LED Lighting Device with Phosphor Particle Size Control
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Solution Overview
Problem
Conventional lighting technologies, such as incandescent and fluorescent lights, are inefficient and have limitations in color rendering index (CRI Ra) and lifespan, necessitating the development of more energy-efficient and long-lasting alternatives like light emitting diodes (LEDs) that can produce white light effectively.
Innovation Solution
The use of LEDs in combination with lumiphors, specifically phosphor particles of varying sizes, to achieve high efficacy and CRI Ra, with the lumiphors being excited to produce a mixture of light that falls within specific chromaticity coordinates on the CIE Diagram, creating a white light source with improved color temperature and gamut.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If incandescent light bulbs are used, then color rendering index is high (Ra > 95), but energy efficiency is very low (90% of electricity released as heat)
Solution Approach 1:
The patent replaces the thermal radiation mechanism of incandescent bulbs with electroluminescence in LEDs and photoluminescence in phosphors. This substitution eliminates the need for heating to produce light, directly converting electrical energy to optical energy with much higher efficiency and minimal heat generation.
Solution Approach 2:
The patent changes the fundamental operating parameters from thermal excitation (incandescent) to electrical and optical excitation (LED+phosphor). By operating at room temperature rather than thousands of degrees, the system achieves high energy efficiency while maintaining good color rendering through phosphor down-conversion.
2Use of energy by moving object
If fluorescent light bulbs are used, then energy efficiency is improved (10x better than incandescent), but color reproduction is less accurate (Ra 70-80)
Solution Approach 1:
The patent uses a composite approach combining LED materials (GaN, InGaN) with multiple phosphor materials (Y3Al5O12:Ce, Lu3Al5O12:Ce, beta-SiAlON:Eu). This composite system allows precise spectral engineering to achieve both high energy efficiency and excellent color rendering (Ra > 90) by combining the narrow-band LED emission with broad-band phosphor down-conversion.
Solution Approach 2:
The patent applies different phosphor materials with specific emission characteristics to different regions or combinations, optimizing the overall spectral output. By selecting phosphors with appropriate emission wavelengths and bandwidths, the system achieves accurate color rendering while maintaining high efficiency.
3Duration of action of stationary object
If conventional light bulbs are used, then device replacement is needed periodically, but access is difficult in applications like vaulted ceilings and high buildings
Solution Approach 1:
The patent addresses the lifetime issue by making the LED module itself replaceable while keeping the fixture permanent. The dynamic replacement strategy allows maintenance without replacing entire fixtures in hard-to-access locations, reducing maintenance complexity and cost.
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 solution results in a high efficacy white light source with improved color rendering index and longer lifespan, achieving lumens per watt efficiency and providing a pleasing white light with reduced manufacturing complexity and reflected light.
Implementation Method 1
Light emitting diodes are semiconducting devices that emit light (ultraviolet, visible, or infrared) when a potential difference is applied across a p-n junction structure
Implementation Method 2
A first luminescent material is disposed on a portion of the light emitting diode and is excited by light emitted by the light emitting diode to produce a first responsive radiation
Data Source
AI summary
A lighting device comprising at least one solid state light emitter and at least one lumiphor. If each solid state light emitter is illuminated and each lumiphor is excited, a mixture of light emitted has x, y color coordinates within an area defined by the coordinates 0.32, 0.40; 0.36, 0,48; 0.43, 0.45; 0.42, 0.42; and 0.36, 0.38. The lumiphor(s) comprises phosphor particles, in the range of from 3 to 7 micrometers (or 5-15, 10-20, or 15-25 micrometers), or having a mean particle size of 5, 10, 15, 20 micrometers. Also, a lighting device comprising at least one emitter and at least one lumiphor in which the lumiphor comprises phosphor particles having sizes as mentioned above, where the lighting device has an efficacy of at least 60 (or 70, or 80) lumens per watt.