CAPACITANCE VARIATION DETECTION CIRCUIT, AND DISPLAY DEVICE

• US 20120086671A1
• Filed: 06/11/2010
• Published: 04/12/2012
• Est. Priority Date: 06/19/2009
• Status: Abandoned Application

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Brown, Christopher, Katoh, Hiromi, Tanaka, Kohei
• Application Number:
  US13/378,934
• Publication Number:
  US 20120086671A1
• Time in Patent Office: Days
• US Class Current: 345/174
• CPC Class Codes: G06F 3/0412 Digitisers structurally integrated in a display
• 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

Abstract

A capacitance variation detection circuit is provided in which detection sensitivity to variations in the liquid crystal capacitance can be improved. A capacitance variation detection circuit (10) includes a first variable capacitance portion (C_LC1) connected to the voltage supply line; a second variable capacitance portion (C_LC2) connected in series with the first variable capacitance portion (C_LC1); and a TFT (15) connected to the second variable capacitance portion (C_LC2) to be driven depending on the capacitance value of the first variable capacitance (C_LC1) and the capacitance value of the second variable capacitance (C_LC2), to output an electrical signal corresponding to these capacitance values.

Claims

1. A capacitance variation detection circuit for detecting a variation in capacitance in a cell, comprising:

a first variable capacitance portion connected to a voltage supply line;

a second variable capacitance portion connected in series with the first variable capacitance portion; and

a switching device connected to the second variable capacitance portion, the switching device being driven depending on a capacitance value of the first variable capacitance portion and a capacitance value of the second variable capacitance portion, to output an electrical signal corresponding to these capacitance values.

2. The capacitance variation detection circuit according to claim 1, further comprising:

a first substrate; and

a second substrate opposite the first substrate,

wherein;

the first substrate includes a floating electrode;

the second substrate includes a first electrode and a second electrode;

the first variable capacitance portion is formed between the first electrode and the floating electrode; and

the second variable capacitance portion is formed between the second electrode and the floating electrode.

3. A display device for detecting a contact location in a display screen based on a variation in capacitance between an electrode on a first substrate and an electrode on a second substrate, comprising:

a plurality of pixel circuits;

at least one capacitance variation detection circuit; and

an active matrix substrate,

wherein the capacitance variation detection circuit includes;

a first variable capacitance portion connected to a voltage supply line;

a second variable capacitance portion connected in series with the first variable capacitance portion; and

a switching device connected to the second variable capacitance portion, the switching device being driven depending on a capacitance value of the first variable capacitance portion and a capacitance value of the second variable capacitance portion, to output an electrical signal corresponding to these capacitance values.

4. The display device according to claim 3, wherein:

the first substrate includes a floating electrode;

the second substrate includes a first electrode and a second electrode;

the first variable capacitance portion is formed between the first electrode and the floating electrode; and

the second variable capacitance portion is formed between the second electrode and the floating electrode.

5. The display device according to claim 4, wherein:

on the first substrate is formed a projection that projects toward the second substrate;

the floating electrode is formed to cover the projection; and

the first electrode and the second electrode are provided opposite the projection.