Optimizing the design of single-stage power factor correctors

This paper presents a new analytical method for the generalized study of a cluster of single-stage power-factor correctors (S2PFCs). Due to this generalized approach, new topologies have been obtained, and the study of other known topologies has been simplified. The new analytical method simplifies the design of S2PFCs by making it possible to compare a large number of different designs from the same viewpoint in order to identify the best topology. Finally, this research has enabled us to reduce the total size of the additional inductors that are used by a factor of two to three with respect to previous implementations

Buck derived converters based on gallium nitride devices for Envelope Tracking applications

Envelope tracking (ET) is a technique designed to enhance the efficiency of radio frequency power amplifiers (RF PA). It is based on providing the voltage to the RF PA with variations that mimic the shape of the envelope of the communication signal that the RF PA is processing. As the bandwidth of these signals can be around several megahertz, the switching frequency of the switching mode power supply designed for ET applications has to be very high. The good switching characteristics of Gallium Nitride devices makes them suitable for this application. This paper presents two multiphase converters to be used as envelope modulators in envelope tracking application

Design considerations for single-stage, input- current shapers for low output voltage ripple

A lot of power topologies have been proposed to comply with the IEC-61000-3-2 regulations. One group of solutions involves obtaining an additional output from one of the converter’s magnetic devices. These solutions are very good due to the low harmonic content and from the low cost point of view. Nevertheless these magnetic coupled circuits can modify the converter’s performance. The abnormal operation can be observed as an output voltage ripple higher than expected. This paper deals with the design considerations for law output voltage ripple Single-Stage-Input-Current Shapers (S’ICS) and explains the abnormalities

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

A linear assisted switching envelope amplifier for a UHF polar transmitter

Spectrally efficient wireless communication standards impose stringent linearity specifications, which would require traditional IQ transmitters to operate with back-offed and power inefficient linear RF power amplifiers (PAs). In order to overcome such a significant limitation, alternative architectures have been proposed, as those based on the envelope elimination and restoration technique. An example of the application of this technique is the polar transmitter. In this paper, a UHF polar transmitter is presented, combining switching and linear stages in the envelope amplifier as to achieve both wide bandwidth and high efficiency, when drain modulating a GaN HEMT Class E RF PA. Several tests, using EDGE, TETRA, and WCDMA standards have been performed with good results.This work was supported by the Spanish Ministries MICINN and MINECO through the FEDER cofunded Project TEC2011-29126-C03-01, Consolider Project CSD2008-00068, Consolider Project RUECSD2009-00046, and Project DPI2010-21110-C02-01

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

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

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

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