Touch-detection system for display

• US 8,823,676 B2
• Filed: 01/21/2010
• Issued: 09/02/2014
• Est. Priority Date: 01/21/2009
• Status: Active Grant

• Current Assignee: Microchip Technology Germany GmbH (Microchip Technology Incorporated)
• Original Assignee: IDENT Technology AG (Microchip Technology Incorporated)
• Inventors: Fasshauer, Peter
• Primary Examiner(s): NGUYEN, KIMNHUNG T
• Application Number:
  US12/743,729
• Publication Number:
  US 20110267302A1
• Time in Patent Office: 1,685 Days
• Field of Search: 345173-179, 178 1801- 1804
• US Class Current: 345/174
• CPC Class Codes: G06F 3/044 by capacitive means
• 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
• CPC Class Codes: H03K 17/962 Capacitive touch switches
• CPC Class Codes: H03K 17/975 using a capacitive movable element

Abstract

A display screen is carried on a base by an elastically deformable support such that a touch shifts the screen relative to the base. A pair of juxtaposed electrodes form a capacitor, with one of the electrodes fixed to the screen and the other of the electrodes fixed to or formed by the base. A capacitance of the capacitor changes when the screen electrode moves relative to the base electrode. A circuit connected to the electrodes initiates an action on change of the capacitance.

Claims

1. An arrangement for detecting contact on a display, the arrangement comprising:

a screen panel,

an electrode forming part of a capacitor, and

a support carrying the screen panel and being configured such that it the support structure is compressed by a compression force exerted by contact with the screen panel, the electrode being coupled with the screen panel, the capacitor having a capacitance that changes when the support is compressed,

wherein the support comprises a base and an elastically deformable spacer arranged between the base and the screen panel such that a touch on the screen panel shifts the screen relative to the base;

and wherein the electrode is a first electrode of the capacitor, wherein the first electrode is fixed to the screen panel and a second electrode is fixed to or formed by the base, and

circuit means connected to the first and second electrodes for initiating an action on change of the capacitance.

2. The arrangement according to claim 1, wherein the screen panel is rectangular and the electrode is in a corner of the screen panel.

3. The arrangement according to claim 2, wherein the electrode is flat.

4. The arrangement according to claim 3, wherein the electrode is a metallic layer.

5. The arrangement according to claim 1 wherein a change of the capacitance of the capacitor is detected on the basis of a phase shift.

6. The arrangement according claim 1 wherein the electrode constitutes part of an LC network whose inductance is formed by a gyrator circuit.

7. The arrangement according to claim 1, wherein the screen panel is polygonal and has corners, the first electrode being in at least one of the corners.

8. The arrangement according to claim 7, wherein the first electrode extends annularly around an edge of the screen through all the corners, the second electrode being of generally the same shape as the first electrode.

9. The arrangement according to claim 1, wherein the first electrode is a metallic trace fixed to the screen panel.

10. The arrangement according to claim 1, wherein the circuit means detects a phase shift of the capacitance.