IMAGE DISPLAY APPARATUS AND CONTROL METHOD THEREFOR

• US 20100328294A1
• Filed: 09/07/2010
• Published: 12/30/2010
• Est. Priority Date: 03/05/2002
• Status: Abandoned Application

• Current Assignee: Isao Sasaki, Koichi Iguchi
• Original Assignee: Isao Sasaki, Koichi Iguchi
• Inventors: Iguchi, Koichi, Sasaki, Isao
• Application Number:
  US12/877,068
• Publication Number:
  US 20100328294A1
• Time in Patent Office: Days
• US Class Current: 345/211
• CPC Class Codes: G09G 2300/0465 Improved aperture ratio, e.g. by size reduction of the pixel circuit, e.g. for improving the pixel density or the maximum displayable luminance or brightness
• CPC Class Codes: G09G 2300/0819 used for counteracting undesired variations, e.g. feedback or autozeroing
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2300/0861 with additional control of the display period without amending the charge stored in a pixel memory, e.g. by means of additional select electrodes
• CPC Class Codes: G09G 2310/0251 Precharge or discharge of pixel before applying new pixel voltage
• CPC Class Codes: G09G 2310/0254 Control of polarity reversal in general, other than for liquid crystal displays
• CPC Class Codes: G09G 2310/0256 with the purpose of reversing the voltage across a light emitting or modulating element within a pixel
• CPC Class Codes: G09G 2320/043 Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 3/3233 with pixel circuitry controlling the current through the light-emitting element
• CPC Class Codes: G09G 3/3241 the current through the light-emitting element being set using a data current provided by the data driver, e.g. by using a two-transistor current mirror

Abstract

An image display apparatus comprises a pixel having a drive transistor and a pixel display element which are connected in series between a first power line and a second power line, a holding capacitor connected to a gate electrode of the drive transistor, and a selection transistor connected between a signal line and the gate electrode of the drive transistor. When the selection transistor is turned on, gradation pixel data is written in the holding capacitor from the signal line. The charge of gradation pixel data written in the holding capacitor is discharged for a certain period through the drive transistor, thereafter the charge of the gradation pixel data stored in the holding capacitor is held by floating the gate electrode of the drive transistor.

Claims

1-42. -42. (canceled)

43. An image display apparatus comprising:

a pixel having a drive transistor and a pixel display element which are electrically connected in series between a first power line and a second power line, a holding capacitor electrically connected to a gate electrode of said drive transistor, and a selection transistor electrically connected between a signal line and the gate electrode of said drive transistor; and

a controller for turning on said selection transistor thereby to write gradation pixel data in said holding capacitor from said signal line, discharging charges of the gradation pixel data written in said holding capacitor through said drive transistor for a predetermined time less than a frame time, and thereafter floating the gate electrode of said drive transistor thereby to hold the charges of the gradation pixel data stored in said holding capacitor.

44. The image display apparatus according to claim 43, further comprising:

a display panel having a plurality of signal lines to which corresponding gradation pixel data are applied and a plurality of scanning lines to which scanning signals are applied, said pixel being positioned at each of points of intersection between said signal lines and said scanning lines;

a signal line driver for applying said gradation pixel data to said signal lines based on a pixel input signal; and

a scanning line driver for applying said scanning signals to said scanning lines;

wherein said selection transistor has a first drain electrode, a first source electrode, and a first gate electrode, said drive transistor has a second drain electrode, a second source electrode, and a second gate electrode, said holding capacitor holds a voltage between said second gate electrode and said second source electrode, and said pixel display element has a first electrode and a second electrode;

wherein said first drain electrode/said first source electrode is connected to said signal line, said first source electrode/said first drain electrode is connected to said second gate electrode, said first gate electrode is connected to said scanning line, and said selection transistor performs on/off control of a conduction state between said signal line and said second gate electrode based on said scanning signal;

wherein said first power line is connected to said second drain electrode, said second source electrode is connected to said first electrode, and said drive transistor passes an output current controlled based on a voltage held by said holding capacitor from said second source electrode to said first electrode; and

wherein said second power line is connected to said second electrode, and said pixel display element displays a pixel at a gradation based on said output current of said drive transistor.

45. The image display apparatus according to claim 44, wherein said scanning signals are applied to said scanning lines in a preset sequence.

46. The image display apparatus according to claim 43, wherein said pixel display element comprises an organic electroluminescence element.

47. A control method for an image display apparatus including a pixel having a drive transistor and a pixel display element which are connected in series between a first power line and a second power line, a holding capacitor connected to a gate electrode of said drive transistor, and a selection transistor connected between a signal line and the gate electrode of said drive transistor, comprising:

a pixel data writing step of turning on said selection transistor thereby to write gradation pixel data in said holding capacitor from said signal line;

a discharging step of discharging charges of the gradation pixel data written in said holding capacitor through said drive transistor for a predetermined time less than a frame time; and

after said discharging step, a pixel data holding step of floating the gate electrode of said drive transistor thereby to hold the charges of the gradation pixel data stored in said holding capacitor.

48. The control method according to claim 47, wherein said image display apparatus further includes:

a display panel having a plurality of signal lines to which corresponding gradation pixel data are applied and a plurality of scanning lines to which scanning signals are applied, said pixel being positioned at each of points of intersection between said signal lines and said scanning lines;

a signal line driver for applying said gradation pixel data to said signal lines based on a pixel input signal; and

a scanning line driver for applying said scanning signals to said scanning lines;

wherein said selection transistor has a first drain electrode, a first source electrode, and a first gate electrode, said drive transistor has a second drain electrode, a second source electrode, and a second gate electrode, said holding capacitor holds a voltage between said second gate electrode and said second source electrode, and said pixel display element has a first electrode and a second electrode;

wherein said first drain electrode/said first source electrode is connected to said signal line, said first source electrode/said first drain electrode is connected to said second gate electrode, said first gate electrode is connected to said scanning line, said selection transistor performs on/off control of a conduction state between said signal line and said second gate electrode based on said scanning signal;

wherein said first power line is connected to said second drain electrode, said second source electrode is connected to said first electrode, and said drive transistor passes an output current controlled based on a voltage held by said holding capacitor from said second source electrode to said first electrode; and

wherein said second power line is connected to said second electrode, and said pixel display element displays a pixel at a gradation based on said output current of said drive transistor.

49. The control method according to claim 48, wherein said scanning signals are applied to said scanning lines in a preset sequence.

50. The control method according to claim 47, wherein said pixel display element comprises an organic electroluminescence element.

51. An image display apparatus comprising:

a pixel having a drive transistor and a pixel display element which are electrically connected in a series between a first power line and a second power line, a holding capacitor electrically connected between a gate electrode of said drive transistor and a junction node, and a selection transistor electrically connected between a signal line and the gate electrode of said drive transistor, said junction node being of between said pixel display element and a source electrode of said drive transistor.

52. An image display apparatus comprising:

a pixel having a drive transistor and a pixel display element which are electrically connected in a series between a first power line and a second power line, a holding capacitor electrically connected between a gate electrode of said drive transistor and a source electrode of said drive transistor, a selection transistor electrically connected between a signal line and the gate electrode of said drive transistor; and

a controller for discharging charges written in said holding capacitor for a predetermined time less than a frame time, and thereafter floating the gate electrode of said drive transistor thereby to hold the charges of the gradation pixel data stored in said holding capacitor.