LED Driver Current Regulator for Flicker Elimination
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Solution Overview
Problem
Non-isolated LED driver circuits are susceptible to line noise, leading to undesirable flicker in LED light output due to asymmetrical alternating cycles and rising/falling edge mismatches, which existing solutions like electrolytic capacitors cannot effectively address without compromising compactness and cost.
Innovation Solution
The implementation of a method that synchronizes a timer with the AC voltage waveform to generate integration outputs for separate portions of the cycle, using electrically variable resistors to mitigate voltage source variations, and employing multiple integrators or a microprocessor to moderate the LED load conditions independently for each segment of the wave cycle, eliminating the need for electrolytic capacitors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a massive electrolytic capacitor is used to compensate for short-term fluctuations and eliminate flicker, then flicker is reduced, but the device size and cost increase significantly
Solution Approach 1:
The patent divides the AC line voltage cycle into separate segments (half-cycles or quarter-cycles) and uses separate integrators for each segment. This segmentation allows the circuit to address asymmetry in different portions of the waveform without requiring a single large capacitor to handle the entire cycle, thereby reducing overall component size while maintaining flicker elimination effectiveness.
Solution Approach 2:
The patent employs dynamic switching between different integrators based on the detected phase of the AC line voltage. By dynamically selecting which integrator is active during each half-cycle or quarter-cycle, the system can respond to short-term fluctuations and asymmetry in real-time, achieving flicker reduction with smaller, more efficient components rather than a static large capacitor.
2Reliability
If separate integrators are used for each half-cycle or quarter-cycle, then short-term fluctuations and asymmetry are compensated, but circuit complexity increases
Solution Approach 1:
The patent segments the AC cycle into manageable portions (half-cycles or quarter-cycles) and assigns dedicated integrators to each segment. This segmentation approach allows the circuit to handle asymmetry and short-term fluctuations in each portion independently, improving compensation effectiveness while keeping each individual integrator simpler and more manageable.
Solution Approach 2:
The patent implements preliminary detection of the AC line voltage waveform characteristics before processing. By detecting the waveform and determining the appropriate integrator to use in advance, the system prepares the correct integration path beforehand, reducing the complexity of real-time decision-making and simplifying the overall control logic despite using multiple integrators.
3Reliability
If integration time constant is increased for good regulation, then voltage regulation improves, but the circuit cannot respond to short-term fluctuations
Solution Approach 1:
The patent segments the integration process into multiple shorter integration intervals corresponding to different half-cycles or quarter-cycles of the AC waveform. By using separate integrators for each segment with appropriate time constants, the system achieves good voltage regulation within each segment while maintaining the ability to respond quickly to short-term fluctuations between segments, effectively resolving the speed-regulation trade-off.
Data Source
AI summary
A current regulator for non-isolated, line voltage LED Driver circuits solves the problem of LED flicker caused by line noise in the visible frequency range. In one aspect of the invention, LED flicker frequency may be increased beyond the line frequency. In another aspect, line voltages in excess of LED voltage ratings may be tolerated. The driver may be implemented using discrete circuit elements or in software and utilizes separate current regulation for different segments of an AC line voltage cycle.