Dynamic LED String Segmentation for AC Voltage Matching
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Solution Overview
Problem
Conventional Direct AC driven LED lighting suffers from low efficiency, low frequency flicker, and low power factor due to inefficiencies in matching the 'ON' voltage of the LED string to the rectified AC voltage, leading to wasted power and suboptimal performance.
Innovation Solution
A device and method that dynamically adjust the number of LED diodes in the string by dividing it into major and minor segments, with a controller selectively enabling or disabling minor segments to match the 'ON' voltage to the rectified voltage, thereby improving power efficiency and reducing flicker.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the number of LED diodes in the string is fixed, then the circuit is simple to design and manufacture, but the voltage matching between LED string and rectified voltage is poor leading to low efficiency
Solution Approach 1:
The LED string is divided into multiple groups of parallel-connected LED diodes. Each group can be independently controlled by switching elements to be connected or disconnected from the circuit. This segmentation allows the effective number of LED diodes to be dynamically adjusted to match the rectified voltage level, minimizing voltage mismatch and improving power efficiency while maintaining a relatively simple overall circuit structure.
2Loss of energy
If the LED string voltage is always lower than rectified voltage, then the LED string can be continuously driven, but there is always extra voltage across the current source causing power waste
Solution Approach 1:
The circuit employs switching elements that dynamically adjust the configuration of LED diode groups based on the rectified voltage level. During different phases of the AC cycle, different numbers of LED diode groups are connected in parallel to the current source. This dynamic adjustment ensures that the LED string voltage closely matches the rectified voltage at any given moment, minimizing power waste while ensuring continuous reliable operation throughout the entire AC cycle.
3Loss of energy
If fewer LED diodes are used in the string, then the voltage requirement is lower and easier to match, but the light output is reduced
Solution Approach 1:
The circuit design allows the same LED string configuration to serve multiple functions: it can operate with different numbers of LED diode groups active depending on the rectified voltage level. This multi-functionality enables the system to optimize for either voltage matching efficiency or light output based on operating conditions, as the switching elements can configure the LED diodes to achieve the desired balance between these two objectives.
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 enhances power efficiency by closely matching the LED string voltage to the rectified voltage, reducing wasted energy and minimizing flicker, with power efficiency improvements exceeding 97% in some embodiments.
Implementation Method 1
The LED string has multiple LED diodes connected in series
Data Source
AI summary
An approach is provided for devices and methods for driving an LED light, which adjust the numbers of diodes of the LED string corresponding to the rectified AC voltage. The device comprises a power module, a LED string, a current source and a controller. The LED string has multiple LED diodes connected in series that forms a major segment and multiple minor segments. The controller is connected to the current source and the LED string, which selectively shorts the LED diodes of the minor segments. Since the number of LED diodes of the LED string is dynamically adjusted in response to the rectified voltage, the overall “on” voltage of the LED string is more closely matched to the rectified voltage, and thus the power efficiency is improved.