US20160282991A1 - Capacitive touch device with high sensitivity and operating method thereof - Google Patents
Capacitive touch device with high sensitivity and operating method thereof Download PDFInfo
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- US20160282991A1 US20160282991A1 US15/080,718 US201615080718A US2016282991A1 US 20160282991 A1 US20160282991 A1 US 20160282991A1 US 201615080718 A US201615080718 A US 201615080718A US 2016282991 A1 US2016282991 A1 US 2016282991A1
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- emulation
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
- G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
- G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
- G06F3/041—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
- G06F3/0416—Control or interface arrangements specially adapted for digitisers
- G06F3/0418—Control or interface arrangements specially adapted for digitisers for error correction or compensation, e.g. based on parallax, calibration or alignment
- G06F3/04182—Filtering of noise external to the device and not generated by digitiser components
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
- G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
- G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
- G06F3/041—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
- G06F3/0416—Control or interface arrangements specially adapted for digitisers
- G06F3/04166—Details of scanning methods, e.g. sampling time, grouping of sub areas or time sharing with display driving
- G06F3/041662—Details of scanning methods, e.g. sampling time, grouping of sub areas or time sharing with display driving using alternate mutual and self-capacitive scanning
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
- G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
- G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
- G06F3/041—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
- G06F3/044—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means by capacitive means
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
- G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
- G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
- G06F3/041—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
- G06F3/0416—Control or interface arrangements specially adapted for digitisers
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
- G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
- G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
- G06F3/041—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
- G06F3/0416—Control or interface arrangements specially adapted for digitisers
- G06F3/0418—Control or interface arrangements specially adapted for digitisers for error correction or compensation, e.g. based on parallax, calibration or alignment
Definitions
- This disclosure generally relates to a touch device, more particularly, to a capacitive touch device with high sensitivity and an operating method thereof.
- the touch panel Because a user can operate a touch panel by intuition, the touch panel has been widely applied to various electronic devices. In general, the touch panel is classified into capacitive, resistive and optical touch panels.
- the capacitive touch sensor is further classified into self-capacitive touch sensors and mutual capacitive touch sensors. These two kinds of touch sensors have different characteristics of the capacitive variation, so they are adaptable to different functions. For example, the mutual capacitive touch sensors are adaptable to the multi-touch detection, and the self-capacitive touch sensors have a higher sensitivity to hovering operations and a lower sensitivity to water drops. However, how to improve the touch sensitivity of these two kinds of capacitive touch sensors is an important issue.
- the present disclosure provides a capacitive touch device with high sensitivity and an operating method thereof.
- the present disclosure provides a capacitive touch device and an operating method thereof in which an emulation circuit is arranged in a control chip to generate a reference signal as a cancellation of a detection signal, and thus a size of a detection capacitor in the control chip is reduced.
- the present disclosure provides a capacitive touch device and an operating method thereof in which an emulation circuit is arranged in a control chip to generate a reference signal as a cancellation of a detection signal, and thus a touch sensitivity is improved.
- the present disclosure provides a capacitive touch device including a touch panel and a control chip.
- the touch panel includes a detection electrode forming a self-capacitor.
- the control chip includes a detection capacitor, an input resistor, an amplifying circuit and an emulation circuit, wherein the detection capacitor, the self-capacitor, the input resistor and the amplifying circuit form a first filter circuit, the emulation circuit forms a second filter circuit, and a frequency response of the second filter circuit is determined according to a frequency response of the first filter circuit.
- the present disclosure further provides a capacitive touch device including a touch panel and a control chip.
- the touch panel includes a plurality of detection electrodes respectively forming a self-capacitor.
- the control chip includes an emulation circuit, a plurality of programmable filters and a subtraction circuit.
- the emulation circuit outputs a reference signal.
- the programmable filters are respectively coupled to the detection electrodes.
- the subtraction circuit is coupled to the emulation circuit, and configured to be sequentially coupled to the programmable filters in a self-capacitive mode and perform a differential operation on the reference signal outputted by the emulation circuit and a detection signal outputted by the coupled programmable filter to output a differential detected signal.
- the present disclosure further provides an operating method of a capacitive touch device.
- the capacitive touch device includes a touch panel and a control chip.
- the touch panel includes a plurality of drive electrodes and a plurality of receiving electrodes extending along different directions.
- the control chip includes a plurality of drive circuits, a plurality of detection capacitors, a subtraction circuit and an anti-aliasing filter.
- the operating method includes: respectively coupling, in a self-capacitive mode, the drive circuits to first ends of the drive electrodes via the detection capacitors, and respectively coupling the subtraction circuit to second ends of the drive electrodes; and respectively coupling, in a mutual capacitive mode, the drive circuits to the first ends of the drive electrodes without passing the detection capacitors, and respectively coupling the anti-aliasing filter to second ends of the receiving electrodes without passing the subtraction circuit.
- a capacitive touch device of the present disclosure is adaptable to a touch device which uses only a self-capacitive detection mode, and to a touch device which uses a dual-mode detection including the self-capacitive detection mode and a mutual capacitive detection mode.
- FIG. 1 is a schematic block diagram of a capacitive touch device according to one embodiment of the present disclosure.
- FIG. 2 is a schematic block diagram of a capacitive touch device according to one embodiment of the present disclosure.
- FIG. 3 is another schematic block diagram of a capacitive touch device according to one embodiment of the present disclosure.
- FIG. 4A is the waveform of a detection signal and a reference signal in the capacitive touch device of the embodiments of FIGS. 2 and 3 .
- FIG. 4B is a waveform of a differential detected signal of the detection signal and the reference signal in FIG. 4A .
- FIG. 5 is a flow chart of an operating method of a capacitive touch device according to one embodiment of the present disclosure.
- FIG. 6 is a frequency response of a filter circuit of a capacitive touch device according to one embodiment of the present disclosure.
- the capacitive touch device 1 includes a control chip 100 and a touch panel 13 , wherein the capacitive touch device 1 is preferably able to detect by a self-capacitive mode.
- the capacitive touch device 1 is able to detect approaching objects and distinguish touch positions by successively using a self-capacitive mode and a mutual capacitive mode. For example, in some embodiments, because a scanning interval of the self-capacitive mode is short, the capacitive touch device 1 is able to identify whether any object is approaching using the self-capacitive mode.
- a touch position is identified using the mutual capacitive mode.
- the capacitive touch device 1 is able to identify a rough position of an approaching object and determine a window of interest (WOI) on the touch panel 13 with the self-capacitive mode, and then identify a fine position within the window of interest with the mutual capacitive mode to reduce data amount to be processed in the mutual capacitive mode.
- WI window of interest
- the touch panel 13 includes a plurality of detection electrodes 131 to respectively form a self-capacitor C s , wherein the detection electrodes 131 include a plurality of drive electrodes and a plurality of receiving electrodes extending along different directions, e.g., perpendicular to each other.
- Mutual capacitors C m (referring to FIGS. 2 and 3 ) are formed between the drive electrodes and the receiving electrodes.
- the principle of forming self-capacitors and mutual capacitors in a capacitive touch panel is known and is not an object of the present disclosure, and thus details thereof is not described herein.
- the control chip 100 includes a plurality of drive circuits 11 , a plurality of detection capacitors C in and an emulation circuit 150 , wherein the emulation circuit 150 is used to emulate the characteristics of the detection line in a self-capacitive mode (described hereinafter).
- the drive circuits 11 and the detection capacitors C in are electrically coupled to signal inputs of the detection electrodes 131 via pins.
- the drive circuits 11 output a drive signal Sd, e.g., a sine wave, a cosine wave or a square wave to the detection electrodes 131 .
- a mutual capacitive mode only the drive circuit 11 corresponding to the drive electrode outputs the drive signal Sd, whereas the drive circuit 11 corresponding to the receiving electrode is bypassed.
- the capacitive touch device 1 includes a touch panel 13 and a control chip 100 .
- the control chip 100 includes a plurality of drive circuits 11 , a plurality of detection capacitors C in , an analog front end 15 and a digital back end 16 , wherein as the digital back end 16 is not an object of the present disclosure, details thereof are not described herein.
- the drive circuits 11 are able to be electrically coupled to signal inputs of the detection electrodes 131 via the detection capacitors C in (e.g. in the self-capacitive mode) or bypassing the detection capacitors C in (e.g. in the mutual capacitive mode), wherein said coupled to and bypassing the detection capacitors C in is able to be implemented by arranging a plurality of switches SW 1 between the drive circuits 11 and the touch panel 13 .
- the analog front end 15 includes an emulation circuit 150 , a plurality of programmable filters 151 , a subtraction circuit 52 , a gain circuit 153 and an anti-aliasing filter (AAF) 154 .
- the programmable filters 151 , the detection capacitors C in and the self-capacitors C s of the detection electrodes 131 form a first filter circuit, wherein the first filter circuit is, e.g., a band-pass filter (BPF) or a high-pass filter (HPF).
- BPF band-pass filter
- HPF high-pass filter
- the first filter circuit is able to further form a band-pass filter having a predetermined bandwidth with a low-pass filter formed by the anti-aliasing filter 154 .
- each detection electrode 131 is coupled to (e.g. via a switch) one programmable filter 151 . It should be mentioned that although only the horizontally arranged detection electrodes 131 shown in FIGS. 2 and 3 are coupled to the programmable filters 151 , in other embodiments the programmable filters 151 are also coupled to the longitudinally arranged detection electrodes 131 , and the present disclosure is not limited to those shown in FIGS. 2 and 3 .
- the emulation circuit 150 forms a second filter circuit and outputs a reference signal S ref , wherein the second filter circuit is, e.g., a band-pass filter or a high-pass filter.
- the second filter circuit is able to further form a band-pass filter having a predetermined bandwidth with a low-pass filter formed by the anti-aliasing filter 154 .
- the subtraction circuit 152 is coupled to the emulation circuit 150 and is sequentially and electrically coupled to the programmable filters 151 via switches SW 2 in a self-capacitive mode to be further electrically coupled to the detection electrodes 131 .
- the subtraction circuit 152 performs a differential operation on the reference signal S ref outputted by the emulation circuit 150 and a detection signal S o1 outputted by the coupled programmable filter 151 to output a differential detected signal S diff .
- the detection capacitors C in are respectively and electrically coupled to signal inputs of the detection electrodes 131 via a plurality of switches (e.g. SW 1 ), and the subtraction circuit 152 is respectively and electrically coupled to the programmable filters 151 and the detection electrodes 131 via a plurality of switches (e.g. SW 2 ).
- the detection capacitor C in is disposed in the control chip 100 to form the voltage division with the self-capacitor C s . Accordingly, the capacitive touch device 1 identifies a touch event according to a variation of peak-to-peak values of the differential detected signal S diff , wherein the differential detected signal S diff is a continuous signal. Before a touch event is identified, the differential detected signal S diff is further filtered or digitized. For example, FIG. 2 shows the touched differential detected signal S touch and the non-touched differential detected signal S non .
- the self-capacitor C s is generally very large, an effective voltage division is implemented by using a large detection capacitor C in . Therefore, the considerable disposition space in the chip for the large capacitor is necessary such that a total size of the control chip 100 is unable to be reduced.
- the circuit characteristics of the detection line (e.g. from the drive circuit 11 via the detection capacitor C in , the detection electrode 131 and the programmable filter 151 ) is emulated by disposing the emulation circuit 150 to output the reference signal S ref as a cancellation of the detection signal S o1 , as shown in FIG. 4 .
- the capacitance of the detection capacitor C in is able to be decreased by subtracting the cancellation from the detection signal S o1 .
- the capacitance of the detection capacitor C in is preferably smaller than 10 percent of capacitance of the self-capacitor C s . Therefore, the size of the control chip 100 is effectively decreased.
- a gain circuit 153 is employed to amplify the differential detected signal S diff , wherein a gain of the gain circuit 153 is determined according to an analytical range of an analog-to-digital convertor (ADC) of the digital back end 16 , but not limited thereto.
- ADC analog-to-digital convertor
- FIG. 2 the difference between the touched differential detected signal S touch and the non-touched differential detected signal S non , which are signals (i.e. differential detected signal) outputted by the gain circuit 153 , is increased such that a touch event is easier to be identified.
- the anti-aliasing filter 154 filters the amplified differential detected signal and, as mentioned above, the anti-aliasing filter 154 is, for example, a low-pass filter.
- FIG. 3 it is another schematic block diagram of a capacitive touch device according to one embodiment of the present disclosure, wherein FIG. 3 further shows an implementation of the emulation circuit 150 and the programmable filter 151 .
- the programmable filter 151 includes an input resistor R in and an amplifying circuit 15 A, wherein the detection capacitor C in , the self-capacitor C s , the input resistor R in and the amplifying circuit 15 A form a first filter circuit, and the emulation circuit 150 forms a second filter circuit.
- the subtraction circuit 152 performs a differential operation on a detection signal S o1 outputted by the first filter circuit and a reference signal S ref outputted by the second filter circuit to output a differential detected signal S diff , as shown in FIGS. 4A and 4B , wherein FIG. 4B shows a waveform of a differential detected signal S diff of the detection signal S o1 and the reference signal S ref shown in FIG. 4A .
- the amplifying circuit 15 A includes an operational amplifier OP, a feedback resistor Rf and a compensation capacitor Cf.
- the feedback resistor Rf and the compensation capacitor Cf are connected between a negative input and an output of the operational amplifier OP.
- the input resistor R in is coupled between a second end (i.e. the signal output) of the detection electrode 131 and the negative input of the operational amplifier OP.
- a first end (i.e. the signal input) of the detection electrode 131 is coupled to the detection capacitor C in .
- a frequency response of the first filter circuit is indicated by equation (1) and the Bode diagram of FIG. 6 , wherein the first filter circuit has two poles and a zero, which is located at 0.
- V out /V in ⁇ ( Rf/R in ) ⁇ ( s ⁇ C in ⁇ R in )/(1+ s ⁇ Rf ⁇ Cf ) ⁇ (1+ s ⁇ R in ⁇ C s +s ⁇ R in ⁇ C in ) (1)
- the frequency response of the emulation circuit 150 is preferably similar to that of the first filter circuit, i.e. the frequency response of the emulation circuit 150 is determined according to a frequency response of the first filter circuit.
- the two frequency responses are similar is referred to, for example, two poles of the emulation circuit 150 being close to two poles of the first filter circuit, but not limited thereto.
- the two poles of the emulation circuit 150 are determined according to the two poles of the first filter circuit, and because the zero is not affected, only the pole frequencies are considered.
- differences between pole frequencies of two poles of the emulation circuit 150 and frequencies of poles, which correspond to the two poles of the emulation circuit 150 , of the second filter circuit is designed to be below 35 percent of the pole frequencies of the emulation circuit 150 , and preferably to be below 20 percent.
- the two poles of the emulation circuit 150 are close to the two poles of the first filter circuit as much as possible, since it is difficult to precisely know the self-capacitor C s of each detection electrode 131 in advance, the emulation circuit 150 is designed by estimation.
- the emulation circuit 150 includes an emulation detection capacitor C ref _ in , an emulation self-capacitor C ref _ s , an emulation input resistor R ref _ in and an emulation amplifying circuit 15 B, and connections between the emulation detection capacitor C ref _ in , the emulation self-capacitor C ref _ s , the emulation input resistor R ref _ in and the emulation amplifying circuit 15 B are arranged based on connections between the detection capacitor C in , the self-capacitor C s , the input resistor R in and the amplifying circuit 15 A to obtain a similar frequency response without particular limitations, e.g., having identical connections.
- the emulation self-capacitor C ref _ s is used to emulate self-capacitor C s of the detection electrode 131
- the emulation detection capacitor C ref _ in is used to emulate the detection capacitor C in
- the emulation input resistor R ref _ in corresponds to the input resistor R in
- the emulation amplifying circuit 15 B corresponds to the amplifying circuit 15 A.
- the circuit parameter of the emulation circuit 150 i.e. RC value
- the circuit parameter of the emulation circuit 150 is not necessary to be completely the same as the circuit parameter of the first filter circuit, as long as the frequency response of the emulation circuit 150 is similar to the frequency response of the first filter circuit, and the detection capacitor C s is decreased without particular limitations.
- the emulation amplifying circuit 15 B also includes an operational amplifier OP′, an emulation feedback resistor R ref _ f and an emulation compensation capacitor C ref _ f , wherein connections of elements in the emulation amplifying circuit 15 B are arranged based on those of the amplifying circuit 15 A without particular limitations, e.g., having identical connections. Therefore, a second filter circuit formed by the emulation circuit 150 also has a similar frequency response as the equation (1) and the Bode diagram of FIG. 6 . The difference is that all element parameters of the emulation circuit 150 are predesigned. Accordingly, positions of two poles are adjustable by changing the element parameters, i.e. resistance and capacitance, of the emulation circuit 150 .
- FIG. 5 it is a flow chart of an operating method of a capacitive touch device according to one embodiment of the present disclosure, including a self-capacitive mode (step S 51 ) and a mutual capacitive mode (step S 52 ).
- the self-capacitive mode and the mutual capacitive mode is separately operated, e.g., firstly identifying an approaching object and/or a window of interest (WOI) using the self-capacitive mode and identifying a touch positions and/or a gesture using the mutual capacitive mode.
- WOI window of interest
- the drive circuits 11 are respectively and electrically coupled to first ends of the drive electrodes via the detection capacitors C in
- the subtraction circuit 152 is respectively and electrically coupled to second ends of the drive electrodes.
- the subtraction circuit 152 receives a reference signal S ref outputted by the emulation circuit 150 and the subtraction circuit 152 is electrically coupled to the second end of the drive electrodes via a programmable filter 151
- the subtraction circuit 152 performs a differential operation on a detection signal S o1 outputted by the programmable filter 151 and the reference signal S ref outputted by the emulation circuit 150 to output a differential detected signal S diff , as shown in FIGS. 4A and 4B .
- a gain circuit 153 amplifies the differential detected signal S diff to make a difference between a touched differential detected signal S touch and a non-touched differential detected signal S non be more significant, as shown in FIG. 2 .
- a touch event is identified by detecting detection signals outputted by a plurality of drive electrodes or a plurality of receiving electrodes to operate in a shorter scanning period.
- detection signals outputted by a plurality of drive electrodes and a plurality of receiving electrodes are detected to identify a window of interest (WOI) on the touch panel in a self-capacitive mode. Therefore, in the self-capacitive mode, the drive circuits 11 are respectively and electrically coupled to the first ends (i.e. signal inputs) of the receiving electrodes via the detection capacitors C in , and the subtraction circuit 152 is sequentially and electrically coupled to second ends (i.e. signal outputs) of the receiving electrodes.
- the window of interest is determined after identifying the drive electrode and the receiving electrode that sense an approaching object.
- the drive electrodes and the receiving electrodes are both belong to the detection electrodes 131 to generate mutual capacitors C m therebetween.
- the drive circuits 11 are respectively and electrically coupled to the first ends of the drive electrodes without passing the detection capacitors C in .
- the drive circuits 11 bypass the detection capacitor C in using a switch SW 1 and directly input the drive signal S d to the detection electrode 131 .
- the anti-aliasing filter 154 is respectively and electrically coupled to the second ends of the drive electrodes without passing the subtraction circuit 152 .
- FIGS. 1 and 3 the drive circuits 11 bypass the detection capacitor C in using a switch SW 1 and directly input the drive signal S d to the detection electrode 131 .
- the anti-aliasing filter 154 is respectively and electrically coupled to the second ends of the drive electrodes without passing the subtraction circuit 152 .
- the anti-aliasing filter 154 bypasses the subtraction circuit 152 (and the gain circuit 153 ) using another switch SW 2 to allow the detection signal S o1 outputted by the programmable filter 151 to be directly outputted to the anti-aliasing filter 154 .
- the filter parameter of the anti-aliasing filter 154 is determined according to actual applications without particular limitation.
- the reference signal S ref is used as a cancellation to be subtracted from a detection signal.
- the amplitude (or peak-to-peak value) of a non-touched differential detected signal S non is shown to be larger than the amplitude (or peak-to-peak value) of a touched differential detected signal S touch in FIG. 2 , it is only intended to illustrate but not to limit the present disclosure. According to the parameter setting of the emulation circuit 150 (i.e. RC value), it is possible that the amplitude of the touched differential detected signal S touch is larger than the amplitude of the non-touched differential detected signal S non .
- amplitude (or peak-to-peak value) of a detection signal S o1 is shown to be larger than the amplitude (or peak-to-peak value) of a reference signal S ref in FIG. 4A , it is only intended to illustrate but not to limit the present disclosure. According to the parameter setting of the emulation circuit 150 (i.e. RC value), it is possible that the amplitude of the reference signal S ref is larger than the amplitude of the detection signal S o1 .
- the present disclosure provides a capacitive touch device ( FIGS. 1 to 3 ) and an operating method thereof ( FIG. 5 ) that generate a cancellation by disposing an emulation circuit in a control chip to decrease a size of a capacitor in the control chip used in the self-capacitive mode and improve the touch sensitivity.
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Abstract
There is provided a capacitive touch device including a touch panel and a control chip. The touch panel includes a detection electrode configured to form a self-capacitor. The control chip includes an emulation circuit and a subtraction circuit. The emulation circuit is configured to output a reference signal. The subtraction circuit is coupled to the emulation circuit and the detection electrode, subtracts the reference signal outputted by the emulation circuit from a detected signal outputted by the detection electrode to output a differential detected signal, and identifies a touch event according to an amplified differential detected signal so as to improve the touch sensitivity.
Description
- This application claims the priority benefit of Taiwan Patent Application Serial Number 104109783, filed on Mar. 26, 2015, the full disclosure of which is incorporated herein by reference.
- 1. Field of the Disclosure
- This disclosure generally relates to a touch device, more particularly, to a capacitive touch device with high sensitivity and an operating method thereof.
- 2. Description of the Related Art
- Because a user can operate a touch panel by intuition, the touch panel has been widely applied to various electronic devices. In general, the touch panel is classified into capacitive, resistive and optical touch panels.
- The capacitive touch sensor is further classified into self-capacitive touch sensors and mutual capacitive touch sensors. These two kinds of touch sensors have different characteristics of the capacitive variation, so they are adaptable to different functions. For example, the mutual capacitive touch sensors are adaptable to the multi-touch detection, and the self-capacitive touch sensors have a higher sensitivity to hovering operations and a lower sensitivity to water drops. However, how to improve the touch sensitivity of these two kinds of capacitive touch sensors is an important issue.
- Accordingly, the present disclosure provides a capacitive touch device with high sensitivity and an operating method thereof.
- The present disclosure provides a capacitive touch device and an operating method thereof in which an emulation circuit is arranged in a control chip to generate a reference signal as a cancellation of a detection signal, and thus a size of a detection capacitor in the control chip is reduced.
- The present disclosure provides a capacitive touch device and an operating method thereof in which an emulation circuit is arranged in a control chip to generate a reference signal as a cancellation of a detection signal, and thus a touch sensitivity is improved.
- The present disclosure provides a capacitive touch device including a touch panel and a control chip. The touch panel includes a detection electrode forming a self-capacitor. The control chip includes a detection capacitor, an input resistor, an amplifying circuit and an emulation circuit, wherein the detection capacitor, the self-capacitor, the input resistor and the amplifying circuit form a first filter circuit, the emulation circuit forms a second filter circuit, and a frequency response of the second filter circuit is determined according to a frequency response of the first filter circuit.
- The present disclosure further provides a capacitive touch device including a touch panel and a control chip. The touch panel includes a plurality of detection electrodes respectively forming a self-capacitor. The control chip includes an emulation circuit, a plurality of programmable filters and a subtraction circuit. The emulation circuit outputs a reference signal. The programmable filters are respectively coupled to the detection electrodes. The subtraction circuit is coupled to the emulation circuit, and configured to be sequentially coupled to the programmable filters in a self-capacitive mode and perform a differential operation on the reference signal outputted by the emulation circuit and a detection signal outputted by the coupled programmable filter to output a differential detected signal.
- The present disclosure further provides an operating method of a capacitive touch device. The capacitive touch device includes a touch panel and a control chip. The touch panel includes a plurality of drive electrodes and a plurality of receiving electrodes extending along different directions. The control chip includes a plurality of drive circuits, a plurality of detection capacitors, a subtraction circuit and an anti-aliasing filter. The operating method includes: respectively coupling, in a self-capacitive mode, the drive circuits to first ends of the drive electrodes via the detection capacitors, and respectively coupling the subtraction circuit to second ends of the drive electrodes; and respectively coupling, in a mutual capacitive mode, the drive circuits to the first ends of the drive electrodes without passing the detection capacitors, and respectively coupling the anti-aliasing filter to second ends of the receiving electrodes without passing the subtraction circuit.
- A capacitive touch device of the present disclosure is adaptable to a touch device which uses only a self-capacitive detection mode, and to a touch device which uses a dual-mode detection including the self-capacitive detection mode and a mutual capacitive detection mode.
- Other objects, advantages, and novel features of the present disclosure will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.
-
FIG. 1 is a schematic block diagram of a capacitive touch device according to one embodiment of the present disclosure. -
FIG. 2 is a schematic block diagram of a capacitive touch device according to one embodiment of the present disclosure. -
FIG. 3 is another schematic block diagram of a capacitive touch device according to one embodiment of the present disclosure. -
FIG. 4A is the waveform of a detection signal and a reference signal in the capacitive touch device of the embodiments ofFIGS. 2 and 3 . -
FIG. 4B is a waveform of a differential detected signal of the detection signal and the reference signal inFIG. 4A . -
FIG. 5 is a flow chart of an operating method of a capacitive touch device according to one embodiment of the present disclosure. -
FIG. 6 is a frequency response of a filter circuit of a capacitive touch device according to one embodiment of the present disclosure. - It should be noted that, wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.
- Please refer to
FIG. 1 , it is a schematic block diagram of a capacitive touch device according to one embodiment of the present disclosure. Thecapacitive touch device 1 includes acontrol chip 100 and atouch panel 13, wherein thecapacitive touch device 1 is preferably able to detect by a self-capacitive mode. In some embodiments, thecapacitive touch device 1 is able to detect approaching objects and distinguish touch positions by successively using a self-capacitive mode and a mutual capacitive mode. For example, in some embodiments, because a scanning interval of the self-capacitive mode is short, thecapacitive touch device 1 is able to identify whether any object is approaching using the self-capacitive mode. After an approaching object is identified, a touch position is identified using the mutual capacitive mode. In other embodiments, thecapacitive touch device 1 is able to identify a rough position of an approaching object and determine a window of interest (WOI) on thetouch panel 13 with the self-capacitive mode, and then identify a fine position within the window of interest with the mutual capacitive mode to reduce data amount to be processed in the mutual capacitive mode. It should be mention that implementations of the self-capacitive mode and the mutual capacitive mode mentioned above are only intended to illustrate, but not to limit the present disclosure. - The
touch panel 13 includes a plurality ofdetection electrodes 131 to respectively form a self-capacitor Cs, wherein thedetection electrodes 131 include a plurality of drive electrodes and a plurality of receiving electrodes extending along different directions, e.g., perpendicular to each other. Mutual capacitors Cm (referring toFIGS. 2 and 3 ) are formed between the drive electrodes and the receiving electrodes. The principle of forming self-capacitors and mutual capacitors in a capacitive touch panel is known and is not an object of the present disclosure, and thus details thereof is not described herein. - The
control chip 100 includes a plurality ofdrive circuits 11, a plurality of detection capacitors Cin and anemulation circuit 150, wherein theemulation circuit 150 is used to emulate the characteristics of the detection line in a self-capacitive mode (described hereinafter). In the self-capacitive mode, thedrive circuits 11 and the detection capacitors Cin are electrically coupled to signal inputs of thedetection electrodes 131 via pins. Thedrive circuits 11 output a drive signal Sd, e.g., a sine wave, a cosine wave or a square wave to thedetection electrodes 131. In a mutual capacitive mode, only thedrive circuit 11 corresponding to the drive electrode outputs the drive signal Sd, whereas thedrive circuit 11 corresponding to the receiving electrode is bypassed. - Please refer to
FIG. 2 , it is a schematic block diagram of a capacitive touch device according to one embodiment of the present disclosure. As mentioned above, thecapacitive touch device 1 includes atouch panel 13 and acontrol chip 100. Thecontrol chip 100 includes a plurality ofdrive circuits 11, a plurality of detection capacitors Cin, ananalog front end 15 and adigital back end 16, wherein as thedigital back end 16 is not an object of the present disclosure, details thereof are not described herein. In the present disclosure, thedrive circuits 11 are able to be electrically coupled to signal inputs of thedetection electrodes 131 via the detection capacitors Cin (e.g. in the self-capacitive mode) or bypassing the detection capacitors Cin (e.g. in the mutual capacitive mode), wherein said coupled to and bypassing the detection capacitors Cin is able to be implemented by arranging a plurality of switches SW1 between thedrive circuits 11 and thetouch panel 13. - The analog
front end 15 includes anemulation circuit 150, a plurality ofprogrammable filters 151, a subtraction circuit 52, again circuit 153 and an anti-aliasing filter (AAF) 154. Theprogrammable filters 151, the detection capacitors Cin and the self-capacitors Cs of thedetection electrodes 131 form a first filter circuit, wherein the first filter circuit is, e.g., a band-pass filter (BPF) or a high-pass filter (HPF). The first filter circuit is able to further form a band-pass filter having a predetermined bandwidth with a low-pass filter formed by theanti-aliasing filter 154. In one embodiment, the signal output of eachdetection electrode 131 is coupled to (e.g. via a switch) oneprogrammable filter 151. It should be mentioned that although only the horizontally arrangeddetection electrodes 131 shown inFIGS. 2 and 3 are coupled to theprogrammable filters 151, in other embodiments theprogrammable filters 151 are also coupled to the longitudinally arrangeddetection electrodes 131, and the present disclosure is not limited to those shown inFIGS. 2 and 3 . - The
emulation circuit 150 forms a second filter circuit and outputs a reference signal Sref, wherein the second filter circuit is, e.g., a band-pass filter or a high-pass filter. The second filter circuit is able to further form a band-pass filter having a predetermined bandwidth with a low-pass filter formed by theanti-aliasing filter 154. Thesubtraction circuit 152 is coupled to theemulation circuit 150 and is sequentially and electrically coupled to theprogrammable filters 151 via switches SW2 in a self-capacitive mode to be further electrically coupled to thedetection electrodes 131. Thesubtraction circuit 152 performs a differential operation on the reference signal Sref outputted by theemulation circuit 150 and a detection signal So1 outputted by the coupledprogrammable filter 151 to output a differential detected signal Sdiff. To be more precisely, in the present disclosure, the detection capacitors Cin are respectively and electrically coupled to signal inputs of thedetection electrodes 131 via a plurality of switches (e.g. SW1), and thesubtraction circuit 152 is respectively and electrically coupled to theprogrammable filters 151 and thedetection electrodes 131 via a plurality of switches (e.g. SW2). - In the present disclosure, the detection capacitor Cin is disposed in the
control chip 100 to form the voltage division with the self-capacitor Cs. Accordingly, thecapacitive touch device 1 identifies a touch event according to a variation of peak-to-peak values of the differential detected signal Sdiff, wherein the differential detected signal Sdiff is a continuous signal. Before a touch event is identified, the differential detected signal Sdiff is further filtered or digitized. For example,FIG. 2 shows the touched differential detected signal Stouch and the non-touched differential detected signal Snon. However, as the self-capacitor Cs is generally very large, an effective voltage division is implemented by using a large detection capacitor Cin. Therefore, the considerable disposition space in the chip for the large capacitor is necessary such that a total size of thecontrol chip 100 is unable to be reduced. - Accordingly, in the present disclosure, the circuit characteristics of the detection line (e.g. from the
drive circuit 11 via the detection capacitor Cin, thedetection electrode 131 and the programmable filter 151) is emulated by disposing theemulation circuit 150 to output the reference signal Sref as a cancellation of the detection signal So1, as shown inFIG. 4 . The capacitance of the detection capacitor Cin is able to be decreased by subtracting the cancellation from the detection signal So1. For example, the capacitance of the detection capacitor Cin is preferably smaller than 10 percent of capacitance of the self-capacitor Cs. Therefore, the size of thecontrol chip 100 is effectively decreased. - To make a difference between the touched differential detected signal Stouch and the non-touched differential detected signal Snon be more obvious, in some embodiments a
gain circuit 153 is employed to amplify the differential detected signal Sdiff, wherein a gain of thegain circuit 153 is determined according to an analytical range of an analog-to-digital convertor (ADC) of the digitalback end 16, but not limited thereto. As shown inFIG. 2 , the difference between the touched differential detected signal Stouch and the non-touched differential detected signal Snon, which are signals (i.e. differential detected signal) outputted by thegain circuit 153, is increased such that a touch event is easier to be identified. Theanti-aliasing filter 154 filters the amplified differential detected signal and, as mentioned above, theanti-aliasing filter 154 is, for example, a low-pass filter. - Please refer to
FIG. 3 , it is another schematic block diagram of a capacitive touch device according to one embodiment of the present disclosure, whereinFIG. 3 further shows an implementation of theemulation circuit 150 and theprogrammable filter 151. - In some embodiments, the
programmable filter 151 includes an input resistor Rin and anamplifying circuit 15A, wherein the detection capacitor Cin, the self-capacitor Cs, the input resistor Rin and the amplifyingcircuit 15A form a first filter circuit, and theemulation circuit 150 forms a second filter circuit. As mentioned above, thesubtraction circuit 152 performs a differential operation on a detection signal So1 outputted by the first filter circuit and a reference signal Sref outputted by the second filter circuit to output a differential detected signal Sdiff, as shown inFIGS. 4A and 4B , whereinFIG. 4B shows a waveform of a differential detected signal Sdiff of the detection signal So1 and the reference signal Sref shown inFIG. 4A . - In one embodiment, the amplifying
circuit 15A includes an operational amplifier OP, a feedback resistor Rf and a compensation capacitor Cf. The feedback resistor Rf and the compensation capacitor Cf are connected between a negative input and an output of the operational amplifier OP. The input resistor Rin is coupled between a second end (i.e. the signal output) of thedetection electrode 131 and the negative input of the operational amplifier OP. A first end (i.e. the signal input) of thedetection electrode 131 is coupled to the detection capacitor Cin. In this embodiment, a frequency response of the first filter circuit is indicated by equation (1) and the Bode diagram ofFIG. 6 , wherein the first filter circuit has two poles and a zero, which is located at 0. -
(V out /V in)=−(Rf/R in)×(s·C in ·R in)/(1+s·Rf·Cf)×(1+s·R in ·C s +s·R in ·C in) (1) - As mentioned above, because an output of the
emulation circuit 150 is used as a cancellation of the first filter circuit, the frequency response of theemulation circuit 150 is preferably similar to that of the first filter circuit, i.e. the frequency response of theemulation circuit 150 is determined according to a frequency response of the first filter circuit. In some embodiments, the two frequency responses are similar is referred to, for example, two poles of theemulation circuit 150 being close to two poles of the first filter circuit, but not limited thereto. For example, the two poles of theemulation circuit 150 are determined according to the two poles of the first filter circuit, and because the zero is not affected, only the pole frequencies are considered. For example, differences between pole frequencies of two poles of theemulation circuit 150 and frequencies of poles, which correspond to the two poles of theemulation circuit 150, of the second filter circuit is designed to be below 35 percent of the pole frequencies of theemulation circuit 150, and preferably to be below 20 percent. Although the two poles of theemulation circuit 150 are close to the two poles of the first filter circuit as much as possible, since it is difficult to precisely know the self-capacitor Cs of eachdetection electrode 131 in advance, theemulation circuit 150 is designed by estimation. - In one embodiment, the
emulation circuit 150 includes an emulation detection capacitor Cref _ in, an emulation self-capacitor Cref _ s, an emulation input resistor Rref _ in and anemulation amplifying circuit 15B, and connections between the emulation detection capacitor Cref _ in, the emulation self-capacitor Cref _ s, the emulation input resistor Rref _ in and theemulation amplifying circuit 15B are arranged based on connections between the detection capacitor Cin, the self-capacitor Cs, the input resistor Rin and the amplifyingcircuit 15A to obtain a similar frequency response without particular limitations, e.g., having identical connections. That is, the emulation self-capacitor Cref _ s is used to emulate self-capacitor Cs of thedetection electrode 131, the emulation detection capacitor Cref _ in is used to emulate the detection capacitor Cin, the emulation input resistor Rref _ in corresponds to the input resistor Rin, and theemulation amplifying circuit 15B corresponds to the amplifyingcircuit 15A. It should be mentioned that the circuit parameter of the emulation circuit 150 (i.e. RC value) is not necessary to be completely the same as the circuit parameter of the first filter circuit, as long as the frequency response of theemulation circuit 150 is similar to the frequency response of the first filter circuit, and the detection capacitor Cs is decreased without particular limitations. - The
emulation amplifying circuit 15B also includes an operational amplifier OP′, an emulation feedback resistor Rref _ f and an emulation compensation capacitor Cref _ f, wherein connections of elements in theemulation amplifying circuit 15B are arranged based on those of the amplifyingcircuit 15A without particular limitations, e.g., having identical connections. Therefore, a second filter circuit formed by theemulation circuit 150 also has a similar frequency response as the equation (1) and the Bode diagram ofFIG. 6 . The difference is that all element parameters of theemulation circuit 150 are predesigned. Accordingly, positions of two poles are adjustable by changing the element parameters, i.e. resistance and capacitance, of theemulation circuit 150. - Please refer to
FIG. 5 , it is a flow chart of an operating method of a capacitive touch device according to one embodiment of the present disclosure, including a self-capacitive mode (step S51) and a mutual capacitive mode (step S52). In this embodiment, the self-capacitive mode and the mutual capacitive mode is separately operated, e.g., firstly identifying an approaching object and/or a window of interest (WOI) using the self-capacitive mode and identifying a touch positions and/or a gesture using the mutual capacitive mode. - In the self-capacitive mode, the
drive circuits 11 are respectively and electrically coupled to first ends of the drive electrodes via the detection capacitors Cin, and thesubtraction circuit 152 is respectively and electrically coupled to second ends of the drive electrodes. Meanwhile, because thesubtraction circuit 152 receives a reference signal Sref outputted by theemulation circuit 150 and thesubtraction circuit 152 is electrically coupled to the second end of the drive electrodes via aprogrammable filter 151, thesubtraction circuit 152 performs a differential operation on a detection signal So1 outputted by theprogrammable filter 151 and the reference signal Sref outputted by theemulation circuit 150 to output a differential detected signal Sdiff, as shown inFIGS. 4A and 4B . Then, again circuit 153 amplifies the differential detected signal Sdiff to make a difference between a touched differential detected signal Stouch and a non-touched differential detected signal Snon be more significant, as shown inFIG. 2 . Furthermore, in one embodiment, a touch event is identified by detecting detection signals outputted by a plurality of drive electrodes or a plurality of receiving electrodes to operate in a shorter scanning period. - In another embodiment, detection signals outputted by a plurality of drive electrodes and a plurality of receiving electrodes are detected to identify a window of interest (WOI) on the touch panel in a self-capacitive mode. Therefore, in the self-capacitive mode, the
drive circuits 11 are respectively and electrically coupled to the first ends (i.e. signal inputs) of the receiving electrodes via the detection capacitors Cin, and thesubtraction circuit 152 is sequentially and electrically coupled to second ends (i.e. signal outputs) of the receiving electrodes. The window of interest is determined after identifying the drive electrode and the receiving electrode that sense an approaching object. As mentioned above, in the present disclosure the drive electrodes and the receiving electrodes are both belong to thedetection electrodes 131 to generate mutual capacitors Cm therebetween. - In the mutual capacitive mode, the
drive circuits 11 are respectively and electrically coupled to the first ends of the drive electrodes without passing the detection capacitors Cin. For example inFIGS. 2 and 3 , thedrive circuits 11 bypass the detection capacitor Cin using a switch SW1 and directly input the drive signal Sd to thedetection electrode 131. Besides, theanti-aliasing filter 154 is respectively and electrically coupled to the second ends of the drive electrodes without passing thesubtraction circuit 152. For example inFIGS. 2 and 3 , theanti-aliasing filter 154 bypasses the subtraction circuit 152 (and the gain circuit 153) using another switch SW2 to allow the detection signal So1 outputted by theprogrammable filter 151 to be directly outputted to theanti-aliasing filter 154. The filter parameter of theanti-aliasing filter 154 is determined according to actual applications without particular limitation. - In the present disclosure, in the self-capacitive mode because signals sent to the detection lines do not pass resistors and capacitors of the panel, a phase difference between the reference line (i.e. emulation circuit) and the detection line is not obvious. Therefore, the reference signal Sref is used as a cancellation to be subtracted from a detection signal.
- It should be mentioned that, although the amplitude (or peak-to-peak value) of a non-touched differential detected signal Snon is shown to be larger than the amplitude (or peak-to-peak value) of a touched differential detected signal Stouch in
FIG. 2 , it is only intended to illustrate but not to limit the present disclosure. According to the parameter setting of the emulation circuit 150 (i.e. RC value), it is possible that the amplitude of the touched differential detected signal Stouch is larger than the amplitude of the non-touched differential detected signal Snon. - It should be mentioned that although the amplitude (or peak-to-peak value) of a detection signal So1 is shown to be larger than the amplitude (or peak-to-peak value) of a reference signal Sref in
FIG. 4A , it is only intended to illustrate but not to limit the present disclosure. According to the parameter setting of the emulation circuit 150 (i.e. RC value), it is possible that the amplitude of the reference signal Sref is larger than the amplitude of the detection signal So1. - As mentioned above, how to improve the touch sensitivity of a capacitive touch device is an important issue. Therefore, the present disclosure provides a capacitive touch device (
FIGS. 1 to 3 ) and an operating method thereof (FIG. 5 ) that generate a cancellation by disposing an emulation circuit in a control chip to decrease a size of a capacitor in the control chip used in the self-capacitive mode and improve the touch sensitivity. - Although the disclosure has been explained in relation to its preferred embodiment, it is not used to limit the disclosure. It is to be understood that many other possible modifications and variations can be made by those skilled in the art without departing from the spirit and scope of the disclosure as hereinafter claimed.
Claims (20)
1. A capacitive touch device comprising:
a touch panel comprising a detection electrode configured to form a self-capacitor; and
a control chip comprising a detection capacitor, an input resistor, an amplifying circuit and an emulation circuit, wherein
the detection capacitor, the self-capacitor, the input resistor and the amplifying circuit are configured to form a first filter circuit,
the emulation circuit is configured to form a second filter circuit, and
a frequency response of the second filter circuit is determined according to a frequency response of the first filter circuit.
2. The capacitive touch device as claimed in claim 1 , further comprising a subtraction circuit configured to perform a differential operation on a detection signal outputted by the first filter circuit and a reference signal outputted by the second filter circuit to output a differential detected signal.
3. The capacitive touch device as claimed in claim 2 , further comprising a gain circuit configured to amplify the differential detected signal.
4. The capacitive touch device as claimed in claim 3 , wherein the capacitive touch device is configured to identify a touch event according to a variation of peak-to-peak values of the amplified differential detected signal.
5. The capacitive touch device as claimed in claim 1 , wherein capacitance of the detection capacitor is smaller than 10 percent of capacitance of the self-capacitor.
6. The capacitive touch device as claimed in claim 1 , wherein differences between pole frequencies of two poles of the first filter circuit and frequencies of poles, which correspond to the two poles of the first filter circuit, of the second filter circuit is lower than 35 percent of the pole frequencies of the first filter circuit.
7. The capacitive touch device as claimed in claim 1 , wherein
the amplifying circuit comprises an operational amplifier, a feedback resistor and a compensation capacitor,
the feedback resistor and the compensation capacitor are connected between a negative input and an output of the operational amplifier,
the input resistor is coupled between a second end of the detection electrode and the negative input of the operational amplifier, and
a first end of the detection electrode is coupled to the detection capacitor.
8. The capacitive touch device as claimed in claim 7 , wherein
the emulation circuit comprises an emulation detection capacitor, an emulation self-capacitor, an emulation input resistor and an emulation amplifying circuit, and
connections between the emulation detection capacitor, the emulation self-capacitor, the emulation input resistor and the emulation amplifying circuit are arranged based on connections between the detection capacitor, the self-capacitor, the input resistor and the amplifying circuit.
9. A capacitive touch device comprising:
a touch panel comprising a plurality of detection electrodes configured to respectively form a self-capacitor; and
a control chip comprising:
an emulation circuit configured to output a reference signal;
a plurality of programmable filters respectively coupled to the detection electrodes; and
a subtraction circuit, coupled to the emulation circuit, configured to be sequentially coupled to the programmable filters in a self-capacitive mode, and perform a differential operation on the reference signal outputted by the emulation circuit and a detection signal outputted by the coupled programmable filter to output a differential detected signal.
10. The capacitive touch device as claimed in claim 9 , wherein the control chip further comprises a gain circuit configured to amplify the differential detected signal.
11. The capacitive touch device as claimed in claim 10 , wherein the capacitive touch device is configured to identify a touch event according to a variation of peak-to-peak values of the amplified differential detected signal.
12. The capacitive touch device as claimed in claim 9 , further comprising a plurality of detection capacitors configured to be electrically coupled to signal inputs of the detection electrodes in the self-capacitive mode.
13. The capacitive touch device as claimed in claim 12 , wherein the programmable filter, the self-capacitor and the detection capacitor are configured to form a first filter circuit.
14. The capacitive touch device as claimed in claim 13 , wherein the emulation circuit is configured to form a second filter circuit, and a frequency response of the second filter circuit is determined according to a frequency response of the first filter circuit.
15. The capacitive touch device as claimed in claim 12 , wherein capacitance of the detection capacitors is smaller than 10 percent of capacitance of the self-capacitor.
16. The capacitive touch device as claimed in claim 12 , wherein
the detection capacitors are respectively coupled to the detection electrodes via a plurality of switches, and
the subtraction circuit is coupled to the programmable filters respectively via a plurality of switches.
17. An operating method of a capacitive touch device, the capacitive touch device comprising a touch panel and a control chip, the touch panel comprising a plurality of drive electrodes and a plurality of receiving electrodes extending along different directions, and the control chip comprising a plurality of drive circuits, a plurality of detection capacitors, a subtraction circuit and an anti-aliasing filter, the operating method comprising:
respectively coupling, in a self-capacitive mode, the drive circuits to first ends of the drive electrodes via the detection capacitors, and respectively coupling the subtraction circuit to second ends of the drive electrodes; and
respectively coupling, in a mutual capacitive mode, the drive circuits to the first ends of the drive electrodes without passing the detection capacitors, and respectively coupling the anti-aliasing filter to second ends of the receiving electrodes without passing the subtraction circuit.
18. The operating method as claimed in claim 17 , further comprising:
respectively coupling, in the self-capacitive mode, the drive circuits to first ends of the receiving electrodes via the detection capacitors, and
respectively coupling, in the self-capacitive mode, the subtraction circuit to the second ends of the receiving electrodes.
19. The operating method as claimed in claim 17 , wherein the control chip further comprises an emulation circuit and a programmable filter, the subtraction circuit is electrically coupled to the second ends of the drive electrodes via the programmable filter, and the operating method further comprises:
performing a differential operation on a detection signal outputted by the programmable filter and a reference signal outputted by the emulation circuit to output a differential detected signal;
amplifying the differential detected signal; and
identifying a touch event according to a variation of peak-to-peak values of the amplified differential detected signal.
20. The operating method as claimed in claim 19 , wherein
the programmable filter, the detection capacitors and self-capacitors of the drive electrodes form a first filter circuit,
the emulation circuit forms a second filter circuit, and
a frequency response of the second filter circuit is determined according to a frequency response of the first filter circuit.
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US17/021,169 US11592936B2 (en) | 2015-03-26 | 2020-09-15 | Capacitive touch device with high sensitivity and low power consumption |
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Also Published As
Publication number | Publication date |
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US20190042029A1 (en) | 2019-02-07 |
TWI550495B (en) | 2016-09-21 |
US20200371623A1 (en) | 2020-11-26 |
US11599221B2 (en) | 2023-03-07 |
US10775945B2 (en) | 2020-09-15 |
TW201635124A (en) | 2016-10-01 |
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