Hot LED Lighting Systems with Remote Phosphor Thermal Decoupling
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Solution Overview
Problem
Conventional LED lighting systems face limitations in operational lifetime and thermal management, as they typically require maintaining a junction temperature below 85°C to achieve an L70 lifetime of 25,000 hours, which can lead to increased complexity, cost, and size of thermal management systems.
Innovation Solution
Operating LEDs above 85°C by spacing components such as encapsulants and wavelength conversion materials away from the LED, allowing a junction temperature up to 200°C while maintaining an L70 lifetime of at least 25,000 hours, and potentially up to 50,000 hours, without degrading light output, using a bare LED die and remote phosphor configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional LED lighting systems maintain junction temperature below 85°C to achieve L70 lifetime of 25,000 hours, then reliability is improved, but device complexity and size increase due to extensive heat sinking requirements
Solution Approach 1:
The patent extracts the wavelength conversion material from direct contact with the LED, placing it in a separate location within the housing. This separation removes the thermal management burden from the LED assembly, allowing the LED to operate at higher temperatures without compromising the lifetime of the wavelength conversion material. The LED and wavelength conversion material are decoupled into independent functional modules.
Solution Approach 2:
The patent changes the operating temperature parameter of the LED from the conventional below 85°C to above 85°C (up to 200°C). By changing this fundamental operating parameter and separating the LED from the wavelength conversion material, the system achieves high reliability without requiring complex heat sinking. The wavelength conversion material is positioned where it experiences lower temperatures while the LED operates hot.
2Reliability
If conventional LED lighting systems maintain junction temperature below 85°C to achieve L70 lifetime of 25,000 hours, then reliability is improved, but the size of thermal management systems increases
Solution Approach 1:
The wavelength conversion material is extracted from the immediate vicinity of the LED, eliminating the need for large heat sinks that would be required to cool both the LED and the temperature-sensitive wavelength conversion material together. This allows for a compact design where only the LED requires thermal management, and even then, less aggressive cooling is needed since the conversion material is thermally decoupled.
Solution Approach 2:
The patent spatially separates the LED and wavelength conversion material along the optical path dimension. The LED is positioned at one location and the wavelength conversion material at another, allowing independent thermal management. This dimensional separation enables compact packaging without requiring large heat dissipation structures.
3Reliability
If conventional LED lighting systems maintain junction temperature below 85°C to achieve L70 lifetime of 25,000 hours, then reliability is improved, but cost increases due to extensive heat sinking requirements
Solution Approach 1:
By extracting the wavelength conversion material from direct thermal contact with the LED, the patent eliminates the need for expensive, high-performance heat sinking materials and complex thermal management assemblies. The simplified thermal management requirement reduces material costs, assembly complexity, and manufacturing expenses while maintaining the desired L70 lifetime through the separated configuration.
4Device complexity
If LEDs are operated above 85°C, then the need for heat sinking is reduced, but the lifetime of components in contact with the LED decreases below 25,000 hours
Solution Approach 1:
The wavelength conversion material is extracted from the high-temperature zone around the LED and placed in a separate location. This allows the LED to be operated above 85°C without exposing the wavelength conversion material to degrading temperatures, thereby maintaining system lifetime above 25,000 hours while reducing thermal management complexity.
Solution Approach 2:
The patent introduces an optical intermediary pathway where light from the hot LED travels through air or vacuum to reach the wavelength conversion material. This intermediary optical path allows thermal decoupling while maintaining optical coupling, enabling the LED to operate hot without compromising the lifetime of the conversion material.
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 approach reduces the need for extensive heat sinking, decreasing the size, cost, and complexity of thermal management systems, while maintaining or exceeding the expected operational lifetime and conforming to energy efficiency and L Prize requirements.
Implementation Method 1
a wavelength conversion material, such as a YAG:Ce phosphor, that emits yellow light in response to stimulation with blue light
Data Source
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AI summary
LED lighting systems operate their LED above a junction temperature of 85°C and space apart from the LED, components of the LED lighting system that reduce an expected lifetime of the LED lighting system to less than 25,000 hours as a result of operating the LED above the junction temperature of 85°C. Accordingly, the LED itself may be driven hotter than is conventionally the case, without impacting its lifetime. By allowing the LED to operate hotter, reduced heat sinking may be needed for the LED itself, which can decrease the cost, size and/or complexity of the thermal management system for the LED lighting system and/or can allow a thermal budget for the LED lighting system to be used elsewhere. Related structures are also described.