LED String Flicker Reduction via Energy Storage Module
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Solid-state lighting systems driven by rectified AC waveforms often experience flickering and reduced power factor due to the minimum forward voltage requirement of LEDs, and previous solutions like anti-parallel configurations require more LEDs to achieve the same luminous flux.
Innovation Solution
A lighting apparatus with a string of LED sets coupled in series, an energy storage module that stores energy during a peak interval of the power signal and applies it during a valley interval, and a notch circuit that disconnects the string during peak voltage to divert current to a storage element, ensuring all LED sets are turned on during the valley interval, thereby reducing flicker and increasing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If LEDs are driven by rectified AC waveform directly, then the circuit is simple, but the LEDs turn on only for part of the waveform causing visible flickering and reduced power factor
Solution Approach 1:
The energy storage module (capacitor) is charged during the peak voltage interval before the LEDs need operation. This preliminary energy storage ensures continuous power supply during valley intervals, eliminating flickering caused by intermittent LED activation on rectified AC waveforms.
Solution Approach 2:
The energy storage module acts as an intermediary between the rectified AC power source and the LED string. It buffers the power fluctuations, storing energy during peaks and releasing during valleys, thereby stabilizing the power delivery to LEDs without requiring complex active control circuits.
2Reliability
If anti-parallel LED configuration is used to drive LEDs on each half-cycle of AC waveform, then continuous illumination is achieved, but twice as many LEDs are required to produce the same luminous flux
Solution Approach 1:
Energy is stored in advance during the peak voltage interval when the power signal is strong, so that sufficient energy is available to drive all LED sets during the subsequent valley interval. This eliminates the need for anti-parallel configurations where only half the LEDs operate at any given time.
3Power
If LEDs are driven only during part of the rectified AC waveform, then forward voltage requirement is met, but resistive loss in the system increases
Solution Approach 1:
The energy storage module enables continuous useful action by ensuring the LED string receives power throughout the entire AC cycle. Instead of LEDs being off during valley intervals (causing power waste), the stored energy maintains continuous LED operation, eliminating unnecessary resistive losses from intermittent switching.
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 significantly reduces flicker and increases the frequency of the current signal through the LED sets, improving light uniformity and efficiency by ensuring all LED sets are turned on during the valley interval, with a dominant frequency of the current signal being at least three times that of the power signal.
Implementation Method 1
an energy storage module that is configured to store energy during a first interval of a period of the power signal and to apply the stored energy to the string during a second interval of the period of the power signal
Implementation Method 2
a notch circuit that is coupled to a node of the string and is configured to electrically disconnect the string from the power signal responsive to a voltage of the power signal exceeding a threshold, such as, for example, a summation of forward bias voltages of the respective LED sets and breakdown voltages of a pair of control Zener diodes
Data Source
AI summary
A lighting apparatus includes a string of Light Emitting Diode (LED) sets coupled in series, each set including at least one LED, a light spreading circuit configured to incrementally turn on respective ones of the LED sets responsive to a power signal, and an energy storage module that is configured to store energy during a first interval of a period of the power signal and to apply the stored energy to the string during a second interval of the period of the power signal.