Electrostatic capacitance detection device

• US 9,261,547 B2
• Filed: 05/13/2013
• Issued: 02/16/2016
• Est. Priority Date: 06/22/2012
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Tokai RIKA Denki Seisakusho
• Original Assignee: Kabushiki Kaisha Tokai RIKA Denki Seisakusho
• Inventors: Shimizu, Tomomi
• Primary Examiner(s): Koval, Melissa
• Assistant Examiner(s): NGUYEN, TRUNG Q
• Application Number:
  US13/892,505
• Publication Number:
  US 20130342220A1
• Time in Patent Office: 1,009 Days
• Field of Search: 324/600, 324658-661, 324/500, 324/519, 324/512, 324/679, 324/670, 324/690, 324/548, 345173-178
• US Class Current: 1/1
• CPC Class Codes: G01R 27/2605 Measuring capacitance capacitive sensors G01D5/24
• CPC Class Codes: G01R 31/2829 Testing of circuits in sensor or actuator systems testing of apparatus for measuring electric or magnetic variables G01R35/00; testing of indicating or recording apparatus G01D; in airbag systems B60R21/0173; checking gas analysers G01N33/007; monitoring or fail-safe circuits for electromagnets H01F7/1844
• CPC Class Codes: H03K 17/9622 using a plurality of detectors, e.g. keyboard
• CPC Class Codes: H03K 2217/960705 Safety of capacitive touch and proximity switches, e.g. increasing reliability, fail-safe

Abstract

An electrostatic capacitance detection device includes a plurality of electrodes configured to detect an electrostatic capacitance, an electrostatic capacitance measurement part configured to select one electrode from the plurality of electrodes as a detection electrode, to allow the electrodes other than the detection electrode to be in a first electric potential condition and then to be in a second electric potential condition that is different from the first electric potential condition, and to measure a first voltage of the detection electrode in the first electric potential condition and a second voltage of the detection electrode in the second electric potential condition, and a judgment part configured to compare measurement values based on the first and the second voltages of the detection electrode, thereby to judge whether the detection electrode is in a short circuit condition.

Claims

1. An electrostatic capacitance detection device, comprising:

a plurality of electrodes formed on a touch panel and configured to detect an electrostatic capacitance;

an electrostatic capacitance measurement part configured to select one electrode from the plurality of electrodes as a detection electrode, to allow the electrodes other than the detection electrode to be in a first electric potential condition and then to be in a second electric potential condition that is different from the first electric potential condition, and to measure a first voltage of the detection electrode in the first electric potential condition and a second voltage of the detection electrode in the second electric potential condition; and

a judgment part configured to compare measurement values based on the first and the second voltages of the detection electrode, thereby to judge whether the detection electrode is in a short circuit condition,

wherein the electrostatic capacitance measurement part is configured to sequentially perform a first loop measurement with respect to all of the plurality of electrodes, the first loop measurement comprising;

selecting one of the plurality of electrodes as the detection electrode;

rendering the plurality of electrodes except for the selected detection electrode in the first electric potential condition; and

measuring the first voltage of the selected detection electrode in the first electric potential condition, and

wherein the electrostatic capacitance measurement part is configured to, after the first loop measurement, sequentially perform a second loop measurement with respect to all of the plurality of electrodes, the second loop measurement comprising;

selecting one of the plurality of electrodes as the detection electrode;

rendering the plurality of electrodes except for the selected detection electrode in the second electric potential condition; and

measuring the second voltage of the selected detection electrode in the second electric potential condition.

2. The electrostatic capacitance detection device according to claim 1, wherein the first electric potential condition is one of Open, Lo and Hi, and the second electric potential condition is one of Open condition, Lo condition and Hi condition and is different from the first electric potential condition.

3. The electrostatic capacitance detection device according to claim 1, wherein the electrostatic capacitance measurement part measures more than once the first and second voltages of the detection electrode in the first and the second electric potential conditions.

4. The electrostatic capacitance detection device according to claim 1, wherein the judgment part configured to compare, with respect to all of the plurality of electrodes, a first measurement value based on the first voltage measured at the first loop measurement and a second measurement value based on the second voltage measured at the first loop measurement, thereby to judge whether the selected detection electrode is in the short circuit condition.

5. The electrostatic capacitance detection device according to claim 4, wherein the judgment part judges that the selected detection electrode is in the shot circuit condition when a difference between the first measurement value and the second measurement value is beyond a predetermined threshold value.