TOUCH SENSING SYSTEM

• US 20150185913A1
• Filed: 09/05/2014
• Published: 07/02/2015
• Est. Priority Date: 12/31/2013
• Status: Active Grant

• Current Assignee: LG Display Co., Ltd.
• Original Assignee: LG Display Co., Ltd.
• Inventors: HAN, Sungsu, KANG, Seongkyu
• Granted Patent: US 9,465,497 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 3/0418 for error correction or compensation, e.g. based on parallax, calibration or alignment
• CPC Class Codes: G06F 3/04182 Filtering of noise external to the device and not generated by digitiser components
• 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 3/0443 using a single layer of sensing electrodes
• 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 system includes a plurality of touch sensors, sensing lines connected to the touch sensors, a touch sensing integrated circuit (IC) sensing a touch input using signals received through a plurality of receiving channels, a plurality of differential amplifiers which are formed between the sensing lines and the receiving channels of the touch sensing IC and amplify a difference between touch sensor signals received through adjacent sensing lines, and a multiplexer which connects the adjacent sensing lines to input terminals of each differential amplifier in a forward sensing mode and switches the adjacent sensing lines connected to the input terminals of each differential amplifier in a reverse sensing mode.

Claims

1. A touch sensing system, comprising:

a plurality of touch sensors;

sensing lines connected to the touch sensors;

a touch sensing integrated circuit (IC) configured to sense a touch input using signals received through a plurality of receiving channels;

a plurality of differential amplifiers formed between the sensing lines and the receiving channels of the touch sensing IC, each of the plurality of differential amplifiers configured to amplify a difference between touch sensor signals received through adjacent sensing lines; and

a multiplexer configured to connect the adjacent sensing lines to input terminals of each differential amplifier in a forward sensing mode and switch the adjacent sensing lines connected to the input terminals of each differential amplifier in a reverse sensing mode.

2. The touch sensing system of claim 1, wherein the touch sensing IC ignores an output signal having a low signal-to-noise ratio among output signals of the differential amplifiers received in the forward sensing mode and output signals of the differential amplifiers received in the reverse sensing mode and senses the touch input based on the remaining output signals.

3. The touch sensing system of claim 2, wherein the touch sensing IC converts an output of the differential amplifiers into touch raw data using an analog-to-digital converter (ADC),

wherein the touch sensing IC ignores one of an output signal of a first differential amplifier connected to a first receiving channel and an output signal of an Nth differential amplifier connected to an Nth receiving channel corresponding to a last receiving channel, where N is a positive integer equal to or greater than 2.

4. The touch sensing system of claim 3, wherein each differential amplifier includes an inverting input terminal, a non-inverting input terminal, an output terminal, and a capacitor connected between the inverting input terminal and the output terminal,

wherein an inverting input terminal and a non-inverting input terminal of each of other differential amplifiers except the Nth differential amplifier are connected to adjacent sensing lines, and one input terminal of the Nth differential amplifier is not connected to any sensing line.

5. The touch sensing system of claim 3, wherein in the forward sensing mode, an inverting input terminal of each of other differential amplifiers except the Nth differential amplifier is connected to an ith sensing line, and a non-inverting input terminal of each of the other differential amplifiers except the Nth differential amplifier is connected to an (i+1)th sensing line, where ‘

i’

is a positive integer,

wherein in the reverse sensing mode, the inverting input terminal of each of the other differential amplifiers except the Nth differential amplifier is connected to the (i+1)th sensing line, and the non-inverting input terminal of each of the other differential amplifiers except the Nth differential amplifier is connected to the ith sensing line,

wherein in the forward sensing mode, an inverting input terminal of the Nth differential amplifier is connected to an Nth sensing line, and a non-inverting input terminal of the Nth differential amplifier is not connected to any sensing line,

wherein in the reverse sensing mode, the inverting input terminal of the Nth differential amplifier is not connected to any sensing line, and the non-inverting input terminal of the Nth differential amplifier is connected to the Nth sensing line.

6. The touch sensing system of claim 4, wherein the touch sensing IC ignores an output of the Nth differential amplifier and calculates coordinates of a position of the touch input based on sensing results obtained by combining touch raw data obtained from an output of the other differential amplifiers as many as the number of receiving channels.

7. The touch sensing system of claim 2, wherein each differential amplifier includes an inverting input terminal, a non-inverting input terminal, an output terminal, and a capacitor connected between the inverting input terminal and the output terminal,

wherein an inverting input terminal and a non-inverting input terminal of each of other differential amplifiers except a first differential amplifier connected to a first receiving channel of the touch sensing IC among the differential amplifiers are connected to adjacent sensing lines, and one input terminal of the first differential amplifier is not connected to any sensing line.

8. The touch sensing system of claim 7, wherein in the forward sensing mode, the inverting input terminal of each of the other differential amplifiers except the first differential amplifier is connected to an ith sensing line, and the non-inverting input terminal of each of the other differential amplifiers except the first differential amplifier is connected to an (i+1)th sensing line, where ‘

i’

is a positive integer,

wherein in the reverse sensing mode, the inverting input terminal of each of the other differential amplifiers except the first differential amplifier is connected to the (i+1)th sensing line, and the non-inverting input terminal of each of the other differential amplifiers except the first differential amplifier is connected to the ith sensing line,

wherein in the forward sensing mode, an inverting input terminal of the first differential amplifier is not connected to any sensing line, and a non-inverting input terminal of the first differential amplifier is connected to a first sensing line,

wherein in the reverse sensing mode, the inverting input terminal of the first differential amplifier is connected to the first sensing line, and the non-inverting input terminal of the first differential amplifier is not connected to any sensing line.

9. The touch sensing system of claim 8, wherein the touch sensing IC ignores an output of the first differential amplifier and calculates coordinates of a position of the touch input based on sensing results obtained by combining touch raw data obtained from an output of the other differential amplifiers as many as the number of receiving channels.

10. The touch sensing system of claim 3, further comprising a second multiplexer configured to shift the sensing lines connected to the input terminals of the differential amplifiers.

11. The touch sensing system of claim 10, wherein in a first time of the forward sensing mode, an inverting input terminal of each of other differential amplifiers except the Nth differential amplifier is connected to an ith sensing line, and a non-inverting input terminal of each of the other differential amplifiers except the Nth differential amplifier is connected to an (i+1)th sensing line, where ‘

i’

is a positive integer,

wherein in a second time of the forward sensing mode, the inverting input terminal of each of the other differential amplifiers except the Nth differential amplifier is connected to the (i+1)th sensing line, and the non-inverting input terminal of each of the other differential amplifiers except the Nth differential amplifier is connected to an (i+2)th sensing line,

wherein in a first time of the reverse sensing mode, the inverting input terminal of each of the other differential amplifiers except the Nth differential amplifier is connected to the (i+1)th sensing line, and the non-inverting input terminal of each of the other differential amplifiers except the Nth differential amplifier is connected to the ith sensing line,

wherein in a second time of the reverse sensing mode, the inverting input terminal of each of the other differential amplifiers except the Nth differential amplifier is connected to the (i+2)th sensing line, and the non-inverting input terminal of each of the other differential amplifiers except the Nth differential amplifier is connected to the (i+1)th sensing line,

wherein in the first time of the forward sensing mode, an inverting input terminal of the Nth differential amplifier is connected to an (N−

1)th sensing line, and a non-inverting input terminal of the Nth differential amplifier is connected to an Nth sensing line,

wherein in the second time of the forward sensing mode, the inverting input terminal of the Nth differential amplifier is connected to the Nth sensing line, and the non-inverting input terminal of the Nth differential amplifier is not connected to any sensing line,

wherein in the first time of the reverse sensing mode, the inverting input terminal of the Nth differential amplifier is connected to the Nth sensing line, and the non-inverting input terminal of the Nth differential amplifier is connected to the (N−

1)th sensing line,

wherein in the second time of the reverse sensing mode, the inverting input terminal of the Nth differential amplifier is not connected to any sensing line, and the non-inverting input terminal of the Nth differential amplifier is connected to the Nth sensing line.

12. The touch sensing system of claim 11, wherein the touch sensing IC ignores an output of the Nth differential amplifier and calculates coordinates of a position of the touch input based on sensing results obtained by combining touch raw data obtained from an output of the other differential amplifiers as many as the number of receiving channels.

13. The touch sensing system of claim 10, wherein each differential amplifier includes an inverting input terminal, a non-inverting input terminal, an output terminal, and a capacitor connected between the inverting input terminal and the output terminal,

wherein an inverting input terminal and a non-inverting input terminal of each of other differential amplifiers except a first differential amplifier connected to a first receiving channel of the touch sensing IC among the differential amplifiers are connected to adjacent sensing lines, and one input terminal of the first differential amplifier is not connected to any sensing line.

14. The touch sensing system of claim 13, wherein in a first time of the forward sensing mode, the inverting input terminal of each of the other differential amplifiers except the first differential amplifier is connected to an ith sensing line, and the non-inverting input terminal of each of the other differential amplifiers except the first differential amplifier is connected to an (i+1)th sensing line, where ‘

i’

is a positive integer,

wherein in a second time of the forward sensing mode, the inverting input terminal of each of the other differential amplifiers except the first differential amplifier is connected to the (i+1)th sensing line, and the non-inverting input terminal of each of the other differential amplifiers except the first differential amplifier is connected to an (i+2)th sensing line,

wherein in a first time of the reverse sensing mode, the inverting input terminal of each of the other differential amplifiers except the first differential amplifier is connected to the (i+1)th sensing line, and the non-inverting input terminal of each of the other differential amplifiers except the first differential amplifier is connected to the ith sensing line,

wherein in a second time of the reverse sensing mode, the inverting input terminal of each of the other differential amplifiers except the first differential amplifier is connected to the (i+2)th sensing line, and the non-inverting input terminal of each of the other differential amplifiers except the first differential amplifier is connected to the (i+1)th sensing line,

wherein in the first time of the forward sensing mode, an inverting input terminal of the first differential amplifier is not connected to any sensing line, and a non-inverting input terminal of the first differential amplifier is connected to a first sensing line,

wherein in the second time of the forward sensing mode, the inverting input terminal of the first differential amplifier is connected to the first sensing line, and the non-inverting input terminal of the first differential amplifier is connected to a second sensing line,

wherein in the first time of the reverse sensing mode, the inverting input terminal of the first differential amplifier is connected to the first sensing line, and the non-inverting input terminal of the first differential amplifier is not connected to any sensing line,

wherein in the second time of the reverse sensing mode, the inverting input terminal of the first differential amplifier is connected to the second sensing line, and the non-inverting input terminal of the first differential amplifier is connected to the first sensing line.

15. The touch sensing system of claim 14, wherein the touch sensing IC ignores an output of the first differential amplifier and calculates coordinates of a position of the touch input based on sensing results obtained by combining touch raw data obtained from an output of the other differential amplifiers as many as the number of receiving channels.

16. The touch sensing system of claim 1, wherein one frame period is time-divided into a plurality of pixel driving periods and a plurality of touch sensing periods,

wherein in the touch sensing periods, the touch sensing IC is driven, receives the output of the differential amplifiers, and converts the output of the differential amplifiers into the touch raw data.

17. The touch sensing system of claim 1, wherein one frame period is time-divided into a plurality of pixel driving periods and a plurality of touch sensing periods,

wherein the touch sensing IC is driven and receives the output of the differential amplifiers in the touch sensing periods,

wherein the touch sensing IC converts the output of the differential amplifiers into the touch raw data in the pixel driving periods.