EL emitting touch switch

• US 8,766,924 B2
• Filed: 03/14/2008
• Issued: 07/01/2014
• Est. Priority Date: 09/19/2007
• Status: Active Grant

• Current Assignee: Mitsubishi Jidosha Kogyo Kabushiki Kaisha, Visteon Japan, Ltd. (Visteon Corporation)
• Original Assignee: Mitsubishi Jidosha Kogyo Kabushiki Kaisha, Visteon Japan, Ltd. (Visteon Corporation)
• Inventors: Yamauchi, Kazuto, Murayama, Yasunori, Tanaka, Sadahiko, Takizawa, Keitaro, Yamanoue, Kouichi
• Primary Examiner(s): HERNANDEZ, JESUS J
• Application Number:
  US12/076,207
• Publication Number:
  US 20090073133A1
• Time in Patent Office: 2,300 Days
• Field of Search: None
• US Class Current: 345/173
• CPC Class Codes: H03K 17/9622 using a plurality of detectors, e.g. keyboard
• CPC Class Codes: H03K 2217/960785 with illumination

Abstract

An EL emitting touch switch includes first electrodes, a single second electrode facing the first electrodes, and EL layers each sandwiched between a corresponding one of the first electrodes and the second electrode. A light emission driver applies a driving voltage between the first and second electrodes to cause the EL layers to emit light. A timing signal generator generates a timing signal to control the light emission driver such that the application of the driving voltage is stopped at predetermined intervals. Touch decision units are provided for each first electrode. Each touch decision unit includes a feedback circuit for supplying current to the corresponding first electrode such that the potentials of the first and second electrodes become equal to each other, and detects contact of a human body with the corresponding first electrode based on operation of the feedback circuit while the application of the driving voltage is stopped.

Claims

1. An EL emitting touch switch, comprising:

a plurality of first electrodes having light permeability;

a second electrode arranged so as to face the plurality of first electrodes, the second electrode functioning as a single electrode associated with the plurality of first electrodes;

a plurality of EL layers each sandwiched between a corresponding one of the first electrodes and the second electrode, each of the EL layers being a laminate including a phosphor layer and an electrically insulating layer;

light emission driving means for applying a driving voltage between each of the first electrodes and the second electrode to cause the EL layers to emit light, the light emission driving means including switching elements that selectively and electrically connect each of the plurality of first electrodes to a ground potential and disconnect the first electrodes from the ground potential;

timing signal generating means for generating a first timing signal to control the light emission driving means such that the application of the driving voltage is stopped at predetermined intervals by electrically disconnecting the first electrodes from the ground potential by the switching elements while the first timing signal is being output, the first timing signal being a pulse signal having a first predetermined width; and

touch decision means provided for each of the first electrodes, each of the touch decision means including a feedback circuit that supplies an electric current to a corresponding one of the first electrodes such that potentials of the corresponding first electrode and the second electrode become equal to each other when the first timing signal is being output, and a decision circuit that detects contact of a human body with the corresponding first electrode based on operation of the feedback circuit only while the application of the driving voltage by the light emission driving means is being stopped in accordance with the first timing signal,

wherein the timing signal generating means generates a second timing signal while the first timing signal is being output, the second timing signal being a pulse signal having a second predetermined width shorter than the first predetermined width such that the second timing signal completely overlaps the first timing signal, and

the decision circuit detects contact of a human body at a rise timing of the second timing signal from the timing signal generating means.

2. The EL emitting touch switch according to claim 1,

wherein said feedback circuit is a differential amplifier circuit including an operational amplifier and resistors;

and

each of said touch decision means detects the contact of a human body with the corresponding first electrode based on an output voltage of the operational amplifier.

3. An EL emitting touch switch, comprising:

a plurality of first electrodes having light permeability;

a second electrode arranged so as to face the plurality of first electrodes, the second electrode functioning as a single electrode associated with the plurality of first electrodes;

a plurality of EL layers each sandwiched between a corresponding one of the first electrodes and the second electrode, each of the EL layers being a laminate including a phosphor layer and an electrically insulating layer;

light emission driving means for applying a driving voltage between each of the first electrodes and the second electrode to cause the EL layers to emit light, the light emission driving means including switching elements that selectively and electrically connect each of the plurality of first electrodes to a ground potential and disconnect the first electrodes from the ground potential;

timing signal generating means for generating a first timing signal to control the light emission driving means such that the application of the driving voltage is stopped at predetermined intervals by electrically disconnecting the first electrodes from the ground potential by the switching elements while the timing signal is being output, the first timing signal being a pulse signal having a first predetermined width, and a second timing signal while the first timing signal is being output, the second timing signal being a pulse signal having a second predetermined width shorter than the first predetermined width such that the second timing signal completely overlaps the first timing signal; and

touch decision means provided for each of the first electrodes, each of the touch decision means including a feedback circuit that supplies an electric current to a corresponding one of the first electrodes such that potentials of the corresponding first electrode and the second electrode become equal to each other when the first timing signal is being output, and each of the touch decision means detecting contact of a human body with the corresponding first electrode based on operation of the feedback circuit only while the application of the driving voltage by the light emission driving means is being stopped in accordance with the timing signal and at a rise timing of the second timing signal,

wherein said feedback circuit is a differential amplifier circuit including an operational amplifier and resistors, and

each of said touch decision means detects the contact of a human body with the corresponding first electrode based on an output voltage of the operational amplifier,

wherein the resistors includes,

a first resistor connected between the first electrode and a first input terminal of the operational amplifier,

a second resistor that has a resistance same as a resistance of the first resistor, and connected between the second electrode and a second input terminal of the operational amplifier,

a third resistor connected between the first input terminal and an output terminal of the operational amplifier, and

a fourth resistor that has a resistance same as a resistance of the third resistor, and connected between the second input terminal of the operational amplifier and a ground potential.