EL DISPLAY APPARATUS AND METHOD FOR DRIVING EL DISPLAY APPARATUS

• US 20070126667A1
• Filed: 11/30/2006
• Published: 06/07/2007
• Est. Priority Date: 12/01/2005
• Status: Abandoned Application

• Current Assignee: Toshiba Matsushita Display Technology (Japan Display Incorporated)
• Original Assignee: Toshiba Matsushita Display Technology (Japan Display Incorporated)
• Inventors: Takahara, Hiroshi, NAKAMURA, Norio
• Application Number:
  US11/565,182
• Publication Number:
  US 20070126667A1
• Time in Patent Office: Days
• US Class Current: 345/76
• CPC Class Codes: G09G 2300/0417 Special arrangements specific to the use of low carrier mobility technology
• 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 2300/0852 being a dynamic memory with more than 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 2310/0205 Simultaneous scanning of several lines in flat panels
• CPC Class Codes: G09G 2310/0248 Precharge or discharge of column electrodes before or after applying exact column voltages
• CPC Class Codes: G09G 2310/0289 Details of voltage level shifters arranged for use in a driving circuit
• CPC Class Codes: G09G 2320/0233 Improving the luminance or brightness uniformity across the screen
• CPC Class Codes: G09G 2320/0261 in the context of movement of objects on the screen or movement of the observer relative to the screen
• CPC Class Codes: G09G 2320/041 Temperature compensation
• CPC Class Codes: G09G 2330/028 Generation of voltages supplied to electrode drivers in a matrix display other than LCD
• CPC Class Codes: G09G 3/3233 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
• CPC Class Codes: G09G 3/325 the data current flowing through the driving transistor during a setting phase, e.g. by using a switch for connecting the driving transistor to the data driver
• CPC Class Codes: G09G 3/3266 Details of drivers for scan electrodes
• CPC Class Codes: G09G 3/3283 in which the data driver supplies a variable data current for setting the current through, or the voltage across, the light-emitting elements

Abstract

An EL display apparatus in which pixels having EL elements are formed in a matrix, has a constant current circuit which generates a predetermined constant current; and a gradation voltage circuit which generates a gradation voltage; wherein the constant current generated by the constant current circuit is supplied to the pixels via a source signal line; and the gradation voltage generated by the gradation voltage circuit is supplied to the pixels via the source signal line.

Claims

1. An EL display apparatus in which pixels having EL elements are formed in a matrix, comprising:

a constant current circuit which generates a predetermined constant current; and

a gradation voltage circuit which generates a gradation voltage;

wherein said constant current generated by said constant current circuit is supplied to said pixels via a source signal line; and

said gradation voltage generated by said gradation voltage circuit is supplied to said pixels via said source signal line.

2. A driving method of an EL display apparatus in which pixels having EL elements are formed in a matrix, wherein said EL display apparatus comprises:

a constant current circuit which generates a predetermined constant current; and

a gradation voltage circuit which generates a gradation voltage;

wherein said pixel has a driver transistor for supplying a driving current to said EL element and a switching transistor for forming a current path between a source signal line and said driver transistor;

said driving method of the EL display element comprises the steps of;

applying said constant current generated by said constant current circuit to said pixel via said source signal line;

obtaining a potential of said source signal line, while said constant current is applied to said source signal line; and

adding said obtained potential to said gradation voltage or subtracting said gradation voltage from said obtained potential, and applying the result of said addition or subtraction to said driver transistor of said pixels via said source signal line.

3. The driving method of the EL display apparatus according to claim 2, wherein a pre-charge voltage is applied to said source signal line or said pixel during or before a period in which said constant current is applied to said pixel.

4. The driving method of the EL display apparatus according to claim 2, wherein a constant current circuit is formed by a plurality of unitary transistors.

5. An EL display apparatus in which pixels having EL elements are formed in a matrix, comprising:

a constant current circuit which generates a predetermined constant current; and

a gradation voltage circuit which generates a gradation voltage;

wherein said pixel has a driver transistor for supplying a driving current to said EL element, a capacitor connected to a gate terminal of said driver transistor, a first switching transistor for forming a current path between a source signal line and said driver transistor, and a second switching transistor for applying said gradation voltage to said driving transistor via said capacitor.

6. An EL display apparatus in which pixels having EL elements are formed in a matrix, comprising:

a constant current circuit which generates a predetermined constant current; and

a gradation voltage circuit which generates a gradation voltage;

a first signal line which supplies said constant current to said pixel; and

a second source signal line which supplies said gradation voltage to said pixel;

wherein said pixel has a driver transistor for supplying a driving current to said EL element, a capacitor connected to a gate terminal of said driver transistor, a first switching transistor for forming a current path between said first source signal line and said driver transistor, and a second switching transistor for forming an electronic path between said second source signal line and a capacitor.

7. An EL display apparatus in which pixels having EL elements are formed in a matrix, comprising:

a constant current circuit which generates a predetermined constant current;

a gradation voltage circuit which generates a gradation voltage;

a capacitor; and

a source signal line which supplies said constant current to said pixel;

wherein said gradation voltage is applied to said source signal line via said capacitor.

8. An EL display apparatus, comprising:

a display unit in which pixels having EL elements are formed in a matrix;

a constant current output circuit which outputs a reset current to a driver transistor of said EL element;

a voltage holding circuit which obtains a gate terminal potential of said driver transistor while said reset current is applied;

a gradation voltage circuit which outputs a gradation voltage corresponding to a video signal; and

a voltage applying circuit which adds said gate terminal potential, to said gradation voltage or subtracts said gradation voltage from said gate terminal potential, and applying the result of said addition or subtraction to a gate terminal of said driver transistor.