Capacitive touch sensor

• US 9,377,915 B2
• Filed: 03/20/2012
• Issued: 06/28/2016
• Est. Priority Date: 10/21/2011
• Status: Active Grant

• Current Assignee: Postech Academy-Industry Foundation
• Original Assignee: Postech Academy-Industry Foundation
• Inventors: Park, Hong June, Lee, Jae Seung, Yeo, Dong Hee, Lee, Sang Su, Cho, Joon Ho, Kwon, Hye Jung
• Primary Examiner(s): Boyd, Jonathan
• Assistant Examiner(s): AZONGHA, SARDIS F
• Application Number:
  US14/374,462
• Publication Number:
  US 20140368467A1
• Time in Patent Office: 1,561 Days
• US Class Current: 1/1
• CPC Class Codes: G06F 3/0412 Digitisers structurally integrated in a display
• 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

Provided is a capacitive touch sensor which includes a flat panel display for displaying an image and a touch sensor panel positioned on the flat panel display or embedded in the flat panel display. The capacitive touch sensor may include: a driving clock generator configured to generate a plurality of time-periodic output signals by using a gate driver signal of the flat panel display, and apply the generated time-periodic output signals to the touch sensor panel and a receiver circuit unit; a driver configured to generate a driving signal of the touch sensor panel using a part of the output signals of the driving clock generator; and the receiver circuit unit configured to process noise contained in a signal received from the touch sensor panel, using the output signals.

Claims

1. A capacitive touch sensor which includes a flat panel display for displaying an image and a touch sensor panel positioned on the flat panel display or embedded in the flat panel display, the capacitive touch sensor comprising:

a driving clock generator configured to generate a plurality of time-periodic output signals, and apply the time-periodic output signals of the driving clock generator to the touch sensor panel and a receiver circuit unit;

a driver configured to generate a driving signal of the touch sensor panel using a part of the time-periodic output signals of the driving clock generator; and

the receiver circuit unit configured to process noise contained in a signal received from the touch sensor panel, using the time-periodic output signals,

wherein one or more of the time-periodic output signals of the driving clock generator have a period corresponding to an even multiple of a period of self-generated noise of the flat panel display.

3. The capacitive touch sensor according to claim 1, wherein the receiver circuit unit is operated to reduce an influence of the noise in an output signal thereof, based on the characteristic that the noise has a time periodic property.

4. The capacitive touch sensor according to claim 1, wherein the noise is taken from a noise waveform of a common electrode, and the receiver circuit unit compensates for the noise.

5. The capacitive touch sensor according to claim 4, wherein the noise waveform comprises a voltage waveform between the common electrode and a common ground.

6. The capacitive touch sensor according to claim 5, wherein the common ground comprises a terminal at which a ground terminal of a driving circuit for driving the panel of the flat panel display and a ground terminal of the touch sensor circuit are shorted to each other.

7. The capacitive touch sensor according to claim 1, wherein one signal of the time-periodic output signals of the driving clock generator has a frequency corresponding to a positive integer multiple or (positive integer multiple+0.5) of a reciprocal of the period of the common electrode noise.

8. The capacitive touch sensor according to claim 1, wherein a noise waveform is transmitted to the receiver circuit unit through an RC network including resistance and capacitance.

9. The capacitive touch sensor according to claim 8, wherein the noise waveform is transmitted to an input terminal of an amplifier existing within the receiver circuit unit.

10. The capacitive touch sensor according to claim 8, wherein the RC network has a time constant larger than a reciprocal of the maximum frequency component of the noise waveform of the common electrode.

11. The capacitive touch sensor according to claim 1, wherein the time-periodic output signals of the driving clock generator of the capacitive touch sensor are generated using a gate driver clock signal of the flat panel display.

12. The capacitive touch sensor according to claim 1, wherein one of the time-periodic output signals of the driving clock generator comprises a sine wave or square wave.

19. The capacitive touch sensor according to claim 7, wherein

another signal of the time-periodic output signals of the driving clock generator performs the function of a chopper signal,

the chopper signal is constantly maintained at ‘

+1’

or ‘

−

1’

during a time period corresponding to a positive integer multiple of the self-generated noise period, and

the chopper signal comprises a time-periodic digital signal wherein the time period during which the digital signal is constantly maintained at ‘

+1’

is equal to the time period during which the digital signal is constantly maintained at ‘

−

1’

.

21. The capacitive touch sensor according to claim 1, wherein the receiver circuit unit is coupled to an output signal compensator for increasing an output dynamic range thereof.

22. The capacitive touch sensor according to claim 21, wherein the output signal compensator comprises:

a comparator;

a successive approximation register;

a digital-to-analog converter;

a voltage buffer; and

an inverter.

25. The capacitive touch sensor according to claim 4, wherein the common electrode terminal indicates a transparent electrode applied onto the entire surface of a glass plane positioned remote from a back light unit (BLU), between two glass planes forming a pixel element in a liquid crystal display based on vertical alignment.

26. The capacitive touch sensor according to claim 4, wherein the common electrode terminal indicates a common electrode pattern positioned with a thin film transistor on a glass plane positioned close to a BLU, between two glass planes forming a pixel element in a liquid crystal display based on in-plane switching.

27. The capacitive touch sensor according to claim 1, wherein the driving clock generator comprises a reference-less clock data recovery (CDR) circuit or a reference-less frequency-locked loop (FLL).

28. The capacitive touch sensor according to claim 1, wherein the driving clock generator comprises:

a level converter;

a reference-less CDR circuit or reference-less FLL;

a frequency divider;

a rising edge detector;

a multiplexer;

a counter;

a look-up table;

a digital-to-analog converter; and

a chopper circuit.

29. The capacitive touch sensor according to claim 1, wherein a touch operation is recognized even during an active time period in which the flat panel display drives an image signal and VBLANK and HBLANK time periods in which the flat panel display drives no image signal.

30. The capacitive touch sensor according to claim 1, wherein the receiver circuit unit comprises:

a charge amplifier configured to receive a signal from the touch sensor panel;

an analog multiplier configured to multiply an output of the charge amplifier by one of the time-periodic output signals of the driving clock generator; and

an integrator configured to integrate an output signal of the analog multiplier or a low-pass filter configured to pass only a low-frequency component of the output signal of the analog multiplier,

wherein one signal of the time-periodic output signals of the driving clock generator has a frequency corresponding to a positive integer multiple or (positive integer multiple+0.5) of a reciprocal of the period of the common electrode noise.

2. A capacitive touch sensor comprising:

a flat panel display;

a touch sensor panel coupled to the flat panel display;

a driving clock generator configured to generate a plurality of time-periodic output signals, using a clock signal for driving a gate of the flat panel display;

a driver configured to drive the touch sensor panel using a part of the time-periodic output signals of the driving clock generator; and

a receiver circuit unit configured to receive a signal from the touch sensor panel and reduce noise,

wherein one or more of the time-periodic output signals of the driving clock generator have a period corresponding to an even multiple of a period of self-generated noise of the flat panel display.

13. The capacitive touch sensor according to claim 2, wherein the receiver circuit unit comprises:

a charge amplifier configured to receive a signal from the touch sensor panel;

an analog multiplier configured to multiply an output of the charge amplifier by one of the time-periodic output signals of the driving clock generator;

a chopper circuit configured to multiply an output of the analog multiplier by another of the time-periodic output signals of the driving clock generator; and

an integrator configured to integrate an output signal of the chopper circuit or a low-pass filter configured to pass only a low-frequency component of the output signal of the chopper circuit.

14. The capacitive touch sensor according to claim 2, wherein the noise is reduced through two multiplications performed through the receiver circuit unit.

15. A capacitive touch sensor comprising:

a flat panel display;

a touch sensor panel coupled to the flat panel display;

a driving clock generator configured to generate a plurality of time-periodic output signals using a clock signal for driving a gate of the flat panel display;

a driver configured to drive the touch sensor panel using a part of the time-periodic output signals of the driving clock generator;

a receiver circuit unit configured to receive a signal from the touch sensor panel and reduce an influence of common electrode noise of the flat panel display; and

an AC coupling circuit configured to transmit the waveform of the common electrode noise to the receiver circuit unit,

wherein one or more of the time-periodic output signals of the driving clock generator have a period corresponding to an even multiple of a period of self-generated noise of the flat panel display.

17. The capacitive touch sensor according to claim 15, wherein the operation of reducing the influence of the noise within the receiver circuit unit is performed through a multiplication operation of signals inputted to the receiver circuit units and an integration operation or low-pass filtering operation following the multiplication operation.

18. The capacitive touch sensor according to claim 15, wherein the driver comprises a unit configured to perform a multiplication operation on signals.

20. The capacitive touch sensor according to claim 15, wherein one or more of the time-periodic output signals of the driving clock generator comprise a time-periodic digital signal wherein the time during which the signal level thereof is maintained at ‘

1’

is much shorter than the time during which the signal level thereof is maintained at ‘

0’

, and

an integrator or low-pass filter existing in the receiver circuit unit is reset at the time period in which the signal level is maintained at ‘

1’

, and performs an integration or low-pass filtering operation during the time period in which the signal level is maintained at ‘

0’

.

16. A capacitive touch sensor which includes a flat panel display for displaying an image and a touch sensor panel provided on or in the flat panel display, the capacitive touch sensor comprising:

a driving clock generator configured to generate a plurality of time-periodic output signals using a clock signal for driving a gate of the flat panel display;

a driver having multiple output terminals of which each is electrically coupled one-to-one to one of Y electrodes of the touch sensor panel; and

a receiver circuit unit having multiple input terminals of which each is electrically coupled one-to-one to one of X electrodes of the touch sensor panel,

wherein each of the multiple input terminals of the receiver circuit unit is electrically coupled one-to-one to an inverting input terminal of a charge amplifier existing in the receiver circuit unit,

wherein mutual capacitance is formed between an i-th Y electrode and a j-th X electrode of the touch sensor panel, and

wherein one or more of the time-periodic output signals of the driving clock generator have a period corresponding to an even multiple of a period of self-generated noise of the flat panel display.

23. A capacitive touch sensor which drives a touch sensor panel coupled to a flat panel display, the capacitive touch sensor comprising:

a driving clock generator configured to generate a plurality of time-periodic output signals using a clock signal for driving a gate of the flat panel display;

a driver configured to drive the touch sensor panel using a part of the time-periodic output signals of the driving clock generator;

a receiver circuit unit configured to receive a signal from the touch sensor panel and reduce an influence of common electrode noise of the flat panel display; and

an analog-to-digital converter (ADC) configured to receive an output signal of the receiver circuit unit,

wherein the driving clock generator, the driver, the receiver circuit unit, and the ADC are included in one integrated circuit chip, and

wherein one or more of the time-periodic output signals of the driving clock generator have a period corresponding to an even multiple of a period of self-generated noise of the flat panel display.

24. The capacitive touch sensor according to claim 23, wherein a power supply voltage of the integrated circuit chip is 4V or less,

the power supply voltage is not boosted in the integrated circuit chip,

the touch sensor panel is driven only through the integrated circuit chip, and

an analog signal received from the touch sensor panel is processed through the integrated circuit chip to output a digital signal.