Sequential AC LED Driving for Flicker Reduction
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Solution Overview
Problem
Conventional LED lighting apparatuses using direct current (DC) driving face issues such as increased manufacturing costs, size limitations, reduced energy efficiency, and shortened lifespan due to the need for AC-DC power converters, and AC driving can cause power factor reduction and severe flickering due to non-light emitting sections of LEDs.
Innovation Solution
A sequential driving type AC LED lighting apparatus that controls LED drive current based on the number of LEDs in a preset group, using a rectification unit and an LED drive controller to maintain constant current in each operation section, thereby reducing light output deviation and improving flicker index.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If AC driving is used to eliminate AC-DC power converter, then manufacturing cost is reduced and lifespan is extended, but power factor is reduced and severe flickering occurs
Solution Approach 1:
The LED lighting apparatus divides LEDs into multiple groups (first LED group, second LED group, third LED group) that are driven sequentially in different operation sections. This segmentation allows the system to eliminate non-light-emitting sections by ensuring at least one LED group is always active, thereby resolving the flickering issue while maintaining AC driving benefits.
Solution Approach 2:
The control unit implements periodic switching of LED groups across different operation sections (first, second, third operation sections). By periodically transitioning between LED groups in a coordinated manner, the system maintains continuous light output and eliminates flickering while operating on AC power without traditional AC-DC converters.
2Object-affected harmful factors
If sequential driving of LED groups is implemented, then flicker index is improved, but light output deviation may occur between operation sections
Solution Approach 1:
The control unit dynamically adjusts the drive current for each LED group based on the operation section. In the first operation section, a first drive current is applied to the first LED group; in the second operation section, a second drive current is applied to the second LED group; and in the third operation section, a third drive current is applied to the third LED group. These parameter changes ensure that light output remains substantially equal across all operation sections, eliminating light output deviation while maintaining improved flicker index.
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 provides more natural-appearing light by minimizing light output deviation and flickering, achieving constant light output with improved flicker index by controlling LED drive current detection rather than voltage detection, enhancing power quality and efficiency.
Implementation Method 1
a rectification unit connected to an AC power source and outputting a first rectified voltage as a first drive voltage to an LED light emitting unit through full-wave rectification of AC voltage
Implementation Method 2
the LED light emitting unit comprising a first LED group to an nth LED group (n being a positive integer of 2 or more) and operated to emit light when receiving the first drive voltage from the rectification unit
Data Source
AI summary
A sequential driving type alternating current (AC) LED lighting apparatus including a rectifier connected to an alternating current (AC) power source and outputting a first rectified voltage as a first drive voltage to a light-emitting diode (LED) light-emitting device through full-wave rectification of an AC voltage, and an LED drive controller configured to detect a first drive voltage applied to the LED light emitting device and control sequential driving based on the detected first drive voltage. The LED drive controller is configured to set an LED drive current in each of operation sections, such that a difference between light output of the LED light-emitting device in each of the operation sections does not exceed a predetermined light output deviation.