Multi-Stage LED Driver with Charge Storage for Flicker Reduction
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Solution Overview
Problem
LED lighting devices driven by rectified AC voltage face limitations in operational voltage range and reliability, leading to flicker issues due to varying rectified voltage levels, which can impact human health and device performance.
Innovation Solution
The implementation of a multi-stage driving system with current controllers and charge storage units to regulate currents and maintain luminescent devices in an on-state during insufficient voltage, ensuring consistent light output and reducing flicker.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the number of LEDs is increased to provide required luminance, then the luminance output is improved, but the forward-bias voltage requirement increases thereby reducing the effective operational voltage range
Solution Approach 1:
The patent divides the LED array into multiple strings with different numbers of series-connected LEDs. Each string is configured to operate at different voltage levels, allowing the system to adapt to a wider voltage range while maintaining required luminance output.
Solution Approach 2:
The patent implements dynamic switching between different LED string configurations based on the input voltage level. The controller selectively activates appropriate strings to optimize both luminance output and voltage compatibility, making the system adaptable to varying voltage conditions.
2Adaptability or versatility
If the number of LEDs is decreased to broaden voltage range, then the effective operational voltage range is improved, but the large driving current at maximum rectified voltage impacts LED reliability
Solution Approach 1:
The patent segments the total LED count into multiple smaller strings that can be selectively activated. This allows the system to use fewer LEDs at high voltage conditions while maintaining reliability, and more LEDs at lower voltage conditions to maintain luminance requirements.
Solution Approach 2:
The patent changes the operational parameters by switching between different LED string configurations. At maximum rectified voltage, the system activates strings with fewer LEDs to limit current and protect reliability. At lower voltages, it activates strings with more LEDs to maintain luminance output.
3Device complexity
If LEDs are directly driven by rectified AC voltage, then the device simplicity is improved, but the varying rectified voltage levels cause flicker that impacts human health
Solution Approach 1:
The patent ensures continuous light output by configuring multiple LED strings with different voltage requirements. As the rectified AC voltage varies during its cycle, the system continuously activates appropriate strings to maintain steady luminance, eliminating flicker while keeping the overall device relatively simple.
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 solution enhances the effective operational voltage range, improves reliability, and significantly reduces flicker in LED lighting devices, providing a more stable and healthier lighting experience.
Implementation Method 1
a first charge storage unit coupled in parallel with at least the first luminescent device and configured to discharge energy to the first luminescent device when the rectified AC voltage is insufficient to turn on the first luminescent device
Implementation Method 2
a first luminescent device driven by a rectified AC voltage for providing light according to first current
Data Source
AI summary
An LED lighting device includes multiple luminescent devices driven by a rectified AC voltage. The multiple luminescent devices are turned on flexibly in a multi-stage driving scheme using multiple current control units. At least one charge storage unit is coupled in parallel with at least one luminescent device. When the rectified AC voltage is still insufficient to turn on the at least one luminescent device, the at least charge storage unit is configured to discharge energy to the at least one luminescent device, thereby keeping the at least one luminescent device turned on.