LED Driver Supplementary Control for Flicker Reduction
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Solution Overview
Problem
LED flicker occurs at low dimming levels due to hysteresis in switched-mode power supplies, and existing solutions either increase energy losses or result in significant start-up delays and limited duty cycles.
Innovation Solution
An LED lighting driver with a supplementary control system that overrides the primary control system to maintain a predetermined current through an inductor, ensuring consistent current delivery to the LED, thereby minimizing flicker and reducing energy losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a higher switching frequency is used to decrease LED flicker, then LED flicker is reduced, but energy losses increase significantly
Solution Approach 1:
The supplementary control system pre-charges the inductor to a predetermined current level before the LED is switched on. This preliminary action ensures that when the LED turns on, the current is already at the required level, eliminating flicker without needing continuous high-frequency switching during operation, thus avoiding energy losses.
Solution Approach 2:
The control system is divided into two distinct parts: a primary control system for normal operation and a supplementary control system for pre-charging the inductor. This segmentation allows each system to operate optimally for its specific function, with the supplementary system only active during the brief pre-charge phase, minimizing overall energy consumption while ensuring reliable LED operation.
2Reliability
If synchronization of PWM signal to switched-mode power supply switching is implemented, then LED flicker is reduced, but start-up delay increases significantly
Solution Approach 1:
The supplementary control system performs the necessary inductor current setup in advance, before the main PWM signaling begins. This preliminary current establishment eliminates the need for time-consuming synchronization between the PWM signal and the power supply switching, as the inductor is already prepared with the required current level when the LED is activated.
3Reliability
If synchronization of PWM signal to switched-mode power supply switching is implemented, then LED flicker is reduced, but maximum duty cycle is limited
Solution Approach 1:
By separating the control into primary and supplementary systems with distinct functions, the invention removes the synchronization constraint that limited duty cycle. The supplementary system handles only the brief pre-charge operation, while the primary system manages the full-range PWM control, enabling the LED to operate at any duty cycle from 0% to 100% without synchronization restrictions.
4Reliability
If lower hysteresis of the switched-mode power supply is used to decrease LED flicker, then LED flicker is reduced, but energy losses increase
Solution Approach 1:
The supplementary control system establishes the inductor current at the precise predetermined level before LED activation, eliminating the need for tight hysteresis control during normal operation. This preliminary current setting ensures stable LED operation without requiring the power supply to maintain low hysteresis, which would otherwise cause excessive energy losses.
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 reduces LED flicker and minimizes energy losses while achieving fast start-up times and consistent light output, particularly effective at low dimming levels.
Implementation Method 1
a switched-mode power supply comprising: an inductor connectable to the lighting arrangement, wherein a current through the inductor defines a current through the lighting arrangement
Implementation Method 2
LED-based luminaires
Data Source
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AI summary
The invention provides a method and apparatus for overcoming LED flicker caused by an asynchronous control of an LED on or off state and a switched-mode power supply for the LED. There is provided a supplementary control system adapted to override a primary control system for the switched-mode power supply, and control an energy storage inductor of the switched-mode power supply. In particular, in response to an indicated desire to switch the LED on, the supplementary control system sets the current in the energy storage inductor to a predetermined level. In this way, when the LED is switched on, the current through the inductor is known and LED flicker is thereby reduced.