Current Limiting Circuit for Display Gamma Consistency
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Solution Overview
Problem
Display devices with self-light-emitting pixels face issues in maintaining consistent gamma characteristics between small and large area video displaying, leading to user discomfort due to uneven luminance, especially when displaying white and single colors.
Innovation Solution
A current limiting circuit that calculates a screen power value based on pixel values and adjusts the gain to ensure power consumption remains within a control target, using a gain calculation circuit to set the gain to 1 when the screen power value is within the target, and reducing it when exceeding the target, thereby maintaining consistent gamma characteristics across different display areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If current is limited based on screen power value to control power consumption, then power consumption is reduced, but gamma characteristics become inconsistent between single color and white displaying in large area video displaying
Solution Approach 1:
The patent applies local quality by differentiating the treatment of pixel values based on their magnitude. When maximum pixel value exceeds the first threshold, the system uses a common pixel value for calculation purposes while still applying individual current limiting to each pixel. This localized differentiation allows the system to maintain accurate gamma characteristics for each pixel while controlling overall power consumption.
Solution Approach 2:
The patent changes the parameter used for power calculation from individual pixel values to a common pixel value when maximum pixel value exceeds the threshold. This parameter change allows the system to calculate screen power value accurately without requiring each pixel to maintain full dynamic range, thus controlling power consumption while preserving gamma characteristics through the gain multiplication step.
2Use of energy by stationary object
If current is limited when pixel value is large in large area video displaying, then power consumption is controlled, but luminance becomes constant and fails to reflect video signal faithfully
Solution Approach 1:
The patent performs preliminary action by calculating the screen power value using the common pixel value before applying current limiting to individual pixels. This advance calculation allows the system to determine the appropriate gain factor that will maintain luminance fidelity while controlling power consumption, rather than simply clamping pixel values which would destroy luminance information.
Solution Approach 2:
The patent implements feedback by using the calculated screen power value to determine a gain factor that is then applied to individual pixel values. This feedback mechanism ensures that current limiting is applied in a controlled manner that preserves the relationship between pixel values and luminance, maintaining faithful video signal representation while controlling power consumption.
3Adaptability or versatility
If gamma characteristics are made identical to conventional liquid crystal display devices in small area video displaying, then compatibility is improved, but the same gamma characteristics cause user discomfort in large area video displaying
Solution Approach 1:
The patent applies dynamics by making the gamma characteristics adaptive rather than fixed. The system dynamically adjusts its behavior based on the display area being used: in small area video displaying, it maintains standard gamma characteristics for compatibility, while in large area video displaying, it uses the common pixel value calculation method to maintain luminance consistency. This dynamic adaptation resolves the contradiction between compatibility and luminance consistency.
Data Source
AI summary
A current limiting circuit includes: a gain calculation circuit which calculates a screen power value based on pixel values and calculates a gain based on the screen power value; and a gain multiplication circuit which multiplies the pixel values by the gain, and when a maximum value of the pixel values exceeds a first threshold value, the gain calculation circuit calculates the screen power value by use of a common pixel value greater than or equal to the maximum value instead of the pixel values, and when the screen power value exceeds a control target power value, the gain calculation circuit sets the gain to a ratio of the control target power value with respect to the screen power value, and when the screen power value is less than or equal to the control target power value, the gain calculation circuit sets the gain to 1.