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

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

A wireless power system includes a power source, power receiver, and components thereof. The system can also include a parasitic antenna that can improve the coupling to the power source in various modes. The antenna can have both a variable capacitor and a variable inductor, and both of those can be changed in order to change characteristics of the matching.

Packaging and details of a wireless power device

Computer Controlled Systems: Theory and Design

A control circuit for a switch unit of a clocked power supply receives an auxiliary signal from a resonant transformer driven by the switch unit and detects reference crossing moments when the auxiliary signal crosses a reference value. A driver is controllable to switch the switch unit, and a synchronization circuit synchronizes a turn-on of the switch unit within a predetermined time interval around a zero crossing of a voltage present across the switch unit, or of a current flowing through the switch unit. The synchronization circuit receives information about the reference crossing moments and provides a turn-on signal to the driver with a fixed phase delay at the reference crossing moments, so as to define turn-on moments at which the driver is to turn on the switch unit.

Control circuit for a switch unit of a clocked power supply circuit, and resonance converter

This paper provides a comparative analysis among four electronic ballast topologies with high power factor, employing the same switch for inverter and power factor correction stage. The analyses done are based on experimental results. A commercial electromagnetic ballast (EMB) is tested to provide a comparison with implemented electronic ballasts. The features of each topology are shown through the discussion of their advantages and disadvantages. The electronic ballasts are made for two 40-W fluorescent lamps at 50-kHz switching frequency and for a 110-V/sub rms/ 60-Hz utility line.

A practical comparison among high-power-factor electronic ballasts with similar ideas

This paper presents a simple alternative for an electronic ballast operating in self-sustained oscillating mode with dimming capability for fluorescent lamps. A simple modification in one of the gate drivers side circuit allows the lamp to dim without compromising the simplicity, reliability, and low cost which characterize the self-oscillating electronic ballast (SOEB). A qualitative analysis is presented to explain the behavior of the proposed self-oscillating electronic ballast with dimming feature. In addition, the stability and the key equations for the design are derived using the extended Nyquist criterion and describing function method. Experimental results from two 40-W electronic ballasts are presented to demonstrate the performance and to validate the analysis carried out.

Self-oscillating dimmable electronic ballast

This paper presents a design methodology and analysis of electronic ballast employing the self-oscillating-command circuit. The self-oscillating electronic ballast is represented as a relay control system in order to determine its parameters using the describing-function method and an extended Nyquist stability criterion. Simulation and experimental results of the electronic ballast supplying a 40-W fluorescent lamp are presented in order to confirm the feasibility of the performed design methodology.

A Design Methodology for a Self-Oscillating Electronic Ballast

This paper deals with the thermal characteristics of the I -V curve of GaN-based white light-emitting diodes (LEDs), focused on the variations of the dynamic resistance The final goal of this study is to improve the static and dynamic operations of the LED driver within a wide range of temperatures Four LEDs from different manufacturers were chosen for this study The first part of this paper shows the thermal characterization of the forward voltage at a given injected current After that, the experimental data are fitted in order to calculate the junction temperature accurately Then, a small-signal analysis where the LEDs are supplied with dc current and an ac perturbation superimposed at the operation point under variable junction temperature is covered This analysis allows the dynamic resistance to be experimentally determined for a wide junction temperature range Furthermore, the experimental data have been fitted in order to establish the relationship between junction temperature and dynamic-resistance variation, so the dynamic resistance can be determined for a given operation point Finally, an illustrative example is presented as a case study in order to analyze the implications of the dynamic resistance on the output-current ripple and on the closed-loop operation of a LED driver The experimental results confirm that the junction temperature shift induces a variation in the dynamic resistance, which might have a significant effect on the output-current ripple and closed-loop performance in certain LED fixtures

Fábio Ecke Bisogno

Papers

Control circuit for a switch unit of a clocked power supply circuit, and resonance converter

A practical comparison among high-power-factor electronic ballasts with similar ideas

Self-oscillating dimmable electronic ballast

A Design Methodology for a Self-Oscillating Electronic Ballast

Effects of the Junction Temperature on the Dynamic Resistance of White LEDs