Static Phosphor Light Emitting Device Thermal Management
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Solution Overview
Problem
Conventional laser projection systems rely on rotating phosphor wheels, which are prone to reliability issues, overheating, and increased costs, and lack efficiency due to moving parts and limited heat sinking capabilities, making them unsuitable for applications requiring robustness and compactness.
Innovation Solution
A static light emitting device with a luminescent element and a heat sink, where the luminescent element's dimensions and dopant concentration are optimized to prevent overheating, enhance cooling, and improve conversion efficiency, while a scattering mechanism ensures sufficient light penetration and heat spreading, reducing the need for complex optics and moving parts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a phosphor wheel is used to distribute and cool laser light, then light distribution and cooling are achieved, but the system reliability decreases due to moving parts and photo-thermal degradation
Solution Approach 1:
The patent replaces the rotating phosphor wheel (mechanical system) with a static phosphor layer mounted on a heat sink. The mechanical rotation is substituted by thermal conduction through the heat sink, eliminating moving parts while maintaining cooling functionality. This resolves the contradiction by removing the reliability issues associated with mechanical rotation while preserving the temperature control capability.
Solution Approach 2:
The patent extracts the cooling function from the rotating phosphor wheel and separates it into a dedicated heat sink structure. The phosphor layer is decoupled from the mechanical rotation, allowing the cooling function to be independently optimized through thermal conduction pathways without the constraints of rotational mechanics.
2Illumination intensity
If a phosphor wheel with diameter of 3-4 cm is used, then light distribution is achieved, but the system size increases and etendue is reduced
Solution Approach 1:
The patent replaces the large-diameter rotating wheel with a compact static phosphor layer on a heat sink. By eliminating the need for rotation-based light distribution, the system achieves effective light distribution over a much smaller footprint, directly reducing system volume while maintaining illumination quality.
Solution Approach 2:
The patent transitions from a two-dimensional rotating surface (wheel) to a three-dimensional static structure (phosphor layer on heat sink). This dimensional change allows the light distribution function to be achieved through thermal and optical conduction in a compact volume, reducing the overall system size while maintaining effective light distribution.
3Temperature
If a phosphor wheel is used, then cooling is achieved through rotation, but the system complexity and manufacturing cost increase
Solution Approach 1:
The patent replaces the complex rotating mechanical system with a simple static thermal conduction structure. The cooling function is achieved through direct thermal contact between the phosphor layer and heat sink, eliminating motors, bearings, and control systems required for rotation, thereby significantly reducing device complexity.
Solution Approach 2:
The patent enables the phosphor layer to self-cool through direct thermal conduction to the heat sink without requiring external mechanical actuation. The system serves itself by utilizing the natural heat flow from the phosphor to the heat sink, eliminating the need for complex active cooling mechanisms.
4Device complexity
If a static phosphor layer without heat sink is used, then device simplicity is achieved, but overheating occurs reducing efficiency
Solution Approach 1:
The patent introduces a heat sink as an intermediary thermal management component between the phosphor layer and the environment. This intermediary structure provides a dedicated thermal conduction pathway that efficiently removes heat from the phosphor layer, preventing overheating while maintaining the simplicity of the static design.
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 a more reliable, efficient, and cost-effective light emitting device with improved luminous flux and etendue, offering a compact, robust, and versatile solution for applications like digital projection and automotive lighting.
Implementation Method 1
converting at least a part of the first light with the first spectral distribution to second light with a second spectral distribution
Implementation Method 2
a heat sink element arranged to be in thermal contact with at least a part of the luminescent element extending between the first face and the second face
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A light emitting device (1) comprising a luminescent element (3) comprising a first face (31) and a second face (32), the first face comprising a light input surface and one of the first face and the second face comprising a light exit surface, the luminescent element (3) being adapted for receiving first light (4) with a first spectral distribution emitted by at least one laser light source (21, 22, 23) at the light input surface, converting at least a part of the first light with the first spectral distribution to second light (5) with a second spectral distribution, guiding the second light with the second spectral distribution to the light exit surface and coupling at least a part of the second light with the second spectral distribution out of the light exit surface, and a heat sink element (7) arranged to be in thermal contact with at least a part of the luminescent element (3) extending between the first face (31) and the second face (32), wherein the first face (31) comprises a cross-sectional area A and the luminescent element (3) further comprises a length L being defined as the shortest distance between the first face and the second face and a characteristic length B of the cross sectional area A, the characteristic length B being defined as the square root of the cross sectional area A, and wherein, and wherein the length L and the characteristic length B of the cross sectional area A are chosen such that they satisfy any one of the relations L/B ≥ 2 * Ells/44(W/mm2) for λTHC < 6 W/mK, L/B ≥ 1.3 * Ells/44(W/mm2) for 6 W/mK ≤ λTHC ≤ 8 W/mK, and L/B ≥ 0.85 * Ells/44(W/mm2) for 8 W/mK < λTHC, where Ells is the irradiance of the at least one laser light sources measured in W/mm2 and λTHC is the thermal heat coefficient of the luminescent element at room temperature.