There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

This International Myeloma Working Group consensus updates the disease defi nition of multiple myeloma to include validated biomarkers in addition to existing requirements of attributable CRAB features (hypercalcaemia, renal failure, anaemia, and bone lesions). These changes are based on the identifi cation of biomarkers associated with near inevitable development of CRAB features in patients who would otherwise be regarded as having smouldering multiple myeloma. A delay in application of the label of multiple myeloma and postponement of therapy could be detrimental to these patients. In addition to this change, we clarify and update the underlying laboratory and radiographic variables that fulfi l the criteria for the presence of myeloma-defi ning CRAB features, and the histological and monoclonal protein requirements for the disease diagnosis. Finally, we provide specifi c metrics that new biomarkers should meet for inclusion in the disease defi nition. The International Myeloma Working Group recommends the implementation of these criteria in routine practice and in future clinical trials, and recommends that future studies analyse any diff erences in outcome that might occur as a result of the new disease defi nition.

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International Myeloma Working Group updated criteria for the diagnosis of multiple myeloma.

Solid-state switch-mode rectification converters have reached a matured level for improving power quality in terms of power-factor correction (PFC), reduced total harmonic distortion at input AC mains and precisely regulated DC output in buck, boost, buck-boost and multilevel modes with unidirectional and bidirectional power flow. This paper deals with a comprehensive review of improved power quality converters (IPQCs) configurations, control approaches, design features, selection of components, other related considerations, and their suitability and selection for specific applications. It is targeted to provide a wide spectrum on the status of IPQC technology to researchers, designers and application engineers working on switched-mode AC-DC converters. A classified list of more than 450 research publications on the state of art of IPQC is also given for a quick reference.

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A review of single-phase improved power quality AC-DC converters

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

Solid-state switch mode AC-DC converters having high-frequency transformer isolation are developed in buck, boost, and buck-boost configurations with improved power quality in terms of reduced total harmonic distortion (THD) of input current, power-factor correction (PFC) at AC mains and precisely regulated and isolated DC output voltage feeding to loads from few Watts to several kW. This paper presents a comprehensive study on state of art of power factor corrected single-phase AC-DC converters configurations, control strategies, selection of components and design considerations, performance evaluation, power quality considerations, selection criteria and potential applications, latest trends, and future developments. Simulation results as well as comparative performance are presented and discussed for most of the proposed topologies.

Comprehensive Study of Single-Phase AC-DC Power Factor Corrected Converters With High-Frequency Isolation

A solution to operate DC-DC resonant converters at constant frequency is proposed. A variable inductor is used to achieve output voltage control and regulation without changing the switching frequency of the converter. The output voltage characteristic of the parallel resonant converter operating under this so-called magnetic control is briefly analysed. A 48 V input, 5 V output, 500 kHz, 25 W prototype is presented to prove the feasibility of the proposed control method.

Magnetic control of DC-DC resonant converters provides constant frequency operation

This paper presents the study of an offline flyback-based light-emitting diode (LED) driver with reduced storage capacitance. An approach called active ripple compensation was used for minimizing the converter bulk capacitance. This technique is oriented to voltage-controlled pulse width modulation converters and is based on the modulation of the duty cycle, which allows for the reduction of the filtering capacitance by increasing the harmonic content of the input current up to the limits established by the standards. By means of the design procedure presented in this paper, the amount of capacitance reduction and input current distortion can be fully controlled and theoretically predicted. In addition, no extra sensors are required to implement the proposed technique, apart from the LED current sensor already available in most LED drivers. Experimental results from a 50-W laboratory prototype supplied from a 220-V 60-Hz grid were carried out. The results were compared with the conventional approach, attesting the superior performance of the proposed methodology.

Investigation of the Active Ripple Compensation Technique to Reduce Bulk Capacitance in Offline Flyback-Based LED Drivers

This paper presents some design issues and experimental results regarding the use of the input current shaper (ICS) technique to implement high power factor electronic ballasts. The ICS is placed between main rectifier and bulk capacitor to increase the conduction angle of the main rectifier diodes up to a minimum value to obtain low current harmonics injected to the mains. Two possibilities to implement ICS-based ballast are considered in this paper: the forward-based ICS and the flyback-based ICS. Experimental results obtained from two 40-W fluorescent lamp ballasts are also presented.

Design and experimental results of an input-current-shaper based electronic ballast

In this article, a novel high-power-factor electrolytic-capacitorless light-emitting diode (LED) driver based on the use of a ripple port is presented. The ripple port consists of adding an extra power processing circuit at the output of the converter that injects energy to compensate for the output current and voltage ripples. In this work, the main converter is built by using a flyback converter operating in the discontinuous conduction mode (DCM). The ripple port is implemented by adding an extra winding to the flyback coupled inductors, together with an extra switch, a capacitor, and an inductor. The additional switch is used to inject energy to the output in the time intervals, in which the flyback output current is low, thus reducing the output current ripple. The proposed converter is analyzed in detail, and a design methodology is proposed. A design example for a 27-V/1-A LED lamp is presented. Simulation and laboratory experiments have also been carried out. It is demonstrated that the proposed solution can achieve a reduction on the output current ripple of around 65% compared to the solution without ripple port for the same total capacitance and maintain a high power factor of 0.994.

A Novel High-Power-Factor Electrolytic-Capacitorless LED Driver Based on Ripple Port

Based on the respective merits of the LLC resonant converter and the VI (Variable Inductor), a new battery charger topology is proposed. This paper presents a design methodology for the LLC resonant converter controlled with a VI. The output of the converter is regulated through a variable resonant tank in order to control the charging process. A small-scale prototype fed by a 50V DC input, with an IGBT based inverter working at 11.3 kHz was built in order to test the proposed control method. Experimental results are presented.

J.M. Alonso

Papers

Magnetic control of DC-DC resonant converters provides constant frequency operation

Investigation of the Active Ripple Compensation Technique to Reduce Bulk Capacitance in Offline Flyback-Based LED Drivers

Design and experimental results of an input-current-shaper based electronic ballast

A Novel High-Power-Factor Electrolytic-Capacitorless LED Driver Based on Ripple Port

Evaluation of a variable-inductor-controlled LLC resonant converter for battery charging applications