CN101957697A - Mutual capacitance touch screen and driving method thereof - Google Patents

Abstract

The invention discloses a mutual capacitance touch screen and a driving method thereof. Compared with the prior art, the mutual capacitance touch screen adds a driving signal unit, which provides a driving signal to the driving line, and in the rising stage of the waveform of the driving signal, sends The driving line provides a first forward constant current; during the falling phase of the waveform of the driving signal, a first reverse constant current is supplied to the driving line. The invention effectively reduces the waveform deformation caused by RC delay, and even if the parasitic capacitance is large, the detection signal is relatively large and can be detected more easily, thereby improving the sensitivity of the touch screen.

Description

Mutual capacitance touch screen and driving method thereof

technical field

The invention relates to the field of touch screens, in particular to a mutual capacitance touch screen with improved sensitivity and a driving method thereof.

Background technique

In the touch screen technology, compared with the resistive touch screen, the capacitive touch screen has the advantages of long life, high light transmittance, and can support multi-point touch. The mutual capacitance sensing touch screen is an emerging technology in the capacitive touch screen. It can not only realize the real multi-touch, but also has a good suppression effect on noise and ground parasitic capacitance. The direction of the main attack.

As shown in Figures 1 and 2, a traditional mutual capacitance touch screen includes: a lower substrate 9, on which a driving line layer (material is indium tin oxide) 10 is formed, and the driving line layer 10 includes at least one driving Line 2, the driving line 2 is composed of several parallel driving electrodes 2a, 2b...2h, the driving electrode layer 10 has an insulating medium 11, and the other surface of the insulating medium 11 is formed with Induction line layer 12, the induction line layer 12 includes at least one induction line 5, the induction line 5 is composed of a number of induction electrodes 5a, 5b...5i parallel to each other, formed on the induction line layer 12 There is a protective layer 13, the driving electrodes 2a, 2b...2h and the sensing electrodes 5a, 5b...5i are perpendicular to each other, and the traditional mutual capacitance touch screen also includes an AC driving power supply 1 , the AC driving power supply 1 is used to provide signals to the driving lines; as shown in FIG. 2 , each sensing line 5 is connected to a detection unit 16 through a digital switch 17 .

FIG. 3 shows an equivalent circuit of the conventional mutual capacitance touch screen. As shown in FIG. 3, the AC driving power supply 1 is connected to the driving line 2, and the driving line 2 of a certain length is equivalent to a resistance, and the driving electrode and the sensing electrode form a mutual capacitance 4 at the intersection point, When there is a touch, the value of the mutual capacitance 4 will change. In addition, the driving electrode and the sensing electrode also have parasitic capacitance 3 to the ground. Since the sensing signal on the sensing line 5 is relatively small, it is generally An amplifier 6 is connected to one end of each sensing line 5 to amplify the signal, and then the output signal Vout is output through the output terminal 8 .

The detection method of the traditional mutual-capacitance touch screen is: scan each drive line 2 in sequence, that is, apply a drive voltage 14 to each drive line 2 in sequence, and simultaneously ground the rest of the drive lines 15, and each sensing line at the detection end 5 are connected to the detection unit 16 through a digital switch 17, and the digital switch 17 controls each induction line 5 to be connected to the detection unit 16 so as to detect the signal on each induction line 5.

Since the finger is a kind of conductor, when the finger touches the surface of the touch screen, the mutual capacitance 4 at the touch position changes due to the capacitive sensing effect of the finger. This change can be detected by the detection unit 16, so as to determine whether there is a finger touch and where it is touched. When the parasitic capacitance 3 to the ground is relatively large, the change of the mutual capacitance 4 can still have a great influence on the signal at the detection circuit 6, and the change of the detection signal 6 due to the change of the mutual capacitance 4 is not affected by the increase of the parasitic capacitance 3 Impact. Therefore, the principle of mutual capacitance detection has a strong inhibitory effect on the parasitic capacitance to ground. Similarly, this principle also has a good suppression effect on coupled noise.

Although the mutual capacitance touch screen has a strong suppression effect on the parasitic capacitance 3 . But when the parasitic capacitance 3 is very large, the driving signal will be severely deformed. The deformation of the driving pulse will have two adverse effects on the detection signal: first, it will seriously attenuate the detection signal; detection. Figures 4a to 6b illustrate the aforementioned adverse effects caused by the deformation of the drive pulse.

The pulse deformation is mainly caused by the time delay (RC delay) of the resistance and capacitance. In FIGS. 4a and 4b, the drive signal is measured from the drive signal node 18 on the drive line 2. In FIGS. 5a and 5b The sensing signal is measured from the sensing signal node 19 on the sensing line 5 . Since RC (R represents resistance, C represents capacitance) delays are different, when the driving voltage 14 applied by the AC driving power supply 1 is the driving square wave 1a and 1b respectively, the driving signal node 18 of the driving line 2 will be deformed into waveforms 18a and 18 respectively. 18b. When the resistance on the driving line 2 and the sensing line 5 are both 1 kohms, the parasitic capacitance on the driving line 2 is 300pF, the parasitic capacitance on the sensing line 5 is 40pF, and the mutual capacitance is 1.4pF, the driving signal node 18 The waveform of the driving square wave 1a is transformed into a waveform 18a; when the resistance on the driving line 2 is 10 kohms, the resistance on the sensing line 5 is 15 kohms, the parasitic capacitance on the driving line 2 is 900pF, and the resistance on the sensing line 5 is When the parasitic capacitance is 40pF and the mutual capacitance is 1.4pF, the waveform at the driving signal node 18 is transformed from the driving square wave 1b to the waveform 18b. Wherein, in Fig. 4a and Fig. 4b, the period of each waveform is 16 microseconds (μs), and the peak values of the driving square waves 1a, 1b are plus or minus 18 volts (V). The time required for waveforms 18a and 18b to rise to 0.632 times their respective amplitudes is the product of RC. Figure 4a shows the case of small RC delay, while Figure 4b shows the case of large RC delay. From Figure 4a and Figure 4b, it can be seen that when the parasitic capacitance is large, the RC delay is large, and the rising speed of waveforms 18a and 18b is relatively fast. slow. In FIG. 4b, it can be seen that due to the RC delay, the waveform 18b at the driving signal node 18 has not yet risen to the maximum value, but begins to fall because of the falling edge of the driving square wave 1b. Therefore, the waveform 18b on the driving line 2 cannot reach the maximum value, thereby reducing the output signal Vout output from the output terminal 8 . At this time, the peak value of the waveform 18a is still plus or minus 18 volts, while the peak value of the waveform 18b is about 8 volts after stabilization.

Fig. 5a and Fig. 5b show the waveforms 19a and 19b of two situations at the sensing signal node 19 on the sensing line 5, wherein Fig. 5a corresponds to the situation shown in Fig. 4a, and Fig. 5b corresponds to the situation shown in Fig. 4b. The period of each waveform in Fig. 5a and Fig. 5b is also 16 microseconds. The waveforms 18a and 18b of the driving signal on the driving line 2 have passed through the high-pass effect of the mutual capacitance 4, and an induction signal is generated on the induction line 5. The waveforms of the induction signal are waveforms 19a and 19b, and the strength of the waveform of the induction signal In relation to waveforms 18a and 18b on the drive lines, a reduction in waveforms 18a and 18b at drive signal nodes will also result in a reduction in sense signal nodes 19a and 19b. In Figure 5a, waveform 19a shows the case of a small RC delay, while in Figure 5b, waveform 19b shows the case of a large RC delay. The peak value of waveform 19a is approximately plus or minus 350 millivolts (mV), and the peak value of waveform 19b is approximately 50 mV.

FIGS. 6 a and 6 b show waveforms 8 a and 8 b of the output signal Vout output from the output terminal 8 after the waveforms 19 a and 19 b pass through the amplifier 6 . Wherein, Fig. 6a corresponds to the situation shown in Fig. 4a, and Fig. 6b corresponds to the situation shown in Fig. 4b. The period of each waveform in Fig. 6a and Fig. 6b is also 16 microseconds. In fact, this output voltage is actually the integral of the waveforms 19a, 19b of the sense line signal. Therefore, the signal reduction phenomenon due to RC delay is also reflected in the output voltage. In Figure 6a, waveform 8a shows a case with a small RC delay, while in Figure 6b, waveform 8b shows a case with a large RC delay. Waveform 8a has a peak value of 0 to -1 volt, 1 volt peak-to-peak, and waveform 8b has a peak value of about -300 millivolts to -700 millivolts, with a peak-to-peak value of about 400 millivolts. The peak-to-peak value refers to the difference between the maximum positive phase value and the maximum negative phase value of the waveform.

In addition, due to the deformation of each waveform 18b, 19b, the amplitude of the waveform 8b is always changing, so compared with the waveform 8a, the waveform 8b is more difficult to detect, that is, the touch and the position of the touch are more difficult to detect.

Contents of the invention

The purpose of the present invention is to solve the waveform distortion caused by RC delay, especially in the case of large parasitic capacitance, the waveform of the induction signal is small and unstable, so the waveform is not easy to be detected, and the sensitivity of the touch screen is low.

In order to achieve the above object of the present invention, the present invention provides a mutual capacitance touch screen, the mutual capacitance touch screen includes:

Insulation;

a driving line layer located on the first surface of the insulating layer, the driving line layer including at least two driving lines;

an induction line layer located on the second surface of the insulating layer, the induction line layer comprising at least two induction lines;

It is characterized in that it also includes: a drive signal unit, which provides a drive signal to the drive line, and provides a first positive constant current to the drive line during the rising phase of the waveform of the drive signal; In the falling phase of the waveform, a first reverse constant current is supplied to the driving line.

Optionally, the driving signal unit provides the driving signal to the driving line through the first switch unit.

Optionally, the first switch unit is a single-pole multi-throw switch.

Optionally, the driving signal unit further includes a first positive voltage source and a second positive voltage source, or a first negative voltage source and a second negative voltage source.

Optionally, the mutual-capacitance touch screen further includes: a sensing signal unit, which provides a sensing signal to the sensing line, and provides A second positive constant current: during the reverse rising phase of the waveform of the sensing signal, providing a second reverse constant current to the sensing line.

Optionally, the sensing line includes a first sensing signal input end and a second sensing signal input end.

Optionally, the second forward constant current source includes two connection terminals, and when the second forward constant current is supplied to the induction line, the two connection terminals of the second forward constant current source are respectively connected to the The first sensing signal input end and the second sensing signal input end are described above.

Optionally, the second reverse constant current source includes two connection terminals, and when the second reverse constant current is provided to the induction line, the two connection terminals of the second reverse constant current source are respectively connected to the The first sensing signal input end and the second sensing signal input end are described above.

Optionally, the sensing signal unit further includes a third forward constant current source and a third reverse constant current source, which provide a third forward constant current source to the sensing line during the forward falling phase of the waveform of the sensing signal. Constant current: providing a third reverse constant current to the sensing line during the reverse rising phase of the waveform of the sensing signal.

Optionally, the sensing line further includes a third sensing signal input end and a fourth sensing signal input end, the third sensing signal input end is connected to the first sensing signal input end through a switch, and the fourth sensing signal input end is connected to the first sensing signal input end through a switch. The signal input end is connected to the second sensing signal input end through another switch.

Optionally, the second forward constant current is the same as the third forward constant current, and the second reverse constant current is the same as the third reverse constant current.

Optionally, the magnitudes of the second forward constant current and the second reverse constant current are equal.

Optionally, each of the second forward constant current source, the second reverse constant current source, the third forward constant current source and the third reverse constant current source includes a connection terminal, through The switch is connected to the first sensing signal input end or the second sensing signal input end.

The present invention also provides a driving method for a mutual capacitance touch screen, comprising the steps of:

S1: The drive signal unit provides a drive signal to at least one of the drive lines, and in the rising phase of the waveform of the drive signal, the drive line obtains a first positive constant current, and in the falling phase of the waveform of the drive signal stage, the drive line obtains a first reverse constant current;

S2: Receive a sensing signal on the sensing line.

Preferably, the step S1 further includes: providing a sensing signal to the sensing line by the sensing signal unit, and providing a second forward constant current to the sensing line during the positive falling phase of the waveform of the sensing signal, In the reverse rising phase of the waveform of the sensing signal, a second reverse constant current is supplied to the sensing line.

According to the mutual capacitance touch screen and the driving method of the mutual capacitance touch screen of the present invention, the driving signal unit provides the driving signal to the driving line, and in the rising stage of the waveform of the driving signal, the second driving signal is provided to the driving line. A positive constant current; during the falling phase of the waveform of the driving signal, a first reverse constant current is provided to the driving line. Therefore, the waveform deformation caused by RC delay can be reduced, so that even if the parasitic capacitance is large, a larger detection signal can be obtained and the detection signal is more stable so that it is easier to be detected and the sensitivity of the touch screen is improved.

Description of drawings

FIG. 1 shows a schematic cross-sectional structure diagram of a traditional mutual capacitance touch screen.

FIG. 2 shows a schematic diagram of the planar structure and connection method of the driving line layer and the sensing line layer of the traditional mutual capacitance touch screen.

FIG. 3 shows a schematic diagram of an equivalent circuit of a conventional mutual capacitance touch screen.

4a and 4b show waveforms of driving signal nodes in a conventional mutual-capacitance touch screen.

5a and 5b show waveforms of sensing signal nodes in a conventional mutual-capacitance touch screen.

6a and 6b show the waveform of the output signal Vout output from the output terminal in the traditional mutual capacitance touch screen.

Fig. 7a and Fig. 7b further illustrate the signal deformation of the driving line and the sensing line in the traditional mutual capacitance touch screen.

FIG. 8 is a circuit schematic diagram of a preferred embodiment of a mutual capacitance touch screen according to the present invention.

Fig. 9 is a circuit schematic diagram of another preferred embodiment of the mutual capacitance touch screen according to the present invention.

FIG. 10 shows the voltage waveforms of the driving line, the sensing line and the output terminals of the preferred embodiment of the mutual capacitance touch screen of the present invention.

Detailed ways

In order to make the technical content of the present invention and the technical problems and technical effects to be solved clearer and easier to understand, the specific embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, but the present invention is not limited to the accompanying drawings and the described embodiments.

In order to illustrate the working principle of the embodiment of the present invention, the driving line voltage 18 and the sensing line voltage 19 in the traditional mutual capacitance model ( FIG. 3 ) are described once. 7a and 7b are schematic diagrams of the waveforms of the driving line voltage 18 and the sensing line voltage 19 in general. In Fig. 7a and Fig. 7b, the horizontal axis is time, and the vertical axis is voltage. As shown in Figure 3, when the driving power supply 1 inputs a square wave to the driving line 2, the waveform on the driving line 2 is deformed due to RC delay, and the waveform of the driving signal at the driving signal node 18 is shown in Figure 7a, so that the induction The waveform of the induction signal at the signal node 19 becomes as shown in Fig. 7b. The forward phase of the waveform of the induction signal in FIG. 7 b can be divided into two phases: a positive rising phase 20 and a positive falling phase 21 . The positive rising stage 20 is mainly determined by the rising speed of the waveform in FIG. 7 a , while the positive falling stage 21 is mainly determined by the resistance and parasitic capacitance on the sensing line 5 . It can be seen from FIG. 7 b that the signal attenuation on the sensing line 5 is very serious, which is not conducive to the detection of the touch signal. In order to solve the problem of severe attenuation of the signal on the sensing line 5 in the prior art, it is necessary to rapidly increase the voltage on the driving line 2 to the high level of the driving pulse, and in order to solve the problem that the detection signal instability in the prior art causes For problems that are difficult to detect, it is necessary to quickly pull down the signal on the sensing line 5 from a high level to close to zero, so that the integration result (output voltage) can be kept at a potential for a long time. To this end, the mutual capacitance touch screen and the driving method of the mutual capacitance touch screen of the present invention have a driving signal unit to provide the driving signal to the driving line, and provide the first driving signal to the driving line during the rising phase of the waveform of the driving signal. Forward constant current; during the falling phase of the waveform of the driving signal, supplying a first reverse constant current to the driving line. Therefore, the waveform deformation caused by RC delay can be reduced, so that even if the parasitic capacitance is large, a larger detection signal can be obtained and the detection signal is more stable so that it is easier to be detected and the sensitivity of the touch screen is improved.

The mutual capacitance touch screen according to the present invention includes: an insulating layer (not shown); a driving line layer (not shown), located on the first surface of the insulating layer, and the driving line layer includes at least two driving lines; a sensing line layer (not shown), located on the second surface of the insulating layer, the sensing line layer includes at least two sensing lines; and: a driving signal unit that provides a driving signal to the driving line, and the driving signal In a rising phase of the waveform, a first forward constant current is supplied to the driving line; in a falling phase of the waveform of the driving signal, a first reverse constant current is supplied to the driving line. Wherein, the insulating layer, the driving line layer, and the sensing line layer may be the same in position, shape, material, etc. as those of the prior art, or may be the same as other existing mutual-capacitance touch screens.

Providing the first forward constant current and the first reverse constant current in the rising phase and falling phase of the waveform of the driving signal respectively can make the waveform of the driving signal rise rapidly to the high level of the driving pulse, thereby reducing the induction signal Attenuation problem.

Embodiment one

FIG. 8 shows a schematic circuit diagram of a preferred embodiment of a mutual capacitance touch screen according to the present invention. As shown in FIG. 8 , the driving signal unit 20 of this embodiment provides a driving signal to the driving line 2 through the first switch unit 26 , and the sensing line 5 includes a first sensing signal input terminal 501 and a second sensing signal input terminal. 502, and the third induction signal input end 503 and the fourth induction signal input end 504, the induction signal unit 50 sends the induction signal unit 50 to the induction line through the first induction signal input end 501 and the second induction signal input end 502 5 input signals; the drive signal unit 20 includes: a first forward constant current source 22, a first reverse constant current source 23, a first positive voltage source Vd 24, a second positive voltage source 25, wherein the first A positive voltage source Vd24 and the second positive voltage source 25 can be replaced by the first negative voltage source and the second negative voltage source; the induction signal unit 50 includes: the second positive constant current source 29, the second reverse constant current source 30 , a third forward constant current source 30 , and a third reverse constant current source 40 .

The drive line 2 is selectively connected with the first forward constant current source 22, the first reverse constant current source 23, the first positive voltage source Vd 24, and the second positive voltage source 25 through the first switch unit 26; The first sensing signal input end 501 can be selectively connected to the second forward constant current source 29, the second reverse constant current source 30 and the third sensing signal input end 503; the second sensing signal The input terminal 502 can be selectively connected to the third forward constant current source 39 , the third reverse constant current source 40 and the fourth sensing signal input 504 .

In the mutual-capacitance touch screen shown in Fig. 8 and Fig. 9, the parameter values are: one cycle of the driving signal unit 20 is 6 microseconds (μs), the resistance on the driving line 2 is 25 kilohms, and the resistance on the driving line 2 is 6 microseconds (μs). The parasitic capacitance of the sensor is 3000pF, the resistance on the sensing line 5 is 30 kΩ, the parasitic capacitance on the sensing line 5 is 30pF, the mutual capacitance 4 is 0.6pF when not touched, the mutual capacitance 4 is 0.4pF when touched, and the capacitance of the detection amplifier 34 50pF, the amplitude of the first forward constant current and the first reverse constant current is 44 mA, the second forward constant current and the second reverse constant current and the third forward constant current and the third reverse The magnitude of the constant current is 6.1 microamps, the maximum magnitude of the output of the detection signal amplifier is 75 millivolts ((mV)), the first positive voltage is 15 volts (V), and the second positive voltage is 0 volts.

As shown in Figure 10, in one cycle of the driving voltage 14, the waveform 221 at the driving signal node 21 on the driving line 2 can be divided into six periods of 101 to 106, correspondingly, the sensing signal node on the sensing line 5 The waveform at 51 and the output voltage waveform at output terminal 35 are also divided into corresponding six periods:

In period 101, corresponding to the rising stage of the waveform of the drive signal, that is, the positive rising stage of the sensing signal waveform, the first switch unit 26 is connected to the first positive constant current source 22, and the first sensing signal input terminal 501 is connected to the third induction signal input end 503, and the second induction signal input end 502 is connected to the fourth induction signal input end 504, so that the induction line 5 and the detection amplifier 34 are communicated; preferably, the The sense amplifier 34 is a charge amplifier.

In period 102, corresponding to the positive falling phase of the waveform of the sensing signal, the first switch unit 26 is connected to the first positive voltage source Vd 24, and the first sensing signal input terminal 501 is connected to the second positive voltage source Vd 24. A constant current source 29, the second sensing signal input terminal 502 is connected to the third forward constant current source 39;

In period 103, the first switch unit 26 is connected to the first forward constant current source 22, the first sensing signal input terminal 501 is connected to the third sensing signal input terminal 503, and the second sensing signal The input end 502 is connected to the fourth sensing signal input end 504, so that the sensing line 5 communicates with the detection amplifier 34;

In period 104, corresponding to the falling phase of the waveform of the driving signal, that is, the reverse rising phase of the waveform of the sensing signal, the first switching unit 26 is connected to the first reverse constant current source 23, and the first sensing The signal input end 501 is connected to the third sensing signal input end 503, and the second sensing signal input end 502 is connected to the fourth sensing signal input end 504, so that the sensing line 5 communicates with the detection amplifier 34;

In period 105, corresponding to the reverse falling phase of the waveform of the sensing signal, the first switch unit 26 is connected to the second positive voltage source 25, and the first sensing signal input terminal 501 is connected to the second reverse constant A current source 30, the second sensing signal input terminal 502 is connected to the third reverse constant current source 40;

In period 106, the first switch unit 26 is still connected to the first reverse constant current source 23, the first sensing signal input terminal 501 is connected to the third sensing signal input terminal 503, and the second sensing signal input terminal 501 is connected to the third sensing signal input terminal 503. The signal input end 502 is connected to the fourth sensing signal input end 504, so that the sensing line 5 communicates with the detection amplifier 34;

Corresponding to the above six periods, the waveform 551 at the sensing signal node 51 on the sensing line 5 and the output voltage waveform at the output terminal 35 are shown in FIG. 10 .

The above embodiments are preferred embodiments of the present invention. Optionally, in period 102 and period 105, the first positive voltage source may be replaced by the first negative voltage source, and the second positive voltage source may be replaced by the second negative voltage source.

As previously mentioned, the rising phase 20 of the waveform in Figure 7b is mainly determined by the rising speed of the waveform in Figure 7a, that is, the speed of the rising phase of the waveform of the induction signal on the induction line 5 is determined by the rising speed of the waveform of the driving signal on the driving line 2. The speed is determined, so, in period 101 and period 104, the driving line 2 is connected to the first forward constant current source 22 and the first reverse constant current source 23 respectively, which is beneficial to the rise of the waveform of the induction signal on the induction line. In this way, the signal attenuation on the sensing line 5 can be effectively reduced, which is beneficial to the detection of the touch signal.

Preferably, the first forward constant current source 22 provides a first forward constant current, the first reverse constant current source 23 provides a first reverse constant current, and the first forward constant current and the first reverse constant current equal to the magnitude of the constant current. In this way, the rise of the waveform of the drive signal is equal to the decline of the waveform of the drive signal, so that the influence of the drive signal on the induction signal is also symmetrical, that is, the positive rise of the waveform of the induction signal caused by the rise of the waveform of the drive signal and the drive The reverse rise of the waveform of the induction signal caused by the fall of the signal waveform is equivalent.

As mentioned above, the falling phase 21 of the waveform in Fig. 7b is mainly determined by the capacitance and resistance on the sensing line 5, therefore, in the period 102 and the period 105, the driving line 2 is respectively connected to a constant voltage source (the first positive voltage source and the second positive voltage source, or the first negative voltage source and the second negative voltage source), so that the induction line 5 is connected to a constant current source (see period 102 and period 105 for the specific connection), so that the induction line 5 The signal falls rapidly from high to zero. In this way, the voltage of the output terminal 35 can be maintained at a potential for a long time, which is beneficial to the detection of the touch signal.

Preferably, the second forward constant current source 29 is the same 39 as the third forward constant current source, and the second reverse constant current source 30 is the same 40 as the third reverse constant current source, so The second forward constant current provided by the second forward constant current source 29 is equal to the magnitude of the second reverse constant current provided by the second reverse constant current source, and the third forward constant current source 39 The magnitude of the third forward constant current provided is equal to the third reverse constant current provided by the third reverse constant current source 40 . In this way, the waveform 221 at the driving signal node 21 on the driving line 2, the waveform 551 at the sensing signal node 51 on the sensing line 5, and the output voltage waveform at the output terminal 35 have changes and The changes in the latter half-period are symmetrical.

As shown in FIG. 10 , regarding the waveform 221, the horizontal axis is the time in microseconds, the vertical axis is the voltage in volts; regarding the waveform 551, the horizontal axis is the time in microseconds, and the vertical axis is the voltage in microseconds. Volt is the unit; Regarding the output voltage waveform at the output terminal 35, the horizontal axis is the time in microseconds, and the vertical axis is the voltage in microvolts. The periods of the waveforms 221, 551 and the waveform at the output terminal are both 6 microseconds, the peak value of the waveform 221 is 15 volts, the peak value of the waveform 551 is about 100 millivolts, and the peak value of the waveform at the output terminal is about 50 millivolts.

Embodiment two

In period 101, the first switch unit 26 is connected to the first forward constant current source 22, the first sensing signal input terminal 501 is connected to the third sensing signal input terminal 503, and the second sensing signal input terminal 502 is connected to the fourth sensing signal input terminal 504;

In period 102, the first switch unit 26 is connected to the first positive voltage source Vd 24, the first sensing signal input terminal 501 is connected to the third sensing signal input port 503, and the second sensing signal input Terminal 502 is connected to the fourth sensing signal input terminal 504;

In period 103, the first switch unit 26 is connected to the first forward constant current source 22, the first sensing signal input terminal 501 is connected to the third sensing signal input terminal 503, and the second sensing signal The input terminal 502 is connected to the fourth sensing signal input terminal 504;

In period 104, the first switching unit 26 is connected to the first reverse constant current source 23, the first sensing signal input terminal 501 is connected to the third sensing signal input terminal 503, and the second sensing signal The input terminal 502 is connected to the fourth sensing signal input terminal 504;

In period 105, the first switch unit 26 is connected to the second positive voltage source 25, the first sensing signal input terminal 501 is connected to the third sensing signal input terminal 503, and the second sensing signal input terminal 502 is connected to the fourth sensing signal input terminal 504;

In period 106, the first switch unit 26 is still connected to the first reverse constant current source 23, the first sensing signal input terminal 501 is connected to the third sensing signal input terminal 503, and the second sensing signal input terminal 501 is connected to the third sensing signal input terminal 503. The signal input terminal 502 is connected to the fourth sensing signal input terminal 504;

In this embodiment, the sensing signal provided by the sensing signal unit 50 to the sensing line 5 is zero, and the driving signal provided by the driving signal unit 20 to the driving line 2 is the same as that in Embodiment 1, and the functions of each signal It is also the same as the first embodiment.

Embodiment three

In this embodiment, the sensing signal provided by the sensing signal unit 50 to the sensing line 5 is the same as in Embodiment 1, and the driving signal provided by the driving signal unit 20 to the driving line 2 is the same as that of the prior art. The voltage 14 and the functions of each signal are also the same as those in the first embodiment.

Embodiment Four

As shown in FIG. 9 , the difference between this embodiment and the first embodiment is mainly: the connection mode between the sensing signal unit 50 and the sensing line 5 , and in other respects, such as in each period, the driving signal unit 20 and the The signals applied by the sensing signal unit to the driving line 2 and the sensing line 5 are the same, and the functions of each signal are also the same.

The second forward constant current source 29 and the second reverse constant current source 30 of this embodiment both include two connection terminals, and the two connection terminals correspond to the first induction signal input end 501 and the second induction signal input Terminal 502.

In this embodiment, the first sensing signal input end 501 and the second sensing signal input end 502 may be connected to each other.

Embodiment five

The present invention also provides a driving method for a mutual capacitance touch screen, comprising the steps of:

S1: The drive signal unit provides a drive signal to at least one of the drive lines, and in the rising phase of the waveform of the drive signal, the drive line obtains a first positive constant current, and in the falling phase of the waveform of the drive signal stage, the drive line obtains a first reverse constant current;

S2: Receive a sensing signal on the sensing line.

Preferably, the step S1 further includes: providing a sensing signal to the sensing line by the sensing signal unit, and providing a second forward constant current to the sensing line during the positive falling phase of the waveform of the sensing signal, In the reverse rising phase of the waveform of the sensing signal, a second reverse constant current is supplied to the sensing line.

The driving method of the mutual capacitance touch screen according to the present invention and the achieved effects will be further described below with reference to FIG. 10 .

It can be seen from FIG. 10 that by using the driving signal unit 20 and the sensing signal unit 50 of the present invention, the output voltage of the final output terminal 35 will not be deformed due to the large parasitic capacitance, and the maximum voltage value can still be reached and It has a relatively flat waveform for easy detection. In this way, the deformation of the driving pulse waveform caused by the parasitic capacitance is reduced, and the problem of difficult signal detection is solved.

The driving signal unit 20 and the sensing signal unit 50 of the present invention mainly utilize the current source, so that the charge is pumped through the current source to increase the voltage rise and fall speed due to the influence of the parasitic capacitance, thereby improving the deformation of the waveform and overcoming the The adverse effect of the deformation of the driving signal on the signal detection improves the sensitivity of the touch screen.

The mutual-capacitance touch screen of the present invention can be applied to liquid crystal displays, organic light-emitting diode displays, or electronic paper, as long as the mutual capacitance changes between touch and non-touch.

What is described in this specification is only a preferred embodiment of the present invention, which is only used to illustrate the technical solution of the present invention rather than limit the present invention. All technical solutions that can be obtained by persons of ordinary skill in the art through logical analysis, reasoning or limited experiments based on the content disclosed in the present invention shall fall within the scope of the present invention.

Claims (15)

1. mutual capacitance touchscreens, described mutual capacitance touchscreens comprises:

Insulation course;

The drive wire layer is positioned at the first surface of described insulation course, and described drive wire layer comprises at least two drive wires;

Line of induction layer is positioned at the second surface of described insulation course, and described line of induction layer comprises at least two lines of induction;

It is characterized in that, also comprise: the drive signal unit, provide drive signal to described drive wire, the ascent stage at the waveform of described drive signal provides the first forward steady current to described drive wire; Decline stage at the waveform of described drive signal, provide the first reverse steady current to described drive wire.

2. mutual capacitance touchscreens according to claim 1 is characterized in that, described drive signal unit provides drive signal by first switch element to described drive wire.

3. mutual capacitance touchscreens according to claim 2 is characterized in that, described first switch element is a single pole multiple throw.

4. mutual capacitance touchscreens according to claim 3 is characterized in that, described drive signal unit also comprises first positive voltage source and second positive voltage source, or first negative voltage source and second negative voltage source.

5. according to claim 1 or 4 described mutual capacitance touchscreens, it is characterized in that, also comprise: the induced signal unit, described induced signal unit provides induced signal to the described line of induction, the forward decline stage at the waveform of described induced signal, provide the second forward steady current to the described line of induction; Reverse ascent stage at the waveform of described induced signal provides the second reverse steady current to the described line of induction.

6. mutual capacitance touchscreens according to claim 5 is characterized in that, the described line of induction comprises the first induced signal input end and the second induced signal input end.

7. mutual capacitance touchscreens according to claim 6, it is characterized in that, the described second forward constant current source comprises two links, when the described line of induction provided the second forward steady current, two links of the described second forward constant current source connected the described first induced signal input end and the second induced signal input end respectively.

8. mutual capacitance touchscreens according to claim 6, it is characterized in that, the described second reverse constant current source comprises two links, when the described line of induction provided the second reverse steady current, two links of the described second reverse constant current source connected the described first induced signal input end and the second induced signal input end respectively.

9. mutual capacitance touchscreens according to claim 6, it is characterized in that, described induced signal unit also comprises the 3rd forward constant current source and the 3rd reverse constant current source, the forward decline stage at the waveform of described induced signal, provides the 3rd forward steady current to the described line of induction; Reverse ascent stage at the waveform of described induced signal provides the 3rd reverse steady current to the described line of induction.

10. mutual capacitance touchscreens according to claim 9, it is characterized in that, the described line of induction also comprises the 3rd induced signal input end and the 4th induced signal input end, described the 3rd induced signal input end is connected with the described first induced signal input end by switch, and described the 4th induced signal input end is connected with the described second induced signal input end by another switch.

11. mutual capacitance touchscreens according to claim 9 is characterized in that, the described second forward steady current is identical with described the 3rd forward steady current, and the described second reverse steady current is identical with the described the 3rd reverse steady current.

12. mutual capacitance touchscreens according to claim 11 is characterized in that, the described second forward steady current and the described second reverse constant current magnitude equal and opposite in direction.

13. mutual capacitance touchscreens according to claim 12, it is characterized in that, the described second forward constant current source, the described second reverse constant current source, described the 3rd forward constant current source and the described the 3rd reverse constant current source respectively comprise a link, are connected with described first induced signal input end or the described second induced signal input end by switch.

14. the driving method according to each described mutual capacitance touchscreens in the claim 1 to 6 comprises step:

S1: described drive signal unit provides drive signal at least one described drive wire, ascent stage at the waveform of described drive signal, described drive wire obtains the first forward steady current, and in the decline stage of the waveform of described drive signal, described drive wire obtains the first reverse steady current;

S2: receive the induced signal on the described line of induction.

15. the driving method of mutual capacitance touchscreens according to claim 14, it is characterized in that, also comprise at described step S1: provide induced signal to the described line of induction by the induced signal unit, in the forward decline stage of the waveform of described induced signal, provide the second forward steady current to the described line of induction, reverse ascent stage at the waveform of described induced signal provides the second reverse steady current to the described line of induction.

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