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

Analysis and design of a single-stage electronic ballast with unity power factor are presented in this paper The proposed single-state ballast is the integration of a boost converter in DCM and a LCC resonant inverter The boost semi-stage working in discontinuous conduction mode functions as a power factor corrector and the inverter semi-stage operated above resonance is employed in the lamp ballast The fundamental approximation is used to design the inverter at steady-state The proposed lamp ballast can save a controller, reduce size and possibly increase system reliability over a conventional two-stage system

Analysis and design of an AC/AC resonant converter as a high pressure sodium lamp ballast

This paper presents the analysis, design and experimentation of a closed-loop metal halide lamp ballast, which supplies the lamp with a low-frequency square waveform. First of all, a discussion related to the lamp parameter that should be regulated (power or current) is presented, since this issue has not been well addressed in previous literature. Experiments demonstrated that lamp current can be chosen to be kept constant during lamp life, because, on one hand, it can attenuate the effect of lumen depreciation with lamp ageing, and, on the other hand, the lamp power does not reach over-rated values during lamp life. In order to analyze the open-loop characteristic and design a suitable controller for the closed-loop operation, a dynamic model of the lamp-ballast system is developed,. Therefore, considering the dynamic of the lamp current sensor, a PI controller is proposed to minimize the steady state error and provide a phase margin of about 80° (fully stable system). Experimental results using a flyback-based ballast supplied from a non-regulated DC voltage source (100 ? 150V) are presented to validate the theoretical analysis. It is demonstrated that the lamp current is kept constant at rated value (0.42A) within the whole input voltage range. The time response of the complete closed-loop system is about 5 ms.

Analysis, Design and Experimentation of a Closed-Loop Metal Halide Lamp Electronic Ballast

Discharge lamps present a negative dynamic characteristic that makes necessary to use a current limiting element. In high-frequency resonant ballasts, current limitation is performed by the output resonant tank; but in low-frequency square-wave electronic ballasts, arc stabilization is accomplished by the stage feeding the square wave inverter. Therefore, the design of the input converter must be made taking into account the lamp dynamic characteristic. In the present paper, a new procedure to obtain the small-signal dynamic characteristic of metal halide lamps is proposed. Using the proposed methodology, the small-signal characteristic of a 70-W lamp is obtained. This characteristic is then used for the design of an electronic ballast based on a buck-boost converter followed by a full bridge inverter. The limits for stable operation obtained are verified using a laboratory prototype.

Arc Dynamic Stabilization in Low-Frequency Square-Wave Electronic Ballast for Metal Halide Lamps

The clamped mode LCC-PS resonant inverter working with resonant current control is analysed. With this control method, the inverter is forced to operate with optimum commutations and without handling reactive energy, minimising both switching and conduction losses. A design abacus is generated and a graphic design method based on that abacus is presented and illustrated with a design example.

Analysis and design of the LCC-parallel series inverter with resonant current control as HPS lamp ballast

New advances on magnetically-controlled electronic ballasts can grant the ability to dim the lamp and simultaneously guarantee output electrical isolation. By means of a variable transformer, the model of which is presented, this new technique is developed and experimentally verified. In addition, a simple method for the large signal characterisation of the transformer is described. An FH 14W/840 Osram lamp was chosen to validate this new technique and experimental results clearly show its adequate behaviour.

J.M. Alonso

Papers

Analysis and design of an AC/AC resonant converter as a high pressure sodium lamp ballast

Analysis, Design and Experimentation of a Closed-Loop Metal Halide Lamp Electronic Ballast

Arc Dynamic Stabilization in Low-Frequency Square-Wave Electronic Ballast for Metal Halide Lamps

Analysis and design of the LCC-parallel series inverter with resonant current control as HPS lamp ballast

Magnetically-controlled dimming technique with isolated output