LED Panel Color Correction Using PWM Duty Cycle Balancing
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Solution Overview
Problem
Multiple strings of LEDs are difficult to balance in terms of power, brightness, temperature, and color due to production tolerances, resulting in inconsistent perceived colors across LED panels.
Innovation Solution
A color correction device with a computation engine and software application that computes adjustment values to achieve a reference color by modifying pulse width modulated (PWM) duty cycles, using a reference panel matrix and inverse target panel matrix to drive LEDs and produce uniform color across panels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If multiple strings of LEDs are used to increase brightness and coverage, then illumination intensity and area are improved, but color consistency and manufacturing precision deteriorate due to production tolerances
Solution Approach 1:
The patent applies local quality by individually adjusting the PWM duty cycle for each LED string based on its specific color characteristics. The system measures the actual color output of each string and applies unique correction factors, allowing each local component (LED string) to have customized control parameters that compensate for manufacturing variations while maintaining overall color consistency across the entire lighting system.
Solution Approach 2:
The system changes the PWM duty cycle parameter for each LED string to compensate for color variations. By dynamically adjusting this electrical parameter based on measured color data and pre-determined correction values, the system transforms the physical state of each LED string's light output to achieve uniform perceived color across all strings despite manufacturing tolerances.
2Manufacturing precision
If PWM duty cycles are adjusted for each LED string to achieve color consistency, then color uniformity is improved, but device complexity increases due to individual control requirements
Solution Approach 1:
The system performs preliminary action by pre-determining correction values for each LED string during initial setup or calibration. The microcontroller measures the actual color output of each string and calculates the necessary PWM duty cycle adjustments in advance, storing these correction values in memory. This preliminary configuration eliminates the need for complex real-time calculations during operation, reducing computational complexity while maintaining color uniformity.
Solution Approach 2:
The patent uses copying by creating a digital representation (lookup table) of the correction values for each LED string. Instead of performing complex color science calculations in real-time, the system copies pre-computed correction data into a searchable table structure, allowing rapid retrieval and application of the appropriate duty cycle adjustments based on the desired color point, thereby simplifying the control algorithm.
Data Source
AI summary
A color correction device includes a computation engine including a processor and a memory coupled to the processor. The computation engine is configured to receive reference color data. A software application stored in the memory and configured to compute adjustment values needed to achieve the reference color data from a target color. An output configured to output color corrected signals to light emitting diodes (LEDs) to achieve a reference color associated with the reference color data from the target color of the LEDs.