CN221100907U - Mutual capacitance detection circuit, touch chip and electronic equipment - Google Patents
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Abstract
The application relates to a mutual capacitance detection circuit, a touch chip and electronic equipment. The circuit comprises: the system comprises a signal sending end, a signal receiving end, a counteracting module and a signal amplifying module; a mutual capacitor to be tested is connected in series between the signal sending end and the signal receiving end; the cancellation module comprises a cancellation capacitor, a first switch unit and a switch signal generation unit; one end of the counteracting capacitor is respectively connected with the signal receiving end and the input end of the signal amplifying module; the first switch unit is respectively connected with the other end of the counteracting capacitor and the switch signal generating unit; the first switch unit is also connected with the feedback loop of the signal amplifying module and is used for adjusting the feedback form of the feedback loop according to the switch signal output by the switch signal generating unit. The application can counteract the influence of the capacitance value of the mutual capacitance to be detected on the signal amplifying module, and avoids the problems of smaller mutual capacitance detection range and low detection precision caused by the saturation of the signal amplifying module.
Description
Technical Field
The present application relates to the field of capacitive detection technologies, and in particular, to a mutual capacitance detection circuit, a touch chip, and an electronic device.
Background
Mutual capacitance (Mutual Capacitance) is a type of capacitance that is commonly used to describe the capacitive relationship between two or more conductors, and involves the interaction of an electric field between two or more conductors that creates an electric field when a charge changes on one conductor that can affect other conductors in the vicinity, resulting in a change in the distribution of charge on them. Mutual capacitance is widely used in capacitive touch screens.
Referring to fig. 1, fig. 1 shows a conventional mutual capacitance detection circuit. Wherein TX is a mutual capacitance transmitting end, RX is a mutual capacitance receiving end, ctx is a parasitic capacitance of the transmitting end, crx is a parasitic capacitance of the receiving end, cm is a mutual capacitance to be measured, cf is a feedback capacitance, A1 is an operational amplifier, and U1 is an analog-to-digital converter. During detection, the mutual capacitance transmitting end TX outputs a sine wave with the amplitude of A, the sine wave sequentially passes through the mutual capacitance Cm and the mutual capacitance receiving end RX and then is input into the operational amplifier A1, and then the operational amplifier A1 amplifies the sine wave and then converts the amplified sine wave into digital quantity through the analog-to-digital converter U1 for analysis by a subsequent processing circuit.
When a touch signal exists on the capacitive touch screen, the capacitance value of the mutual capacitance Cm is reduced, and at the moment, the voltage signal at the output end of the operational amplifier A1 is also changed, and the voltage change amount is in proportional relation with the capacitance change amount.
By adopting the scheme, when the capacitance value of the mutual capacitance Cm is larger, the operational amplifier A1 is easy to saturate, so that the detection range is reduced, and the detection precision is reduced.
Therefore, how to avoid saturation of the operational amplifier to expand the detection range of the mutual capacitance value is an urgent problem to be solved.
Disclosure of Invention
Based on this, it is necessary to provide a mutual capacitance detection circuit, a touch chip and an electronic device for solving the problems of small mutual capacitance detection range and low detection precision caused by saturation of an operational amplifier in the conventional technology.
In a first aspect, the present application provides a mutual capacitance detection circuit, the circuit comprising: the system comprises a signal sending end, a signal receiving end, a counteracting module and a signal amplifying module;
a mutual capacitor to be tested is connected in series between the signal sending end and the signal receiving end;
The cancellation module comprises a cancellation capacitor, a first switch unit and a switch signal generation unit;
One end of the offset capacitor is connected with the signal receiving end and the input end of the signal amplifying module respectively;
The first switch unit is respectively connected with the other end of the offset capacitor and the switch signal generating unit and is used for connecting the offset capacitor to a first voltage or a ground line according to the switch signal output by the switch signal generating unit;
The first switch unit is also connected with the feedback loop of the signal amplifying module and is used for adjusting the feedback form of the feedback loop according to the switch signal output by the switch signal generating unit.
In one embodiment, the first switching unit includes a first switch, a second switch, and a third switch;
One end of the first switch and one end of the second switch are connected with the other end of the offset capacitor;
The other end of the first switch is connected with the first voltage, and the other end of the second switch is connected with a ground wire;
The third switch is arranged in a feedback loop of the signal amplifying module;
And the control ends of the first switch, the second switch and the third switch are respectively connected with the output end of the switch signal generating unit.
In one embodiment, the signal amplification module includes: an operational amplifier and a feedback loop; the feedback loop comprises a first feedback loop and a second feedback loop;
the non-inverting input end of the operational amplifier is connected with a reference voltage;
The first feedback loop is connected in series between the inverting input end and the output end of the operational amplifier;
the second feedback loop is connected in series between the inverting input end and the output end of the operational amplifier;
The third switch is connected in series with the second feedback loop and is used for controlling the on-off state of the second feedback loop.
In one embodiment, the switching signal generating unit includes: a first generation subunit and a second generation subunit;
The input end of the first generation subunit is connected with an externally input clock signal, and the output end of the first generation subunit is connected with the control end of the third switch;
The input end of the second generation subunit is connected with an externally input clock signal, and the output end of the second generation subunit is respectively connected with the control ends of the first switch and the second switch.
In one embodiment, the switching signal generating unit further includes:
And the input end of the delay subunit is connected with the output end of the second generation subunit, and the output end of the delay subunit is respectively connected with the control ends of the first switch and the second switch.
In one embodiment, the cancellation module further comprises:
And the second switch unit is respectively connected with the signal transmitting end and the switch signal generating unit and is used for connecting the signal transmitting end to the first voltage or the ground according to the switch signal output by the switch signal generating unit.
In one embodiment, the second switching unit includes: a fourth switch and a fifth switch;
One end of the fourth switch and one end of the fifth switch are connected with the signal sending end;
The other end of the fourth switch is connected with the first voltage, and the other end of the fifth switch is connected with a ground wire;
and the control ends of the fourth switch and the fifth switch are respectively connected with the output end of the switch signal generating unit.
In one embodiment, the circuit further comprises:
And the analog-to-digital converter is connected with the output end of the operational amplification module and is used for converting the analog quantity output by the operational amplification module into digital quantity.
In a second aspect, the present application further provides a touch chip, including the mutual capacitance detection circuit in the first aspect.
In a third aspect, the present application also provides an electronic device, including:
The touch screen is arranged on the surface of the display screen; the touch screen is provided with a plurality of mutual capacitors;
The touch chip of the second aspect is connected to the touch screen, and is configured to detect each mutual capacitance according to a touch signal of the touch screen.
The mutual capacitance detection circuit, the touch chip and the electronic equipment have the following advantages:
The application adds a counteracting module based on the prior mutual capacitance detecting circuit. The cancellation module comprises a cancellation capacitor, a first switching unit and a switching signal generation unit, wherein the switching signal generation unit is used for outputting a switching signal, and the first switching unit is used for connecting the cancellation capacitor to a first voltage or a ground wire according to the switching signal. Meanwhile, the first switch unit is also used for adjusting the feedback form of the feedback loop of the signal amplifying module according to the switch signal. By adopting the scheme, the application can counteract the influence of the capacitance value of the mutual capacitance to be detected on the signal amplifying module, and the problems of smaller mutual capacitance detection range and low detection precision caused by the saturation of the signal amplifying module are avoided.
Drawings
The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the application.
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of a conventional mutual capacitance detection circuit;
FIG. 2 is a block diagram of a mutual capacitance detection circuit in one embodiment;
FIG. 3 is a schematic diagram of the wiring of a mutual capacitance detection circuit in one embodiment;
FIG. 4 is a schematic diagram of a switch signal generating unit according to an embodiment;
FIG. 5 is a block diagram of a cancellation module in another embodiment;
FIG. 6 is a block diagram of a mutual capacitance detection circuit in another embodiment;
FIG. 7 is a timing diagram of a mutual capacitance detection circuit in one embodiment;
FIG. 8 is a block diagram of a touch chip in one embodiment;
fig. 9 is a block diagram of an electronic device in one embodiment.
Detailed Description
In order that the application may be readily understood, a more complete description of the application will be rendered by reference to the appended drawings. Preferred embodiments of the present application are shown in the drawings. This application may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and/or" as used herein includes any and all combinations of one or more of the associated listed items.
Where the terms "comprising," "having," and "including" are used herein, another component may also be added unless a specifically defined term is used, such as "consisting of only," "… …," etc. Unless mentioned to the contrary, singular terms may include plural and are not to be construed as being one in number.
It will be understood that, although the terms "first," "second," etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of the present application.
In the present application, unless explicitly specified and limited otherwise, the terms "connected," "coupled," and the like are to be construed broadly, and may be, for example, directly connected or indirectly connected through intermediaries, or may be in communication with each other between two elements or in an interaction relationship between the two elements. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art according to the specific circumstances.
Referring to fig. 2, in some embodiments, the present application provides a mutual capacitance detection circuit, including: the system comprises a signal transmitting end, a signal receiving end, a counteracting module and a signal amplifying module.
The mutual capacitance to be measured is connected in series between the signal transmitting end and the signal receiving end. The signal transmitting end is used for transmitting a detection signal to the mutual capacitance to be detected; the signal receiving end is used for receiving the detection signal after passing through the mutual capacitance to be detected and transmitting the detection signal to the signal amplifying module. The signal amplifying module is used for amplifying the detection signal which is subjected to the mutual capacitance to be detected and is used for subsequent analysis. It should be understood that if the capacitance value of the mutual capacitance to be measured changes due to the presence of the touch signal, the detection signal sent by the signal sending end will carry the information of the capacitance value change after passing through the mutual capacitance to be measured.
Referring to fig. 1, in general, the detection signal is a sine wave, and the signal transmitting terminal TX outputs a sine wave Asin (2pi ft) with an amplitude a, where f represents the frequency of the sine wave, and t represents the time of the sine wave. The sine wave is amplified into a sine wave with the amplitude of ACm/Cf after sequentially passing through a capacitor Cm to be detected, a signal receiving end RX and an operational amplifier A1, and the expression is as follows:
When a touch signal exists on the capacitive touch screen, the capacitance value of the mutual capacitance Cm is reduced to be Cm- Δcm, and then the output voltage expression of the operational amplifier A1 is as follows:
Wherein, the signal quantity caused by the capacitance value change of the mutual capacitance Cm is as follows:
Therefore, the output voltage of the operational amplifier A1 is related to the capacitance of the mutual capacitance to be measured, and if the capacitance of the mutual capacitance to be measured is large, the operational amplifier A1 easily enters a saturated state. Based on the above, the application introduces the offset module between the signal receiving end and the signal amplifying module on the basis of fig. 1, and the offset module is used for offset the influence of the mutual capacitance to be detected on the signal amplifying module when detecting the mutual capacitance, so that the problems of smaller mutual capacitance detection range and low detection precision caused by the saturation of the signal amplifying module are avoided.
With continued reference to fig. 2, specifically, the cancellation module includes a cancellation capacitor, a first switching unit, and a switching signal generating unit.
And one end of the counteracting capacitor is respectively connected with the signal receiving end and the input end of the signal amplifying module, and the other end of the counteracting capacitor is connected with the first switch unit.
And the control end of the first switching unit is connected with the switching signal generating unit and is used for connecting the counteracting capacitor to the first voltage or the ground according to the switching signal output by the switching signal generating unit.
The first switch unit is also connected with the feedback loop of the signal amplifying module and is used for adjusting the feedback form of the feedback loop according to the switch signal output by the switch signal generating unit.
And a switching signal generating unit for converting the input clock signal into a switching signal.
In the above embodiment, by reasonably setting the timing sequence of the switching signal output by the switching signal generating unit, the offset capacitor can be connected to the first voltage or the ground wire and the feedback form of the feedback loop of the signal amplifying module can be adjusted, so that when the mutual capacitance is detected, the offset capacitor is connected to the mutual capacitance detecting circuit to offset the influence of the mutual capacitance to be detected on the signal amplifying module, and the problems of small mutual capacitance detecting range and low detecting precision caused by saturation of the signal amplifying module are avoided.
Referring to fig. 3, optionally, the first switching unit includes a first switch K1, a second switch K2, and a third switch K3.
One end of the first switch K1 and one end of the second switch K2 are connected to the other end of the canceling capacitor Cc. The other end of the first switch K1 is connected to the first voltage AVDD, and the other end of the second switch K2 is connected to the ground. It should be understood that the first voltage AVDD is an operating voltage of the mutual capacitance detection circuit, and specific values thereof can be set according to needs, and the values thereof are not limited in this embodiment. The third switch K3 is disposed in the feedback loop of the signal amplifying module. The control ends of the first switch K1, the second switch K2 and the third switch K3 are respectively connected with the output end of the switch signal generating unit. It should be noted that, the switching signals accessed by the control ends of the first switch K1 and the second switch K2 are reverse signals, that is, when the first switch K1 is turned on, the second switch K2 is turned off; when the first switch K1 is turned off, the second switch K2 is turned on. By adopting the scheme, the connection state of the counteracting capacitor Cc can be grounded or the first voltage; meanwhile, the feedback form of the feedback loop can be adjusted by controlling the on-off of the third switch K3, so that the output of the signal amplifying module is adjusted.
Optionally, the signal amplifying module includes: an operational amplifier A1 and a feedback loop. Wherein the feedback loop comprises a first feedback loop and a second feedback loop.
The noninverting input of the operational amplifier A1 is connected to a reference voltage VCM, wherein the value of the reference voltage VCM is determined according to the operating voltage of the operational amplifier A1.
The first feedback loop and the second feedback loop are both connected in series between the inverting input terminal and the output terminal of the operational amplifier A1, and the third switch K3 is connected in series in the second feedback loop. The feedback form of the feedback loop can be adjusted by controlling the third switch K3 to be turned on or off.
Illustratively, the first feedback circuit includes a feedback capacitor Cf, and at this time, both ends of the feedback capacitor Cf are connected to the inverting input terminal and the output terminal of the operational amplifier A1, respectively.
Specifically, the feedback mode of the feedback loop is adjusted by controlling the third switch K3 to be turned on or off, so that the inverting input terminal and the output terminal of the signal amplifying module are directly connected, or the inverting input terminal and the output terminal are connected through the feedback capacitor Cf. Specifically, when the third switch K3 is turned on, the inverting input terminal and the output terminal of the operational amplifier A1 are shorted, and at this time, the output voltage of the operational amplifier A1 follows the voltage of the inverting input terminal. When the third switch K3 is turned off, the output voltage VOUT of the operational amplifier A1 is fed back to the inverting input terminal through the feedback capacitor Cf, and the gain of the operational amplifier A1 can be adjusted by the operational amplifier A1 according to the feedback signal.
It should be noted that, in order to offset the influence of the mutual capacitance to be measured on the signal amplifying module, the offset capacitance Cc and the feedback capacitance Cf in this embodiment are both adjustable capacitances. Further, in practical applications, the first feedback circuit may further include other feedback devices, such as a feedback resistor.
Referring to fig. 4, optionally, the switching signal generating unit includes: a first generation subunit and a second generation subunit.
The input end of the first generating subunit is connected with an externally input clock signal, and the output end of the first generating subunit is connected with the control end of the third switch K3;
The input end of the second generation subunit is connected with an externally input clock signal, and the output end of the second generation subunit is respectively connected with the control ends of the first switch K1 and the second switch K2.
In this embodiment, the first generating subunit and the second generating subunit adopt frequency dividers, which are used for dividing the frequency of the input clock signal according to preset requirements, so as to output switching signals with different frequencies. It should be noted that, the input clock signal is usually a periodic electrical signal, which may be a square wave or a sine wave, and the reverse control of the first switch K1 and the second switch K2 may be implemented by connecting an inverter before the first switch K1 or the second switch K2.
It will be appreciated that in actual use, other devices having the above functions may also be selected as desired, such as counters, digital signal generators, etc.
Optionally, the switching signal generating unit further includes: and a delay subunit.
The input end of the delay subunit is connected with the output end of the second generation subunit, and the output end of the delay subunit is respectively connected with the control ends of the first switch K1 and the second switch K2.
In this way, the switching signals output by the first generating subunit and the second generating subunit can be distinguished, so as to realize various timing control.
Referring to fig. 5, optionally, the cancellation module further includes: and a second switching unit.
And the second switching unit is respectively connected with the signal transmitting end TX and the switching signal generating unit and is used for connecting the signal transmitting end TX to the first voltage or the ground according to the switching signal output by the switching signal generating unit.
Referring to fig. 3, optionally, the second switching unit includes: a fourth switch K4 and a fifth switch K5.
One end of the fourth switch K4 and one end of the fifth switch K5 are connected to the signal transmitting terminal TX.
The other end of the fourth switch K4 is connected with the first voltage AVDD, and the other end of the fifth switch K5 is connected with the ground wire.
The control ends of the fourth switch K4 and the fifth switch K5 are respectively connected with the output end of the switch signal generating unit.
Specifically, the switching signals accessed by the control ends of the fourth switch K4 and the fifth switch K5 are reverse signals, that is, when the fourth switch K4 is turned on, the fifth switch K5 is turned off; when the fourth switch K4 is turned off, the fifth switch K5 is turned on. With this arrangement, the signal transmitting terminal TX can be connected to the first voltage or the ground line according to the switching signal output from the switching signal generating unit.
It should be noted that, the control end signals of the first switch K1 and the fifth switch K5 are the same direction signals, that is, the first switch K1 and the fifth switch K5 are turned on or off at the same time. The control end signals of the second switch K2 and the fourth switch K4 are the same-direction signals, namely the second switch K2 and the fourth switch K4 are turned on or turned off simultaneously. By adopting the scheme, the structural difficulty of the switch signal generating unit is reduced, and the on/off of each switch in the switch unit can be realized through two switch signals.
Referring to fig. 3 and fig. 6, in some embodiments, the mutual capacitance detection circuit provided by the present application further includes: analog-to-digital converter U1.
The analog-to-digital converter U1 comprises an input and an output. The input end of the analog-to-digital converter U1 is connected with the output end of the operational amplification module, and the output end of the analog-to-digital converter U1 is connected with a subsequent processor and is used for converting the analog quantity output by the operational amplification module into a digital quantity for analysis and processing by the processor of a subsequent circuit. Specifically, the input end of the analog-to-digital converter U1 is connected to the output end of the operational amplifier A1 of the operational amplifier module.
Referring to fig. 3 and 7, in order to fully understand the present application, the following describes the operation principle of the mutual capacitance detection circuit of the present application with reference to fig. 3 and 7. Fig. 7 shows a timing diagram of the mutual capacitance detection circuit of the present application, and fig. 7 shows 2 complete duty cycle timings. The control end signals of the first switch K1 and the fifth switch K5 are the same-direction signals, the control end signals of the second switch K2 and the fourth switch K4 are the same-direction signals, and the control end signals of the first switch K1 and the second switch K2 are the reverse signals.
At time t 0-t 1, the first switch K1, the third switch K3 and the fifth switch K5 are turned on, the second switch K2 and the fourth switch K4 are turned off, at this time, the cancellation capacitor Cc is connected to the first voltage AVDD, the feedback loop of the operational amplifier A1 is shorted by the third switch K3, the signal transmitting end TX is grounded, and the charge amounts on the capacitors are respectively:
QCm＝VCMCm
QCc＝(VCM-AVDD)CC
QCf＝0
the output voltage V OUT＝VCM of the operational amplifier A1.
Wherein V CM is the reference voltage of the operational amplifier A1;
Q Cm is the charge amount of the mutual capacitance Cm to be measured, and C m is the capacitance value of the mutual capacitance Cm to be measured;
Q Cc is the charge amount of the canceling capacitor Cc, and C c is the capacitance value of the canceling capacitor Cc;
Q Cf is the charge amount of the feedback capacitor Cf.
At time t 1-t 2, the first switch K1, the third switch K3 and the fifth switch K5 are turned off, the second switch K2 and the fourth switch K4 are turned on, at this time, the counteracting capacitor Cc is grounded, the feedback loop of the operational amplifier A1 is connected to the feedback capacitor Cf, the signal transmitting end TX is connected to the first voltage AVDD, and the electric charge amounts on the capacitors are respectively:
QCm＝(VCM-AVDD)Cm
QCc＝VCMCC
QCf＝(VCM-VOUT)Cf
according to conservation of charge:
VCMCm+(VCM-AVDD)CC＝(VCM-AVDD)Cm+VCMCC+(VCM-VOUT)Cf
The expression for obtaining the output voltage V OUT of the operational amplifier A1 is:
If the following steps are made:
AVDD(Cc-Cm)＝0
Namely:
Cc＝Cm
At this time, the output voltage V OUT＝VCM of the operational amplifier A1.
When the capacitance value of the mutual capacitance Cm to be measured changes from Cm to Cm- Δcm, the output voltage of the operational amplifier A1 is V OUT1, and the expression of V OUT1 is:
Namely, the signal quantity caused by the capacitance change is as follows:
At time t 2-t 3, the second switch K2, the third switch K3 and the fourth switch K4 are turned on, the first switch K1 and the fifth switch K5 are turned off, at this time, the counteracting capacitor Cc is grounded, the feedback loop of the operational amplifier A1 is shorted, the signal transmitting terminal TX is connected to the first voltage AVDD, and the charge amounts on the capacitors are respectively:
QCm＝(VCM-AVDD)Cm
QCc＝VCMCC
QCf＝0
the output voltage V OUT＝VCM of the operational amplifier A1.
At time t 3-t 4, the second switch K2, the third switch K3 and the fourth switch K4 are turned off, the first switch K1 and the fifth switch K5 are turned on, at this time, the cancellation capacitor Cc is connected to the first voltage AVDD, the feedback loop of the operational amplifier A1 is connected to the feedback capacitor Cf, the signal transmitting end TX is grounded, and the electric charge amounts on the capacitors are respectively:
QCm＝VCMCm
QCc＝(VCM-AVDD)CC
QCf＝(VCM-VOUT)Cf
according to conservation of charge:
(VCM-AVDD)Cm+VCMCC＝VCMCm+(VCM-AVDD)CC+(VCM-VOUT)Cf
The expression for obtaining the output voltage VOUT of the operational amplifier A1 is:
If the following steps are made:
CC＝Cm
At this time, the output voltage V OUT＝VCM of the operational amplifier A1.
When the capacitance of the mutual capacitance Cm changes from Cm to Cm- Δcm, the output voltage V OUT1 of the operational amplifier A1 is expressed as:
Namely, the signal quantity caused by the capacitance change is as follows:
The peak-to-peak value of DeltaV OUT after the above operation is:
When a touch signal is present, the peak-to-peak value will change, and if the change is detected, the presence of the touch signal can be determined.
By the mode, the output voltage of the operational amplifier A1 is irrelevant to the capacitance value of the mutual capacitance to be detected, so that the influence of the mutual capacitance to be detected on the signal amplifying module is counteracted, and the problems of small mutual capacitance detection range and low detection precision caused by saturation of the signal amplifier are avoided.
Further, the output voltage of the operational amplifier A1 is connected to the input end of the analog-to-digital converter U1, and the embodiment of the application converts the variable quantity of the mutual capacitance into the variable quantity of the voltage, and the variable quantity of the voltage is proportional to the variable quantity of the mutual capacitance, and the voltage is converted into the digital quantity by the analog-to-digital converter U1 and then is transmitted to the processor for subsequent judgment.
The mutual capacitance detection circuit is provided with the offset module on the basis of the existing mutual capacitance detection circuit. The cancellation module comprises a cancellation capacitor, a first switching unit and a switching signal generation unit, wherein the switching signal generation unit is used for outputting a switching signal, and the first switching unit is used for connecting the cancellation capacitor to a first voltage or a ground wire according to the switching signal. Meanwhile, the first switch unit is also used for adjusting the feedback form of the feedback loop of the signal amplifying module according to the switch signal. By adopting the scheme, the application can counteract the influence of the capacitance value of the mutual capacitance to be detected on the signal amplifying module, and the problems of smaller mutual capacitance detection range and low detection precision caused by the saturation of the signal amplifying module are avoided.
Referring to fig. 8, in some embodiments, the present application further provides a touch chip including the mutual capacitance detection circuit provided in the above embodiments.
Referring to fig. 9, in some embodiments, the present application further provides an electronic device, including: display screen, touch-sensitive screen, touch-control chip.
The touch screen is arranged on the surface of the display screen, a plurality of mutual capacitances are arranged on the touch screen, and when a user touches the touch screen and generates a touch signal, the capacitance value of each mutual capacitance changes.
The touch chip provided in the above embodiment is adopted. The touch screen is connected with the touch screen and used for detecting each mutual capacitance according to a touch signal of the touch screen.
The technical features of the above embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.
The foregoing examples illustrate only a few embodiments of the application and are described in detail herein without thereby limiting the scope of the application. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the application, which are all within the scope of the application. Accordingly, the scope of the application should be assessed as that of the appended claims.
Claims (10)
1. A mutual capacitance detection circuit, the circuit comprising: the system comprises a signal sending end, a signal receiving end, a counteracting module and a signal amplifying module;
a mutual capacitor to be tested is connected in series between the signal sending end and the signal receiving end;
The cancellation module comprises a cancellation capacitor, a first switch unit and a switch signal generation unit;
One end of the offset capacitor is connected with the signal receiving end and the input end of the signal amplifying module respectively;
The first switch unit is respectively connected with the other end of the offset capacitor and the switch signal generating unit and is used for connecting the offset capacitor to a first voltage or a ground line according to the switch signal output by the switch signal generating unit;
The first switch unit is also connected with the feedback loop of the signal amplifying module and is used for adjusting the feedback form of the feedback loop according to the switch signal output by the switch signal generating unit.
2. The mutual capacitance detection circuit of claim 1, wherein the first switching unit comprises a first switch, a second switch, and a third switch;
One end of the first switch and one end of the second switch are connected with the other end of the offset capacitor;
The other end of the first switch is connected with the first voltage, and the other end of the second switch is connected with a ground wire;
The third switch is arranged in a feedback loop of the signal amplifying module;
And the control ends of the first switch, the second switch and the third switch are respectively connected with the output end of the switch signal generating unit.
3. The mutual capacitance detection circuit of claim 2, wherein the signal amplification module comprises an operational amplifier and a feedback loop; the feedback loop includes a first feedback loop and a second feedback loop;
the non-inverting input end of the operational amplifier is connected with a reference voltage;
The first feedback loop is connected in series between the inverting input end and the output end of the operational amplifier;
the second feedback loop is connected in series between the inverting input end and the output end of the operational amplifier;
The third switch is connected in series with the second feedback loop and is used for controlling the on-off state of the second feedback loop.
4. The mutual capacitance detection circuit according to claim 2, wherein the switching signal generation unit includes: a first generation subunit and a second generation subunit;
The input end of the first generation subunit is connected with an externally input clock signal, and the output end of the first generation subunit is connected with the control end of the third switch;
The input end of the second generation subunit is connected with an externally input clock signal, and the output end of the second generation subunit is respectively connected with the control ends of the first switch and the second switch.
5. The mutual capacitance detection circuit according to claim 4, wherein the switching signal generation unit further includes:
And the input end of the delay subunit is connected with the output end of the second generation subunit, and the output end of the delay subunit is respectively connected with the control ends of the first switch and the second switch.
6. The mutual capacitance detection circuit of claim 1, wherein the cancellation module further comprises:
And the second switch unit is respectively connected with the signal transmitting end and the switch signal generating unit and is used for connecting the signal transmitting end to the first voltage or the ground according to the switch signal output by the switch signal generating unit.
7. The mutual capacitance detection circuit of claim 6, wherein the second switching unit comprises: a fourth switch and a fifth switch;
One end of the fourth switch and one end of the fifth switch are connected with the signal sending end;
The other end of the fourth switch is connected with the first voltage, and the other end of the fifth switch is connected with a ground wire;
and the control ends of the fourth switch and the fifth switch are respectively connected with the output end of the switch signal generating unit.
8. The mutual capacitance detection circuit of claim 1, wherein the circuit further comprises:
And the analog-to-digital converter is connected with the output end of the operational amplification module and is used for converting the analog quantity output by the operational amplification module into digital quantity.
9. A touch chip comprising the mutual capacitance detection circuit of any one of claims 1-8.
10. An electronic device, comprising:
The touch screen is arranged on the surface of the display screen; the touch screen is provided with a plurality of mutual capacitors;
the touch chip of claim 9, coupled to the touch screen, for detecting each of the mutual capacitances based on a touch signal of the touch screen.
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| CN202323101642.4U CN221100907U (en) | 2023-11-16 | 2023-11-16 | Mutual capacitance detection circuit, touch chip and electronic equipment |
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| CN202323101642.4U CN221100907U (en) | 2023-11-16 | 2023-11-16 | Mutual capacitance detection circuit, touch chip and electronic equipment |
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