Performance Evaluation of a VLC Transmitter Based on the Split of the Power

IEEE Applied Power Electronics Conference and Exposition, San Antonio, (Estados Unidos de Norteamérica), marzo de 2018Visible Light Communication (VLC) has gained relevance during last years. It consists in using High-Brightness LEDs (HB-LEDs) both for lighting and for transmitting information changing the light intensity rapidly. However, there are some bottlenecks that are slowing down the deployment of this technology. One of the most important problems is that the HB-LED drivers proposed for addressing high data rates in VLC achieve poor power efficiency. Since these HB-LED drivers must be able to reproduce fast current waveforms, the use of Linear Power Amplifiers (LPAs) has been adopted, which clearly damage the power efficiency of HB-LED lighting. In order to alleviate this problem, a HB-LED driver made up of two DC-DC power converters is presented in this work. One of them is responsible for performing the communication functionality by operating at high switching frequency (10 MHz), whereas the second one fulfills the illumination functionality by ensuring a certain biasing point. The split of the power allows to minimize the power delivered by the fast-response DC-DC power converter. Thus, the efficiency can be maximized for scenarios with changing conditions (i.e., mobile transmitter and/or receiver, presence of mobile obstacles, etc.). In this sense, how the lighting level and the communication signal power affect both the power efficiency and the communication efficiency is deeply analyzed. The implemented prototype achieves an overall efficiency around 90%. In addition, the proposed VLC transmitter is able to reproduce a wide range of digital modulation schemes, including Orthogonal Frequency Division Multiplexing (OFDM

Desarrollo de un transmisor para comunicaciones en luz visible (VLC) basado en un convertidor CC/CC conmutado de respuesta rápida

XXIV Seminario Anual de Automática, Electrónica Industrial e Instrumentación 2017 (SAAEI'17), Valencia (España)En este artículo se presenta un sistema de transmisión de información usando luz visible (Visible-Light Communication, VLC) basado en un convertidor CC/CC conmutado de respuesta rápida y un sistema de caracterización en frecuencia de LEDs de alta eficiencia (High Brightness Light Emitting Diodes, HB-LED). Por una parte se presenta un sistema transmisor/receptor para caracterización en frecuencia de HBLEDs basado en un amplificador lineal como transmisor y un amplificador de transimpedancia y fotodiodo como receptor. Este sistema permite caracterizar la relación tensión/corriente/luz en frecuencia y permite el estudio de la utilidad de HB-LEDs en sistemas VLC. Debido a la baja eficiencia del amplificador lineal, se presenta además un convertidor CC/CC de respuesta rápida como propuesta de transmisor real para un sistema VLC con alta eficiencia y mayores niveles de potencia de transmisió

Efficient Visible Light Communication Transmitters Based on Switching-Mode dc-dc Converters

Visible light communication (VLC) based on solid-state lighting (SSL) is a promising option either to supplement or to substitute existing radio frequency (RF) wireless communication in indoor environments. VLC systems take advantage of the fast modulation of the visible light that light emitting diodes (LEDs) enable. The switching-mode dc-to-dc converter (SMCdc-dc) must be the cornerstone of the LED driver of VLC transmitters in order to incorporate the communication functionality into LED lighting, keeping high power efficiency. However, the new requirements related to the communication, especially the high bandwidth that the LED driver must achieve, converts the design of the SMCdc-dc into a very challenging task. In this work, three different methods for achieving such a high bandwidth with an SMCdc-dc are presented: increasing the order of the SMCdc-dc output filter, increasing the number of voltage inputs, and increasing the number of phases. These three strategies are combinable and the optimum design depends on the particular VLC application, which determines the requirements of the VLC transmitter. As an example, an experimental VLC transmitter based on a two-phase buck converter with a fourth-order output filter will demonstrate that a bandwidth of several hundred kilohertz (kHz) can be achieved with output power levels close to 10Wand power efficiencies between 85% and 90%. In conclusion, the design strategy presented allows us to incorporate VLC into SSL, achieving high bit rates without damaging the power efficiency of LED lightin

On the Role of Power Electronics in Visible Light Communication

The continuous demand of increasing data rates provided by wireless communication systems is contributing to saturating the RF spectrum. Visible Light Communication (VLC) systems aim to alleviate this congestion by using the visible light spectrum. These systems have been proposed to make use of High-Brightness LEDs (HB-LEDs) not only for lighting, but also for transmitting information by rapidly changing the intensity of the emitted light. A critical issue is that VLC requires a fast HB-LED driver in order to reproduce the target light intensity waveforms, which can include components of several MHz. Consequently, the HB-LED drivers proposed to date are based on the use of an RF Power Amplifier (RFPA). These devices provide the required speed, but suffer from very high power losses. To overcome this drawback, different solutions based on the use of fast-response DC/DC converters are presented in this paper. Several DC/DC converters, either to be used instead of an RFPA or to help an RFPA to achieve high efficiency, are thus analysed. The proposed HB-LED drivers enable the implementation of VLC transmitters without sacrificing one of the most important advantages of HB-LED lighting, namely its high power efficienc

Power-Efficient VLC Transmitter Able to Reproduce Multi-Carrier Modulation Schemes by Using the Output Voltage Ripple of the HB-LED Driver

2018 IEEE 19th Workshop on Control and Modeling for Power Electronics (COMPEL), 25-28 junio, Padua (Italia)Visible Light Communication (VLC) consists in using High-Brightness LEDs (HB-LEDs) not only for lighting, but also for transmitting information by changing the light intensity rapidly. One of the most important problems of VLC is that the HB-LED drivers that have been proposed for achieving the highest bit rates offer low power efficiency. The reason is that since these HB-LED drivers must be able to reproduce fast current waveforms, the use of Linear Power Amplifiers (LPAs) has been adopted, which damages the power efficiency of HB-LED lighting. To the author’s knowledge, there is only one approach reported in the literature that is able to reproduce the most recommended modulation schemes by using a power efficient HB-LED driver. However, since it is based on the use of pulse-width modulated dc-dc power converters, the required switching frequency is between 3 and 6 times higher than the maximum frequency of the communication signal. As a result, the approach suffers from high switching losses when the highest bandwidths are addressed. A method for reproducing the most recommended modulation schemes by modulating both the amplitude and the phase of the output voltage ripple is presented in this work. The major benefits are the high efficiency, the simplicity and the lower switching frequency required for the implementatio

Power Efficient VLC Transmitter Based on Pulse-Width Modulated DC-DC Converters and the Split of the Power

Visible Light Communication (VLC) has gained relevance during the last years. It consists in using High-Brightness LEDs (HB-LEDs) both for lighting and for transmitting information changing the light intensity rapidly. However, there are some bottlenecks that are slowing down the deployment of this technology. One of the most important problems is that the HB-LED drivers proposed for addressing high data rates in VLC achieve poor power efficiency. Since these HB-LED drivers must be able to reproduce fast current waveforms, the use of Linear Power Amplifiers (LPAs) has been adopted, which clearly damages the power efficiency of HB-LED lighting. In order to alleviate this problem, a HB-LED driver made up of two DC-DC power converters is presented in this work. One of them is responsible for performing the communication functionality by operating at high switching frequency (10 MHz), whereas the second converter fulfills the illumination functionality by ensuring a certain biasing point. The split of the power allows us to minimize the power delivered by the fast-response DC-DC power converter, which suffers from high switching losses. Thus, the overall efficiency can be maximized for each particular communication scenario and for scenarios with changing condition

Taking advantage of the sum of the light in outphasing technique for visible light communication transmitter

Visible Light Communication (VLC) takes advantage of the widespread use of the LEDs, and by modifying the driver stage, the LEDs are capable of lighting and transmitting information. One of the main drawbacks is the low power efficiency due to the modification of the LED driver stage in order to add the communication capability. Most of the research work related to VLC is towards the communication task, whereas there is a limited work about the improvement on the power efficiency. This paper proposes a high efficiency LED driver for VLC working as a transmitter based on the outphasing technique. This technique is used also in RF communications and increases the efficiency of the amplifiers. The proposed transmitter is made up of two switching-mode power amplifiers that reproduce the signals required for the outphasing technique and a DC/DC converter that biases the LEDs. The proposal exploits the light and, instead of being added electrically, the signals are added in their light form, which leads to a reduction in the complexity of the design. As experimental results, a transmitter was built of two Class E amplifiers reproducing a 16-QAM modulation, achieving a signal-generation efficiency of 78% and an overall efficiency of 92

Design of a Linear-Assisted VLC-LED Transmitter Based on Summing the Light

45th Annual Conference of the IEEE Industrial Electronics Society (IES), Lisboa, 2019A high efficiency linear-assisted Visible Light Communication (VLC) LED driver working as a transmitter is presented in this work. A linear-assisted transmitter is based on the idea of using a high efficiency but bandwidth limited circuitry which delivers most of the power and a low efficiency but fast linear amplifier (linear assistance) which corrects the distortion of the signal. The presented solution takes advantage of the light in a VLC system by summing the contribution of the linear amplifier in light instead of electrically, which leads to a electrical isolation between both stages and a reduction of the complexity comparing to the traditional approach used in Envelope Tracking (ET) and Envelope Elimination and Restoration (EER) techniques. As experimental results, the design of a linear-assisted Class E amplifier delivering a 16-PSK phase digital modulation with a 1 MHz carrier is presented. On one hand, the Class E amplifier delivers most of the power (92% of the signal power) at high efficiency (81%) and, on the other hand, the linear amplifier only delivers the error signal at lower efficiency. The efficiency of the signal circuitry is up to 75% and the efficiency of the whole system considering the signal and the LED biasing circuitry is up to 85

Effect of hypocaloric diet with a commertial formula in weight loss and quality of life in obese patients with chronic osteoarthritis

Producción CientíficaIntroducción: El objetivo de nuestro estudio fue evaluar en pacientes obesos con osteoartritis crónica el impacto sobre la calidad de vida y el control metabólico de una intervención dietética con una formula comercial hipocalórica. Material y métodos: Se evaluó una muestra de 55 pacientes obesos con osteoartritis crónica. EL estudió consistió en un programa de 12 semanas de reducción de peso en el que los paciente recibían al día dos envases de Optisource Plus®. Resultados: Se dividieron a los pacientes en dos grupos, uno que perdió menos de un 9% (grupo 1) y el grupo 2 (más de 9% de pérdida de peso). Los pacientes en el grupo 2 mostraron una mejoria en la puntuacion total del test de calidad de vida SF-36 (4,0 ± 6,1 puntos), en el campo de la función física del SF 36 (1,8 ± 3,4 puntos), el en campo del componente físico del SF 36 (0,6 ± 1,6 puntos) y en el campo de la vitalidad del SF 36 (2,7 ± 4,6 puntos). También mejoraron de manera significativa, la puntuación total del test específico de calidad de vida para osteoartritis WOMAC (-8,2 ± 15,0 puntos), el dominio funcional del test WOMAC (- 6.5+/-10.6 puntos) y el dominio de la rigidez del test WOMAC (-0,7 ± 2,1 puntos). Conclusión: El efecto sobre la calidad de vida fue superior en el grupo con porcentaje de pérdida de peso > 9% con la formula hipocalórica comercial

On supplying LEDs from very low dc voltages with high frequency AC-LED drivers

2018 IEEE 19th Workshop on Control and Modeling for Power Electronics (COMPEL), 25-28 junio, Padua (Italia)This work studies the driving of white Light Emitting Diodes (LEDs) from very low voltages in the range of 1.2 to 2 V. The proposed idea is based on replacing the standard Schottky diode used in conventional converter topologies (i.e., buck, buck-boost and boost) with an LED, while shortcutting the output of the converter. In this configuration, the LED works both as the load and as the rectifier diode of the converter, hence, switching the LED at high frequencies (i.e. > 100 kHz). Moreover, a thorough analytical study is carried out for the two topologies rendered in this work. Particularly emphasizing their static analysis and the obtaining of the boundaries between the different conduction modes. Finally, the idea is validated experimentally by means of the boost converter variation (i.e., DL//S AC-LED driver). The DL//S AC-LED driver has also been compared with a dc-dc boost converter showing a better luminous efficacy while disposing of the Schottky diode and the output capacitor. This analysis is carried out when connected to a Li-Ion battery using a simple control and integrated circuit for its developmen