IN-CELL MULTI-TOUCH PANEL SYSTEM WITH LOW NOISE AND TIME DIVISION MULTIPLEXING AND ITS DRIVING METHOD

• US 20140354590A1
• Filed: 05/28/2014
• Published: 12/04/2014
• Est. Priority Date: 05/28/2013
• Status: Active Grant

• Current Assignee: FocalTech Systems Co.,Ltd
• Original Assignee: Orise Technology Co., Ltd (FocalTech Systems Co.,Ltd)
• Inventors: WANG, Hsin-Hao, HUANG, Yen-Lin
• Granted Patent: US 9,547,396 B2
• Time in Patent Office: Days
• US Class Current: 345/174
• CPC Class Codes: G06F 2203/04104 Multi-touch detection in digitiser, i.e. details about the simultaneous detection of a plurality of touching locations, e.g. multiple fingers or pen and finger
• CPC Class Codes: G06F 3/0443 using a single layer of sensing electrodes

Abstract

An in-cell multi-touch panel system includes: an in-cell touch display panel, a touch display control system. In a first frame time interval, the touch display control system drives the in-cell touch display panel and samples the sensing voltage from the in-cell touch display panel to determine whether there is an approaching external object and noise interference. In a second frame time interval, the touch display control system finds out a frequency with minimum noise for use as a frequency of the touch driving signal when the noise interference exists. In a third frame time interval, the touch display control system is based on the frequency with minimum noise to correspondingly generate the touch driving signal so as to determine whether there is an approaching external object.

Claims

1. An in-cell multi-touch panel system with low noise and time division multiplexing, comprising:

an in-cell touch display panel, for displaying an image signal and sensing an external object; and

a touch display control system connected to the in-cell touch display panel, for sequentially outputting a display driving signal to the in-cell touch display panel so as to display the image signal, and for sequentially outputting a touch driving signal to the in-cell touch display panel for sampling a sensing voltage from the in-cell touch display panel so as to determine whether there is the external object,

wherein, the touch display control system drives the in-cell touch display panel and samples the sensing voltage from the in-cell touch display panel to determine whether there is the external object and noise interference during a first frame time interval, the touch display control system finds out a frequency with the minimum noise for use as a frequency of the touch driving signal when the noise interference exists during a second frame time interval, and the touch display control system is based on the frequency with minimum noise to correspondingly generate the touch driving signal so as to determine whether there is the external object during a third frame time interval.

2. The panel system as claimed in claim 1, wherein the in-cell touch display panel comprises:

a thin film transistor (TFT) layer, having K gate driving lines and L source driving lines, to drive corresponding transistors and capacitors based on a display pixel signal and the display driving signal thereby performing a display operation;

a sensing electrode layer, which has M first conductor lines to sense an approaching external object based on the touch driving signal; and

a common voltage and touch driving layer, which has N second conductor lines to receive a common voltage on displaying and the touch driving signal on touch sensing;

wherein the M first conductor lines and the L second source driving lines are disposed on a first direction, the K gate driving lines and the N second conductor lines are disposed on a second direction, a mutual capacitance is formed on each overlap between the first conductor lines and the second conductor lines, and the first direction is vertical to the second direction, where K, L, M and N are positive integer respectively and K is a value greater than N.

3. The panel system as claimed in claim 2, wherein the touch display control system is connected to the TFT layer, the sensing electrode layer, and the common voltage and touch driving layer, for sequentially providing the display driving signal to the K gate driving lines to turn on corresponding transistors and sequentially providing the display pixel signal to the L source driving lines to perform the display operation, and the touch display control system sequentially provides the touch driving signal to the N second conductor lines and samples a sensing voltage from the M first conductor lines, for determining whether there is the external object.

4. The panel system as claimed in claim 3, wherein the K gate driving lines are divided into N groups, each corresponding to one second conductor line such that the second conductor line is connected to the common voltage when the group receives the display driving signal, and the touch display control system first determines whether the display driving signal is concurrently provided to an i-th group of gate driving lines and then provides the touch driving signal to an i-th second conductor line corresponding to the i-th group of gate driving lines when the display driving signal is not concurrently provided, where i=1 to N.

5. The panel system as claimed in claim 4, wherein the touch display control system provides the touch driving signal to a (j−

1)-th second conductor line when the touch display control system provides the display driving signal to a j-th group of gate driving lines, where j=2 to N.

6. The panel system as claimed in claim 2, wherein the touch display control system provides the common voltage to an N-th second conductor line to thus connect the N-th second conductor line to the common voltage when the touch display control system provides the display driving signal to the first group of gate driving lines.

7. The panel system as claimed in claim 2, wherein the touch display control system comprises:

a touch detector, connected to the common voltage and touch driving layer of the in-cell touch display panel, for detecting the mutual capacitance of the in-cell touch display panel and correspondingly generate a touch coordinate; and

a noise and timing controller, connected to the touch detector, in order to detect a noise interference based on the touch coordinate and change the frequency of the touch driving signal to correspondingly generate the display driving signal and a switch signal when the noise interference exists.

8. The panel system as claimed in claim 7, wherein the touch display control system further comprises:

a touch driver, for generating the touch driving signal;

a common grounding signal generator, for generating a common grounding signal based on the display driving signal;

a switch, connected to the noise and timing controller, the touch driver, the common grounding signal generator, and the in-cell touch display panel, for outputting the touch driving signal or the common grounding signal to the in-cell touch display panel based on the switch signal; and

a display driver, connected to the noise and timing controller for outputting the display driving signal to the in-cell touch display panel.

9. The panel system as claimed in claim 7, wherein the touch detector comprises:

a detection circuit, having M sensors to detect the mutual capacitance and further generate corresponding M sensing signals;

a programmable gain amplifier, connected to the detection circuit, for amplifying the M sensing signals and further generating M amplified signals;

a analog to digital converter (ADC), connected to the programmable gain amplifier, for converting the M amplified signals into M digital signals for N times so as to generate N×

M digital signals;

an offset device, connected to the ADC for performing an offset adjustment on the N×

M digital signals to generate N×

M offset signals;

a frame buffer, connected to the offset device, for buffering the N×

M offset signals outputted by the offset device; and

a coordinate decision device, connected to the frame buffer, for determining the touch coordinate on the in-cell touch display panel touched by a grounded conductor or a finger.

10. The panel system as claimed in claim 7, wherein the noise and timing controller comprises:

a time domain noise detector, connected to the coordinate decision device, for detecting a noise interference based on the touch coordinate and generating an indicative signal when the noise interference exists;

a frequency-hopping spread spectrum detector circuit, connected to the time domain noise detector, for performing a frequency hopping based on the indicative signal to generate a frequency hopping indicative signal representative of the frequency hopping;

a frequency multiplexing controller, connected to the frequency-hopping spread spectrum detector circuit, for searching a set of candidate frequencies based on the frequency hopping indicative signal to find a cleanest driving frequency for output.

an oscillator, connected to the frequency multiplexing controller, for generating an oscillation signal based on the cleanest driving frequency outputted by the frequency multiplexing controller; and

a timing controller, connected to the oscillator, for generating the display driving signal and the switch signal based on the oscillation signal.

11. The panel system as claimed in claim 7, wherein the common voltage is a DC common voltage or an AC common voltage.

12. A driving method for an in-cell multi-touch panel system with low noise and time division multiplexing including an in-cell touch display panel and a touch display control system, the driving method comprising the steps of:

(A) selecting a frequency from a set of candidate frequencies to generate a display driving signal and a touch driving signal, such that the touch display control system sequentially outputs the display driving signal to the in-cell touch display panel for performing a display of an image signal, and sequentially outputs the touch driving signal to the in-cell touch display panel for sampling a sensing voltage from the in-cell touch display panel, so as to determine whether there is an approaching external object;

(B) during a first frame time interval, sampling the sensing voltage from the in-cell touch display panel when the touch display control system drives the in-cell touch display panel, so as to determine whether there is an approaching external object and noise interference;

(C) during a second frame time interval, using the touch display control system to change with the candidate frequencies and find out a frequency of the touch driving signal with minimum noise when there is noise interference; and

(D) during a third frame time interval, using the touch display control system to generate the touch driving signal corresponding to the frequency with the minimum noise so as to determine whether the external object approaches to the in-cell touch display panel.

13. The driving method as claimed in claim 12, wherein the in-cell touch display panel comprises a thin film transistor (TFT) layer with K gate driving lines and L source driving lines, a sensing electrode layer with M first conductor lines, and a common voltage and touch driving layer with N second conductor lines, where K, L, M, N are each a positive integer and K has a value greater than N, and wherein the M first conductor lines and the L second source driving lines are disposed on a first direction, the K gate driving lines and the N second conductor lines are disposed on a second direction, a mutual capacitance is formed on each overlap between the first conductor lines and the second conductor lines, and the first direction is substantially vertical to the second direction.

14. The driving method as claimed in claim 13, wherein the touch display control system is connected to the TFT layer, the sensing electrode layer, and the common voltage and touch driving layer for sequentially providing the display driving signal to the K gate driving lines to turn on a corresponding transistor and sequentially providing the display pixel signal to the L source driving lines to charge the capacitor of a corresponding pixel through the corresponding transistor so as to perform the display operation, and the touch display control system sequentially provides the touch driving signal to the N second conductor lines and samples a sensing voltage from the M first conductor lines for determining whether there is an approaching external object.

15. The driving method as claimed in claim 14, wherein the K gate driving lines are divided into N groups, each corresponding to one second conductor line such that the second conductor line is connected to the common voltage when the group receives the display driving signal and, if the touch display control system provides the touch driving signal to an i-th second conductor line, the touch display control system first determines whether the display driving signal is concurrently provided to a corresponding i-th group of gate driving lines, otherwise provides the touch driving signal to the i-th second conductor line, where i=1 to N.

16. The driving method as claimed in claim 12, wherein step (B) comprises:

(B1) comparing a current two-dimensional touch data of the in-cell touch display panel with a two-dimensional touch reference data to calculate a data difference;

(B2) determining whether the data difference is over a first threshold;

(B3) calculating a whole data difference when the data difference is not over the first threshold;

(B4) determining whether there is noise interference based on the whole data difference; and

(B5) configuring the current two-dimensional touch data when there is no noise interference.

17. The driving method as claimed in claim 16, wherein step (C) is executed when step (B4) determines that there is noise interference.

18. The driving method as claimed in claim 17, wherein step (C) comprises:

(C1) selecting a different frequency from the set of candidate frequencies to generate the touch driving signal for driving the in-cell touch display panel;

(C2) reading a two-dimensional touch data of the in-cell touch display panel to calculate the whole data difference with respect to all corresponding data of the two-dimensional touch reference data; and

(C3) selecting a frequency of the touch driving signal with a minimum whole data difference.