Control unit, sensing device for a capacitive touch panel and method therefor

• US 8,976,122 B2
• Filed: 06/24/2009
• Issued: 03/10/2015
• Est. Priority Date: 06/24/2009
• Status: Active Grant

• Current Assignee: eGalax_eMPIA Technology Inc.
• Original Assignee: eGalax_eMPIA Technology Inc.
• Inventors: Chang, Chin-Fu, Lee, Cheng-Han
• Primary Examiner(s): HORNER, JONATHAN R
• Application Number:
  US12/457,867
• Publication Number:
  US 20100327881A1
• Time in Patent Office: 2,085 Days
• Field of Search: 345/173, 345/174, 324/658, 178/18.03, 178/18.06
• US Class Current: 345/173
• CPC Class Codes: G01B 2210/58 Wireless transmission of information between a sensor or probe and a control or evaluation unit
• CPC Class Codes: G01B 7/004 for measuring coordinates of points
• CPC Class Codes: G06F 3/0444 using a single conductive element covering the whole sensing surface, e.g. by sensing the electrical current flowing at the corners

Abstract

A noise reducing device for a capacitive touch panel and a method of reducing noise for a capacitive touch panel are disclosed to solve problems related to noise generated by a conventional filter circuit and an integrating circuit or external noise. In the invention, at least one switch circuit is used so that the conventional filter circuit and integrating circuit used in the prior are omitted. Signals output from a current measurement circuit are transmitting to a control unit to calculate the location of a touch point, reducing any noise.

Claims

1. A sensing device for a capacitive touch panel, the capacitive touch panel being rectangular and having a transparent substrate and a sensing layer on the transparent substrate, the sensing layer being transparent and electrically conductive, the capacitive touch panel further having a first X side, a second X side, a first Y side and a second Y side, the sensing device comprising:

a first X side switch circuit, respectively electrically connected to the first X side;

a second X side switch circuit, respectively electrically connected to the second X side;

a first Y side switch circuit, respectively electrically connected to the first Y side;

a second Y side switch circuit, respectively electrically connected to the second Y side;

a sensing source, providing a sensing signal to the first X side switch circuit, the second X side switch circuit, the first Y side switch circuit and the second Y side switch circuit; and

a control circuit, receiving the sensing signal generated by the sensing source, the control circuit further comprising;

a first current measurement circuit, electrically connected to the first X side switch circuit and the first Y side switch circuit; and

a second current measurement circuit, electrically connected to the second X side switch circuit and the second Y side switch circuit;

wherein the first current measurement circuit and the second current measurement circuit respectively receiving either a first X side current signal and a second X side current signal or a second X side current and a first Y side current signal simultaneously, wherein the first X side current signal is generated by the first X side switch circuit, the second X side current signal is generated by the second X side switch circuit, the first Y side current signal is generated by the first Y side switch circuit, and the second Y side current signal is generated by the second Y side switch circuit;

a control unit, comprising;

a first analogue/digital conversion circuit, electrically connected to the first current measurement circuit, converting a first X side analogue signal generated by the first X side current signal into a first X side digital signal, or converting a first Y side analogue signal generated by the first Y side current signal into a first Y side digital signal; and

a second analogue/digital conversion circuit, electrically connected to the second current measurement circuit, converting a second X side analogue signal generated by the second X side current signal into a second X side digital signal, or converting a second Y side analogue signal generated by the second Y side current signal into a second Y side digital signal; and

a location determining unit, electrically connected to the first analogue/digital conversion circuit and the second analogue/digital conversion circuit, and comprising;

a X coordinate determining device, receiving the first X side digital signal and the second X side digital signal, and determining the X coordinate of a touch point after calculations of the first X side digital signal and the second X side digital signal have been carried out; and

a Y coordinate determining device, receiving the first Y side digital signal and the second Y side digital signal, and determining the Y coordinate of the touch point after calculations of the first Y side digital signal and the second Y side digital signal have been carried out.

2. The sensing device for a capacitive touch panel of claim 1, wherein the control circuit further comprises:

a first sample and hold circuit, arranged between the first current measurement circuit and the first analogue/digital conversion circuit to receive the first X side current signal or the first Y side current signal for sampling; and

a second same and hold circuit, arranged between the second current measurement circuit and the second analogue/digital conversion circuit to receive the second X side current signal or the second Y side current signal for sampling.

3. The sensing device for a capacitive touch panel of claim 1, wherein the sensing source comprises a first sensing signal source and a second sensing signal source for generating a first sensing signal and a second sensing signal respectively, the X coordinate determining device connects the first X side switch circuit and the second X side switch circuit according to the first sensing signal, and the Y coordinate determining device connects the first Y side switch circuit and the second Y side switch circuit according to the second sensing signal.

4. The sensing device for a capacitive touch panel of claim 1, wherein the capacitive touch panel further comprises a rectangular work area and the touch point within the work area.