Evaluation of a Synchronous Flyback Driving Parallelized High Efficiency LEDs

High power LED (Light Emitting Diode) has a wide application in lighting for its good features. In this paper, the electrical properties of LED are first introduced, and then a series-parallel connection of LEDs with more stability and reliability is adopted on the basis of the features of parallel connection and series connection. After that, a flyback circuit for driving high power LED group with a constant-output-current is investigated, and the parameters are designed. According to the driving method, a circuit prototype with an output of 10.0V/1.10A is fabricated and tested in rated load and overload conditions to verify its current stability. Experimental results show that the LED drive circuit has a high accuracy, good stability and high efficiency, suggesting that the proposed method might be practical for driving high power LEDs.

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“…Such an occurrence affects the change of luminance of the LEDs. In a worst case scenario, the LEDs will continuously breakdown [13].…”

Section: B Type Of Connection For the Ledsmentioning

confidence: 99%

Research on High-Efficiency Driving Technology for High Power LED Lighting

Liu

Wang

Song

et al. 2010

2010 Asia-Pacific Power and Energy Engineering Conference

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“…However, the extra driver per LED string increases the cost, size and complexity of the entire system. Examples of such systems can be found in [1], [2], and [3].…”

Section: Introductionmentioning

confidence: 99%

Study on passive self-equalization of parallel-connected LED strings

Gacio¹,

Alonso

Garcia

et al. 2013

2013 International Conference on New Concepts in Smart Cities: Fostering Public and Private Alliances (SmartMILE)

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Parallel connection of several LED strings is a practical way to reduce the overall lamp voltage when a large number of emitters is needed. However, this connection might lead to high current mismatches between strings due to the dispersion of characteristics that even binned devices feature. Several techniques have been proposed in order to eliminate or, at least, reduce the forward current mismatch between paralleled strings. Provided that a cost-effective design is pursued, passive self-equalization of LED strings will be studied in this paper, where the dynamic resistance will be considered as the equalizing resistor. Thus, a statistical study will firstly be developed on four commercial devices in order to determine the forward voltage deviation in both binned and unbinned LEDs. Then, the dynamic resistance will accurately be determined for the operating current in a wide temperature range by the procedure followed in previous works, since this parasitic effect will be employed as the equalizing resistor. The I-V and R D -T j curves will be thus experimentally obtained for a large sample. Once the thermal and statistical characterizations are done, the study of the LED linear model will be performed in order to determine the impact on forward current mismatches that forward voltage and dynamic resistance variations imply in both binned and unbinned LEDs. Finally, experimental results will show that binned LEDs are suitable for self-equalization even for a tight current-mismatch tolerance, especially for a significant number of series-connected LEDs in each string.

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