connected to the input end of the reference voltage VREF, and is controlled by the second switch P2 to be connected or not. The third amplifying unit comprises a third operational amplifier OP3 and an adjustable capacitor R2, and two ends of the adjustable capacitor R2 are respectively connected with the negative input end and the output end of the third operational amplifier OP 3. The output end of the first operational amplifier OP1 is also connected with the negative input end of the third operational amplifier, and a resistor R1 is connected in series between the connections. The negative input end and the output end of the second operational amplifier OP2 are short-circuited, the output end of the second operational amplifier OP2 outputs a voltage V2, and the output end of the second operational amplifier OP2 is connected with the positive input end of the third operational amplifier OP3, and a resistor R1 is connected in series between the output end of the second operational amplifier OP2 and the positive input end of the third operational amplifier OP 3. The output end of the third operational amplifier OP3 outputs a voltage V3, and the value of the voltage V3 is equal to (V2-V1) × (R2/R1) + V1. The output end of the third operational amplifier OP3 is connected with an analog-to-digital conversion unit ADC, and the analog-to-digital conversion unit ADC is accessed to a sampling hold signal ADC-SH. The analog-to-digital conversion unit performs analog-to-digital conversion on the voltage and is connected with the digital end.
The time sequence control unit provides time sequence control for the whole touch control detection system.
Specifically, fig. 6 shows a voltage change timing control diagram when there is no finger touch. As shown in FIG. 6, the voltage variation of V1/V2/V3 under the condition of no finger touch at different times is as follows:
v1= V2= V3= VREF at time t1;
at the time of t2, the voltage of V1 changes from VREF to generate a corresponding positive edge voltage, and the voltages of V2 and V3 change along with the voltage of V1;
at the time of t3, the voltage of V1 changes to VOUT1, and the voltage of V2 and V3 changes to VOUT1 along with the voltage of V1;
at time t4, the voltage V1 is reset to VREF again, the voltage V2 keeps the voltage VOUT1, and the voltage V3 keeps an intermediate voltage value (VOUT 1-VREF) × (R2/R1) + VREF;
at the time of t5, the voltage V1 continuously changes from the voltage VREF to generate a corresponding negative edge voltage, the voltage V2 continuously keeps the voltage VOUT1, and the voltage V3 continuously increases along with the gradual decrease of the voltage V1;
the V1 voltage changes to VOUT2 at the time of t6, the V2 voltage keeps the VOUT1 voltage, the V3 voltage changes to (VOUT 1-VOUT 2) × (R2/R1) + VOUT1, at the moment, the ADC _ SH samples and keeps the V3 voltage at the time of t6, then the ADC starts analog-to-digital conversion, the voltage value is converted into a corresponding digital CODE value CODE, and after the signal sampling is repeated for N times, the ADC also correspondingly repeats data processing for N times, so that an accumulated value N × CODE of the N times can be obtained;
at the time t7, the voltage V1 is reset to VREF again, the voltage V2 is reset to VREF again, and the voltage V3 returns to the voltage VREF again;
keeping the state of t7 at the time t 8;
the TX scanning of the next period starts again after the time t9, and the cycle is repeated.
If a finger touch causes a corresponding capacitance value of the CM capacitor to change, another set of VOUT voltages can be obtained.
Specifically, fig. 7 shows a timing chart of voltage change when a finger touches. As shown in the figure, the voltage change of V1/V2/V3 under the condition of finger touch at different times is as follows:
v1= V2= V3= VREF at time t1;
at the time t2, the voltage of V1 changes from VREF to generate a corresponding positive edge voltage, and the voltages of V2 and V3 change along with the voltage of V1;
v1 voltage changes to VOUT1 'at the time of t3, and V2 and V3 voltage change to VOUT 1' along with the V1 voltage;
at time t4, the voltage V1 is reset to VREF again, the voltage V2 continues to maintain the voltage VOUT1 ', and the voltage V3 is maintained at an intermediate voltage value (VOUT 1' -VREF) × (R2/R1) + VREF;
at the time of t5, the voltage V1 continuously changes from the voltage VREF to generate a corresponding negative edge voltage, the voltage V2 continuously keeps the voltage VOUT 1', and the voltage V3 continuously increases along with the gradual reduction of the voltage V1;
when the voltage V1 at the time of t6 changes to VOUT2 ', the voltage V2 keeps on keeping VOUT 1', the voltage V3 changes to (VOUT 1 '-VOUT 2') × (R2/R1) + VOUT1 ', at this time, ADC _ SH samples and keeps the voltage V3 at the time of t6, then ADC starts analog-to-digital conversion, the voltage value is converted into a corresponding digital CODE value CODE', when the signal sampling is repeated N times, the ADC also correspondingly repeats data processing N times, thus N times of accumulation value N × CODE 'can be obtained, when the value N × (CODE' -CODE) is more than a set detection threshold value, the finger touch is judged, otherwise, no finger touch is judged;
at the time t7, the voltage V1 is reset to VREF again, the voltage V2 is also reset to VREF again, and the voltage V3 is also reset to the VREF again;
keeping the state of t7 at the time t 8;
the TX scanning of the next period starts again after the time t9, and the cycle is repeated.
Comparing the traditional mutual capacitance detection mode with the mutual capacitance detection mode provided by the invention patent, it can be seen that in the traditional mutual capacitance detection mode, the ADC needs to sample and process the positive edge sampling voltage and the negative edge sampling voltage in turn in each TX scanning period, then the difference is made between the converted CODE values at the digital end to generate the corresponding Δ CODE, and N times of repeated sampling is needed to amplify the corresponding difference value N times to be beneficial to judging whether there is finger touch. The mutual capacitance detection method provided by the invention can realize the effect of sampling for 10 times in the traditional mutual capacitance detection method in one sampling process when the value of R2/R1 is 10, thereby greatly improving the precision of finger touch detection and greatly reducing the scanning time and power consumption loss of the system.
On the basis, the invention also discloses a touch detection method, the sensitivity of touch detection is adjusted by adjusting the resistance value of the adjustable resistor R2, when the resistor R1 is a fixed value, the higher the resistance value of the resistor R2 is, the higher the sensitivity of touch detection is, otherwise, the lower the sensitivity is.
The embodiment of the invention also discloses a display module which comprises the touch detection system and a touch display panel, wherein the touch detection system is connected with the touch display panel. The plurality of parasitic capacitors CM are uniformly distributed below the touch display panel, and the digital end is connected with the touch display panel and outputs a detection result to the touch display panel.
Although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (7)
1. A touch detection system is characterized in that,
the touch detection system comprises a sending end TX, a receiving end RX, an amplifying unit, an analog-to-digital conversion unit, a digital end and a time sequence control unit;
the transmitting end TX is used for transmitting a square wave signal;
the receiving end RX is used for receiving the square wave signal sent by the sending end TX;
the receiving terminal RX is connected to the amplifying unit, and the amplifying unit is configured to amplify a signal received by the receiving terminal RX;
the analog-to-digital conversion unit is used for receiving the amplified voltage and outputting a conversion result;
the digital end is used for receiving the conversion result and carrying out subsequent judgment and processing;
the time sequence control unit is used for controlling the working time sequence of the amplifying unit;
the amplifying unit comprises a first amplifying unit, a second amplifying unit and a third amplifying unit, the first amplifying unit processes the signal received by the receiving terminal RX to generate a voltage V1, and the second amplifying unit and the third amplifying unit perform subsequent processing on the voltage V1 to generate a voltage V3 under the control of the time sequence control unit;
the first amplification unit comprises a first operational amplifier OP1, the second amplification unit comprises a second operational amplifier OP2, and the third amplification unit comprises a third operational amplifier OP3;
the negative input end of the first operational amplifier OP1 is connected with the output end of the receiving end RX, the reference voltage VREF is input to the positive input end of the first operational amplifier OP1, and the output end of the first operational amplifier OP1 outputs the voltage V1;
the positive input end of the second operational amplifier OP2 is connected with the output end of the first operational amplifier OP1, a first switch P1 is arranged in the connecting line, the reference voltage VREF is input into the positive input end of the second operational amplifier OP2, and whether the reference voltage VREF is connected or not is controlled by the second switch P2;
the output end of the first operational amplifier OP1 is further connected with the negative input end of the third operational amplifier OP3, a resistor R1 is connected in series between the connections, the negative input end and the output end of the second operational amplifier OP2 are short-circuited, the output end of the second operational amplifier OP2 outputs a voltage V2, the output end of the second operational amplifier OP2 is connected with the positive input end of the third operational amplifier OP3, a resistor R1 is connected in series between the output end and the negative input end of the third operational amplifier OP3, and an adjustable capacitor R2 is connected in series between the output end and the negative input end of the third operational amplifier OP3; the output end of the third operational amplifier OP3 outputs a voltage V3, and is connected to the analog-to-digital conversion unit ADC.
2. The touch detection system of claim 1,
a parasitic capacitor CM exists between the transmitting end TX and the receiving end RX, and a capacitance value of the parasitic capacitor changes when a finger touch is detected.
3. The touch detection system of claim 1,
the voltage V3 has a value equal to (V2-V1) × (R2/R1) + V1;
wherein R2 is an adjustable resistor, and R1 is a constant value resistor.
4. The touch detection system of claim 1,
under the condition of no finger touch, the control logic of the time sequence control unit is as follows:
v1= V2= V3= VREF at time t1;
at the time of t2, the voltage of V1 changes from VREF to generate a corresponding positive edge voltage, and the voltages of V2 and V3 change along with the voltage of V1;
the voltage of V1 changes to VOUT1 at the time of t3, and the voltage of V2 and V3 changes to VOUT1 along with the voltage of V1;
at time t4, the voltage V1 is reset to VREF again, the voltage V2 continues to maintain the voltage VOUT1, and the voltage V3 is maintained at an intermediate voltage value (VOUT 1-VREF) × (R2/R1) + VREF;
at the time of t5, the voltage V1 continuously changes from the voltage VREF to generate a corresponding negative edge voltage, the voltage V2 continuously keeps the voltage VOUT1, and the voltage V3 continuously increases along with the gradual decrease of the voltage V1;
the V1 voltage changes to VOUT2 at the time of t6, the V2 voltage keeps the VOUT1 voltage, the V3 voltage changes to (VOUT 1-VOUT 2) × (R2/R1) + VOUT1, at the moment, the ADC _ SH samples and keeps the V3 voltage at the time of t6, then the ADC starts analog-to-digital conversion, the voltage value is converted into a corresponding digital CODE value CODE, and after the signal sampling is repeated for N times, the ADC also correspondingly repeats data processing for N times, so that an accumulated value N × CODE of the N times can be obtained;
at the time t7, the voltage V1 is reset to VREF again, the voltage V2 is reset to VREF again, and the voltage V3 returns to the voltage VREF again;
keeping the state of t7 at the time t 8;
the TX scan of the next cycle starts again after time t9, and the cycle is repeated.
5. The touch detection system of claim 1,
under the condition of finger touch, the control logic of the time sequence control unit is as follows:
v1= V2= V3= VREF at time t1;
at the time t2, the voltage of V1 changes from VREF to generate a corresponding positive edge voltage, and the voltages of V2 and V3 change along with the voltage of V1;
at the time of t3, the voltage of V1 changes to VOUT1 ', and the voltage of V2 and V3 changes to VOUT 1' along with the voltage of V1;
at time t4, the voltage V1 is reset to VREF, the voltage V2 continues to maintain the voltage VOUT1 ', and the voltage V3 is maintained at an intermediate voltage (VOUT 1' -VREF) × (R2/R1) + VREF;
at the time of t5, the voltage V1 continuously changes from the voltage VREF to generate a corresponding negative edge voltage, the voltage V2 continuously keeps the voltage VOUT 1', and the voltage V3 continuously increases along with the gradual reduction of the voltage V1;
when the voltage V1 at the time of t6 changes to VOUT2 ', the voltage V2 keeps on keeping VOUT 1', the voltage V3 changes to (VOUT 1 '-VOUT 2') × (R2/R1) + VOUT1 ', at this time, ADC _ SH samples and keeps the voltage V3 at the time of t6, then ADC starts analog-to-digital conversion, the voltage value is converted into a corresponding digital CODE value CODE', when the signal sampling is repeated N times, the ADC also correspondingly repeats data processing N times, thus N times of accumulation value N × CODE 'can be obtained, when the value N × (CODE' -CODE) is more than a set detection threshold value, the finger touch is judged, otherwise, no finger touch is judged;
at the time t7, the voltage V1 is reset to VREF again, the voltage V2 is also reset to VREF again, and the voltage V3 is also reset to the VREF again;
keeping the state of t7 at the time t 8;
the TX scan of the next cycle starts again after time t9, and the cycle is repeated.
6. A control method for a touch detection system according to any one of claims 3 to 5,
and adjusting the sensitivity of the touch detection by adjusting the resistance value of the adjustable resistor R2.
7. A display module of the touch detection system according to any one of claims 1 to 5,
the display module comprises the touch detection system and a touch display panel, parasitic capacitors CM of the touch detection system are uniformly distributed below the touch display panel, and the digital end is connected with the touch display panel.
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