Capacitive touch system and method of operating a capacitive touch system

• US 9,182,849 B2
• Filed: 07/31/2012
• Issued: 11/10/2015
• Est. Priority Date: 06/28/2012
• Status: Expired due to Fees

• Current Assignee: Chunghwa Picture Tubes Limited (Tatung Co., Ltd.)
• Original Assignee: Chunghwa Picture Tubes Limited (Tatung Co., Ltd.)
• Inventors: Chiang, Chih-Yin, Hsieh, Ju-Yi, Huang, Tzu-Hsuan
• Primary Examiner(s): Moorad, Waseem
• Application Number:
  US13/562,329
• Publication Number:
  US 20140002411A1
• Time in Patent Office: 1,197 Days
• Field of Search: 345173-179
• US Class Current: 1/1
• CPC Class Codes: G06F 3/0418 for error correction or compensation, e.g. based on parallax, calibration or alignment
• CPC Class Codes: G06F 3/044 by capacitive means
• CPC Class Codes: G06F 3/0443 using a single layer of sensing electrodes
• CPC Class Codes: G06F 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes

Abstract

A capacitive touch system includes a touch panel, a detection circuit, and a microprocessor. The touch panel includes a plurality of scan areas. Each scan area of the plurality of scan areas includes a plurality of sensing units. The detection circuit is coupled to the touch panel for utilizing the Wheatstone bridge principle to transmit driving signals to the plurality of scan areas in turn to generate a detection result corresponding to each scan area of the plurality of scan areas according to a predetermined timing. The microprocessor is used for generating the predetermined timing to the detection circuit, and determining whether each area is touched according to a detection result corresponding to each scan area.

Claims

1. A capacitive touch system, comprising:

a touch panel comprising a plurality of scan areas, wherein each scan area of the plurality of scan areas comprises a plurality of sensing units;

a detection circuit coupled to the touch panel for utilizing the Wheatstone bridge principle to transmit driving signals to the plurality of scan areas in turn to generate a detection result corresponding to each scan area of the plurality of scan areas according to a predetermined timing, the detection circuit comprising;

a first switch circuit for connecting a first sensing line corresponding to a scan area to a first terminal of a power source;

a comparator;

a second switch circuit for connecting two adjacent second sensing lines corresponding to the scan area to the comparator;

a variable capacitor having a first terminal coupled to a second sensing line of the two adjacent second sensing lines and the comparator, and a second terminal coupled to a second terminal of the power source; and

a fixed capacitor having a first terminal coupled to another second sensing line of the two adjacent second sensing lines and the comparator, and a second terminal coupled to the second terminal of the power source; and

a microprocessor for generating the predetermined timing to the detection circuit, and determining whether each scan area is touched according to a detection result corresponding to each scan area.

2. The capacitive touch system of claim 1, wherein the touch panel is a projected capacitive touch panel.

3. The capacitive touch system of claim 2, wherein the projected capacitive touch panel is a mutual capacitance touch panel.

4. The capacitive touch system of claim 1, wherein the detection circuit transmitting the driving signals to the plurality of scan areas in turn according to the predetermined timing is the detection circuit transmitting a driving signal to each scan area row of the plurality of scan areas in turn according to the predetermined timing.

5. The capacitive touch system of claim 1, wherein the detection circuit transmitting the driving signals to the plurality of scan areas in turn according to the predetermined timing is the detection circuit transmitting a driving signal to each scan area column of the plurality of scan areas in turn according to the predetermined timing.

6. The capacitive touch system of claim 1, wherein the microprocessor determining whether the scan area is touched according to the detection result corresponding to the scan area is the microprocessor determining that the scan area is touched when capacitance variation of the variable capacitor comprised in the detection circuit is greater than a predetermined value.

7. The capacitive touch system of claim 1, wherein the first sensing line is located at a first axis of the touch panel, and the two adjacent second sensing lines are located at a second axis of the touch panel.

8. The capacitive touch system of claim 1, wherein the microprocessor is further used for calculating coordinates of at least one touch point of a scan area when the scan area is touched by at least one object.

9. A method of operating a capacitive touch system, the capacitive touch system comprising a touch panel, a detection circuit, and a microprocessor, the touch panel comprising a plurality of scan areas, and each scan area of the plurality of scan areas comprising a plurality of sensing units, the method comprising:

the microprocessor generating a first predetermined timing;

the detection circuit utilizing the Wheatstone bridge principle to transmit driving signals to the plurality of scan areas in turn to generate a detection result corresponding to each scan area of the plurality of scan areas according to the first predetermined timing, wherein the detection circuit comprises;

a first switch circuit for connecting a first sensing line corresponding to a scan area to a first terminal of a power source;

a comparator;

a second switch circuit for connecting two adjacent second sensing lines corresponding to the scan area to the comparator;

a variable capacitor having a first terminal coupled to a second sensing line of the two adjacent second sensing lines and the comparator, and a second terminal coupled to a second terminal of the power source; and

a fixed capacitor having a first terminal coupled to another second sensing line of the two adjacent second sensing lines and the comparator, and a second terminal coupled to the second terminal of the power source; and

the microprocessor executing a corresponding operation according to a detection result corresponding to each scan area.

10. The method of claim 9, wherein the microprocessor executing the corresponding operation according to the detection result corresponding to the scan area is the microprocessor determining whether a next scan area is touched when the microprocessor determines that the scan area is not touched according to the detection result corresponding to the scan area.

11. The method of claim 9, wherein the microprocessor executing the corresponding operation according to the detection result corresponding to the scan area is the microprocessor notifying the detection circuit to transmit a driving signal to each sensing unit of the scan area according to a second predetermined timing to generate a detection result corresponding to each sensing unit of the scan area when the microprocessor determines that the scan area is touched according to the detection result corresponding to the scan area.

12. The method of claim 11, further comprising:

the microprocessor calculating coordinates of at least one touch point of the scan area according to a detection result corresponding to each sensing unit of the scan area.

13. The method of claim 11, wherein the microprocessor determining that the scan area is touched according to the detection result corresponding to the scan area is the microprocessor determining that the scan area is touched when capacitance variation of the variable capacitor comprised in the detection circuit is greater than a predetermined value.

14. The method of claim 9, wherein the detection circuit transmitting the driving signals to the plurality of scan areas in turn according to the first predetermined timing is the detection circuit transmitting a driving signal to each scan area row of the plurality of scan areas in turn according to the first predetermined timing.

15. The method of claim 9, wherein the detection circuit transmitting the driving signals to the plurality of scan areas in turn according to the first predetermined timing is the detection circuit transmitting a driving signal to each scan area column of the plurality of scan areas in turn according to the first predetermined timing.