LED Driver Circuit for Low Flicker and Sinusoidal Current
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Solution Overview
Problem
AC-operated LED lights experience significant flickering due to the intermittent connection of LED chains over a sinusoidal AC voltage, leading to incomplete lighting and undesirable current consumption profiles that deviate from a sinusoidal curve, causing eye strain and operational inefficiencies.
Innovation Solution
A circuit design that incorporates a modified valley-fill circuit and switchable current sources, managed by a microcontroller, to ensure continuous lighting by adjusting the voltage and current supply to LED chains, maintaining a sinusoidal current profile and minimizing flickering, while optimizing transformer design and reducing heat generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If valley-fill circuit is used to reduce flickering, then lighting continuity is improved, but current profile deviates from sinusoidal shape
Solution Approach 1:
A controllable current sink is introduced as an intermediary component between the valley-fill circuit and the LED chains. This current sink absorbs the charging current of the valley-fill circuit, preventing it from distorting the overall current profile. The current sink acts as a mediator that decouples the flicker-reducing function from the power network, allowing the valley-fill circuit to operate without negatively impacting the sinusoidal current requirement.
2Stability of the object's composition
If multiple LED chains are switched on in stages, then flickering is reduced, but device complexity increases
Solution Approach 1:
The LED lighting system is divided into multiple independently controllable LED chains. Each LED chain can be switched on or off independently based on the instantaneous supply voltage level. This segmentation allows the system to maintain continuous lighting by ensuring at least one LED chain is always active, while simplifying the control logic to voltage-threshold-based switching.
Solution Approach 2:
The control unit continuously monitors the supply voltage and adjusts the switching state of each LED chain accordingly. When the supply voltage exceeds a predefined threshold, the control unit switches on additional LED chains; when it falls below the threshold, LED chains are switched off. This feedback mechanism enables automatic adaptation to voltage fluctuations without complex control algorithms.
3Stability of the object's composition
If valley-fill circuit charges above supply starting voltage, then lighting continuity is maintained, but heat generation increases
Solution Approach 1:
The controllable current sink serves as a heat-managing intermediary by absorbing the charging current during valley-fill operation. Instead of allowing this current to flow through the LED chains and generate excessive heat, the current sink provides a dedicated path for charge current, separating the charging function from the lighting function and reducing thermal stress on the LED components.
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 achieves low-flicker operation with continuous lighting, reducing eye strain and operational inefficiencies, and allows for smaller, cost-effective transformer designs, while maintaining a sinusoidal current profile and minimizing heat generation.
Implementation Method 1
n LED chains with a respective number of LEDs N
Implementation Method 2
the connected light-emitting diodes emit a light signal during this time
Data Source
Figure 1
AI summary
The invention relates to a circuit, in particular for operating light-emitting diodes having low flicker and in accordance with standards, having n LED chains having a respective LED number N, wherein n is an integer and greater than 1 and N is an integer and greater than 0, also having a total supply voltage connection, to which a time-dependent supply voltage, in particular rectified a.c. voltage, can be applied, and a LED chain circuitry, wherein the LED chain circuitry has a control device and the LED chain circuitry connects the individual LED chains in stages in the event of rising supply voltage and disconnects them in stages in the event of falling supply voltage. The circuit has a refill circuit, in particular a valley fill circuit, which below a quantitative supply voltage value supplies at least one of the LED chains having a voltage and/or having a current, wherein the circuit has a controllable and/or adjustable current sink, which reduces a supply current of the LED chain by a charging current of the refill circuit.