US 6,188,375 B1Granted

Pixel drive circuit and method for active matrix electroluminescent displays

AssigneeAllied-Signal Inc.

InventorDanny R. Kagey

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Abstract

An AMEL display is formed and operated in a manner to provide enhanced gray scale or color operation. The AMEL display is operated over consecutive illumination frames which are partitioned into a plurality of passes. The desired illumination intensity for a given pixel during each illumination frame is determined and the pixel is activated for a substantially equal duration in each pass to provide the desired illumination level for each frame. Each pass has an associated illumination profile signal composed of a plurality of discrete steps for selectively passing a number of illumination pulses to each active EL cell in the display in accordance with a pixel activation voltage loaded into each active EL cell. The pixel activation voltage and illumination profiles cooperate to distribute the number of illumination pulses in a substantially equal fashion in each pass of an illumination frame. Pixel driver circuits are disclosed for operating the pixel in accordance with the disclosed illumination methods.

Claims2

Dependent claims

A method of operating a pixel in an active electroluminescent matrix display for desired gray scale operation, said pixel including a first transistor coupled to an associated data line and to a select line, a second transistor connected to said first transistor, a load capacitor connected to both said first and said second transistors, and an electroluminescent cell connected to said second transistor, said method comprising the steps of:

dividing an illumination frame for said pixel into a plurality of passes, each of said passes including a load time period and an illumination time period;
applying pixel activation voltages to the data and select lines to load a voltage on said load capacitor during load time periods in each of said passes;
and
applying an illumination profile signal across said capacitor and said electroluminescent cell during illumination time periods in each of said passes, said illumination profile signals each including a discrete number of illumination profile states, said number being less than the number of possible gray scale states;
said illumination frame for said pixel being divided into three passes, each of said passes including thirty illumination pulses, and each illumination profile signal including six illumination profile states.

2 more elements

Dependencies are inferred from the claim text.