1,721,025 research outputs found
EMI Worsening in a SMPS with Non-linear Inductor
Full text linkThis paper is focused on the input current in a Switched Mode Power Supply (SMPS) in which the power inductor is exploited up to the saturation showing a non-linear behaviour. The input current exhibits a distortion due to the non-linearity. The electromagnetic interference (EMI) caused by the ripple at switching frequency, superimposed to the DC value of the input current, requires a suitable design of the input differential mode (DM) filter. The input current is analyzed both in the time and frequency domain for different operating conditions, and it is compared to a SMPS equipped with a traditional linear inductor
Characterization of inductors in partial saturation for SMPS applications
No full textThe exploitation of partially saturated inductors in Switching Mode Power Supply (SMPS) is
a key strategy for reducing the size of SMPS and increasing their power density [1]. However
an accurate characterization and modellization of each inductor is needed for a correct design
and control of the SMPS [2]. Most of inductors’ datasheets only indicate the nominal
inductance at low current. Anyway, when the inductor is subjected to a higher current, the
value of the inductance is lessened. Moreover, inductance meters often actuate their
measurements at no or moderate DC bias. In this work we describe the realization of an
automated test bench (Fig. 1) for characterizing an inductor under variable current levels,
moving its operating point form the linear region to the partial saturation region [3].
The core of the measurement setup is a simple buck converter, used for applying a square
wave voltage to the inductor under test (Fig. 1). The current flowing through the inductor is
measured by a Hall-effect current transducer. In order to measure the inductance at different
values of the DC bias current, a constant current sink is placed after the LC filter as a variable
load. The measurement is carried out by exploiting the inductor constitutive equation
VL = L dIL/dt , rewritten as: L = VL / (dIL/dt). For small current variations, the value of L can
be considered constant and depending only on the average current. The DC bias current, the
frequency and duty-cycle of the switching element can be controlled by a virtual instrument
developed in LabVIEW, which also takes care of data acquisition and post elaboration
(Fig.2).
Several inductors have been tested using the described setup. Figure 3 shows a typical plot of
the inductance L versus the inductor current IL . The inductor under test has a rated value of
470 μH. The partial saturation of the inductor is quite evident. Reproducibility tests have been
performed on the system, by comparing the results of several measurements on the same
inductor. Standard deviation bars, indicated in the plot, show the acceptable precision of the
method, the results being well within 1%. The absolute accuracy has not been tested due to
the lack of calibrated reference inductors, however the inductance values measured at low
currents are in good agreement with nominal values
Design and realization of a DC/DC converter with a partially saturated inductor
No full textDC/DC converters, in some types of applications such as portable equipments, can require
more space than it is actually available. The inductor is typically the most bulky element and
the possibility to reduce its size can save up to 50% of the converter volume and area [1][2],
thus increasing the power density. This reduction, however, comes with nonlinear effects
caused by the saturation of the ferromagnetic core. An appropriate modelling of the inductor
and of the converter circuit is needed for guaranteeing a good output power quality (Fig. 1).
A Boost converter with an inductor in the partially saturated roll-off operating zone was
designed and realized to study the behaviour of DC/DC converters with nonlinear inductors
(Fig. 2). The main components of the circuit are listed in Table I. An innovative polynomial
model of the inductor [3] has been used for the circuit simulations. The Boost circuit model is
derived from [4]. The converter control system has been implemented on a Nucleo64-
STM32F401RE microcontroller; this system manages the startup of the converter, regulates
the output voltage and implements a control of the inductor current via a current loop (Fig. 3).
An example of the system stability under a 10% step variation of the load is shown in Fig. 4.
For the experimental measurement a test rig has been set up, the elements of which are listed
in Table II. Initially, the converter is operated at high frequency (f=15 kHz) with low current
ripple. By changing the average current, the inductor is characterized in its linear and partial
saturation zones. Then, the current ripple is increased to 2A by decreasing the switching
frequency to 2 kHz, in order to simulate an equivalent reduction of the inductor value (volume
reduction); in this case, the cusp-shaped current waveform, typical of saturated inductors, can
be noted (Fig. 5). Finally the converter has been forced to work in discontinuous conduction
mode (DCM) by increasing the load resistance; even in this case the current control system
guarantees the output voltage regulation and the system stability (Fig.6).
In conclusion, in this work the reduction of the inductor volume has been considered together
with its two main consequences: the non-linear behaviour for heavy loads and the
discontinuous conduction mode (DCM) for light loads. In both cases, it has been shown that
the converter is able to handle partial saturation and to operate correctly in DCM thanks to the
current control with consequent beneficial effects on power density
Non-Linear Inductor Models Comparison for Switched-Mode Power Supplies Applications
Full text linkThe use of non-linear power inductors, intended as devices exploited up to a current at which the inductance is halved, is of great interest in switched-mode power supplies (SMPSs). Indeed, it allows the use of lighter and cheaper inductors improving the power density. On the other hand, the analysis of SMPSs equipped with non-linear inductors requires appropriate modeling of the inductor reproducing the inductance versus current. This paper compares two main analytical models proposed in the literature: the former is based on a polynomial, and the latter exploits the arctangent function to reproduce the non-linearity of the inductance. Performance is compared by considering the effort of retrieving the model’s parameters, evaluating a current profile by the characteristic equation of the inductor, and exploiting the two models to simulate a switched-mode power supply. Results are given both in terms of computation time and accuracy with reference to experimental values, highlighting the pros and cons of each model
Experiments on chaotic circuits and crypted data transmission
No full textThe basic concepts of deterministic chaos have been recently included in several classes for undergraduate students, both in Engineering and Physics courses. An experimental approach proves effective in raising the learning rate for students who face for the first time these new concepts. In this paper we propose a versatile electronic circuit for chaos generation and observation, which can also be used in experiments on crypted data transmission
A Temperature Dependent Non-Linear Inductor Model for a DC/DC Boost Converter
No full textThis paper is focused on the use of non-linear inductors in DC/DC switching converters, as well as their behaviour due to changes in current and temperature. The model of an inductor is set up on the basis of experimental data, which are automatically acquired by a virtual instrument; from those data, a polynomial curve describing the inductance variations is obtained. The analysis of the converter, performed by including the proposed model, is validated by experimental tests
Technologies for the fabrication of cylindrical fine line devices
No full textA microlithographic process suited for metal patterning on cylindrical dielectric substrates has been developed. This includes all steps from metal coating to final etching, with resolution in the 5 μm range
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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