Threshold voltage compensation method for electroluminescent display devices
AssigneeKoninklijke Philips Electronic, N.V.
InventorMark Childs
Life of this patent
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Abstract
An active matrix electroluminescent display device has a shorting transistor (30) connected between the gate and drain of the drive transistor (22). Means (42) is provided for measuring a voltage on the data line (6). The shorting transistor (30) can be used to discharge the voltage on the gate of the drive transistor (22) until it switches off. By storing the resultant voltage on the data line (6) through an address transistor (16), the data line is used as one of the control/measurement lines for the threshold measurement.
Claims13
An active matrix electroluminescent display device comprising an array of display pixels, each pixel comprising:
- an electroluminescent (EL) display element (2);
- a drive transistor (22) for driving a current through the display element (2);
- an address transistor (16) for providing a pixel drive signal from a data line to the gate of the drive transistor (22);
- and
- a shorting transistor (30) connected between the gate and drain of the drive transistor,
- wherein the display device further comprises means (42) for measuring a voltage on the data line.
A method of addressing the pixels of an active matrix electroluminescent display device, comprising an electroluminescent (EL) display element (2) and a drive transistor (22) for driving a current through the display element (2), the method comprising:
- disabling the display element (2);
- applying a first voltage to a data line (6);
- driving a current through the drive transistor (22), through a shorting transistor (30) connected between the gate and drain of the drive transistor and through an address transistor (16) connected between the gate of the drive transistor and the data line (6);
- allowing the data line (6) electrically to float;
- measuring a voltage on the data line (6);
- and
- modifying a data voltage to be applied to the drive transistor (22) using the voltage measured on the data line.
Dependencies are inferred from the claim text.