LED Color Point Control via Tristimulus Derivation and PWM
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Solution Overview
Problem
Existing LED light sources using multiple colors struggle to accurately set a user-selected color point, especially when it falls outside the color selection range, leading to inefficiencies in applications like LCD backlighting and decorative lighting.
Innovation Solution
An integrated circuit that receives a user-selected color point in a device-independent color space, derives RGB tristimulus values, checks if it's within the LED light source's range, and generates pulse width modulated signals for the LED drivers to achieve the desired color, with error handling for unachievable color points.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If LED light sources use multiple colors (RGB LEDs) to create white light, then the versatility and adaptability of the light source is improved, but the difficulty of detecting and measuring the color point accurately worsens due to manufacturing variances and environmental changes
Solution Approach 1:
The patent implements a feedback mechanism where the controller continuously monitors the actual color output of the LED light source and compares it to the desired color point. Based on this feedback, the controller adjusts the drive signals to RGB LEDs in real-time, compensating for manufacturing variances and environmental changes. This closed-loop control system ensures accurate color point achievement despite the inherent variability of multiple LED components.
2Adaptability or versatility
If the system attempts to achieve any user-selected color point, then the adaptability is improved, but the reliability worsens when the color point is outside the achievable range due to manufacturing variances
Solution Approach 1:
The patent performs preliminary determination of the achievable color range based on the specific RGB LEDs installed in the light source. Before accepting user input, the system pre-calculates the gamut of colors that can be achieved with the given LED components. When a user selects a color point, the system checks it against this pre-determined range and either adjusts it to the nearest achievable color or notifies the user that the selected color cannot be achieved, thereby maintaining reliability.
3Ease of operation
If the system uses device-independent color space for user input, then the ease of operation is improved, but the device complexity increases due to color space conversion and tristimulus value derivation
Solution Approach 1:
The patent introduces an intermediary color processing layer that handles the complex color space conversions and tristimulus value derivations. The controller includes dedicated color processing circuitry that acts as a mediator between the simple user interface (which only needs to accept and display color selections) and the LED drive signals. This intermediary layer performs all the mathematically intensive color space transformations, isolating the complexity from both the user interface and the LED control logic.
4Reliability
If the system implements error checking for unachievable color points, then the reliability is improved, but the loss of time increases due to error flag setting and user notification
Solution Approach 1:
The patent performs error checking in advance by pre-determining the achievable color range based on the installed LEDs. When a user selects a color point, the system immediately checks it against the pre-calculated gamut boundaries. If the color point is outside the achievable range, the error flag is set instantly without requiring iterative adjustments or repeated measurements. This preliminary validation approach minimizes the time penalty for error handling while maintaining high reliability.
Data Source
AI summary
In one embodiment, a user-selected color point is received. RGB tristimulus values are then derived for the color point. It is also determined whether the user-selected color point is outside a color selection range of the LED light source and, if so, an error flag is set. Pulse width modulated signals for a plurality of LED drivers for the LED light source are also generated. In another embodiment, tristimulus values representing a color of light produced by an LED light source are received. The received tristimulus values are then compared to tristimulus values corresponding to a user-identified color point. In response to the comparison, pulse width modulated signals are generated for a plurality of LED drivers for the LED light source. After a predetermined number of repetitions of these actions, an error flag is set if the user-selected color point has not been achieved by the LED light source.