Method and system for programming and driving active matrix light emitting device pixel having a controllable supply voltage
First Claim
Patent Images
1. A display system comprising:
- a pixel circuit including a drive transistor, a storage capacitor, one or more switch transistors, and a light emitting device, the drive transistor having a terminal connected to the light emitting device, the drive transistor having a threshold voltage that shifts during operation of the drive transistor;
a controllable power supply connected to a terminal of the drive transistor other than the one connected to the light emitting device for supplying the pixel circuit with a compensating voltage or with an operating voltage;
a voltage driver for supplying a programming voltage to the pixel circuit via the one or more switch transistors along a data line so as to program the pixel circuit to emit light according to display information; and
a controller configured to operate the controllable power supply, the voltage driver, and one or more select lines that control the one or more switch transistors, such that;
in response to one of the one or more select lines being activated, the compensating voltage is applied to the light emitting device, via the drive transistor, to turn off the light emitting device,in response to applying the compensation voltage, setting the data line to a nonzero reference voltage,responsive to setting the data line to the nonzero reference voltage, the storage capacitor is allowed to charge or discharge, through the drive transistor, until the drive transistor turns off, while the one of the one or more select lines remain activated such that the threshold voltage of the drive transistor is established across the drive transistor,the programming voltage is applied to the pixel circuit, thereby establishing a fixed voltage across the drive transistor that accounts for instabilities in the threshold voltage of the drive transistor, andwherein the controller is configured to operate the pixel circuit to maintain the fixed voltage across the drive transistor on the storage capacitor while turning on the operating voltage during a driving cycle of the pixel circuit, the driving cycle being separate from a programming cycle during which the fixed voltage is established on the storage capacitor.
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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.
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Citations
18 Claims
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1. A display system comprising:
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a pixel circuit including a drive transistor, a storage capacitor, one or more switch transistors, and a light emitting device, the drive transistor having a terminal connected to the light emitting device, the drive transistor having a threshold voltage that shifts during operation of the drive transistor; a controllable power supply connected to a terminal of the drive transistor other than the one connected to the light emitting device for supplying the pixel circuit with a compensating voltage or with an operating voltage; a voltage driver for supplying a programming voltage to the pixel circuit via the one or more switch transistors along a data line so as to program the pixel circuit to emit light according to display information; and a controller configured to operate the controllable power supply, the voltage driver, and one or more select lines that control the one or more switch transistors, such that; in response to one of the one or more select lines being activated, the compensating voltage is applied to the light emitting device, via the drive transistor, to turn off the light emitting device, in response to applying the compensation voltage, setting the data line to a nonzero reference voltage, responsive to setting the data line to the nonzero reference voltage, the storage capacitor is allowed to charge or discharge, through the drive transistor, until the drive transistor turns off, while the one of the one or more select lines remain activated such that the threshold voltage of the drive transistor is established across the drive transistor, the programming voltage is applied to the pixel circuit, thereby establishing a fixed voltage across the drive transistor that accounts for instabilities in the threshold voltage of the drive transistor, and wherein the controller is configured to operate the pixel circuit to maintain the fixed voltage across the drive transistor on the storage capacitor while turning on the operating voltage during a driving cycle of the pixel circuit, the driving cycle being separate from a programming cycle during which the fixed voltage is established on the storage capacitor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method of programming a pixel circuit that drives a current-driven light emitting device independent of a threshold voltage of a drive transistor connected in series to the light emitting device, the drive transistor being connected between the light emitting device and a controllable power supply such that the controllable power supply is not directly coupled to the light emitting device, the method comprising:
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activating a select line to turn on a selection transistor coupled to a gate terminal of the drive transistor; responsive to the activating the select line, adjusting the controllable power supply to a compensating voltage sufficient to turn off the light emitting device while the select line remains active; responsive to the adjusting, applying a nonzero reference voltage to the drive transistor through the selection transistor while the select line remains active; responsive to the adjusting, allowing a node of the pixel circuit to charge or discharge until the drive transistor turns off while the select line remains selected, thereby establishing the threshold voltage of the driving transistor across the drive transistor; responsive to the drive transistor turning off, applying a programming voltage to the drive transistor, thereby establishing a fixed voltage across the drive transistor according to both the threshold voltage of the drive transistor and the applied programming voltage; setting the controllable power supply to an operating voltage; and deselecting the select line to complete the programming cycle and initiate a driving cycle while maintaining the fixed voltage across the drive transistor. - View Dependent Claims (13, 14, 15, 16, 17, 18)
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Specification