Dual-Driver Pixel Circuit for Display Chromaticity Stability
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Solution Overview
Problem
Existing display devices face challenges in achieving high contrast ratios and accurate gradation control due to low light emission efficiency and significant variations in light emission chromaticity when using self-luminous light-emitting elements like LEDs, particularly in low current regions, which affect the reproducibility of gradations and display quality.
Innovation Solution
The display device employs a matrix of pixel units with a dual-driver system, where a low-gradation driver and a high-gradation driver control the light-emitting elements based on specific gradation value ranges, using composite drive signals to reduce discontinuous changes in current and emission wavelength, thereby stabilizing luminance and chromaticity across a wide luminance range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single driver controls the light-emitting element across all gradation values, then the device complexity is low, but the light emission chromaticity varies significantly and gradation accuracy deteriorates
Solution Approach 1:
The pixel circuit is divided into two separate driver circuits: a first driver for low gradation values (0-127) and a second driver for high gradation values (128-255). Each driver is optimized for its specific gradation range, allowing precise control and stable chromaticity characteristics in each region. This segmentation resolves the contradiction by achieving high gradation accuracy through specialized drivers while keeping each individual driver relatively simple in structure.
2Illumination intensity
If the light-emitting element is driven at low current to achieve high contrast ratios, then the power consumption is low, but the light emission efficiency decreases and chromaticity variations increase
Solution Approach 1:
The patent applies different drive strategies to different gradation ranges. For low gradation values where high contrast is needed, the first driver uses optimized current control to maintain acceptable efficiency. For high gradation values, the second driver provides sufficient current for high luminance output. This local optimization resolves the contradiction by matching the drive mode to the specific luminance requirement, achieving high contrast ratios in dark regions without sacrificing overall light emission efficiency.
3Illumination intensity
If the current magnitude is varied to control luminance, then the luminance control is simple, but the emission wavelength changes discontinuously affecting chromaticity
Solution Approach 1:
By segmenting the control into two drivers with different operating characteristics, the patent achieves smooth chromaticity transitions. The first driver operates in a current range that maintains stable chromaticity for low luminance, while the second driver handles high luminance with its own optimized current characteristics. The boundary region (gradations 96-160) allows overlapping operation to ensure continuous and smooth chromaticity transition, resolving the contradiction between simple luminance control and chromaticity stability.
4Stability of the object's composition
If a dual-driver system is used to stabilize chromaticity across gradation ranges, then the chromaticity variation is reduced, but the device complexity increases
Solution Approach 1:
The patent changes the operational parameters of the two drivers to complement each other. The first driver is optimized for low-current operation with specific current magnitude and pulse width characteristics, while the second driver is optimized for high-current operation. By carefully selecting and adjusting these parameters, the system achieves stable chromaticity across the full gradation range while keeping the additional circuit complexity manageable through parameter optimization rather than complex circuit architectures.
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 approach enhances the display quality by maintaining high contrast ratios and reducing light emission chromaticity variations, allowing for the precise representation of gradations and improved image fidelity, especially in high-definition images.
Implementation Method 1
Each pixel unit of the plurality of pixel units includes a light-emitting element... The light-emitting element has luminance changeable in accordance with a magnitude of a current and an input period of the current
Data Source
AI summary
A display device includes a matrix of pixel units each including a light-emitting element and a pixel circuit that causes the light-emitting element to emit light. The pixel circuit includes a first driver that drives the light-emitting element in response to the gradation value of an image in a range of gradation values less than or equal to a first boundary value and does not drive the light-emitting element in response to the image gradation value in a range of gradation values greater than the first boundary value, and a second driver that does not drive the light-emitting element in response to the image gradation value in a range of gradation values less than or equal to a second boundary value and drives the light-emitting element in response to the image gradation value in a range of gradation values greater than the second boundary value.