Pulse Width Modulator Subframe Distribution for Flicker Alleviation
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Solution Overview
Problem
Display devices using pulse width modulation (PWM) driving methods often experience flicker phenomena due to uneven distribution of subframes with different numbers of active unit times, which affects image quality.
Innovation Solution
A display device and pulse width modulator that distribute subframes with the same number of active unit times by adjusting the activation width of the modulation signal based on estimated cumulative errors, ensuring that each subframe has either 'a' or 'a+1' unit times activated, where 'a' is determined by the data value and the number of subframes, thereby preventing continuous progression of subframes with significantly different active unit times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If subframes with different numbers of active unit times are used to represent different data values, then the display device can achieve precise brightness control, but continuous progression of subframes with significantly different active unit times causes flicker phenomenon
Solution Approach 1:
The patent applies periodic action by organizing subframes into cycles where the number of active unit times varies periodically rather than monotonically. Specifically, when the current subframe number modulo 4 equals 0 or 3, the activation width is set to one value; when it equals 1 or 2, the activation width is set to another value. This creates a periodic pattern in subframe activation that distributes the visual impact of brightness changes across multiple cycles, preventing continuous progression of subframes with significantly different active unit times and thereby reducing flicker while maintaining brightness control precision
Solution Approach 2:
The patent changes the parameter of activation width based on the subframe number and its remainder when divided by 4. By dynamically adjusting the activation width according to the formula involving (subframe number modulo 4), the system optimizes the distribution of active unit times across subframes. This parameter change strategy ensures that subframes are distributed more evenly in terms of their visual impact, preventing the continuous progression of subframes with significantly different active unit times that causes flicker
2Illumination intensity
If the activation width of modulation signal is adjusted according to data value, then the light emitting element can emit light with desired brightness, but uneven distribution of subframes with different active unit times degrades image quality
Solution Approach 1:
The patent implements periodic action by creating a cyclic pattern in subframe activation where the activation width repeats every 4 subframes. By using the subframe number modulo 4 to determine activation width, the system ensures that subframes with similar activation characteristics appear periodically rather than continuously. This periodic distribution prevents the uneven subframe progression that degrades image quality while still allowing the light emitting element to emit light with the desired brightness through appropriate activation width selection
Solution Approach 2:
The patent dynamically changes the activation width parameter based on the relationship between subframe number and data value, specifically using the remainder of subframe number divided by 4. This parameter change strategy optimizes the distribution of active unit times across subframes, ensuring that subframes are evenly distributed in terms of their visual impact. The activation width is adjusted according to the formula involving (subframe number modulo 4), which prevents continuous progression of subframes with significantly different active unit times and thereby maintains high image quality
Data Source
AI summary
In a display device according to an embodiment, subframes having the same number of active unit time(s) are distributed. As a result, according to the display device of the disclosure, the flicker phenomenon may be alleviated.