LED Interference-Resistant Compensation Using Periodic Measurement
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Solution Overview
Problem
LED illumination devices face challenges in maintaining consistent luminous flux due to variations in temperature and aging, with existing compensation methods being prone to interference from nearby lamps, leading to inaccurate adjustments.
Innovation Solution
The method involves operating multiple emitter modules with varying drive currents during measurement intervals, using photodetectors to monitor photocurrents, and subtracting background currents to isolate the measurement photocurrent, thereby minimizing interference and accurately adjusting drive currents for consistent illumination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If compensation measurements are performed to maintain constant luminous flux, then LED aging and temperature effects are compensated, but interference from nearby lamps causes measurement errors
Solution Approach 1:
The patent implements periodic measurement intervals where LEDs are selectively turned on and off in a repeating cycle. During each period, only specific LEDs are activated for measurement while others remain off, creating a time-division multiplexed measurement scheme that eliminates mutual interference between adjacent LEDs and allows accurate photocurrent measurements despite the presence of nearby lamps.
Solution Approach 2:
The patent divides the LED array into separate groups or channels that are measured independently at different time intervals. By segmenting the measurement process into discrete intervals for different LED groups, the system可以避免 interference from other LEDs that are not currently being measured, thereby improving measurement accuracy in the presence of external light sources.
2Reliability
If drive current is increased to compensate for aging, then luminous flux is maintained, but temperature increases affecting measurement accuracy
Solution Approach 1:
The system performs compensation measurements periodically rather than continuously, allowing the LED to return to normal operating temperature between measurement cycles. The measurement intervals are designed to be brief and spaced sufficiently to prevent cumulative heating, ensuring that temperature effects do not significantly alter the measurement results while still providing regular compensation for aging effects.
Solution Approach 2:
The patent performs compensation measurements at controlled, lower drive currents before the LED reaches high operating temperatures. By conducting measurements during brief intervals when the LED is either off or at reduced current, the system obtains accurate baseline data before temperature-induced drift occurs, then applies compensation based on these pre-measured characteristics.
3Measurement precision
If measurement intervals are extended to improve accuracy, then measurement precision increases, but illumination continuity is disrupted
Solution Approach 1:
The system uses short, periodic measurement intervals repeated at fixed cycles rather than long continuous measurements. Each measurement pulse is brief enough to maintain illumination continuity while providing sufficient data for accurate photocurrent measurement. The periodic repetition accumulates measurement precision over time without causing noticeable interruption to the overall illumination output.
Solution Approach 2:
The patent employs brief measurement intervals that are sufficient for accurate measurement purposes but do not extend to the point of disrupting illumination. By using just enough measurement time to achieve required precision (not excessive time), the system maintains continuous illumination while obtaining adequate measurement data for compensation calculations.
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 ensures precise compensation for temperature and aging effects, reducing interference errors and maintaining consistent luminous flux in LED illumination devices.
Implementation Method 1
using photodetectors to monitor photocurrents
Data Source
AI summary
A method and light emitting diode (LED) illumination device comprising multiple emitter modules are provided. In one embodiment, the method includes bringing to a level insufficient to produce illumination the respective drive currents of all except one of multiple emission LED elements within respective first and second emitter modules for the duration of a measurement interval within respective first and second series of measurement intervals. The measurement intervals are interspersed with periods of illumination, and the first and second series of measurement intervals are separated by respective first and second offsets from a timing reference. An embodiment of an illumination device includes multiple emitter modules, where each emitter module includes multiple emission LED elements and one or more photodetectors. The illumination device further includes a lamp control circuit adapted to perform steps of the method.