Programmable LED Driver with Feed-Forward Regulation
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Solution Overview
Problem
Solid state light sources face issues with line-voltage fluctuations, leading to varying light output and reduced lifespan due to temperature increases, and require programmable drivers for dimming and fault condition management without efficiency loss or system shutdown.
Innovation Solution
The development of programmable drivers with an isolated half-bridge resonant converter and feed-forward loop for improved output regulation, enabling extended dimming range, reduced flicker, and fault condition recovery without complete system restart, utilizing both digital and analog control loops for precise current regulation and fault detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If PWM dimming is used to reduce light output, then dimming capability is achieved, but color shift in the light output occurs
Solution Approach 1:
The patent implements a feedback mechanism that monitors the forward voltage of the solid state light source and adjusts the drive current accordingly. This feedback loop compensates for voltage fluctuations and maintains stable current through the LED, preventing color shift during dimming operations while preserving the desired illumination intensity levels.
Solution Approach 2:
The system dynamically changes operating parameters by adjusting drive current levels based on monitored forward voltage conditions. During dimming, the controller modifies current parameters while compensating for voltage changes, maintaining optimal color characteristics across different brightness levels without requiring physical hardware changes.
2Stability of the object's composition
If forward current is increased to compensate for voltage fluctuations, then light output stability is improved, but operating temperature increases reducing device lifespan
Solution Approach 1:
The control system continuously monitors forward voltage and adjusts drive current in real-time to maintain stable light output. This precise feedback control prevents over-compensation that would otherwise increase current and temperature, thereby extending device lifespan while maintaining light output stability under varying voltage conditions.
Solution Approach 2:
The system dynamically adjusts operating parameters based on real-time conditions rather than using fixed compensation values. The controller adapts current levels according to actual voltage fluctuations and thermal conditions, optimizing the balance between light output stability and temperature management to prevent premature device failure.
3Reliability
If analog primary side regulation is used for constant current control, then current regulation is achieved, but core losses and leakage inductance occur in low current range
Solution Approach 1:
The patent replaces traditional analog primary side regulation with a digital control system that uses PWM techniques. This substitution eliminates the core losses and leakage inductance problems associated with analog regulation in the low current range, while maintaining precise current regulation through digital processing and pulse-width modulation of the power switches.
Solution Approach 2:
The system uses periodic PWM switching actions to regulate current instead of continuous analog control. By switching the power devices in periodic pulses with variable duty cycles, the system achieves accurate current regulation across the full range including low current levels, while minimizing core losses and eliminating leakage inductance effects that plague analog approaches.
4Measurement precision
If digital control with high speed A2D converter is used for regulation, then processing accuracy is improved, but dead time between sampling and adjusting causes instability in low current level
Solution Approach 1:
The system performs preliminary actions by pre-calculating control parameters and preparing adjustment commands before they are needed. The digital controller anticipates required current adjustments and initiates PWM duty cycle changes in advance, compensating for the inherent dead time in the sampling and processing loop. This preliminary action maintains stability in low current conditions while preserving the high measurement precision of the A2D converter.
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 lifespan of solid state light sources by maintaining efficiency during dimming, reducing temperature, and providing a controllable restart feature that monitors load conditions, ensuring stable operation without user intervention.
Implementation Method 1
isolated half bridge resonant converter with an improved control approach designed to regulate very low current though primary side in a feed-forward loop. In some embodiments, this is an LCC resonant converter
Implementation Method 2
galvanic topologies with primary current regulation
Data Source
AI summary
Programmable drivers (or power supplies) for solid state light sources are disclosed, on which output regulation is improved to expand the dimming range to 1% and reduce and/or remove flicker. Additional fault conditions are set up to avoid latching, and thus provide for a controllable restart feature. Such drivers include an isolated half bridge resonant converter with an improved control approach designed to regulate very low current though primary side in a feed-forward loop. Such drivers include both digital and analog loops that improve the performance in steady state and/or during transients, particularly for a lighting load, in comparison to a single full digital control.