# US 7,609,236 B2 · Display device and method of driving the same > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,609,236 B2 - Document ID: US7609236B2 - Status: Granted - Kind: B2 - Application number: 10/924,775 - Filed: 2004-08-25 - Published: 2005-01-27 - Granted: 2009-10-27 - Earliest claimed: 2000-08-10 - Assignees: Semiconductor Energy Laboratory Co., Ltd. - Inventors: Jun Koyama - Web page: https://patentgrep.com/patent/US7609236B2 ## CPC - H10D 30/6715: {characterised by the doping profiles, e.g. having lightly-doped source or drain extensions} - G09G 3/2081: {with combination of amplitude modulation and time modulation (space and time error diffusion G09G3/2066)} - G09G 3/3258: with pixel circuitry controlling the voltage across the light-emitting element - 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 - H10D 30/0314: {of lateral top-gate TFTs comprising only a single gate} - H10D 30/0321: {comprising silicon, e.g. amorphous silicon or polysilicon} - G09G 3/2022: {using sub-frames} - G09G 3/2025: {the sub-frames having all the same time duration} - G09G 3/3233: with pixel circuitry controlling the current through the light-emitting element - G09G 2300/0408: Integration of the drivers onto the display substrate - G09G 2300/0426: Layout of electrodes and connections - G09G 2300/0814: used for selection purposes, e.g. logical AND for partial update - G09G 2300/0842: forming a memory circuit, e.g. a dynamic memory with one capacitor - G09G 2300/0866: by means of changes in the pixel supply voltage - G09G 2320/029: by monitoring one or more pixels in the display panel, e.g. by monitoring a fixed reference pixel - G09G 2320/041: Temperature compensation - H10D 30/6721: {having lightly-doped extensions consisting of multiple lightly doped zones or having non-homogeneous dopant distributions, e.g. graded LDD} - H10D 86/00: Integrated devices formed in or on insulating or conducting substrates, e.g. formed in silicon-on-insulator [SOI] substrates or on stainless steel or glass substrates - H10D 86/021: {of multiple TFTs} - H10D 86/0221: {comprising manufacture, treatment or patterning of TFT semiconductor bodies} - H10D 86/40: characterised by multiple TFTs - H10D 86/60: wherein the TFTs are in active matrices - H10K 59/12: Active-matrix OLED [AMOLED] displays - H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES - G09G: ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION (arrangements for transferring data between digital computers and displays G06F3/14; static indicating arrangements comprising an association of a number of separate sources or light control cells G09F9/00; static indicating arrangements comprising integral associations of a number of light sources H01J, H01K, H10H, H05B33/12; scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission, details thereof H04N1/00) - H10K: ORGANIC ELECTRIC SOLID-STATE DEVICES ## Abstract A display is conducted by using a time gray-scale system, in which one frame period is divided into a plurality of sub-frame periods, and a voltage applied to an EL element of a pixel is varied on a sub-frame period basis. Because of this, a display device is provided in which the fluctuations in brightness caused by an environment temperature of an EL element are suppressed with a gray-scale display method that is unlikely to be influenced by variations in characteristics of TFTs in a pixel portion and that is unlikely to be influenced by variations in a display period. ## Claims ### Claim 1 A display device comprising: a pixel portion formed over a substrate, the pixel portion having a light emitting element, wherein the light emitting element comprises a first electrode and a second electrode with a light emitting material interposed therebetween; a monitoring light emitting element electrically connected to the light emitting element through a power source line; and a plurality of constant current sources, wherein the monitoring light emitting element comprises the light emitting material interposed between a pair of electrodes, wherein any one of the plurality of constant current sources is electrically connected to the monitoring light emitting element through a switch, and wherein a brightness change of the light emitting element caused by a temperature change of the light emitting material interposed between the first electrode and the second electrode is suppressed by using the monitoring light emitting element. ### Claim 2 (depends on 1) A display device according to claim 1, wherein the monitoring light emitting element is provided independently of the pixel portion. ### Claim 3 (depends on 1) A display device according to claim 1, wherein the monitoring light emitting element is included in the pixel portion. ### Claim 4 (depends on 1) A display device according to claim 1, wherein the plurality of constant current sources is formed over an IC chip. ### Claim 5 (depends on 1) A display device according to claim 1, wherein the light emitting material comprises an organic compound. ### Claim 6 (depends on 1) A display device according to claim 1, wherein the display device is incorporated in at least one selected from the group consisting of a portable telephone, a video camera, a digital camera, a goggle type display, an image reproduction apparatus, and a personal computer. ### Claim 7 (depends on 1) A display device according to claim 1, wherein the display device is an EL display device. ### Claim 8 A display device comprising: a pixel portion formed over a substrate, the pixel portion having a light emitting element, wherein the light emitting element comprises a first electrode and a second electrode with a light emitting material interposed therebetween; a monitoring light emitting element electrically connected to the light emitting element through a power source line; and a plurality of constant current sources, wherein the monitoring light emitting element comprises the light emitting material interposed between a pair of electrodes, wherein any one of the plurality of constant current sources is electrically connected to the monitoring light emitting element through a switch, and wherein a brightness increase of the light emitting element caused by a temperature change of the light emitting material interposed between the first electrode and the second electrode is suppressed by using the monitoring light emitting element. ### Claim 9 A display device comprising: a pixel portion formed over a substrate, the pixel portion having a light emitting element, wherein the light emitting element comprises a first electrode and a second electrode with a light emitting material interposed therebetween; and a buffer amplifier, a monitoring light emitting element, and a plurality of constant current sources, wherein the monitoring light emitting element comprises the light emitting material interposed between a pair of electrodes, wherein the monitoring light emitting element and an input terminal of the buffer amplifier are electrically connected to any one of the plurality of constant current sources through a switch, wherein an output terminal of the buffer amplifier is electrically connected to the light emitting element, and wherein a brightness change of the light emitting element caused by a temperature change of the light emitting material interposed between the first electrode and the second electrode is suppressed by using the monitoring light emitting element. ### Claim 10 (depends on 9) A display device according to claim 9, wherein the buffer amplifier is formed over an IC chip. ### Claim 11 A display device comprising: a pixel portion formed over a substrate, the pixel portion having a light emitting element, wherein the light emitting element comprises a first electrode and a second electrode with a light emitting material interposed therebetween; and a buffer amplifier, a monitoring light emitting element, and a plurality of constant current sources, wherein the monitoring light emitting element comprises the light emitting material interposed between a pair of electrodes, wherein the monitoring light emitting element and an input terminal of the buffer amplifier are electrically connected to any one of the plurality of constant current sources through a switch, wherein an output terminal of the buffer amplifier is electrically connected to the light emitting element, and wherein a brightness increase of the light emitting element caused by a temperature change of the light emitting material interposed between the first electrode and the second electrode is suppressed by using the monitoring light emitting element. ### Claim 12 A display device comprising: a pixel portion formed over a substrate, the pixel portion having a light emitting element, wherein the light emitting element comprises a first electrode and a second electrode with a light emitting material interposed therebetween; and a buffer amplifier, a monitoring light emitting element, and a plurality of constant current sources, wherein the monitoring light emitting element comprises the light emitting material interposed between a pair of electrodes, wherein the monitoring light emitting element and an input terminal of the buffer amplifier are electrically connected to any one of the plurality of constant current sources through a switch, wherein an output terminal of the buffer amplifier is electrically connected to the light emitting element through a power source line, and wherein a brightness change of the light emitting element caused by a temperature change of the light emitting material interposed between the first electrode and the second electrode is suppressed by using the monitoring light emitting element. ### Claim 13 A display device comprising: a pixel portion formed over a substrate, the pixel portion having a light emitting element, wherein the light emitting element comprises a first electrode and a second electrode with a light emitting material interposed therebetween; and a buffer amplifier, a monitoring light emitting element, and a plurality of constant current sources, wherein the monitoring light emitting element comprises the light emitting material interposed between a pair of electrodes, wherein the monitoring light emitting element and an input terminal of the buffer amplifier are electrically connected to any one of the plurality of constant current sources through a switch, wherein an output terminal of the buffer amplifier is electrically connected to the light emitting element through a power source line, and wherein a brightness increase of the light emitting element caused by a temperature change of the light emitting material interposed between the first electrode and the second electrode is suppressed by using the monitoring light emitting element. ### Claim 14 A display device comprising: a pixel portion formed over a substrate, the pixel portion having a light emitting element, wherein the light emitting element comprises a first electrode and a second electrode with a light emitting material interposed therebetween; a monitoring light emitting element electrically connected to the light emitting element through a power source line; and a plurality of constant current sources, wherein the monitoring light emitting element comprises the light emitting material interposed between a pair of electrodes, wherein any one of the plurality of constant current sources is electrically connected to the monitoring light emitting element through a switch, wherein a brightness change of the light emitting element caused by a temperature change of the light emitting material interposed between the first electrode and the second electrode is suppressed by using the monitoring light emitting element, and wherein a current flowing into the monitoring light emitting element is equal to a current flowing into the light emitting element. ### Claim 15 A display device comprising: a pixel portion formed over a substrate, the pixel portion having a light emitting element, wherein the light emitting element comprises a first electrode and a second electrode with a light emitting material interposed therebetween; a monitoring light emitting element electrically connected to the light emitting element through a power source line; and a plurality of constant current sources, wherein the monitoring light emitting element comprises the light emitting material interposed between a pair of electrodes, wherein any one of the plurality of constant current sources is electrically connected to the monitoring light emitting element through a switch, wherein a brightness increase of the light emitting element caused by a temperature change of the light emitting material interposed between the first electrode and the second electrode is suppressed by using the monitoring light emitting element, and wherein a current flowing into the monitoring light emitting element is equal to a current flowing into the light emitting element. ### Claim 16 A display device comprising: a pixel portion formed over a substrate, the pixel portion having a light emitting element, wherein the light emitting element comprises a first electrode and a second electrode with a light emitting material interposed therebetween; and a buffer amplifier, a monitoring light emitting element, and a plurality of constant current sources, wherein the monitoring light emitting element comprises the light emitting material interposed between a pair of electrodes, wherein the monitoring light emitting element and an input terminal of the buffer amplifier are electrically connected to any one of the plurality of constant current sources through a switch, wherein an output terminal of the buffer amplifier is electrically connected to the light emitting element, wherein a brightness change of the light emitting element caused by a temperature change of the light emitting material interposed between the first electrode and the second electrode is suppressed by using the monitoring light emitting element, and wherein a current flowing into the monitoring light emitting element is equal to a current flowing into the light emitting element. ### Claim 17 A display device comprising: a pixel portion formed over a substrate, the pixel portion having a light emitting element, wherein the light emitting element comprises a first electrode and a second electrode with a light emitting material interposed therebetween; and a buffer amplifier, a monitoring light emitting element, and a plurality of constant current sources, wherein the monitoring light emitting element comprises the light emitting material interposed between a pair of electrodes, wherein the monitoring light emitting element and an input terminal of the buffer amplifier are electrically connected to any one of the constant current sources through a switch, wherein an output terminal of the buffer amplifier is electrically connected to the light emitting element, wherein a brightness increase of the light emitting element caused by a temperature change of the light emitting material interposed between the first electrode and the second electrode is suppressed by using the monitoring light emitting element, and wherein a current flowing into the monitoring light emitting element is equal to a current flowing into the light emitting element. ### Claim 18 A display device comprising: a pixel portion formed over a substrate, the pixel portion having a light emitting element, wherein the light emitting element comprises a first electrode and a second electrode with a light emitting material interposed therebetween; and a buffer amplifier, a monitoring light emitting element, and a plurality of constant current sources, wherein the monitoring light emitting element comprises the light emitting material interposed between a pair of electrodes, wherein the monitoring light emitting element and an input terminal of the buffer amplifier are electrically connected to any one of the plurality of constant current sources through a switch, wherein an output terminal of the buffer amplifier is electrically connected to the light emitting element through a power source line, wherein a brightness change of the light emitting element caused by a temperature change of the light emitting material interposed between the first electrode and the second electrode is suppressed by using the monitoring light emitting element, and wherein a current flowing into the monitoring light emitting element is equal to a current flowing into the light emitting element. ### Claim 19 A display device comprising: a pixel portion formed over a substrate, the pixel portion having a light emitting element, wherein the light emitting element comprises a first electrode and a second electrode with a light emitting material interposed therebetween; and a buffer amplifier, a monitoring light emitting element, and a plurality of constant current sources, wherein the monitoring light emitting element comprises the light emitting material interposed between a pair of electrodes, wherein the monitoring light emitting element and an input terminal of the buffer amplifier are electrically connected to any one of the plurality of constant current sources through a switch, wherein an output terminal of the buffer amplifier is electrically connected to the light emitting element through a power source line, wherein a brightness increase of the light emitting element caused by a temperature change of the light emitting material interposed between the first electrode and the second electrode is suppressed by using the monitoring light emitting element, and wherein a current flowing into the monitoring light emitting element is equal to a current flowing into the light emitting element.