Warm White Backlight With Dual LED-Phosphor CRI Control
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Solution Overview
Problem
Conventional white light emitting apparatuses using LEDs struggle to provide high-quality warm white light with excellent color rendering properties due to complex circuit configurations, limited color reproduction, and efficiency issues, particularly when using multiple phosphors without proper separation, leading to light loss and degraded phosphor efficiency.
Innovation Solution
A warm white light emitting apparatus employing two LED-phosphor combinations, one generating base light of white or yellowish white and another adjusting the Color Rendering Index (CRI), utilizing alternating current (AC) LEDs for base light and direct current (DC) LEDs for CRI adjustment, with a partition wall to separate the phosphor combinations and reduce light loss and flickering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If three primary color LEDs (red, green, blue) are used to generate white light, then color rendering property is improved, but circuit configuration becomes complicated and manufacturing cost increases
Solution Approach 1:
The patent combines blue LED and yellow phosphor into a single white light generating unit, merging the functions of color conversion and light emission. This reduces the number of LED components from three (red, green, blue) to one (blue LED), simplifying the circuit configuration while maintaining acceptable color rendering through the yellow phosphor's broad emission spectrum
Solution Approach 2:
The patent adjusts the particle size distribution of yellow phosphor particles (specifically controlling D10, D50, D90 values) to optimize the emission spectrum. By changing the phosphor particle size parameters, the system achieves improved color rendering properties without adding circuit complexity, as the spectral modification is achieved through material parameter optimization rather than additional components
2Device complexity
If blue LED and yellow phosphor combination is used, then circuit configuration is simplified and cost is reduced, but color rendering property and color reproduction property are degraded
Solution Approach 1:
The patent applies local quality by creating multiple phosphor layers with different particle size characteristics. The first phosphor layer contains larger particles (D50: 4-6 μm) while the second layer contains smaller particles (D50: 1-3 μm). This spatial differentiation of phosphor properties within the same device enables enhanced color rendering by capturing different portions of the blue LED spectrum and converting them to yellow light with complementary characteristics
Solution Approach 2:
The patent uses composite phosphor materials with specific particle size distributions and compositions. By combining yellow phosphor particles of different sizes and controlling their concentration ratios, the system creates a composite light emission profile that maintains the simplicity of the blue LED-yellow phosphor structure while significantly improving color rendering properties through the synergistic effect of the composite phosphor system
3Device complexity
If multiple phosphors are positioned in encapsulant without separation, then device structure is simplified, but light loss increases and phosphor efficiency is degraded
Solution Approach 1:
The patent segments the phosphor system into distinct layers rather than mixing multiple phosphors in a single encapsulant. The first phosphor layer and second phosphor layer are positioned at different depths within the light emitting apparatus, with each layer containing phosphor particles of specific size ranges. This segmentation prevents mutual absorption and re-absorption of light between different phosphor populations, reducing energy loss while maintaining structural simplicity through the layered architecture
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 simplifies the provision of high-quality warm white light near the Black Body Locus (BBL) curve, suitable for large-sized electronic displays, while reducing flickering and total harmonic distortion (THD) by using AC and DC LEDs in conjunction with anti-flickering and anti-THD circuits.
Implementation Method 1
a blue LED and yellow phosphor to generate a base light of white or yellowish white
Implementation Method 2
a red phosphor having a peak wavelength greater than 600 nm to generate pink light
Data Source
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Figure 5~6
Figure 7~8(b)
AI summary
A warm white light emitting apparatus includes a first light emitting diode (LED)-phosphor combination to generate a base light that is white or yellowish white and a second LED-phosphor combination to generate a Color Rendering Index (CRI) adjusting light. The base light the CRI adjusting light together make a warm white light having a color temperature of 2500 to 4500K