Solid State Lighting Control Circuit for Planckian Locus Dimming
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Solution Overview
Problem
Solid state lighting systems struggle to maintain color consistency and accurately reproduce color across varying brightness levels, particularly when dimmed, as they often fall below the Planckian locus, resulting in undesirable color temperatures.
Innovation Solution
Incorporating a control circuit with a bypass circuit that adjusts current distribution among LEDs, including red/orange, Blue-Shifted-Yellow, and amber LEDs, to vary color temperature in conformance with the Planckian locus during dimming, using variable resistance circuits to bypass current around certain LEDs and increase it through others, thereby maintaining color consistency and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If solid state lighting systems are dimmed to low brightness levels, then energy consumption is reduced, but color temperature deviates from the Planckian locus resulting in undesirable color appearance
Solution Approach 1:
The lighting system is segmented into multiple LED types with different spectral characteristics (warm white LEDs, blue LEDs, yellow LEDs). Each segment can be independently controlled to maintain color accuracy across different brightness levels. This segmentation allows the system to switch between different LED combinations depending on the desired brightness and color temperature.
Solution Approach 2:
The system dynamically changes the operational parameters (current distribution) of different LED types based on the brightness level. At lower brightness levels, the control circuit adjusts the current ratio between warm white LEDs and blue/yellow LEDs to compensate for the deviation from Planckian locus, thereby maintaining accurate color temperature despite reduced energy consumption.
2Stability of the object's composition
If multiple LED types are combined to achieve accurate color rendering, then color consistency is improved, but device complexity increases
Solution Approach 1:
The control circuit is designed to perform multiple functions: it manages current distribution among different LED types, maintains color accuracy across brightness levels, and ensures operation along the Planckian locus. This multi-functionality reduces the need for separate control mechanisms for each LED type, thereby managing complexity while achieving color consistency.
Solution Approach 2:
The system incorporates feedback mechanisms where the control circuit continuously monitors the output of multiple LED types and adjusts current distribution accordingly. This feedback ensures that color consistency is maintained across different brightness levels by dynamically balancing the contribution of each LED type based on their spectral characteristics and the desired color temperature.
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 solution ensures that the light produced by the system closely follows the Planckian locus over a wide range of dimming levels, providing a more natural and pleasing color temperature, similar to incandescent lighting, by introducing an additional v′ component through amber LEDs when necessary.
Implementation Method 1
A solid state light emitting device may include, for example, a packaged light emitting device including one or more light emitting diodes (LEDs)
Implementation Method 2
which may include inorganic LEDs, which may include semiconductor layers forming p-n junctions
Data Source
AI summary
A lighting apparatus having a plurality of light-emitting devices (LEDs) can include at least one first LED that is configured to emit first chromaticity light, at least one second LED that is configured to emit second chromaticity light, and at least one additional LED that is configured to emit third chromaticity light. A control circuit can be operatively coupled to the plurality of light-emitting devices and configured to cause a color temperature produced by the plurality of LEDs to vary substantially in conformance with a Planckian locus in response to a dimming control input less than about 1800K.