LED Control System Using Random Switching Periods
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Solution Overview
Problem
Existing systems for controlling LED light output are ineffective in environments with non-constant background light, leading to reduced color and brightness accuracy due to interference from external pulsed light sources with fixed frequencies.
Innovation Solution
A control system that randomizes the switching period of LEDs, using a random frequency to reduce interference from periodic external light sources, and includes a sensor unit to detect light output and provide feedback for adjusting the LED energizing based on a reference signal, with optional filtering to remove erroneous measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single optical sensor is used with time-multiplexed LED color switching to detect output, then device complexity is reduced, but measurement precision deteriorates due to interference from non-constant background light
Solution Approach 1:
The patent applies periodic action by using time-multiplexed switching of LED colors (blue, green, red) with specific measurement windows within each period. The sensor takes measurements at predetermined times during each switching period, allowing the system to distinguish between LED output and background light through temporal separation. This periodic switching pattern enables accurate color and brightness measurement using a single sensor without requiring multiple simultaneous sensors.
2Ease of operation
If fixed frequency switching is used for LED control, then ease of operation is improved, but reliability deteriorates due to interference from external pulsed light sources with matching frequencies
Solution Approach 1:
The patent implements dynamics by making the LED switching frequency variable rather than fixed. The control unit can adjust the switching frequency dynamically to avoid interference from external pulsed light sources. This allows the system to adapt to different environmental conditions and maintain measurement reliability by selecting switching frequencies that do not coincide with external interference sources, while still maintaining simple operation through automated frequency management.
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
The system provides a stable light output by minimizing interference from external pulsed light sources, maintaining accurate color and brightness even in non-constant environments, and can be implemented without additional hardware costs.
Implementation Method 1
a sensor unit adapted to detect the light output of the light emitting unit and provide a corresponding feedback signal
Data Source
AI summary
The present invention relates to a control system (12) for controlling the light output of a light emitting unit (10), which light emitting unit comprises at least one light emitting diode (LED) (14) and is adapted to emit light of at least one color, the control system comprising: a sensor unit (18) adapted to detect the light output of the light emitting unit and provide a corresponding feedback signal; and a control unit (22) adapted to control the light output of the light emitting unit based on a comparison between the feedback signal and a corresponding reference signal representing a desired light output, in order to provide an improved light output, wherein the control unit is further adapted to: determine a random switching period; determine on-time(s) for the LED(s) within the random switching period for providing the improved light output; and control energizing of the LED(s) according to the determined period and on-time(s). The present invention also relates to an LED light emitting unit arrangement, and a method for controlling the light output of an LED light emitting unit.