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OLED display drive circuits and techniques

A pixel driving circuit, display panel technology, applied in the direction of circuits, static indicators, instruments, etc.

Inactive Publication Date: 2013-11-13
CAMBRIDGE DISPLAY TECH LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0004] For large displays and thus long current programming lines, such small currents present a significant challenge, not least due to the relatively large capacitance associated with such lines

Method used

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  • OLED display drive circuits and techniques
  • OLED display drive circuits and techniques
  • OLED display drive circuits and techniques

Examples

Experimental program
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Embodiment Construction

[0031] The two requirements for OLED displays relate to:

[0032] a. Programming / Settling Time - The requirement for brightness programming within a specified programming time that decreases with increasing resolution. If the programming of brightness is not completed within the specified time, this can result in either loss of grayscale information or loss of contrast or both.

[0033] b. Aging (Vt drift) - the requirement to compensate for drift in Vt (and μ). If unsuccessful, this can reduce brightness and / or cause image retention.

[0034] The main schemes for programming pixel circuits can be divided into voltage programming (VP) and current programming (CP). The voltage programming scheme provides fast programming times, and therefore it is suitable for high resolution displays. But such technology requires additional features to compensate for OLED aging (which changes the brightness-voltage characteristics) and voltage drop on the power line.

[0035] The current p...

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PUM

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Abstract

An active matrix OLED (AMOLED) display panel comprising: a plurality of OLED pixels each having an associated current-programmed pixel drive circuit 180, said pixel drive circuit having a pixel select line SEL and a current programming input for programming an OLED pixel when said pixel select line is active; at least one distributed cascode transistor 202a-d shared between a set of said pixel drive circuits and comprising a set of transistors each having an input connection, an output connection and a control connection, wherein each transistor of said set is in physical proximity to a respective one of said pixel drive circuits and has said output connection connected to said current programming input of said respective one of said pixel drive circuits, wherein said input connections of said transistors of said set are connected together in parallel, said output connections of said transistors of said set are connected together in parallel, and said control connections of said transistors of said set are connected together in parallel, and wherein said parallelâ connected input connections are connected to a common current programming line for said set of said pixel drive circuits.

Description

technical field [0001] The present invention relates to improved pixel driving techniques for organic light emitting diode (OLED) displays. Background technique [0002] It is known to drive OLED displays using an "active matrix" layout in which individual pixels of the display are activated by associated thin film transistors. In one drive technique, an analog current is used to program the drive current of an active-matrix OLED pixel such that the current through the pixel (and thus brightness) is directly proportional to the programmed level. Thus, in a standard current programmed pixel circuit, the data line supplies a current replicated on a 1:1 basis or in a fixed ratio to the output stage. [0003] As OLED displays continue to grow larger, the length of the backplane pixel interconnection increases, and for HDTV (High Definition Television) its length can be on the order of 1 meter. Furthermore, the gamma function yields for such displays a dynamic range of 1000:1 b...

Claims

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Application Information

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IPC IPC(8): G09G3/32
CPCG09G2300/0842G09G3/3241G09G2320/0233G09G2320/0223G09G2310/0218G09G3/3233H10K59/12G09G3/32
Inventor E·史密斯A·兰科夫
Owner CAMBRIDGE DISPLAY TECH LTD
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