LED Controller Transient Correction for Precision Brightness
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Solution Overview
Problem
Current LED control systems face challenges in achieving precise current control due to transient behavior and manufacturing tolerances, leading to reduced contrast and increased minimal brightness levels, especially when using switch mode current sources.
Innovation Solution
A controller that receives an input signal, converts it, and applies corrections based on predetermined transient characteristics of the LED assembly, such as current transients, to improve correspondence between required and actual characteristics, thereby enhancing control and contrast.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If switch mode current sources are used to control LED assemblies, then power to light conversion efficiency is improved, but transient behavior causes mismatch between required and actual current characteristics
Solution Approach 1:
The controller measures the actual current through the LED assembly and compares it with the required current. Based on this feedback, the controller adjusts the duty cycle of the PWM signal to compensate for transient behavior and ensure the actual current matches the required current, resolving the precision issue while maintaining efficient switch mode operation
Solution Approach 2:
The controller predicts the transient response of the switch mode current source and pre-adjusts the duty cycle before the transient occurs. This preliminary compensation ensures that when the transient happens, the actual current already matches the required current, eliminating the mismatch caused by transient behavior
2Reliability
If minimum intensity is set high to ensure consistent behavior across different LEDs, then reliability is improved, but contrast is reduced
Solution Approach 1:
The controller continuously monitors the actual current and intensity output of each LED assembly. By comparing the measured intensity with the target intensity, the controller compensates for manufacturing tolerances and transient behavior, allowing each LED to operate at its true minimum intensity rather than forcing all LEDs to a higher conservative minimum, thereby restoring contrast while maintaining consistency
Solution Approach 2:
The controller dynamically adjusts operating parameters such as duty cycle and current levels based on real-time measurements of each LED assembly's actual characteristics. This allows the system to adapt to manufacturing tolerances and transient behavior, enabling lower minimum intensity settings while maintaining consistent performance across different LEDs
3Manufacturing precision
If correction based on transient characteristics is applied to control signal, then correspondence between required and actual characteristics is improved, but device complexity increases
Solution Approach 1:
The controller incorporates current sensing circuitry and a feedback loop that automatically measures actual current and adjusts the PWM duty cycle accordingly. This self-regulating feedback mechanism handles the complexity of transient compensation automatically without requiring external calibration or complex manual adjustments, making the added complexity manageable while achieving precise current control
Data Source
Figure 1a~1b
Figure 1c~1d
Figure 1e~2
AI summary
A controller for controlling an LED assembly is described. The controller is arranged to - receive an input signal representing a required characteristic of the LED assembly, - convert the input signal to a control signal for the LED assembly, - apply a correction to the control signal to obtain a corrected control signal, the correction being based on a predetermined transient characteristic of the LED assembly, - output the corrected control signal. As such, a better correspondence between a required characteristic and an actual characteristic of the LED assembly is obtained.