CN109144305B

CN109144305B - High-sensitivity capacitive touch device and operation method thereof

Info

Publication number: CN109144305B
Application number: CN201810155262.3A
Authority: CN
Inventors: 巫松翰
Original assignee: Pixart Imaging Inc
Current assignee: Pixart Imaging Inc
Priority date: 2017-06-27
Filing date: 2018-02-23
Publication date: 2021-07-27
Anticipated expiration: 2038-02-23
Also published as: CN109144305A

Abstract

A capacitive touch device comprises a touch panel and a control chip. The touch panel comprises a detection electrode for forming self-inductance and mutual-inductance capacitance. The control chip comprises a simulation circuit and a subtraction circuit. The simulation circuit is used for outputting a reference signal. The subtraction circuit is coupled with the simulation circuit and the detection electrode, performs differential operation on the reference signal output by the simulation circuit and the detection signal output by the detection electrode to output a differential detection signal, and identifies a contact event according to the differential detection signal, so as to save electric energy required by contact detection.

Description

High-sensitivity capacitive touch device and operation method thereof

Technical Field

The present invention relates to a touch device, and more particularly, to a high-sensitivity capacitive touch device and an operating method thereof.

Background

Touch panels are widely used in various electronic devices because they allow users to intuitively operate the touch panels. Touch panels can be generally classified into capacitive, resistive, and optical touch panels.

The capacitive touch device can be further divided into a self-capacitive touch sensor and a mutual capacitive touch sensor, which have different capacitance variation characteristics and are suitable for different functions. For example, the mutual capacitance type touch device can be used for multi-touch detection (multi-touch detection) and the self-capacitance type touch device has higher sensitivity to the floating operation and lower sensitivity to the water drop. However, in both of these capacitive touch devices, how to improve the touch sensitivity is an important issue.

Disclosure of Invention

In view of the above, the present invention provides a capacitive touch device with high sensitivity.

The invention provides a capacitive touch device, wherein a simulation circuit is arranged in a control chip and used for generating a reference signal as an elimination value (cancellation) of a detection signal so as to reduce the size of a detection capacitor in the control chip.

The invention provides a capacitive touch device, wherein an emulation circuit is arranged in a control chip to generate a reference signal as an elimination value of a detection signal so as to increase the sensitivity of touch detection.

The invention provides a capacitive touch device which comprises a touch panel, an amplifying circuit, a simulation circuit and a subtraction circuit. The touch panel includes a detection electrode. The amplifying circuit is coupled with the detection electrode and used for outputting a first detection signal when the detection electrode is not in inductive contact and outputting a second detection signal when the detection electrode is in inductive contact. The simulation circuit is used for outputting a reference signal. The subtraction circuit is configured to perform a differential operation on the reference signal and the first detection signal to generate a first differential detection signal, and perform a differential operation on the reference signal and the second detection signal to generate a second differential detection signal, wherein the first differential detection signal and the second differential detection signal are in an inverted phase.

The invention also provides a capacitive touch device, which comprises a touch panel, a detection capacitor, an input resistor, an amplifying circuit, a simulation circuit and a subtraction circuit. The touch panel comprises a detection electrode, and is used for operating in a self-capacitance detection mode or a mutual capacitance detection mode. The detection capacitor is configured to couple to a signal input of the detection electrode in the self-capacitance detection mode and not couple to the signal input of the detection electrode in the mutual-capacitance detection mode. The input resistor is coupled with the signal output end of the detection electrode. The amplifying circuit is coupled with the input resistor and used for outputting a detection signal. The simulation circuit comprises a simulation detection capacitor, a simulation self-inductance capacitor, a simulation mutual inductance capacitor, a simulation input resistor and a simulation amplifying circuit, and is used for outputting a first reference signal according to the simulation detection capacitor, the simulation self-inductance capacitor, the simulation input resistor and the simulation amplifying circuit in the self-capacitance detection mode or outputting a second reference signal according to the simulation mutual inductance capacitor, the simulation input resistor and the simulation amplifying circuit in the mutual-capacitance detection mode. The subtraction circuit is configured to perform a differential operation on the detection signal and the first reference signal in the self-capacitance detection mode or perform a differential operation on the detection signal and the second reference signal in the mutual-capacitance detection mode to generate a differential detection signal.

The invention also provides a capacitive touch device, which comprises a touch panel, an input resistor, an amplifying circuit, a flash memory, a digital-to-analog converter and a subtracting circuit. The touch panel includes a detection electrode. The input resistor is coupled with the signal output end of the detection electrode. The amplifying circuit is coupled with the input resistor and used for outputting a detection signal. The flash memory stores at least one digital data in advance. The digital-to-analog converter is used for outputting at least one reference signal according to the at least one digital data. The subtraction circuit is used for carrying out a differential operation on the detection signal and the at least one reference signal to generate a differential detection signal.

The capacitive touch device described in the present invention can be applied to a touch device using only self-capacitance detection and a touch device using dual-mode detection (dual-mode detection) using both self-capacitance detection and mutual capacitance detection.

In order that the manner in which the above recited and other objects, features and advantages of the present invention are obtained will become more apparent, a more particular description of the invention briefly described below will be rendered by reference to the appended drawings. In the description of the present invention, the same components are denoted by the same reference numerals and will be described later.

Drawings

Fig. 1 is a block diagram of a capacitive touch device according to an embodiment of the invention;

fig. 2 is a block diagram of a capacitive touch device according to an embodiment of the invention;

fig. 3 is another schematic block diagram of a capacitive touch device according to an embodiment of the invention;

FIG. 4A is a waveform of a detection signal and a reference signal in the capacitive touch device of the embodiment of FIGS. 2-3;

FIG. 4B is a waveform of a differential detection signal of the detection signal of FIG. 4A and a reference signal;

fig. 5 is a flowchart illustrating an operating method of a capacitive touch device according to an embodiment of the invention;

fig. 6 is a frequency response of a filter circuit of a capacitive touch device according to an embodiment of the invention;

FIG. 7 is a block diagram of a capacitive touch device according to another embodiment of the present invention;

fig. 8A is a circuit diagram of a simulation circuit of a capacitive touch device according to another embodiment of the invention;

fig. 8B is a block diagram of a simulation circuit of a capacitive touch device according to another embodiment of the invention;

9A-9B are circuit diagrams of phase reference circuits of a capacitive touch device according to another embodiment of the invention; and

fig. 9C-9D are block diagrams of phase reference circuits of a capacitive touch device according to another embodiment of the invention.

Description of the reference numerals

1 capacitive touch device

11 drive circuit

13 touch panel

131 detection electrode

15 analog front end

150' simulation circuit

15A amplifying circuit

152 subtraction circuit

155 detection circuit

156 phase reference circuit

16 digital back end

C_inDetecting capacitance

C_mEach otherInductive capacitor

C_SSelf-inductance capacitor

R_inInput resistance

S_o1Detecting the signal

S_ref' reference Signal

S_diffDifferential detection signal

S_prefA phase reference signal.

Detailed Description

Fig. 1 is a block diagram of a capacitive touch device according to an embodiment of the invention. The capacitive touch device 1 includes a control chip 100 and a touch panel 13; preferably, the capacitive touch device 1 can be detected by using a self-capacitance detection mode (self-capacitance mode). In some embodiments, the capacitive touch device 1 can detect a proximity object and determine a touch position by using a self capacitive detection mode and a mutual capacitive detection mode (mutual capacitive mode) in a time-sharing manner. For example, in some embodiments, since the scanning period of the self-capacitance detection mode is short, the capacitive touch device 1 may first identify whether an object is approaching by using the self-capacitance detection mode, and then identify a touch position by using the mutual capacitance detection mode when it is determined that an object is approaching; in other embodiments, the capacitive touch device 1 may first determine a rough position (rough position) of an approaching object and determine a desired detection range (WOI) by using the self-capacitance detection mode, and then identify a precise position (fine position) in the desired detection range by using the mutual capacitance detection mode, so as to reduce the amount of data required to be processed in the mutual capacitance detection mode. It should be noted that the above embodiments of the self-capacitance detection mode and the mutual capacitance detection mode are only used for illustration, but not for limiting the invention.

The touch panel 13 includes a plurality of detecting electrodes 131 for forming self-inductance capacitors C respectively_s(ii) a The detecting electrode 131 includes a plurality of driving electrodes and a plurality of receiving electrodes extending in different directions, such as perpendicular to each other, and a mutual inductance capacitance C can be formed between the driving electrodes and the receiving electrodes_m(see FIGS. 2 and 3). Capacitor with a capacitor elementThe principle of forming the self-inductance capacitor and the mutual-inductance capacitor in the touch panel is known and is not the subject of the description of the present invention, and therefore, the description thereof is omitted.

The control chip 100 includes a plurality of driving circuits 11 and a plurality of detecting capacitors C_inAnd a simulation circuit 150; the simulation circuit 15 is used to simulate the circuit characteristics of the detection circuit in the self-contained detection mode (for example, detailed later). In the self-capacitance detection mode, the driving circuit 11 and the detection capacitor C_inA signal input terminal electrically coupled to the detection electrode 131 through a pin (pin). The driving circuit 11 is configured to output a driving signal Sd, such as a sine wave, a cosine wave, a square wave, etc., to the detecting electrode 131. In the mutual capacitance detection mode, only the driving circuit 11 corresponding to the driving electrode outputs the driving signal Sd, and the driving circuit 11 corresponding to the receiving electrode is opened.

Fig. 2 is a block diagram illustrating a capacitive touch device according to an embodiment of the invention. As described above, the capacitive touch device 1 includes the touch panel 13 and the control chip 100. The control chip 100 includes a plurality of driving circuits 11 and a plurality of detecting capacitors C_inAn analog front end 15 and a digital back end 16; the digital backend 16 is not a subject of the description of the present invention, and therefore, is not described herein again. In the present invention, the driving circuit 11 can pass through the detection capacitor C_inA signal input terminal electrically coupled to the detecting electrode 131 (e.g. in a self-capacitance detecting mode), or the detecting capacitor C can be bypassed (bypass)_inA signal input terminal electrically coupled to the detection electrode 131 (e.g., in a mutual capacitance detection mode); wherein, a plurality of change-over switches SW can be arranged₁Between the driving circuit 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-noise filter (AAF) 154. The programmable filter 151 and the detection capacitor C_inAnd a self-inductance capacitance C of the detection electrode 131_sForming a first filter circuit; wherein the first filter circuit is, for example, a band-pass filter (BPF) or a high-pass filter (b:)HPF), the first filter circuit may further form a band pass filter having a predetermined bandwidth with the low pass filter formed by the anti-noise filter 154. In one embodiment, the signal output terminal of each detection electrode 131 is connected (e.g., via a switch element) to the programmable filter 151. It should be noted that although FIGS. 2 and 3 only show the laterally disposed detecting electrodes 131 connected to the programmable filter 151, in other embodiments, the programmable filter 151 is also connected to the longitudinally disposed detecting electrodes 131, and is not limited to that shown in FIGS. 2-3. The connection manner of the programmable filter 151 may be determined according to the operation mode of the capacitive touch device 1.

The simulation circuit 150 forms a second filter circuit and is configured to output a reference signal S_ref(ii) a The second filter circuit is, for example, a band-pass filter circuit or a high-pass filter circuit, and the second filter circuit may further form a band-pass filter with a predetermined bandwidth with the low-pass filter formed by the anti-noise filter 154. The subtraction circuit 152 is coupled to the simulation circuit 150 for passing through the switch SW in the self-capacitance detection mode₂The programmable filter 151 is electrically coupled to the detecting electrode 131. The subtraction circuit 152 is used for subtracting the reference signal S output by the simulation circuit 150_refThe detection signal S outputted from the programmable filter 151 coupled thereto_o1Performing a differential operation to output a differential detection signal S_diff. More particularly, in the present specification, the detection capacitor C_inBy a plurality of change-over switches (e.g. SW)₁) Are electrically coupled to the signal input terminals of the detecting electrodes 131 respectively, and the subtracting circuit 152 is connected to the detecting electrodes through a plurality of switches (e.g. SW)₂) Are electrically coupled to the programmable filter 151 and the detecting electrode 131, respectively.

In the present specification, the detection capacitor C_inDisposed in the control chip 100 for connecting with a self-inductance capacitor C_sA partial pressure is formed. Thereby, the capacitive touch device 1 can detect the signal S according to the difference_diffA peak-to-peak value (peak-to-peak values) change of (a) determines a contact event; wherein the differential detection signal S_diffIs a time continuous signal; wherein the differential detection signal S is used before the touch event is determined_diffMay be further filtered, digitized, etc. For example, FIG. 2 shows a touch differential sense signal S_{Contact with}And no-contact differential detection signal S_{Is not in contact with}. However, due to the self-inductance capacitance C_sUsually quite large, so that a large sensing capacitor C is required to achieve effective voltage division_inTherefore, a relative installation space is required in the wafer, and the overall size of the control wafer 100 cannot be reduced.

Therefore, in the present description, the emulation circuit 150 is configured to simulate the detection line (e.g., from the driving circuit 11 through the detection capacitor C)_inThe detecting electrode 131 and the programmable filter 151) to output the reference signal S_refAs the detection signal S_o1The erase value of (2) is shown in FIG. 4A. By deriving from said detection signal S_o1Subtracting the elimination value to reduce the DC signal level, the detection capacitor C can be reduced_inThe value of (c). For example, the detection capacitor C_inIs preferably smaller than the self-inductance capacitance C_s10% of the capacitance value of (c). Therefore, the overall size of the control wafer 100 can be effectively reduced.

In order to contact the differential detection signal S_{Contact with}And the untouched differential detection signal S_{Is not in contact with}The difference between the signals is more obvious, and in some embodiments, the gain circuit 153 may be used to amplify the differential detection signal S_diff(ii) a The gain value (gain) of the gain circuit 153 may be determined according to an analysis range of an analog-to-digital conversion unit (ADC) in the digital back end 16, and is not particularly limited. As shown in fig. 2, the contact differential detection signal S is included in the output signal (i.e., the amplified differential detection signal) of the gain circuit 153_{Contact with}And the untouched differential detection signal S_{Is not in contact with}The difference therebetween is increased, and thus whether a contact event occurs can be more easily recognized. The anti-noise filter 154 is then used to filter the amplified differential detection signal, as described above154 is for example a low pass filter.

Fig. 3 is a schematic diagram illustrating another block diagram of a capacitive touch device according to an embodiment of the present invention; FIG. 3 also shows an implementation of the simulation circuit 150 and the programmable filter 151.

In some embodiments, the programmable filter 151 includes an input resistor R_inAnd an amplifying circuit 15A; wherein the detection capacitor C_inThe self-inductance capacitor C_sThe input resistor R_inAnd the amplifying circuit 15A forms a first filter circuit and the emulating circuit 150 forms a second filter circuit. As mentioned above, the subtracting circuit 152 is used to output the detection signal S from the first filtering circuit_o1And a reference signal S output by the second filter circuit_refPerforming a differential operation to output a differential detection signal S_diffReferring to FIGS. 4A-4B; wherein, FIG. 4B is the detection signal S of FIG. 4A_o1And a reference signal S_refIs detected as a differential detection signal S_diffThe waveform of (2).

In one embodiment, the amplifier circuit 15A is an Integral Programmable Gain Amplifier (IPGA). For example, 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 bridged between the negative input end and the output end of the operational amplifier OP, and the input resistor R_inA second terminal (i.e. a signal output terminal) of the detecting electrode 131 is coupled to the negative input terminal of the operational amplifier OP, and a first terminal (i.e. a signal input terminal) of the detecting electrode 131 is coupled to the detecting capacitor C_in. In this embodiment, the frequency response of the first filter circuit can be expressed by equation (1) and Bode plot (Bode diagram) of fig. 6, and the first filter circuit has two poles (pole) and zero (zero) 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 described above, since the output of the simulation circuit 150 is the output of the simulation circuitThe cancellation value of the first filter circuit, the frequency response of the emulation circuit 150 is preferably similar to the first filter circuit, i.e., the frequency response of the emulation circuit 150 is determined according to the frequency response of the first filter circuit. In some embodiments, the two frequency responses are similar, including, but not limited to, two poles of the simulation circuit 150 being close to two poles of the first filter circuit. For example, two poles of the simulation circuit 150 can be determined according to two poles of the first filter circuit, and only the pole frequency needs to be considered since the zero has no effect. For example, the frequency difference between the pole frequency (pole frequency) of two poles of the simulation circuit 150 and the corresponding pole of the second filter circuit is designed to be lower than 35%, preferably lower than 20%, of the pole frequency. Although theoretically, the two poles of the simulation circuit 150 are as close as possible to the two poles of the first filter circuit, in practice, the self-inductance capacitance C of each detection electrode 131 is considered to be the same_sIt is not easily known in advance with precision, and therefore the simulation circuit 150 is designed in an estimated manner.

In one embodiment, the simulation circuit 150 includes an analog detection capacitor C_{ref_in}Analog self-inductance capacitor C_{ref_s}Analog input resistor R_{ref_in}And an analog amplifier circuit 15B, and the analog detection capacitor C_{ref_in}The analog self-inductance capacitor C_{ref_s}The analog input resistor R_{ref_in}The connection mode with the analog amplifying circuit 15B is the same as that of the detection capacitor C_inThe self-inductance capacitor C_sThe input resistor R_inConnected to the amplifier circuit 15A in such a way as to obtain a similar frequency response. That is, the analog self-inductance capacitance C_{ref_s}Self-inductance capacitance C for simulating detection electrode 131_sThe analog detection capacitor C_{ref_in}Corresponding analog detection capacitor C_inThe analog input resistor R_{ref_in}Corresponding input resistance R_inThe analog amplifier circuit 15B corresponds to the amplifier circuit 15A. It has to be noted that the circuit parameters (pole RC values) of the simulation circuit 150 may not be exactly the same as the circuit parameters of the first filter circuit, as long as the simulation circuitThe circuit 150 has a similar frequency response to the first filter circuit and is capable of reducing the detection capacitance C_sThat is, there is no particular limitation.

The analog amplifying circuit 15B also includes an operational amplifier OP', an analog feedback resistor R_{ref_f}And an analog compensation capacitor C_{ref_f}(ii) a The connection of the elements in the analog amplifier circuit 15B is the same as that of the amplifier circuit 15A. Therefore, the second filter circuit formed by the simulation circuit 150 also has a frequency response similar to that of equation (1) and fig. 6, except that all the device parameters in the simulation circuit 150 are designed in advance. Therefore, the positions of the two extreme values can be adjusted by changing the parameters of the elements in the simulation circuit 150, i.e., the resistance and the capacitance.

Referring to fig. 5, a flowchart illustrating an operating method of a capacitive touch device according to an embodiment of the invention includes a self-capacitance detection mode (step S)₅₁) And mutual capacitance detection mode (step S)₅₂). In this embodiment, the self-capacitance detection mode and the mutual capacitance detection mode operate in a time-sharing manner, for example, the self-capacitance detection mode is used to determine an approaching object and/or a to-be-detected area (WOI), and then the mutual capacitance detection mode is used to determine a touch position and/or a gesture.

In the self-capacitance detection mode, the driving circuit 11 passes through the detection capacitor C_inAre respectively electrically coupled to the first ends of the driving electrodes 131, and the subtracting circuit 152 is sequentially electrically coupled to the second ends of the driving electrodes 131. Meanwhile, the subtraction circuit 152 receives the reference signal S output by the simulation circuit 150_refThe subtracting circuit 152 is electrically coupled to the second end of the driving electrode 131 through the programmable filter 151, so that the subtracting circuit 152 can output the detecting signal S outputted by the programmable filter 151_o1And the reference signal S output by the simulation circuit 150_refPerforming a differential operation to output a differential detection signal S_diffAs shown in fig. 4A and 4B. Then, the gain circuit 153 can be used to amplify the differential detection signal S_diffSo as to contact the differential detection signal S_{Contact with}And the untouched differential detection signal S_{Is not in contact with}The difference between them is more pronounced as shown in fig. 2. In addition, in one embodiment, only the detection signals output by the plurality of driving electrodes or the plurality of receiving electrodes are detected to determine whether a contact event occurs, so that the operation can be performed in a shorter scanning period.

In another embodiment, the detection signals output by the plurality of driving electrodes and the plurality of receiving electrodes can be detected to substantially identify a desired detection area (WOI) in a mutual capacitance detection mode. Therefore, in the self-capacitance detection mode, the driving circuit 11 is also driven by the detection capacitor C_inAre respectively electrically coupled to a first terminal (i.e., a signal input terminal) of the receiving electrode 131, and the subtracting circuit 152 is sequentially electrically coupled to a second terminal (i.e., a signal output terminal) of the receiving electrode 131. The range to be detected can be determined by judging the driving electrode and the receiving electrode which sense the approaching object. As described above, in the present specification, the driving electrode and the receiving electrode belong to the detecting electrode 131 for generating the mutual inductance capacitance C therebetween_m。

In the mutual capacitance detection mode, the driving circuit 11 does not pass through the detection capacitor C_inAre electrically coupled to the first ends of the driving electrodes 131, respectively; for example, in FIGS. 2-3, the drive circuit 11 utilizes a switch SW₁Bypass (bypass) the detection capacitor C_inTo directly drive the signal S_dTo the detection electrode 131. Furthermore, the anti-noise filter 154 is not electrically coupled to the second end of the driving electrode 131 through the subtraction circuit 152 in turn, for example, as in fig. 2-3, the anti-noise filter 154 utilizes another switch SW₂The subtracting circuit 152 (and the gain circuit 153) are bypassed so that the detecting signal S outputted from the programmable filter 151_o1Directly to the anti-noise filter 154. The filter parameters of the anti-noise filter 154 may be determined according to the actual application, and are not particularly limited.

In the self-capacitance detection mode, the signal transmitted to the detection line does not pass through the resistance and the capacitance of the panel, so the reference line (C) is usedI.e., an emulation circuit) and the detection line, so that the reference signal S is not significant_refCan be used as a cancellation value in subtracting the detected signal.

It should be noted that although the contactless differential detection signal S is shown in fig. 2_{Is not in contact with}Is greater than the contact differential detection signal S_{Contact with}The amplitude (or peak to peak) of the signal is merely illustrative and not limiting. The contact differential detection signal S is set according to the parameter (i.e., RC value) of the simulation circuit 150_{Contact with}May be larger than the untouched differential detection signal S_{Is not in contact with}。

It should be noted that although the detection signal S is shown in FIG. 4A_o1Is greater than the reference signal S_refThe amplitude (or peak to peak) of the signal is merely illustrative and not limiting. According to the parameter setting (i.e. RC value) of the simulation circuit 150, the reference signal S_refMay also be larger than the detection signal S_o1The amplitude of (d).

In other embodiments, the circuit parameters of the simulation circuit 150 are changed to wake up the sleep mode of the capacitive touch device 1. In this sleep mode, most of the touch detection is performed by the analog front end 15, which reduces the amount of complex post-processing operations of the digital back end 16 and thus reduces overall power consumption.

Fig. 7 is a block diagram of a capacitive touch device 1 according to another embodiment of the invention. The analog front end 15 of the present embodiment further includes a mechanism for waking up the capacitive touch device 1 operating in the sleep mode. In other words, the capacitive touch device 1 of fig. 7 can be combined with fig. 3, for example, the analog front end 15 further includes a multiplexer or a switch (for example, switched between the subtraction circuit 152 and the gain circuit 153 and the detection circuit 155) to switch to the circuit connection of fig. 7 in a sleep mode and to switch to the circuit connection of fig. 3 in a normal mode (non-sleep mode), for example, a mode for calculating touch positions and/or gestures, and the sleep mode for example, a mode for not calculating touch positions and gestures. Thus, after detecting a touch event using FIG. 7, the operations of FIGS. 2-3 and 5 can be performed.

As described above, the capacitive touch device 1 includes the touch panel 13, the driving terminal and the detecting terminal. The detection end includes an analog front end 15 and a digital back end 16. A driving circuit 11 and a plurality of switches SW included in the driving end₁And a detection capacitor C_inThe contents of the detecting electrodes 131 included in the touch panel 13 and the digital back end 16 have been described in the previous embodiments. For example, the touch panel 13 can be operated in a self-capacitance detection mode or a mutual-capacitance detection mode. The detection capacitor C_inA switch SW for coupling to the signal input terminal of the detecting electrode 131 in the self-capacitance detection mode and for being switched from the signal input terminal of the detecting electrode 131 in the mutual-capacitance detection mode₁Bypassing the detection electrode 131 without being connected thereto.

The analog front end 15 comprises a plurality of input resistors R_inA plurality of amplification circuits 15A (see fig. 3), a simulation circuit 150', a subtraction circuit 152, a detection circuit 155, and a phase reference circuit 156; wherein the detection circuit 155 is a phase detection circuit. As mentioned above, the driving terminal and the detecting terminal are disposed in the control chip 100.

As mentioned above, the plurality of input resistors R_inRespectively coupled to the signal output terminals of the detecting electrodes 131. The plurality of amplifying circuits 15A pass through the plurality of input resistors R_inCoupled to the detection electrode 131 and configured to output a detection signal S_o1. When the conductor contacts or approaches the touch panel 13, the detection signal S is generated_o1A change occurs. For example, fig. 7 shows that when the detecting electrode 131 is not in inductive contact, the amplifying circuit 15A outputs the first detecting signal S_o11(ii) a When the detecting electrode 131 is touched, the amplifying circuit 15A outputs the second detecting signal S_o12. In the description of the present invention, the signal S is detected unless otherwise specified_o1May be the first detection signal S_o11And a second detection signal S_o12One of them. As mentioned before, the first detection signal S depends on the application_o11And a second detection signal S_o12The size values of (a) may be interchanged.

This embodiment and the previous oneOne difference of the embodiments is the reference signal S output by the simulation circuit 150' of FIG. 7_ref' reference signal S output by simulation circuit 150 different from FIG. 2_ref. In the former embodiment, the reference signal S output by the simulation circuit 150_refTo approximate the detection signal S as closely as possible_o1(ii) a In this embodiment, the reference signal S outputted by the simulation circuit 150_ref' is interposed between the first detection signal S_o11And the second detection signal S_o12As shown in fig. 7.

The subtracting circuit 152 is also used to calculate the detection signal S_o1(may be the first detection signal S_o11Or the second detection signal S_o12Determined by whether there is a conductor approaching the touch panel 13) and the reference signal S_ref' to output a differential detection signal S_diff。

For example, the subtraction circuit 152 is directed to the reference signal S_ref' with said first detection signal S_o11Performing a differential operation to generate a first differential detection signal S_diff1＝S_o11-S_ref' (as shown in FIG. 7) and with respect to the reference signal S_ref' with said second detection signal S_o12Performing a differential operation to generate a second differential detection signal S_diff2＝S_o12-S_ref' (as shown in FIG. 7). According to a reference signal S_ref' the first differential detection signal S_diff1And the second differential detection signal S_diff2With a phase difference of 180 degrees or referred to as reverse. The present embodiment uses the phase difference to identify whether a touch event occurs on the touch panel 13.

In one embodiment, the simulation circuit 150' of FIG. 8A is similar to that of FIG. 3, and includes an analog detection capacitor C_{ref_in}Analog self-inductance capacitor C_{ref_s}Analog input resistor R_{ref_in}And an analog amplifier circuit 15B. In addition, the simulation circuit 150' of the present embodiment further includes an analog mutual inductance capacitor C_{ref_m}The analog mutual inductance capacitor C_{ref_m}For simulating mutual inductance capacitance C between the detection electrodes 131 of the touch panel 13_m。

In addition, such asAs shown in FIG. 8A, the simulation circuit 150' of the present embodiment further includes a switch SW_{ref_1}、SW_{ref_2}And SW_{ref_3}To cooperate with the touch panel 13 to operate in a self-capacitance detection mode or a mutual-capacitance detection mode.

In the self-contained test mode, the switch SW is switched_{ref_2}Bypass analog mutual inductance capacitor C_{ref_m}And a change-over switch SW_{ref_1}And SW_{ref_3}Conducted to connect with the analog detection capacitor C_{ref_in}And an analog self-inductance capacitor C_{ref_s}To form the simulation circuit 150 of fig. 3. That is, the simulation circuit 150' detects the capacitance C according to the simulation in the self-capacitance detection mode_{ref_in}The analog self-inductance capacitor C_{ref_s}The analog input resistor R_{ref_in}And the analog amplifying circuit 15B outputs a first reference signal (or a self-contained reference signal).

However, in order to make the waveform of the first reference signal intervene in the first detection signal S_o11(also detected in the self-contained detection mode) and the second detection signal S_o12(also detected in the self-capacitance detection mode), the analog self-inductance capacitance C_{ref_s}Can be based on the detection signal S caused by contact_o1Is selected. In one embodiment, the analog self-inductance capacitor C_{ref_s}A self-inductance capacitance C selected as the detection electrode 131 of the touch panel 13_S0.92 to 0.98 times, since the detection signal S caused by contact in general_o1The amount of change in (c) is about 10%. It can be understood that the detection signal S is caused when the touch is made_o1The range of multiples may be adjusted when the amount of change in (c) is different.

The subtraction circuit 152 is for the detection signal S in the self-capacitance detection mode_o1Performs a differential operation with the first reference signal to generate a differential detection signal S_diff。

In the mutual capacitance detection mode, the switch SW is switched_{ref_1}And SW_{ref_3}Separately bypassing analog detection capacitor C_{ref_in}And an analog self-inductance capacitor C_{ref_s}And a change-over switch SW_{ref_2}Conducted to connect with analog mutual inductance capacitor C_{ref_m}That is, as shown in FIG. 8AThe connections shown are. That is, the simulation circuit 150' in the mutual capacitance detection mode is based on the simulated mutual inductance capacitance C_{ref_m}The analog input resistor R_{ref_in}And the analog amplifying circuit 15B outputs a second reference signal (or a mutual capacitance reference signal). In this embodiment, the first reference signal may be different from the second reference signal due to different circuit components for generating the first reference signal and the second reference signal.

Similarly, in order to interpose the waveform of the second reference signal between the first detection signal S_o11(also generated in the mutual capacitance detection mode) and said second detection signal S_o12(also generated in mutual capacitance detection mode), the analog mutual capacitance C_{ref_m}Selected as the mutual inductance capacitance C of the detection electrode 131 of the touch panel 13_m0.92 to 0.98 times; the setting of the multiple is described above.

The subtraction circuit 152 is for the detection signal S in the mutual capacitance detection mode_o1Is differentially operated with a second reference signal to generate a differential detection signal S_diff。

It should be understood that although FIG. 8A shows the emulation circuit 150' including three switches SW_{ref_1}、SW_{ref_2}、SW_{ref_3}And analog detection capacitor C_{ref_in}Analog self-inductance capacitor C_{ref_s}Analog mutual inductance capacitor C_{ref_m}To cooperate with the two modes of operation, which are merely illustrative and not restrictive. In some embodiments, the capacitive touch device 1 can perform contact detection in one of the self-capacitance detection mode and the mutual capacitance detection mode to end the sleep mode, and does not need to adopt the two modes at the same time.

For example, when the capacitive touch device 1 only uses the mutual capacitance detection mode for touch detection, the simulation circuit 150' of fig. 8A may not include the switch SW_{ref_1}、SW_{ref_2}、SW_{ref_3}And an analog detection capacitor C_{ref_in}Analog self-inductance capacitor C_{ref_s}. For example, when the capacitive touch device 1 only uses the self-capacitance detection mode for touch detection, the simulation circuit 150' of fig. 8A may not include the switch SW_{ref_1}、SW_{ref_2}、SW_{ref_3}And simulating mutual inductance capacitance C_{ref_m}。

In another embodiment, the emulation circuit 150' may not be implemented as the circuit of FIG. 8A, but includes the flash memory 81 of FIG. 8B and a digital-to-analog converter (DAC)83, and the DAC 83 generates the reference signal S according to at least one digital data stored in the flash memory 81_ref'. The flash memory 81 stores digital data, and therefore the flash memory 81 is included in the digital back end 16, for example.

As described above, the capacitive touch device 1 can perform contact detection in the sleep mode by using at least one of the self-capacitance detection mode and the mutual capacitance detection mode. Therefore, it is preferable that at least one of the first digital data used in the self-capacitance detection mode and the second digital data used in the mutual-capacitance detection mode is stored in the flash memory 81.

The first digital data is a first detection signal S output by the amplifying circuit 15A when the simulation touch panel 13 is touched in the self-capacitance detection mode in advance_o11And a second detection signal S outputted from the amplifier circuit 15A when not touched_o12The data is obtained and stored in the flash memory 81. The touch simulation method is, for example, a built-in self test (BIST) circuit built in parallel with the detection electrode 131 of the touch panel 13, such as an equivalent capacitance circuit simulating a human body or a finger. Contact is indicated when the BIST circuit is connected (e.g., turned on by a switch) to the detection electrode 131 and no contact is indicated when the BIST circuit is not connected (e.g., turned off by a switch) to the detection electrode 131, thereby simulating a contact operation.

The first digital data is a waveform of the first reference signal (similar to S of fig. 7)_ref') between the first detection signals S_o11And the second detection signal S_o12Between the waveforms of (a). The first digital data is generated by, for example, operating the touch panel 13 in a self-contained detection mode and sequentially connecting or disconnecting the built-in self-test circuit to obtain two sets of data (e.g., S shown in fig. 7 for sampling)_o11、S_o12Data obtained from the waveform) and then based onThe two sets of data are used to calculate the first digital data, for example, but not limited to, averaging the data of the corresponding sampling points of the two sets of data.

Similarly, the second digital data is a third detection signal (similar to S) output by the amplifying circuit 15A in advance according to simulation when the touch panel 13 is touched in the mutual capacitance detection mode_o11) And a fourth detection signal (like S) outputted from the amplification circuit 15A when not touched_o12) The data is obtained and stored in the flash memory 81. The second digital data is a waveform of the second reference signal (similar to S of fig. 7)_ref') between waveforms of the third and fourth detection signals; the second digital data is generated in a manner similar to the first digital data, and only the operation mode of the capacitive touch device 1 is different.

At the time of contact detection, the digital-analog converter 83 outputs a first reference signal according to the first digital data in the self-capacitance detection mode or outputs a second reference signal according to the second digital data in the mutual capacitance detection mode. It can be understood that when the detection signal S is sampled_o11、S_o12The reference signal can be restored from the digital data when the sampling frequency of (2) times the Nyquist frequency is exceeded. As mentioned above, in some embodiments, the flash memory 81 may store only one of the first digital data and the second digital data, so the digital-to-analog converter 83 may generate only one of the first reference signal and the second reference signal.

The subtracting circuit 152 operates as described above for the detection signal S in the self-capacitance detection mode_o1Performing a differential operation with the first reference signal or for the detection signal S in the mutual capacitance detection mode_o1Performing a differential operation with the second reference signal to generate a differential detection signal S_diff。

The capacitive touch device 1 further comprises a phase reference circuit 156 for generating a phase reference signal S_prefAnd includes a detection circuit 155 for comparing the differential detection signal S_diffAnd a phase reference signal S_prefTo determine whether the capacitive touch device 1 is touched. The detection circuit 155 is electrically connected to the subtraction circuit 152 and the phase reference circuit 156. In one embodiment, the detection circuit 155 may be implemented by a differential operational amplifier (differential amplifier), for example.

As shown in fig. 7, the subtracting circuit 152 outputs the first differential detection signal S when no touch is detected_diff1The subtraction circuit 152 outputs a second differential detection signal S when a touch occurs_diff2. The detection circuit 155 compares the first differential detection signal S_diff1And/or said second differential detection signal S_diff2And the phase reference signal S_prefTo output a contact signal St or a non-contact signal Snt.

For example, assume the phase reference signal S_prefSelected to differentially detect signals (i.e., S) from no contact_diff1) Having the same phase. When the detection circuit 155 judges the differential detection signal S_diffAnd a phase reference signal S_prefWhen the touch panel is substantially in phase, it is determined that no touch event has occurred and an untouched signal Snt indicating that the touch panel 13 is untouched is generated to the digital back end 16. The digital back end 16 maintains the capacitive touch device 1 in a sleep or low power mode. When the detection circuit 155 judges the differential detection signal S_diffAnd a phase reference signal S_prefWith an inverted phase (180 degrees out of phase), it can be determined that a touch event has occurred and generate a touch signal St to the digital back end 16 indicating that the touch panel 13 is touched, and the digital back end 16 wakes up the capacitive touch device 1. The capacitive touch device 1 is woken up and operates as in the previous embodiment, as shown in fig. 2 to 3 and 5.

In another embodiment, the detection circuit 155 generates the control signal St to the digital back end 16 only when it is determined that the touch event occurs to wake up the capacitive touch device 1, otherwise does not generate the control signal.

The phase reference circuit 156 can be made in a suitable manner without limitation, as long as it can generate the phase reference signal S_prefThe detection circuit 155 may be used as a phase reference. Phase reference signal S_prefCan be selected as_diff1、S_diff2Or a combination thereof, as long as the detection circuit 155 is able to recognize.

In one embodiment, the touch panel 13 may include at least one null line (null line) to generate the false signal S_{o1_dummy}The empty line is arranged not to be contacted to make the capacitance value (C)_S、C_m) Is modified, for example, by providing a shielding layer thereon. In other words, the glitch S_{o1_dummy}Always representing a non-contact detection signal. The phase reference circuit 156 includes the at least one empty line, the emulation circuit 150', and the subtraction circuit 152. More specifically, the phase reference circuit 156 may be disposed apart from and identical to the circuit for generating the phase reference signal S for the capacitive touch device 1 to actually detect the touch_prefThe circuit of (1).

For example, FIG. 9A shows a circuit diagram of phase reference circuit 156 in a relatively mutual capacitance detection mode, which includes drive circuit 11, and mutual capacitance C formed by empty lines (i.e., empty detection electrodes 131)_mInput resistance R_in An amplifying circuit 15A, a simulation circuit 150' and a subtracting circuit 152. The emulation circuit 150' includes at least the components of the relatively mutually compatible detection mode of fig. 8A (as mentioned above, all the components of fig. 8A may be included and the connection may be changed by switching a switch). The subtracting circuit 152 outputs S of fig. 7_diff1Of the phase reference signal S_prefThis is used as a reference for judging contact or non-contact.

For example, FIG. 9B shows a circuit diagram of the phase reference circuit 156 in the self-capacitance detection mode, which includes the driving circuit 11 and the detection capacitor C_inA self-inductance capacitance C formed by the empty line (i.e. the empty detection electrode 131)_SInput resistance R_in An amplifying circuit 15A, a simulation circuit 150' and a subtracting circuit 152. The emulation circuit 150' includes at least the components of the relatively self-contained detection mode of fig. 8A (similarly, all the components of fig. 8A may be included and the connection may be changed by switching a switch). The subtracting circuit 152 outputs S of fig. 7_diff1Of the phase reference signal S_prefThis is used as a reference for judging contact or non-contact.

In another embodiment, as shown in FIG. 9C, the phase reference circuit 156 includesIncludes a phase lock loop (157), the phase lock loop (157) is used to lock the reference signal S outputted by the simulation circuit 150_refThe phase of. As mentioned above, since the emulation circuit 150' is disposed in the control chip 100 without being affected by an external conductor, the reference signal S_refThe phase of' is in phase with the untouched differential detection signal.

Similarly, the connected capacitances of the simulation circuit 150' are different according to different operation modes, so that different reference signals S are output_ref'. It is assumed that the simulation circuit 150' outputs a first reference signal in the self-capacitance detection mode and a second reference signal in the mutual-capacitance detection mode, and thus the phase-locked loop 157 locks the phase of the first reference signal in the self-capacitance detection mode and the phase of the second reference signal in the mutual-capacitance detection mode.

In another embodiment, as shown in fig. 9D, the phase reference circuit 156 includes a phase locking loop 157, and the phase locking loop 157 is used to lock the phase of the driving signal Sd output by the driving circuit 11 at the driving end. Although the drive signal Sd is also unaffected by the external conductor, the differential detection signal S being compared_diffThe differential detection signal S is generated because the phase shift is still derived from the signal passing through the touch panel 13_diffThe phase of the driving signal Sd is not exactly in phase or in anti-phase. In this embodiment, the detection circuit 155 can detect the differential detection signal S_diffWhether the phase difference from the phase of the driving signal Sd is within a preset range. For example, non-contact is determined when the phase difference is between 0 and 45 degrees and non-contact is determined when the phase difference is between 135 and 180 degrees. It is understood that the range of the phase difference is not limited thereto, and may be measured and set in advance before factory shipment, and is not particularly limited.

In some embodiments, the capacitive touch device 1 described in the present invention can be used as a trigger button (touch button) for simply detecting whether a touch event occurs, without calculating a touch position, for example, without including the components in fig. 3 that are not included in fig. 7.

The change-over switch of the illustrative embodiment of the invention is, for example, a semiconductor switch.

In summary, how to reduce the overall power consumption of the capacitive touch device is an important issue. Therefore, the present invention provides a capacitive touch device (fig. 7), in which an emulation circuit is disposed in a control chip to generate a reference signal, a phase difference between a contact differential signal and a non-contact differential signal, which is obtained by subtracting the reference signal from a detection signal of a touch panel, is 180 degrees, and a contact event can be determined according to the phase difference. Meanwhile, the judgment of the contact event can be completed by the analog front end, so that the electric energy consumed by the digital back end can be reduced.

Although the present invention has been disclosed by way of examples, it is not intended to be limited thereto, and various changes and modifications can be made by one of ordinary skill in the art without departing from the spirit and scope of the invention. Therefore, the protection scope of the present invention is subject to the scope defined by the appended claims.

Claims

1. A capacitive touch device, comprising:

a touch panel including a detection electrode;

the amplifying circuit is coupled with the detection electrode and used for outputting a first detection signal when the detection electrode is not in inductive contact and outputting a second detection signal when the detection electrode is in inductive contact;

the simulation circuit is used for outputting a reference signal, and comprises a selector switch, a simulation detection capacitor, a simulation self-inductance capacitor, a simulation input resistor and a simulation amplifying circuit, wherein the selector switch is connected with or not connected with the simulation self-inductance capacitor and the simulation input resistor in a self-capacitance detection mode and a mutual-capacitance detection mode; and

a subtraction circuit for performing a differential operation on the reference signal and the first detection signal to generate a first differential detection signal, and performing a differential operation on the reference signal and the second detection signal to generate a second differential detection signal, wherein the first differential detection signal is in anti-phase with the second differential detection signal.

2. The capacitive touch device according to claim 1, wherein a waveform of the reference signal is between waveforms of the first detection signal and the second detection signal.

3. The capacitive touch device of claim 1, wherein the analog self-inductance capacitance is 0.92-0.98 times the self-inductance capacitance of the detection electrode of the touch panel.

4. The capacitive touch device of claim 1, wherein the emulation circuit further comprises an analog mutual inductance capacitance that is 0.92-0.98 times a mutual inductance capacitance of the detection electrodes of the touch panel.

5. The capacitive touch device of claim 1, further comprising

A phase reference circuit for generating a phase reference signal; and

and the detection circuit is electrically connected with the subtraction circuit and the phase reference circuit and is used for comparing the phases of the first differential detection signal or the second differential detection signal and the phase reference signal so as to output a contact signal or a non-contact signal.

6. The capacitive touch device according to claim 5, wherein the phase reference circuit comprises a phase locked loop for locking the phase of the reference signal output by the emulation circuit.

7. The capacitive touch device according to claim 5, wherein the phase reference circuit comprises a phase-locked loop for locking the phase of the driving signal output by the driving circuit.

8. A capacitive touch device, comprising:

the touch panel comprises a detection electrode and a control electrode, wherein the detection electrode is used for operating in a self-capacitance detection mode or a mutual capacitance detection mode;

a detection capacitor for coupling to a signal input of the detection electrode in the self-capacitance detection mode and not coupling to the signal input of the detection electrode in the mutual capacitance detection mode;

an input resistor coupled to a signal output terminal of the detection electrode;

the amplifying circuit is coupled with the input resistor and is used for outputting a detection signal;

the simulation circuit comprises a simulation detection capacitor, a simulation self-inductance capacitor, a simulation mutual inductance capacitor, a simulation input resistor and a simulation amplification circuit, and is used for outputting a first reference signal according to the simulation detection capacitor, the simulation self-inductance capacitor, the simulation input resistor and the simulation amplification circuit in the self-capacitance detection mode or outputting a second reference signal according to the simulation mutual inductance capacitor, the simulation input resistor and the simulation amplification circuit in the mutual-capacitance detection mode; and

a subtraction circuit for differentiating the detection signal with the first reference signal in the self-capacitance detection mode or differentiating the detection signal with the second reference signal in the mutual-capacitance detection mode to generate a differential detection signal.

9. The capacitive touch device according to claim 8, wherein the analog self-inductance capacitance is 0.92 to 0.98 times the self-inductance capacitance of the detection electrode of the touch panel.

10. The capacitive touch device of claim 8, wherein the analog mutual inductance capacitance is 0.92-0.98 times the mutual inductance capacitance of the detection electrodes of the touch panel.

11. The capacitive touch device of claim 8, wherein the emulation circuit further comprises a switch for connecting or bypassing the analog detection capacitor, the analog self-inductance capacitor, and the analog mutual-inductance capacitor.

12. The capacitive touch device of claim 8, further comprising

A phase reference circuit for generating a phase reference signal; and

a detection circuit for comparing phases of the differential detection signal and the phase reference signal to output a contact signal indicating that the touch panel is contacted or a non-contact signal indicating that the touch panel is not contacted.

13. The capacitive touch device of claim 12, wherein the phase reference circuit comprises a phase-locked loop for locking a phase of the first reference signal output by the emulation circuit in the self-capacitance detection mode or locking a phase of the second reference signal output by the emulation circuit in the mutual-capacitance detection mode.

14. The capacitive touch device according to claim 12, wherein the phase reference circuit comprises a phase-locked loop for locking a phase of the driving signal output by the driving circuit.

15. A capacitive touch device, comprising:

a touch panel including a detection electrode;

a flash memory, wherein at least one digital data is stored in the flash memory in advance;

a digital-to-analog converter for outputting at least one reference signal in accordance with the at least one digital data; and

a subtraction circuit for performing a differential operation on the detection signal and the at least one reference signal to generate a differential detection signal, wherein,

the at least one digital data includes first digital data and second digital data,

the digital-to-analog converter is used for outputting a first reference signal according to the first digital data in a self-capacitance detection mode and outputting a second reference signal according to the second digital data in a mutual-capacitance detection mode,

the first digital data is obtained in advance according to a first detection signal output by the amplifying circuit when the touch panel is simulated to be contacted in the self-capacitance detection mode and a second detection signal output by the amplifying circuit when the touch panel is not contacted and is stored in the flash memory,

the first digital data is such that the waveform of the first reference signal is interposed between the waveforms of the first detection signal and the second detection signal,

the second digital data is obtained in advance according to a third detection signal output by the amplifying circuit when the touch panel is simulated to be contacted in the mutual capacitance detection mode and a fourth detection signal output by the amplifying circuit when the touch panel is not contacted, and is stored in the flash memory, and

the second digital data is such that the waveform of the second reference signal is interposed between the waveforms of the third detection signal and the fourth detection signal.

16. The capacitive touch device of claim 15, further comprising

A phase reference circuit for generating a phase reference signal; and

17. The capacitive touch device according to claim 16, wherein the phase reference circuit comprises a phase-locked loop for locking a phase of the first reference signal output by the digital-to-analog converter in the self-capacitance detection mode and locking a phase of the second reference signal output by the digital-to-analog converter in the mutual-capacitance detection mode.

18. The capacitive touch device according to claim 16, wherein the phase reference circuit comprises a phase-locked loop for locking a phase of the driving signal output by the driving circuit.