CAPACITIVE TOUCH SENSING DEVICE AND DETECTION METHOD THEREOF

• US 20140204046A1
• Filed: 01/22/2013
• Published: 07/24/2014
• Est. Priority Date: 01/22/2013
• Status: Abandoned Application

• Current Assignee: PixArt Imaging Incorporated
• Original Assignee: PixArt Imaging Incorporated
• Inventors: HSU, En-Feng, CHEN, Hsin-Chia, KAO, Ming-Tsan, CRANDALL, Ken
• Application Number:
  US13/746,883
• Publication Number:
  US 20140204046A1
• 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 3/04182 Filtering of noise external to the device and not generated by digitiser components
• 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

Abstract

There is provided a capacitive touch sensing device including a sensing element, a drive unit, a detection circuit and a processing unit. The sensing element has a first electrode and a second electrode configured to form a coupling capacitance therebetween. The drive unit is configured to input a drive signal to the sensing element. The detection circuit is configured to detect a detection signal coupled to the second electrode from the drive signal through the coupling capacitance and to modulate the detection signal respectively with two signals to generate a two-dimensional detection vector. The processing unit identifies a touch event according to the two-dimensional detection vector.

Claims

1. A capacitive touch sensing device, comprising:

a first electrode and a second electrode configured to form a coupling capacitance;

a drive unit configured to input a drive signal to the first electrode;

a detection circuit, coupled to the second electrode, configured to detect a detection signal coupled to the second electrode from the drive signal through the coupling capacitance and to modulate the detection signal respectively with two signals to generate a two-dimensional detection vector; and

a processing unit configured to calculate a norm of vector of the two-dimensional detection vector and to compare the norm of vector with a threshold so as to identify a touch event.

2. The capacitive touch sensing device as claimed in claim 1, wherein the two signals are continuous signals orthogonal to each other.

3. The capacitive touch sensing device as claimed in claim 1, wherein the two signals include a sine signal and a cosine signal.

4. The capacitive touch sensing device as claimed in claim 1, wherein the processing unit calculates the norm of vector using CORDIC.

5. The capacitive touch sensing device as claimed in claim 1, wherein the drive signal is a periodic signal.

6. The capacitive touch sensing device as claimed in claim 1, wherein the detection circuit further comprises at least one integrator and at least one analog-to-digital converter;

the integrator is configured to integrate the detection signal being modulated; and

the analog-to-digital converter is configured to digitize the detection signal being modulated and integrated so as to generate two components of the two-dimensional detection vector.

7. A detection method of a capacitive touch sensing device, the capacitive touch sensing device comprising a sensing element, which comprises a first electrode and a second electrode configured to form a coupling capacitance, the detection method comprising:

inputting a drive signal to the first electrode of the sensing element;

modulating a detection signal coupled to the second electrode from the drive signal through the coupling capacitance respectively with two signals so as to generate a pair of modulated detection signals; and

calculating a scale of the pair of the modulated detection signals to accordingly identify a touch event.

8. The detection method as claimed in claim 7, wherein the scale of the pair of the modulated detection signals is a norm of vector of a two-dimensional vector formed by the pair of the modulated detection signals.

9. The detection method as claimed in claim 8, wherein the norm of vector is calculated by using CORDIC.

10. The detection method as claimed in claim 7, wherein the two signals include a sine signal and a cosine signal.

11. The detection method as claimed in claim 7, wherein the two signals are continuous signals orthogonal to each other.

12. The detection method as claimed in claim 7, wherein the drive signal is a periodic signal.

13. The detection method as claimed in claim 7, wherein before the step of calculating a scale of the pair of the modulated detection signals further comprises:

integrating and digitizing the pair of the modulated detection signals.

14. A capacitive touch sensing device, comprising:

a capacitive sensing matrix comprising a plurality of sensing elements arranged in matrix and each of the sensing elements comprising a first electrode and a second electrode configured to form a coupling capacitance;

a plurality of drive units, coupled to the first electrode of the sensing elements, configured to sequentially output a drive signal to the first electrode;

a detection circuit, coupled to the second electrode of the sensing elements, configured to sequentially detect a detection signal coupled to the second electrode from the drive signal through the coupling capacitance and to modulate the detection signal respectively with two signals so as to generate a pair of modulated detection signals; and

a processing unit configured to identify a touch event and a touch position according to the pair of the modulated detection signals.

15. The capacitive touch sensing device as claimed in claim 14, wherein the two signals are continuous signals orthogonal to each other.

16. The capacitive touch sensing device as claimed in claim 14, wherein the two signals include a sine signal and a cosine signal.

17. The capacitive touch sensing device as claimed in claim 14, wherein the drive signal is a periodic signal.

18. The capacitive touch sensing device as claimed in claim 14, wherein the processing unit calculates a norm of vector of a two-dimensional detection vector formed by the pair of the modulated detection signals and identifies the touch event occurs when the norm of vector is smaller than or larger than a threshold.

19. The capacitive touch sensing device as claimed in claim 18, wherein the processing unit calculates the norm of vector using CORDIC.

20. The capacitive touch sensing device as claimed in claim 14, wherein the processing unit identifies a position of at least one of the sensing elements occurring the touch event within a scan period as the touch position.