Blue-Shifted LED Packages for High-Temperature Color Rendering
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Solution Overview
Problem
Solid state light fixtures face challenges in maintaining high luminous efficiency and color rendering properties at elevated temperatures, particularly with red LEDs used in true white fixtures experiencing reduced efficiency and color shift, and phosphor-converted white LEDs facing inefficiencies due to double conversion losses.
Innovation Solution
The use of blue-shifted-yellow/green and blue-shifted-red LED packages with distinct phosphor-converted LEDs, where blue LEDs have associated recipient luminophoric mediums that emit light in the yellow and green or red ranges, respectively, reducing double conversion inefficiencies and maintaining performance at high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If red LEDs are used in true white fixtures, then color rendering properties are improved, but luminous efficiency decreases at elevated temperatures
Solution Approach 1:
The patent divides the white light generation into separate blue LED sources and distinct phosphor-converted yellow/green and red LED packages, rather than using a single true white LED. This segmentation allows independent optimization of each component's temperature characteristics, maintaining color rendering through the red package while preserving overall luminous efficiency by using efficient blue LEDs as the primary source.
Solution Approach 2:
The patent changes the spectral parameters by using blue-shifted LEDs with peak wavelengths in the 440-470 nm range, paired with phosphors that convert to yellow/green and red wavelengths. This parameter change in the excitation source wavelength allows the system to maintain efficient blue LED operation at high temperatures while still achieving good color rendering through the phosphor conversion process.
2Illumination intensity
If phosphor-converted white LEDs are used, then white light is produced, but double conversion losses reduce luminous efficiency
Solution Approach 1:
The patent extracts the red wavelength generation from the phosphor conversion process and provides it through a separate red LED package. This removes the need for double conversion (blue to yellow/green, then yellow/green to red) and replaces it with direct blue-to-red phosphor conversion or direct red LED emission, eliminating the energy losses associated with sequential phosphor conversions.
3Illumination intensity
If blue LEDs with yellow phosphors are used, then cool white light is produced, but color rendering properties deteriorate
Solution Approach 1:
The patent merges the output of blue LEDs with yellow/green phosphors and red LED packages to create a combined light spectrum. This combination maintains the cool white light characteristics from the blue-yellow/green portion while adding the red component from the separate package to improve overall color rendering, achieving both illumination intensity and color rendering goals simultaneously.
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 luminous flux, CRI, CRI R9, and Qg performance, making the solid state light fixtures suitable for high temperature operations while providing improved color rendering and efficiency compared to conventional true white and phosphor-converted white LED packages.
Implementation Method 1
phosphors that convert some of the light emitted by the LED to light of one or more other colors
Implementation Method 2
When a sufficient voltage is applied across the p-n junction, electrons in the n-type semiconductor layers and holes in the p-type semiconductor layers flow toward the p-n junction. As the electrons and holes flow toward each other, some of the electrons will 'collide' with corresponding holes and recombine. Each time this occurs, a photon of light is emitted
Data Source
AI summary
Solid state light fixtures include a plurality of blue-shifted-yellow/green light emitting diode (“LED”) packages and a plurality of blue-shifted-red LED packages, where the solid state light fixture emits light having a correlated color temperature of between 1800 K and 5500 K, a CRI value of between 80 and 99, a CRI R9 value of between 15 and 75, and a Qg value of between 90 and 110 when the blue-shifted-yellow/green LED packages and the blue-shifted-red LED packages are operating at steady-state operating temperatures of at least 80° C.