A multiwinding modeling method for high frequency transformers and inductors

This paper presents a method to obtain an electric model for transformers and inductors, including both frequency and geometry effects in the windings, which can be linked with existing core models. One-dimensional distributions for magnetic and electric fields are assumed, and from Maxwell's equations an equivalent electric circuit is easily obtained. This equivalent circuit has been included in analog simulators (Spice, AnalogWorkBench, Saber ...), and comparisons between measured and simulated results are shown, both in time domain and in AC sweep, which verify the model accuracy. The model described in this paper allows designers to deal with key issues in the design of high-frequency magnetic components (copper losses, leakage inductance, skin and proximity effects) by using analog simulators, which are usually more familiar to them than finite-element analysis tools.     

Thick-film hybrid technology for low-output-voltage DC/DC converter

The new requirements in portable and telecommunication equipment also affect the supply systems. The current tendency to lower the output voltage (3.3, 2.7 V/sub DC/) together with the necessity of an important size reduction is modifying the strategies for dc/dc converter implementation. Low-voltage high-power-density applications present two important factors that must be analyzed: thermal problems due to high power density, and the high currents to be handled. This paper presents a 10-W dc/dc buck converter with passive integration using hybrid technology (within the frame of ESPRIT Project 23910.). As a result of the mentioned integration technique, a power density of 6.25 W/cm/sup 3/ was obtained with high efficiency (approximately 90%).     

Zinc coating control on steel wires

Galvanic steel wire manufacturers have to fulfill several international regulations regarding zinc mass by surface unit. This article presents a new sensor to measure this parameter online. Details about the different parts of the system (sensor, circuitry, adjustment, and signal processing) are explained. Experimental results in a real manufacturing line are also presented. Online measurement conserves zinc mass and guarantees savings     

Trade openness and regional development in a developing country

This paper examines how economic openness influences regional development in a developing country, with the Philippines as a case study. It first looks at the disparities in economic and social indicators across the country's 14 regions and over time. Metro Manila continues to tower over the national economic landscape, although economic dispersal especially in adjacent regions appears to be expanding. The paper then analyzes the determinants of regional development, using five-year panel data. Trade openness appears to be beneficial to regional economic growth and, via growth, poverty reduction. However, it cannot by itself be expected to bring about more balanced regional development. The authors thank Emma Fan, Jesus Felipe, Rana Hasan, and participants in the conference on the Impacts of Globalization on Urban Development, Bellagio, Lake Como, Italy, 19–23 August 2002, for their helpful comments.     

A Monolithic and Self-Referenced RF LC Clock Generator Compliant With USB 2.0

A monolithic and self-referenced radio frequency (RF) LC clock generator that is compliant with USB 2.0 is demonstrated in a system-on-chip (SoC). This work presents the first successful approach to replacing an external crystal (XTAL), the crystal oscillator (XO) and the phase-locked loop for clock generation in an IC supporting USB 2.0 using a standard CMOS fabrication process. It is shown that the primary design challenges with the implemented approach involve maintaining high frequency accuracy and low jitter. Techniques for addressing both are shown. In particular, the presented architecture exploits the effects of frequency division and low far-from-carrier phase noise to achieve low jitter. From a 1.536 GHz temperature-compensated LC reference oscillator, coherent clock signals are derived at 96MHz for the SoC logic and 12 MHz for an on-chip full-speed USB PHY. Though self-referenced, approximately plusmn400ppm total frequency accuracy is achieved over process variations, plusmn10% variation in the USB power supply voltage and temperature variation from -10 to +85degC. Measured period and cycle-to-cycle jitter are 6.78 ps_rms and 8.96 ps_rms, respectively. Fabricated in a 0.35 mum CMOS technology, the clock generator occupies 0.22 mm² and draws 9.5 mA from a 3.3-V supply, which is derived from the 5-V USB power supply     

Analysis and design of a new constant frequency control for QRC andMRC based on magnetic elements modification

Multiresonant power converters (MRCs) and quasi-resonant power converters (QRCs) have been modified to provide constant-frequency operation. Transformer leakage inductance has been used to adapt the traditional pulse-width-modulation (PWM) control to these converters. Conventional PWM integrated circuits can be used for the power converter regulation. Several experimental results are developed to test the control method proposed     

Magnetic nanocarriers with tunable pH dependence for controlled loading and release of cationic and anionic payloads

Superparamagnetic nanocarriers with tunable pH dependence of the surface charge are designed by a simple co-precipitation method. By exploiting electrostatic interactions, cationic or anionic payloads can be adsorbed and desorbed depending on the pH. On three different resulting nanocarrier systems, experiments of loading and release of gold nanoparticles as well as effective siRNA loading and in vitro delivery on human cells are performed.     

Intelligent and universal fast charger for Ni-Cd and Ni-MH batteries in portable applications

In this paper, a new fast charger is presented for Ni-Cd and Ni-MH batteries, which are the most frequently used in portable applications. In this charger, the control and supervision of the process has been entrusted to a microcontroller, which provides a powerful and intelligent tool to undertake complex tasks, and reduces the requested circuitry to the microcontroller itself and a few additional components. The resulting charger is able to work out the initial battery state (detecting deteriorated devices), decide the suitable way to charge it (ensuring a long cyclic life), and determine when the charge process must be finished. This way, the state of the battery is always controlled, preventing any damage to it and providing a fully protected operation mode. This paper summarizes the design and construction of the presented charger, as well as shows the experimental results obtained in the prototype tests.     

Design of integrated magnetic elements using thick-film technology

One of the most important aims in the electronic industry is the integration of magnetic elements, since it allows the reduction of the size of power electronics equipment. This paper presents a method of designing integrated magnetic elements using thick-film technology. A DC-to-DC converter has been built and tested to validate this technology. Experimental results obtained and conclusions are also presented