Phosphor Wheel Arrangement for Thermal Management in High-Power Lighting
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Solution Overview
Problem
Existing lighting devices for projection applications face limitations in power scaling due to thermal quenching of phosphors, particularly at higher pump powers, as the heat dissipation becomes inefficient, leading to reduced conversion efficiency and spatial constraints.
Innovation Solution
The use of two phosphor wheels arranged one behind the other, with each wheel having different phosphor regions that can be irradiated with pump light, allowing for heat dissipation through multiple wheels and optimizing phosphor types based on temperature dependence, along with a collecting optical unit to efficiently collect conversion light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the pump power is increased to achieve higher output light power, then the luminous flux is improved, but the heat loss increases leading to thermal quenching of phosphor and reduced conversion efficiency
Solution Approach 1:
The phosphor wheel is divided into multiple phosphor segments (first phosphor region, second phosphor region, third phosphor region) arranged in the rotation direction. Each segment converts pump light to different wavelength ranges, allowing distributed heat generation and improved heat dissipation across the wheel structure.
Solution Approach 2:
The patent transitions from a single phosphor layer to a multi-layer phosphor wheel structure with phosphor regions arranged both radially and azimuthally. This three-dimensional arrangement increases the surface area for heat dissipation and allows better thermal management while maintaining high conversion efficiency.
2Loss of energy
If the diameter of the phosphor wheel is increased to improve heat dissipation, then the heat loss is reduced, but the space requirement and wheel motor power increase
Solution Approach 1:
Different phosphor segments are positioned at different radial distances from the rotation axis, with each segment optimized for its local thermal conditions. The multi-segment design allows heat to be dissipated locally at multiple zones rather than requiring a single large wheel.
Solution Approach 2:
The phosphor wheel rotates during operation, dynamically distributing the pump light absorption and heat generation across different angular positions. This rotation enables continuous heat dissipation to the surrounding environment and prevents localized thermal accumulation, achieving effective heat management without increasing wheel diameter.
3Power
If multiple phosphor wheels are arranged one behind the other, then the heat dissipation is improved and power scaling is enabled, but the device complexity increases
Solution Approach 1:
Multiple phosphor segments are combined into a single integrated phosphor wheel structure that rotates as one unit. This merging approach achieves the benefits of multiple phosphor layers (improved heat dissipation, enhanced power handling) while avoiding the mechanical complexity of multiple separate rotating wheels, synchronization mechanisms, and alignment systems.
Solution Approach 2:
The single phosphor wheel serves multiple functions simultaneously: it performs wavelength conversion across multiple spectral ranges through different phosphor segments, dissipates heat through its distributed structure and rotation, and maintains mechanical simplicity as a single rotating component. This multi-functionality resolves the contradiction between power scaling capability and device complexity.
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
This configuration enables power scaling into the multi-kilolumens range without additional optical components, reduces heat-related efficiency losses, and allows for higher luminous flux by managing temperature sensitivity of phosphors, thus overcoming the limitations of single phosphor wheel designs.
Implementation Method 1
at least one first phosphor region which can be irradiated with the pump light of the pump light source and re-emits said pump light at least partly in a wavelength-converted fashion
Implementation Method 2
The heat is dissipated by surface radiation
Implementation Method 3
by convection of the ambient medium (e.g. air)
Implementation Method 4
by thermal conduction, e.g. via the rotation spindle
Data Source
AI summary
A lighting device comprising a pump light source and two or more phosphor wheels arranged one directly behind another. As a result, firstly, the heat loss can be dissipated via the two phosphor wheels. Secondly, only a single common collecting optical unit is required for collecting the conversion light emitted by the first phosphor wheel and the second phosphor wheel.