Method and apparatus compensating noise in touch panel

• US 8,736,573 B2
• Filed: 01/25/2011
• Issued: 05/27/2014
• Est. Priority Date: 02/05/2010
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Choi, Yoon-kyung, Byun, San-ho
• Primary Examiner(s): Shalwala, Bipin
• Assistant Examiner(s): XIE, KWIN
• Application Number:
  US13/013,308
• Publication Number:
  US 20110193817A1
• Time in Patent Office: 1,218 Days
• Field of Search: None
• 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 a touch input applied to a group of affected sense channels among the sense channels, wherein a parasitic capacitance is accumulated as the touch input is applied to the group of affected sense channels, and the sense channels further include unaffected sense channels to which the touch input is not applied; and

a touch controller receiving the sense output and comprising;

a noise compensation block that receives a compensating input from a channel multiplexer connecting unaffected channels, and is configured to generate a compensation capacitance to compensate for the parasitic capacitance in response to the compensating input to provide a compensation output; and

a signal conversion unit that receives the compensation output from the noise compensation block and directly receives a portion of the sense output from one of the group of affected sense channels while the compensating input is received by the noise compensation block, and is configured to generate a noise compensated sense output in response to the portion of the sense output and the compensation output.

2. The apparatus of claim 1, wherein the noise compensation block comprises:

an amplifier having a gain reset switch disposed between an inverting input and an output of the amplifier, wherein the compensating input is applied to the inverting input;

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 a first input of the signal conversion unit, wherein the first input of the signal conversion unit directly receives the portion of the sense output together with the compensation output.

3. The apparatus of claim 2, wherein the unaffected sense channels include;

first unaffected sense channels disposed in one direction from the group of affected sense channels; and

second unaffected sense channels disposed in another direction from the group of affected sense channels.

4. The apparatus of claim 3, wherein while the compensating input is received by the noise compensation block and while the portion of the sense output is received by the signal conversion unit, a constant voltage is applied to at least one of the group of affected sense channels.

5. The apparatus of claim 4, wherein the at least one of the group of affected sense channels receiving the constant voltage is a sense channel directly adjacent to the one of the group of affected sense channels providing the portion of the sense output directly to the first input of the signal conversion unit.

6. The apparatus of claim 2, wherein a 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.

7. The apparatus of claim 6, wherein a 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 the unaffected sense channels.

8. The apparatus of claim 2, wherein the channel multiplexer connects the unaffected sense channels to the inverting input of the amplifier.

9. The apparatus of claim 2, wherein the touch screen panel and touch controller are integrated into a single body.

10. The apparatus of claim 9, wherein the touch screen panel is an ON-cell type touch panel.

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

12. A method compensating noise in a touch screen system including a touch screen panel and a signal processing unit, wherein the touch screen panel comprises sense channels providing a sense output in response to a touch input, the method comprising:

sensing a capacitance variation associated with the touch input applied to a group of affected sense channel among the sense channels, wherein a parasitic capacitance is accumulated as the touch input is applied to the group of affected sense channels;

generating in a noise compensation block a compensating capacitance to compensate for the parasitic capacitance in response to a compensating input received from a channel multiplexer connecting unaffected sense channels among the sense channels, and generating a compensation output corresponding in response to the compensating capacitance; and

converting a portion of the sense output directly applied to a signal conversion unit from one of the group of affected sense channels while the compensating input is received from the channel multiplexer into a noise compensated sense output in response to the compensation output.

13. The method of claim 12, wherein generating the compensation capacitance comprises:

while receiving the compensating input from the channel multiplexer at an inverting input of an amplifier in the noise compensation block, applying a constant voltage to a non-inverting input of the amplifier;

applying a compensation feedback capacitance across the amplifier;

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 the group of affected sense channels to generate a noise compensation block output; and

passing the noise compensation block output through a noise compensation capacitor disposed between the output of the amplifier and a first input of the signal conversion unit to generate the compensation output, wherein the first input of the signal conversion unit directly receives the portion of the sense output together with the compensation output.

14. The method of claim 13, wherein the group of unaffected sense channels comprises;

first unaffected sense channels disposed in one direction from the group of affected sense channels; and

second unaffected sense channels disposed in another direction from the group of unaffected sense channels.

15. The method of claim 14, further comprising:

applying a constant voltage to at least one of the group of affected sense channels while the compensating input is received from the channel multiplexer at the inverting input of an amplifier in the noise compensation block.

16. The method of claim 15, wherein the at least one of the group of affected sense channels receiving the constant voltage is a sense channel directly adjacent to the one of the group of affected sense channels applying the portion of the sense output directly to the signal conversion unit.

17. The method of claim 13, wherein the compensation feedback capacitance is substantially the same as a parasitic capacitance between at least one of the sensing channels and a common electrode.

18. The method of claim 17, wherein the noise compensation capacitor has a capacitance substantially the same as a value obtained by dividing the compensation feedback capacitance by a number of the unaffected sense channels.

19. The method of claim 13, wherein the channel multiplexer connects the unaffected sense channels to the inverting input of the amplifier.

20. 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 that receives a compensating input from a first group of channels among the sense channels, and is configured to generate a compensation capacitance to compensate for the parasitic capacitance in response to the compensating input and provide a compensation output; and

a charge amplifier configured to receive the compensation output from the noise compensation block and directly receive a portion of the sense output from one of the second group of channels among the sense channels and generate a noise compensated sense output in response to the portion of the sense output and the compensation output.