White LED Current Zoning for Uniform Headlamp Chromaticity
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Solution Overview
Problem
In light-emitting devices for automobile headlamps, the emission chromaticity of LED units varies significantly between the central and surrounding areas due to current density differences, leading to inconsistent color rendition.
Innovation Solution
A white light emitting device is designed with two groups of LED units, each receiving different currents, where the first group is arranged in the central area and the second group in the surrounding area, using LED chips and phosphor members with specific chromaticity and intensity characteristics to maintain identical average emission chromaticities across both areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If different currents are applied to light-emitting units in the central and surrounding areas to achieve high luminance in the hot zone, then the luminance in the central area is improved, but the emission chromaticity becomes inconsistent between the central and surrounding areas
Solution Approach 1:
The patent applies different currents to light-emitting units in different spatial locations (central area vs. surrounding area) to create a hot zone with high luminance while managing chromaticity variations through localized current control
Solution Approach 2:
The patent changes the current parameter applied to different light-emitting units based on their position, with higher currents in the central area to achieve high luminance while accepting and managing the resulting chromaticity variations
2Stability of the object's composition
If the same current is applied to all light-emitting units, then the emission chromaticity is uniform across the device, but the luminance in the central hot zone is insufficient
Solution Approach 1:
The patent transitions from uniform current application to localized current differentiation, allowing the central area to receive higher currents for enhanced luminance while the surrounding areas receive lower currents
Solution Approach 2:
The patent introduces dynamic current distribution where different light-emitting units receive different current levels based on their functional requirements, moving from a static uniform approach to a dynamic differentiated approach
3Shape
If light-emitting units with different current densities are arranged to create a hot zone, then the light distribution pattern is improved, but the color consistency across the projection surface deteriorates
Solution Approach 1:
The patent creates a light distribution pattern with a hot zone in the central area by applying higher currents to central light-emitting units, accepting color variations as a trade-off for achieving the desired luminance distribution
Solution Approach 2:
The patent segments the light-emitting units into different groups (central area units vs. surrounding area units) with different current applications to achieve the hot zone effect while managing color consistency through grouped control
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 achieves a uniform emission chromaticity and high luminance in the central 'hot zone' while ensuring the surrounding area matches the central area's color, enhancing the light distribution pattern's consistency and effectiveness.
Implementation Method 1
each of the plurality of first light-emitting units includes a first light-emitting diode (LED) chip
Implementation Method 2
Each of the plurality of first light-emitting units includes a first light-emitting diode (LED) chip and a first phosphor member
Data Source
AI summary
A white light emitting device includes: first light-emitting units to which a first current is applied; and second light-emitting units to which a second current which is different from the first current is applied. When the first current is applied to the first light-emitting units and the second current is applied to the second light-emitting units, an average emission chromaticity of the first light-emitting units and an average emission chromaticity of the second light-emitting units are identical colors. When the same current is applied to both the first light-emitting units and the second light-emitting units, the average emission chromaticity of the first light-emitting units and the average emission chromaticity of the second light-emitting units are non-identical colors.