Showing papers by "J.A. Cobos published in 2006"

Nonlinear digital control breaks bandwidth limitations

Abstract: The bandwidth achievable by using linear control in SMPS is limited either by the switching frequency or by the robustness of the system Fast transient response requires high switching frequency However, lower switching frequencies could be more suitable to maximize efficiency On the other hand, if high switching frequency is not a problem, high bandwidth is difficult to obtain because of noise, plant variation and non-idealities of the error amplifier This paper proposes two different approaches based on the combination of nonlinear control with linear control to break these limitations These strategies are applied for dynamic voltage scaling and two prototypes are built to validate the concepts

Behavioral modeling of dc-dc converters for large-signal simulation of distributed power systems

Abstract: System designers normally use commercial dc-dc converters to build the power system. Simulation plays an important role in the configuration, analysis and design of the system, but the lack of available models of commercial dc-dc converters is a major drawback. The aim of this work is to develop a generic model of dc-dc converters based on the information provided by manufacturers in their datasheet. The model is intended to be able to predict power consumption, efficiency, system stability and large signal behavior including inrush current, protections, start-up and remote on-off control.

Comparison of current doubler rectifier and center tapped rectifier for low voltage applications

Abstract: It is well known that the current doubler rectifier is very suitable for low voltage (1V-2V) and very high current (50A-100A) dc-dc converters. However, at lower current applications (30A, 20A, 10A), it is not clear which is the more appropriate rectifier the current doubler or the center tapped. The goal of this paper is to identify the application area of these rectifiers. The output current together the output current ripple/output current ratio (/spl Delta/I/I/sub O/) are important parameters to select the more suitable rectifier.

A low power topology derived from flyback with active clamp based on a very simple transformer

Abstract: This paper presents and analyzes a low power (10W) topology derived from flyback with active clamp based on very simple and low cost transformers. The main feature of this flyback topology is that the ratio between magnetizing inductance and the series inductance (leakage or integrated inductor) is very low (around 10/1). Operation of the topology is analyzed and several transformer configurations are considered. Performance of this topology are validated in three prototypes developed for an automotive application (V/sub IN/ =42V, V/sub OUT/ = 3.3V, I/sub OUT/ = 5A). The proposed solution achieves a promising trade-off between efficiency and cost in low power applications with medium or high input/output voltage ratio.

Behavioral modeling of multi-output DC-DC converters for large-signal simulation of distributed power systems

Abstract: Simulation can play an important role in the configuration, analysis and design of distributed power systems, but the lack of available models of the main components (batteries, fuel-cells, AC-DC and DC-DC converters) is a major drawback for its use. The aim of this work is to develop a generic model of multi-output DC-DC converters, widely used in power electronic systems, based on the information provided by manufacturers in their datasheet or measurements. The model is intended to be able to predict power consumption, efficiency, system stability and large signal behavior including cross-regulation, inrush current, protections, start-up and remote on-off control.

Experiences in education innovation: developing tools in support of active learning

Abstract: The paper focuses on educational projects developed in the ETSII (Escuela Tecnica Superior de Ingenieros Industriales) of the Polytechnic University of Madrid during the past few years. These projects were developed as new tools for enhancing the active role of students, for improving practical teaching, especially by means of virtual laboratories and different sets of problems and exercises, and for promoting self-learning. The paper analyses the use of ICT in teaching, with the case of a developed e-learning platform as a tracking system for subjects. The paper concludes by discussing the new educational trends in the Centre, devoted to develop an active role of students by activities such as peer mentoring and laboratory monitors programs, and competitions for achieving multidisciplinary engineering challenges.

Digital control for power supply of a transmitter with variable reference

Abstract: RF power amplifiers can save much energy if they are supplied with a variable voltage as described in the state of the art. The design of the power supply of these amplifiers is challenging since many requirements have to be accomplished: very low output voltage ripple; wide output voltage variation at kHz frequencies; fast load current steps; etc. A typical solution is the use of a multiphase dc-dc converter based on the buck topology. In this paper, we propose the use of digital control for these power supplies. The main advantage is that current loops are removed. The design of this control circuit and main trade-offs are discussed. The results obtained from a 240 W prototype show the advantages and the limitations of this proposal.

High-Frequency Bi-Directional DC/DC Converter Using Two Inductor Rectifier

Abstract: In recent years, many converters are being proposed to be used as bidirectional Some applications of these DC-DC converters can be battery charger-dischargers, hybrid vehicles, and DC-UPS In applications like hybrid vehicles a high voltage DC bus to supply power to the motor is usually required When the DC bus in hybrid vehicle is held by a big capacitor, the selection and design of the converter has an additional difficulty, since the converter has to work with an output voltage that ranges from 0 to 420 V in steady-state conditions In this paper, a bidirectional DC-DC converter is proposed to satisfy the hybrid vehicles requirements and can be used to work permanently with any output voltage from 0 to 420 V without any difficulty Analysis, design and experimental results of a 200 W laboratory prototype circuit are included

A new approach to obtain 1D thermal models for magnetic components including the effect of spacing between conductors

Abstract: Analytical (1D) thermal models for magnetic components are commonly used in the magnetic component design process in order to estimate the temperature in the component. Most of the analytical thermal models presented in the literature, consider small separation between different turns of the same layer. However, if that separation is high, a 1D thermal model might be inaccurate. This paper presents a new thermal model that is valid also for those cases. The model has been validated with several components and it has been compared with FEA results and measurements.