Micro-fabrication and Circuit Optimization for Magnetic Components of High-efficiency DC-DC Converters
Micro-fabrication and Circuit Optimization for Magnetic Components of High-efficiency DC-DC Converters

Author: Rui Tian

Publisher:

Published: 2014

Total Pages: 174

ISBN-13:

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Magnetic components are essential parts of power converters. Inductors with magnetic cores are investigated. An eddy current loss model for pot-core inductors is developed with finite elemental analysis (FEA). The reliability of inductors using magnetic cores in a high-temperature environment is investigated. Working in up to 150°C circumstance for a short periods is not destructive for the inductors. Optimization of toroidal inductors in a DC-DC converter is investigated. Parasitic capacitance and the capacitive loss in toroidal inductors are modeled. Standard circuit optimization is performed to explore the energy conversion efficiency of the toroidal inductors. Thermal analysis, light-load efficiency and relative permeability of the toroidal inductor design are also investigated. The toroidal inductor can achieve about 85% efficiency for 3 A DC current and 1 W/mm2 power density. Inductor-only efficiency of toroidal inductors is investigated with revised model. At 100 MHz operating frequency, toroidal inductors can achieve more than 97% inductor efficiency with power density range of 0.7 W/mm2 to 6 W/mm2. The performance of our nanograngular magnetic core is dependent on the angle of the poling magnetic field compared to the field during operation. Experiments on a serious of samples show that the poling angle can deviate by up to 15 degrees from ideal with only a small penalty in performance. The field-angle experiment is intended to prove integrated toroidal inductor process possible. A magnetic fixture model is proposed for large-scale toroidal inductor processing.

Magnetics Design for High Current Low Voltage DC/DC Converter
Magnetics Design for High Current Low Voltage DC/DC Converter

Author: Hua Zhou

Publisher:

Published: 2007

Total Pages: 155

ISBN-13:

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With the increasing demand for small and cost efficient DC/DC converters, the power converters are expected to operate with high efficiency. Magnetics components design is one of the biggest challenges in achieving the higher power density and higher efficiency due to the significant portion of magnetics components volume in the whole power system. At the same time, most of the experimental phenomena are related to the magnetics components. So, good magnetics components design is one of the key issues to implement low voltage high current DC/DC converter. Planar technology has many advantages. It has low profile construction, low leakage inductance and inter-winding capacitance, excellent repeatability of parasitic properties, cost efficiency, great reliability, and excellent thermal characteristics. On the other side, however, planar technology also has some disadvantages. Although it improves thermal performance, the planar format increases footprint area. The fact that windings can be placed closer in planar technology to reduce leakage inductance also often has an unwanted effect of increasing parasitic capacitances. In this dissertation, the planar magnetics designs for high current low voltage applications are thoroughly investigated and one CAD design methodology based on FEA numerical analysis is proposed. Because the frequency dependant parasitic parameters of magnetics components are included in the circuit model, the whole circuit analysis is more accurate. When it is implemented correctly, integrated magnetics technique can produce a significant reduction in the magnetic core content number and it can also result in cost efficient designs with less weight and smaller volume. These will increase the whole converter's power density and power efficiency. For high output current and low output voltage applications, half bridge in primary and current doublers in secondary are proved to be a very good solution. Based on this topology, four different integrated magnetics structures are analyzed and compared with each other. One unified model is introduced and implemented in the circuit analysis. A new integrated magnetics component core shape is proposed. All simulation and experimental results verify the integrated magnetics design. There are several new magnetics components applications shown in the dissertation. Active transient voltage compensator is a good solution to the challenging high slew rate load current transient requirement of VRM. The transformer works as an extra voltage source. During the transient periods, the transformer injects or absorbs the extra transient to or from the circuit. A peak current mode controlled integrated magnetics structure is proposed in the dissertation. Two transformers and two inductors are integrated in one core. It can force the two input capacitors of half bridge topology to have the same voltage potential and solve the voltage unbalance issue. The proposed integrated magnetics structure is simple compared with other methods implementing the current mode control to half bridge topology. Circuit analysis, simulation and experimental results verify the feasibility of these applications.

Integrated Magnetics for Future DC-DC Microprocessor Power Delivery
Integrated Magnetics for Future DC-DC Microprocessor Power Delivery

Author: Brice Jamieson

Publisher:

Published: 2010

Total Pages: 288

ISBN-13:

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Integrated, switched-mode DC-DC converters are becoming widely adopted for in-package or on-chip power supply applications, however a limiting factor in their development is the relatively large size of passive components which are necessary in such a converter. By increasing the switching frequency above 100 MHz, a significant reduction in the inductance necessary for such a converter may be achieved and as a result a dramatic reduction in micro-inductor sizes may be afforded. Although considerable work has been done in the field of high-frequency micro-inductors on silicon, most of these devices have attempted to increase the inductance of such a structure at the expense of current-handling capacity, resulting in a low-power device. High-power micro-inductors, additionally, have only recently achieved a 100 Mhz operation frequency at the expense of significant losses in the thin-film magnetic enhancement layers used in these structures. If a high-power device is to successfully operate at 100 MHz with low loss, a combination of improved device design and novel magnetic thin-films is necessary. The goal of this work is to define the parameters of a high-frequency, power micro-inductor suitable for integration into an on-chip power conversion module. To achieve this goal, device and material models were developed for the first time to characterise these devices. Magnetic thin-films were characterized to ascertain the suitability of an electrodeposited thin-film as a replacement for RF-sputtered materials, desirable for the ability of an electrodeposited material to be plated in conformally thicker layers to achieve the required power density. Thin-film models were developed to extend the high-frequency permeability spectrum to account for the conductive seed layer present in an electrodeposited thin-film and the effects of shape and material thickness on anisotropy and permeability were modelled. These material models were verified against experimentally measured thin-films and determined to accurately predict the parameters of a thin-film material when it is integrated into a bounded geometry such as would be present in a micro-inductor. Device models were developed which analyze the inductance and loss in a micro-inductor structure, taking into account the shape-dependent anisotropy model and the presence of magnetic core-closure structures deposited to close the flux path between magnetic planes in a structure. The presence of gap in these core-closures is also considered which considers the cases of a non-magnetic and a magnetic gap. These models were verified against finite-element analysis as well as against fabricated micro-inductors. Finally, optimised stripline micro-inductors were fabricated and characterised for high-current and for high-frequency operation. Comparing these devices to the values expected from the device model, it is seen that the effects of shape and thickness predicted by the analytic models are seen in the fabricated structures, as well as a dependency of these on the magnitude of the AC current through the micro-inductors.

Investigation on Performance Advantage of Functionally Integrated Magnetic Components in Decentralised Power Electronic Applications
Investigation on Performance Advantage of Functionally Integrated Magnetic Components in Decentralised Power Electronic Applications

Author: Kleeb, Thiemo

Publisher: kassel university press GmbH

Published: 2017

Total Pages: 276

ISBN-13: 3737602263

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The functional integration of magnetic components is a known technique in order to enable high power densities for power electronic converters. Magnetic components are mandatory in many power electronic converters and many topologies demand more than one magnetic component. Therefore, the functional integration of magnetic components allows realising several magnetic functions within one component. This technique promises lower total size, losses and costs without switching frequency increase. There are several examples in the literature for coupled inductors, common-differential-mode chokes or transformer-inductor components. One centralised question of this work is to explore the performance advantage of functionally integrated magnetic components in comparison to discrete components. Many applications allow the introduction of simple magnetic structures and standard cores or simple modifications of these (flux bypasses) in order to enable the required component behaviour. The design guidelines introduced in this work enable the design of functional integrated magnetic components with limited effort and, therefore, the application of components which enable superior performance regarding size and power loss for the applications.

Integrated Magnetics for High Current, Low Voltage Power Converter
Integrated Magnetics for High Current, Low Voltage Power Converter

Author: Ningning Wang

Publisher:

Published: 2005

Total Pages: 208

ISBN-13:

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The objective of this work is to develop analytical models for micro-transformers and micro-inductors with a view to understand the various loss mechanisms and optimisation of the design. An analytical model for transformers has been developed, which is based on the estimation of the parameters of the standard equivalent circuit. This model is validated by the finite element analysis and the measurements on the prototypes fabricated. In order to take into account the non-linear behaviour of the magnetic core, a dynamic model is also developed in this work, which can accurately model the transient performance of the device. A variation on the transformer analytical model has been developed especially for micro-inductors. The model uses the same eddy current and hysteresis model. However Dowell{u2019}s 1D approach to the calculation of the winding loss was found not to be accurate for the inductor. A new approximated 2.D winding loss model has been developed in order to give much more accurate prediction of the winding losses compared to those conventional one-dimension solution. The simple approach to model the air gap used for conventional magnetic components is not accurate for this case because of the fringing effect. An air gap model has been developed, which allows an accurate prediction of the inductance. Again, the analytical model for micro-inductors is validated by the finite element analysis as well as the measurements on the prototypes. The analytical models developed are further employed in the design optimisation. Based on the small signal measurements, the newly designed micro-transformer prototypes can achieve 78% efficiency with a power density of 28.8 W/cm2 and the fabricated micro-inductor can achieve 89.5% efficiency with a power density of 12 W/cm2 at 5MHz, which shows a significant improvement comparing to the performance of micro-magnetics reported in the literature.