PWM Display Subframe Brightness Control
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Solution Overview
Problem
Display devices using PWM driving methods often experience brightness differences and flicker phenomena among subframes due to varying activation times of modulation signals, especially when dealing with special data values.
Innovation Solution
A display device configuration that includes multiple light emitting elements connected to scan and channel lines, with a pulse width modulating part that generates modulation signals with varying activation widths based on specific data values, ensuring non-overlapping and sequential activation of scan lines and corresponding current transmission through channel lines to maintain consistent brightness across subframes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If PWM driving method is used to control brightness of light emitting elements, then brightness control capability is improved, but brightness difference among subframes occurs causing flicker phenomenon
Solution Approach 1:
The unit frame is divided into multiple subframes, and each subframe is further divided into multiple unit times. By segmenting the brightness control into finer time units (unit times) across multiple subframes, the patent enables precise control of the modulation signal activation width in each subframe, allowing compensation for brightness differences through distributed control.
Solution Approach 2:
The patent dynamically changes the activation width parameter of the modulation signal in different subframes based on the data value. For special data values (1 to (2^N-2)), the activation width is adjusted differently across subframes compared to extreme values (0 or 2^N-1), thereby maintaining consistent perceived brightness across all subframes while preserving PWM brightness control capability.
2Measurement precision
If modulation signal activation width is adjusted according to data value, then brightness control precision is improved, but brightness difference among subframes increases causing flicker
Solution Approach 1:
The patent applies asymmetric treatment to different data value ranges. For data values of 0 or 2^N-1 (extreme values), the modulation signal is activated in all subframes with maximum width. For data values between 1 and (2^N-2) (intermediate values), the activation width varies across subframes according to a specific distribution pattern. This asymmetric strategy maintains high brightness control precision while preventing flicker through appropriate differentiation.
Solution Approach 2:
The modulation signal activation width is made dynamic across subframes for intermediate data values, rather than being static. The activation width changes from subframe to subframe according to the distribution pattern, creating a dynamic control scheme that achieves both precision and flicker reduction through temporal variation.
3Loss of time
If scan lines are activated sequentially in each subframe, then display timing control is improved, but complexity of driving circuit increases
Solution Approach 1:
The scan lines are activated in a periodic sequential manner across subframes (1st scan line in odd subframes, 2nd scan line in even subframes). This periodic activation pattern simplifies the driving circuit design by using regular alternating timing signals, while still achieving precise timing control for each subframe through the systematic periodic structure.
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
The solution effectively reduces brightness differences among subframes, thereby alleviating the flicker phenomenon by adjusting modulation signal activation widths according to specific data values, ensuring consistent light emission across the display.
Implementation Method 1
The light emitting element emits light with brightness according to the data value of the corresponding display data
Implementation Method 2
In the PWM driving method, one unit frame is divided into a plurality of subframes. Each of the plurality of subframes includes a plurality of unit times. The number of unit times, in which the modulation signal is activated, is adjusted according to the data value of the display data
Data Source
AI summary
A display device includes a display panel including light emitting elements, scan lines, and channel lines, a scan driving part that transmits current to the channel lines, a data storage part that stores display data, and a pulse width modulating part that generates modulating signals.