LED Chromaticity Selection for Uniform White Light
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Solution Overview
Problem
Solid state lighting systems face challenges in achieving consistent hue and color rendering index for general illumination, with variations in LED intensity and placement leading to non-uniform color output over time and temperature changes, and existing solutions like fluorescent lights have environmental concerns and poor color rendering.
Innovation Solution
A solid state lighting apparatus comprising multiple LEDs with specific chromaticities, including a first LED emitting blue or green light and a second LED emitting yellow or green light, with phosphors to produce a combined light with a target chromaticity, arranged on a planar substrate to achieve consistent and high color rendering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If multiple solid state lighting panels are connected together to form a lighting system, then the illumination area is increased, but the hue consistency deteriorates due to variations in LED intensity and placement
Solution Approach 1:
The patent applies parameter changes by carefully selecting and controlling the chromaticity parameters of individual LEDs within specific ranges. By defining target chromaticity values and acceptable deviation ranges for each LED, the system maintains consistent combined light output even when multiple panels are connected, resolving the hue consistency issue while expanding illumination area.
Solution Approach 2:
The patent implements local quality by assigning specific chromaticity characteristics to different LEDs within the array. Each LED is selected to have chromaticity within a defined range around a target value, creating localized quality control that ensures uniform combined output across the entire multi-panel lighting system.
2Device complexity
If LED chips are mounted directly to a submount with phosphor coating, then the device complexity is reduced, but the manufacturing precision deteriorates due to challenges in achieving uniform phosphor distribution
Solution Approach 1:
The patent addresses manufacturing precision by defining specific parameter ranges for phosphor concentration and distribution. By establishing acceptable ranges for phosphor content and its spatial distribution on the submount, the invention enables direct mounting methods to achieve consistent chromaticity output without requiring complex multi-step manufacturing processes.
3Ease of manufacture
If a single type of LED is used throughout the lighting system, then the manufacturing process is simplified, but the adaptability deteriorates when temperature variations cause color shift
Solution Approach 1:
The patent applies local quality by selecting LEDs with slightly different chromaticity characteristics to be placed in different thermal zones or positions within the lighting assembly. This allows the system to compensate for temperature-induced color shifts, as LEDs in different locations experience different thermal conditions and their combined output maintains overall color consistency.
Solution Approach 2:
The patent uses composite materials by combining multiple LED types with different chromaticity profiles in a single lighting system. This composite approach creates a lighting assembly that is more adaptable to temperature variations, as the different LED types respond differently to thermal changes, collectively maintaining stable overall output.
4Device complexity
If LED intensity variations are not compensated, then the device complexity is reduced, but the color rendering index deteriorates
Solution Approach 1:
The patent resolves the contradiction by selecting LEDs with intensity parameters that fall within specifically defined ranges. By controlling the initial intensity parameters of individual LEDs during selection and assembly, the system achieves consistent color rendering without requiring complex active control systems to compensate for variations.
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 provides high color uniformity, improved thermal stability, and high luminous efficacy, overcoming the limitations of existing technologies by generating consistent white light with high color rendering index and reduced environmental impact.
Implementation Method 1
a first LED including a first LED chip that emits light in the blue or green portions of the visible spectrum
Implementation Method 2
a phosphor that emits red light in response to light emitted by the first LED chip
Implementation Method 3
a second LED chip that emits substantially saturated light having a dominant wavelength between about 400 nm and 465 nm
Implementation Method 4
a phosphor that is configured to receive light emitted by the second LED chip and to responsively emit light
Data Source
AI summary
A solid state lighting apparatus includes a plurality of light emitting diodes (LEDs) including at least a first LED and a second LED. Chromaticities of the first and second LEDs are selected so that a combined light generated by a mixture of light from the pair of LEDs has about a target chromaticity. The first LED may include a first LED chip that emits light in the blue portion of the visible spectrum and a phosphor that emits red light in response to blue light emitted by the first LED chip. The second LED emits light having a color point that is above the planckian locus of a 1931 CIE Chromaticity diagram, and in particular may have a yellow green, greenish yellow or green hue.