LED Lighting Device Color Consistency Control via Aging Compensation
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Solution Overview
Problem
LED-based lighting devices face challenges in maintaining color consistency over time due to differential aging of LEDs, which affects light intensity and color emission, particularly when used in multi-channel setups where warm white and cool white LEDs have different deterioration rates.
Innovation Solution
A controller is implemented to adjust the color ratio of LED channels based on measures of LED deterioration, tracking activation times and operating hours to ensure consistent color output by correcting the duty cycles of PWM signals for each channel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multi-channel LED-based lighting devices are used to emit colored light, then color rendering capability is improved, but color consistency over time deteriorates due to differential aging of LEDs in different channels
Solution Approach 1:
The controller continuously monitors the actual color output of the LED-based lighting device and compares it with the target color. Based on this feedback, the controller dynamically adjusts the drive currents for different LED channels to compensate for differential aging effects, thereby maintaining color consistency over time.
Solution Approach 2:
The system changes the operational parameters (drive currents) of individual LED channels based on their aging states. By adjusting the current distribution among different channels, the controller compensates for the different deterioration rates of warm white and cool white LEDs, ensuring stable color output.
2Reliability
If PWM signals with high frequency are used to control LED channels, then flickering is prevented, but control precision for color ratio adjustment is reduced
Solution Approach 1:
The system dynamically adjusts the duty cycle of PWM signals for different LED channels independently. By allowing flexible modification of duty cycle parameters while maintaining high frequency operation, the controller achieves both flicker prevention and precise color ratio control through real-time parameter optimization.
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 solution ensures color consistency by dynamically adjusting the color ratio in response to LED aging, maintaining the desired color appearance and intensity over the lifespan of the lighting device.
Implementation Method 1
a first LED channel comprising at least one LED arranged for emitting light at a first color; a second LED channel comprising at least one LED arranged for emitting light at a second color
Data Source
AI summary
A Light Emitting Diode, LED, based lighting device arranged to emit colored light, wherein said LED based lighting device comprises a first LED channel comprising at least one LED arranged for emitting light at a first color, a second LED channel comprising at least one LED arranged for emitting light at a second color, said second color being different to said first color, a controller arranged for activating said first LED channel and said second LED channel based on a color ratio such that said LED based lighting device emits light having a particular color, wherein said controller is further arranged for correcting said color ratio based on aging of said at least one LED in said first LED channel and on said at least one LED in said second LED channel, thereby ensuring color consistency of said particular color of said LED based lighting device over time.