CN114487784A - Capacitance detection circuit, touch chip and electronic equipment - Google Patents
Capacitance detection circuit, touch chip and electronic equipment Download PDFInfo
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- CN114487784A CN114487784A CN202210146748.7A CN202210146748A CN114487784A CN 114487784 A CN114487784 A CN 114487784A CN 202210146748 A CN202210146748 A CN 202210146748A CN 114487784 A CN114487784 A CN 114487784A
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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- G—PHYSICS
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Abstract
The utility model provides a capacitance detection circuit, touch-control chip and electronic equipment, can reduce the influence of display interference to capacitance detection circuit, reduce the passageway gain for capacitance detection circuit's interference immunity is stronger. The capacitance detection circuit comprises a control module, a first driving module, a charge transfer module and a processing module; the control module is used for controlling the first driving module to output a driving signal; the first driving module outputs a driving signal to a self-capacitor through a first switch, a second switch, a first current source and a second current source to charge and discharge the self-capacitor, the charge transfer module is used for converting the charge of the self-capacitor to generate an output voltage, and the output voltage is related to a capacitance value of the self-capacitor; the processing module is connected with the output end of the charge transfer module and used for determining the capacitance value of the self-capacitance according to the output voltage.
Description
Technical Field
The application relates to the technical field of touch control, in particular to a capacitance detection circuit, a touch control chip and electronic equipment.
Background
In the field of capacitive touch, capacitive detection is the key to achieving touch detection. When a conductor such as a finger approaches or touches the detection electrode, the capacitance corresponding to the detection electrode changes, and by detecting the change amount of the capacitance, the information that the finger approaches or touches the detection electrode can be acquired, so as to determine the operation of the user.
In the prior art, a self-capacitance detection circuit works in a detection cycle at a plurality of time intervals, a capacitor to be detected is firstly counteracted by adopting a counteracting capacitor in the former time interval, and then the capacitor is detected in the latter time interval, namely, the self-capacitance detection in the prior art is usually carried out at discrete time.
For a screen of an electronic device, a display layer of the screen may generate large noise interference when scanning, a data line between a main control unit and a control unit, a data line connected between the display control unit and the display screen, for example, an interference signal generated by a Low-Voltage Differential Signaling (Lvds) data line to touch, and interference caused by data structure inversion to a touch key signal may easily saturate a channel, and since an output of a capacitance detection circuit of a discrete-time capacitance detection scheme is strongly correlated with a phase of the interference signal, a phase of the channel may be inconsistent, so that the interference cannot be removed by an algorithm in a post-processing, and the phase inconsistency of each channel may cause channel saturation more easily, thereby causing inaccurate capacitance detection and affecting the comprehensive performance of the capacitance detection circuit.
Disclosure of Invention
The application provides a capacitance detection circuit, touch chip and electronic equipment, can reduce the influence that shows the interference to capacitance detection circuit, reduce the passageway gain for capacitance detection circuit's interference immunity is stronger.
In a first aspect, a capacitance detection circuit is provided, which is used for detecting a self-capacitance in a touch screen, and includes a control module, a first driving module, a charge transfer module, and a processing module;
the control module is used for controlling the first driving module to output a driving signal;
the first driving module is provided with a first switch, a second switch, a first current source and a second current source, power supply voltage supplies power to the first current source, the second current source is grounded, the first switch and the second switch are positioned between the first current source and the second current source, and the output end of the first driving module is positioned between the first switch and the second switch; the output end of the first driving module outputs a driving signal to the touch screen for detecting the self-capacitance of the touch screen;
the output end of the first driving module is connected with the charge transfer module and is used for converting the charges of the self-capacitor to generate an output voltage, and the output voltage is related to the capacitance value of the self-capacitor; and
the processing module is connected with the output end of the charge transfer module and used for determining the capacitance value of the self-capacitance according to the output voltage.
In a possible implementation manner, the first driving module charges the self-capacitor through the first current source and the first switch; the self-capacitance discharges through the second switch and the second current source.
In one possible implementation manner, the control module controls the first switch and the second switch to be turned on at different times through a reverse non-overlapping timing sequence so that the first driving module outputs the driving signal.
In one possible implementation, one detection cycle in which the reverse non-overlapping timing controls the first switch and the second switch to not be turned on at the same time includes four phases, wherein,
in the first stage, the first switch is controlled to be closed and the second switch is controlled to be opened, the first current source charges the self-capacitor, and the voltage of the output end of the first driving module rises to a peak;
in the second stage, the first switch and the second switch are controlled to be switched off, and the voltage of the output end of the first driving module is kept unchanged;
in the third stage, the first switch is controlled to be opened and the second switch is controlled to be closed, the self-capacitance discharges through the second current source, and the voltage of the output end of the first driving module is reduced to a wave trough;
a fourth stage, controlling the first switch to be switched off and the second switch to be switched off, wherein the voltage of the output end of the first driving module is kept unchanged;
and repeating the four stages to control the first driving module to output the square-wave-like signal.
In one possible implementation, the one detection cycle in which the reverse non-overlapping timing controls the first switch and the second switch to be not simultaneously turned on includes two phases, wherein,
in the first stage, the first switch is controlled to be closed and the second switch is controlled to be opened, the first current source charges the self-capacitor, and the voltage of the output end of the first driving module rises to a peak;
in the second stage, the first switch is controlled to be switched off and the second switch is controlled to be switched on, the self-capacitance discharges through the second current source, and the voltage of the output end of the first driving module is reduced to a wave trough;
and repeating the two stages to control the first driving module to output the triangle wave-like signal.
In one possible implementation, the charge transfer module is a differential voltage follower.
In a possible implementation manner, a positive phase input end of the differential voltage follower is connected to an output end of the first driving module, an output end of the differential voltage follower is connected to a negative phase input end of the differential voltage follower, so that an output voltage follows an input voltage, and a voltage gain of the differential voltage follower is 1.
In a possible implementation manner, the touch panel further includes a second driving module, an output end of the second driving module outputs a driving signal to the touch screen for detecting a mutual capacitance of the touch screen, and a capacitance value of the mutual capacitance is detected through common voltage division of the mutual capacitance and the self-capacitance.
In a possible implementation manner, the second driving module is connected to a first end of the mutual capacitor, and a second end of the mutual capacitor is connected to a first end of the self capacitor and an input end of the charge transfer module;
the control module controls the first switch and the second switch to be switched off simultaneously, so that the capacitance detection circuit is used for detecting the mutual capacitance in the touch screen.
In one possible implementation, the processing module is an analog-to-digital conversion ADC circuit.
In one possible implementation manner, the self-capacitance is the self-capacitance of each electrode of the touch screen to the ground.
In one possible implementation manner, the mutual capacitance is a mutual capacitance between any two electrodes in the transverse direction and the longitudinal direction of the touch screen.
In a second aspect, a touch chip is provided, which includes the capacitance detection circuit in any possible implementation manner of the first aspect.
In a third aspect, an electronic device is provided, including: a display screen; the touch screen is arranged on the surface of the display screen; and the touch chip according to the second aspect realizes a touch display function.
Based on above-mentioned scheme, thereby the electric capacity detection circuitry of this application utilizes first, second current source and first, second switch to combine to carry out the self-capacitance detection that charges and discharge the touch-sensitive screen to through the first, second switch of disconnection can be simple convenient carry out mutual capacitance and detect the switching, and this electric capacity detection circuitry can reduce the passageway gain, makes the passageway be difficult to the saturation, improves electric capacity detection circuitry's wholeness ability.
Drawings
Fig. 1 is a schematic diagram of a possible application scenario of a capacitance detection circuit according to an embodiment of the present application.
FIG. 2 is a schematic diagram of a capacitance detection circuit according to an embodiment of the present application.
Fig. 3 is a schematic diagram of a differential voltage follower of a capacitance detection circuit providing a dc bias voltage according to an embodiment of the present application.
Fig. 4 is a schematic diagram of an equivalent circuit of self-capacitance detection according to an embodiment of the present application.
FIG. 5 is a schematic diagram of an equivalent circuit for mutual capacitance detection according to an embodiment of the present application.
Fig. 6 is a square wave coding process in a self-capacitance detection equivalent circuit according to an embodiment of the present application.
Fig. 7 is a triangular wave coding process in a self-capacitance detection equivalent circuit according to an embodiment of the present application.
Detailed Description
First, a schematic diagram of a possible application scenario of the capacitance detection circuit according to the embodiment of the present application is described with reference to fig. 1.
While two layers of channels in the touch screen are shown in fig. 1, a capacitive touch system using such a pattern can typically employ both self-capacitance and mutual capacitance detection. During self-capacitance detection, the touch control chip scans the change condition of the self-capacitance of each transverse channel and each longitudinal channel to the ground. When a finger is close to or touching, the self-capacitance of the channel near the finger becomes large. For example, as shown in FIG. 1, the finger and its nearby cross channel Rx3 will generate a capacitance Cs, and the finger and its nearby vertical channel Tx2 will generate a capacitance Cd. For example, when a finger approaches the driving channel Tx2 and the sensing channel Rx3, since a human body is connected to the system ground as a conductor, the capacitance of the driving channel Tx2 to the system ground becomes CTx2+ Cd, and the capacitance of the sensing channel Rx3 to the system ground becomes CRx3+ Cs. The touch chip can obtain touch information of the finger according to the detected change of the self-capacitance. When mutual capacitance detection is carried out, the change of the mutual capacitance between the transverse channel and the longitudinal channel is detected. For example, as shown in fig. 1, mutual capacitance is generated between the horizontal channel Rx3 and the vertical channel Tx2 near the finger, and the touch chip can obtain touch information of the finger according to a detected change of the mutual capacitance between the horizontal channel and the vertical channel. Here, the horizontal channel in fig. 1 is referred to as an Rx channel, the vertical channel is referred to as a Tx channel, and the horizontal channel and the vertical channel in the touch screen may also be referred to as a detection electrode or a sensor (sensor).
In general, the capacitor to be tested of the capacitance detection circuit comprises a self capacitance of each electrode to the ground in the touch screen and a mutual capacitance between the two electrodes, and the capacitance of the capacitor to be tested comprises a basic capacitance Cx and a capacitance variation quantity Δ Cx relative to the basic capacitance Cx. When no finger touches or approaches, the detected capacitance of the capacitor to be detected is the basic capacitance Cx; when a finger is close to or touches the touch panel, the capacitance of the capacitor to be detected changes relative to the base capacitance Cx on the basis of the base capacitance Cx, and therefore the detected capacitance of the capacitor to be detected includes the base capacitance Cx and a capacitance change amount Δ Cx, wherein the capacitance change amount Δ Cx actually reflects the touch information of the user.
In an embodiment, the capacitance detection circuit is specifically configured on the touch chip 101 of fig. 1, and therefore, it can be understood that the touch chip 101 includes the capacitance detection circuit described in the following embodiments.
In general, a capacitance detection circuit includes a front-end circuit for data detection and a back-end circuit for data processing.
Fig. 2 is a schematic diagram of a capacitance detection circuit according to an embodiment of the present application. The capacitance detection circuit can be used to detect self and/or mutual capacitance in a touch screen. In particular, it can be used to detect respectively the capacitors C to be testedmOr CLA capacity change amount of (2), wherein CmIs the mutual capacitance between two detection electrodes in the touch screen, CLThe self-capacitance of each detection electrode in the touch screen to the ground.
Referring to fig. 2, the capacitance detection circuit includes: the control module 201 and the driving module comprise a first driving module 203 and a second driving module 202, a charge transfer module 204 and a processing module 205; the capacitance detection circuit can be switched to a self-capacitance detection mode or a mutual capacitance detection mode.
The driving module is used for generating a driving signal or a code printing signal. Specifically, the driving module is connected to the capacitor to be tested and is configured to output a driving signal to the capacitor to be tested. Specifically, the driving module includes a first driving module 203 and a second driving module 202, where the first driving module 203 is configured to detect a mutual capacitance and output a driving signal, and the second driving module 202 is configured to detect a self-capacitance and output a driving signal.
Practically, the second driving module 202 is specifically a square wave signal; the first driving module 203 is specifically a current source ILp、ILnAnd the control module 201 controls the on and off of the switches K1 and K2 by using a reverse non-overlapping clock time sequence, so as to control the first driving module 203 to output a square-wave-like or triangular-wave-like driving signal.
The charge transfer module 204 is connected to the capacitor to be tested, and is configured to convert the charge of the capacitor to be tested to generate an output voltage VoutSaid output voltage VoutRelating to the capacitance value to be measured; the charge transfer module is a differential voltage followerOPA), as shown with reference to fig. 3, by the supply voltage VCMAnd a resistance RbA differential voltage follower consisting of an operational amplifier is provided with a DC Bias. Specifically, the positive phase terminal of the differential voltage follower and the capacitor C to be testedmOr CLAnd a feedback is formed between the output end and the negative phase end, so that the output follows the input and the voltage gain of the output is 1.
The processing module 205 is connected to the charge transfer module 204 for outputting the output voltage VoutAnd determining the capacitance value of the capacitor to be measured before and after being influenced by the external electric field. Specifically, the processing module 205 is an analog-to-digital converter ADC circuit, and is configured to convert the voltage signal output by the charge transfer module 204 into a digital signal.
The switching of the capacitance detection circuit into the self-capacitance detection mode or the mutual-capacitance detection mode specifically includes: under the self-capacitance detection mode, the control module 201 adopts a reverse non-overlapping time sequence to control the first switch K1 and the second switch K2 not to be conducted at the same time, and the first driving module 203 and the capacitor C to be detectedLConnected to the capacitor C to be measuredLAnd outputting a driving signal, and fig. 4 is a schematic diagram of a self-capacitance detection equivalent circuit according to an embodiment of the present application. In the mutual capacitance detection mode, the control module 201 controls the first switch K1 and the second switch K2 to be turned off simultaneously, and the second driving module 202 and the capacitor C to be tested are connected to each othermConnected to the capacitor C to be measuredmAnd outputting a driving signal, and fig. 5 is a schematic diagram of an equivalent circuit for mutual capacitance detection according to an embodiment of the present application.
The self capacitance detection equivalent circuit of fig. 4 and the mutual capacitance detection equivalent circuit of fig. 5 will be described in detail below, respectively.
As shown in fig. 4, the self capacitance detection equivalent circuit includes a control module 401, a first driving module 403, a charge transfer module 404, and a processing module 405.
The charge transfer module 404 is connected to the capacitor to be tested, and is configured to convert the charge of the capacitor to be tested to generate an output voltage VoutSaid output voltage VoutRelating to the capacitance value to be measured; the charge transfer module 404 is embodied as a differential voltage follower (OPA). In particular, the differential voltagePositive phase end of follower and capacitor C to be testedLAnd a feedback is formed between the output end and the negative phase end, so that the output follows the input and the voltage gain of the output is 1.
The processing module 405 is connected to the charge transfer module 404 for determining the output voltage VoutAnd determining the capacitance value of the capacitor to be measured before and after being influenced by the external electric field. Specifically, the processing module 405 is an analog-to-digital converter ADC circuit, and is configured to convert the voltage signal output by the charge transfer module 404 into a digital signal.
The first driving module 403 includes a first switch K1 and a second switch K2. The control module 401 generates the driving signal from the capacitance detection circuit by controlling the first switch K1 and the second switch K2 of the first driving module 403 to be turned on at different times, and specifically, the control module 401 controls the first switch K1 and the second switch K2 to be turned on at different times by using a reverse non-overlapping timing.
The first driving module 403 has a first switch K1 and a second switch K2, and a first current source ILpAnd a second current source ILnThe first current source ILpIs connected to a supply voltage Vcc, the first current source ILpIs connected to a first terminal of a first switch K1, a second terminal of the first switch K1 is connected to a first terminal of a second switch K2, a second terminal of the second switch K2 is connected to a second current source ILnThe first terminal of (1), the second current source ILnIs connected to ground GND, wherein the second terminal of the first switch K1 is the output terminal of the first driving module 403. The first driving module 403 passes through the first current source ILpAnd the first switch K1 charges the self-capacitance; the self-capacitance passes through the second switch K2 and the second current source ILnAnd (4) discharging.
The output end of the first driving module 403 and the self-capacitor CLIs connected to the non-inverting input of the charge transfer module 404, the self-capacitance CLThe second end of the first switch is connected to the ground GND;
it should be understood that the first drive module 403 is comprised ofA first current source ILpAnd a second current source ILnAnd the first switch unit K1 and the second switch unit K2 are connected in series. The output terminal of the first driving module 403 is connected to the non-inverting input terminal of the charge transfer module 404 and the self-capacitance CLA second terminal of the self-capacitance is connected to ground GND. Output terminal of the first driving module 403 and the capacitor C to be testedLConnected to output a drive signal via a pair of capacitors CLAnd charging and discharging to finish the detection process of the self-capacitance.
By means of a current source generating a voltage to the capacitor CLCharging and discharging to make charging and discharging current constant and free from CLThe parasitic resistance of (2). And a current source is adopted to supply a capacitor CLCharging and discharging, outputting voltage V in capacitance detection periodoutFollow input VinThe capacitance detection circuit realizes capacitance detection in continuous time, the output of the capacitance detection circuit is not affected by the phase of an interference signal, the channel gain is small, and the comprehensive performance of the capacitance detection circuit is improved.
As an alternative implementation manner, the on-off of the first switch K1 and the second switch K2 is controlled by an inverse non-overlapping timing sequence, so that square-wave-like self-capacitance code printing driving can be realized. Specifically, one detection cycle in which the reverse non-overlapping timing controls the first switch K1 and the second switch K2 not to be turned on simultaneously includes four phases, referring to fig. 6(a) - (d) the square wave coding process:
the first stage is as follows: the first switch K1 is controlled to be closed and the second switch K2 is controlled to be opened through the first current source IxpTo self-capacitance CLCharging, the output voltage of the first driving module 403/the input voltage Vin of the charge transfer module 404 rises to the peak;
and a second stage: the first switch K1 is controlled to be turned off and the second switch K2 is controlled to be turned off, and the output voltage of the first driving module 403/the input voltage Vin of the charge transfer module 404 is kept unchanged;
and a third stage: the first switch K1 is controlled to be opened and the second switch K2 is controlled to be closed, and the self-capacitance CLBy a second current source IxnDischarging, the input voltage Vin of the output voltage/charge transfer module 404 of the first driving module 403 falls to the trough;
a fourth stage: k2 is kept off, and the input voltage Vin is kept unchanged; the first switch K1 is controlled to be turned off and the second switch K2 is controlled to be turned off, and the output voltage of the first driving module 403/the input voltage Vin of the charge transfer module 404 is kept unchanged;
by continuously performing the above timing control on the switches K1 and K2, the first driving module 403 can be controlled to output a square-wave-like code printing driving signal, so as to realize square-wave-like code printing driving.
As another alternative implementation, the triangular wave-like self-capacitance code printing driving can be realized by controlling the on and off of the first switch K1 and the second switch K2 through reverse non-overlapping timing. Specifically, one detection cycle in which the reverse non-overlapping timing controls the first switch K1 and the second switch K2 not to be turned on at the same time includes two stages, referring to the triangular wave coding process of fig. 7(a) - (d):
the first stage is as follows: the first current source I controls the first switch K1 to be closed and the second switch K2 to be openedxpTo self-capacitance CLCharging, the output voltage of the first driving module 403/the input voltage Vin of the charge transfer module 404 rises to the peak;
in the second stage, the first switch K1 is controlled to be opened and the second switch K2 is controlled to be closed, and the self-capacitance CLBy a second current source IxnDischarging, the input voltage Vin of the output voltage/charge transfer module 404 of the first driving module 403 falls to the trough;
fig. 7(c) - (d) repeat the processes of fig. 7(a) - (b), and the first driving module 403 outputs the triangle wave-like coding driving signal by continuously and repeatedly implementing the above-mentioned timing control to the switches K1, K2, thereby realizing the triangle wave-like coding driving.
Generating a voltage-to-capacitance C using a current source in a self-capacitance detection equivalent circuit as shown in FIG. 4LCharging and discharging to carry out CLAnd (4) detecting a capacitance value. Specifically, the amplitude amp value, the charging and discharging time t and the current source I of the square-like wave or the triangular-like wave measured by the self-capacitance detection circuit can be usedxp、IxnInverse calculation CLThe calculation reference formula includes:
the self-capacitance detection circuit controls the first switch K1 and the second switch K2 to be switched on at different times through the reverse non-overlapping clock so as to not switch in the first current source I at the same timexpAnd a second current source IxnAnd then to the capacitor CLIn the process of self-capacitance detection during charging and discharging, C is usedLIs directly connected with the charge transfer module and outputs a voltage V in the capacitance detection periodoutFollow input VinAnd the output in the coding detection period is complete and continuously follows the input, so that the interference of a time sequence is eliminated, the output of the self-capacitance detection circuit is irrelevant to the phase of a display interference signal, and the capacitance is detected in continuous time, so that the consistency of channel phases can be improved, the channel saturation is further prevented, and the performance of the capacitance detection circuit is improved.
The self-capacitance detection circuit is not conducted at the same time to C except by controlling K1 and K2LOutside carrying out charge-discharge and accomplishing self-capacitance detection process, can also break off simultaneously through control K1, K2 for the disconnection of first drive module, beat the sign indicating number drive on mutual capacitance through second drive module, make electric capacity detection circuitry is arranged in detecting the touch-sensitive screen mutual capacitance. Therefore, self-capacitance detection and mutual capacitance detection can be integrated in the same capacitance detection circuit, the circuit structure is simpler, and the cost is reduced.
Furthermore, the capacitance detection circuit further comprises a second driving module, and the second driving module is connected with a mutual capacitor CmThe first terminal of, the mutual capacitance CmIs connected to the first terminal of the self-capacitance and the input terminal of the charge transfer module.
As shown in fig. 5, the mutual capacitance detection equivalent circuit includes a control module 501, a second driving module 502, a charge transfer module 504 and a processing module 505.
The control module 501 controls the first switch K1 and the second switch K2 to be turned off simultaneously for mutual capacitance detection.
The charge transfer module 504 is connected to the capacitor to be tested, and is used for converting the charge of the capacitor to be testedBecomes an output voltage VoutSaid output voltage VoutRelating to the capacitance value to be measured; the charge transfer module is embodied as a differential voltage follower (OPA). Specifically, the positive phase terminal of the differential voltage follower is connected to the capacitor C to be testedm、CLAnd a feedback is formed between the output end and the negative phase end, so that the output follows the input and the voltage gain of the output is 1.
The processing module 505 is connected to the charge transfer module 504 for converting the output voltage V into an output voltage VoutAnd determining the capacitance value of the capacitor to be measured before and after being influenced by the external electric field. Specifically, the processing module 505 is an analog-to-digital converter ADC circuit, and is configured to convert the voltage signal output by the charge transfer module 504 into a digital signal.
The output end of the second driving module 502 is connected to the mutual capacitor CmThe first terminal of, the mutual capacitance CmIs respectively connected to the non-inverting input terminal of the charge transfer module 504 and the self-capacitance CLThe first terminal of (C), the self-capacitanceLIs connected to ground, the second driving module 502 outputs a square wave driving signal VtxThrough said mutual capacitance CmAnd said self-capacitance CLCommon voltage division detection of the mutual capacitance CmThe capacitance value of (2).
Specifically, the second driving module 502 outputs a square wave driving signal VtxCapacitor C to be measuredmAnd CLThe two capacitors share the voltage division, so the voltage V input by the differential voltage followerinComprises the following steps:
due to the differential voltage follower output voltage VoutFollowing the input voltage VinThus, C can be calculated from the actual measurement values in the no-touch and touch statesmWherein the self-capacitance C is further requiredLCalculating the mutual capacitance CmThe capacitance value of (2).
Mutual capacitance detection equivalent electricity as shown in FIG. 5Front-end circuit of circuit CmAnd CLTwo capacitors are used for voltage division, and mutual capacitance C is detected and calculated by adopting a capacitive voltage division modemDue to self-capacitance CLRelatively large, so that the divided voltage is small, the circuit voltage attenuation is large, and the voltage V input by the differential voltage follower in the circuit is largeinThe voltage gain of the differential voltage follower is unit gain, namely gain is 1, so that the channel gain is relatively reduced to be lower by the mutual capacitance detection circuit. When display interference exists on the screen, the interference signal serving as an input signal is divided, so that the attenuation of the interference signal input into the back-end circuit is large, and the capacitance detection circuit has larger interference tolerance. Therefore, the mutual capacitance detection circuit is relatively low in channel gain, not easy to saturate in a channel, high in capacitance detection accuracy and high in anti-interference performance.
The capacitance detection scheme of this application is gone on in succession in a capacitance detection cycle, continuous time capacitance detection promptly for detection circuitry is irrelevant with the phase place that the touch-sensitive screen shows the interference, and the problem of the passageway saturation that the passageway phase place nonconformity leads to when can solving the demonstration interference, and also can reduce the passageway gain wholly, and the passageway is difficult to saturate, improves capacitance detection circuitry's accuracy.
The self/mutual capacitance detection circuit integrates self capacitance detection and mutual capacitance detection in the same circuit, and is simpler in circuit structure and lower in cost.
The embodiment of the application also provides a touch chip, which comprises the capacitance detection circuit in various embodiments of the application.
An embodiment of the present application further provides an electronic device, including: a touch screen; a display screen; and, the touch chip in the various embodiments of the present application described above.
By way of example and not limitation, the electronic device in the embodiments of the present application may be a portable or mobile computing device such as a terminal device, a mobile phone, a tablet computer, a notebook computer, a desktop computer, a game device, an in-vehicle electronic device, or a wearable smart device, and other electronic devices such as an electronic database, an automobile, and an Automated Teller Machine (ATM). The wearable intelligent device comprises a device which has complete functions and large size and can realize complete or partial functions without depending on a smart phone, such as a smart watch or smart glasses and the like; and, only focus on a certain kind of application function, and need with other equipment such as the equipment that the smart mobile phone cooperation was used, for example, all kinds of intelligent bracelet, intelligent ornament etc. that carry out the physical sign monitoring.
It should be understood that the display screen and the touch screen described in the embodiments of the present application may be considered as a display layer and a touch layer in a screen of an electronic device, respectively. The screen of the circuit device generally includes a display layer and a touch layer for implementing a display function and a touch function, respectively.
It should be noted that, without conflict, the embodiments and/or technical features in the embodiments described in the present application may be arbitrarily combined with each other, and the technical solutions obtained after the combination also fall within the protection scope of the present application.
It should be understood that the specific examples in the embodiments of the present application are for the purpose of promoting a better understanding of the embodiments of the present application, and are not intended to limit the scope of the embodiments of the present application, and that various modifications and variations can be made by those skilled in the art based on the above embodiments and fall within the scope of the present application.
The above description is only for the specific embodiments of the present application, but the scope of the present application is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present application, and shall be covered by the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.
Claims (14)
1. The capacitance detection circuit is used for detecting self capacitance in a touch screen and comprises a control module, a first driving module, a charge transfer module and a processing module;
the control module is used for controlling the first driving module to output a driving signal;
the first driving module is provided with a first switch, a second switch, a first current source and a second current source, power supply voltage supplies power to the first current source, the second current source is grounded, the first switch and the second switch are positioned between the first current source and the second current source, and the output end of the first driving module is positioned between the first switch and the second switch; the output end of the first driving module outputs a driving signal to the touch screen for detecting the self-capacitance of the touch screen;
the output end of the first driving module is connected with the charge transfer module and is used for converting the charges of the self-capacitor to generate an output voltage, and the output voltage is related to the capacitance value of the self-capacitor; and
the processing module is connected with the output end of the charge transfer module and used for determining the capacitance value of the self-capacitance according to the output voltage.
2. The capacitance detection circuit according to claim 1, wherein the first driving module charges the self-capacitance through the first current source and the first switch;
the self-capacitance discharges through the second switch and the second current source.
3. The capacitance detection circuit according to claim 2, wherein the control module controls the first switch and the second switch to be turned on at different times by a reverse non-overlapping timing sequence so that the first driving module outputs the driving signal.
4. The capacitance detection circuit of claim 3, wherein a detection cycle in which the reverse non-overlapping timing controls the first switch and the second switch to not conduct at the same time includes four phases, wherein,
in the first stage, the first switch is controlled to be closed and the second switch is controlled to be opened, the first current source charges the self-capacitor, and the voltage of the output end of the first driving module rises to a peak;
in the second stage, the first switch and the second switch are controlled to be switched off, and the voltage of the output end of the first driving module is kept unchanged;
in the third stage, the first switch is controlled to be opened and the second switch is controlled to be closed, the self-capacitance discharges through the second current source, and the voltage of the output end of the first driving module is reduced to a wave trough;
a fourth stage, controlling the first switch to be switched off and the second switch to be switched off, wherein the voltage of the output end of the first driving module is kept unchanged;
and repeating the four stages to control the first driving module to output the square-wave-like signal.
5. The capacitance detection circuit of claim 3, wherein a detection cycle in which the reverse non-overlapping timing controls the first switch and the second switch to not conduct at the same time comprises two phases, wherein,
in the first stage, the first switch is controlled to be closed and the second switch is controlled to be opened, the first current source charges the self-capacitor, and the voltage of the output end of the first driving module rises to a peak;
in the second stage, the first switch is controlled to be switched off and the second switch is controlled to be switched on, the self-capacitance discharges through the second current source, and the voltage of the output end of the first driving module is reduced to a wave trough;
and repeating the two stages to control the first driving module to output the triangle wave-like signal.
6. The capacitance detection circuit according to any one of claims 1-5, wherein the charge transfer module is a differential voltage follower.
7. The capacitance detection circuit according to claim 6, wherein a positive phase input terminal of the differential voltage follower is connected to the output terminal of the first driving module, and an output terminal of the differential voltage follower is connected to a negative phase input terminal of the differential voltage follower, so that an output voltage follows an input voltage, and a voltage gain of the differential voltage follower is 1.
8. The capacitance detection circuit according to any one of claims 1 to 5, further comprising a second driving module, wherein an output end of the second driving module outputs a driving signal to the touch screen for detecting a mutual capacitance of the touch screen, and a capacitance value of the mutual capacitance is detected by dividing a voltage by the mutual capacitance and the self-capacitance.
9. The capacitance detection circuit according to claim 8, wherein the second driving module is connected to a first terminal of the mutual capacitance, and a second terminal of the mutual capacitance is connected to a first terminal of the self-capacitance and an input terminal of the charge transfer module;
the control module controls the first switch and the second switch to be switched off simultaneously, so that the capacitance detection circuit is used for detecting the mutual capacitance in the touch screen.
10. The capacitance detection circuit according to any one of claims 1-5, wherein the processing module is an analog-to-digital converter (ADC) circuit.
11. The capacitance detection circuit according to any one of claims 1-5, wherein the self-capacitance is the self-capacitance of each electrode to ground in the lateral and longitudinal directions of the touch screen.
12. The capacitance detection circuit according to any one of claims 1-5, wherein the mutual capacitance is a mutual capacitance between any two electrodes in a lateral direction and a longitudinal direction of the touch screen.
13. A touch chip comprising the capacitance detection circuit according to any one of claims 1 to 12.
14. An electronic device, comprising:
a display screen;
the touch screen is arranged on the surface of the display screen; and the number of the first and second groups,
the touch chip of claim 13, wherein the touch chip implements a touch display function.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116961658A (en) * | 2023-09-18 | 2023-10-27 | 南京沁恒微电子股份有限公司 | Touch key detection circuit and detection method thereof |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116961658A (en) * | 2023-09-18 | 2023-10-27 | 南京沁恒微电子股份有限公司 | Touch key detection circuit and detection method thereof |
| CN116961658B (en) * | 2023-09-18 | 2024-01-26 | 南京沁恒微电子股份有限公司 | Touch key detection circuit and detection method thereof |
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