Variable-Frequency PWM Pixel Dimming for Gray-Scale Resolution
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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, necessitating improved temporal modulation techniques for enhanced dynamic range and bit depth.
Innovation Solution
Implementing a system with 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 variable temporal periods and dimming control without loss of gray-scale resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If minimum temporal period is used in pulse-width modulation, then circuit operation is simplified, but gray-scale resolution and image frame rates are limited
Solution Approach 1:
The patent implements dynamic temporal modulation where the minimum temporal period is not fixed but can be varied based on luminance requirements. The system adjusts the effective minimum period dynamically to achieve higher gray-scale resolution at lower luminances while maintaining circuit simplicity through software-controlled timing adjustments rather than hardware complexity changes.
Solution Approach 2:
The patent changes the temporal period parameter dynamically based on the desired luminance level. By varying the minimum temporal period parameter in response to luminance signals, the system achieves improved gray-scale resolution without requiring fundamental circuit redesign, thus resolving the contradiction between measurement precision and device complexity.
2Adaptability or versatility
If temporal modulation is used to improve dynamic range, then luminance control is enhanced, but hardware complexity increases
Solution Approach 1:
The patent uses periodic temporal modulation where the light emitter is switched on and off in periodic pulses with varying duty cycles. This periodic action enables dynamic range control through simple timing adjustments rather than complex hardware, achieving adaptability while maintaining hardware simplicity.
Solution Approach 2:
The patent replaces complex hardware-based luminance control mechanisms with software-controlled temporal modulation. Instead of using additional analog control circuits or multiple light emitters, the system achieves dynamic range control through digital timing control of a single light emitter, substituting mechanical/hardware complexity with software-based solutions.
3Use of energy by moving object
If constant current is used for pixel control, then light emitter efficiency is maintained, but luminance adjustment range is limited
Solution Approach 1:
The patent maintains constant current efficiency during active periods while using periodic on/off switching to achieve luminance adjustment. The light emitter operates at constant current during each pulse, maintaining efficiency, while the average luminance is controlled by varying the pulse width and duty cycle, thus resolving the contradiction between efficiency and adjustment range.
Solution Approach 2:
The system uses preliminary temporal modulation setup where the constant current is established in advance during pulse intervals, and the overall luminance is controlled by pre-calculating the appropriate pulse width and duty cycle based on desired luminance levels. This preliminary action allows efficient constant current operation while achieving wide luminance adjustment range through timing control.
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.