Showing papers by "J.A. Cobos published in 2005"

Bi-directional DC/DC Converter for Hybrid Vehicles

Abstract: Hybrid vehicles need a high voltage DC bus to supply power to the motor. Architectures of these vehicles usually include a DC-DC bi-directional converter between this voltage bus and the conventional battery. When the DC bus is held by a big capacitor, the selection and design of the aforementioned converter has an additional difficulty since the converter has to work with an output voltage ranging from 0 to 420 V in steady-state conditions. A bi-directional DC-DC converter for a hybrid vehicle is proposed in this paper. It can be used in the case that a big capacitor holds the voltage in the high side. The application forces three different operation modes being the converter able to operate in those conditions. Experimental results of a 1500 W prototype are included in the paper

Tight magnetic coupling in multiphase interleaved converters based on simple transformers

Abstract: Magnetic integration and magnetic coupling are very promising concepts to be applied in multiphase converters. Tight magnetic coupling allows energy transfer among phases. Ideally the magnetic component can act as a voltage source, with very low output impedance and with a perfect sharing of output current ripple. The main advantages provided by magnetic coupling are size and losses reduction and dynamic improvement. In this paper two winding transformer arrangements to be used in multiphase converters are presented, and validated with a new integrated transformer.

Design methodology for dynamic voltage scaling in the buck converter

Abstract: Dynamic voltage scaling is a technique that reduces the energy consumption in electronics systems. This paper deals with the design of the buck converter to meet dynamic voltage specifications and regulation under load current steps. A design methodology is proposed. Filter designs, number of interleaved phases, optimum switching frequency and control speed are key parameters that are taken into account in this methodology. The minimum time control law enables the maximum inductance design at the optimum switching frequency, thus, maximizing the efficiency of the converter. This methodology is applied to a particular specification for dynamic voltage scaling and a prototype is built to validate the concepts

Effect of the Tolerances in Multi-Phase DC-DC Converters

Abstract: Multiphase technique is being used in several DC-DC applications such as VRM and automotive. The use of a high number of phases provides several advantages being the reduction of input and output filters one of the most important. However, due to the tolerances of the components (semiconductors and inductors) these advantages are limited. The purpose of this paper is to evaluate the effect of tolerances in the inductance on the output current and voltage ripple. Also, it is shown how the digital control may help to reduce drastically this problem. Experiments are included in the paper

A very simple analytical approach of thermal modeling for magnetic components

Abstract: This work is focused on the analysis of an analytical thermal model for magnetic components. This model can be used to predict the average temperature rise in the outer surface of the device using a very simple expression. The application scope of the model is shown from a practical point of view. An analytical procedure to calculate its parameters is proposed. Finally, the model has been validated using finite element analysis and measurements.

Bridging the gap between FEA field solution and the magnetic component model

Abstract: The use of FEA solvers in order to explore the field distribution is a common practice for designing custom made magnetic components. However, the levering of the field distribution information to the generation of a model valid to be simulated in a circuit simulator is not evident. There are several issues that need to be addressed in order to obtain a model based on the field solution. This paper presents the steps that should be covered to generate a FEA based magnetic component model. In addition to that, the paper describes the appropriate path (analytical or FEA based) that should be followed depending on the model needs

Study of Non-axisymmetric Magnetic Components by means of 2D FEA Solvers

Abstract: FEA solvers provide detailed information about the behavior of magnetic components. This information can be used either to generate models or just to explore the field distribution. Since most of the magnetic components exhibit a 3D field distribution, the most suitable FEA approach is the 3D one. However, 3D FEA solvers are not efficient in terms of "time to solve" the problem or even convergence problems may appear for most of actual designs. Therefore, it is very convenient to propose procedures to make possible the use of 2D FEA solver instead of 3D ones in order to analyze 3D field distributions. This paper presents several rules that can be applied in order to "emulate" the real 3D behavior using 2D FEA solvers

Circuit Oriented Model of Rectifiers for Large Signal Envelope Simulation

Abstract: Envelope simulation has proven to be an efficient tool for the analysis and simulation of resonant converters such as frequency controlled ballasts, series-parallel and parallel resonant converters and converters with piezoelectric transformers. In this work a nonlinear model for the envelope simulation of the half-wave rectifier and full wave rectifier is presented. The model accounts for the input capacitance effect on the rectifiers and can be easily implemented in a circuit oriented simulator. It is valid for transient, DC and AC analysis, what is especially useful for the controller design

High current DC-DC converter with SMT components

Abstract: The use of interleaving techniques in DC/DC converter allows several important advantages such as smaller filters and a better dynamic response. The massive use of this concept may change the design and the look of these converters. In this paper two 1000 W DC/DC converters with automotive specifications have been developed according to this principle. The main result is that the converters are made with surface mounting devices keeping a very high efficiency

Dual-voltage quarter-brick DC-DC converter with control in secondary side

Abstract: This paper presents the design and measurements of a dual output voltage (3.3 V and 2.5 V) quarter-brick DC/DC converter for telecom applications. Secondary-side control is used since outputs must be trimmable and must have very good regulation capabilities. Control architecture is analyzed in detail since the secondary-side control makes more complex other control functions (protections, start-up, etc.)