1,720,976 research outputs found
Identification of DC thermal steady-state differential inductance of ferrite power inductors
Get PDFIn this paper, we propose a method for the identification of the differential inductance of saturable ferrite inductors adopted in DC–DC converters, considering the influence of the operating temperature. The inductor temperature rise is caused mainly by its losses, neglecting the heating contribution by the other components forming the converter layout. When the ohmic losses caused by the average current represent the principal portion of the inductor power losses, the steady-state temperature of the component can be related to the average current value. Under this assumption, usual for saturable inductors in DC–DC converters, the presented experimental setup and characterization method allow identifying a DC thermal steady-state differential inductance profile of a ferrite inductor. The curve is obtained from experimental measurements of the inductor voltage and current waveforms, at different average current values, that lead the component to operate from the linear region of the magnetization curve up to the saturation. The obtained inductance profile can be adopted to simulate the current waveform of a saturable inductor in a DC–DC converter, providing accurate results under a wide range of switching frequency, input voltage, duty cycle, and out-put current values
The role of materials in the optimal design of magnetic components for DC–DC converters
No full textThis paper analyses the design of the output inductor of a DC–DC converter, comparing the performances achieved by three different core materials to reach the best trade-off between the total losses and the size of the magnetic component. The N87 ferrite, the Xflux60 silicon iron powder, and the Metglas 2605 SA-1 iron-based amorphous are considered in the present analysis. An equivalent non-linear reluctance model is adopted to compute the differential inductance profile of each design configuration. The total losses are estimated with analytical computations. Several considerations are presented in comparing the different core materials, and the optimum design criteria in different configurations are investigated
Saturable Ferrite Inductor Parameters Obtained through a Double Step Optimization
No full textThis paper deals with the modelling of ferrite inductors considering weak saturation operating conditions. The proposed methodology is based on a parametric representation of the magnetic characteristic of the inductor that is optimized through a double-step identification/optimization algorithm. The obtained magnetic characteristic is applied in a simulator to compute the inductor current. To demonstrate the effectiveness of this approach the inductor is tested in a DC-DC buck power converter. Two experimental cases are presented: the former regarding a low voltage, low current, MOSFETs buck converter; the second case regarding a 110W GaN-based buck converter up to 1MHz
Extended ZVS/ZCS operation of Class-E Inverter for Capacitive Wireless Power Transfer
No full textIn this work, a control strategy for a Class-E inverter for Capacitive Wireless Power Transfer (CWPT) application is proposed. The presented approach allows to stabilize the output power regulating the components values of the resonant tank. A matrix of capacitors is used to adjust the values of capacitances and the magnetic design procedure for the variable inductor is proposed. The obtained performances are evaluated through Plecs simulations and compared with the case without a control strategy
Low-Voltage GaN FET in High Power Density Half-Bridge LED Driver
No full textIn the paper, a half-bridge GaN FETs-based converter for a LED driver circuit is investigated. The reduced size of the GaN devices allows reaching high power density compared with the pure silicon devices. The main technology and electrical characteristics are recalled to demonstrate the advantageous features in the DC-DC applications such as of Synchronous Buck Converter. The dead time reduction, the parasitic capacitors, and stray inductances impact the switching operation is described. Furthermore, the control approach and the GaN FETs related issues are investigated. Finally, the switching evaluation of an SBC with an output power of 120W at 1MHz of switching frequency is carried out highlighting the thermal behavior
Identification of material properties and optimal design of magnetically shielded rooms
Get PDFIn this paper, we propose an optimal design procedure for magnetically shielded rooms. Focusing on multi-layer ferromagnetic structures, where inner layers operate at very low magnetic field, we propose an identification method of the magnetic material characteristic in the Rayleigh region. A numerical model to simulate the shielding efficiency of a multi-layer ferromagnetic structure is presented and experimentally tested on different geometries and layer configurations. The fixed point iterative method is adopted to handle the nonlinearity of the magnetic material. In conclusion, the optimization of the design parameters of a MSR is discussed, using the Vector Immune System algorithm to minimize the magnetic field inside the room and the cost of the structure. The results highlight that a linear magnetic characteristic for the material is sufficient to identify the suitable geometry of the shield, but the nonlinear model in the Rayleigh region is of fundamental importance to determine a realistic shielding factor
Data-Driven Constraint Handling in Multi-Objective Inductor Design
Get PDFThis paper analyses the multi-objective design of an inductor for a DC-DC buck converter. The core volume and total losses are the two competing objectives, which should be minimised while satisfying the design constraints on the required differential inductance profile and the maximum overheating. The multi-objective optimisation problem is solved by means of a population-based metaheuristic algorithm based on Artificial Immune Systems (AIS). Despite its effectiveness in finding the Pareto front, the algorithm requires the evaluation of many candidate solutions before converging. In the case of the inductor design problem, the evaluation of a configuration is time-consuming. In fact, a non-linear iterative technique (fixed point) is needed to obtain the differential inductance profile of the configuration, as it may operate in conditions of partial saturation. However, many configurations evaluated during an optimisation do not comply with the design constraint, resulting in expensive and unnecessary calculations. Therefore, this paper proposes the adoption of a data-driven surrogate model in a pre-selection phase of the optimisation. The adopted model should classify newly generated configurations as compliant or not with the design constraint. Configurations classified as unfeasible are disregarded, thus avoiding the computational burden of their complete evaluation. Interesting results have been obtained, both in terms of avoided configuration evaluations and the quality of the Pareto front found by the optimisation procedure
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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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