LED String Driver Circuit Mitigating Flicker via Capacitive Energy Storage
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Solution Overview
Problem
Existing LED driving solutions, particularly direct AC drive methods, suffer from flicker issues in LED string luminosity, are limited by voltage and frequency ranges, require external reference voltages, and necessitate bulky components like transformers and capacitors, leading to inefficiencies and visual discomfort.
Innovation Solution
An electronic circuit that includes a rectifier, current regulator, electronic switch, capacitor, and bias stage, which regulates current and adjusts the capacitor's charging/discharging to mitigate flicker, allowing operation across a wide voltage and frequency range without external references or bulky components, and enables adjustable luminous flux.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If direct AC drive is used to avoid AC-DC converters, then device complexity and component size are reduced, but flicker in LED string luminosity occurs
Solution Approach 1:
A capacitor is introduced as an intermediary energy storage element between the AC input and the LED string. The capacitor charges during voltage peaks and discharges during voltage troughs, acting as a mediator that smooths the voltage waveform and eliminates flicker without requiring complex AC-DC conversion circuitry
Solution Approach 2:
The invention changes the voltage parameter by using a capacitor to store and release electrical energy, thereby modifying the voltage waveform characteristics. This parameter change smooths the alternating voltage applied to the LED string, eliminating flicker while maintaining direct AC drive simplicity
2Use of energy by moving object
If AC-DC converter is used to convert alternating voltage into direct voltage, then energy efficiency is improved, but device complexity and component size increase
Solution Approach 1:
The invention extracts and eliminates the complex AC-DC converter components (transformers, large inductors, capacitors) while retaining the essential function of voltage conversion through a simplified capacitor-based energy storage approach. This extraction reduces device complexity while maintaining energy efficiency
Solution Approach 2:
The capacitor provides self-service by automatically charging during voltage peaks and discharging during voltage troughs, eliminating the need for complex control circuits and large components. The system uses the inherent characteristics of the AC waveform to charge and discharge the capacitor, providing energy conversion without external intervention
3Object-affected harmful factors
If known direct AC drive solutions are used to reduce flicker, then flicker is partially reduced, but the solutions require external reference voltages or higher frequency alternating voltage
Solution Approach 1:
The capacitor-based solution is self-service and requires no external reference voltages. The system automatically adapts to the AC waveform characteristics, using the inherent voltage peaks and troughs to charge and discharge the capacitor, thereby eliminating flicker across the full range of AC voltages and frequencies without requiring external assistance
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
Significantly reduces or eliminates flicker in LED string luminosity, operates effectively with varying voltages and frequencies, eliminates the need for transformers and capacitors, and allows for adjustable brightness, enhancing reliability and user comfort.
Implementation Method 1
a capacitor (7) interposed between the first terminal of the LED string (5) and the electronic switch (6)
Data Source
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AI summary
It is disclosed an electronic circuit (1) for driving a string of light-emitting diodes (5). The circuit comprises a current regulator (4) comprising an input terminal configured to receive a rectified alternating voltage (VRTF) and comprising a plurality of input terminals (It1, It2, It3, It4) connected to respective different voltages selected from the string of light-emitting diodes, the current regulator being configured to regulate the value of the current flowing through the string of light-emitting diodes. The electronic driving circuit further comprises an electronic switch (6) configured to switch between a closed and an open position, as a function of the value of a control signal (Vg). The electronic driving circuit further comprises a bias stage (8) comprising an input terminal configured to receive a voltage selected from a voltage internal to the string of light-emitting diodes and comprising an output terminal configured to generate, as a function of the selected voltage, said control signal controlling the electronic switch. The electronic driving circuit comprises, finally, a capacitor (7) interposed between the electronic switch and the string of light-emitting diodes.