Control circuit and control method for capacitive touch panel

• US 8,884,909 B2
• Filed: 02/25/2009
• Issued: 11/11/2014
• Est. Priority Date: 10/31/2008
• Status: Expired due to Fees

• Current Assignee: Elan Microelectronics Corporation
• Original Assignee: Elan Microelectronics Corporation
• Inventors: Huang, Chun-Chung, Wang, Tsun-Min, Lin, Chun-Yu
• Primary Examiner(s): MARINELLI, PATRICK
• Application Number:
  US12/379,573
• Publication Number:
  US 20100110037A1
• Time in Patent Office: 2,085 Days
• Field of Search: 345156-184, 178 1801- 2004
• US Class Current: 345/174
• CPC Class Codes: G06F 3/0443 using a single layer of sensing electrodes
• CPC Class Codes: G06F 3/0445 using two or more layers of sensing electrodes, e.g. using two layers of electrodes separated by a dielectric layer
• 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 control circuit and a control method for a capacitive touch panel are provided. Therein, while a scanning signal charges and discharges each trace on the capacitive touch panel, a signal in phase with the scanning signal is provided to traces adjacent to the scanned trace or a ground layer under the scanned trace so as to lower parasitic capacitances between the scanned trace and the ground layer or other traces, thereby decreasing a base capacitance of the capacitive touch panel and enhancing a sensing result of the control circuit as well as providing a shielding effect and reducing noise interference so that the capacitive touch panel has improved performance.

Claims

1. A control circuit for a capacitive touch panel, the capacitive touch panel comprising a first trace and a second trace, the control circuit comprising:

a modulator for providing a first signal and a second signal in phase with the first signal;

a multiplexer coupled with the capacitive touch panel and the modulator for simultaneously applying the first signal to the first trace and the second signal to the second trace for generating a third signal corresponding to the first trace; and

a demodulator coupled with the multiplexer for demodulating the third signal on the first trace with a reference DC signal;

wherein the first trace and the second trace are substantially parallel and directly adjacent to each other;

wherein the demodulator comprises a first switch, a second switch, a third switch and a fourth switch, each having a first terminal and a second terminal,

wherein the first terminals of the first switch and the second switch are directly coupled to a first output terminal of the demodulator,

wherein the first terminals of the third switch and the fourth switch are directly coupled to a second output terminal of the demodulator,

wherein the second terminals of the first switch and the third switch directly receive the third signal, and

wherein the second terminals of the second switch and the fourth switch directly receive the reference DC signal.

2. The control circuit of claim 1, further comprising a voltage processing circuit for transforming a demodulation result of the demodulator into a change of capacitance.

3. A control circuit for a capacitive touch panel, the capacitive touch panel comprises a sensor layer and a ground layer, the control circuit comprising:

a modulator for providing a first signal and a second signal in phase with the first signal;

a multiplexer coupled with the capacitive touch panel and the modulator for simultaneously applying the first signal to the sensor layer and the second signal to the ground layer; and

a demodulator for demodulating with a reference DC signal;

wherein the demodulator comprises a first switch, a second switch, a third switch and a fourth switch, each having a first terminal and a second terminal,

wherein the first terminals of the first switch and the second switch are directly coupled to a first output terminal of the demodulator,

wherein the first terminals of the third switch and the fourth switch are directly coupled to a second output terminal of the demodulator,

wherein the second terminals of the first switch and the third switch directly receive a signal from the sensor layer, and

wherein the second terminals of the second switch and the fourth switch directly receive the reference DC signal.

4. A control method for a capacitive touch panel, the capacitive touch panel comprises a first trace and a second trace, the control method comprising the steps of:

providing a first signal so as to charge and discharge the first trace;

providing a second signal in phase with the first signal so as to charge and discharge the second trace;

simultaneously applying the first signal to the first trace and the second signal to the second trace; and

demodulating a third signal on the first trace with a reference DC signal;

wherein the first trace and the second trace are substantially parallel and directly adjacent to each other,

wherein demodulating the third signal is performed by a demodulator that comprises a first switch, a second switch, a third switch and a fourth switch, each having a first terminal and a second terminal,

wherein the first terminals of the first switch and the second switch are directly coupled to a first output terminal of the demodulator,

wherein the first terminals of the third switch and the fourth switch are directly coupled to a second output terminal of the demodulator,

wherein the second terminals of the first switch and the third switch directly receive the third signal, and

wherein the second terminals of the second switch and the fourth switch directly receive the reference DC signal.

5. The control method of claim 4, further comprising a step of transforming a result of demodulating the signal on the first trace with the reference signal into a change of capacitance.

6. A control method for a capacitive touch panel, the capacitive touch panel comprises a sensor layer and a ground layer, the control method comprising the steps of:

providing a first signal so as to charge and discharge the sensor layer;

providing a second signal in phase with the first signal to the ground layer;

simultaneously applying the first signal to the sensor layer and the second signal to the ground layer; and

demodulating a signal from the sensor layer with a reference DC signal;

wherein demodulating the signal from the sensor layer is performed by a demodulator that comprises a first switch, a second switch, a third switch and a fourth switch, each having a first terminal and a second terminal,

wherein the first terminals of the first switch and the second switch are directly coupled to a first output terminal of the demodulator,

wherein the first terminals of the third switch and the fourth switch are directly coupled to a second output terminal of the demodulator,

wherein the second terminals of the first switch and the third switch directly receive the signal from the sensor layer, and

wherein the second terminals of the second switch and the fourth switch directly receive the reference DC signal.

7. A capacitive touch panel module, comprising:

a capacitive touch panel having a first trace and a second trace;

a modulator for providing a first signal and a second signal in phase with the first signal;

a multiplexer coupled with the capacitive touch panel and the modulator for simultaneously applying the first signal to the first trace and the second signal to the second trace; and

a demodulator for demodulating a third signal on the first trace with a reference DC signal;

wherein the first trace and the second trace are substantially parallel and directly adjacent to each other,

wherein the demodulator comprises a first switch, a second switch, a third switch and a fourth switch, each having a first terminal and a second terminal,

wherein the first terminals of the first switch and the second switch are directly coupled to a first output terminal of the demodulator,

wherein the first terminals of the third switch and the fourth switch are directly coupled to a second output terminal of the demodulator,

wherein the second terminals of the first switch and the third switch directly receive the third signal, and

wherein the second terminals of the second switch and the fourth switch directly receive the reference DC signal.

8. The capacitive touch panel module of claim 7, wherein the first trace comprises a plurality of first sensors.

9. The capacitive touch panel module of claim 7, wherein the second trace comprises a plurality of second sensors.

10. The capacitive touch panel module of claim 7, wherein the second trace is adjacent to the first trace.

11. The capacitive touch panel module of claim 7, further comprising a voltage processing circuit for transforming a demodulation result of the demodulator into a change of capacitance.

12. A capacitive touch panel module, comprising:

a capacitive touch panel having a sensor layer and a ground layer;

a modulator for providing a first signal and a second signal in phase with the first signal;

a multiplexer coupled with the capacitive touch panel and the modulator for simultaneously applying the first signal to the sensor layer and the second signal to the ground layer; and

a demodulator for demodulating with a reference DC signal;

wherein the demodulator comprises a first switch, a second switch, a third switch and a fourth switch, each having a first terminal and a second terminal,

wherein the first terminals of the first switch and the second switch are directly coupled to a first output terminal of the demodulator,

wherein the first terminals of the third switch and the fourth switch are directly coupled to a second output terminal of the demodulator,

wherein the second terminals of the first switch and the third switch directly receive a signal from the sensor layer, and

wherein the second terminals of the second switch and the fourth switch directly receive the reference DC signal.

13. The capacitive touch panel module of claim 12, wherein the sensor layer comprises a plurality of sensors.