LED Backlight PWM Frequency Control for LCD Artifact Reduction
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Solution Overview
Problem
Liquid crystal display (LCD) backlight illumination systems face challenges in minimizing resolution loss, reducing distortion or artifacts, and achieving broad brightness adjustment ranges due to the configuration of LEDs.
Innovation Solution
An edge-lit backlight unit with strings of LEDs, where a pulse width modulator (PWM) signal is used to control the activation and deactivation of the strings at a high frequency, allowing for effective frequency generation and reduced power consumption, thereby minimizing visual artifacts and maintaining brightness control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If groupings of LEDs are utilized to reduce power consumption, then power consumption is reduced, but resolution is reduced and distortion or artifacts occur
Solution Approach 1:
The LED array is divided into multiple independently controllable groupings or zones, allowing selective activation of individual LED groups rather than activating all LEDs simultaneously. This segmentation enables power consumption reduction by activating only necessary regions while maintaining sufficient resolution through precise control of each segment's contribution to the overall image.
Solution Approach 2:
Different regions of the LED array are controlled with different activation patterns based on local requirements. Areas requiring higher resolution maintain full LED activation, while less critical areas use reduced activation to save power. This local quality approach allows resolution to be maintained where needed while reducing overall power consumption.
2Use of energy by moving object
If groupings of LEDs are utilized to reduce power consumption, then power consumption is reduced, but distortion or artifacts are increased
Solution Approach 1:
LED groupings are activated and deactivated in periodic cycles rather than remaining constantly on or off. By rapidly switching between activation states in a periodic manner, the system reduces average power consumption while maintaining continuous illumination perception, thereby minimizing visible distortion or artifacts that would occur with static grouping configurations.
3Manufacturing precision
If LEDs are controlled individually to maintain resolution, then resolution is maintained, but power consumption increases
Solution Approach 1:
The system dynamically adjusts which LED groupings are activated based on real-time requirements for resolution and power consumption. Rather than using a fixed configuration, the control system adaptively determines the optimal set of LED groups to activate for each display scenario, allowing resolution to be maintained when necessary while minimizing power consumption during normal operation.
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
This approach reduces visual artifacts and maintains reduced power consumption while allowing for broad dimming ranges and high brightness resolution, effectively addressing the limitations of existing LCD backlight systems.
Implementation Method 1
Control of the activation and deactivation of the strings may be generated via a pulse width modulator (a pulse width modulation device). The strings may be activated in such a manner that the first string is activated, followed by the second string, and so forth.
Implementation Method 2
An edge-lit backlight unit with strings of LEDs, where a pulse width modulator (PWM) signal is used to control the activation and deactivation of the strings at a high frequency
Implementation Method 3
The activation of these strings may cause LEDs thereon to emit light
Data Source
AI summary
A method and system for modifying the pulse width modulation frequency for controlling the backlit illumination intensity of a liquid crystal display. The modified pulse width modulation frequency may be selected to reduce distortion in the display while allowing for a wide range of dimming settings for the display. A pulse width modulation signal may be also be phase shifted such that a string of light sources may be sequentially activated to generate a effective frequency greater than that of the frequency of the pulse width modulation signal.