SNR ENHANCEMENT FOR DIFFERENTIAL INPUT DEVICE

• US 20110210924A1
• Filed: 02/26/2010
• Published: 09/01/2011
• Est. Priority Date: 02/26/2010
• Status: Active Grant

• Current Assignee: AU Optronics Corporation
• Original Assignee: AU Optronics Corporation
• Inventors: Cheng, Yung-Tse, Hsu, Yu-Min, Yang, Chia-Feng, Yang, Chun-Wei
• Granted Patent: US 8,432,374 B2
• Time in Patent Office: Days
• US Class Current: 345/173
• CPC Class Codes: G06F 3/04164 Connections between sensors and controllers, e.g. routing lines between electrodes and connection pads

Abstract

The present invention relates to a position detector and a touch sensing device of using same with SNR enhancement. In one embodiment, the position detector has (P+1) inputs, each input for receiving an input signal associated with a position, P being a positive integer, and P operational amplifiers, each operational amplifier having a non-inverting input and an inverting input, where the inverting input of the j-th operational amplifier is electrically connected to the non-inverting input of the (j+1)-th operational amplifier, and the non-inverting input and the inverting input of the j-th operational amplifier are electrically connected to the j-th input port and the (j+1)-th input port, respectively, j=1, 2, 3, . . . , (P−1).

Claims

1. A touch sensing device, comprising:

(a) a sensor matrix comprising (M+1) x-axis sensors spatially arranged in an x-axis direction, and (N+1) y-axis sensors spatially arranged crossing over the (M+1) x-axis sensors in a y-axis direction substantially perpendicular to the x-axis direction, M, N being a positive integer;

(b) an x-axis detector comprising;

(i) M operational amplifiers, the m-th operational amplifier having a non-inverting input electrically connected to the m-th x-axis sensor, an inverting input electrically connected to the (m+1)-th x-axis sensor, and an output, m=1, 2, 3, . . . , M;

(ii) M gain amplifiers, the m-th gain amplifier having an input electrically connected to the output of the m-th operational amplifier, and an output;

(iii) M reference capacitors, the m-th reference capacitor having a first terminal electrically connected to the output of the m-th gain amplifier, and a second terminal electrically connected to ground;

(iv) M switches, the m-th switch having a first terminal electrically connected to the output of the m-th gain amplifier, and a second terminal;

(v) an analog-to-digital converter (ADC) having an input electrically connected to the second terminal of each of the M switches, and an output, and

(vi) a subtraction circuit having an input electrically connected to the output of the ADC and an output for outputting touch sensing signals of the (M+1) x-axis sensors; and

(c) a y-axis detector comprising;

(i) N operational amplifiers, the n-th operational amplifier having a non-inverting input electrically connected to the n-th y-axis sensor, an inverting input electrically connected to the (n+1)-th y-axis sensor, and an output, n=1, 2, 3, . . . , N;

(ii) N gain amplifiers, the n-th gain amplifier having an input electrically connected to the output of the n-th operational amplifier, and an output;

(iii) N reference capacitors, the n-th reference capacitor having a first terminal electrically connected to the output of the n-th gain amplifier, and a second terminal electrically connected to ground;

(iv) N switches, the n-th switch having a first terminal electrically connected to the output of the n-th gain amplifier, and a second terminal;

(v) an analog-to-digital converter (ADC) having an input electrically connected to the second terminal of each of the N switches, and an output, and

(vi) a subtraction circuit having an input electrically connected to the output of the ADC and an output for outputting touch sensing signals of the (N+1) y-axis sensors.

2. The touch sensing device of claim 1, wherein when the sensor matrix is touched at a junction of the m-th x-axis sensor and the n-th y-axis sensor, a signal is generated responsively and transmitted to both of the inverting input of the (m−

1)-th operational amplifier and the non-inverting input of the m-th operational amplifier of the M operational amplifiers, and to both of the inverting input of the (n−

1)-th operational amplifier and the non-inverting input of the n-th operational amplifier of the N operational amplifiers, and wherein the (m−

1)-th operational amplifier and the m-th operational amplifier of the M operational amplifiers respectively output a first x-axis signal and a second x-axis signal that is out of phase of the first x-axis signal, and the (n−

1)-th operational amplifier and the n-th operational amplifier of the N operational amplifiers respectively output a first y-axis signal and a second y-axis signal that is out of phase of the first y-axis signal, responsive to the generated signal.

3. The touch sensing device of claim 2, wherein each of the M switches is configured to have an on-state and an off-state such that when the m-th x-axis sensor is touched, the (m−

1)-th switch and the m-th switch of the M switches are turned in the on-state, and the other switches of the M switches are turned in the off-state, and wherein each of the N switches is configured to have an on-state and an off-state such that when the n-th y-axis sensor is touched, the (n−

1)-th switch and the n-th switch of the N switches are turned in the on-state, and the other switches of the N switches are turned in the off-state.

4. The touch sensing device of claim 1, wherein

(a) each of the M operational amplifiers and the N operational amplifiers is identical to each other;

(b) each of the M gain amplifiers and the N gain amplifiers is identical to each other;

(c) each of the M reference capacitors and the N reference capacitors is identical to each other; and

(d) each of the M switches and the N switches is identical to each other.

5. A position detector usable for a touch sensing device, comprising:

(a) (P+1) input ports, each input for receiving an input signal associated with a position, P being a positive integer;

(b) P operational amplifiers, the j-th operational amplifier having a non-inverting input electrically connected to the j-th input port, an inverting input electrically connected to the (j+1)-th input port, and an output, j=1, 2, 3, . . . , P;

(c) P gain amplifiers, the j-th gain amplifier having an input electrically connected to the output of the j-th operational amplifier, and an output;

(d) P reference capacitors, the j-th reference capacitor having a first terminal electrically connected to the output of the j-th gain amplifier, and a second terminal electrically connected to ground;

(e) P switches, the j-th switch having a first terminal electrically connected to the output of the j-th gain amplifier, and a second terminal;

(f) an analog-to-digital converter (ADC) having an input electrically connected to the second terminal of each of the P switches, and an output, and

(g) a subtraction circuit having an input electrically connected to the output of the ADC and an output for outputting an output signal identified the position.

6. The position detector of claim 5, wherein when an input signal is input to the j-th input of the (P+1) inputs, it is transmitted to both of the inverting input of the (j−

1)-th operational amplifier and the non-inverting input of the j-th operational amplifier of the P operational amplifiers, and the (j−

1)-th operational amplifier and the j-th operational amplifier respectively output a first signal and a second signal that is out of phase of the first signal responsive to the input signal.

7. The position detector of claim 6, wherein each of the P switches is configured to have an on-state and an off-state such that when the input signal is input to the j-th input of the (P+1) inputs, the (j−

1)-th switch and the j-th switch of the P switches are turned in the on-state, and the other switches of the P switches are turned in the off-state.

8. The position detector of claim 5, wherein

(a) each of the P operational amplifiers is identical to each other;

(b) each of the P gain amplifiers is identical to each other;

(c) each of the P reference capacitors is identical to each other; and

(d) each of the P switches is identical to each other.

9. A touch sensing device, comprising at least one position detector of claim 5.

10. The touch sensing device of claim 9, further comprising a sensor matrix comprising a plurality of x-axis sensors spatially arranged in an x-axis direction, and a plurality of y-axis sensors spatially arranged crossing over the plurality of x-axis sensors in a y-axis direction substantially perpendicular to the x-axis direction.

11. The touch sensing device of claim 10, wherein each of the plurality of x-axis sensors is electrically connected to a corresponding input of the at least one position detector.

12. The touch sensing device of claim 10, wherein each of the plurality of y-axis sensors is electrically connected to a corresponding input of the at least one position detector.

13. A position detector usable for a touch sensing device, comprising:

(a) (P+1) inputs, each input for receiving an input signal associated with a position, P being a positive integer; and

(b) P operational amplifiers, each operational amplifier having a non-inverting input and an inverting input, wherein the inverting input of the j-th operational amplifier is electrically connected to the non-inverting input of the (j+1)-th operational amplifier, and wherein the non-inverting input and the inverting input of the j-th operational amplifier are electrically connected to the j-th input port and the (j+1)-th input port, respectively, j=1, 2, 3, . . . , (P−

1).

14. The position detector of claim 13, wherein when an input signal is input to the j-th input of the (P+1) inputs, it is transmitted to both of the inverting input of the (j−

1)-th operational amplifier and the non-inverting input of the j-th operational amplifier of the P operational amplifiers, and the (j−

1)-th operational amplifier and the j-th operational amplifier respectively output a first signal and a second signal that is out of phase of the first signal responsive to the input signal.

15. The position detector of claim 13, wherein each of the P operational amplifiers is identical to each other.

16. A touch sensing device, comprising at least one position detector of claim 13.