Light-Emitting Diodes. (Monographs in Electrical and Electronic Engineering.) By A. A. Bergh and P. J. Dean. Pp. viii+591. (Clarendon: Oxford; Oxford University: London, 1976.) £22.

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Light-emitting diodes

This article reviews the design and evaluation of different DC-DC converter topologies for Battery Electric Vehicles (BEVs) and Plug-in Hybrid Electric Vehicles (PHEVs). The design and evaluation of these converter topologies are presented, analyzed and compared in terms of output power, component count, switching frequency, electromagnetic interference (EMI), losses, effectiveness, reliability and cost. This paper also evaluates the architecture, merits and demerits of converter topologies (AC-DC and DC-DC) for Fast Charging Stations (FCHARs). On the basis of this analysis, it has found that the Multidevice Interleaved DC-DC Bidirectional Converter (MDIBC) is the most suitable topology for high-power BEVs and PHEVs (> 10kW), thanks to its low input current ripples, low output voltage ripples, low electromagnetic interference, bidirectionality, high efficiency and high reliability. In contrast, for low-power electric vehicles (<10 kW), it is tough to recommend a single candidate that is the best in all possible aspects. However, the Sinusoidal Amplitude Converter, the Z-Source DC-DC converter and the boost DC-DC converter with resonant circuit are more suitable for low-power BEVs and PHEVs because of their soft switching, noise-free operation, low switching loss and high efficiency. Finally, this paper explores the opportunity of using wide band gap semiconductors (WBGSs) in DC-DC converters for BEVs, PHEVs and converters for FCHARs. Specifically, the future roadmap of research for WBGSs, modeling of emerging topologies and design techniques of the control system for BEV and PHEV powertrains are also presented in detail, which will certainly help researchers and solution engineers of automotive industries to select the suitable converter topology to achieve the growth of projected power density.

DC-DC Converter Topologies for Electric Vehicles, Plug-in Hybrid Electric Vehicles and Fast Charging Stations: State of the Art and Future Trends

Light-emitting diode (LEDs) have a promising prospect because of its outstanding advantages: 1) long lifetime, 2) environmentally friendly, 3) flexibility of color mixing, 4) high illumination efficiency, etc. Based on the electrical characteristics of LEDs, a constant current driver is needed to support the LED working performance. With the wide applications of LEDs, many new technologies are presented. In this paper, advantages and disadvantages of different LED drivers are discussed. A detailed technology review is presented which is good for researchers and engineers to make right choices in design and selection of LED drivers.

A Review of LED Drivers and Related Technologies

This paper proposes an automatic any-cells-to-any-cells battery equalizer, which merges the forward and flyback converters through a common multiwinding transformer. The windings of the transformer are divided into two groups, which have opposite polarities. The principles of the proposed equalizer are that the equalization in one group is achieved based on forward conversion and the balancing between the two different groups is based on flyback conversion, by which the magnetic energy stored in the transformer can be automatically reset without using additional demagnetizing circuits. Moreover, only one MOSFET and one primary winding are required for each cell, resulting in smaller size and lower cost. One pair of complementary control signals is employed for all MOSFETs, and energy can be automatically and directly delivered from any high-voltage cells to any low-voltage cells without the requirement of cell monitoring circuits, thereby leading to a high balancing efficiency and speed. The proposed topology can achieve the global equalization for a long battery string through connecting the secondary sides of transformers without the need of additional components for the equalization among modules, which also overcomes the mismatching problem of multiple windings. The validity of the proposed equalizer is verified through experiments, and the balancing efficiency can reach up to 89.4% over a wide range of conditions.

An Automatic Equalizer Based on Forward–Flyback Converter for Series-Connected Battery Strings

A review of DC/DC converter-based electrochemical impedance spectroscopy for fuel cell electric vehicles

This paper proposes an interleaved buck converter (IBC) with continuous input current, extremely low output current ripple, low switching losses, and improved step-down conversion ratio Unlike the conventional IBC, the proposed converter has a continuous input current, and its output current ripple is extremely low The proposed converter has a lower voltage stress in comparison to the conventional IBC and can also provide a high step-down ratio, which makes it a proper choice for high-power applications where a nonisolated step-down converter with low output current ripple and continuous input current is required Also, the proposed converter can provide current sharing between two interleaved modules without using additional current-sharing control method All of these benefits are obtained without any additional stress on the circuit components A prototype converter with 200-V input and 24-V–10-A output is implemented to verify the theoretical analysis Operational principles and experimental results are presented in this paper

Interleaved Buck Converter With Continuous Input Current, Extremely Low Output Current Ripple, Low Switching Losses, and Improved Step-Down Conversion Ratio

This paper proposes a new isolated single-stage single-switch power-factor-correction (S4 PFC) driver for supplying light-emitting diodes (LEDs) without electrolytic capacitor. In the proposed LED driver, the switch turns on under zero current switching (ZCS) condition. Also, it turns on at a voltage less than its nominal voltage stress, and therefore, the switch capacitive turn-on loss decreases too much extent. The leakage energy is absorbed, so there are no voltage spikes across the switch when the switch turns off. In this paper, operating principles of the proposed driver are discussed, and design considerations are presented. Also, a laboratory prototype for supplying a 21 W/30 V LED module from 220 ${\rm V}_{\rm rms}/50\,{\rm Hz}$ ac mains is implemented, and experimental results are presented to verify the theoretical analysis.

Analysis of the Integrated SEPIC-Flyback Converter as a Single-Stage Single-Switch Power-Factor-Correction LED Driver

In this paper, a novel grid-connected high step-up inverter is proposed. The topology is composed of two stages. The first stage is a single-switch high step-up dc–dc converter with bipolar outputs, and the second stage is a conventional half-bridge dc–ac grid-connected inverter. Negative grounding of the photovoltaic (PV) module has resulted in elimination of unwanted ground leakage currents in the PV system. Simple structure, employing few semiconductor switches, simple control, and high efficiency are the features of the proposed topology. Theoretical analysis and principal operation of the circuit are discussed. An experimental prototype is implemented to verify the performance of the proposed inverter. The experimental results confirm the aforementioned features and the theoretical analysis of the converter operation.

High Step-Up DC–AC Inverter Suitable for AC Module Applications

Z-source converter has several advantages such as high-voltage gain, clamped switch voltage and positive output voltage polarity. This study presents a new non-isolated high step-up DC–DC converter which is derived from Z-source converter and provides higher-voltage gain compared with its conventional counterpart. Owing to its high-voltage conversion ratio, the proposed converter is a proper choice for photovoltaic applications. Furthermore, reverse-recovery problems caused by the output diode are reduced in the proposed converter which reduces the switching losses. In addition, the leakage energy is recycled so the conversion efficiency is improved. Analysis and operating principles of the proposed converter are discussed and design guidelines are presented. Moreover, the effect of non-ideal elements on the proposed converter performance is analysed. A 100 W laboratory prototype to convert 20–300 V is implemented and experimental results are presented to verify theoretical analysis.

https://ietresearch.onlinelibrary.wiley.com/doi/pdf/10.1049/iet-pel.2014.0200

High step-up Z-source DC–DC converter with coupled inductors and switched capacitor cell

To enhance the gain of conventional boost converters in applications such as fuel cells and photovoltaic systems, cascade boost converters are normally applied. In this study, a new cascade boost converter topology with reduced conduction losses is proposed. This converter shows reduced root-mean-square currents of the circuit elements and reduced conduction losses. The proposed converter is analysed and compared with the conventional circuit topology. The proposed converter has all the advantages of cascade boost converter with the advantage of reduced conduction losses. Finally, simulation and experimental results of a 200 W laboratory prototype are presented.

https://ietresearch.onlinelibrary.wiley.com/doi/pdf/10.1049/iet-pel.2015.0240

Behzad Poorali

Papers

Interleaved Buck Converter With Continuous Input Current, Extremely Low Output Current Ripple, Low Switching Losses, and Improved Step-Down Conversion Ratio

Analysis of the Integrated SEPIC-Flyback Converter as a Single-Stage Single-Switch Power-Factor-Correction LED Driver

High Step-Up DC–AC Inverter Suitable for AC Module Applications

High step-up Z-source DC–DC converter with coupled inductors and switched capacitor cell

New cascade boost converter with reduced losses