CN115128359A - Capacitance detection circuit, chip and electronic equipment - Google Patents
Capacitance detection circuit, chip and electronic equipment Download PDFInfo
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- CN115128359A CN115128359A CN202210918374.6A CN202210918374A CN115128359A CN 115128359 A CN115128359 A CN 115128359A CN 202210918374 A CN202210918374 A CN 202210918374A CN 115128359 A CN115128359 A CN 115128359A
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Abstract
The application provides a capacitance detection circuit, chip and electronic equipment, capacitance detection circuit are applied to touch display device, and touch display device includes detection electrode, and capacitance detection circuit includes: the detection channel comprises an amplifying circuit and a first feedback circuit; the first input end of the amplifying circuit is connected with the detection electrode and used for receiving the capacitance detection signal output by the detection electrode, and the second input end of the amplifying circuit is connected with the reference signal; the amplifying circuit is used for amplifying the capacitance detection signal, wherein a first output end of the amplifying circuit is used for outputting a first capacitance detection signal with the same phase as the capacitance detection signal, and a second output end of the amplifying circuit is used for outputting a second capacitance detection signal with the opposite phase to the capacitance detection signal; the first feedback circuit is connected between the second input end of the amplifying circuit and the first output end of the amplifying circuit, and the first feedback circuit is a high-pass filter circuit, so that the touch performance is improved.
Description
Technical Field
The present application relates to electronic technologies, and in particular, to a capacitance detection circuit, a chip, and an electronic device.
Background
At present, the AMOLED screen is more and more common to be used by the display panel of the intelligent terminal, the AMOLED screen is divided into a hard screen and a soft screen, and along with the market demand, the soft screen is more and more popularized in use.
In the soft-screen AMOLED, the screen stack is thinned, wherein the distance from the driving electrode and the detection electrode for sensing the touch signal to the cathode ELVSS layer in the display panel is also reduced, which results in increased coupling capacitance between the cathode ELVSS layer and the driving electrode and the detection electrode, interference signals of the cathode ELVSS signal of the display panel are easily coupled to the touch panel, and particularly, a large amount of high-frequency harmonics in the interference signals may cause great interference to the touch panel, resulting in poor touch performance.
Disclosure of Invention
The application provides a capacitance detection circuit, a chip and electronic equipment, has restrained the influence of the high frequency harmonic in the interference signal to the capacitance detection, has promoted touch performance.
In a first aspect, an embodiment of the present application provides a capacitance detection circuit, which is applied to a touch display device, where the touch display device includes a detection electrode, and the capacitance detection circuit includes: a detection channel comprising an amplification circuit and a first feedback circuit;
a first input end of the amplifying circuit is connected with the detection electrode and is used for receiving a capacitance detection signal output by the detection electrode, and a second input end of the amplifying circuit is connected with a reference signal;
the amplifying circuit is used for amplifying the capacitance detection signal, wherein a first output end of the amplifying circuit is used for outputting a first capacitance detection signal with the same phase as the capacitance detection signal, and a second output end of the amplifying circuit is used for outputting a second capacitance detection signal with the opposite phase to the capacitance detection signal;
the first feedback circuit is connected between the second input end of the amplifying circuit and the first output end of the amplifying circuit, and the first feedback circuit is a high-pass filter circuit.
In one embodiment, the first feedback circuit comprises: a first capacitor and a first resistor;
the first end of the first capacitor is connected with the first output end of the amplifying circuit, the second end of the first capacitor is connected with the second input end of the amplifying circuit and the first end of the first resistor respectively, and the second end of the first resistor is connected with the reference signal.
In one embodiment, the method further comprises: a second feedback circuit;
the second feedback circuit is connected between the first input terminal of the amplification circuit and the second output terminal of the amplification circuit.
In one embodiment, the second feedback circuit includes: a second capacitor and a second resistor;
the second capacitor and the second resistor are connected in parallel between the second output end of the amplifying circuit and the first input end of the amplifying circuit.
In one embodiment, the capacitance detection signal includes an interference signal introduced into the capacitance detection circuit by a display panel, and the interference signal includes a high frequency harmonic.
In one embodiment, the amplification circuit includes a first operational amplifier;
the non-inverting input end of the first operational amplifier is connected with the detection electrode and used for receiving the capacitance detection signal output by the detection electrode, the inverting input end of the first operational amplifier is connected with the reference signal, the non-inverting output end of the first operational amplifier is used for outputting the first capacitance detection signal, and the inverting output end of the first operational amplifier is used for outputting the second capacitance detection signal.
In one embodiment, the amplification circuit comprises a second operational amplifier;
the non-inverting input end of the second operational amplifier is connected with the reference signal, the inverting input end of the second operational amplifier is connected with the detection electrode and used for receiving the capacitance detection signal output by the detection electrode, the non-inverting output end of the second operational amplifier is used for outputting the second capacitance detection signal, and the inverting output end of the second operational amplifier is used for outputting the first capacitance detection signal.
In one embodiment, the method further comprises: a control circuit;
the control circuit is used for determining a touch position according to the difference of the first capacitance detection signal and the second capacitance detection signal.
In a second aspect, the present application provides a chip comprising the capacitance detection circuit according to the first aspect.
In a third aspect, the present application provides an electronic device comprising a chip as described in the second aspect.
The application provides a capacitance detection circuit, chip and electronic equipment, this capacitance detection circuit is applied to touch display device, and touch display device includes detection electrode, and capacitance detection circuit includes: the detection channel comprises an amplifying circuit and a first feedback circuit; the first input end of the amplifying circuit is connected with the detection electrode and used for receiving the capacitance detection signal output by the detection electrode, and the second input end of the amplifying circuit is connected with the reference signal; the amplifying circuit is used for amplifying the capacitance detection signal, wherein a first output end of the amplifying circuit is used for outputting a first capacitance detection signal with the same phase as the capacitance detection signal, and a second output end of the amplifying circuit is used for outputting a second capacitance detection signal with the opposite phase to the capacitance detection signal; the first feedback circuit is connected between the second input end of the amplifying circuit and the first output end of the amplifying circuit, and the first feedback circuit is a high-pass filter circuit. The high-frequency interference signal in the first capacitance detection signal is fed back to the second input end of the amplifying circuit through the first feedback circuit, the high-frequency interference signal can be superposed on the first input end of the amplifying circuit, the voltage of the first input end of the amplifying circuit is increased, the pressure difference between two ends of the coupling capacitor formed by the driving electrode and the detection electrode is reduced, the current passing through the coupling capacitor is reduced, namely the current of the first input end of the amplifying circuit is reduced, the high-frequency gain of the amplifying circuit is also reduced, the high-frequency interference signal is restrained, and the touch performance is improved.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present application, and for those skilled in the art, other drawings can be obtained according to these drawings without inventive exercise.
Fig. 1 is a schematic view of a stacked layer of a touch electrode layer and a cathode ELVSS layer according to an embodiment of the present disclosure;
FIG. 2 is a schematic diagram of a capacitance detection circuit in the related art;
fig. 3 is a schematic frequency spectrum diagram of an interference signal according to an embodiment of the present application;
fig. 4 is a schematic structural diagram of a capacitance detection circuit according to an embodiment of the present disclosure;
fig. 5 is a circuit schematic diagram of a capacitance detection circuit according to an embodiment of the present disclosure;
fig. 6 is a circuit schematic diagram of another capacitance detection circuit provided in the embodiment of the present application;
fig. 7 is a schematic diagram illustrating a difference between frequency response curves of a capacitance detection circuit according to an embodiment of the present disclosure.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some embodiments of the present application, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
The touch display device includes a touch panel and a display panel, for example, the touch display device may be an AMOLED screen of an electronic device, the cathode of a light-emitting device in the display panel is connected with a cathode ELVSS layer, the cathode ELVSS layer is a cathode common reference signal of a display driving circuit, the cathode ELVSS layer outputs a cathode ELVSS signal, the cathode ELVSS signal is a cathode common reference signal of the display driving circuit, the cathode ELVSS signal contains an interference signal, and the interference signal contains a large amount of high-frequency harmonics, when the display driving circuit drives the display panel, the interference signal in the cathode ELVSS layer is introduced into the touch panel through the coupling capacitance between the cathode ELVSS layer and the driving electrode, and between the cathode ELVSS layer and the detecting electrode, which causes the influence on the touch panel, in order to suppress the influence of a large amount of high-frequency harmonics in an interference signal on a touch panel, in the embodiment of the present application, it is considered to improve a capacitance detection circuit in the related art.
First, the interference signal in the capacitance detection process is explained by combining the stacked structure of the AMOLED screen and the capacitance detection circuit in the related art.
In the AMOLED screen, a touch electrode layer for sensing a touch of a finger, a stylus pen, or the like and a cathode ELVSS layer are stacked, the touch electrode layer includes a driving electrode and a detection electrode, and the cathode ELVSS layer is disposed below the touch electrode layer. Because the coupling capacitance exists between the touch electrode layer and the cathode ELVSS layer, the interference signal of the cathode ELVSS layer is coupled into the capacitance detection circuit through the coupling capacitance, and the accuracy of the capacitance detection circuit in calculating the touch position is influenced.
Fig. 1 is a schematic view of a stack of a touch electrode layer and a cathode ELVSS layer according to an embodiment of the present disclosure. As shown in fig. 1, a touch electrode layer is disposed on the cathode ELVSS layer 100, and the touch electrode layer is used for sensing a touch position of a finger or a stylus and outputting a corresponding capacitance detection signal, and the touch electrode layer includes longitudinally distributed electrodes and transversely distributed electrodes, where in fig. 1, a longitudinal electrode 101 is taken as a driving electrode, and a transverse electrode 102 is taken as a detection electrode for illustration. In this case, the lateral electrode 102 may be a driving electrode, and the vertical electrode 101 may be a detection electrode. Drv1, Drv2, Drv3 and Drv4 in fig. 1 are driving signals, the driving signals are signals applied to driving electrodes by a driving circuit in the chip 103, the driving electrodes and the detection electrodes are both coupled with the chip 103, when a finger or a touch pen approaches or contacts the upper surface of the touch display device, the detection electrodes are used for inputting capacitance detection signals to the chip 103, the capacitance detection signals are Sens1, Sens2, Sens3 and Sens4 in fig. 1, and the capacitance detection circuit in the chip 103 calculates the touch position of the finger or the touch pen according to the capacitance detection signals.
A coupling capacitor Cs is formed between the detection electrode and the cathode ELVSS layer, a coupling capacitor Cd is formed between the driving electrode and the cathode ELVSS layer, and a detection capacitor Cx is formed between the driving electrode and the detection electrode, the capacitors jointly forming a capacitance generated by the coupling of the touch electrode layer, and the touch electrode layer receives the driving of the driving signal and outputs a capacitance detection signal to the capacitance detection circuit in the chip 103.
Fig. 2 is a schematic diagram of a capacitance detection circuit in the related art. As shown in fig. 2, the capacitance detection circuit includes a detection channel 201, and the detection channel 201 receives a capacitance detection signal SensN output from the detection electrode 202, the capacitance detection signal SensN being generated by a coupling capacitance Cs formed between the detection electrode 202 and the cathode ELVSS layer, a coupling capacitance Cd formed between the drive electrode 203 and the cathode ELVSS layer, and a detection capacitance Cx formed by a coupling between the drive electrode 203 and the detection electrode 202. The detection channel 201 receives the capacitance detection signal SensN output by the detection electrode 202, and amplifies the received capacitance detection signal SensN to output two paths of amplified capacitance detection signals, which are VoutN + and VoutN-, respectively, and have the same amplitude and opposite phases. Referring to fig. 2, an operational amplifier 204 is included in the detection channel 201, and two symmetrical feedback circuits, namely a feedback circuit 205 and a feedback circuit 206, are adopted for the signal feedback of the operational amplifier 204.
Since the cathode ELVSS signal is used as a reference signal for display driving in the display panel, the cathode ELVSS signal is equivalently grounded when the display driving is not performed, and the cathode ELVSS signal is coupled to an interference signal of the display panel when the display driving is performed, and the interference signal is coupled into the detection channel 201 through the coupling capacitor described above, it can be seen that the interference signal in the cathode ELVSS layer can be coupled into the detection channel 201 through two paths, wherein the path 1 is coupled into through the coupling capacitor Cs, the path 2 is coupled into through a series path of the coupling capacitor Cd and the detection capacitor Cx, and the path 1 is a main coupling path, thereby causing the interference signal to exist in the capacitance detection signal SensN, in particular, the interference signal also has a large number of high-frequency harmonics in addition to the fundamental frequency, for example, as shown in fig. 3, a frequency spectrum diagram of the interference signal is shown, FL-FH is the working frequency band of capacitance detection, and it can be seen that interference harmonics still exist in the frequency band higher than FH, and these interference harmonics are high frequency harmonics, which can have a great influence on capacitance detection, resulting in poor touch performance.
Therefore, in the embodiment of the present application, it is proposed to improve the part of the feedback circuit 206 of the capacitance detection circuit to suppress the influence of the high frequency harmonic on the touch performance.
Hereinafter, the capacitance detection circuit provided in the present application will be described in detail by specific embodiments. It is to be understood that the following detailed description may be combined with other embodiments, and that the same or similar concepts or processes may not be repeated in some embodiments.
Fig. 4 is a schematic structural diagram of a capacitance detection circuit according to an embodiment of the present disclosure. As shown in fig. 4, the capacitance detection circuit includes: a detection channel 401, the detection channel 401 comprising an amplification circuit 402 and a first feedback circuit 403.
A first input terminal of the amplifying circuit 402 is connected to the detection electrode and is configured to receive the capacitance detection signal SensN output by the detection electrode, and a second input terminal of the amplifying circuit 402 is connected to the reference signal Vcmi.
The amplifying circuit 402 is configured to amplify the capacitance detection signal SensN, wherein a first output terminal of the amplifying circuit 402 is configured to output a first capacitance detection signal Vout1 having the same phase as the capacitance detection signal SensN, and a second output terminal of the amplifying circuit 402 is configured to output a second capacitance detection signal Vout2 having the opposite phase to the capacitance detection signal SensN.
The first feedback circuit 403 is connected between the second input terminal of the amplifying circuit 402 and the first output terminal of the amplifying circuit 402, and the first feedback circuit 403 is a high-pass filter circuit.
The drive electrode and the detection electrode of the touch display device are coupled to form a detection capacitance Cx, when the touch display device is touched by a finger or a stylus, the detection capacitance Cx at the touch position is changed, so that a capacitance detection signal SenSN output by the detection electrode is changed, and the capacitance detection circuit receives the capacitance detection signal output by the detection electrode and determines the touch position of the finger based on the change of the capacitance detection signal. Fig. 4 only illustrates one detection channel 401 as an example, in the embodiment of the present disclosure, the number of the detection channels 401 is related to the number of the detection electrodes in the touch panel, each row of the detection electrodes is connected to one detection channel 401, and the detection channels can be set as needed in practical application.
Since the capacitance detection signal SensN includes an interference signal, a high-frequency harmonic in the interference signal is amplified by the amplifying circuit 402, so that the output first capacitance detection signal Vout1 and the second capacitance detection signal Vout2 also include a high-frequency interference signal, where the first capacitance detection signal Vout1 and the capacitance detection signal SensN have the same phase, and the second capacitance detection signal Vout2 and the capacitance detection signal SensN have the opposite phase.
In the embodiment of the present application, the first feedback circuit 403 between the second input terminal of the amplifying circuit 402 and the first output terminal of the amplifying circuit 402 is a high-pass filter circuit, so as to feed back the high-frequency interference signal in the first capacitance detection signal Vout1 to the second input terminal of the amplifying circuit 402, because the amplifying circuit 402 has the characteristic that the voltages of the two input terminals are consistent, the high-frequency interference signal is also superimposed on the first input terminal of the amplifying circuit 402, that is, the input terminal for receiving the capacitance detection signal SensN, because the first capacitance detection signal Vout1 is in phase with the capacitance detection signal SensN, the high-frequency interference signal is in phase with the capacitance detection signal SensN, that is, the high-frequency interference signal is superimposed on the first input terminal of the amplifying circuit 402, the voltage of the first input terminal of the amplifying circuit 402 is increased, and the voltage difference between the coupling capacitors formed by the detection electrodes and the driving electrodes is reduced, the current through the coupling capacitor is reduced, that is, the current at the first input terminal of the amplifying circuit 402 is reduced, which also reduces the high frequency gain of the amplifying circuit 402, thereby suppressing the high frequency interference signal and improving the touch performance.
The following is further described with reference to the circuit diagram.
Referring to fig. 5, a detection channel 401 includes an amplification circuit 402 and a first feedback circuit 403. Wherein, the first feedback circuit 403 includes: a first capacitor Cfb1 and a first resistor Rin 1.
A first input terminal of the amplifying circuit 402 is connected to the detecting electrode 405 for receiving the capacitance detecting signal SensN output by the detecting electrode 405, and a second input terminal of the amplifying circuit 402 is connected to a reference signal Vcmi, for example, Vcmi is 1/2 × VCC.
A first end of the first capacitor Cfb1 is connected to a first output terminal of the amplifying circuit 402, a second end of the first capacitor Cfb1 is connected to a second input terminal of the amplifying circuit 402 and a first end of the first resistor Rin1, respectively, a first end of the first resistor Rin1 is connected to a second input terminal of the amplifying circuit 402, and a second end of the first resistor Rin1 is connected to the reference signal 405.
The circuit diagram of fig. 5 illustrates that the amplifying circuit 402 receives the capacitance detection signal SensN outputted from the detection electrode 405, and the capacitance detection signal SensN is generated by the coupling capacitance Cs formed between the detection electrode 405 and the cathode ELVSS layer, the coupling capacitance Cd formed between the driving electrode 406 and the cathode ELVSS of the display driving, and the detection capacitance Cx formed by the coupling between the driving electrode 406 and the detection electrode 405. The driving circuit in the chip 103 outputs a driving signal to the driving electrode 406, which is illustrated by taking the mth column driving signal VdrvM as an example.
The first capacitor Cfb1 and the first resistor Rin1 in the first feedback circuit can be sized according to practical situations.
As shown in fig. 5, when the first capacitance detection signal VoutN + outputted from the first output terminal of the amplifying circuit 402 is VoutN + outputted from the first output terminal of the amplifying circuit 402, in the embodiment, the first capacitance detection signal Vout1 is VoutN +, the first capacitance detection signal VoutN + is fed back to the second input terminal of the amplifying circuit 402 through the first capacitor Cfb1, due to the high-pass filtering function of the first feedback circuit 403, a high-frequency interference signal in the first capacitance detection signal VoutN + is fed back to the second input terminal of the amplifying circuit 402 through the first capacitor Cfb1, and due to the characteristic that the voltages of the two input terminals of the amplifying circuit 402 are consistent, the high-frequency interference signal is also superimposed on the first input terminal of the amplifying circuit 402, that is, the input terminal of the amplifying circuit 402 receiving the capacitance detection signal SensN, and the high-frequency interference signal is in phase with the capacitance detection signal SensN, so that the voltage of the first input terminal of the amplifying circuit 402 is increased, the voltage difference between the two ends of the coupling capacitor is reduced, and the current passing through the coupling capacitor is reduced, that is, the current of the first input end of the amplifying circuit 402 is reduced, so that the high-frequency gain of the amplifying circuit 402 is reduced, high-frequency interference signals in the output of the amplifying circuit 402 are suppressed, and the touch performance is improved.
Optionally, the capacitance detection circuit further comprises a second feedback circuit 404.
The second feedback circuit 404 is connected between the first input terminal of the amplification circuit 402 and the second output terminal of the amplification circuit 402.
Optionally, the second feedback circuit 404 includes: a second capacitor Cfb2 and a second resistor Rfb 2.
A first terminal of the second capacitor Cfb2 is connected to a first input terminal of the amplifier circuit 402, a second terminal of the second capacitor Cfb2 is connected to a second output terminal of the amplifier circuit 402, a first terminal of the second resistor Rfb2 is connected to a first input terminal of the amplifier circuit 402, and a second terminal of the second resistor Rfb2 is connected to a second output terminal of the amplifier circuit 402. The second capacitor Cfb2 and the second resistor Rfb2 in the second feedback circuit 404 can be sized according to practical situations. The low frequency gain of the capacitive sensing circuit can be adjusted by adjusting the size of the second capacitor Cfb2 and the second resistor Rfb2 in the second feedback circuit 404.
On the basis of the above-described embodiment, the amplifier circuit 402 will be described.
In the embodiment of the present application, the capacitance detection signal SensN is input to the first input terminal of the amplifying circuit 402, the first feedback circuit 403 is connected between the second input terminal of the amplifying circuit 402 and the first output terminal of the amplifying circuit 402, and the phase of the first capacitance detection signal Vout1 output by the first output terminal of the amplifying circuit 402 is the same as that of the capacitance detection signal SensN.
In one embodiment, with continued reference to fig. 5, the amplification circuit 402 includes a first operational amplifier 4021.
The non-inverting input terminal of the first operational amplifier 4021 is connected to the detection electrode 405 and configured to receive the capacitance detection signal SensN output by the detection electrode 405, the inverting input terminal of the first operational amplifier 4021 is connected to the reference signal Vcmi, the non-inverting output terminal of the first operational amplifier 4021 is configured to output the first capacitance detection signal Vout1, and the inverting output terminal of the first operational amplifier 4021 is configured to output the second capacitance detection signal Vout 2. That is, in the embodiment shown in fig. 5, the first input terminal of the amplifying circuit 402 is the non-inverting input terminal of the first operational amplifier 4021, the second input terminal of the amplifying circuit 402 is the inverting input terminal of the first operational amplifier 4021, the signal VoutN + output by the non-inverting output terminal of the first operational amplifier 4021 is the first capacitance detection signal Vout1, and the signal VoutN-output by the inverting output terminal of the first operational amplifier 4021 is the second capacitance detection signal Vout 2.
Due to the high-pass filtering effect of the first feedback circuit 403, a high-frequency interference signal in the first capacitance detection signal VoutN + is fed back to the inverting input terminal of the first operational amplifier 4021 through the first capacitor Cfb1, and due to the characteristic that the voltages of the two input terminals of the amplifying circuit 402 are consistent, the high-frequency interference signal is also superimposed on the non-inverting input terminal of the first operational amplifier 4021, that is, the input terminal of the first operational amplifier 4021 receiving the capacitance detection signal SensN, because the first capacitance detection signal VoutN-is in phase with the capacitance detection signal SensN, the high-frequency interference signal increases the voltage of the non-inverting input terminal of the first operational amplifier 4021, so that the voltage difference between the two terminals of the coupling capacitor is reduced, that is, the current passing through the coupling capacitor is reduced, that is, the current at the non-inverting input terminal of the first operational amplifier 4021 is reduced, so that the high-frequency gain of the amplifying circuit 402 is reduced, thereby suppressing high-frequency interference signals in the output of the amplifying circuit 402 and improving the touch performance.
In another embodiment, referring to fig. 6, the detection channel 401 includes an amplification circuit 402 and a first feedback circuit 403.
The amplifying circuit 402 includes a second operational amplifier 4022.
A non-inverting input terminal of the second operational amplifier 4022 is connected to the reference signal Vcmi, an inverting input terminal of the second operational amplifier 4022 is connected to the detection electrode 405 and is configured to receive the capacitance detection signal SensN output by the detection electrode 405, a non-inverting output terminal of the second operational amplifier 4022 is configured to output the second capacitance detection signal Vout2, and an inverting output terminal of the second operational amplifier 4022 is configured to output the first capacitance detection signal Vout 1. That is, in the embodiment shown in fig. 6, the first input terminal of the amplifying circuit 402 is the inverting input terminal of the first operational amplifier 4021, the second input terminal of the amplifying circuit 402 is the non-inverting input terminal of the first operational amplifier 4021, the signal VoutN-output from the inverting output terminal of the first operational amplifier 4021 is the first capacitance detection signal Vout1, and the signal VoutN + output from the non-inverting output terminal of the first operational amplifier 4021 is the second capacitance detection signal Vout 2.
The first feedback circuit 403 includes: a first capacitor Cfb1 and a first resistor Rin 1. A first terminal of the first capacitor Cfb1 is connected to a first output terminal of the amplifier circuit 402, a second terminal of the first capacitor Cfb1 is connected to a second input terminal of the amplifier circuit 402 and a first terminal of the first resistor Rin1, and a second terminal of the first resistor Rin1 is connected to the reference signal 405. The first capacitor Cfb1 and the first resistor Rin1 in the first feedback circuit 403 can be sized according to practical situations.
Fig. 6 is a circuit diagram illustrating that the second operational amplifier 4022 receives a capacitance detection signal SensN output from the detection electrode 405, the capacitance detection signal SensN being generated by the combined action of the coupling capacitance Cs formed between the detection electrode 405 and the cathode ELVSS layer, the coupling capacitance Cd formed between the driving electrode 406 and the cathode ELVSS for display driving, and the detection capacitance Cx formed by the coupling between the driving electrode 406 and the detection electrode 405. The driving circuit in the chip 103 outputs a driving signal to the driving electrode 406, which is illustrated by taking the mth column driving signal VdrvM as an example.
In this embodiment, when the first capacitance detection signal Vout1 is VoutN-, and the first capacitance detection signal VoutN-is fed back to the non-inverting input terminal of the second operational amplifier 4022 through the first capacitance Cfb1, due to the high-pass filtering function of the first feedback circuit 403, a high-frequency interference signal in the first capacitance detection signal VoutN-is fed back to the non-inverting input terminal of the second operational amplifier 4022 through the first capacitance Cfb1, and due to the consistent voltage characteristics of the two input terminals of the second operational amplifier 4022, the high-frequency interference signal is also superimposed on the inverting input terminal of the second operational amplifier 4022, that is, the input terminal of the second operational amplifier 4022 receives the capacitance detection signal SensN, and since the first capacitance detection signal VoutN-is in phase with the capacitance detection signal SensN, the high-frequency interference signal increases the voltage of the inverting input terminal of the second operational amplifier 4022, the voltage difference between the two ends of the coupling capacitor is reduced, and the current passing through the coupling capacitor is reduced, that is, the current at the inverting input end of the second operational amplifier 4022 is reduced, so that the high-frequency gain of the amplifying circuit 402 is reduced, a high-frequency interference signal in the output of the amplifying circuit 402 is suppressed, and the touch performance is improved.
Optionally, the capacitance detection circuit further comprises a second feedback circuit 404. The second feedback circuit 404 is connected between the first input terminal of the amplification circuit 402 and the second output terminal of the amplification circuit 402.
Optionally, the second feedback circuit 404 includes: a second capacitor Cfb2 and a second resistor Rfb 2.
A first terminal of the second capacitor Cfb2 is connected to a first input terminal of the amplifier circuit 402, a second terminal of the second capacitor Cfb2 is connected to a second output terminal of the amplifier circuit 402, a first terminal of the second resistor Rfb2 is connected to a first input terminal of the amplifier circuit 402, and a second terminal of the second resistor Rfb2 is connected to a second output terminal of the amplifier circuit 402. The second capacitor Cfb2 and the second resistor Rfb2 in the second feedback circuit 404 can be sized according to practical situations. The low frequency gain of the capacitive sensing circuit can be adjusted by adjusting the size of the second capacitor Cfb2 and the second resistor Rfb2 in the second feedback circuit 404.
In both embodiments, the amount of signal in the circuit is unchanged, but the output signals are opposite in phase.
In the capacitance detection circuit of the embodiment of the present application, the first feedback circuit 403 suppresses the high-frequency gain of the capacitance detection circuit, so that the peak value of the frequency response characteristic curve of the capacitance detection circuit is shifted to the left, as shown in fig. 7, curve 1 is the frequency response characteristic curve of the capacitance detection circuit of the related art shown in fig. 2, and curve 2 is the frequency response characteristic curve of the capacitance detection circuit of the embodiment of the present application, it can be seen that, compared to curve 1, the peak value of curve 2 is shifted to the left, in the operating frequency band of FL-FH, the gain of the capacitance detection circuit of the embodiment of the present application is greater than that of the capacitance detection circuit of the related art, and in the high-frequency band higher than FH, the gain of the capacitance detection circuit of the embodiment of the present application is less than that of the capacitance detection circuit of the related art, that is, the capacitance detection circuit of the embodiment of the present application can suppress the high-frequency interference signal well, the signal quantity is improved, the interference quantity is suppressed, the capacitance detection signal amplified by the detection channel has a higher signal-to-noise ratio, and the touch performance is improved.
Optionally, the capacitance detection circuit of the embodiment of the present application further includes a control circuit.
The control circuit is used for determining the touch position according to the difference of the first capacitance detection signal and the second capacitance detection signal.
That is, the control circuit determines the touch position based on twice capacitance detection signals, which is equivalent to that the amplification factor of the amplification circuit is increased by one time, and further improves the sensitivity, accuracy and stability of touch detection. The method for determining the touch position based on the specific capacitance detection signal by the control circuit may refer to the related art, and is not described in detail in this embodiment. Optionally, the control circuit is a micro processing Unit (MCU).
The chip 103 illustrated in fig. 1 will be described with reference to fig. 5 and 6. Alternatively, the amplifying circuit 402, the first feedback circuit 403 and the second feedback circuit 404 in fig. 5 and 6 may be integrated in the chip 103 shown in fig. 1. Alternatively, the control circuit may be integrated into the chip 103 shown in fig. 1.
The embodiment of the present application further provides a chip, which includes the capacitance detection circuit in any of the above embodiments.
The embodiment of the application also provides electronic equipment which comprises a screen and the chip in the embodiment.
In the present application, the terms "include" and variations thereof may refer to non-limiting inclusions; the term "or" and variations thereof may mean "and/or". The terms "first," "second," and the like in this application are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. In the present application, "a plurality" means two or more. "and/or" describes the association relationship of the associated objects, meaning that there may be three relationships, e.g., a and/or B, which may mean: a exists alone, A and B exist simultaneously, and B exists alone. The character "/" generally indicates that the former and latter associated objects are in an "or" relationship.
In the several embodiments provided in the present application, it should be understood that the disclosed apparatus and method may be implemented in other ways. For example, the above-described embodiments of the apparatus are merely illustrative, and for example, the division of modules is only one logical division, and other divisions may be realized in practice, for example, a plurality of modules may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed coupling or direct coupling or communication connection between each other may be through some interfaces, indirect coupling or communication connection between devices or modules, and may be in an electrical, mechanical or other form.
Those of ordinary skill in the art will understand that: all or a portion of the steps of implementing the above-described method embodiments may be performed by hardware associated with program instructions. The program may be stored in a computer-readable storage medium. When executed, the program performs steps comprising the method embodiments described above; and the aforementioned storage medium includes: various media that can store program codes, such as ROM, RAM, magnetic or optical disks.
Finally, it should be noted that: the above embodiments are only used for illustrating the technical solutions of the present application, and not for limiting the same; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present application.
Claims (10)
1. A capacitance detection circuit applied to a touch display device including a detection electrode, the capacitance detection circuit comprising: a detection channel comprising an amplification circuit and a first feedback circuit;
a first input end of the amplifying circuit is connected with the detection electrode and is used for receiving a capacitance detection signal output by the detection electrode, and a second input end of the amplifying circuit is connected with a reference signal;
the amplifying circuit is used for amplifying the capacitance detection signal, wherein a first output end of the amplifying circuit is used for outputting a first capacitance detection signal with the same phase as the capacitance detection signal, and a second output end of the amplifying circuit is used for outputting a second capacitance detection signal with the opposite phase to the capacitance detection signal;
the first feedback circuit is connected between the second input end of the amplifying circuit and the first output end of the amplifying circuit, and the first feedback circuit is a high-pass filter circuit.
2. The capacitance detection circuit according to claim 1, wherein the first feedback circuit comprises: a first capacitor and a first resistor;
the first end of the first capacitor is connected with the first output end of the amplifying circuit, the second end of the first capacitor is connected with the second input end of the amplifying circuit and the first end of the first resistor respectively, and the second end of the first resistor is connected with the reference signal.
3. The capacitance detection circuit according to claim 1, further comprising: a second feedback circuit;
the second feedback circuit is connected between the first input terminal of the amplifying circuit and the second output terminal of the amplifying circuit.
4. The capacitance detection circuit according to claim 3, wherein the second feedback circuit comprises: a second capacitor and a second resistor;
the second capacitor and the second resistor are connected in parallel between the second output end of the amplifying circuit and the first input end of the amplifying circuit.
5. The capacitance detection circuit according to any one of claims 1 to 4, wherein the capacitance detection signal comprises an interference signal introduced into the capacitance detection circuit by a display panel, and the interference signal comprises high frequency harmonics.
6. The capacitance detection circuit according to any one of claims 1-4, wherein the amplification circuit comprises a first operational amplifier;
the non-inverting input end of the first operational amplifier is connected with the detection electrode and used for receiving the capacitance detection signal output by the detection electrode, the inverting input end of the first operational amplifier is connected with the reference signal, the non-inverting output end of the first operational amplifier is used for outputting the first capacitance detection signal, and the inverting output end of the first operational amplifier is used for outputting the second capacitance detection signal.
7. The capacitance detection circuit according to any one of claims 1-4, wherein the amplification circuit comprises a second operational amplifier;
the non-inverting input end of the second operational amplifier is connected with the reference signal, the inverting input end of the second operational amplifier is connected with the detection electrode and used for receiving the capacitance detection signal output by the detection electrode, the non-inverting output end of the second operational amplifier is used for outputting the second capacitance detection signal, and the inverting output end of the second operational amplifier is used for outputting the first capacitance detection signal.
8. The capacitance detection circuit according to any one of claims 1 to 4, further comprising: a control circuit;
the control circuit is configured to determine a touch location based on a difference between the first capacitive detection signal and the second capacitive detection signal.
9. A chip comprising a capacitance detection circuit according to any one of claims 1 to 8.
10. An electronic device comprising the chip of claim 9.
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| CN202210918374.6A CN115128359A (en) | 2022-08-01 | 2022-08-01 | Capacitance detection circuit, chip and electronic equipment |
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| CN202210918374.6A CN115128359A (en) | 2022-08-01 | 2022-08-01 | Capacitance detection circuit, chip and electronic equipment |
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