A Probabilistic Approach of Designing Driving Circuits for Strings of High-Brightness Light Emitting Diodes

Bhattacharya, Avik; Lehman, Brad; Shteynberg, A.; Rodríguez, Hernán

doi:10.1109/pesc.2007.4342204

Cited by 20 publications

(20 citation statements)

References 4 publications

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“…The variation of forward voltage drops are assumed to be a random variable, so placing a large number of devices in series will cause the random variables to sum together, and this has the effect of lowering the standard deviation of the forward voltage drop across the whole LED load. Therefore, a statistical approach can be done instead of designing the load in worst-case conditions [12] [12].…”

Section: Hb-leds and Load Designmentioning

confidence: 99%

A Universal-Input Single-Stage High-Power-Factor Power Supply for HB-LEDs Based on Integrated Buck-Flyback Converter

Gacio

Alonso

Calleja

et al. 2009

2009 Twenty-Fourth Annual IEEE Applied Power Electronics Conference and Exposition

132

110

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Due to the high rise in luminous efficiency that HBLEDs have experienced in the last recent years, many new applications have been researched. In this paper, a streetlight LED application will be covered, using the Integrated BuckFlyback Converter developed in previous works, which performs power factor correction (PFC) from a universal ac source, as well as a control loop using the LM3524 IC, which allows PWM dimming operation mode.Firstly, the LED load will be linearized and modeled in order to calculate the IBFC topology properly. Afterwards, the converter will be calculated, presenting the one built in the lab.Secondly, the converter will be modeled in order to build the closed loop system, modeling the current sensor as well in order to develop an adequate controller.Finally, experimental results obtained from the lab tests will be presented.

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Section: Hb-leds and Load Designmentioning

confidence: 99%

A Universal-Input Single-Stage High-Power-Factor Power Supply for HB-LEDs Based on Integrated Buck-Flyback Converter

Gacio

Alonso

Calleja

et al. 2009

2009 Twenty-Fourth Annual IEEE Applied Power Electronics Conference and Exposition

132

110

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“…The first step will be to obtain the forward voltage deviation for a given sample size from the data provided by the manufacturer. Since LED lamps composed by 60 emitters are considered, this estimation will allow the statistical deviation from the typical value to be determined in order to consider whether the average forward voltage is a good estimator [7]. This way, the characteristics of LEDs follow a statistical distribution that is approximately Gaussian [7], [9].…”

Section: Statistical Characterization Of Ledsmentioning

confidence: 99%

“…Since LED lamps composed by 60 emitters are considered, this estimation will allow the statistical deviation from the typical value to be determined in order to consider whether the average forward voltage is a good estimator [7]. This way, the characteristics of LEDs follow a statistical distribution that is approximately Gaussian [7], [9]. Nevertheless, it can be considered that the assumption of a Gaussian distribution is satisfactorily accurate even for a narrow bin [7] or simply, by the Central Limit Theorem, a Gaussian distribution could be assumed.…”

Section: Statistical Characterization Of Ledsmentioning

confidence: 99%

“…Other techniques use coupled inductors or coupling capacitors in order to balance the current mismatches [4], [5], [6]. A resistor-based equalizing circuit was presented in [7] achieving a 30% better efficiency through resistors optimized by a statistical study of LEDs.…”

Section: Introductionmentioning

confidence: 99%

“…The technique proposed in [7] will be taken as a basis and will be applied to the LED series parasitic resistance.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

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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Electrical model formulation for multicolor light‐emitting diode modules and its application to design dimmable driver

Bakshi¹,

Roy

2021

Circuit Theory & Apps

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A multicolor light-emitting diode (LED) module comprises LED chips of more than one type or color and is frequently used for spectrally tunable lighting applications. In this paper, electrical models of such multicolor LED modules are formulated taking two basic circuit configurations into account, namely, (i) conventional, where a parallel string is made of one particular LED type, and (ii) nonconventional, where a parallel string is composed of different LED types. For deriving the model equations, the basic exponential model of a single LED chip has been applied, which is experimentally found to be the suitable option out of the four existing models, namely, linear, parabolic, exponential, and modified Shockley models. The formulated models are experimentally validated, results of which show maximum deviations of 4.71% and 4.19% from the measured data in the nonlinear and the linear operating regions, respectively. The formulated models are utilized to design dimmable, isolated LED drivers for red-green-blue (R-G-B) LED module. Performance evaluation of the drivers is conducted in Matlab-Simulink. The results reveal the satisfactory operation of the LED modules in terms of current and power regulation, branch current matching, and fast response and thus establish the effectiveness of the proposed algorithm.

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A Probabilistic Approach of Designing Driving Circuits for Strings of High-Brightness Light Emitting Diodes

Cited by 20 publications

References 4 publications

A Universal-Input Single-Stage High-Power-Factor Power Supply for HB-LEDs Based on Integrated Buck-Flyback Converter

A Universal-Input Single-Stage High-Power-Factor Power Supply for HB-LEDs Based on Integrated Buck-Flyback Converter

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

Electrical model formulation for multicolor light‐emitting diode modules and its application to design dimmable driver

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