Multiple Phosphor Wheels for Thermal Dissipation in Projectors
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Solution Overview
Problem
In projector systems using phosphors for light generation, the heat loss due to the Stokes shift leads to increased operating temperatures, reducing the overall efficiency of light generation, and scaling the projector's power results in thermal dissipation challenges due to limited motor and installation space constraints.
Innovation Solution
The use of multiple phosphor wheels, where phosphors are thermally decoupled and synchronized to distribute heat loss effectively, allowing for improved thermal dissipation and reduced temperature rise, enabling the scaling of power to several thousand lumens without significant cost increases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the primary light power is increased to scale the output power, then the light flux increases, but the heat loss and operating temperature of the phosphor increase, reducing conversion efficiency
Solution Approach 1:
The single phosphor wheel is divided into multiple phosphor wheels, each handling a portion of the light conversion task. This segmentation distributes the heat generation across multiple components, reducing the thermal load on each individual phosphor wheel while maintaining high output power.
2Loss of energy
If the wheel diameter of the phosphor wheel is increased to improve thermal dissipation, then the thermal dissipation area increases, but the installation space requirements and motor power requirements increase
Solution Approach 1:
Instead of expanding a single large phosphor wheel, the system uses multiple smaller phosphor wheels. Each wheel has a compact diameter that fits within space constraints, while the collective area of multiple wheels provides sufficient thermal dissipation surface area.
Solution Approach 2:
The solution transitions from a single large-diameter wheel to multiple smaller wheels arranged in space, utilizing the third dimension (depth/stacking) to achieve thermal dissipation without increasing the radial footprint or requiring a larger motor.
3Temperature
If the wheel diameter is increased from 33mm to 70mm to reduce average power density, then the thermal dissipation improves, but the motor requirements and installation space increase significantly
Solution Approach 1:
The thermal management function is segmented across multiple wheels, each with its own motor. This allows the use of smaller, less powerful motors that are easier to control and integrate, rather than one large motor driving a giant wheel.
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 reduces heating of phosphors, enhances thermal dissipation, and allows for increased power scaling while maintaining efficiency, enabling the production of high-lumen lighting systems with improved thermal management.
Implementation Method 1
The phosphor wheel typically includes a central driveshaft, which is driven by a motor. The laser generates primary light, which is at least partially converted by phosphors located on the phosphor wheel into secondary light of longer wavelength (down-conversion).
Implementation Method 2
When the phosphor wheel is exposed, a certain power loss is generated in the phosphor, which is based for the most part on the so-called Stokes shift (which represents an energy difference of the photos between the absorbed and emitted radiation). This power loss leads to heating of the phosphor.
Implementation Method 3
The heat loss is dissipated by convection, radiant cooling and by thermal conduction of the carrier material of the phosphor wheel to the motor axle of the phosphor wheel
Implementation Method 4
The heat loss is dissipated by convection, radiant cooling and by thermal conduction of the carrier material of the phosphor wheel to the motor axle of the phosphor wheel
Implementation Method 5
The heat loss is dissipated by convection, radiant cooling and by thermal conduction of the carrier material of the phosphor wheel to the motor axle of the phosphor wheel
Data Source
AI summary
Various embodiments relate to a lighting apparatus including at least one light generating device for generating primary light, and at least one phosphor wheel arranged optically downstream of the light generating device. The phosphor wheel may include at least one phosphor for wavelength conversion of the primary light into secondary light. A plurality of phosphor wheels are arranged optically downstream of the light generating device.