Touch sensing apparatus and method

• US 10,152,179 B2
• Filed: 11/21/2013
• Issued: 12/11/2018
• Est. Priority Date: 12/26/2012
• Status: Active Grant

• Current Assignee: LG Display Co., Ltd.
• Original Assignee: LG Display Co., Ltd.
• Inventors: Park, Dong-Jo
• Primary Examiner(s): Mehmood, Jennifer
• Assistant Examiner(s): Gupta, Parul H
• Application Number:
  US14/086,872
• Publication Number:
  US 20140176489A1
• Time in Patent Office: 1,846 Days
• Field of Search: None
• CPC Class Codes: G06F 3/0412 Digitisers structurally integrated in a display
• 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 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes

Abstract

A touch sensing apparatus and method for correctly sensing a touch signal by removing an offset per touch node via differential sensing are discussed. The touch sensing method includes sensing a first sensing value including an offset component per touch node using a read out signal of a touch sensor, the touch sensor not being supplied with a driving pulse, in a first sensing period; sensing a second sensing value including the offset component of the touch node and a mutual capacitive component based on whether a touch is performed, using a read out signal of the touch sensor, the touch sensor being supplied with a driving pulse, in a second sensing period; and acquiring touch data from which the offset component is removed via a differential operation of the second sensing value and the first sensing value.

Claims

1. A touch sensing method, the method comprising:

acquiring, via a touch controller, a first sensing value representing only noise by sensing an offset component of each touch node using a first read out signal from a corresponding read out line of a touch sensor before a voltage of a driving pulse from the touch controller is supplied to a corresponding scan line of the touch sensor, in a first sensing period;

acquiring, via the touch controller, a second sensing value by sensing the offset component of each of the touch node and a capacitance change based on whether a touch is performed, using a second read out signal from the corresponding read out line of the touch sensor, in a second sensing period in which the driving pulse from the touch controller is supplied to the touch sensor; and

acquiring, via the touch controller, a touch data corresponding to the capacitance change from which the offset component is removed via a differential operation of the second sensing value and the first sensing value,

wherein;

a readout circuit of one channel connected with the corresponding read out line includes an analog sensing unit, a sample and hold unit, an analog-to-digital converter (ADC), and a differential operator,

during the first sensing period, the analog sensing unit acquires the first sensing value from the corresponding read out line and supplies the first sensing value to the sample and hold unit, the sample and hold unit samples and holds the first sensing value and supplies the first sensing value to the ADC, the ADC converts the first sensing value into the first digital sensing data, and the differential operator stores the first digital sensing data supplied from the ADC, and

during the second sensing period, the analog sensing unit acquires the second sensing value from the corresponding read out line, and supplies the second sensing value to the sample and hold unit, the sample and hold unit samples and holds the second sensing value and supplies the second sensing value to the ADC, the ADC converts the second sensing value into the second digital sensing data, and the differential operator performs a subtraction operation of the second digital sensing data supplied from the ADC and the first digital sensing data to remove noise sensed on the corresponding read out line before the driving pulse is supplied and acquire the touch data corresponding to the capacitance change, and

wherein the first and second sensing periods are immediately adjacent periods.

2. The method of claim 1, further comprising:

integrating the first read out signal to output a first analog sensing signal, holding and sampling the first analog sensing signal to output the sampled and held first analog sensing signal, converting the first analog sensing signal into the first digital sensing data to output the first digital sensing data, and inputting the first digital sensing data and storing the first digital sensing data in the buffer, in the first sensing period; and

integrating the second read out signal to output a second analog sensing signal, holding and sampling the second analog sensing signal to output the sampled and held second analog sensing signal, converting the second analog sensing signal into the second digital sensing data to output the second digital sensing data, and performing subtraction on the second digital sensing data and the first digital sensing data from the buffer to acquire the touch data, in the second sensing period.

7. The touch sensing method of claim 1, wherein a process sensing the first sensing value from the first read out signal is the same as a process sensing the second sensing value from the second read out signal.

3. A touch sensing apparatus comprising:

a touch sensor for outputting a read out signal indicating capacitance change based on a presence of touch; and

a touch controller for;

acquiring a first sensing value representing only noise by sensing an offset component of each touch node using a first read out signal from a corresponding read out line of the touch sensor before a voltage of a driving pulse from the touch controller is supplied to a corresponding scan line of the touch sensor, in a first sensing period,

acquiring a second sensing value by sensing the offset component of each of the touch node and a capacitance change based on whether a touch is performed, using a second read out signal from the corresponding read out line of the touch sensor, in a second sensing period in which the driving pulse from the touch controller is supplied to the touch sensor, and

acquiring a touch data corresponding to the capacitance change from which the offset component is removed via a differential operation of the second sensing value and the first sensing value,

wherein;

a readout circuit of one channel connected with the corresponding read out line includes an analog sensing unit, a sample and hold unit, an analog-to-digital converter (ADC), and a differential operator,

during the first sensing period, the analog sensing unit acquires the first sensing value from the corresponding read out line and supplies the first sensing value to the sample and hold unit, the sample and hold unit samples and holds the first sensing value and supplies the first sensing value to the ADC, the ADC converts the first sensing value into the first digital sensing data, and the differential operator stores the first digital sensing data supplied from the ADC, and

during the second sensing period, the analog sensing unit acquires the second sensing value from the corresponding read out line, and supplies the second sensing value to the sample and hold unit, the sample and hold unit samples and holds the second sensing value and supplies the second sensing value to the ADC, the ADC converts the second sensing value into the second digital sensing data, and the differential operator performs a subtraction operation of the second digital sensing data supplied from the ADC and the first digital sensing data to remove noise sensed on the corresponding read out line before the driving pulse is supplied and acquire the touch data corresponding to the capacitance change,

wherein the first and second sensing periods are immediately adjacent periods.

4. The touch sensing apparatus of claim 3, wherein the touch controller includes:

a control signal generator for generating and outputting a plurality of control signals;

a driving pulse generator for generating and outputting the driving pulse;

a touch sensor driver for not supplying the driving pulse from the driving pulse generator to a corresponding scan line of the touch sensor in the first sensing period and supplying the driving pulse to the corresponding scan line in the second sensing period in response to a control signal from the control signal generator; and

the read out circuit for sensing the first sensing value using the first read out signal from the corresponding read out line of the touch sensor in the first sensing period and sensing the second sensing value using the second read out signal from the corresponding read out line in the second sensing period in response to the control signal from the control signal generator, and then, acquiring and outputting the touch data via the differential operation of the first and second sensing values.

5. The touch sensing apparatus of claim 4, wherein the read out circuit includes:

the analog sensing unit for integrating the first read out signal to output a first analog sensing signal in the first sensing period, and integrating the second read out signal to output a second analog sensing signal in the second sensing period;

the sample and hold unit for holding and sampling the first analog sensing signal to output the sampled and held first analog sensing signal in the first sensing period, and holding and sampling the second analog sensing signal to output the sampled and held second analog sensing signal in the second sensing period;

the ADC for converting the first analog sensing signal from the sample and hold unit into the first digital sensing data to output the first digital sensing data in the first sensing period, and converting the second analog sensing signal from the sample and hold unit into the second digital sensing data to output the second digital sensing data in the second sensing period; and

the differential operator for inputting the first digital sensing data and storing the first digital sensing data in the buffer in the first sensing period, and performing subtraction on the second digital sensing data and the first digital sensing data from the buffer in the second sensing period to acquire the touch data.

6. The touch sensing apparatus of claim 3, wherein:

the touch sensor includes scan lines and read out lines intersecting each other,

a period allocated for each of the scan lines includes consecutive first and second sensing periods, and

the touch controller senses first sensing values by read out channel using first read out signals respectively outputting from the read out lines in the first sensing period, senses second sensing values by read out channel using second read out signals respectively outputting from the read out lines in the second sensing period, and acquiring touch data per touch node via the differential operation of each of the second sensing values and each of the first sensing values.

8. The touch sensing apparatus of claim 3, wherein in the touch controller, a process sensing the first sensing value from the first read out signal is the same as a process sensing the second sensing value from the second read out signal.

9. The touch sensing apparatus of claim 5, wherein the analog sensing unit comprises:

a first amplifier connected with the corresponding read out line,

first and second switches that are connected in series to each other between the corresponding read output line and an input terminal of the first amplifier,

a first capacitor between a ground and a node between the first and second switches, and

a third switch and a second capacitor that are connected in parallel to each other between the input terminal and an output terminal of the first amplifier.

10. The touch sensing apparatus of claim 9, further comprising a sample and hold unit including:

a second amplifier connected with an output terminal of the analog sensing unit,

a fourth switch and a third capacitor that are connected in series to each other between the output terminal of the analog sensing unit and an input terminal of the second amplifier,

a fifth switch connected between the fourth switch and an output terminal of the second amplifier, and

a sixth switch connected between the input terminal and the output terminal of the second amplifier.

11. The touch sensing apparatus of claim 10, further comprising:

an analog-to-digital converter, wherein the analog-to-digital converter further comprises a seventh switch connected to an input terminal the digital-to-analog converter and an output terminal of the sample and hold unit, and

a differential operator comprising;

a buffer connected with an output terminal of the analog-to-digital converter,

an eighth switch connected between the output terminal of the analog-to-digital converter and the buffer, and

a subtracter connected between the output terminal of the analog-to-digital converter and an output terminal of the buffer.

12. The touch sensing apparatus of claim 11, wherein the analog sensing unit is configured to:

short the input and output terminals of the first amplifier via the third switch responding to a reset signal to reset the first amplifier,

store a corresponding read out signal from the corresponding read out line in first capacitor via the first switch responding to a first control signal, and

integrate the stored signal via the second switch responding to a second control signal and the first amplifier to output a corresponding sensing signal proportional to a capacitance ratio of the first and second capacitor.

13. The touch sensing apparatus of claim 12, wherein the sample and hold unit is configured to:

hold the corresponding sensing signal in the third capacitor via the four switch responding to a third control signal and the fifth switch responding to the second control signal, and

output the corresponding sensing signal via the second amplifier and the sixth switch responding to the first control signal.

14. The touch sensing apparatus of claim 13, wherein:

the analog-to-digital converter is configured to convert the sensing signal, received via the seventh switch responding to a fourth control signal from the sample and hole unit, to a corresponding sensing data as the first or second sensing value, and

the differential operator is configured to;

store the first sensing value in the buffer via the eighth switch responding to a fifth control signal in part of the first sensing period, and

perform subtraction on the second sensing data from the analog-to-digital converter and the first sensing data from the buffer via the subtracter in part of the second sensing period to output the subtraction result as the touch data.