EL Display Device Gray-Level Control via Subframe Timing
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Solution Overview
Problem
Active matrix organic EL display devices face challenges in efficiently controlling luminance variations and threshold voltage changes, leading to irregularities in pixel luminance, which existing technologies have not adequately addressed.
Innovation Solution
The EL display device employs an array of pixel circuits with drive transistors that apply current to organic EL elements, a driver circuit for signal control, and an image signal processing circuit with an N-bit D/A converter, dividing the image display period into subframes for high and low gray-level signals, ensuring a longer light emission period in the first subframe compared to the second subframe, allowing for efficient gray-level display using an N-bit D/A converter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an N-bit D/A converter is used for gray-level display, then display precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent divides the gray-level display into two stages: a first stage using an N-bit D/A converter for coarse gray-level control, and a second stage using a separate M-bit D/A converter for fine gray-level adjustment. This segmentation allows the system to achieve (N+M)-bit display precision while using simpler, lower-cost D/A converters instead of requiring a single complex (N+M)-bit D/A converter.
2Manufacturing precision
If light emission period is extended for better display quality, then image quality is improved, but energy consumption increases
Solution Approach 1:
The patent implements periodic action by dividing the light emission period into two distinct phases: a first light emission period for displaying the image signal, and a second light emission period for displaying the correction signal. This periodic structure allows the system to maintain display quality while controlling energy consumption through optimized timing and signal sequences.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enables effective gray-level display of N+M bits using an N-bit D/A converter, reducing costs and improving image quality by controlling light emission periods, thus addressing luminance irregularities and threshold voltage changes.
Implementation Method 1
an organic EL element that emits light in response to applied current
Data Source
AI summary
Provided is an EL display device that includes: an EL display panel including an array of a plurality of pixel circuits each having a drive transistor that applies a current to an organic EL element; a driver circuit that applies, to each of the pixel circuits, a signal in response to an image signal and a signal for selecting pixel circuits that are expected to emit light; and an N-bit D/A converter. An image display period in a single frame is divided into a first subframe and a second subframe, the first subframe performing display by light emission based on a gray-level signal of high N bits, the second subframe performing display by light emission based on a gray-level signal of low M bits (where M satisfies M<N), and light emission period L1 in the first subframe and light emission period L2 in the second subframe are controlled such that a relation therebetween satisfies L1>L2.