Method and system for programming and driving active matrix light emitting device pixel having a controllable supply voltage
First Claim
1. A method of programming a pixel circuit that drives a current-driven organic light emitting device independent of a threshold voltage of a drive transistor connected in series to the organic light emitting device, the pixel circuit further including a discharge transistor connected between the organic light emitting device and a node of the pixel circuit, the method comprising:
- adjusting during a programming cycle a controllable voltage supply to a compensation voltage sufficient to turn off the organic light emitting device;
in a first operating cycle of the programming cycle, selecting a select line, to turn on a selection transistor coupled to the drive transistor, for applying a reference voltage to the drive transistor through the selection transistor;
in the first operating cycle, applying to a data line connected to the selection transistor a voltage that exceeds a programming voltage to be applied to the drive transistor;
responsive to the adjusting, allowing the node of the pixel circuit to charge or discharge through the drive transistor, via the discharge transistor, until the drive transistor turns off, thereby establishing the threshold voltage of the drive transistor across the drive transistor; and
in a further operating cycle of the programming cycle following the first operating cycle, selecting the select line to turn on the selection transistor for applying a programming voltage from the data line to the drive transistor through the selection transistor, thereby establishing a fixed voltage applied to the drive transistor according to both the threshold voltage and the applied programming voltage, wherein the programming voltage is lower than the reference voltage.
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Accused Products
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
17 Claims
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1. A method of programming a pixel circuit that drives a current-driven organic light emitting device independent of a threshold voltage of a drive transistor connected in series to the organic light emitting device, the pixel circuit further including a discharge transistor connected between the organic light emitting device and a node of the pixel circuit, the method comprising:
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adjusting during a programming cycle a controllable voltage supply to a compensation voltage sufficient to turn off the organic light emitting device; in a first operating cycle of the programming cycle, selecting a select line, to turn on a selection transistor coupled to the drive transistor, for applying a reference voltage to the drive transistor through the selection transistor; in the first operating cycle, applying to a data line connected to the selection transistor a voltage that exceeds a programming voltage to be applied to the drive transistor; responsive to the adjusting, allowing the node of the pixel circuit to charge or discharge through the drive transistor, via the discharge transistor, until the drive transistor turns off, thereby establishing the threshold voltage of the drive transistor across the drive transistor; and in a further operating cycle of the programming cycle following the first operating cycle, selecting the select line to turn on the selection transistor for applying a programming voltage from the data line to the drive transistor through the selection transistor, thereby establishing a fixed voltage applied to the drive transistor according to both the threshold voltage and the applied programming voltage, wherein the programming voltage is lower than the reference voltage. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A display system comprising:
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a pixel circuit including a drive transistor, a light emitting device, a switch transistor, and a discharge transistor, the drive transistor having a first terminal connected to the light-emitting device, the drive transistor having a threshold voltage that shifts during operation of the drive transistor, the switch transistor coupled between a data line and the discharge transistor, and the discharge transistor having a first terminal connected to the first terminal of the drive transistor and a second terminal connected to a gate terminal of the drive transistor, such that, during a compensation cycle of a programming cycle while the discharge transistor is selected via a select line and while a high voltage, which exceeds a programming voltage to be applied to the drive transistor through the switch transistor, is applied to the data line, the discharge transistor is allowed to charge or discharge a node of the pixel circuit, through the drive transistor, via the discharge transistor, until the drive transistor turns off, thereby establishing the threshold voltage of the drive transistor between the gate terminal and the first terminal of the drive transistor; during an operating cycle of the programming cycle following the compensation cycle, turning on the switch transistor via the select line for applying the programming voltage from the data line to the drive transistor through the switch transistor, thereby establishing a fixed voltage applied to the drive transistor according to both the threshold voltage and the applied programming voltage, wherein the programming voltage is lower than the high voltage; and a controllable power supply connected to the light-emitting device for supplying the drive transistor with a voltage that is adjusted to a compensation voltage sufficient to turn off the light emitting device, during the compensation cycle. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17)
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Specification