A Novel Method to Predict the Real Operation of Ferrite Inductors With Moderate Saturation in Switching Power Supply Applications
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This paper presents a method to predict the real operation current wave-shape of Ferrite Core (FC) inductors in switching power supply applications involving a moderate inductor saturation. The method is based on a behavioral analytical model of inductance versus current saturation curve, obtained starting from the data provided by inductors manufacturers. The algorithm developed to solve the nonlinear model of the inductor can be applied to predict the range of the operating conditions involving a sustainable partial saturation for FC inductors, and the resulting method is best suited for the selection of minimum size inductors for high-power-density power supply design solutions.Keywords:
Ferrite core
Saturation (graph theory)
The inductance's high frequency equivalent circuit model is given, and the parameter analysis method is provided from which the material performance of the ferrite core can be obtained. By testing the Insert Loss of the inductance with ferrite core, and then can obtain the effective magnetic permeability. After Testing, analyzing and calculating the inductance with the typical pot core, the curve about the magnetic permeability varying with the frequency is given, and the reason why the errors are produced is analyzed.
Ferrite core
Relative permeability
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In this paper we propose a modeling procedure and the design criterion for the simulation in 2D of an inductor with a POT type ferrite core. The procedure is capable of reproducing the nonlinear magnetic flux-current curve and the corresponding inductance-current curve in the ferrite's complete working range, from the linear to the saturation region. It also reproduces the effect of different air-gap thickness on these curves. The Finite Element simulations are carried out in 2D with the advantages of considerable reduction of the computational cost as well as the ability to achieve convergence. The validation is made for the P22/13 soft ferrite core comparing the results obtained by 2D and 3D simulations with experimental measurements.
Ferrite core
Saturation (graph theory)
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On-chip inductors are key passive elements for future power supplies on chip (PwrSoC), which are expected to be compact and show enhanced performance: high efficiency and high power density. The objective of this thesis work is to study the material and technology to realize small size (<4 mm²) and low profile (< 250 μm) ferrite-based on-chip inductor. This component is dedicated to low power conversion (≈ 1 W) and should provide high inductance density and high quality factor at medium frequency range (5-10 MHz). Fully sintered NiZn ferrites are selected as soft magnetic materials for the inductor core because of their high resistivity and moderate permeability stable in the frequencies range of interest. Two techniques are developed for the ferrite cores: screen printing of in-house made ferrite powder and cutting of commercial ferrite films, followed in each case by sintering and pick-and place assembling to form the rectangular toroid inductor. Test inductors were realized first so that the characterization could be carried out to study the magnetic properties of the ferrite core and the volumetric core losses. The core losses were fit from the measured curve with Steinmetz equation to obtain analytical expressions of losses versus frequency and induction. The second phase of the thesis is the design optimization for the on-chip ferrite based inductor, taking into account the expected losses. Genetic algorithm is employed to optimize the inductor design with the objective function as minimum losses and satisfying the specification on the inductance values under weak current-bias condition. Finite element method for magnetics FEMM is used as a tool to calculate inductance and losses. The second run of prototypes was done to validate the optimization method. In perspective, processes of thick-photoresist photolithography and electroplating are being developed to realize the completed thick copper windings surrounding ferrite cores.
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This paper sets down the major considerations in the design of high frequency AC inductors. It describes two methods for designing the inductor— the area product method and the core geometry method. The two major effects of the inductor air gap, fringing flux power loss and increase of inductance, are discussed. Equations for the inductor design and a step-by-step design procedure are given. The use of a lumped air gap or a distributed air gap are discussed and a comparison of the losses resulting from these gaps together with experimental results are presented.
Ferrite core
Air gap (plumbing)
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Inductors with a Ni-Zn ferrite thin-film prepared by reactive ECR sputtering as a lower magnetic core and a Ni-Zn-Cu ferrite over coat layer as a upper magnetic core was designed using high frequency electromagnetic simulation based on FEM and fabricated in trial. The fabricated inductor with upper and lower magnetic cores showed higher inductance by about 25% than the inductor without magnetic core as predicted by simulation. High inductance value of the inductor with upper and lower magnetic cores was maintained up to high frequency of 1 GHz showing the effectiveness of the ferrite layers.
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A new concept of stacked-spiral inductor fully-filled with VERTICAL closed-circuit nano-particle magnetic core in CMOS is reported. Prototypes, fabricated in a six Al metal layer CMOS backend process using ferrite nanoparticles, show a high inductance-density up to 920 nH/mm 2 in multi-GHz, which is promising for making super compact inductors in RF system-on-a-chip (SoC).
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This paper presents a first assessment of a design method aiming at the minimization of the number of turns $N$ and the air gap length $g$ in ferrite-core based low-frequency-current biased AC filter inductors. Several design cases are carried on a specific model of Power Module (PM) core, made of distinct ferrite materials and having different kinds of air gap arrangements The correspondingly obtained design results are firstly compared with the classic approach by linearization of the magnetic curve to calculate $N$ and the use of a fringing factor to determine $g$. Next, a refined design approach of specifying the inductance roll-off at the peak current and its potential limitations are discussed with respect to our design method. Finally, the behaviour of inductors operated beyond their design specifications is analyzed.
Ferrite core
Linearization
Air gap (plumbing)
Minification
Medium frequency
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A new concept of stacked-spiral inductor with vertical near-closed-circuit nano-particle-magnetic-core in CMOS is reported. Prototypes, fabricated in a 6-Al-metal CMOS backend process using ferrite nano-particles, show a high inductance-density of 825nH/mm 2 in multi-GHz, which is promising for making super compact inductors in RF SoC.
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On-chip stacked-spiral radio-frequency (RF) inductor with vertical nanopowder-magnetic-core was proposed and implemented in standard 0.18 μm six-metal CMOS with a post-CMOS backend process module (i.e., CMOS+). To improve on the prior open-magnetic-circuit-loop structure and thus limited improvement at multi-GHz performance, the non-traditional concept shows vertical magnetic core forming a near closed magnetic loop. The ferrite nanoparticle-magnetic-core reduced magnetic loss to improve L-density to 9 GHz. Results show the proof-of-concept designs greatly increase the inductance, L, by up to 34% and the factor, Q, by 62% over a multi-GHz frequency range.
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Research presented in this paper offer results of influence of fabrication process processing parameters on performance of a solenoid inductor with ferrite core. Embedded solenoid inductor with three half-turn conductive segments that enclose ferrite core was designed for fabrication in LTCC (Low Temperature Co-fired Ceramic) technology. Two inductor samples were fabricated differing in manner of fabrication of the ferrite core. For the first sample, core was formed by inserting stacked ferrite green tapes and co-sintering the whole structure at lower peak temperature. The second inductor enclosed pre-fired core at higher temperature and the whole structure was co-sintered with the first sample in the same firing process. It has been shown that implementation of optimal processing parameters of ferrite material resulted in improvement of inductor performance and increase of its inductance and Q-factor values. Solenoid structure with pre-fired exhibits 26 % increase in inductance value and 45 % increase in Q-factor maximum value.
Ferrite core
Solenoid
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