Phosphor-Converted LED Lighting for 1800K–6500K Black-Body Tuning
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Solution Overview
Problem
Existing color-tunable multi-LED packaged lighting devices face issues with varying thermal stability and aging characteristics among Red, Green, and Blue LEDs, leading to changes in light output over time and temperature, and their emission spectrum often deviates from the black body locus, requiring complex drive circuitry and increased costs.
Innovation Solution
The invention employs a multi-cavity lead frame package with specific chromaticity regions defined by chromaticity coordinates, utilizing narrowband red phosphors like K2SiF6:Mn4+, K2GeF6:Mn4+, and K2TiF6:Mn4+ to generate light with tunable color temperatures ranging from 1800K to 6500K, closely matching the black body locus, and includes a 2D array of LEDs to equalize drive current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If Direct-Emitting Color LED chips (Red, Green, Blue) are used for color-tunable lighting, then a wide color temperature range can be achieved, but the light output changes differently with temperature and time due to different thermal stability and ageing characteristics of each LED type, requiring complex drive circuitry
Solution Approach 1:
The patent extracts the problematic Red LED from the traditional RGB system and replaces it with a Phosphor Converted LED (PCL) that uses a blue LED chip with red phosphor. This extraction eliminates the thermal stability and ageing issues associated with direct-emitting red LEDs while maintaining the ability to generate red light, thereby reducing drive circuitry complexity.
Solution Approach 2:
The patent changes the fundamental parameter of how red light is generated - instead of using direct-emitting red LED chips with their own drive requirements, it uses phosphor conversion from blue light. This parameter change allows the red light output to be controlled through the same blue LED drive circuitry, simplifying the overall system.
2Ease of manufacture
If Phosphor Converted LEDs with broadband red phosphors are used, then manufacturing is simplified, but the emission spectrum deviates from the black body locus, reducing color rendering quality
Solution Approach 1:
The patent uses a composite phosphor system combining broadband red phosphor (K2SiF6:Mn4+) with narrowband red phosphor (CaAlSiN3:Eu2+). This composite approach maintains the manufacturing simplicity of phosphor conversion while achieving a emission spectrum that more closely matches the black body locus, thereby improving chromaticity accuracy.
Solution Approach 2:
The patent segments the red phosphor emission into two distinct components - a broadband component for overall color rendering and a narrowband component for precise spectral matching. This segmentation allows each phosphor type to contribute its strengths while working together to achieve both ease of manufacture and high chromaticity accuracy.
3Adaptability or versatility
If multiple different semiconductor material systems are used for Red, Green, and Blue LEDs, then various color temperatures can be generated, but the different thermal stability and ageing characteristics cause light output to change differently over time, requiring complex compensation circuitry
Solution Approach 1:
The patent merges the control of multiple color temperatures into a single Phosphor Converted LED system where blue, green, and red light are generated from a single blue LED chip through phosphor conversion. This combining approach ensures that all color outputs respond uniformly to temperature and ageing, eliminating the reliability issues caused by using multiple different semiconductor material systems.
Solution Approach 2:
The single blue LED chip in the PCL system serves multiple functions - generating blue light directly and converting to green and red light through phosphors. This multi-functionality allows the system to achieve color temperature tunability while maintaining consistent thermal and ageing characteristics across all color outputs.
4Reliability
If complex drive circuitry is used to compensate for differing LED characteristics, then light output consistency can be maintained, but manufacturing cost and device complexity increase
Solution Approach 1:
The patent extracts and eliminates the need for complex compensation circuitry by fundamentally changing the light generation approach to PCL. Since all colors originate from the same blue LED chip, the inherent uniformity in thermal and ageing characteristics removes the need for active compensation, thereby reducing device complexity while maintaining light output consistency.
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 achieves luminous efficacy with a General Color Rendering Index (CRI Ra) of 80 to 97, ensuring chromaticity close to the black body locus, reducing the need for complex drive circuitry and maintaining consistent light output across varying temperatures.
Implementation Method 1
The phosphor material may be incorporated in the light-transmissive encapsulant in the LED package
Implementation Method 2
a Direct-Emitting blue LED chip and a photoluminescence material, typically a phosphor material, that converts a portion blue excitation light generated by the LED chip
Data Source
AI summary
A light emitting device comprising: a first LED for generating light of a first chromaticity in a first chromaticity region; a second LED for generating light of a second chromaticity in a second chromaticity region; and a third LED for generating light of a third chromaticity in a third chromaticity region, wherein the device is for generating light with a CCT that is tunable within a range of CCTs from 1800K to 6500K and has a chromaticity that is within 5 SDCM of the black body locus; wherein the device has a luminous efficacy of at least 95 lm/W; and wherein the light generated by the device comprises a combination of light generated by the first, second, and third LEDs and wherein the CCT is tunable by controlling power to the first, second and third LEDs.