http://ieeexplore.ieee.org/iel5/5610941/5624686/05624745.pdf

Power electronics

DC–DC converters with voltage boost capability are widely used in a large number of power conversion applications, from fraction-of-volt to tens of thousands of volts at power levels from milliwatts to megawatts. The literature has reported on various voltage-boosting techniques, in which fundamental energy storing elements (inductors and capacitors) and/or transformers in conjunction with switch(es) and diode(s) are utilized in the circuit. These techniques include switched capacitor (charge pump), voltage multiplier, switched inductor/voltage lift, magnetic coupling, and multistage/-level, and each has its own merits and demerits depending on application, in terms of cost, complexity, power density, reliability, and efficiency. To meet the growing demand for such applications, new power converter topologies that use the above voltage-boosting techniques, as well as some active and passive components, are continuously being proposed. The permutations and combinations of the various voltage-boosting techniques with additional components in a circuit allow for numerous new topologies and configurations, which are often confusing and difficult to follow. Therefore, to present a clear picture on the general law and framework of the development of next-generation step-up dc–dc converters, this paper aims to comprehensively review and classify various step-up dc–dc converters based on their characteristics and voltage-boosting techniques. In addition, the advantages and disadvantages of these voltage-boosting techniques and associated converters are discussed in detail. Finally, broad applications of dc–dc converters are presented and summarized with comparative study of different voltage-boosting techniques.

/pdf/step-up-dc-dc-converters-a-comprehensive-review-of-voltage-6dlytctzg2.pdf

Step-Up DC–DC Converters: A Comprehensive Review of Voltage-Boosting Techniques, Topologies, and Applications

The authors discuss high-voltage power conversion. Conventional series connection and three-level voltage source inverter techniques are reviewed and compared. A novel versatile multilevel commutation cell is introduced: it is shown that this topology is safer and more simple to control, and delivers purer output waveforms. The authors show how this technique can be applied to either choppers or voltage-source inverters and generalized to any number of switches.<<ETX>>

Multi-level conversion : high voltage choppers and voltage-source inverters

A comparison of on-chip inductors with magnetic materials from previous studies is presented and examined. Results from on-chip inductors with magnetic material integrated into a 90 nm CMOS processes are presented. The inductors use copper metallization and amorphous Co-Zr-Ta magnetic material. Inductance densities of up to 1700 nH/mm2 were obtained thanks to inductance increases of up to 31 times, significantly greater than previously published on-chip inductors. With such improvements, the effects of eddy currents, skin effect, and proximity effect become clearly visible at higher frequencies. Co-Zr-Ta was chosen for its good combination of high permeability, good stability at high temperature (> 250degC), high saturation magnetization, low magnetostriction, high resistivity, minimal hysteretic loss, and compatibility with silicon technology. The Co-Zr-Ta alloy can operate at frequencies up to 9.8 GHz, but trade-offs exist between frequency, inductance, and quality factor. Our inductors with thick copper and thicker magnetic films have dc resistances as low as 0.04 Omega, and quality factors of up to 8 at frequencies as low as 40 MHz.

Review of On-Chip Inductor Structures With Magnetic Films

The trend toward high power density, high operating frequency, and low profile in power converters has exposed a number of limitations in the use of conventional wire-wound magnetic component structures. A planar magnetic is a low-profile transformer or inductor utilizing planar windings, instead of the traditional windings made of Cu wires. In this paper, the most important factors for planar transformer (PT) design including winding loss, core loss, leakage inductance, and stray capacitance have individually been investigated. The tradeoffs among these factors have to be analyzed in order to achieve optimal parameters. Combined with an application, four typical winding arrangements have been compared to illustrate their advantages and disadvantages. An improved interleaving structure with optimal behaviors is proposed, which constructs the top layer paralleling with the bottom layer and then in series with the other turns of the primary, so that a lower magnetomotive force ratio m can be obtained, as well as minimized ac resistance, leakage inductance, and even stray capacitance. A 1.2-kW full-bridge dc-dc converter prototype employing the improved PT structure has been constructed, over 96% efficiency is achieved, and a 2.7% improvement, compared with the noninterleaving structure, is obtained.

https://orbit.dtu.dk/files/4566316/Ouyang.pdf

Optimal Design and Tradeoff Analysis of Planar Transformer in High-Power DC–DC Converters

The integration of photovoltaic (PV) modules in buildings causes problems with shadows that can strongly reduce the energy produced by these systems. Moreover, most PV modules are designed for stand-alone applications that have output voltage adapted to lead batteries. Indeed, this historical sizing of PV modules can be discussed in the case of grid-connected systems. In this paper, a cascaded dc/dc converter based on boost chopper is proposed. First, the advantages and the limits of this topology will be shown. Second, this topology will be optimized to maximize the efficiency or minimize the volume. The originality of this optimization is that the converters' parameters and the arrangement of the PV cells are variable parameters. Indeed, the optimization is done on the entire system. To realize these optimizations, semiempiric models of losses and volumes of different components of a boost chopper were developed. The optimization uses a successive quadratic programming algorithm. Considering the optimization results over the whole range of the specifications, a flexible solution is developed and experimental results are presented. Finally, optimized topologies connected to several PV are evaluated at different situations of typical shadows.

Optimization and Design of a Cascaded DC/DC Converter Devoted to Grid-Connected Photovoltaic Systems

As a consequence of the increase of power needs in low-voltage applications, wiring several windings in parallel to sustain large currents has become common. This choice may have a serious impact on the transformer reliability. In practice, due to additional currents that we call “circulation currents,” highly localized extra losses occur. Although hot points resulting from these currents can destroy the component, the related losses are generally not taken into account by analytical approaches. In planar transformers, windings are made of printed circuit board layers, and circulation currents lead to severe unbalance of current sharing between parallel layers. This paper presents an analytical method enabling the evaluation of the currents in every layer using only a circuit simulation software such as Pspice or PSIM. For a designer, this method is very intuitive and fast compared with the use of finite element method simulations. Several extensions of the modeling method used here are also presented.

https://hal.archives-ouvertes.fr/hal-00289169/document

Current Sharing Between Parallel Turns of a Planar Transformer: Prediction and Improvement Using a Circuit Simulation Software

We present a new structure of a non isolated DC-DC converter, named interleaved double dual boost (IDD boost), applied in the concept of the power electronic interface for fuel cell stationary applications In the first part, the operation of the structure is highlighted The interleaving technique is introduced to solve the problem of high current — low voltage and low current ripple imposed by FC, to reduce the average current, to minimize components losses and to facilitate inductors manufacture The structure coupling offers a high transformer ratio without degrading much the efficiency which is always a limit of non isolated structures It also reduces the dimensioning voltage and permits a flexible choice of semiconductors and capacitors In the second part, in the aim of looking for an optimal converter structure, the study begins by the presentation of all possible system configurations Then, components losses models are built A systematical losses evaluation gives us a global view on the interesting features of the IDD boost, the interests and limits of the interleaving technique, the components choice strategy and the optimal system architecture

New high power - high ratio non isolated DC-DC boost converter for fuel cell applications

This paper deals with the design and the realization of an integrated isolated HF dc-to-dc converter for low-voltage and low-power conditioning applications (3.3 V and 1 W) including galvanic isolation. It is based on the 3-D integration of several elementary silicon dies in which essential components such as the inverter, the rectifier, the HF transformer, the input and output capacitors, and the output inductor have been integrated. The paper deals with the silicon integration of all these elements, with the presentation of our work being related with the state of the art. Then, it focuses on an estimate of the whole converter functional performance at 1-MHz switching frequency. Practical but partial implementation was carried out. The inverter and the rectifier are designed in CMOS technology (Austria Micro Systems 0.35 μm) and have been optimized to operate at HF (1 MHz) to reduce the size of passive devices. We have monolithically integrated all that is necessary for this function. The transformer, as well as the inductor and the capacitors, is also integrated on separate silicon dies. Their integration is discussed, as well as their design and practical characterization. Based on a distributed construction, the overall converter efficiency is estimated in simulation based on practical characterizations. It appears that correct efficiency with a reasonable silicon surface and volume can be reached.

Design and Realization of Highly Integrated Isolated DC/DC Microconverter

Energy storage systems are critical elements in electric vehicle (EV) and hybrid electric vehicle (HEV) applications. In these systems, lithium-ion batteries are preferred for their outstanding characteristics and advantages: high power density, long life cycles and high efficiency. For high voltage applications, batteries cells are connected in series, raising the issue of voltage balancing among cells. This paper presents a new structure of active voltage balancing of Li-ion cells associated in series in battery stack. It is based on the use of micro-converters network. The principle of the charge equalization is to derive energy from an overcharged cell and to transfer it to an undercharged cell no matter whether the battery is currently in charge or in use supplying a load. The highlight of this structure is not only its high efficiency and its ease of implement but moreover, its integration capacity in contrast to state of the art passive and active balancing topologies. A monitoring system is required to perform forced balancing. The results from simulations and experimental test bench validate the feasibility and the interest of the proposed balancing circuitry and operating principle.

Yves Lembeye

Papers

Optimization and Design of a Cascaded DC/DC Converter Devoted to Grid-Connected Photovoltaic Systems

Current Sharing Between Parallel Turns of a Planar Transformer: Prediction and Improvement Using a Circuit Simulation Software

New high power - high ratio non isolated DC-DC boost converter for fuel cell applications

Design and Realization of Highly Integrated Isolated DC/DC Microconverter

Voltage balancing converter network for series-connected battery stack