# US 7,609,234 B2 · Pixel circuit and driving method for active matrix organic light-emitting diodes, and display using the same > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,609,234 B2 - Document ID: US7609234B2 - Status: Granted - Kind: B2 - Application number: 11/232,819 - Filed: 2005-09-22 - Published: 2006-06-22 - Granted: 2009-10-27 - Earliest claimed: 2004-12-16 - Assignees: Korea Advanced Institute of Science and Technology - Inventors: Gyu-Hyeong Cho; Young-Suk Son; Sang-Kyung Kim; Min-Chul Lee - Web page: https://patentgrep.com/patent/US7609234B2 ## CPC - G09G 3/3233: with pixel circuitry controlling the current through the light-emitting element - G09G 3/3258: with pixel circuitry controlling the voltage across the light-emitting element - G09G 3/2014: {by modulation of the duration of a single pulse during which the logic level remains constant} - G09G 2300/0842: forming a memory circuit, e.g. a dynamic memory with one capacitor - 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 - G09G 2310/0259: with use of an analog or digital ramp generator in the column driver or in the pixel circuit - G09G 2310/0297: Special arrangements with multiplexing or demultiplexing of display data in the drivers for data electrodes, in a pre-processing circuitry delivering display data to said drivers or in the matrix panel, e.g. multiplexing plural data signals to one D/A converter or demultiplexing the D/A converter output to multiple columns - G09G 2310/066: Waveforms comprising a gently increasing or decreasing portion, e.g. ramp - G09G 2320/0233: Improving the luminance or brightness uniformity across the screen - 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) ## Abstract Disclosed herein are a pixel circuit and driving method for active matrix Organic Light-emitting Diodes (OLEDs), and a display using the same. The pixel circuit includes a Voltage Control Current Source (VCCS), a high gain amplifier, a storage capacitor, and first and second switches. The VCCS is configured to drive OLEDs. The high gain amplifier is configured such that the control input signal of the VCCS causes the VCCS to be placed in an ON or OFF state. The storage capacitor is located between the input terminal of the high gain amplifier and a data line so as to assign the ON-time of the VCCS. The first and second switches are configured to be controlled through a scan line so as to store voltage in the storage capacitor and control the light-emitting time of the OLEDs, and are formed the input terminal of the high gain amplifier and the input terminal of the VCCS, respectively. ## Claims ### Claim 1 A pixel circuit for active matrix Organic Light-emitting Diodes (OLEDs) comprising: a Voltage Control Current Source (VCCS) configured to drive the OLEDs; a high gain amplifier configured such that a control input signal of the VCCS causes the VCCS to be placed in an ON or OFF state; a storage capacitor located between an input terminal of the high gain amplifier and a data line so as to assign ON-time of the VCCS; and a first switch configured to be controlled through a scan line so as to store the voltage in the storage capacitor and control light-emitting time of the OLEDs, the first switch having one terminal connected to ground (GND) and the other terminal connected to an input terminal of the high gain amplifier; a second switch configured to be controlled through the scan line so as to store voltage in the storage capacitor and control light-emitting time of the OLEDs, the second switch having one terminal connected to the output terminal of the high gain amplifier and the other terminal connected to a power source. ### Claim 2 (depends on 1) The pixel circuit as set forth in claim 1, wherein the VCCS is implemented using a P-channel Thin Film Transistor (TFT), the high gain amplifier is implemented using a N-channel TFT, and each of the first and second switches is implemented using a P-channel TFT. ### Claim 3 (depends on 1) The pixel circuit as set forth in claim 1, wherein the VCCS is implemented using an N-channel TFT, the high gain amplifier is implemented using a P-channel TFT, and each of the first and second switches is implemented using an N-channel TFT. ### Claim 4 A method of driving a pixel circuit for active matrix OLEDs, comprising the step of using a sawtooth wave as a data line signal that controls a light-emitting period, so as to use a scan line not only as a control signal line for selecting a arbitrary pixel during data programming for indicating a gray level of the pixel but also as a reset control signal line, wherein the pixel circuit comprises a Voltage Control Current Source (VCCS) configured to drive the OLEDs; a high gain amplifier configured such that a control input signal of the VCCS causes the VCCS to be placed in an ON or OFF state; a storage capacitor located between an input terminal of the high gain amplifier and a data line so as to assign ON-time of the VCCS; a first switch configured to be controlled through a scan line so as to store the voltage in the storage capacitor and control light-emitting time of the OLEDs, the first switch having one terminal connected to ground (GND) and the other terminal connected to an input terminal of the high gain amplifier; and a second switch configured to be controlled through the scan line so as to store voltage in the storage capacitor and control light-emitting time of the OLEDs, the second switch having one terminal connected to the output terminal of the high gain amplifier and the other terminal connected to a power source. ### Claim 5 (depends on 4) The method as set forth in claim 4, wherein a gamma correction is performed by a variety of rising functions at a rising time of the sawtooth wave. ### Claim 6 (depends on 5) The method as set forth in claim 5, wherein the gamma correction is performed using different Red (R), Green (G), Blue (B) when the variety of rising functions are applied at the rising time of the sawtooth wave. ### Claim 7 A display using a pixel circuit for active matrix OLEDs, comprising: a plurality of pixel circuits constructed in an array form, each of the pixel circuits comprising a VCCS configured to drive the OLEDs, a high gain amplifier configured to cause control input signals of the VCCS to be placed in an off state or an on state, and a storage capacitor located between an input terminal of the high gain amplifier and a data line so as to assign ON-time of the VCCS, a first switch configured to be controlled through a scan line so as to store the voltage in the storage capacitor and control light-emitting time of the OLEDs, the first switch having one terminal connected to ground (GND) and the other terminal connected to an input terminal of the high gain amplifier; a second switch configured to be controlled through the scan line so as to store voltage in the storage capacitor and control light-emitting time of the OLEDs, the second switch having one terminal connected to the output terminal of the high gain amplifier and the other terminal connected to a power source; multiplexers connected to respective data lines; and a sawtooth wave generator connected to the data lines via the multiplexers; wherein a light-emitting period of a pixel connected to the data line is controlled using the sawtooth wave generator. ### Claim 8 (depends on 7) The display as set forth in claim 7, wherein the multiplexers, which are connected to correspond to the data line, are classified according to R, G or B, the sawtooth wave generator is shared by the multiplexers, and different rising functions are applied to a sawtooth wave output from the sawtooth wave generator, so that different R, G and B gamma corrections are performed. ### Claim 9 (depends on 1) The pixel circuit of claim 1, wherein the circuit has only one capacitor, and wherein the only one capacitor is the storage capacitor. ### Claim 10 (depends on 4) The method of claim 4, wherein the circuit has only one capacitor, and wherein the only one capacitor is the storage capacitor. ### Claim 11 (depends on 7) The display of claim 7, wherein the circuit has only one capacitor, and wherein the only one capacitor is the storage capacitor.