Lighting Fixture Housing with Segmented Back Wall for Thermal Management
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Solution Overview
Problem
Existing lighting fixture housings face inefficiencies in heat transfer due to required air gaps between uninsulated current carrying elements of the PCB and metal heat sinks, which hinder effective heat dissipation as per UL spacing requirements.
Innovation Solution
A housing design with a back wall and sidewall that defines a cavity, where the upper section of the back wall is elevated to create an air gap of at least 0.063 inch between uninsulated electrical elements of the PCB and the housing, allowing for efficient heat transfer while meeting safety spacing requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a metal heat sink is positioned close to the PCB for efficient heat transfer, then heat dissipation efficiency is improved, but safety requirements mandate air gaps between uninsulated current carrying elements and the metal heat sink, reducing heat transfer efficiency
Solution Approach 1:
The back wall is segmented into an upper section and a lower section with different functions. The lower section provides thermal contact with the PCB for heat dissipation, while the upper section is elevated to maintain the required air gap for safety spacing. This segmentation allows the housing to simultaneously achieve efficient heat transfer and compliance with safety requirements.
Solution Approach 2:
Different portions of the back wall have different properties: the lower section is positioned close to the PCB to maximize thermal contact area for efficient heat transfer, while the upper section is elevated to create adequate air gap for safety spacing. This local differentiation of properties allows the structure to fulfill both thermal management and safety requirements in different regions.
2Reliability
If an air gap is maintained between uninsulated current carrying elements and the housing to meet UL spacing requirements, then safety is improved, but heat transfer from the PCB to the housing becomes less efficient
Solution Approach 1:
The back wall is divided into upper and lower sections with distinct functions. The lower section maintains close proximity to the PCB to ensure efficient heat transfer, while the upper section is elevated to provide the required air gap for safety spacing compliance. This segmentation resolves the contradiction by assigning different spatial relationships to different portions of the same structure.
Solution Approach 2:
The design addresses the two-dimensional conflict between safety spacing and heat transfer by introducing a vertical dimension through the elevated upper section. The back wall transitions from a flat surface to a multi-level structure, utilizing the vertical dimension to simultaneously achieve close thermal contact in the lower region and adequate air gap in the upper region.
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 housing enables effective heat dissipation from the PCB to the housing, ensuring compliance with safety standards and maintaining operational efficiency at high voltages.
Implementation Method 1
an uninsulated electrical element on a back side of the PCB is separated by an air gap from a closest point on the housing by a distance that is at least 0.063 inch
Implementation Method 2
heat may be transferred from the PCB to the heat sink
Data Source
AI summary
A heat dissipating housing for a lighting device includes a back wall comprising an upper section and a lower section. The housing further includes a sidewall extending down from the upper section of the back wall. The back wall and the sidewall define a cavity of the housing. The upper section of the back wall is elevated from the lower section of the back wall such that when a printed circuit board (PCB) having an uninsulated electrical element on a back side of the PCB is in contact with the lower section of the back wall within the cavity, the uninsulated electrical element is separated from a closest point on the housing by an air gap and a distance that is compliant with an Underwriters Laboratories (UL) spacing requirement. The back side of the PCB faces the upper section of the back wall.