Showing papers by "J.M. Alonso published in 2019"

A Dimmable Offline LED Driver With OOK-M-FSK Modulation for VLC Applications

Abstract: This paper proposes a visible light communication (VLC) system consisting of a single-stage buck–boost power factor correction converter operating in the discontinuous conduction mode with dimming capability. Additionally, this paper proposes the on – off M-frequency shift keying modulation for the VLC system. This modulation allows for the transmission of more than a single bit for each switching period without affecting the dimming characteristics of the light-emitting diode luminaire. The design of the whole system is discussed in detail, including both transmitter and receiver modules. A 20-W laboratory prototype was built in order to verify the proposed modulation scheme. The experimental evaluation showed a good performance of the transmitter, which was able to perform simultaneously the desired functions, namely power factor correction, dimming, and data transmission. The receiver also achieved the desired performance with a low bit error rate (BER). The results showed that the proposed system was able to transfer data between emitter and receiver with a bit rate of 1.11 Mb/s at a frequency of up to 375 kHz over a distance of 10 m, and with a BER lower than $10^{-3}$ under the influence of external lighting sources with illuminance levels up to 500 lx.

Analysis, design, and experimentation of the active hybrid-series-parallel PWM dimming scheme for high-efficient off-line LED drivers

Abstract: This study presents a high power factor (PF) light-emitting diode (LED) driver featuring a pulse width modulation (PWM) dimming technique. The integrated buck-flyback-buck converter (IBFBC) is built by connecting a buck converter to the integrated buck-flyback converter's output. The IBFBC ensures a constant output current regulation as well as high PF at all dimming ratios. The purpose of the output buck converter is to clear up the discontinuous power operation created by the PWM dimming. This occurs when the buck converter absorbs the output power, at LED switched-off, and sends it back to the input. Thus, the IBFBC maintains the operational enhancement shown by the hybrid-series-parallel (HSP)-PWM technique, ensuring greater efficiency. This study explains the operating principles of the IBFBC using circuit diagrams as well as an average model for the entire converter. Moreover, the study presents a mathematical analysis of the IBFBC power flow. It provides guidance on how to select the optimum value for the output buck inductance. A 230V, 50Hz input, 160V output, 100W AC-DC converter operating at 100 kHz has been implemented. The prototype is fully tested to demonstrate the active HSP-PWM technique. An efficiency ranging 50-86% corresponding to the dimming ratio of 5-100% is reached, where 5% dimming refers to an output power of 4W.

Analysis and behavioural modelling of matching networks for resonant-operating capacitive wireless power transfer

Abstract: This study introduces a two-port network-based behavioural modelling approach for resonant-operated capacitive wireless power transfer (WPT) systems. A simple, generic and unified modelling approach is developed to describe the behaviour of WPT systems, under changes of the source and load circuits, variations of the coupling interface and drifts of the components in the matching networks. The resultant model provides insights into the electrical cross-coupling relationships between input and output parameters of the capacitive power transfer systems, including the effect of distance and alignment of the coupling plates. Regardless of the circuit complexity, it is demonstrated that the model core can be reduced to a basic gyrator relationship with added coefficients when required, thus obtaining a compact, closed-form relationship between the input and output. To provide a simulation framework for capacitive medium variations, a simulation-compatible model of the capacitive coupling using a continuous-time variable capacitor has been constructed. The behavioural model and methodology have been validated through simulations and experiments. A 200 W experimental capacitive WPT prototype has been designed and examined for various air-gaps up to 100 mm at a resonant operation of 1.56 MHz. A very good agreement is obtained between the theoretical predictions, simulations, and experimental results.

Review of LED drivers for Visible Light Communication

Abstract: Visible Light Communication (VLC) shows up as a trend for short range wireless networks, which comes as a promising breakthrough for industry. However, this technology still faces challenges on the technical side. In particular, the selection of the appropriate circuit driver to fulfill simultaneously both lighting and communication functions is a non-trivial task. This paper reviews driver solutions intended for VLC applications, summarizing published research according to a proposed classification. Additionally, switched mode circuits stand out among the current works, supporting low data rates with higher overall efficiency at greater power levels. On the other hand, linear power amplifiers are the preferred choice for high data rate systems.

Analysis, design and evaluation of a zero-voltage-switching non-resonant converter for IPT applications

Abstract: This study presents the analysis, design and evaluation of a non-resonant converter for inductive power transfer (IPT) applications that provides zero-voltage-switching operation. The thesis of this work is that in many low-cost applications, compensation circuits used to provide resonant operation in IPT systems can be avoided, greatly simplifying the circuit and providing suitable operation and good efficiency. For this, available tools are a correct design of the converter in terms of switching frequency and output rectifier stage in order to achieve the required input–output characteristics. In order to achieve these goals, a thorough analysis of the non-resonant IPT conversion system is carried out in this study, providing the required tools for a proper study and design of the system. Experimental results from a commercial IPT transmitter/receiver arrangement are provided in order to verify the theoretical study.