LED Driver Phase Diversity for Flicker Reduction
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Solution Overview
Problem
Existing LED light source drivers face challenges in minimizing perceivable flickering and variations in light output at low duty cycles, leading to potential stroboscopic effects and inaccurate intensity control.
Innovation Solution
A driver apparatus and method that adjust the duty cycle of the driving current based on flicker detection, using a power source and control portion to modify the driving current characteristics, ensuring the average current corresponds to the requested light level, and incorporating a flicker detection mechanism to adjust the phase or switch to linear control if necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If low PWM frequency is used to reduce switching losses and improve efficiency, then energy efficiency is improved, but perceivable flickering and stroboscopic effects occur due to too long off periods
Solution Approach 1:
The patent divides the lighting system into multiple independent LED strings, each controlled by its own PWM signal with different phases. This segmentation allows the system to maintain lower PWM frequencies for energy efficiency while the combined output of multiple strings reduces perceivable flickering through phase diversity.
Solution Approach 2:
The patent employs periodic PWM signals with different phases for controlling multiple LED strings. By using periodic action with varied phase offsets, the system achieves continuous light output that minimizes flicker perception while maintaining energy-efficient low-frequency switching.
2Object-affected harmful factors
If high PWM frequency is used to eliminate perceivable flickering, then flickering is reduced, but inaccurate control of light intensity occurs due to switching operation of power converters
Solution Approach 1:
By segmenting the control into multiple lower-frequency PWM signals with different phases, the system avoids the high-frequency switching inaccuracies while still achieving smooth combined light output that eliminates perceivable flickering.
Solution Approach 2:
The patent changes the control parameters by using multiple PWM frequencies and phase offsets instead of a single high frequency. This parameter transformation allows the system to achieve flicker-free operation with improved intensity control accuracy by operating at optimized lower frequencies.
3Object-affected harmful factors
If multiple LED strings are driven with PWM signals of different phases to reduce flickering, then perceivable flickering is reduced, but device complexity increases
Solution Approach 1:
The patent merges multiple PWM control signals into a unified control architecture that manages multiple LED strings. By combining the control functions and using shared components, the system reduces flickering through phase-diversified strings while minimizing the increase in overall device complexity.
Solution Approach 2:
The driver apparatus is designed with multi-functional capabilities to control multiple LED strings with different PWM parameters. This universal control architecture handles phase modulation, frequency control, and intensity regulation across multiple strings, reducing flickering without proportionally increasing complexity.
Data Source
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Figure 5a(a)~5b(f)
AI summary
According to an example embodiment, a driver apparatus for providing a driving current for one or more LEDs is provided. The apparatus comprises a power source portion for providing the driving current, the power source portion arranged to provide, when enabled, the driving current at a first level and a control portion for controlling the provision of the driving current to provide light output at a requested light level, the control portion configured to issue one or more control signals comprising a duty cycle based control signal to cause cyclically enabling and disabling provision of the driving current such that the average driving current corresponds to said requested light level, wherein the control portion is configured to modify characteristics of the driving current, in response to an indication of observed flickering of light in a location served by said one or more LEDs, such that the average driving current continues to correspond to said requested light level.