CAPACITIVE TOUCH DEVICE WITH HIGH SENSITIVITY AND OPERATING METHOD THEREOF
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.
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.
BACKGROUND1. 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.
SUMMARYAccordingly, 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.
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
The touch panel 13 includes a plurality of detection electrodes 131 to respectively form a self-capacitor Cs, 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 Cm (referring to
The control chip 100 includes a plurality of drive circuits 11, a plurality of detection capacitors Cin 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). In the self-capacitive mode, the drive circuits 11 and the detection capacitors Cin 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. In 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.
Please refer to
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 Cin and the self-capacitors Cs 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). 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. In one embodiment, the signal output of 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
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 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 SW2 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 Sref outputted by the emulation circuit 150 and a detection signal So1 outputted by the coupled programmable 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 the detection electrodes 131 via a plurality of switches (e.g. SW1), 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. 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, the capacitive 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,
Accordingly, in the present disclosure, the circuit characteristics of the detection line (e.g. from the drive circuit 11 via the detection capacitor Cin, the detection electrode 131 and the programmable filter 151) is emulated by disposing the emulation circuit 150 to output the reference signal Sref as a cancellation of the detection signal So1, as shown in
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 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. As shown in
Please refer to
In some embodiments, the programmable filter 151 includes an input resistor Rin and an amplifying circuit 15A, wherein the detection capacitor Cin, the self-capacitor Cs, the input resistor Rin and the amplifying circuit 15A form a first filter circuit, and the emulation circuit 150 forms a second filter circuit. As mentioned above, the subtraction 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 in
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 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 Cin. In this embodiment, a frequency response of the first filter circuit is indicated by equation (1) and the Bode diagram of
(Vout/Vin)=−(Rf/Rin)×(s·Cin·Rin)/(1+s·Rf·Cf)×(1+s·Rin·Cs+s·Rin·Cin) (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 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. In some embodiments, 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. For example, 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. For example, 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. Although 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 Cs of each detection electrode 131 in advance, the emulation 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 an emulation 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 the emulation amplifying circuit 15B are arranged based on connections between the detection capacitor Cin, the self-capacitor Cs, the input resistor Rin and the amplifying circuit 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 the detection 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 the emulation amplifying circuit 15B corresponds to the amplifying circuit 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 the emulation 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 the emulation amplifying circuit 15B are arranged based on those of the amplifying circuit 15A 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
Please refer to
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 the subtraction circuit 152 is respectively and electrically coupled to second ends of the drive electrodes. Meanwhile, because the subtraction circuit 152 receives a reference signal Sref 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 So1 outputted by the programmable filter 151 and the reference signal Sref outputted by the emulation circuit 150 to output a differential detected signal Sdiff, as shown in
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 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. As mentioned above, in the present disclosure the drive electrodes and the receiving electrodes are both belong to the detection 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 in
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
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
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 (
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
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.
Type: Application
Filed: Mar 25, 2016
Publication Date: Sep 29, 2016
Inventor: Sung-Han WU (Hsin-Chu County)
Application Number: 15/080,718