Display Dimming With Variable-Frequency PWM Pixel Control
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Solution Overview
Problem
Existing pixel control circuits in displays are limited by minimum temporal periods, which restrict the gray-scale resolution and image frame rates, especially in micro-light-emitting diode displays, due to hardware limitations.
Innovation Solution
Implementing a variable-frequency-clock signal generator and pixel-control signal generator to modulate pixel luminance using pulse-width or pulse-density modulation with a constant current, allowing for adjustable temporal periods and improved gray-scale bit depth and dynamic range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If pulse-width modulation with fixed minimum temporal period is used, then circuit complexity is reduced, but gray-scale resolution and dynamic range are limited
Solution Approach 1:
The patent applies dynamics by making the temporal period variable rather than fixed. The pixel control circuit adjusts the temporal period of PWM signals dynamically based on the desired luminance level, allowing longer periods for lower luminances and shorter periods for higher luminances. This dynamic adjustment enables higher gray-scale resolution without requiring more complex circuitry, as the same hardware can achieve finer control by varying the time scale.
Solution Approach 2:
The patent changes the temporal period parameter of the PWM signal to resolve the contradiction. By allowing the temporal period to vary across a wide range (from minimum to maximum values), the system achieves enhanced gray-scale bit depth and dynamic range. The control circuit selects appropriate temporal periods based on the luminance requirements, effectively using parameter variation to improve precision without increasing circuit complexity.
2Manufacturing precision
If minimum temporal period is reduced to improve gray-scale resolution, then image frame rate decreases
Solution Approach 1:
The system dynamically selects temporal periods based on the specific luminance requirements of each pixel and frame conditions. For pixels requiring low luminance, longer temporal periods are used, which can be accommodated within the frame time without reducing frame rate. For high luminance pixels, shorter temporal periods are used, maintaining faster response. This dynamic adaptation allows the system to achieve high gray-scale bit depth while maintaining acceptable image frame rates.
Solution Approach 2:
The patent segments the frame time into variable temporal periods for different pixels based on their luminance requirements. Instead of using a uniform minimum temporal period for all pixels, the system divides the available time differently for different pixels, allowing some to use longer periods (improving gray-scale resolution) while others use shorter periods (maintaining frame rate). This segmentation approach resolves the trade-off between precision and speed.
3Manufacturing precision
If variable temporal periods are implemented, then gray-scale resolution improves, but device complexity increases
Solution Approach 1:
The pixel control circuit is designed to be universal and multi-functional, handling both the generation of PWM signals with variable temporal periods and the selection of appropriate periods based on luminance requirements. Rather than adding separate dedicated circuits for each function, the same control circuit performs multiple tasks: generating PWM signals, selecting temporal periods, and adapting to different luminance levels. This multi-functionality improves luminance control precision while minimizing the increase in device complexity.
Solution Approach 2:
The patent merges the temporal period selection logic with the PWM signal generation function in a single integrated control circuit. Instead of having separate circuits for period selection and signal generation, these functions are combined, reducing the overall device complexity while still achieving variable temporal periods for improved luminance control precision. The merged circuit efficiently manages both aspects of control within a unified structure.
Data Source
AI summary
A system with dimming control includes a luminance signal, a variable-frequency-clock signal generator responsive to the luminance signal operable to generate a variable-frequency clock signal, a pixel-control signal generator responsive to the variable-frequency clock signal operable to generate a pixel-control signal, and a pixel including a light emitter responsive to the pixel-control signal. The pixel-control signal can be a temporally modulated signal such as a pulse-width modulation signal or a pulse-density modulation signal. A display can comprise an array of pixels and a display controller. The pixel or the display controller can include the variable-frequency clock signal or the pixel-control signal generator, or both.