J.M. Lopera

Dynamic and Steady-State Models for the PRC-LCC Resonant Topology With a Capacitor as Output Filter

In high-voltage DC power supplies (hundreds of kilovolts), avoiding the inductance in the output filter is an important asset. Thus, a capacitor as a unique component of that filter is preferable. On the other hand, a high-voltage step-up transformer shows a high capacitance in its secondary, which can be included in a resonant stage. Both capacitances, i.e., one from the filter and the other from the transformer, are separated by the output rectifier. When this rectifier is on, they are in parallel; when it is off, they are disconnected. A resonant stage where a very large capacitor appears and disappears several times in one period is not linear and has not been dynamically modeled before. This paper shows two simple models for the parallel-series (LCC-type parallel resonant converter) resonant topology with a capacitor as output filter. Its dynamics and steady state are studied and constitute an important help for any designer.

Design and analysis of thick-film integrated inductors for power converters

This paper describes the design procedures followed to obtain a thick-film inductor for its application in DC/DC power microconverters. The main characteristics of the new technology used are commented upon and design equations are given. Results are compared to those obtained by means of finite-element analysis tools. Details of some thick-film inductors developed with this technique (within the framework of the IMPASS Esprit Project (number 23910), financed by the European Community) are also given. The inclusion of one of these inductors in a 5-to-3.3-V DC/DC converter contributes to obtaining a very high power density: 6.25 W/cm/sup 3/.

A new control strategy for an AC/DC converter based on a piezoelectric transformer

Piezoelectric transformers (PTs) are an attractive solution to reduce size and weight in ac/dc converters. In this paper, a PT-based topology is presented together with a control method. As an application, an 8-W ac/dc adapter (110 V/sub AC/ input, 12 V/sub DC/ output) is presented operating at frequencies around 500 kHz.

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 Maxwells 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.

Influence of transformer parasitics in low-power applications

High-frequency operation of power converters has made it clear that the parasitic components associated with power transformers have an important influence on the behavior of the converter. Leakage inductance is often considered to be the most important parameter to take into account when designing a transformer. However, when dealing with low-power applications, self-capacitance and mutual capacitance values may play a much more important role. A proper understanding of the influence of these parasitic components and a method that allows determination of their values will help designers optimize their power converters.

Series Igniters Effects in Metal Halide Lamps Operation With High Frequency Ballasts: Study and Minimization

The use of high frequency (HF) square waveforms is a possible metal halide (MH) lamps supply method which can be implemented by means of non-resonant electronic inverters. This strategy can successfully avoid acoustic resonances appearance in such kind of lamps (theoretically, in a perfect square waveform, no power modulation is found). The main drawbacks of this kind of inverters are the electromagnetic interference emissions and the parasitic effects of the series igniters. This effect can spoil the square waveforms on the lamp, hence injecting HF harmonics in the lamp supply power spectrum, eventually leading to acoustic resonances appearance. In this paper, this effect is studied, in order to limit the values of the parasitic elements of the series igniter compatible with a proper operation of the HF inverter. Once these values are estimated, such an igniter has been built and tested, thus obtaining a practical HF (100 kHz) square waveform inverter with series igniter for 35-W MH lamps

High power density DC/DC converter using thick-film hybrid technology

The tendency to push down supply voltages (3.3 V, 2.7 V...) in telecommunication equipment makes DC/DC conversion systems be placed as close as possible to the load, thus minimizing losses due to high currents. Size is a critical feature in these supply systems, with passive components usually being the bulkiest elements. A 10 watt DC/DC converter is presented in this paper where passive components have been integrated using hybrid technology, thus allowing to obtain high power density of 6.25 W/cm/sup 3/.

A quick way to determine the optimum layer size and their disposition in magnetic structures

Designers of high-frequency magnetic elements (transformers) in switch mode power supplies (SMPS) lack of appropriate methods to select the optimum winding strategy and conductor size. This paper presents an approximate method to carry out this selection in a quick and easy way. The way to use it and the results obtained are also included.

Characteristics and design of a current sensor using multilayer Co/Ni structures

Recent studies show the possibility of using amorphous materials as current sensors. In this paper, the magnetoresistance effect existing in multilayer (Co/sub 50/Ni/sub 25/)/sub 10/ structures has been used to develop a current sensor susceptible to be fully integrated. Experimental results have been obtained to compare the properties of the anisotropic magnetoresistance effect (AMR) with commercial ones.

Analysis and design of a new constant frequency control for QRC and MRC 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.