Light emitting device and driving method thereof

• US 7,796,099 B2
• Filed: 04/18/2006
• Issued: 09/14/2010
• Est. Priority Date: 09/05/2002
• Status: Expired due to Fees

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Yamazaki, Yu, Osame, Mitsuaki
• Primary Examiner(s): Vu; David Hung
• Application Number:
  US11/379,145
• Publication Number:
  US 20060186832A1
• Time in Patent Office: 1,610 Days
• Field of Search: 345/76, 345/77, 345/78, 345/83, 345/82, 345/84, 345/92, 345/204, 315/169.3
• US Class Current: 345/76
• CPC Class Codes: G09G 2300/0809 Several active elements per pixel in active matrix panels
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2300/0866 by means of changes in the pixel supply voltage
• CPC Class Codes: G09G 2310/0251 Precharge or discharge of pixel before applying new pixel voltage
• 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 2310/0289 Details of voltage level shifters arranged for use in a driving circuit
• CPC Class Codes: G09G 2320/043 Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 2320/0666 for control of colour parameters, e.g. colour temperature
• CPC Class Codes: G09G 2330/02 Details of power systems and of start or stop of display operation
• CPC Class Codes: G09G 2330/028 Generation of voltages supplied to electrode drivers in a matrix display other than LCD
• CPC Class Codes: G09G 3/22 using controlled light sources
• CPC Class Codes: G09G 3/3275 Details of drivers for data electrodes

Abstract

A light emitting device which is able to suppress power consumption while a balance of white light is maintained is provided. According to the present invention, either the potential level of the Hi video signal or Lo video signal which is given to a gate electrode of a transistor, and the potential level of the power source lines are changed by the respective corresponding colors. Concretely, the potential level at the side of Lo and the potential level of the power source line are made to be changed by the respective corresponding colors when a transistor which controls current supplied to a light emitting element is a p-channel type. Conversely, the potential level at the side of the Hi and potential level of the power source line are made to be changed by the respective corresponding colors when a transistor which controls current supplied to a light emitting element is an n-channel type.

Claims

1. A method of a driving a light emitting device, the light emitting device comprising a plurality of first pixels electrically connected to a first line and a second line, a plurality of second pixels electrically connected to a third line and a fourth line, each of the plurality of first and second pixels comprising a light emitting element and a transistor electrically connected to the light emitting element, the method comprising:

applying a first potential to the first line;

applying a second potential to the second line, wherein the second potential is a constant potential;

applying a third potential to the third line;

applying a fourth potential to the fourth line, wherein the fourth potential is a constant potential,

wherein each of the light emitting elements included in the first and second pixels emits a light when the first potential is different from the third potential,

wherein each of the light emitting elements included in the first and second pixels does not emit a light when the first potential is the same as the third potential,

wherein the second potential is different from the fourth potential, and

wherein the transistor is operated in a saturated region when the light emitting element emits light.

2. The method according to claim 1, wherein the plurality of first pixels emit a light corresponding to a color selected from the group consisting of red, green, and blue and the color is different from a color of a light emitted from the second pixels.

3. The method according to claim 1, wherein the plurality of second pixels emit a light corresponding to a color selected from the group consisting of red, green, and blue and the color is different from a color of a light emitted from the first pixels.

4. The method according to claim 1, wherein the plurality of first pixels emit a light different from that emitted from the plurality of second pixels.

5. The method according to claim 1, wherein the transistor is a p-channel type transistor.

6. The method according to claim 5, wherein the first and third potentials when the p-channel type transistor is turned off stay the same and are equal to or higher than a highest potential among the second and fourth potentials.

7. The method according to claim 1, wherein the transistor is an n-channel type transistor.

8. The method according to claim 7, wherein the first and third potentials when the n-channel type transistor is turned off stay the same and are equal to or lower than a lowest potential among the second and fourth potentials.

9. The method according to claim 1, wherein a voltage applied to light emitting elements included in the plurality of first pixels is different from a voltage applied to light emitting elements included in the plurality of second pixels.

10. A method of driving a light emitting device, the light emitting device comprising a plurality of first pixels connected to a first signal line and a first power source line, a plurality of second pixels connected to a second signal line and a second power source line, each of the plurality of first and second pixels comprising a light emitting element and a transistor connected to the light emitting element, the method comprising:

applying a first video signal to the first signal line;

applying a second video signal to the second signal line;

applying a first voltage to the first power source line; and

applying a second voltage to the second power source line,

wherein each of the light emitting elements included in the first and second pixels emits a light when a potential of the first video signal is different from a potential of the second video signal,

wherein each of the light emitting elements included in the first and second pixels does not emit a light when a potential of the first video signal is the same as a potential of the second video signal,

wherein a potential of the first power source line is different from a potential of the second power source line, and

wherein the transistor is operated in a saturated region.

11. The method according to claim 10, wherein the plurality of first pixels emit a light corresponding to a color selected from the group consisting of red, green, and blue, and the color is different from a color of a light emitted from the second pixels.

12. The method according to claim 10, wherein the plurality of second pixels emit a light corresponding to a color selected from the group consisting of red, green, and blue, and the color is different from a color of a light emitted from the first pixels.

13. The method according to claim 10, wherein the plurality of first pixels emit a light different from that emitted from the plurality of second pixels.

14. The method according to claim 10, wherein the first video signal is a signal that turns on transistors provided at the plurality of first pixels, and the second video signal is a signal that turns on transistors provided at the plurality of second pixels.

15. The method according to claim 10, wherein the transistor is a p-channel type transistor.

16. The method according to claim 15, wherein potentials of the first and second signal lines when the p-channel type transistor is turned off stay the same and are equal to or higher than a highest potential in the first and second power source lines.

17. The method according to claim 10, wherein the transistor is an n-channel type transistor.

18. The method according to claim 17 wherein potentials of the first and second signal lines when the n-channel type transistor is turned off stay the same and are equal to or lower than a lowest potential in the first and second power source lines.