METHOD AND SYSTEM FOR PROGRAMMING AND DRIVING ACTIVE MATRIX LIGHT EMITTING DEVICE PIXEL

• US 20110012883A1
• Filed: 08/06/2010
• Published: 01/20/2011
• Est. Priority Date: 12/07/2004
• Status: Active Grant

• Current Assignee: IGNIS Innovation Incorporated
• Original Assignee: IGNIS Innovation Incorporated
• Inventors: Chaji, Gholamreza Reza, Servati, Peyman, Nathan, Arokia
• Granted Patent: US 8,405,587 B2
• Time in Patent Office: Days
• US Class Current: 345/211
• CPC Class Codes: G09G 2300/0465 Improved aperture ratio, e.g. by size reduction of the pixel circuit, e.g. for improving the pixel density or the maximum displayable luminance or brightness
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2300/0852 being a dynamic memory with more than one capacitor
• CPC Class Codes: G09G 2310/0262 The addressing of the pixel, in a display other than an active matrix LCD, involving the control of two or more scan electrodes or two or more data electrodes, e.g. pixel voltage dependent on signals of two data electrodes
• CPC Class Codes: G09G 2310/06 Details of flat display driving waveforms
• CPC Class Codes: G09G 2310/061 for resetting or blanking
• CPC Class Codes: G09G 2320/043 Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 3/3233 with pixel circuitry controlling the current through the light-emitting element
• CPC Class Codes: G09G 3/3258 with pixel circuitry controlling the voltage across the light-emitting element
• CPC Class Codes: G09G 3/3696 Generation of voltages supplied to electrode drivers

Abstract

Method and system for programming and driving active matrix light emitting device pixel is provided. The pixel is a voltage programmed pixel circuit, and has a light emitting device, a driving transistor and a storage capacitor. The pixel has a programming cycle having a plurality of operating cycles, and a driving cycle. During the programming cycle, the voltage of the connection between the OLED and the driving transistor is controlled so that the desired gate-source voltage of a driving transistor is stored in a storage capacitor.

Claims

1-18. -18. (canceled)

19. A method of programming a pixel circuit for maintaining a stable current that drives a current-driven light emitting device (LED) independent of a threshold voltage of a driving transistor connected in series to the LED, the method comprising

selecting a select line, coupled to a gate of the driving transistor, for programming the pixel circuit during a programming cycle,

responsive to the selecting, adjusting a controllable voltage supply to a compensating voltage sufficient to turn off the current-driving LED in the pixel circuit while the select line remains selected,

responsive to turning off the LED, causing the driving transistor to discharge until the driving transistor turns off while the select line remains selected, thereby establishing a fixed voltage across the driving transistor,

responsive to turning off the driving transistor, setting the controllable voltage supply to an operating voltage while maintaining the fixed voltage across the driving transistor during a driving cycle that follows the programming cycle, and

responsive to the setting, deselecting the select line to complete the programming cycle and initiate the driving cycle.

20. A display system comprising

a pixel array including a plurality of pixel circuits and a plurality of lines for operation of the plurality of pixel circuits, each of the pixel circuits including a drive circuit connected to the light-emitting device, said drive circuit including a drive transistor having a threshold voltage V_T that increases as the drive transistor ages, and

a controllable power supply connected to a terminal of said drive transistor for supplying the drive transistor with a voltage that is adjusted to compensate for changes in said threshold voltage V_T as the drive transistor ages, to maintain a stable pixel current.