Ferrite Inductors Research Articles

High-Quality Factor Ni-Zn Ferrite Planar Inductor

Ferrite and air-core planar inductor arrays were fabricated on 4 inch Si wafer to characterize inductor performance. Three micron thick Ni0.5Zn0.5Fe2O4 film was deposited by a low temperature electrophoresis ferrite deposition process. All ferrite inductors in the array showed 35% higher inductance (L) and 130% higher quality factor (Q) than air-core inductor. The maximum Q of ferrite inductor was found to be 53 at 2 MHz. The superimposed DC current and the rated power were measured to be about 3 A and 15 W, respectively, for a 5% drop in L. The fabricated ferrite inductor has a higher current capability than the air-core inductor. In addition, the power efficiency of the buck DC-DC converter was predicted to be 94.3% at 1.93 W.

Accurate modeling of voltage and current waveforms with saturation and power losses in a ferrite core via two-dimensional finite elements and a circuit simulator

This paper presents a new dynamic model of equivalent circuit to simulate in the time-domain the effects of saturation and power losses in a nonlinear magnetic component. The parameters of the model are a nonlinear inductance and a nonlinear loss resistance that are computed via two-dimensional finite elements. The effectiveness of the model is analyzed in the case of a soft ferrite inductor excited by a sinusoidal voltage source at frequencies of 500 Hz and 40 kHz. The resulting voltage and current waveforms of the inductor taken in the laboratory are then compared with those computed via the PSIM circuit simulator. PSIM is a simulation software designed for power electronics, motor control, and dynamic system simulation.

High Q Ni-Zn-Cu Ferrite Inductor for On-Chip Power Module

We fabricated 3 times 3 array of 1 mum thick Ni-Zn-Cu ferrite and air-core planar inductors (5 times 5 mm2 in size; 2.5, 3.5, and 4.5 turns of Cu coil) on 4 inch bare Si wafer and 300 nm thick SiO2/Si wafer, respectively. The ferrite inductor showed higher Q than that of air-core inductor in the range of 7 to 100 MHz. The Q (= 19.5) of 4.5 turn ferrite inductor is 3.3 times higher than that (= 5.9) of 4.5 turn air-core inductor at 10 MHz, and inductance (L) increased by 10%. The Q-factors were found to be about 50 at 2.3 MHz and 20 at 10 MHz, respectively, for the ferrite inductor.

Mg–Cu–Zn Ferrites for Multilayer Inductors

Mg–Cu–Zn ferrites can be sintered at T≤950°C to sufficient density and display adequate permeability profiles for application in multilayer ferrite inductors. The permeability and Curie temperature have to be optimized by proper selection of composition. Ferrites with <50 mol% Fe2O3 reveal enhanced densification behavior. Submicrometer powders prepared by fine milling show good sintering activity and density after firing at 900°C. Nano‐size ferrite powders prepared by coprecipitation or flame synthesis lead to high density; maximum shrinkage already occurs at T<800°C. The use of Bi2O3 as a sintering additive further improves the densification, but also affects the microstructure and, hence, the permeability. A maximum permeability of μi=450–500 is obtained.

감온 페라이트를 이용한 비접촉 온도측정시스템의 감도특성

비접촉 온도측정 시스템을 구현하기 위하여 감온페라이트를 이용하여 제작한 인던턴스소자와 캐피시터를 접속하여 LC공진형 센서를 구성하고, 비접촉 온도계측성능에 대하여 조사하였고, 송수신기 사이의 거리에 대한 측정감도에 대하여 검토하였다. 감온 페라이트가 가지는 투자율의 온도의존성에 의해서 제작한 센서의 인덕턴스와 공진주파수가 변화함을 알 수 있었고, 공진주파수의 변화를 비접촉으로 검출함으로써 비접촉으로 온도를 검출할 수 있음을 알 수 있었다. 또한 비접촉 측정 감도는 송 <TEX>$.$</TEX>수신기 사이 거리의 6승에 비례하는 감소하는 것을 알 수 있었다. To construct the non-contact temperature detection systems, LC resonance type sensors composed of temperature sensitive ferrite inductors and capacitors were used, and their wireless temperature detection performances were investigated. The temperature was wirelessly detectable using the fabricated LC resonance sensors with a transmitter and receiver, because their inductances and resonance frequencies were changed according to the temperature dependance of permeability of the ferrites. The sensitivity of the system was decreased with the distance i between transmitter and receiver as a ratio of the l<TEX>$^6$</TEX>.

Flux measurements and modeling of the magnetic hysteresis for a zero-voltage switching dc-to-dc converter

A half-bridge bidirectional step-up dc/dc converter with zero voltage switching is introduced. The losses in the semiconductors are reduced in this concept but the higher current ripple leads to increased losses in the MnZn ferrite inductor. The resulting unsymmetric hysteresis including minor loops due to switching oscillations is predicted using reversible and irreversible energy contributions.

高周波フェライト直交磁心の鉄損及び温度上昇算定に関する一考察

An orthogonal core is a magnetic device which can continuously control the inductance of the secondary winding with the primary dc current. Recently orthogonal core variable inductors have been used in the high-frequency region. Analysis of this device for high-frequency applications is therefore necessary. We previously proposed an analysis method based on reluctance network analysis (RNA) for the silicon steel orthogonal core used in the commercial frequency region. In order to use the orthogonal core in a high-frequency region, we must consider the increase in the core temperature due to iron loss. In this paper, we calculate the iron loss of a ferrite orthogonal core variable inductor in the high-frequency region, based on RNA, and we estimate the core temperature on the basis of the thermal equivalent circuit.

The study of magnetic circuit design for multilayer ferrite chip inductors

The magnetic circuit of the multilayer ferrite chip inductors can be successfully simulated by the three-dimensional finite element method. The linear and low frequency inductances of different chip types are calculated and compared with the experimental data. The experimental data is quite coincident with the calculated curve. This method of magnetic circuit design can be used to control the conductor pattern and layer structure of MLFC inductors, and provide the evaluation of characteristics before manufacturing.

An enhanced perturbation method for analysis of inductance

The inductance of a ferrite cup core inductor is the sum of two parts. One part is the self-inductance of the winding, The other dominant part can be called the residual inductance. We present a mathematical method for calculating the residual inductance from the geometry of the inductor and the permeability μ of the ferrite. The first step in the method is to develop a pair of perturbation series for the residual inductance, one series in powers of 1/μ, and the other series in powers of μ. The final step is to form a Padé approximant based on these series. The Padé approximant yields a uniformly valid approximation, whereas the series may diverge. We describe an application of the method, and discuss its convergence.

Higher Q from Pot Core Inductors

To obtain the maximum Q (quality factor) from a given inductor structure, the designer must employ his whole bag of design tools. When that inductor operates at several megahertz or more, the bag must often be turned inside out. This paper provides design techniques necessary to maximize inductor Q, with particular emphasis on higher frequency applications. Loss analysis (l/Q) calculations for magnetic core loss and winding losses are discussed. Such practical information as capacitive loss constants and actual measured wire diameters needed for loss calculations are included. How to use the calculations to determine the optimum wire type and size is shown. Optimization examples included are based on actual inductors using IEC 14/8 mm pot cores. The design of a particular ferrite pot core inductor operating in the 15-40-MHz range is outlined. Here the relationship between achieving a given inductance and maximizing Q is explored. Also discussed are special considerations of winding lead placement and hardware effects.

The origin of the increase in magnetic loss induced by machining ferrites

Ferrite inductors are usually made in two parts with mating and air gap surfaces perpendicular to the flux path. In the course of manufacture these surfaces are ground flat, and this machining operation is found to increase the loss factor (L.F.), ( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\tan \delta_{r+F})/\mu_{e}</tex> , by up to 33%, measured at a frequency of 100 kHz. It is known that grinding puts the surface of a ceramic into compression, and it is shown that the stress in the surface approaches 700 MN m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> , decreasing to zero at a depth of 5μm or so below the surface. The permeability in this surface layer is greatly reduced, and so the L.F. is. enormously increased, since tan <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\delta/\mu = \mu"/(\mu')^{2}</tex> . The mean value of the L.F. in this surface layer is estimated to be about <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">600 \times 10^{-6}</tex> , compared with about <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1.5 \times 10^{-6}</tex> in the interior. A theoretical expression is derived for the increase in L.F. of an inductor assembly, induced by grinding the surfaces perpendicular to the flux, which accounts quite well for the change observed. Ground surfaces parallel to the flux have virtually no effect on L.F., since little flux penetrates them, but the stresses which they generate in the body of the ferrite influence the temperature factor.

Examples of electric wave filters using ferrite inductors

The paper deals with an application of ferrite inductors where their high Q-factors are of prime importance. The design and performance of two pairs of complementary low- and high-pass filters using ferrite inductors is discussed. The filters provide a discrimination of 40 dB between pass and stop bands. In the first version, the pass band of the low-pass filter ends at 59·4 kc/s and the stop band begins at 60·6 kc/s In the improved version, the transition range has been reduced to 59·7–60·3 kc/s. The use of these filters as group-separating filters in a 24-circuit carrier-on-cable telephone system is considered.