# US 9,439,265 B1 · Method of driving pixel element in active matrix display > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,439,265 B1 - Document ID: US9439265B1 - Status: Granted - Kind: B1 - Application number: 13/745,849 - Filed: 2013-01-20 - Granted: 2016-09-06 - Earliest claimed: 2013-01-20 - Applicants: Nongqiang Fan - Inventors: Nongqiang Fan - Web page: https://patentgrep.com/patent/US9439265B1 ## CPC - G09G 3/3233: with pixel circuitry controlling the current through the light-emitting element - H05B 47/00: Circuit arrangements for operating light sources in general, i.e. where the type of light source is not relevant - G09G 2300/0819: used for counteracting undesired variations, e.g. feedback or autozeroing - G09G 2300/0842: forming a memory circuit, e.g. a dynamic memory with one capacitor - G09G 2300/088: using a non-linear two-terminal element - G09G 2320/043: Preventing or counteracting the effects of ageing - G09G 2320/045: Compensation of drifts in the characteristics of light emitting or modulating elements - 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) - H05B: ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL ## Abstract A method of driving a pixel element an active matrix display. The method inducing a change of the bias voltage of the first transistor towards its threshold voltage with an essentially constant current provided from the semiconductor channel of a field effect transistor to cause the bias voltage of the first transistor linearly depend upon the time lapse since the light-emitting element starts to emit light. The method also includes terminating light emitted from the light-emitting element after the bias voltage of the first transistor becomes substantially close to the threshold voltage of the first transistor. ## Claims ### Claim 1 A method of driving a pixel element in a matrix of pixel elements of an active matrix display, the pixel element comprising (1) a first capacitive element, (2) a first transistor having a semiconductor channel, a first terminal of the semiconductor channel of the first transistor being electrically connected to a first terminal of the first capacitive element, and (3) a light-emitting element, wherein the first transistor is biased at a bias voltage between the gate of the first transistor and a first terminal of the semiconductor channel of the first transistor, the active matrix display comprising an array of column conducting lines and an array of row conducting lines crossing the array of column conducting lines, the method comprising: setting the bias voltage of the first transistor to a value that is substantially close to a threshold voltage of the first transistor by changing a voltage across the first capacitive element with a current passing through the first transistor; setting the bias voltage of the first transistor to a value that is different from the threshold voltage of the first transistor while substantially maintaining the voltage across the first capacitive element; inducing a change of the bias voltage of the first transistor towards the threshold voltage thereof with an essentially constant current provided from the semiconductor channel of a field effect transistor to cause the bias voltage of the first transistor linearly depend upon the time, the essentially constant current being independent of the intensity of light emitted by the light-emitting element while the light-emitting element is emitting light; and terminating light emitted from the light-emitting element after said inducing a change of the bias voltage of the first transistor causes the bias voltage of the first transistor becoming substantially close to the threshold voltage of the first transistor. ### Claim 2 (depends on 1) The method of claim 1, wherein the pixel element further comprises a second transistor having a semiconductor channel operationally coupled to a second terminal of the semiconductor channel of the first transistor. ### Claim 3 (depends on 2) The method of claim 2, wherein the changing a voltage across the first capacitive element comprises: (1) driving the semiconductor channel of the first transistor to a low-impedance state and (2) driving the semiconductor channel of the second transistor to a low-impedance state. ### Claim 4 (depends on 1) The method of claim 1, wherein the setting the bias voltage of the first transistor to a value that is substantially close to a threshold voltage of the first transistor by changing a voltage across the first capacitive element comprises: (1) setting a voltage on the gate of the first transistor at a first gate-voltage value and (2) setting a voltage at a second terminal of the first capacitive element at a first reference-voltage value. ### Claim 5 (depends on 4) The method of claim 4, wherein the setting the bias voltage of the first transistor to a value that is different from the threshold voltage of the first transistor comprises: (1) setting the voltage on the gate of the first transistor at a second gate-voltage value and (2) setting the voltage at the second terminal of the first capacitive element at a second reference-voltage value. ### Claim 6 (depends on 1) The method of claim 1, wherein the changing a voltage across the first capacitive element comprises: (1) driving the semiconductor channel of the first transistor to a low-impedance state and (2) enabling current flow into or flow from the second terminal of the semiconductor channel of the first transistor. ### Claim 7 (depends on 1) The method of claim 1, wherein the substantially maintaining the voltage across the first capacitive element comprises: driving the semiconductor channel of the first transistor to a high-impedance state. ### Claim 8 (depends on 1) The method of claim 1, wherein the substantially maintaining the voltage across the first capacitive element comprises: substantially preventing current flow into or flow from the second terminal of the semiconductor channel of the first transistor. ### Claim 9 A method of driving a pixel element in a matrix of pixel elements of an active matrix display, the pixel element comprising (1) a first capacitive element, (2) a first transistor having a semiconductor channel, and (3) a light-emitting element, wherein the first transistor is biased at a bias voltage between the gate of the first transistor and a first terminal of the semiconductor channel of the first transistor, the active matrix display comprising an array of column conducting lines and an array of row conducting lines crossing the array of column conducting lines, the method comprising: changing the bias voltage of the first transistor to a value that is different from a threshold voltage of the first transistor; emitting light from the light-emitting element while changing the bias voltage of the first transistor towards the threshold voltage thereof with an essentially constant current provided from the semiconductor channel of a field effect transistor to cause the bias voltage of the first transistor linearly depend upon the time lapse since the light-emitting element starts to emit light, the essentially constant current being independent of the intensity of light emitted by the light-emitting element; and terminating light emitted from the light-emitting element after the bias voltage of the first transistor becomes substantially close to the threshold voltage of the first transistor. ### Claim 10 (depends on 9) The method of claim 9, further comprising: setting the bias voltage of the first transistor to a value that is substantially close to the threshold voltage of the first transistor before said changing the bias voltage of the first transistor to a value that is different. ### Claim 11 A method of driving a pixel element in a matrix of pixel elements of an active matrix display, the pixel element comprising (1) a first capacitive element, (2) a first transistor having a semiconductor channel, and (3) a light-emitting element, wherein the first transistor is biased at a bias voltage between the gate of the first transistor and a first terminal of the semiconductor channel of the first transistor, the active matrix display comprising an array of column conducting lines and an array of row conducting lines crossing the array of column conducting lines, the method comprising: changing the bias voltage of the first transistor to a value that is different from a threshold voltage of the first transistor; inducing a change of the bias voltage of the first transistor towards the threshold voltage thereof with an essentially constant current provided from the semiconductor channel of a field effect transistor to cause the bias voltage of the first transistor linearly depend upon the time, the essentially constant current being independent of the intensity of light emitted by the light-emitting element while the light-emitting element is emitting light; and terminating light emitted from the light-emitting element after said inducing a change of the bias voltage of the first transistor causes the bias voltage of the first transistor becoming substantially close to the threshold voltage of the first transistor. ### Claim 12 (depends on 11) The method of claim 11, wherein said changing the bias voltage of the first transistor comprises: changing the bias voltage of the first transistor to a value that is different from a threshold voltage of the first transistor after a step of setting the bias voltage of the first transistor to a value that is substantially close to the threshold voltage of the first transistor by changing a voltage across the first capacitive element with a current passing through the first transistor. ### Claim 13 (depends on 11) The method of claim 11, wherein said terminating light emitted from the light-emitting element comprises: sensing a current passing through the semiconductor channel of the first transistor with a high impedance component while the light-emitting element is emitting light. ### Claim 14 (depends on 11) The method of claim 11, wherein said terminating light emitted from the light-emitting element comprises: inducing a voltage change at the gate of a supplementary transistor with a change of the current passing through the semiconductor channel of the first transistor. ### Claim 15 (depends on 11) The method of claim 11, wherein said terminating light emitted from the light-emitting element comprises: inducing a voltage change at the gate of a supplementary transistor with a voltage change across a high impedance component caused by a change of the current passing through the semiconductor channel of the first transistor. ### Claim 16 (depends on 15) The method of claim 15, wherein the light-emitting element is electrically connected with the semiconductor channel of the supplementary transistor for causing the current passing through the light-emitting element depend upon the voltage at the gate of a supplementary transistor. ### Claim 17 (depends on 15) The method of claim 15, wherein the light-emitting element is electrically connected with the semiconductor channel of the supplementary transistor for causing the voltage across the light-emitting element depend upon the voltage at the gate of the supplementary transistor. ### Claim 18 (depends on 11) The method of claim 11, and wherein said terminating light emitted from the light-emitting element comprises: inducing a voltage change across the light-emitting element with a change of the current passing through the semiconductor channel of the first transistor. ### Claim 19 (depends on 11) The method of claim 11, and wherein said terminating light emitted from the light-emitting element comprises: inducing a voltage change across the light-emitting element with a voltage change across a high impedance component caused by a change of the current passing through the semiconductor channel of the first transistor. ### Claim 20 (depends on 11) The method of claim 11, wherein: the bias voltage of the first transistor linearly depend upon the time lapse since the light-emitting element starts to emit light at least during substantially entire time period that the light-emitting element is emitting light.