Comparison between air-core and laminated iron-core inductors in filtering applications for switching converters
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Inductors for filtering devices are widely employed in power electronics applications in order to reduce voltage and current harmonics caused by switching converters. The use of ferrite-core inductors is limited to small power applications, whereas air-core and laminated iron-core inductors are employed in the medium-to-high power range. The choice of the core medium strongly affects the behavior of the inductor versus frequency. In particular, the inductance, the self-resonant frequency, the winding and core losses and the stray magnetic field are quite different for air-core and laminated iron-core inductors. In this paper a comparison between these two kinds of inductors is carried out through an analytical approach and experimental validations.An original Z transform-based algorithm is used to develop a fast and accurate tool for the dynamic analysis of switch-mode power converters and to achieve insight into the effect of each parasitic. It is shown that iron losses can be neglected without impairing the compliance in the analysis of all the single-inductor converters and also of the two-inductor converters without magnetic coupling. These losses must be included in the modeling of coupled inductor converters, since their effect on the control-to-output gain can jeopardize the feedback loop stability. Experimental data for a low-power prototype are reported.< >
Inductive coupling
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Inductors with small footprints and low profile are vital to the development of high density converters with optimal power conversion, inductors that can embedded should be considered as they provide excellent characteristics. This paper investigates a type of planar magnetic inductor which uses magnetic shielding over an air inductor, instead of using a regular core material. A synchronous buck-boost DC-DC converter is built to verify the effectiveness of the semi-shielded inductor compared to the planar inductor. Furthermore, inductance characteristics are investigated, using the MadMix inductor test system.
Shielded cable
Buck converter
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Principles and possibilities for design of digital to analog converters for application in CMOS ternary digital systems are proposed and described in the paper. Such converters perform signal conversion from ternary digital signals into analog signal. General principle and structure for implementation and design of CMOS ternary to analog converters are considered and proposed first. Then, as example of the design, concrete circuits for implementation of two digit CMOS ternary to analog converters are proposed. Two types of converters are described: powerful type converters and simple type converters. Given solutions were analyzed using computer simulations and all descriptions and considerations were confirmed by the simulations.
Analogue electronics
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Miniaturized thin film inductors with various shaped magnetic cores are described. The dimensions of these inductors are about 2 mm × 2 mm. Since they are used at frequencies above 100 MHz, the effective utilization of the magnetic core must be considered. We measured the inductance of inductors with magnetic cores of various shapes, and investigated the flux density distribution. The inductors were based on from 100 to 240 core pieces, each piece with from one to three coil turns. The conductor of these inductors was confined to a single plane to prevent connection defects. According to measured results, the inductor with the highest inductance per unit area employed two-turn magnetic core pieces. There was no significant difference in the inductance of closed-loop and open-loop core constructions.
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A novel and simple method to distinguish winding loss from inductor loss under practical excitations
Previous methods for measuring magnetic core loss are either only suitable for sine wave excitations or cannot separate winding loss from inductor loss. In this paper, we present a new method to distinguish winding loss from inductor loss under practical excitations. This method utilizes a converter to generate the actual excitation waveforms and uses a calorimetric setup to quantify the losses. By splitting up the inductor in a converter into an air core inductor and a magnetic core inductor, both equipped with exactly the same winding structure, the air core inductor loss can be used as the reference of the magnetic cored inductor winding loss. In this way, magnetic core losses can be determined in the actual operation condition of a converter in which the inductor is to be used. The method requires simple setup and is easy to execute. It worked well in assessing different magnetic core materials.
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This paper describes the modeling and design of package-embedded magnetic-core inductors for a system-in-package-based high-efficiency integrated voltage regulator. An application example is used to demonstrate the complete design process, starting with the fabrication of two candidate magnetic composite materials. Based on the measured properties of these materials, magnetic-core inductors are designed and simulated using full-wave simulations. Finally, the overall voltage regulator efficiencies resulting from inductor designs are obtained from analytical equations, which allows for rapid evaluation of different scenarios. Voltage regulator efficiency with magnetic-core inductors is seen to be considerably higher than with similarly sized air-core inductors. Notably, this is even true at high switching frequencies where the magnetic-core inductors have lower quality factors than the air-core inductor.
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This paper deals with the evaluation of the PFC inductor core losses, while different magnetic core geometry as well as material is being considered. Initially, the most important characteristics and variables of the magnetic properties are given, which are required for proper design and power loss estimation of inductor. Then, comparative analysis related to power loss estimation is provided, while ferrite material in two different shapes is compared with alloy core material. Presented results show how important is proper selection of geometry as well as material of inductor in PFC circuits.
Ferrite core
Magnetic circuit
Power loss
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Inductors for filtering devices are widely employed in power electronics applications in order to reduce voltage and current harmonics caused by switching converters. The use of ferrite-core inductors is limited to small power applications, whereas air-core and laminated iron-core inductors are employed in the medium-to-high power range. The choice of the core medium strongly affects the behavior of the inductor versus frequency. In particular, the inductance, the self-resonant frequency, the winding and core losses and the stray magnetic field are quite different for air-core and laminated iron-core inductors. In this paper a comparison between these two kinds of inductors is carried out through an analytical approach and experimental validations.
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Incremental converters provide a solution for such measurement applications, as they retain most of the advantages of conventional ΔΣ converters, and yet they are capable of offset-free and accurate conversion. Most of the previous research on incremental converters was for single-channel and dc signal applications, where they can perform extremely accurate data conversion with more than 20-bit resolution. In this paper, a design technique for implementing multi-channel incremental data converters to convert narrow bandwidth ac signals is discussed. It incorporates the operation principle, topology, and digital decimation filter design. The theoretical results are verified by simulation results.
Decimation
Data conversion
Delta-sigma modulation
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Recently, thin film inductors are reported by many authors (1-3). These thin film micro inductors are investigated in the point of design of exciting coil and magnetic core. The most difference of electric properties between the thin film inductor and chip inductor is that quality factor (Q) of thin film inductor is lower than that of chip inductor using ferrite magnetic core in same inductance (L). To get the high quality factor, it is important to use the magnetic core in which iron loss is small in high frequency. On the other hand, it is well known that in multilayer magnetic films, generally, the permeability is high and iron loss is small. In this paper, it is proposed that the multilayer magnetic core is useful to increase Q in thin film inductor. The experimental inductor shows L of 100nH, Q=18 at 50 MHz in its size of 0.5x2mm 2 .
Ferrite core
Q factor
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