Multi-chip LED Excitation for High CRI White Light
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Solution Overview
Problem
Current white LED illumination systems, both multi-chip and single-chip, face challenges in achieving optimal color rendering and luminosity due to limitations in wavelength balance and phosphor efficiency, leading to suboptimal performance in producing white light with high brightness and natural color rendering.
Innovation Solution
A multi-chip excitation source system that co-excites a phosphor package using a combination of LEDs emitting in specific wavelength ranges, such as UV and blue, or blue and green, to enhance the photoluminescence spectrum and achieve a higher color rendering index (CRI) by optimizing the ratio of radiation sources and phosphor contributions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-chip LED-phosphor system is used, then the device complexity is reduced and manufacturing cost is lowered, but the color rendering properties and wavelength balance are insufficient
Solution Approach 1:
The invention divides the excitation source into multiple LED chips (e.g., blue LED at 430-470nm and green LED at 480-530nm) that operate at different wavelengths. Each chip excites specific phosphors in the package, creating a segmented approach to achieving full-spectrum white light with superior color rendering while maintaining manageable system complexity
Solution Approach 2:
The invention employs a composite phosphor package containing multiple phosphor materials (yellow-emitting phosphor, red-emitting phosphor, green-emitting phosphor) that work together with multiple LED chips. This composite structure enables the system to achieve CRI>90 by combining the emission spectra from different phosphor-LED pairs, resolving the contradiction between simplicity and color rendering quality
2Device complexity
If conventional blue LED with yellow phosphor is used, then the system is simpler, but the emission spectrum is deficient in longer wavelengths resulting in poor color rendering
Solution Approach 1:
The excitation spectrum is segmented into multiple wavelength regions using different LED chips (blue and green LEDs). Each LED chip targets specific phosphors with complementary emission spectra, ensuring comprehensive coverage across the visible range including the previously deficient longer wavelengths (red region), thus achieving CRI>90
Solution Approach 2:
Different regions of the emission spectrum are optimized by assigning specific LED-phosphor pairs to different wavelength ranges. The blue LED excites yellow and red phosphors for long-wavelength coverage, while the green LED excites green and yellow phosphors for mid-wavelength coverage, creating locally optimized spectral distribution that collectively achieves full-spectrum quality
3Illumination intensity
If multiple LED chips are used for co-excitation, then the color rendering index is improved to greater than 90, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
Multiple LED chips (blue and green) are merged into a single excitation assembly that operates together to illuminate a unified phosphor package. This merging approach achieves CRI>90 through combined spectral output while simplifying the overall structure compared to separate multi-chip assemblies, as all components work cooperatively within a single illumination unit
Solution Approach 2:
The multi-chip LED-phosphor system serves multiple functions simultaneously: it provides high CRI (>90) illumination, achieves full-spectrum coverage, maintains energy efficiency, and enables adjustable color temperature. This multi-functionality resolves the contradiction by demonstrating that increased complexity enables superior performance across multiple parameters rather than just one
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
The multi-chip system achieves a CRI greater than 90, with increased brightness and improved color rendering properties, surpassing the limitations of single-chip systems by providing a more balanced and efficient white light emission across a broader spectrum.
Implementation Method 1
a phosphor package, the phosphor package emitting photoluminescence in a wavelength ranging from about 440 nm to about 700 nm upon co-excitation from the first and second radiation sources
Data Source
AI summary
Embodiments of the present invention are directed toward white light illumination systems (so called “white LEDs”) that comprise a multi-chip excitation source and a phosphor package. In a two-chip source, the two LEDs may be UV-emitting and blue emitting, or blue-emitting and green-emitting. The phosphor package is configured to emit photoluminescence in wavelengths ranging from about 440 nm to about 700 nm upon co-excitation from the first and second radiation sources. The photoluminescence emitted by the phosphors is at least 40 percent of the total power in the white light illumination, and the portion of the total power in the white light illumination contributed by the first and second radiation sources (LEDs) is less than about 60 percent. This ratio can vary in alternative embodiments, and includes 50/50, 60/40, 70/30, and 80/20, respectively. The white light illumination emitted by the system has in one embodiment a color rendering index (CRI) greater than about 90.