LED Color Temperature Control via Parallel String Segmentation
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Solution Overview
Problem
Existing dimmable LED lighting systems struggle to maintain a desired correlated color temperature (CCT) at lower dim levels due to the second string of LEDs remaining powered, which prevents the combined light from reaching the desired CCT.
Innovation Solution
A lighting device configuration where a first group of LEDs emits a first light with a lower CCT and a second group emits a higher CCT, with an active electrical component and a switch in series, allowing the first group to maintain conductivity while the second group is turned off during dimming, ensuring the CCT remains consistent by adjusting the voltage and current flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the current provided to the strings of LEDs is reduced to dim the combined light, then the illumination intensity is reduced, but the second string of LEDs remains powered on which prevents the CCT from reaching the desired CCT
Solution Approach 1:
The patent divides the LED lighting system into two separate parallel strings: a first string with LEDs emitting a first CCT and a second string with LEDs emitting a second CCT. This segmentation allows independent control of each string's contribution to the combined light output, enabling precise CCT management at different dim levels by selectively powering or adjusting individual strings.
Solution Approach 2:
The patent implements dynamic control where the lighting device adjusts the operation state of the second LED string based on the dim level. At lower dim levels, the second string is turned off to allow the combined light CCT to reach the desired warmer temperature, while at higher dim levels both strings operate to maintain the cooler CCT. This dynamic switching resolves the contradiction between maintaining illumination and achieving target CCT.
2Manufacturing precision
If the second string of LEDs is turned off to achieve desired CCT at low dim levels, then the CCT accuracy is improved, but the device complexity increases due to additional control circuitry
Solution Approach 1:
The patent employs a dimming control circuit that performs multiple functions: it controls the overall illumination level of the lighting device and simultaneously manages the selective activation/deactivation of the second LED string based on the dim level. This multi-functionality allows the same control circuitry to address both illumination control and CCT management, reducing the need for separate dedicated circuits and thereby minimizing additional complexity.
Solution Approach 2:
The patent combines the CCT control function with the existing dimming control function in a unified control mechanism. The dimming circuit is designed to inherently manage the second LED string's operation state based on the dim level, merging two control objectives (illumination control and CCT control) into a single integrated control system, thus avoiding the need for separate complex control circuits.
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
Enables the lighting device to maintain a desired CCT at lower dim levels by ensuring the first group of LEDs continues to emit light while the second group is deactivated, effectively transitioning the combined light's CCT from cool white to warm white as dimming occurs.
Implementation Method 1
a first group of light emitting diodes (LEDs) that are in series with each other and that emit a first light having a first correlated color temperature (CCT). The lighting device further includes a second group of LEDs that are in series with each other and that emit a second light having a second CCT
Data Source
AI summary
A lighting device includes a first group of light emitting diodes (LEDs) that are in series with each other and that emit a first light having a first correlated color temperature (CCT). The lighting device further includes a second group of LEDs that are in series with each other and that emit a second light having a second CCT. The lighting device also includes an active electrical component in series with the second group of LEDs. The lighting device further includes a switch coupled in series with the second group of LEDs and the electrical component. The first group of LEDs is in a parallel configuration with the switch, the second group of LEDs, and the electrical component.