NOISE CANCELLATION CIRCUIT

• US 20130147755A1
• Filed: 02/15/2012
• Published: 06/13/2013
• Est. Priority Date: 12/13/2011
• Status: Active Grant

• Current Assignee: Chunghwa Picture Tubes Limited
• Original Assignee: Chunghwa Picture Tubes Limited
• Inventors: Lin, Chia-Hsien, Yeh, Liang-Hua
• Granted Patent: US 8,749,506 B2
• Time in Patent Office: Days
• US Class Current: 345/174
• CPC Class Codes: G06F 3/04166 Details of scanning methods, e.g. sampling time, grouping of sub areas or time sharing with display driving Synchronisation with the driving of the display or the backlighting unit to avoid interferences generated internally G06F3/04184
• CPC Class Codes: G06F 3/0418 for error correction or compensation, e.g. based on parallax, calibration or alignment
• CPC Class Codes: G06F 3/0443 using a single layer of sensing electrodes

Abstract

A noise cancellation circuit includes at least one antenna, a multiplexer, and a readout circuit. The at least one antenna is used for coupling noise of a touch panel and noise of a liquid crystal panel coupled to the touch panel. The multiplexer is used for receiving first X axis sensing signals and first Y axis sensing signals of the touch panel. The readout circuit is used for utilizing the noise of the touch panel and the noise of the liquid crystal panel to cancel noise of the touch panel and noise of the liquid crystal panel in the first X axis sensing signals and the first Y axis sensing signals, and to generate and output second X axis sensing signals and second Y axis sensing signals not including the noise of the touch panel and the noise of the liquid crystal panel.

Claims

1. A noise cancellation circuit of a touch panel, the noise cancellation circuit comprising:

at least one antenna for coupling noise of the touch panel and noise of a liquid crystal panel coupled to the touch panel;

a multiplexer for receiving first X axis sensing signals and first Y axis sensing signals of the touch panel, wherein the first X axis sensing signals and the first Y axis sensing signals comprise the noise of the touch panel and the noise of the liquid crystal panel; and

a readout circuit coupled to the multiplexer and said at least one antenna for utilizing the noise of the touch panel and the noise of the liquid crystal panel to cancel the noise of the touch panel and the noise of the liquid crystal panel in the first X axis sensing signals and the first Y axis sensing signals, and to generate and output second X axis sensing signals and second Y axis sensing signals not comprising the noise of the touch panel and the noise of the liquid crystal panel.

2. The noise cancellation circuit of claim 1, wherein the readout circuit comprises:

a differential operational subunit having a first input terminal coupled to the multiplexer for receiving the first X axis sensing signals and the first Y axis sensing signals, a second input terminal coupled to said at least one antenna for receiving the noise of the touch panel and the noise of the liquid crystal panel, and an output terminal for outputting the second X axis sensing signals and the second Y axis sensing signals.

3. The noise cancellation circuit of claim 2, wherein the differential operational subunit is a differential pair.

4. The noise cancellation circuit of claim 2, wherein the differential operational subunit is a differential operation amplifier.

5. The noise cancellation circuit of claim 2, wherein the differential operational subunit is an instrumentation amplifier.

6. The noise cancellation circuit of claim 1, wherein said at least one antenna is installed in a transparent conductive layer of the touch panel.

7. The noise cancellation circuit of claim 6, wherein said at least one antenna is located outside an active area of the touch panel.

8. The noise cancellation circuit of claim 1, wherein said at least one antenna is installed in a metal layer of the touch panel.

9. The noise cancellation circuit of claim 8, wherein said at least one antenna is located outside an active area of the touch panel.

10. The noise cancellation circuit of claim 1, wherein said at least one antenna is coupled to the readout circuit through a flexible printed circuit (FPC) coupled to the touch panel.

11. The noise cancellation circuit of claim 1, wherein said at least one antenna is installed in a color filter transparent conductive layer of the liquid crystal panel.

12. The noise cancellation circuit of claim 11, wherein said at least one antenna is located outside an active area of the liquid crystal panel.

13. The noise cancellation circuit of claim 1, wherein said at least one antenna is installed in a control circuit array layer of the liquid crystal panel.

14. The noise cancellation circuit of claim 13, wherein said at least one antenna is located outside an active area of the liquid crystal panel.

15. The noise cancellation circuit of claim 1, wherein said at least one antenna is coupled to the readout circuit through a flexible printed circuit coupled to the liquid crystal panel.

16. The noise cancellation circuit of claim 1, wherein the touch panel is a projected capacitive touch panel.

17. The noise cancellation circuit of claim 14, wherein the projected capacitive touch panel is a mutual capacitance touch panel.

18. The noise cancellation circuit of claim 14, wherein the projected capacitive touch panel is a self-capacitance touch panel.