LED Backlight Illumination Control via PWM Sub-Frame Insertion
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Solution Overview
Problem
Conventional backlight illumination methods in LCD displays, particularly those using CCFLs, face inefficiencies due to voltage settling issues, leading to image artifacts and operational inefficiencies, especially in large displays where multiple LEDs are required.
Innovation Solution
Implementing a sequence of alternate pulse-width-modulation (PWM) frames or sub-frames, where the backlight unit is turned off for a phase delay and then on with a finite duty cycle, allowing for efficient backlight regulation through internal or external configuration, optimizing pixel utilization and reducing image artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the backlight unit is turned off for newly updated frames to allow voltage settling, then image artifacts are reduced, but display continuity is interrupted and operational efficiency decreases
Solution Approach 1:
The display frame is segmented into multiple sub-frames, with the first sub-frame having the backlight turned off for voltage settling and subsequent sub-frames having the backlight turned on for display continuity. This segmentation allows simultaneous achievement of image quality improvement and display efficiency.
Solution Approach 2:
The backlight operates in periodic cycles: off during the first sub-frame period for voltage settling, then on during subsequent sub-frame periods for display. This periodic action pattern resolves the contradiction by alternating between settling and display modes.
2Illumination intensity
If multiple LEDs are used in large displays to provide adequate backlight, then illumination coverage is improved, but power consumption and operational complexity increase
Solution Approach 1:
The backlight LEDs operate periodically with duty cycling - off during first sub-frame, on during subsequent sub-frames. This periodic operation reduces average power consumption while maintaining adequate illumination coverage through multiple LEDs.
Solution Approach 2:
The backlight system dynamically adjusts its operation state (on/off) based on the sub-frame timing and display content requirements, allowing optimal balance between illumination coverage and power consumption in large displays.
3Productivity
If the backlight remains on continuously, then display continuity is maintained, but voltage settling issues cause image artifacts
Solution Approach 1:
The continuous display is segmented into sub-frames, with selective backlight control - off for first sub-frame to enable voltage settling, then on for subsequent sub-frames to maintain display continuity. This resolves the contradiction between continuity and image quality.
Solution Approach 2:
The backlight is turned off preliminarily during the first sub-frame to allow voltage settling before data display, preventing image artifacts while maintaining overall display continuity through subsequent sub-frames.
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 enhances the efficiency of LCD display operation by minimizing image artifacts and motion blur, while maintaining high duty cycle utilization, even in large displays, by dynamically controlling the backlight illumination.
Implementation Method 1
illumination systems that include light-emitting-diode (LED) technology
Data Source
AI summary
System(s) and methode s) are provided to regulate backlighting in a light emitting diode (LED)-based display through a sequence of alternate pulse-width-modulation (PWM) frame or sub-frame insertions. Alternate PWM frames or sub-frames can be black or non-black. A plurality of pixels in the display is partitioned into at least one zone including one or more rows of pixels; the at least one zone determines sub-frame period based on refresh frequency of the display. A sequence of alternate PWM sub-frames includes at least one alternate sub-frame and at least one normal sub-frame. Alternate PWM frames or alternate PWM sub-frames include a phase delay during which a backlight unit is turned off, and a PWM sequence in which the backlight unit is turned on with a finite duty cycle for the remainder of the PWM frame or sub-frame.