LED Control Apparatus Ripple Signal Adjuster Flicker Reduction
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Solution Overview
Problem
Conventional light emitting device control apparatuses using full-wave rectified AC voltage to control LEDs result in flicker due to rapid turning-on and turning-off, which can cause user fatigue even if the flicker is not immediately noticeable.
Innovation Solution
A light emitting device control apparatus that includes a rectifier, a ripple signal adjuster to reduce the level difference between maximum and minimum ripple signal levels, and a turning-on controller to control the LEDs based on the adjusted drive signal, ensuring continuous operation even at lower ripple voltage levels, thereby reducing flicker.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If full-wave rectified AC voltage is used to control LEDs, then turning-on and turning-off control is achieved, but flicker occurs causing user fatigue
Solution Approach 1:
The patent applies preliminary action by turning on a predetermined number of LEDs in advance during the voltage valley section before the flicker occurs. This proactive approach ensures continuous light output and prevents flicker by maintaining LED operation during periods when voltage would otherwise be insufficient.
Solution Approach 2:
The patent implements continuity of useful action by ensuring that LEDs remain continuously on through coordinated control of multiple LED strings. When one LED string turns off during voltage peaks, other strings remain active, and predetermined strings turn on during valleys, maintaining uninterrupted light output and eliminating flicker.
2Productivity
If LEDs are turned on and off at short time intervals, then control efficiency is improved, but flicker is generated
Solution Approach 1:
The patent divides the LED lighting system into multiple independent LED strings (first, second, third, and fourth LED strings). Each string can be independently controlled based on voltage conditions, allowing the system to maintain high control efficiency while preventing flicker through distributed management of light output.
Solution Approach 2:
The patent employs periodic action by synchronizing LED string operations with the AC voltage cycle. LEDs are turned on during voltage peaks and turned off during voltage valleys in a periodic pattern that aligns with the power supply frequency, maintaining control efficiency while eliminating perceptible flicker through coordinated periodic switching.
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 solution effectively reduces flicker and associated user fatigue by maintaining LED operation at lower ripple voltage levels, while also decreasing the power factor and increasing total harmonic distortion within acceptable limits for high efficiency authentication.
Implementation Method 1
rectifies alternating current (AC) voltage into ripple voltage
Data Source
AI summary
A light emitting unit includes a plurality of light emitting devices. A control apparatus includes a rectifier for converting an alternating current (AC) signal into a ripple signal by rectifying the AC signal. A ripple signal adjuster reduces a level difference between maximum and minimum levels of the ripple signal, and outputs the resultant ripple signal as a drive signal. A turning-on controller controls turning-on of the light emitting devices in accordance with a level variation of the drive signal.