Light emitting device and method of driving the same

• US 8,947,328 B2
• Filed: 04/07/2005
• Issued: 02/03/2015
• Est. Priority Date: 09/07/2001
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Kimura, Hajime
• Primary Examiner(s): Chang, Kent
• Assistant Examiner(s): Shah, Sujit
• Application Number:
  US11/101,330
• Publication Number:
  US 20050179628A1
• Time in Patent Office: 3,589 Days
• Field of Search: 345/60, 345/63, 345/64, 345/74.1, 345/75.1, 345/75.2, 345/76, 345/77, 345/78, 345/79, 345/80, 345/81, 345/82, 345/83, 345/89, 345/90, 345/92, 345/94, 345/95, 345/96, 345/98, 345/99, 345/100, 345/101, 345/204, 345/205, 345/206, 345/207, 345/208, 345/209, 345/210, 345/214, 345/690, 345/691, 345/696, 345/693, 315/169.1, 315/169.2, 315/169.3, 315/169.4
• US Class Current: 345/77
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2310/0251 Precharge or discharge of pixel before applying new pixel voltage
• CPC Class Codes: G09G 2320/02 Improving the quality of display appearance
• CPC Class Codes: G09G 2320/0257 Reduction of after-image effects
• CPC Class Codes: G09G 2320/0285 using tables for spatial correction of display data
• 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 2320/0295 by monitoring each display pixel
• CPC Class Codes: G09G 2320/043 Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 2340/14 Solving problems related to the presentation of information to be displayed
• CPC Class Codes: G09G 3/2059 using error diffusion
• CPC Class Codes: G09G 3/22 using controlled light sources
• CPC Class Codes: G09G 3/3233 with pixel circuitry controlling the current through the light-emitting element
• CPC Class Codes: G09G 3/3291 in which the data driver supplies a variable data voltage for setting the current through, or the voltage across, the light-emitting elements

Abstract

The present invention specifies the characteristic of a driving transistor provided in a pixel and corrects a video signal to be inputted to the pixel based on the specification. As a result, a light emitting device and its driving method in which influence of fluctuation in characteristic among transistors is removed to obtain clear multi-gray scale are provided. The present invention can also provide a light emitting device and its driving method in which a change with age in amount of current flowing between two electrodes of a light emitting element is reduced to obtain clear multi-gray scale display.

Claims

1. A method of driving a light emitting device, comprising:

inputting a first signal having a first potential P₀ to each of a plurality of pixels;

obtaining a first current value I₀ of all of the plurality of pixels after inputting the first signal to each of the plurality of pixels;

inputting a second signal having a second potential P₁ to a first pixel of the plurality of pixels;

obtaining a second current value I₁ of all of the plurality of pixels after inputting the second signal to the first pixel;

inputting a third signal P₂ having a third potential to the first pixel;

obtaining a third current value I₂ of all of the plurality of pixels after inputting the third signal P₂ to the first pixel;

calculating a current value Q₁ and a current value Q₂ which are Q₁=I₁−

I₀ and Q₂=I₂−

I₀;

obtaining an interpolation function F from two sets of data (P, Q)=(P₁, Q₁) and (P₂, Q₂); and

storing constants in the interpolation function F to a storage medium in the light emitting device,

wherein the first current value I₀ is a current value of when each of the plurality of pixels does not emit light.

2. The method of driving the light emitting device according to claim 1, wherein the first current value I₀, the second current value I₁, and the third current value I₂ are obtained before shipping the light emitting device.

3. The method of driving the light emitting device according to claim 1, wherein the first current value I₀ and the second current value I₁ are obtained by measuring a current flowing through a cathode line electrically connected to cathode electrodes of light emitting elements of the plurality of pixels.

4. A method of driving a light emitting device, comprising:

inputting a first signal having a first potential P₀ to each of a plurality of pixels;

obtaining a first current value I₀ of all of the plurality of pixels after inputting the first signal to each of the plurality of pixels;

inputting a second signal having a second potential P₁ to a first pixel of the plurality of pixels;

obtaining a second current value I₁ of all of the plurality of pixels after inputting the second signal to the first pixel;

inputting a third signal P₂ having a third potential to the first pixel;

obtaining a third current value I₂ of all of the plurality of pixels after inputting the third signal P₂ to the first pixel;

calculating a current value Q₁ and a current value Q₂ which are Q₁=I₁−

I₀ and Q₂=I₂−

I₀;

obtaining an interpolation function F from two sets of data (P, Q)=(P₁, Q₁) and (P₂, Q₂); and

storing constants in the interpolation function F to a storage medium in the light emitting device,

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

wherein the first current value I₀ is a current value of when each of the plurality of pixels does not emit light.

5. The method of driving the light emitting device according to claim 4, wherein the first current value I₀, the second current value I₁, and the third current value I₂ are obtained before shipping the light emitting device.

6. The method of driving the light emitting device according to claim 4, wherein the first current value I₀ and the second current value I₁ are obtained by measuring a current flowing through a cathode line electrically connected to cathode electrodes of light emitting elements of the plurality of pixels.