Display Driver Dimming Control via Variable Reference Duties
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Solution Overview
Problem
Current display devices face challenges in achieving efficient dimming control, particularly with inorganic light emitting elements, as they struggle to minimize dynamic false contours and maximize expressible dimming luminance while maintaining image quality.
Innovation Solution
A display device and dimming driving method that divide the frame period into multiple cycle periods, each with varying subfields and reference duties based on a dimming signal, allowing for independent control of emission on-duties and current flow through the use of a display driver with an oscillator and on-duty controller to generate PWM signals and adjust PAM data voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single reference duty is used for all cycle periods, then the device complexity is reduced, but the expressible dimming luminance is limited and dynamic false contours cannot be minimized
Solution Approach 1:
The frame period is divided into multiple cycle periods (first, second, third, fourth cycle periods), and each cycle period is assigned a different reference duty (first, second, third, fourth reference duties). This segmentation allows the display driver to control luminance at different granularities across time, expanding the expressible dimming luminance range while managing complexity through temporal division
Solution Approach 2:
The reference duty is made dynamic by varying it across different cycle periods within the same frame period. The display driver independently determines different reference duties for different cycle periods based on dimming requirements, enabling adaptive luminance control that responds to changing display conditions and minimizes dynamic false contours
2Illumination intensity
If the emission on-duty is increased to improve visibility, then the image quality is improved, but the dynamic false contours become more pronounced
Solution Approach 1:
The display driver employs periodic subfield driving within each cycle period, where emission and non-emission periods are alternated in a structured sequence. By carefully designing the periodic pattern of subfields with different emission on-duties across multiple cycle periods, the system achieves adequate visibility while distributing the luminance output over time to minimize dynamic false contours
Solution Approach 2:
The system changes the emission on-duty parameter dynamically across different cycle periods. Instead of maintaining a constant high emission on-duty that would cause false contours, the display driver varies the emission on-duty of subfields in different cycle periods, creating a temporal distribution of luminance that reduces perceptible false contours while maintaining overall visibility
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 effectively reduces dynamic false contours and expands expressible dimming luminance by varying the reference duty of cycle periods, enhancing the display's ability to control luminance and maintain image quality.
Implementation Method 1
an oscillator configured to output a clock signal having a preset frequency
Implementation Method 2
configured to generate PWM signals respectively having the first to fourth reference duties based on counted value of the clock signal
Implementation Method 3
a voltage generator configured to generate a PAM data voltage supplied to the pixel in writing periods of the first to eighth subfields
Data Source
AI summary
A display device comprises a pixel configured to be driven in cycle periods during a frame period defined by a vertical start signal, and a display driver configured to divide a cycle period into subfields for driving, configured to control an amount of current flowing through the pixel and to control emission on-duties of the subfields, and configured to independently determine, for the cycle period, a reference duty that is a minimum emission on-duty set in the cycle period based on a dimming signal.