Control circuit and control method for touch panel

• US 8,860,673 B2
• Filed: 07/07/2010
• Issued: 10/14/2014
• Est. Priority Date: 07/07/2009
• Status: Active Grant

• Current Assignee: ROHM Co., Ltd.
• Original Assignee: ROHM Co., Ltd.
• Inventors: Tada, Naoki, Abe, Shinichi, Saito, Koichi, Hisa, Kazunori
• Primary Examiner(s): Snyder, Adam J
• Assistant Examiner(s): RABINDRANATH, ROY P
• Application Number:
  US12/831,610
• Publication Number:
  US 20110025642A1
• Time in Patent Office: 1,560 Days
• Field of Search: 345/173, 345/174
• US Class Current: 345/173
• CPC Class Codes: G06F 2203/04104 Multi-touch detection in digitiser, i.e. details about the simultaneous detection of a plurality of touching locations, e.g. multiple fingers or pen and finger
• CPC Class Codes: G06F 3/0416 Control or interface arrangements specially adapted for digitisers
• CPC Class Codes: G06F 3/045 using resistive elements, e.g. a single continuous surface or two parallel surfaces put in contact

Abstract

A first resistive film is arranged such that one edge thereof is connected to a first terminal, and an edge that is opposite to the aforementioned edge is connected to a second terminal. A second resistive film is arranged with a gap between it and the first resistive film such that one edge thereof is connected to a third terminal. A voltage generating unit applies a predetermined first bias voltage and a predetermined second bias voltage to the first terminal and the second terminal, respectively. A voltage detection unit detects a panel voltage that occurs at the third terminal. A current detection unit detects a panel current that flows through a path including the first terminal, the first resistive film, and the second terminal. A computation unit determines the coordinates touched by the user, based upon the values of the panel voltage and the panel current.

Claims

1. A control method, for a touch panel comprising a first terminal, a second terminal, a third terminal, a first resistive film arranged such that one edge thereof is connected to the first terminal and an edge that is opposite to the aforementioned one edge is connected to the second terminal, and a second resistive film arranged with a gap between it and the first resistive film such that one edge thereof is connected to the third terminal, the control method comprising:

applying a predetermined first bias voltage and a predetermined second bias voltage to the first and second terminals, respectively;

detecting a panel voltage that occurs at the third terminal;

detecting a panel current that flows through a path including the first terminal, the first resistive film, and the second terminal; and

determining coordinates touched by a user, based upon the panel voltage and the panel current, wherein, when the user touches two points, the panel current has a value according to an interval between the two points, and there is a one-to-one correspondence between the panel current and the interval between the two points,

and wherein the control method further comprises

determining the interval between the two points based upon the value of the panel current by referring to the one-to-one correspondence when the user touches two points,

wherein the judgment processing comprises;

determining the midpoint between the two coordinates based upon the panel voltage; and

determining the coordinates of one of the two points by adding a value that corresponds to the interval between the two coordinates to the midpoint coordinates, and determining the coordinates of the other of the two points by subtracting, from the midpoint coordinates, a value that corresponds to the interval between the two coordinates.

2. A method according to claim 1, wherein, when the value of the panel current is greater than a predetermined value, judgment is made that the user touched multiple points.

3. A method according to claim 1, wherein the interval between the two coordinates is determined to be a value which increases according to an increase in the panel current.

4. A method according to claim 1, wherein the interval between the two coordinates is determined based upon the difference between the panel current measured when the user does not touch the panel and the panel current measured when the user touches the panel.

5. A control circuit configured to control a touch panel comprising a first terminal, a second terminal, a third terminal, a first resistive film arranged such that one edge thereof is connected to the first terminal and an edge that is opposite to the aforementioned one edge is connected to the second terminal, and a second resistive film arranged with a gap between it and the first resistive film such that one edge thereof is connected to the third terminal, the control circuit comprising:

a voltage generating unit configured to apply a predetermined first bias voltage and a predetermined second bias voltage to the first and second terminals, respectively;

a voltage detection unit configured to detect a panel voltage that occurs at the third terminal;

a current detection unit configured to detect a panel current that flows through a path including the first terminal, the first resistive film, and the second terminal; and

a coordinate determination unit configured to determine the coordinates touched by the user, based upon the panel voltage and the panel current thus detected,

when the user touches two points, the panel current has a value according to an interval between the two points, and there is a one-to-one correspondence between the panel current and the interval between the two points,

and the interval between the two points is determined based upon the value of the panel current by referring to the one-to-one correspondence,

wherein the coordinate determination unit determines the midpoint between the aforementioned two coordinates, based upon the panel voltage,

and wherein the coordinates of one of the aforementioned two points are determined by adding a value that corresponds to the interval between the two coordinates to the midpoint coordinates,

and wherein the coordinates of the other of the two points are determined by subtracting, from the midpoint coordinates, a value that corresponds to the interval between the two coordinates.

6. A control circuit according to claim 5, wherein, when the value of the panel current is greater than a predetermined value, the coordinate determination unit judges that the user touched multiple points.

7. A control circuit according to claim 5, wherein the interval between the two coordinates is determined based upon the difference between the panel current measured when the user does not touch the panel and the panel current measured when the user touches the panel.

8. A control circuit configured to control a touch panel comprising a first terminal, a second terminal, a third terminal, a first resistive film arranged such that one edge thereof is connected to the first terminal and an edge that is opposite to the aforementioned one edge is connected to the second terminal and a second resistive film arranged with a gap between it and the first resistive film such that one edge thereof is connected to the third terminal, the control circuit comprising:

a voltage generating unit configured to apply a predetermined first bias voltage and a predetermined second bias voltage to the first and second terminals, respectively;

a voltage detection unit configured to detect a panel voltage that occurs at the third terminal;

a current detection unit configured to detect a panel current that flows through a path including the first terminal, the first resistive film, and the second terminal; and

a coordinate determination unit configured to determine the coordinates touched by the user, based upon the panel voltage and the panel current thus detected,

when the user touches two points, the panel current has a value according to an interval between the two points, and there is a one-to-one correspondence between the panel current and the interval between the two points,

and the interval between the two points is determined based upon the value of the panel current by referring to the one-to-one correspondence,

wherein the current detection unit comprises;

a detection resistor arranged as an extension to a path that includes the first terminal, the first resistive film, and the second terminal; and

a bypass switch arranged in parallel with the detection resistor,

wherein, when the panel voltage is to be detected by means of the voltage detection unit, the bypass switch is turned on,

and wherein, when the panel current is to be detected by means of the current detection unit, the bypass switch is turned off, and

wherein a value that corresponds to a voltage drop that occurs at the detection resistor is output as a value which represents the panel current.

9. The control circuit according to claim 8, wherein, when the value of the panel current is greater than a predetermined value, the coordinate determination unit judges that the user touched multiple points.

10. The control circuit according to claim 8, wherein the interval between the two coordinates is determined based upon the difference between the panel current measured when the user does not touch the panel and the panel current measured when the user touches the panel.

11. A touch panel input apparatus comprising:

a touch panel comprising a first terminal, a second terminal, a third terminal, a first resistive film arranged such that one edge thereof is connected to the first terminal and an edge that is opposite to the aforementioned one edge is connected to the second terminal, and a second resistive film arranged with a gap between it and the first resistive film such that one edge thereof is connected to the third terminal; and

a control circuit configured to control the touch panel, wherein

the control circuit comprises;

a voltage generating unit configured to apply a predetermined first bias voltage and a predetermined second bias voltage to the first and second terminals, respectively;

a voltage detection unit configured to detect a panel voltage that occurs at the third terminal;

a current detection unit configured to detect a panel current that flows through a path including the first terminal, the first resistive film, and the second terminal; and

a coordinate determination unit configured to determine the coordinates touched by the user, based upon the panel voltage and the panel current thus detected,

when the user touches two points, the panel current has a value according to an interval between the two points, and there is a one-to-one correspondence between the panel current and the interval between the two points,

and the interval between the two points is determined based upon the value of the panel current by referring to the one-to-one correspondence,

wherein the coordinate determination unit determines the midpoint between the aforementioned two coordinates, based upon the panel voltage,

and wherein the coordinates of one of the aforementioned two points are determined by adding a value that corresponds to the interval between the two coordinates to the midpoint coordinates,

and wherein the coordinates of the other of the two points are determined by subtracting, from the midpoint coordinates, a value that corresponds to the interval between the two coordinates.

12. An electronic device comprising a touch panel input apparatus according to claim 11.