LED Lighting System Color Control via Forward Voltage
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Solution Overview
Problem
Existing LED lighting systems face challenges in maintaining target color and intensity stability over varying environmental temperatures without using color feedback, especially when controlling multiple LED emitters with different primary colors, which affects color rendering and efficiency.
Innovation Solution
A method involving a drive recursion loop that calculates and adjusts the drive settings for each LED emitter based on junction temperature and calibration data to maintain a target output color, using a memory to store calibration data for various drive settings and temperatures, allowing operation without color feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If PWM drive method is used to control LED intensity, then energy efficiency is improved, but electromagnetic interference and flickering problems occur
Solution Approach 1:
The patent changes the control parameter from time-averaged current (PWM duty cycle) to forward voltage. By controlling the forward voltage of each LED emitter, the system achieves intensity control without the electromagnetic interference and flickering issues associated with PWM current modulation, while maintaining energy efficiency.
2Object-affected harmful factors
If Constant Current regulation is used for LED driving, then flickering and EMI are reduced, but energy efficiency decreases and color variations increase
Solution Approach 1:
The patent transitions from constant current regulation to forward voltage control. This parameter change enables the system to maintain stable LED emission without flickering or EMI, while simultaneously improving energy efficiency and reducing color variations through precise voltage control of each emitter.
3Device complexity
If linear temperature-color models are used for LED control, then implementation simplicity is improved, but accuracy deteriorates over large temperature ranges
Solution Approach 1:
The patent implements preliminary calibration at multiple temperature points before actual operation. During calibration, the system measures the actual color output of each LED emitter at different temperatures and stores this data. During operation, the system retrieves and applies the appropriate calibration data based on measured temperature, maintaining high color accuracy across large temperature ranges without complex real-time calculations.
4Manufacturing precision
If color feedback with sensors is used to maintain target color, then color accuracy is improved, but system cost and complexity increase
Solution Approach 1:
The patent introduces junction temperature as an intermediary parameter that indirectly controls color accuracy. Instead of directly measuring color output with expensive sensors, the system measures junction temperature (a cheaper and simpler parameter) and uses pre-stored calibration data to determine the appropriate forward voltage control settings, achieving accurate color control without complex color feedback hardware.
5Manufacturing precision
If multiple LED emitters with different primary colors are used to achieve high CRI, then color rendering is improved, but control complexity increases
Solution Approach 1:
The patent segments the control of each LED emitter independently by controlling their forward voltages separately. This segmentation allows precise individual control of each emitter's contribution to the overall color output, enabling the system to achieve high CRI through additive color synthesis while maintaining simple and independent control pathways for each color channel.
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 approach effectively maintains specified target colors and intensities across temperature variations, improving color rendering and reducing energy inefficiencies, while being applicable to various LED driver schemes and casing designs.
Implementation Method 1
Light-emitting diodes (LED) light sources, emitting either white light or colored light
Implementation Method 2
As the LED dissipates heat when lit, the junction temperature is itself dependent on a number of parameters including the injected current, the junction voltage drop
Data Source
AI summary
A method for operating a LED lighting system has three or more LED emitters of different colors. The method allows finding the optimal drive setting for each LED emitter of the system, taking into account a specific target color. The method involves providing calibration data for each LED emitter at a plurality of values of drive setting and junction temperature, and executing a drive recursion loop calculating the drive setting of each emitter based on an input value for the temperature of each emitter and in view of the target output color and of the calibration data. Advantageously, this can be accomplished without measuring the color emitted by the LED lighting system, that is, no color feedback is required. A LED lighting system implementing the method is also disclosed.