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

Reproducing single-carrier digital modulation schemes for VLC by controlling the first switching harmonic of the dc-dc power converter output voltage ripple

A DC-DC power converter based on a two-phase synchronous buck converter that reproduces single-carrier digital modulation schemes by controlling the first switching harmonic of the output voltage ripple is presented in this work. The DC-DC power converter carries out both the lighting and the transmission functionalities of Visible Light Communication (VLC) transmitters. Control of both the amplitude and the phase of sinusoidal currents injected towards High-Brightness LEDs (HB-LEDs) enables the use of efficient modulation schemes such as Quadrature Amplitude Modulation (QAM), Carrier-less Amplitude and Phase modulation (CAP), Amplitude-Shift Keying (ASK) and Phase-Shift Keying (PSK). These modulation schemes achieve higher spectral efficiency (i.e. more data can be transmitted using the same bandwidth) than previously proposed modulation schemes performed by VLC transmitters based on the use of DC-DC power converters. To the author's knowledge, the ratio between the bit rate achieved and the switching frequency of the DC-DC power converter presented in this paper is the highest that can be found in literatur

Evaluación de técnicas de control modulares en un convertidor elevador síncrono con rendimiento elevado a baja carga con el uso de MOSFET de SiC

XXIV Seminario Anual de Automática, Electrónica Industrial e Instrumentación 2017 (SAAEI'17), Valencia (España)Este artículo se centra en convertidores bidireccionales de alta tensión para ser utilizados como interfaz entre baterías y celdas de un convertidor modular multinivel (MMC), para poder dotar de almacenamiento distribuido a un transformador de estado sólido (SST). Dichos convertidores han de tener un rendimiento elevado a media y baja carga, así como un rizado de corriente reducido, debido a los procesos de carga y descarga de la batería. En este trabajo se analiza el uso de MOSFET de SiC como solución para cumplir con los dos requisitos anteriores. En primer lugar, la implementación de un control de frecuencia variable que permita mantener el rendimiento a baja carga. Y en segundo lugar, el uso de un convertidor modular y de distintas técnicas de control para reducir el rizado de corriente. En este trabajo se resumen distintos resultados experimentales del uso de MOSFET de SiC con el control de frecuencia variable, así como una comparativa de las técnicas de control. Estos resultados se han obtenido mediante un convertidor modular con entrada en paralelo y salida en paralelo (IPOP) basado en tres módulos (3kW por módulo) de un elevador síncrono, para una conversión de 400V a 800V y 9kW de potencia máxim

The voltage-controlled compensation ramp: A new waveshaping technique for power factor correctors

IEEE Applied Power Electronics Conference (APEC) (27. 2008. Austin, Texas)This paper deals with a new control method for Power Factor Correctors. Control is carried out by a standard IC controller for peak current-mode dc-dc converters, with only an additional compensation ramp generator and peak detector. Neither an analog multiplier nor an input voltage sensor is needed to achieve quasi-sinusoidal line waveforms, which makes this method very attractive. The method is similar to the one-cycle control method, but can be very easily adapted for use with topologies different to the boost converter, i.e. flyback, buck-boost, SEPIC Cuk and Zeta topologies. Moreover, as the line current is cycle-by-cycle controlled, the resulting input current feedback loop is extremely fast, thus allowing the use of this type of control with high frequency line

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

Active input current shaper without an electrolytic capacitor for retrofit lamps applications

The evolution of solid-state lighting technology has transformed traditional solutions in lighting. High-brightness light-emitting diodes (HB-LEDs) have become very attractive light sources due to their excellent characteristics, namely high efficiency, a long lifetime, and low maintenance. It is evident that HB-LED drivers must be durable and efficient in order to enjoy these advantages. Moreover, to replace incandescent bulbs, the ac-to-dc HB-LED driver must be simple and have low size and comply with international regulations (i.e., injecting low-frequency harmonics into the mains supply). With the last modifications regarding low-power lighting equipment (i.e., < 25 W), the authors have traditionally focused their efforts on increasing efficiency by sacrificing sinusoidal input current, yet all their solutions obviate the suppression of the traditional electrolytic capacitor of ac-to-dc converters, highlighting that this is the price to pay for a simple and low-size solution. This paper, however, puts forward the design of a simple and low-size ac-to-dc HB-LED driver for retrofit lamps without an electrolytic capacitor in order to extend its lifetime. The solution proposed here derives from a well-known technique used in the past, the active input current shaper (AICS), but without an electrolytic capacitor in this case. If the electrolytic capacitor of an AICS is removed, then low-frequency ripple arises at its intermediate dc bus, adding some distortion in the line input current over the proper natural one of an AICS. However, this addition is slight in comparison to the proper natural distortion of AICSs. Moreover, the low-frequency ripple at the intermediate bus is not transferred to the output with the help of the rapid output dynamic response of the AICS, which prevents flicker. This paper presents a theoretical analysis that guarantees a compromise between compliance with international regulations and the use of capacitor technologies other than the electrolytic design. Finally, a 24-W experimental prototype has been built and tested to validate the theoretical results presented in this paper.This work was supported by the Spanish Ministry of Education and Science under Project MINECO-13-DPI2013-47176-C2-2-R, by the Government of the Principality of Asturias under Project FC-15-GRUPIN14-143, and by European Regional Development Fund grants

High-efficiency LED driver without electrolytic capacitor for street lighting

High-Brightness Light Emitting Diodes (HB-LEDs) are considered as a remarkable lighting device due to their high reliability, chromatic variety and increasing efficiency. As a consequence, a high number of solutions for supplying LED strings are coming out. One-stage solutions are cost-effective, but their efficiency is low as they have to fulfill several purposes with only one converter: Power Factor Correction (PFC), galvanic isolation (in some cases) and current regulation. Two-stage and three-stage solutions have higher efficiency as each stage is optimized for just one or two tasks and they are the preferred option when supplying several strings at the same time. Nevertheless, due to their higher cost in comparison to one-stage solutions, they are used when high-efficiency, high-performance and the possibility of supplying several strings are the main concerns. Besides, they are also used when high reliability is needed and electrolytic capacitors cannot be used. In this paper, a three-stage solution and its complete design guideline for LED-based applications is proposed. PFC is achieved by a Boost converter while the galvanic isolation is provided by an Electronic Transformer (second stage). The third stages (one for each LED string) are designed following the TIBuck schematic, but taking advantage of the load characteristics (i.e., the high value of the LED string knee voltage, approximately equal to half the string nominal voltage). Besides, a variation of the analog driving technique is also proposed. Experimental results obtained with a 160-W prototype show an efficiency as high as 93% for the whole topology and 95% for the cascade connection of the second and third stage