Display Backlight Luminance Control via PWM and Current Segmentation
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Solution Overview
Problem
Existing display apparatuses using LED backlights face challenges in achieving precise luminance control with constant chromaticity, particularly at lower luminance levels, as current methods like PWM, current adjustment, or combinations thereof, struggle to maintain stability and accuracy.
Innovation Solution
Implementing a control mechanism that adjusts the light source's luminance using pulse width modulation based on the ratio of light-on and light-off periods, allowing for precise control of luminance while maintaining constant chromaticity by defining pulse width for higher luminance and adjusting the light-on period ratio for lower luminance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If PWM method is used for luminance control, then luminance control range is extended, but chromaticity stability deteriorates at lower luminance levels
Solution Approach 1:
The patent segments the luminance control into two distinct methods: PWM control for high luminance levels (maintaining constant chromaticity) and current control for low luminance levels (maintaining constant chromaticity). This segmentation allows each control method to operate in its optimal range, resolving the contradiction between extended luminance control range and chromaticity stability.
Solution Approach 2:
The patent changes the control parameter based on luminance level: using PWM duty cycle as the control parameter for high luminance, and using LED drive current as the control parameter for low luminance. This parameter switching enables maintaining constant chromaticity across the entire luminance range while achieving extended luminance control.
2Stability of the object's composition
If current adjustment method is used for luminance control, then chromaticity stability is maintained, but luminance control range is limited
Solution Approach 1:
The patent implements a dynamic control strategy where the control method automatically switches between PWM and current control based on the desired luminance level. For high luminance levels, PWM is used; for low luminance levels, current control is used. This dynamic adaptation extends the luminance control range while maintaining chromaticity stability throughout.
3Illumination intensity
If both PWM and current adjustment are used, then luminance control range is extended, but control system complexity increases
Solution Approach 1:
The patent employs a self-service control mechanism where the system automatically determines which control method (PWM or current control) to use based on the target luminance level. The control algorithm autonomously switches between methods without requiring complex external intervention, thereby extending luminance range while keeping the control system manageable.
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 effectively extends the luminance control range while ensuring constant chromaticity, even at lower luminance levels, by stabilizing the chromaticity and adjusting luminance through pulse width modulation, enhancing the overall performance of display apparatuses.
Implementation Method 1
a light source that irradiates light to the display means
Implementation Method 2
controls the quantity of light of the light source with pulse width modulation, wherein the control means controls the quantity of light of the light source based on the ratio of the light-on period with pulse width modulation to the light-off period
Data Source
AI summary
A display apparatus includes display means for displaying an image, a light source that irradiates light to the display means, and control means for controlling the quantity of light of the light source with pulse width modulation. The control means controls the quantity of light of the light source based on the ratio of the light-on period with pulse width modulation to the light-off period when the light source is turned off.