Liquid crystal display, control method thereof and electronic device for minimizing flicker

• US 8,704,741 B2
• Filed: 06/03/2010
• Issued: 04/22/2014
• Est. Priority Date: 06/03/2009
• Status: Active Grant

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: Mizusako, Kazuhisa, Toyooka, Takashi, Sasaki, Hitoshi
• Primary Examiner(s): Nguyen, Chanh
• Assistant Examiner(s): MISTRY, RAM A
• Application Number:
  US12/792,946
• Publication Number:
  US 20100309189A1
• Time in Patent Office: 1,419 Days
• Field of Search: 345/87, 345/90, 345/94, 345/95, 345/98
• US Class Current: 345/94
• CPC Class Codes: G09G 2300/0426 Layout of electrodes and connections
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2320/029 by monitoring one or more pixels in the display panel, e.g. by monitoring a fixed reference pixel
• CPC Class Codes: G09G 2330/028 Generation of voltages supplied to electrode drivers in a matrix display other than LCD
• CPC Class Codes: G09G 3/001 using specific devices not provided for in groups G09G3/02 - G09G3/36, e.g. using an intermediate record carrier such as a film slide; Projection systems; Display of non-alphanumerical information, solely or in combination with alphanumerical information, e.g. digital display on projected diapositive as background slide projectors per se G03B23/00 = 42 HP
• CPC Class Codes: G09G 3/3614 Control of polarity reversal in general
• CPC Class Codes: G09G 3/3677 suitable for active matrices only

Abstract

A liquid crystal display, applying to the first electrode, a voltage higher and a voltage lower at different timings, detecting a current flowing through the second electrode, designating, as a reference value, the current flowing through the second electrode when the voltage maintained in the liquid crystal element is reset, specifying a first current which is obtained by excluding a charging current due to application of a related higher voltage from currents flowing through the second electrode after the higher voltage is applied to the first electrode, and a second current which is obtained by excluding a charging current due to application of a related lower voltage from currents flowing through the second electrode after the lower voltage is applied to the first electrode, and comparing the first current with the second current, and controlling the first current and the second current based on the comparison result.

Claims

1. A liquid crystal display comprising:

a liquid crystal element in which a liquid crystal layer is sandwiched by a first electrode and a second electrode;

a driving circuit configured to apply, between the first electrode and the second electrode, a voltage for resetting a voltage maintained in the liquid crystal element and thereafter to apply, to the first electrode, a voltage higher than a predetermined voltage and a voltage lower than the predetermined voltage at different timings;

a detection circuit configured to detect a current flowing through the second electrode;

a comparison circuit configured to designate, as a reference value, the current flowing through the second electrode when the voltage maintained in the liquid crystal element is reset, to specify a first current which is obtained by excluding a charging current due to application of a related higher voltage from currents flowing through the second electrode when the higher voltage is applied to the first electrode, and a second current which is obtained by excluding a charging current due to application of a related lower voltage from currents flowing through the second electrode when the lower voltage is applied to the first electrode, and to compare the first current with the second current; and

a control circuit configured to control the first current and the second current based on the comparison result,

wherein the first electrode is a pixel electrode which is coupled to a data line via a switching element turned on when a scanning line is selected; and

the second electrode is a common electrode,

wherein the driving circuit comprises;

a scanning line driving circuit selecting the scanning line;

a data line driving circuit supplying a data signal for the data line at the selection period; and

a common electrode driving circuit supplying the common voltage for the common electrode;

wherein the comparison circuit is configured to compare an integral value for the first current with an integral value for the second current and integrate the first current and the second current for a portion of a vertical scanning period.

2. The liquid crystal display according to claim 1, wherein the driving circuit is configured to apply the same voltage to the first electrode and the second electrode, as the voltage for resetting a voltage maintained in the liquid crystal element.

3. The liquid crystal display according to claim 2, wherein the control circuit is configured to specify, as the first current or the second current, a current flowing through the second electrode after a predetermined time has elapsed since the higher voltage or the lower voltage is applied.

4. The liquid crystal display according to claim 1, wherein the control circuit is configured to increase or decrease the common voltage based on the comparison result.

5. The liquid crystal display according to claim 1, wherein the control circuit configured to alter a duration where the higher voltage is maintained in the pixel electrode and a duration where the lower voltage is maintained in the pixel electrode, based on the comparison result.

6. The liquid crystal display according to claim 1, wherein the detection circuit comprises a resistor interposed in a signal line transmitting the predetermined voltage to the second electrode;

and

a voltage amplification circuit amplifying a voltage across the resistor,

wherein the detection circuit is configured to detect the voltage amplified by the voltage amplification circuit as the current flowing through the second electrode.

7. The liquid crystal display according to claim 1, wherein the detection circuit is configured to detect a current flowing through the second electrode of the liquid crystal element placed in an area other than a display area.

8. An electronic device comprising any one of the liquid crystal displays according to claim 1.