Touch panel, anti-noise unit and method for processing a noise

This application claims the benefit of Taiwan Patent Application No. 101100961, filed on Jan. 10, 2012, which is hereby incorporated by reference for all purposes as if fully set forth herein.

1. Field of Invention

The present invention relates to a touch panel, and more particularly to a touch panel which can reject a noise.

2. Related Art

Recently, the technology of a touch panel is developed quickly. For example, resistance type touch panel, capacitance type touch panel, sound wave type touch panel and optics type touch panel have been widely applied to communication products, computer devices and consumptive electronic products so as to further increase the efficiency and convenience of the applied electronic product.

The optics type touch panel can input a signal by a finger so as to have convenience of input operation, wherein the input operation does not need to press the touch panel. Thus, this touch panel has no disadvantage of a stress caused by repeatedly touching the touch panel, and a damage caused by deformation. Also, this touch panel has simple constitution, less components, and high yield rate of the product so as to decrease the cost by suitably using the mass production.

FIG. 1 is a view showing a basic constitution of conventional touch sensor 100 . A glass substrate 110 and an indium tin oxide (ITO) layer 130 are boned by an optically clear adhesive (OCA) 120 located therebetween. Furthermore, the indium tin oxide (ITO) layer 130 and a cover lens 140 are boned by another OCA 120 located therebetween, thereby finishing the touch sensor 100 .

FIG. 2 is a view showing a basic constitution of conventional touch panel 200 . A touch sensor 100 is disposed above a liquid crystal display (LCD) module 250 so as to finish the touch panel 200 . For example, the glass substrate 110 of the touch sensor 100 is bonded to the LCD module 250 , and there is an air gap 260 between the LCD module 250 and the glass substrate 110 .

FIG. 3 is a block diagram showing signal processing of the conventional touch panel. During touching, a touch sensor 100 senses variances in capacitance value and then outputs an analog signal to an analog multiplexer 320 . The analog multiplexer 320 outputs the scanned analog signal to an analog/digital converter 330 by means of a scanning action. The analog/digital converter 330 converts the analog signal to digital signal, and then outputs the digital signal to a microcontroller 340 . The microcontroller 340 processes the digital signal, and then outputs a control signal. Finally, the control signal transmitted to an operating system 360 through an interface 350 so as to calculate and then determine a touch position.

However, after the touch sensor is installed on the LCD module, a noise generated by the LCD module interferes with the touch sensor so as to cause the touch panel to wrong determine the touch position. The noise is resulted from the couple effect between a common voltage of the LCD module and data lines, e.g. particularly in a heavy loading picture or fast renewed picture so as to cause the picture to be unstable. Recently, a general method is to adjust a firmware so as to solve the problem of wrong determining the touch position. For example, the frequency that is converted from analog to digital is adjusted, and an algorithm of the microcontroller for processing signals is adjusted. However, this adjusting method will extend the processing time of the sensing signal from touch sensor to the operating system.

Therefore, it is required to provide an anti-noise touch panel capable of solving the forgoing problems.

The present invention is directed to a touch panel, including a display module, a touch sensor, an anti-noise unit and a signal processing unit. The display module generates a noise. The touch sensor is disposed above the display module and outputs an abnormal signal, wherein the abnormal signal includes the noise and a sensing signal. The anti-noise unit is adapted to receive the abnormal signal and then reject the noise so as to form the sensing signal. The signal processing unit is adapted to process the sensing signal.

The compared signal outputted by the comparison circuit of the anti-noise unit of the present invention is the high level signal or low level signal of the normal sensing signal of the touch sensor, i.e., the anti-noise unit of the present invention certainly rejects the noise of the abnormal signal and transmits the normal sensing signal, whereby the noise generated by the LCD module which interferes with the touch sensor do not cause the touch panel to wrong determine the touch position. Thus, it is not necessary that the analog-to-digital converting frequency is adjusted and the algorithm of the microcontroller for processing signals is adjusted to solve the problem of wrong determining the touch position, whereby the touch panel of the present invention will not extend the processing time of the sensing signal from touch sensor to the operating system.

In order to make the aforementioned and other objectives, features and advantages of the present invention comprehensible, embodiments are described in detail below with reference to the accompanying drawings.

The present invention will become more fully understood from the detailed description given herein below for illustration only, and thus are not limitative of the present invention, and wherein:

FIG. 1 is a view showing a basic constitution of conventional touch sensor;

FIG. 2 is a view showing a basic constitution of conventional touch panel;

FIG. 3 is a block diagram showing signal processing of the conventional touch panel;

FIG. 4 is a block diagram showing a constitution of a touch panel having an anti-noise unit according to an embodiment of the present invention;

FIG. 5 is a block diagram showing signal processing of a touch panel having an anti-noise unit according to an embodiment of the present invention;

FIG. 6 is a circuit diagram of an anti-noise unit according to an embodiment of the present invention;

FIG. 7 is flow diagram of a method for processing noises of a touch panel according to this embodiment of the present invention; and

FIG. 8 shows timings of an abnormal signal, a first filtering signal, a common voltage coupling signal, a second filtering signal and a compared signal according to this embodiment of the present invention.

FIG. 4 is a block diagram showing a constitution of a touch panel having an anti-noise unit according to an embodiment of the present invention. A touch sensor 410 is disposed above a display module 450 (e.g. liquid crystal display module). When the touch sensor 410 outputs a sensing signal, a noise (e.g. common voltage coupling signal) generated by the display module 450 interferes with the touch sensor 410 so as to change the sensing signal to an abnormal signal, i.e., the abnormal signal includes the normal sensing signal and the noise. The touch sensor 410 transmits the abnormal signal to an anti-noise unit 420 . The anti-noise unit 420 receives the abnormal signal of the touch sensor 410 and then rejects the noise of the abnormal signal so as to form normal sensing signal (i.e. the original sensing signal), and the normal sensing signal is transmitted to a signal processing unit 430 . The signal processing unit 430 is adapted to process the normal sensing signal.

Referring to FIG. 5 , particularly, the signal processing unit 430 includes an analog multiplexer 520 , an analog/digital converter (ADC) 530 , a microcontroller 540 , an interface 550 and an operating system 560 . Originally, the touch sensor 410 outputs the sensing signal, but the touch sensor 410 transmits the abnormal signal (i.e., the abnormal signal includes the sensing signal and the noise) to the analog multiplexer 520 because of the effect of the noise generated by the display module 450 . The analog multiplexer 520 outputs the scanned abnormal signal to the anti-noise unit 420 by means of a scanning action. The anti-noise unit 420 changes the abnormal signal to the normal sensing signal, and then outputs the normal sensing signal to the analog/digital converter 530 . The analog/digital converter 530 converts the normal sensing signal from the analog signal to digital signal, and then outputs the digital signal to the microcontroller 540 . The microcontroller 540 processes the digital signal, and then outputs a control signal. Finally, the control signal is transmitted to the operating system 560 through the interface 550 so as to calculate and then determine a touch position. For example, the touch position is calculated by a change of the sensing signal resulted from variances in capacitance value during touching.

FIG. 6 is a circuit diagram of the anti-noise unit 420 according to an embodiment of the present invention. The anti-noise unit 420 includes a first filtering circuit 610 , a second filtering circuit 620 and a comparison circuit 630 . The first filtering circuit 610 includes a first operational amplifier IC 1 , a first switch Q 10 , a second switch Q 20 and a third switch Q 30 . A positive phase input end of the first operational amplifier IC 1 receives a reference voltage, and a negative phase input end of the first operational amplifier IC 1 receives an abnormal signal 640 (e.g. the abnormal signal transmitted by the touch sensor). The first operational amplifier IC 1 compares the abnormal signal 640 with the reference voltage, and an output end of the first operational amplifier IC 1 outputs a compared result. The first switch Q 10 includes a first end Q 11 , a second end Q 12 and a control end Q 13 . The first end Q 11 receives the abnormal signal 640 . The second end Q 12 outputs a first filtering signal 660 . The control end Q 13 is electrically connected to the output end of the first operational amplifier IC 1 , whereby the compared result outputted by the first operational amplifier IC 1 can control whether the first end Q 11 electrically contacts the second end Q 12 of the first switch Q 10 or not. The second switch Q 20 includes a first end Q 21 , a second end Q 22 and a control end Q 23 . The first end Q 21 is electrically connected to the second end Q 12 of the first switch Q 10 . The second end Q 22 is electrically connected to the reference voltage. The control end Q 23 is electrically connected to the output end of the first operational amplifier IC 1 , whereby the compared result outputted by the first operational amplifier IC 1 can control whether the first end Q 21 electrically contacts the second end Q 22 of the first switch Q 20 or not. The third switch Q 30 includes a first end Q 31 , a second end Q 32 and a control end Q 33 . The first end Q 31 is electrically connected to the second end Q 12 of the first switch Q 10 . The second end Q 32 is electrically connected to the reference voltage. The control end Q 33 receives the abnormal signal 640 , whereby the abnormal signal 640 can control whether the first end Q 31 electrically contacts the second end Q 32 of the first switch Q 30 or not.

The second filtering circuit 620 includes a second operational amplifier IC 2 , a fourth switch Q 40 , a fifth switch Q 50 and a sixth switch Q 60 . A positive phase input end of the second operational amplifier IC 2 receives the reference voltage, and a negative phase input end of the second operational amplifier IC 2 receives a common voltage coupling signal 650 (e.g. the common voltage coupling signal 650 is a noise resulted from the couple effect between a common voltage of the LCD module and data lines). The second operational amplifier IC 2 compares the common voltage coupling signal 650 with the reference voltage, and an output end of the second operational amplifier IC 2 outputs a compared result. The fourth switch Q 40 includes a first end Q 41 , a second end Q 42 and a control end Q 43 . The first end Q 41 receives the common voltage coupling signal 650 . The second end Q 42 outputs a second filtering signal 670 . The control end Q 43 is electrically connected to the output end of the second operational amplifier IC 2 , whereby the compared result outputted by the second operational amplifier IC 2 can control whether the first end Q 41 electrically contacts the second end Q 42 of the fourth switch Q 40 or not. The fifth switch Q 50 includes a first end Q 51 , a second end Q 52 and a control end Q 53 . The first end Q 51 is electrically connected to the second end Q 42 of the fourth switch Q 40 . The second end Q 52 is electrically connected to the reference voltage. The control end Q 53 is electrically connected to the output end of the second operational amplifier IC 2 , whereby the compared result outputted by the second operational amplifier IC 2 can control whether the first end Q 51 electrically contacts the second end Q 52 of the fifth switch Q 50 or not. The sixth switch Q 60 includes a first end Q 61 , a second end Q 62 and a control end Q 63 . The first end Q 61 is electrically connected to the second end Q 42 of the fourth switch Q 40 . The second end Q 62 is electrically connected to the reference voltage. The control end Q 63 receives the common voltage coupling signal 650 , whereby the common voltage coupling signal 650 can control whether the first end Q 61 electrically contacts the second end Q 62 of the sixth switch Q 60 or not.

The comparison circuit 630 includes a third operational amplifier IC 3 , a fourth operational amplifier IC 4 , a seventh switch Q 70 , a eighth switch Q 80 , a ninth switch Q 90 and a tenth switch Q 100 . A positive phase input end of the third operational amplifier IC 3 receives the first filtering signal 660 of the first filtering circuit 610 , and a negative phase input end of the third operational amplifier IC 3 receives the second filtering signal 670 of the second filtering circuit 620 . The third operational amplifier IC 3 compares the first filtering signal 660 with the second filtering signal 670 , and an output end of the third operational amplifier IC 3 outputs a compared result. A negative phase input end of the fourth operational amplifier IC 4 receives the first filtering signal 660 of the first filtering circuit 610 , and a positive phase input end of the fourth operational amplifier IC 4 receives the second filtering signal 670 of the second filtering circuit 620 . The fourth operational amplifier IC 4 compares the first filtering signal 660 with the second filtering signal 670 , and an output end of the fourth operational amplifier IC 4 outputs a compared result. The seventh switch Q 70 includes a first end Q 71 , a second end Q 72 and a control end Q 73 . The control end Q 73 is electrically connected to the output end of the fourth operational amplifier IC 4 , whereby the compared result outputted by the fourth operational amplifier IC 4 can control whether the first end Q 71 electrically contacts the second end Q 72 of the first switch Q 70 or not. The eighth switch Q 80 includes a first end Q 81 , a second end Q 82 and a control end Q 83 . The first end Q 81 is electrically connected to the second end Q 72 of the seventh switch Q 70 . The second end Q 82 is electrically connected to the reference voltage. The control end Q 83 is electrically connected to the output end of the third operational amplifier IC 3 , whereby the compared result of the third operational amplifier IC 3 can control whether the first end Q 81 electrically contacts the second end Q 82 of the first switch Q 80 or not. The ninth switch Q 90 includes a first end Q 91 , a second end Q 92 and a control end Q 93 . The first end Q 91 is electrically connected to a high level signal (i.e., the high level signal is a high level of the normal sensing signal of the touch sensor 410 ). The second end Q 92 is electrically connected to the first end Q 71 of the seventh switch Q 70 for outputting a compared signal 680 . The control end Q 93 is electrically connected to the output end of the third operational amplifier IC 3 , whereby the compared result of the third operational amplifier IC 3 can control whether the first end Q 91 electrically contacts the second end Q 92 of the first switch Q 90 or not. The tenth switch Q 100 includes a first end Q 101 , a second end Q 102 and a control end Q 103 . The first end Q 101 is electrically connected to the second end Q 92 of the ninth switch Q 90 for outputting the compared signal 680 . The second end Q 102 is electrically connected to the reference voltage. The control end Q 103 is electrically connected to the output end of the fourth operational amplifier IC 4 , whereby the compared result of the fourth operational amplifier IC 4 can control whether the first end Q 101 electrically contacts the second end Q 102 of the first switch Q 100 or not.

As described above, the first switch Q 10 , the third switch Q 30 , the fourth switch Q 40 , the sixth switch Q 60 , the seventh switch Q 70 and the eighth switch Q 80 are P-type field effect transistor, and the second switch Q 20 , the fifth switch Q 50 , the ninth switch Q 90 and the tenth switch Q 100 are N-type field effect transistor. The reference voltage is defined as a low level signal (the low level signal is the low level of the normal sensing signal of the touch sensor 410 ), e.g. 0 volt. The compared signal 680 outputted by the comparison circuit 630 is the high level or low level of the normal sensing signal of the touch sensor 410 , i.e., the noise of the abnormal signal can be rejected so as to form the normal sensing signal.

FIG. 7 is flow diagram of a method for processing noises of a touch panel according to this embodiment of the present invention. Referring to FIG. 6 again, the first filtering circuit 610 receives the abnormal signal 640 , and the second filtering circuit 620 receives the common voltage coupling signal 650 (in step S 700 ). The first filtering circuit 610 permits the abnormal signal 640 that is greater than the reference voltage to pass so as to form the first filtering signal 660 , and the first filtering signal 660 is transmitted to the comparison circuit 630 . Also, the second filtering circuit 620 permits the common voltage coupling signal 650 that is greater than the reference voltage to pass so as to form the second filtering signal 670 , and the second filtering signal 670 is transmitted to the comparison circuit 630 (in step S 710 ). The comparison circuit 630 receives the first filtering signal 660 and the second filtering signal 670 , and compares the first filtering signal 660 with the second filtering signal 670 so as to output the compared signal 680 . For example, the comparison circuit 630 judges whether the first filtering signal 660 is greater than the second filtering signal 670 or not (in step S 720 ). If the first filtering signal 660 is greater than the second filtering signal 670 , the comparison circuit 630 outputs the high level signal (in step S 730 ). If the first filtering signal 660 is not greater than the second filtering signal 670 , the comparison circuit 630 outputs the low level signal (in step S 740 ).

FIG. 8 shows timings of the abnormal signal 640 , the first filtering signal 660 , the common voltage coupling signal 650 , the second filtering signal 670 and the compared signal 680 according to this embodiment of the present invention. There are four cases according to the positive phase and negative phase of the abnormal signal 640 and the common voltage coupling signal 650 as follows: The first case (A) is that the abnormal signal 640 and the common voltage coupling signal 650 are positive voltage signals, and the abnormal signal 640 is greater than the common voltage coupling signal 650 . The second case (B) is that the abnormal signal 640 is a positive voltage signal, and the common voltage coupling signal 650 is a negative voltage signal, and the abnormal signal 640 is greater than the common voltage coupling signal 650 . The third case (C) is that the abnormal signal 640 and the common voltage coupling signal 650 are positive voltage signals, and the abnormal signal 640 is smaller than the common voltage coupling signal 650 . The fourth case (D) is that the abnormal signal 640 and the common voltage coupling signal 650 are negative voltage signals, and the abnormal signal 640 is greater than the common voltage coupling signal 650 . More detailed, referring to FIGS. 6 and 8 again, they show actions and signals of circuit node of the noise processing unit in this embodiment. In the first case (A), both of the first operational amplifier IC 1 and the second operational amplifier IC 2 output the low level signals (e.g. 0 volt level), the second switch Q 20 , the third switch Q 30 , the fifth switch Q 50 and the sixth switch Q 60 are turn off, the first switch Q 10 is turn on and outputs the first filtering signal 660 to the third operational amplifier IC 3 , and the fourth switch Q 40 is turn on and outputs the second filtering signal 670 to the fourth operational amplifier IC 4 , wherein the first filtering signal 660 is greater than the second filtering signal 670 such that the third operational amplifier IC 3 outputs the high level signal, and the fourth operational amplifier IC 4 outputs the low level signal. The seventh switch Q 70 is turn on, the eighth switch Q 80 and the tenth switch Q 100 are turn off, and the ninth switch Q 90 is turn on and outputs the compared signal 680 being the high level signal.

In the second case (B), the first operational amplifier IC 1 outputs the low level signal (e.g. 0 volt level), the second operational amplifier IC 2 outputs the high level signal, the second switch Q 20 , the third switch Q 30 and the fourth switch Q 40 are turn off, the first switch Q 10 is turn on and outputs the first filtering signal 660 to the third operational amplifier IC 3 , the fifth switch Q 50 and the sixth switch Q 60 are turn on and output the low level signals to the fourth operational amplifier IC 4 , wherein the first filtering signal 660 is greater than the low level signal such that the third operational amplifier IC 3 outputs the high level signal, and the fourth operational amplifier IC 4 outputs the low level signal. The seventh switch Q 70 is turn on, the eighth switch Q 80 and the tenth switch Q 100 are turn off, and the ninth switch Q 90 is turn on and outputs the compared signal 680 being the high level signal.

In the third case (C), both of the first operational amplifier IC 1 and the second operational amplifier IC 2 output the low level signals (e.g. 0 volt level), the second switch Q 20 , the third switch Q 30 , the fifth switch Q 50 and the sixth switch Q 60 are turn off, the first switch Q 10 is turn on and outputs the first filtering signal 660 to the third operational amplifier IC 3 , and the fourth switch Q 40 is turn on and outputs the second filtering signal 670 to the fourth operational amplifier IC 4 , wherein the first filtering signal 660 is smaller than the second filtering signal 670 such that the third operational amplifier IC 3 outputs the low level signal, and the fourth operational amplifier IC 4 outputs the high level signal. The eighth switch Q 80 is turn on, the seventh switch Q 70 and the ninth switch Q 90 are turn off, and the tenth switch Q 100 is turn on and outputs the compared signal 680 being the low level signal.

In the fourth case (D), both of the first operational amplifier IC 1 and the second operational amplifier IC 2 output the high level signals, both of the third switch Q 30 and the sixth switch Q 60 are turn on and output the low level signal (e.g. 0 volt level), the first switch Q 10 and the fourth switch Q 40 are turn off, the second switch Q 20 is turn on and outputs the low level signal to the third operational amplifier IC 3 , and the fifth switch Q 50 is turn on and outputs the low level signal to the fourth operational amplifier IC 4 , wherein all of the positive and negative input ends of the third operational amplifier IC 3 and the fourth operational amplifier IC 4 receive the low level signals such that both of the third operational amplifier IC 3 and the fourth operational amplifier IC 4 output the low level signal. The ninth switch Q 90 and the tenth switch Q 100 are turn off, the eighth switch Q 80 is turn on, and the seventh switch Q 70 is turn on and outputs the compared signal 680 being the low level signal.

In above-mentioned case (A), (B), (C) and (D), the compared signal outputted by the comparison circuit of the anti-noise unit of the present invention is the high level signal or low level signal of the normal sensing signal of the touch sensor, i.e., the anti-noise unit of the present invention certainly rejects the noise of the abnormal signal and transmits the normal sensing signal, whereby the noise generated by the LCD module which interferes with the touch sensor do not cause the touch panel to wrong determine the touch position. Thus, it is not necessary that the analog-to-digital converting frequency is adjusted and the algorithm of the microcontroller for processing signals is adjusted to solve the problem of wrong determining the touch position, whereby the touch panel of the present invention will not extend the processing time of the sensing signal from touch sensor to the operating system.

The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.