LED Backlight Calibration via Dual Feedback Control
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Solution Overview
Problem
Existing LED control systems face challenges in stabilizing the color and brightness of backlight modules due to color shift issues, as they cannot directly calibrate the combined light output of RGB LEDs, leading to instability in the light source.
Innovation Solution
A method and system that calibrate monochromatic light beams by providing reference values, sensing light signals, comparing them to generate calibration adjustments, and using a control device to adjust the LEDs' output, incorporating a light sensing module, reference value generating device, chroma comparison device, and brightness comparison device for closed-loop control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If only three fundamental color RGB sensor signals are used as feedback signal, then the system complexity is reduced, but the brightness value of the outputted light cannot be obtained directly and feedback control on the light source cannot be performed
Solution Approach 1:
The patent segments the feedback control into two independent parts: chroma feedback control using RGB sensor signals and brightness feedback control using a separate photosensor. This segmentation allows each sensor to specialize in measuring its specific parameter without interference, resolving the contradiction between system simplicity and measurement accuracy.
Solution Approach 2:
The patent introduces a photosensor as an intermediary device to directly measure the brightness of the white light output. This intermediary component bridges the gap between the LED light source and the brightness measurement, enabling direct feedback control without requiring complex calculations from RGB signals.
2Device complexity
If the brightness value is calculated from respective brightness values of three fundamental colors RGB, then the system structure is simplified, but the feedback control on the light source output cannot be truly performed
Solution Approach 1:
The patent implements a dual feedback mechanism where chroma feedback from RGB sensors and brightness feedback from a photosensor work together. The brightness feedback directly measures the actual light output and feeds it back to the control system, creating a reliable closed-loop control that truly stabilizes the light source output.
Solution Approach 2:
The patent replaces the computational approach of calculating brightness from RGB values with a direct optical measurement approach using a photosensor. This substitution of measurement mechanism provides more accurate and reliable brightness data for feedback control.
3Use of energy by moving object
If LEDs are used as light source with temperature changes or prolonged use, then the brightness of light output changes, but the overall brightness becomes unstable and color coordinates shift
Solution Approach 1:
The patent uses both chroma feedback from RGB sensors and brightness feedback from a photosensor to continuously monitor LED output. This dual feedback system detects changes in brightness and color caused by temperature or aging, and the control system adjusts the LED driving currents to compensate, maintaining stable output.
Solution Approach 2:
The patent dynamically adjusts the driving parameters (currents) of the RGB LEDs based on feedback from sensors. By changing these parameters in response to detected variations, the system compensates for temperature effects and aging, maintaining stable brightness and color coordinates.
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 stabilizes the color and brightness of the LED light source by directly calibrating the combined light output, improving the overall luminescence and color quality of the backlight module.
Implementation Method 1
sensing a plurality of first light signals of the plurality of monochromatic light beams outputted by the plurality of LEDs, sensing a second light signal of the light formed of the plurality of monochromatic light beams
Data Source
AI summary
To control chroma and brightness in a backlight module, a plurality of reference values of a plurality of monochromatic light beams are provided, and a brightness reference value is provided for the light formed of the monochromatic light beams. Then, a plurality of first light signals of the monochromatic light beams, and a second light signal of the light formed of the monochromatic light beams are sensed and compared with the reference values and the brightness reference value, respectively. Finally, the monochromatic light beams outputted by the plurality of LEDs is calibrated according to a comparison result of the plurality of first light signals with the plurality of reference values and a comparison result of the second light signal with the brightness reference value.