CN115343538B - Signal measurement circuit and capacitive touch screen - Google Patents
Signal measurement circuit and capacitive touch screen Download PDFInfo
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- CN115343538B CN115343538B CN202211270716.4A CN202211270716A CN115343538B CN 115343538 B CN115343538 B CN 115343538B CN 202211270716 A CN202211270716 A CN 202211270716A CN 115343538 B CN115343538 B CN 115343538B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
- G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
- G01R27/26—Measuring inductance or capacitance; Measuring quality factor, e.g. by using the resonance method; Measuring loss factor; Measuring dielectric constants ; Measuring impedance or related variables
- G01R27/2605—Measuring capacitance
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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
- G06F3/0412—Digitisers structurally integrated in a display
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Abstract
The embodiment of the application relates to the technical field of microelectronics, and discloses a signal measuring circuit and a capacitive touch screen. The signal measurement circuit includes: a first signal measurement circuit and a second signal measurement circuit; the first end of the first signal measurement circuit is grounded, the second end of the first signal measurement circuit is connected with the first end of the second signal measurement circuit, and the first signal measurement circuit is used for receiving a first signal and inputting the first signal to the second signal measurement circuit; the second end of the second signal measuring circuit is connected with the first end of the capacitor to be measured, the second end of the second signal measuring circuit is grounded, the second end of the capacitor to be measured is provided with excitation voltage, and the second signal measuring circuit is used for receiving a second signal and outputting a third signal according to the first signal and the second signal. The touch control method has the advantages that the touch point reporting rate of the capacitive touch screen can not be influenced, the generated interference is effectively inhibited, and the accurate value of the normal capacitance signal change is obtained.
Description
Technical Field
The embodiment of the application relates to the technical field of microelectronics, in particular to a signal measurement circuit and a capacitive touch screen.
Background
In the application of the capacitive touch screen, the capacitive touch screen is often placed close to a cathode plate of the display screen, i.e. a common ground of the display screen, in order to reduce external interference. Fig. 1 is a row-column arrangement of an Active-matrix organic light-emitting diode (AMOLED) -based display screen, in which an enable switch of an LED lamp is gated row by row signals, and then high or low assignment is performed by column signals, so that the display screen can be turned on or off. However, in the implementation process, the cathode plate of the display screen may be greatly interfered, and the interference may be coupled to the receiving end through the capacitance between the cathode plate and the receiving metal line (RX line) of the capacitive touch screen, and the interference is often much larger than the amplitude of the normal signal, thereby interfering the reception of the normal signal of the capacitive touch screen.
In order to suppress the above interference, one way is to subtract signals received by two RX lines to suppress the interference, but this way would subtract the common mode part of the normal signal, so that the accurate value of the change of the normal capacitance signal received by the RX line cannot be obtained; the other method is to use a time-sharing method to enable two RX lines to measure the capacitance signal and the interference signal respectively and subtract the two RX lines, but this method will reduce the reporting rate of the capacitive touch screen.
Disclosure of Invention
An object of the embodiments of the present application is to provide a signal measurement channel and a capacitive touch screen, which can effectively suppress interference on the capacitive touch screen without affecting a reporting rate, so as to obtain an accurate value of a normal capacitance signal change.
To solve the above technical problem, an embodiment of the present application provides a signal measurement circuit, including: a first signal measurement circuit and a second signal measurement circuit; the first end of the first signal measurement circuit is grounded, the second end of the first signal measurement circuit is connected with the first end of the second signal measurement circuit, and the first signal measurement circuit is used for receiving a first signal and inputting the first signal to the second signal measurement circuit; the second end of the second signal measuring circuit is connected with the first end of the capacitor to be measured, the second end of the second signal measuring circuit is grounded, the second end of the capacitor to be measured is provided with excitation voltage, and the second signal measuring circuit is used for receiving a second signal and outputting a third signal according to the first signal and the second signal.
The embodiment of the application also provides a capacitive touch screen which comprises the signal measuring circuit.
Compared with the prior art, the signal measurement circuit comprises: the first signal measuring circuit can receive a first signal from a ground end, namely an interference signal generated by a cathode plate of a display screen, because the first end of the first signal measuring circuit is grounded, the first signal measuring circuit can receive the first signal from the ground end, and the second end of the first signal measuring circuit is connected with the first end of the second signal measuring circuit, the first signal measuring circuit can input the received first signal into the second signal measuring circuit, the second end of the second signal measuring circuit is connected with the first end of a capacitor to be measured, the second end of the second signal measuring circuit is also grounded, and the second end of the capacitor to be measured is configured with an excitation voltage, so that the second signal measuring circuit can receive a second signal, wherein the second signal specifically comprises a normal capacitor signal and an interference signal of the capacitor to be measured, therefore, the second signal measuring circuit can output a third signal according to the first signal input by the second signal and the first signal measuring circuit, namely the second signal and the first signal are subtracted, and the interference signal therein is eliminated. In the application, because the first signal measuring circuit is used for independently receiving the interference signal, when the second signal is subtracted from the first signal, the normal capacitance signal is not influenced, and the accurate value of the change of the normal capacitance signal received by the RX line can be obtained; and the signal receiving work of the first signal measuring circuit and the second signal measuring circuit is carried out simultaneously, so that the touch time delay, namely the touch reporting rate of the capacitive touch screen, is not reduced, and more power consumption is not needed to be increased to maintain the normal touch reporting rate of the capacitive touch screen.
In addition, the signal measuring circuit further comprises a first component, the first signal measuring circuit is connected with the second signal measuring circuit through the first component, and the first component is used for adjusting the size of the first signal. In the application, the first component is used for adjusting the size of the first signal, so that the interference signal in the second signal measuring circuit is equal to the first signal as much as possible, and the interference is completely eliminated.
In addition, the first signal measurement circuit includes a first capacitance, a first amplifier, and a second component; the first end of the first capacitor is grounded, the second end of the first capacitor is connected with the inverting input end of the first amplifier, and the second component is connected across the inverting input end and the output end of the first amplifier; the first capacitor is used for receiving the first signal and inputting the first signal to the first amplifier, and the first amplifier is used for outputting a fourth signal according to the first signal and inputting the fourth signal to the second signal measuring circuit.
In addition, the second signal measurement circuit includes: a second capacitor, a second amplifier and a third element; the first end of the second capacitor is grounded, the second end of the second capacitor is connected with the inverting input end of the second amplifier, the inverting input end of the second amplifier is also connected with the first end of the capacitor to be detected, and the third element device is bridged between the inverting input end and the output end of the second amplifier; the output end of the first amplifier is connected with the inverting input end of the second amplifier, and the second amplifier is used for receiving the second signal and the fourth signal and outputting a fifth signal according to the second signal and the fourth signal.
In addition, a first end of the first component is specifically connected with the output end of the first amplifier, and a second end of the first component is specifically connected with the inverting input end of the second amplifier; the first component is specifically configured to adjust a magnitude of the fourth signal.
In addition, the first signal measurement circuit further comprises a third amplifier, a fourth element and a fifth element; the first end of the fourth element is connected with the output end of the first amplifier, the second end of the fourth element is connected with the inverting input end of the third amplifier, and the fifth element is bridged on the inverting input end and the output end of the third amplifier; the third amplifier is used for outputting a sixth signal according to the fourth signal and inputting the sixth signal to the second signal measuring circuit.
In addition, the second signal measurement circuit further includes: a fourth amplifier, a sixth element device and a seventh element device; the first end of the sixth-element device is connected with the output end of the second amplifier, the second end of the sixth-element device is connected with the inverting input end of the fourth amplifier, and the seventh-element device is bridged on the inverting input end and the output end of the fourth amplifier; the second amplifier is used for outputting a seventh signal according to the second signal; the output end of the third amplifier is connected with the inverting input end of the fourth amplifier, and the fourth amplifier is used for receiving the seventh signal and the sixth signal and outputting an eighth signal according to the seventh signal and the sixth signal.
In addition, a first end of the first component is specifically connected to the output end of the third amplifier, and a second end of the first component is specifically connected to the inverting input end of the fourth amplifier; the first component is specifically configured to adjust a magnitude of the sixth signal.
In addition, the first component, the second component, the third component, the fourth component, the fifth component, the sixth component, and the seventh component are all resistors.
In addition, the product of the resistance value of the fifth element and the capacitance value of the first capacitor is equal to the product of the resistance value of the fourth element and the capacitance value of the second capacitor. To more effectively suppress interference.
In addition, the second component and the third component have equal resistance values. To more effectively suppress interference.
Drawings
One or more embodiments are illustrated by the corresponding figures in the drawings, which are not meant to be limiting.
FIG. 1 is a schematic diagram of a row-column arrangement of a display screen;
FIG. 2 is a first schematic diagram of the connection of a signal measurement circuit according to an embodiment of the present application;
FIG. 3 is a second schematic diagram of a connection of a signal measurement circuit according to an embodiment of the present application;
FIG. 4 is a third schematic diagram of a connection of a signal measurement circuit provided in accordance with an embodiment of the present application;
fig. 5 is a schematic structural diagram of a capacitive touch screen according to an embodiment of the present application.
Detailed Description
To make the objects, technical solutions and advantages of the embodiments of the present application clearer, the embodiments of the present application will be described in detail below with reference to the accompanying drawings. However, it will be appreciated by those of ordinary skill in the art that in the examples of the present application, numerous technical details are set forth in order to provide a better understanding of the present application. However, the technical solution claimed in the present application can be implemented without these technical details and various changes and modifications based on the following embodiments. The following embodiments are divided for convenience of description, and should not constitute any limitation to the specific implementation manner of the present application, and the embodiments may be mutually incorporated and referred to without contradiction.
One embodiment of the present application relates to a signal measurement circuit, comprising: a first signal measurement circuit and a second signal measurement circuit; the first end of the first signal measuring circuit is grounded, the second end of the first signal measuring circuit is connected with the first end of the second signal measuring circuit, and the first signal measuring circuit is used for receiving a first signal and inputting the first signal to the second signal measuring circuit; the second end of the second signal measuring circuit is connected with the first end of the capacitor to be measured, the second end of the second signal measuring circuit is grounded, the second end of the capacitor to be measured is provided with an excitation voltage, the second signal measuring circuit is used for receiving a second signal and outputting a third signal according to the first signal and the second signal, and the interference on the capacitive touch screen can be effectively inhibited on the premise of not influencing the reporting rate, so that the accurate value of the change of the normal capacitance signal can be obtained.
The following is a detailed description of the implementation details of the signal measurement circuit of the present embodiment, and the following is provided only for the convenience of understanding and is not necessary for implementing the present embodiment. Referring to fig. 2, a connection schematic diagram of the signal measurement circuit of this embodiment at least includes: a first signal measuring circuit 21, a second signal measuring circuit 22 and a capacitor 23 to be measured.
Specifically, a first terminal of the first signal measurement circuit 21 is grounded, a second terminal of the first signal measurement circuit 21 is connected to a first terminal of the second signal measurement circuit 22, and the first signal measurement circuit 21 is configured to receive a first signal and input the first signal to the second signal measurement circuit 22. The first end of the first signal measuring circuit 21 is grounded, that is, the first end of the first signal measuring circuit 21 is connected to the cathode plate of the capacitive touch screen to obtain a first signal generated by the cathode plate, where the first signal is an interference signal. Where Vn represents an interference signal and Vdrv represents an excitation voltage.
The second end of the second signal measurement circuit 22 is connected to the first end of the capacitor 23 to be measured, and the second end of the second signal measurement circuit 22 is also grounded. The second end of the capacitor to be measured 23 is configured with an excitation voltage, and the second signal measurement circuit 22 is configured to receive the second signal and output a third signal according to the first signal and the second signal. The second end of the capacitor 23 to be measured is configured with an excitation voltage, that is, the capacitive touch screen is touched, the signal of the capacitor 23 to be measured changes, the capacitance signal of the capacitor 23 to be measured needs to be measured, meanwhile, the cathode plate generates an interference signal, and both the first signal measuring circuit 21 and the second signal measuring circuit 22 can receive the interference signal.
In one example, the signal measurement circuit further comprises: the first component 24, the first signal measurement circuit 21 is connected with the second signal measurement circuit 22 through the first component 24, and the first component 24 is used for adjusting the size of the first signal. The first signal is sized by the first component 24 so that the interference signal in the second signal measurement circuit 22 is as equal as possible to the first signal to completely cancel the interference signal in the second signal.
It is understood that the output terminal of the second signal measuring circuit 22 of the present embodiment is further connected to an analog-to-digital conversion circuit, so as to input the third signal to the analog-to-digital conversion circuit, and complete the processing of the third signal at the digital terminal.
In this embodiment, since the first end of the first signal measuring circuit is grounded, the first signal measuring circuit may receive a first signal from the ground, that is, an interference signal generated by the cathode plate of the display screen, and the second end of the first signal measuring circuit is connected to the first end of the second signal measuring circuit, the first signal measuring circuit may input the received first signal into the second signal measuring circuit, the second end of the second signal measuring circuit is connected to the first end of the capacitor to be measured, the second end of the second signal measuring circuit is also grounded, and the second end of the capacitor to be measured is configured with an excitation voltage, the second signal measuring circuit may receive a second signal, where the second signal specifically includes a normal capacitor signal and an interference signal of the capacitor to be measured, and therefore, the second signal measuring circuit may output a third signal according to the second signal and the first signal input by the first signal measuring circuit, that is to subtract the second signal from the first signal, and eliminate the interference signal therein. In the application, the first signal measuring circuit is used for independently receiving the interference signal, so that when the second signal is subtracted from the first signal, the normal capacitance signal is not influenced, and the accurate value of the change of the normal capacitance signal received by the RX line can be obtained; and the signal receiving work of the first signal measuring circuit and the second signal measuring circuit is carried out simultaneously, so that the touch time delay, namely the touch reporting rate of the capacitive touch screen, is not reduced, and more power consumption is not needed to be increased to maintain the normal touch reporting rate of the capacitive touch screen.
In one embodiment, the connection schematic of the signal measurement circuit of the present application is shown in fig. 3, and includes at least: a first signal measuring circuit 31, a second signal measuring circuit 32 and a capacitor to be measured 33.
Specifically, the first signal measurement circuit 31 includes: a first capacitor 311, a first amplifier 312 and a second component 313. Wherein, the first end of the first capacitor 311 is grounded, the second end of the first capacitor 311 is connected to the inverting input terminal of the first amplifier 312, and the second component 313 is connected across the inverting input terminal and the output terminal of the first amplifier 312; the first capacitor 311 is configured to receive the first signal and input the first signal to the first amplifier 312, and the first amplifier 312 is configured to output a fourth signal according to the first signal and input the fourth signal to the second signal measuring circuit 32.
It can be seen that the first capacitor 311 can input the first signal generated by the cathode plate to the first amplifier 312, amplify the first signal in the first amplifier 312, and input the fourth signal generated after amplification to the second signal measuring circuit 32.
The second signal measurement circuit 32 includes: a second capacitor 321, a second amplifier 322, and a third ternary device 323; the first end of the second capacitor 321 is grounded, the second end of the second capacitor 321 is connected with the inverting input end of the second amplifier 322, the inverting input end of the second amplifier 322 is also connected with the first end of the capacitor 33 to be tested, and the third component 323 is connected across the inverting input end and the output end of the second amplifier 322; the output terminal of the first amplifier 312 is connected to the inverting input terminal of the second amplifier 322, and the second amplifier 322 is configured to receive the second signal and the fourth signal and output a fifth signal according to the second signal and the fourth signal.
It can be seen that the input of the second amplifier 322 is the second signal and the fourth signal input by the first amplifier 312, wherein the second signal comprises: the second capacitor 321 receives the interference signal of the cathode plate and the normal capacitance signal of the capacitor 33 to be measured. The second amplifier 322 is configured to output a fifth signal by subtracting the input second signal from the fourth signal.
In one example, the signal measurement circuit further comprises: a first component 34, a first terminal of the first component 34 being connected to the output terminal of the first amplifier 312, and a second terminal of the first component 34 being connected to the inverting input terminal of the second amplifier 322; the first component 34 is specifically configured to adjust the magnitude of the fourth signal so that the interference signal in the second signal input to the second amplifier 322 is equal to the fourth signal as much as possible, so as to completely eliminate the interference signal in the second signal.
In a specific example, the first component 34, the second component 313, and the third component 323 described in this embodiment may all be resistors, and the first component 34, the second component 313, and the third component 323 may also be adjustable resistors to adjust the amplification degree of the signal.
Further, the product of the resistance of the second component 313 and the capacitance of the first capacitor 311 in this embodiment is equal to the product of the resistance of the first component 34 and the capacitance of the second capacitor 321.
The following description will be given taking the first component 34, the second component 313, and the third component 323 as the resistors as examples:
suppose Vdrv represents the excitation voltage, cm is the capacitance value of the capacitor 33 to be measured, vn is the interference signal, R1 is the resistance value of the first component 34, cref is the capacitance value of the first capacitor 311, R2 is the resistance value of the second component 313, cs is the capacitance value of the second capacitor 321, and R3 is the resistance value of the third component 323.
Then, the input of the first signal measuring circuit 31, i.e. the first signal received by the first capacitor 311, is: in _ ref = Vn · Cref · s; where s = jw, j is the unit imaginary number, and w is the angular frequency of the voltage.
The output of the first signal measurement circuit 31, i.e. the output of the first amplifier 312, is: v0= -In _ ref x R2
The input of the second signal measurement circuit 32, i.e. the second signal received by the second amplifier 322, is: irx = In _ rx + Im; in _ rx is an interference signal received by the second capacitor 321, and Im is a normal capacitance signal of the capacitor 33 to be measured.
And In _ rx = Vn · Cs · s; im = Vdrv · Cm · s.
The output of the second signal measurement circuit 32, i.e. the output of the second amplifier 322, is:
Vrx_final=-R3（Im+Vn·Cs·s-R2/R1·Vn·Cref·s）
when the product of the resistance value of the second component element 313 and the capacitance value of the first capacitor 311 is equal to the product of the resistance value of the first component element 34 and the capacitance value of the second capacitor 321, i.e., R2/R1= Cs/Cref, vrx _ final = -R3 = Im
It can be seen that Vn is eliminated from the output signal of the second signal measuring circuit 32, effectively suppressing the interference generated by the cathode plate.
In another specific example, the first component 34, the second component 313 and the third component 323 may all be capacitors.
It should be noted that the first component 34, the second component 313, and the third component 323 can also be any combination of resistors and capacitors.
The signal measurement circuit of this embodiment shows a specific structure of the first signal measurement circuit and the second signal measurement circuit, and can effectively suppress interference on the capacitive touch screen on the premise of not affecting the reporting rate, so as to obtain an accurate value of the normal capacitance signal change.
In one embodiment, a connection schematic diagram of a signal measurement circuit of the present application is shown in fig. 4, and includes at least: a first signal measuring circuit 41, a second signal measuring circuit 42 and a capacitor 43 to be measured.
Specifically, the first signal measurement circuit 41 includes: a first capacitor 411, a first amplifier 412, a second component 413, a fourth component 414, a third amplifier 415, and a fifth component 416. The connection relationship and the function of the first capacitor 411, the first amplifier 412, and the second component 413 are the same as those of the first capacitor 411, the first amplifier 412, and the second component 413, and are not described herein again. A first terminal of the fourth element 414 is coupled to the output terminal of the first amplifier 412, a second terminal of the fourth element 414 is coupled to the inverting input terminal of the third amplifier 415, and a fifth element 416 is coupled across the inverting input terminal and the output terminal of the third amplifier 415; the third amplifier 415 is configured to output a sixth signal according to the fourth signal, and input the sixth signal to the second signal measurement circuit 42.
It can be seen that in the present embodiment, after the first amplifier 412 outputs the amplified fourth signal, the fourth signal is input to the third amplifier 415 again, the third amplifier 415 also amplifies the fourth signal again, and the sixth signal generated after the amplification is input to the second signal measurement circuit 42.
The second signal measurement circuit 42 includes: a second capacitor 421, a second amplifier 422, a third component 423, a sixth component 424, a fourth amplifier 425, and a seventh component 426. The first end of the second capacitor 421 is grounded, the second end of the second capacitor 421 is connected to the inverting input terminal of the second amplifier 422, the inverting input terminal of the second amplifier 422 is further connected to the first end of the capacitor 43 to be tested, and the third component 423 is bridged between the inverting input terminal and the output terminal of the second amplifier 422; the second amplifier 422 is configured to receive the second signal and output a seventh signal according to the second signal. The first terminal of the sixth component 424 is connected to the output terminal of the second amplifier 422, the second terminal of the sixth component 424 is connected to the inverting input terminal of the fourth amplifier 425, the seventh component 426 is connected across the inverting input terminal and the output terminal of the fourth amplifier 425, the output terminal of the third amplifier 415 is connected to the inverting input terminal of the fourth amplifier 425, and the fourth amplifier 425 is configured to receive the seventh signal and the sixth signal and output an eighth signal according to the seventh signal and the sixth signal.
It can be seen that the second amplifier 422 in this embodiment is configured to amplify the second signal, that is, the interference signal of the cathode plate received by the second capacitor 421 and the normal capacitor signal of the capacitor 43 to be measured, and input the amplified seventh signal to the fourth amplifier 425, and at the same time, the sixth signal output by the third amplifier 415 is also input to the fourth amplifier 425, so that the fourth amplifier 425 may perform a difference between the input seventh signal and the input sixth signal and output an eighth signal.
In one example, the signal measurement circuit further comprises: a first component 44, a first terminal of the first component 44 being connected to an output terminal of the third amplifier 415, and a second terminal of the first component 44 being connected to an inverting input terminal of the fourth amplifier 425; the first component 44 is specifically configured to adjust the magnitude of the sixth signal so that the interference signal in the seventh signal input to the fourth amplifier 425 is equal to the sixth signal output from the third amplifier 415 as much as possible, so as to completely eliminate the interference signal in the seventh signal.
In a specific example, the first component 44, the second component 413, the third component 423, the fourth component 414, the fifth component 416, the sixth component 424, and the seventh component 426 described in this embodiment may all be resistors, and the first component 44, the second component 413, the third component 423, the fifth component 416, and the seventh component 426 may also be adjustable resistors to adjust the amplification degree of the signal.
Further, if the first component 44, the second component 413, the third component 423, the fourth component 414, the fifth component 416, the sixth component 424, and the seventh component 426 are resistors, the product of the resistance value of the fifth component 416 and the capacitance value of the first capacitor 411 in this embodiment is equal to the product of the resistance value of the fourth component 414 and the capacitance value of the second capacitor 421.
Further, the second and third components 413, 423 are equal in resistance.
The following description will take the first, second, third, fourth and seventh components 44, 413, 423, 414, 416, 424 and 426 as resistors as examples:
let Vdrv denote the excitation voltage, cm be the capacitance of the capacitor 43 to be measured, vn be the interference signal, R1 be the resistance of the first component 44, cref be the capacitance of the first capacitor 411, R2 be the resistance of the second component 413, R4 be the resistance of the fourth component 414, R5 be the resistance of the fifth component 416, cs be the capacitance of the second capacitor 421, R3 be the resistance of the third component 423, R6 be the resistance of the sixth component 424, and R7 be the resistance of the seventh component 426.
Then, the input of the first signal measuring circuit 41, i.e. the first signal received by the first capacitor 411, is:
in _ ref = Vn · Cref · s; where s = jw, j is the unit imaginary number and w is the angular frequency of the voltage.
The output of the first signal measurement circuit 41, i.e. the output of the second amplifier 422, is:
Vref=-（R5/R4）·R3·In_ref
the inputs to the second signal measurement circuit 42, i.e. the inputs to the second amplifier 422, are: irx = In _ rx + Im; in _ rx is an interference signal received by the second capacitor 421, and Im is a normal capacitance signal of the capacitor 43 to be measured.
Wherein In _ rx = Vn · Cs · s; im = Vdrv · Cm · s
The output of the second amplifier 422 is: vrx = R3 · (In _ rx + Im)
The output of the second signal measurement circuit 42, i.e. the output of the fourth amplifier 425, is: vrx _ final = Vrx + Vref
Namely, vrx _ final = R2/R7 · R3 · Im + R2/R7 · R3 · Vn · Cs-R2/R7 · R5/R4 · R1 · Vn · Cref · s
When the product of the resistance value of the fifth component 416 and the capacitance value of the first capacitor 411 is equal to the product of the resistance value of the fourth component 414 and the capacitance value of the second capacitor 421, i.e., R5/R4= Cs/Cref, and the resistance values of the second component 413 and the third component 423 are equal, i.e., R1= R3, vrx _ final = R2/R7 · R3 · Vdrv · Cm · s
It can be seen that Vn is eliminated from the output signal of the second signal measuring circuit 42, effectively suppressing interference generated by the cathode plate.
In another specific example, the first component 44, the second component 413, the third component 423, the fourth component 414, the fifth component 416, the sixth component 424, and the seventh component 426 may all be capacitors according to this embodiment.
It should be noted that first component 44, second component 413, third component 423, fourth component 414, fifth component 416, sixth component 424, and seventh component 426 may also be any combination of resistors and capacitors.
For example, when the second and third components 413, 423 are capacitors, and the fourth, fifth, sixth and seventh components 414, 416, 424 and 426 of the first component 44 are resistors, the output of the second signal measurement circuit 42, i.e., the output of the fourth amplifier 425, is:
Vrx_final=R2/R7·Cm/C3·Vdrv·s
in an example, the present embodiment may directly input the first signal In _ ref received by the first capacitor 411 into a control unit with an adjustable gain of a, and based on the above formula, the output of the control unit is: iref = a · In _ ref
And In _ ref is mirrored into the second signal measurement circuit 42 through the current mirror, the signal finally output by the second signal measurement circuit 42 is: irx _ final = Irx-Iref = Im + Vn · Cs · s-a · Vn · Cref · s
If a = Cs/Cref, irx _ final = Vdrv · Cm · s
It can be seen that Vn is eliminated from the signal output by the second signal measuring circuit 42, effectively suppressing interference generated by the cathode plate.
The signal measurement circuit of this embodiment shows another specific structure of the first signal measurement circuit and the second signal measurement circuit, and can effectively suppress interference on the capacitive touch screen on the premise of not affecting the reporting rate, so as to obtain an accurate value of the normal capacitance signal change.
In practical implementation, the first capacitor described in the above embodiment is specifically arranged in the capacitive touch screen in a manner shown in fig. 5, and the capacitive touch screen at least includes: a cathode plate 51 of a capacitive touch screen, RX lines 52, transmission metal lines (TX lines) 53, a touch chip 54, and a first capacitor 55.
The RX lines 52 and the TX lines 53 are receiving terminals and transmitting terminals of the capacitive touch chip 54, are arranged in rows and columns in a crossed manner, and are adjacent to the capacitive screen cathode plate 51, and a plurality of parasitic capacitors 56, i.e., the second capacitors described in the above embodiments, exist between the RX lines 52 and the capacitive screen cathode plate 51.
A first end of the first capacitor 55 is connected to the cathode plate 51 of the capacitive touch screen, that is, the first end of the first capacitor 55 is grounded, and a second end of the first capacitor 55 is connected to the first port of the touch chip 54.
An embodiment of the present application relates to a capacitive touch screen, including the signal measurement circuit described in any of the above embodiments.
It is to be understood that the present embodiment is a capacitive touch panel embodiment corresponding to the circuit embodiment, and the present embodiment can be implemented in cooperation with the signal measurement circuit embodiment. Related technical details mentioned in the signal measurement circuit embodiment are still valid in this embodiment, and are not described herein again in order to reduce repetition. Accordingly, the related art details mentioned in the present embodiment can also be applied to the signal measurement circuit embodiment.
It will be understood by those of ordinary skill in the art that the foregoing embodiments are specific examples of the practice of the disclosure, and that various changes in form and detail may be made therein without departing from the spirit and scope of the embodiments of the disclosure. Various changes and modifications may be effected therein by one of ordinary skill in the pertinent art without departing from the scope or spirit of the embodiments of the present disclosure, and it is therefore intended that the scope of the embodiments of the present disclosure be limited only by the terms of the appended claims.
Claims (8)
1. A signal measurement circuit, comprising: a first signal measurement circuit and a second signal measurement circuit;
the first end of the first signal measurement circuit is grounded, the second end of the first signal measurement circuit is connected with the first end of the second signal measurement circuit, and the first signal measurement circuit is used for receiving a first signal and inputting the first signal to the second signal measurement circuit;
the second end of the second signal measuring circuit is connected with the first end of the capacitor to be measured, the second end of the second signal measuring circuit is also grounded, the second end of the capacitor to be measured is provided with an excitation voltage, and the second signal measuring circuit is used for receiving a second signal and outputting a third signal according to the first signal and the second signal;
the first signal measurement circuit comprises a first capacitor, a first amplifier and a second component; the first end of the first capacitor is grounded, the second end of the first capacitor is connected with the inverting input end of the first amplifier, and the second component is connected across the inverting input end and the output end of the first amplifier; the first capacitor is used for receiving the first signal and inputting the first signal to the first amplifier, and the first amplifier is used for outputting a fourth signal according to the first signal and inputting the fourth signal to the second signal measuring circuit;
the second signal measurement circuit includes: a second capacitor, a second amplifier and a third element; the first end of the second capacitor is grounded, the second end of the second capacitor is connected with the inverting input end of the second amplifier, the inverting input end of the second amplifier is also connected with the first end of the capacitor to be detected, and the third element device is bridged between the inverting input end and the output end of the second amplifier; the output end of the first amplifier is connected with the inverting input end of the second amplifier, and the second amplifier is used for receiving the second signal and the fourth signal and outputting a fifth signal according to the second signal and the fourth signal;
the signal measuring circuit further comprises a first component, a first end of the first component is specifically connected with the output end of the first amplifier, a second end of the first component is specifically connected with the inverting input end of the second amplifier, and the first component is specifically used for adjusting the magnitude of the fourth signal;
the product of the resistance value of the second component element and the capacitance value of the first capacitor is equal to the product of the resistance value of the first component element and the capacitance value of the second capacitor.
2. The signal measurement circuit of claim 1, wherein the first signal measurement circuit further comprises a third amplifier, a fourth device, and a fifth device;
the first end of the fourth element is connected with the output end of the first amplifier, the second end of the fourth element is connected with the inverting input end of the third amplifier, and the fifth element is bridged on the inverting input end and the output end of the third amplifier;
the third amplifier is used for outputting a sixth signal according to the fourth signal and inputting the sixth signal to the second signal measuring circuit.
3. The signal measurement circuit of claim 2, wherein the second signal measurement circuit further comprises: a fourth amplifier, a sixth element device and a seventh element device;
the first end of the sixth-element device is connected with the output end of the second amplifier, the second end of the sixth-element device is connected with the inverting input end of the fourth amplifier, and the seventh-element device is bridged on the inverting input end and the output end of the fourth amplifier; the second amplifier is used for outputting a seventh signal according to the second signal;
the output end of the third amplifier is connected with the inverting input end of the fourth amplifier, and the fourth amplifier is used for receiving the seventh signal and the sixth signal and outputting an eighth signal according to the seventh signal and the sixth signal.
4. A signal measuring circuit according to claim 3, wherein the first terminal of the first component is in particular connected to the output of the third amplifier and the second terminal of the first component is in particular connected to the inverting input of the fourth amplifier; the first component is specifically configured to adjust a magnitude of the sixth signal.
5. The signal measurement circuit of claim 4, wherein the first, second, third, fourth, fifth, sixth, and seventh components are resistors.
6. The signal measurement circuit of claim 5, wherein a product of a resistance value of the fifth component and a capacitance value of the first capacitor is equal to a product of a resistance value of the fourth component and a capacitance value of the second capacitor.
7. The signal measurement circuit of claim 5, wherein the second and third components are equal in resistance.
8. A capacitive touch screen, comprising: a signal measurement circuit as claimed in any one of claims 1 to 7.
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