METHOD AND APPARATUS COMPENSATING NOISE IN TOUCH PANEL

• US 20110193817A1
• Filed: 01/25/2011
• Published: 08/11/2011
• Est. Priority Date: 02/05/2010
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: BYUN, San-ho, CHOI, Yoon-kyung
• Granted Patent: US 8,736,573 B2
• Time in Patent Office: Days
• US Class Current: 345/174
• CPC Class Codes: G06F 3/0412 Digitisers structurally integrated in a display
• CPC Class Codes: G06F 3/0416 Control or interface arrangements specially adapted for digitisers
• CPC Class Codes: G06F 3/04184 Synchronisation with the driving of the display or the backlighting unit to avoid interferences generated internally
• CPC Class Codes: G06F 3/044 by capacitive means
• 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
• CPC Class Codes: G06F 3/045 using resistive elements, e.g. a single continuous surface or two parallel surfaces put in contact

Abstract

Touch screen systems and method of compensating noise in same are presented. One touch screen system includes; a touch screen panel having sense channels providing a sense output corresponding to a capacitance variation associated with an applied touch input as detected by one or more sensing units connected to the sense channels. A parasitic capacitance is accumulated in the sense channels as the touch input is applied. The touch screen system also includes a touch controller receiving the sense output and including; a noise compensation block configured to generate a compensation capacitance to compensate for the parasitic capacitance and provide a compensation output, and a signal conversion unit that receives the sense output and the compensation output and generates a noise compensated sense output.

Claims

1. An apparatus compensating noise in a touch screen system, the apparatus comprising:

a touch screen panel including sense channels providing a sense output corresponding to a capacitance variation associated with an applied touch input as detected by one or more sensing units connected to the sense channels, wherein a parasitic capacitance is accumulated as the touch input is applied; and

a touch controller receiving the sense output and comprising;

a noise compensation block configured to generate a compensation capacitance to compensate for the parasitic capacitance and provide a compensation output; and

a signal conversion unit configured to receive the sense output and the compensation output, and generates a noise compensated sense output.

2. The apparatus of claim 1, wherein the noise compensation block is further configured to be by-passed by an output of at least one of the sense channels, such that the at least one of the sense channels is directed connected to one input of the signal conversion unit.

3. The apparatus of claim 2, wherein the noise compensation block comprises:

an amplifier having a gain reset switch disposed between a inverting input and an output of the amplifier;

a compensation feedback capacitor connected in parallel with the gain reset switch; and

a noise compensation capacitor disposed between the output of the amplifier and an input of the signal conversion unit, wherein a number of the sense channels unaffected by the applied touch input are connected in parallel to the inverting input of the amplifier.

4. The apparatus of claim 3, wherein the number of sense channels unaffected by the applied touch input comprises;

a first number of unaffected sense channels disposed in one direction from a number of sense channels affected by the applied touch input among; and

a second number of unaffected sense channels equal in number to the first number of unaffected sense channels and disposed in another direction from the number of sense channels affected by the applied touch input.

5. The apparatus of claim 4, wherein a constant voltage is applied to at least one of the number of sense channels affected by the applied touch input.

6. The apparatus of claim 5, wherein the at least one sense channel receiving the constant voltage is a sense channel directly adjacent to the at least one of the sense channels directed connected to the input of the signal conversion unit.

7. The apparatus of claim 3, wherein capacitance of the compensation feedback capacitor is substantially the same as a parasitic capacitance between at least one of the sensing channels and a common electrode.

8. The apparatus of claim 7, wherein capacitance of the noise compensation capacitor is substantially the same as a capacitance obtained by dividing the capacitance of the compensation feedback capacitor by a number of sense channels unaffected by the applied touch input.

9. The apparatus of claim 3, further comprising:

a multiplexer connecting each of the sense channels unaffected by the applied touch input to the inverting input of the amplifier.

10. The apparatus of claim 3, wherein the touch screen panel and touch controller are integrated into a single body.

11. The apparatus of claim 10, wherein the touch screen panel is an ON-cell type touch panel.

12. The apparatus of claim 1, wherein the touch screen panel is an overlay touch panel.

13. A method compensating noise in a touch screen system, the method comprising:

sensing a capacitance variation associated with an applied touch input using sensing units connected to multiple sense channels and providing a sense output corresponding to the capacitance variation, wherein a parasitic capacitance is accumulated as the touch input is applied;

generating a compensating capacitance to compensate for the parasitic capacitance and a compensation output corresponding to the compensating capacitance; and

converting the sense output into a noise compensated sense output using the compensation output.

14. The method of claim 13, wherein generating the compensation capacitance comprises:

applying outputs from a number of sense channels unaffected by the applied touch input to an inverting input of an amplifier, and applying a constant voltage to a non-inverting input of the amplifier;

applying a compensation feedback capacitance across the amplifier; and

turning ON and OFF a gain reset switch connected across the amplifier in parallel with the compensation feedback capacitance when the touch input is applied to generate the compensation output in a noise compensation capacitor.

15. The method of claim 13, further comprising:

directly connecting one of a number of sense channels affected by the applied touch input to an input of a signal conversion unit.

16. The method of claim 15, wherein the number of sense channels unaffected by the applied touch input comprises;

a first number of unaffected sense channels disposed in one direction from a number of sense channels affected by the applied touch input among; and

a second number of unaffected sense channels equal in number to the first number of unaffected sense channels and disposed in another direction from the number of sense channels affected by the applied touch input.

17. The method of claim 16, further comprising:

applying a constant voltage to at least one of the sense channels affected by the applied touch input.

18. The method of claim 17, wherein the at least one sense channel receiving the constant voltage is a sense channel adjacent to the one of the number of sense channels affected by the applied touch input and directly connected to the input of the signal conversion unit.

19. The method of claim 14, wherein the compensation feedback capacitor has a capacitance substantially the same as a parasitic capacitance between at least one of the sensing channels and a common electrode.

20. The method of claim 19, wherein the noise compensation capacitor has a capacitance substantially the same as a value obtained by dividing the capacitance of the compensation feedback capacitor by the number of the sense channels unaffected by the applied touch input.

21. The method of claim 14, wherein a multiplexer is used to apply the outputs of the number of sense channels unaffected by the applied touch input to the inverting input of the amplifier.

22. A touch controller receiving a sense output provided by sense channels sensing a capacitance variation associated with an applied touch input as detected by one or more sensing units connected to the sense channels, wherein a parasitic capacitance is accumulated as the touch input is applied, the touch controller comprising:

a noise compensation block configured to generate a compensation capacitance to compensate for the parasitic capacitance and provide a compensation output; and

a charge amplifier configured to receive the sense output and the compensation output and generate a noise compensated sense output.

23. A method compensating noise in a touch screen system, the method comprising:

sensing a capacitance variation associated with an applied touch input using sensing units connected to multiple sense channels and providing a sense output corresponding to the capacitance variation, wherein a parasitic capacitance is accumulated as the touch input is applied;

applying the sense output to one input of a charge amplifier functioning as a signal conversion unit;

generating a compensating capacitance to compensate for the parasitic capacitance and generating a compensation output corresponding to the compensating capacitance;

applying the compensation output the one input of the charge amplifier; and

applying a control voltage to another input of the charge amplifier to generate a noise compensated sense output.

24. The method of claim 23, further comprising generating the control voltage using an exciting pulse buffer.

25. The method of claim 24, wherein the compensation output is generated in relation to a number of the sense channels affected by the applied touch input, and a number of the sense channels unaffected by the applied touch input.

26. The method of claim 25, wherein generating the compensation capacitance comprises:

applying outputs from the number of sense channels unaffected by the applied touch input to an inverting input of an amplifier, and applying a constant voltage to a non-inverting input of the amplifier;

applying a compensation feedback capacitance across the amplifier; and

turning ON and OFF a gain reset switch connected across the amplifier in parallel with the compensation feedback capacitance when the touch input is applied to generate the compensation output in a noise compensation capacitor.

27. The method of claim 26, wherein the compensation feedback capacitor has a capacitance substantially the same as a parasitic capacitance between at least one of the sensing channels and a common electrode.

28. The method of claim 27, wherein the noise compensation capacitor has a capacitance substantially the same as a value obtained by dividing the capacitance of the compensation feedback capacitor by the number of the sense channels unaffected by the applied touch input.

29. The method of claim 26, wherein applying the sense output to the one input of the charge amplifier comprising directly connecting one of the number of sense channels affected by the applied touch input to the one input of the charge amplifier.

30. The method of claim 26, wherein the number of sense channels unaffected by the applied touch input comprises;

at least one of the number of unaffected sense channel disposed in one direction from the number of sense channels affected by the applied touch input among; and

at least another one of the number of unaffected sense channels disposed in another direction from the number of sense channels affected by the applied touch input.