AC LED Driver Circuit with Segmented Current Regulation
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Solution Overview
Problem
Existing LED drivers operating directly from AC input are complex and fail to effectively manage turn-on inrush current and overvoltage surges, which can damage LEDs, and they lack inherent current limiting capability and high power factor.
Innovation Solution
An LED driver circuit that operates directly from AC input with inherent current limiting capability and high power factor, utilizing multiple current regulators to control current through strings of LEDs, each active during specific voltage ranges to manage current flow and prevent damage from surges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If LED drivers operate directly from AC input, then the device becomes compact and low cost, but the current control circuit becomes complicated and fails to manage inrush current and overvoltage surges
Solution Approach 1:
The patent divides the AC cycle into multiple voltage ranges (first, second, and third voltage ranges) and assigns different current regulators to each range. This segmentation allows the circuit to manage different operational states with dedicated regulators, preventing inrush current and overvoltage surges while maintaining simplicity.
Solution Approach 2:
The patent implements preliminary action by activating current regulators in advance as voltage ranges are approached. The first current regulator activates before the second, which activates before the third, creating a staged startup sequence that prevents inrush current while maintaining circuit simplicity.
2Reliability
If multiple current regulators are used to control current through LED strings, then current management and protection improve, but circuit complexity increases
Solution Approach 1:
The patent makes the current regulators dynamic by controlling their activation based on the instantaneous voltage range. Each regulator is enabled or disabled according to which voltage range the AC input is currently in, allowing flexible current management without requiring all regulators to be physically present simultaneously.
Solution Approach 2:
The patent achieves multi-functionality by designing the current regulators to serve multiple purposes: they control current magnitude, prevent inrush current, and protect against overvoltage surges. This universal approach allows the same regulator structure to handle multiple protection functions without increasing overall circuit complexity.
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 provides a compact, cost-effective LED driver circuit that effectively manages current flow, prevents damage from inrush currents and overvoltages, and maintains a high power factor, ensuring efficient and reliable LED operation.
Implementation Method 1
a rectifier circuit that receives an AC voltage and that produces a rectified DC voltage. The rectified DC voltage has a sinusoidal magnitude during each half-cycle of the AC voltage.
Data Source
AI summary
An LED driver circuit controls the currents through a plurality of strings of light-emitting diodes (LEDs), which are connected in series. Each LED string has an associated current regulator. The LED strings are connected between the voltage rail and a reference rail on the output of an AC-to-DC rectifier to receive an unfiltered rectified DC voltage. A first current regulator is active during a first voltage range of the DC voltage to provide a current of a first magnitude to a first LED string only. A second current regulator is active during a second voltage range to provide a current of a second magnitude to the first LED string and to a second LED string. A third current regulator is active during a third voltage range to provide a current of a third magnitude to the first LED string, to the second LED string and to a third LED string.