Giulia Di Capua

An Enhanced Model for Small-Signal Analysis of the Phase-Shifted Full-Bridge Converter

This paper presents an in-depth critical discussion and derivation of a detailed small-signal analysis of the phase-shifted full-bridge (PSFB) converter. Circuit parasitics, resonant inductance, and transformer turns ratio have all been taken into account in the evaluation of this topologys open-loop control-to-output, line-to-output, and load-to-output transfer functions. Accordingly, the significant impact of losses and resonant inductance on the converters transfer functions is highlighted. The enhanced dynamic model proposed in this paper enables the correct design of the converter compensator, including the effect of parasitics on the dynamic behavior of the PSFB converter. Detailed experimental results for a real-life 36 V-to-14 V/10 A PSFB industrial application show excellent agreement with the predictions from the model proposed herein.

A Novel Method to Predict the Real Operation of Ferrite Inductors With Moderate Saturation in Switching Power Supply Applications

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.

A Critical Investigation of Coupled Inductors SEPIC Design Issues

This paper discusses design issues of single-ended primary-inductor converter (SEPIC) with coupled inductors (CIs). The main investigation is focused on the correlation existing among the size of coupling capacitor, the magnetic coupling factor of CIs, the voltage conversion ratio, and the amplitude of peak-to-peak (pk-pk) ripple current in the input and output ports of the CIs. It is shown how the above elements must be properly correlated to prevent large input and output ripple currents, particularly if tightly coupled inductors are used. Analytical design formulas for the coupling capacitor are applied to the design of a low-power SEPIC. Simulations and experimental measurements prove the validity of the model predictions and the reliability of related design rules.

A Versatile Method for MOSFET Commutation Analysis in Switching Power Converter Design

This paper discusses a novel method for the analysis of MOSFET commutations and the investigation of related losses and spike current issues in the switching power converter (SPC) design. The synchronous rectification switching cell (SRSC) configuration is considered for the investigation, which is used in the high-frequency high-efficiency (H 2EF) SPC design. The proposed method is aimed at providing an effective tool for quick feasibility investigations and comparative evaluations among design solutions using different MOSFET combinations for the design of H 2EF SPCs. The method allows us to use nonlinear models of interelectrode MOSFET capacitances and adopts a novel numerical technique specifically developed to solve the SRSC model ensuring robust and fast simulations. Capacitive pulsating currents circulating through the MOSFETs and the SPC during commutations can be analyzed in detail by using the proposed method. Different examples are discussed to show how MOSFETs characteristics and operating conditions may affect switching losses, because of the pulsing currents circulation through the SPC.

Identification of ferrite core inductors parameters by evolutionary algorithms

This paper discusses the identification of Ferrite Core (FC) power inductors parameters in the real operating conditions relevant to Switch-Mode Power Supplies starting from experimental measurements. A novel method for parameters identification is proposed, based on Evolutionary Algorithms (EAs) and on the analysis of inductors non-linear behavior. Two EAs, the Genetic Algorithm and the Differential Evolution, are investigated and compared. The results of the proposed method are experimentally validated by means of a buck converter evaluation board.

Validation of inductors sustainable-saturation-operation in switching power supplies design

This paper discusses a novel method to validate Sustainable Saturation Operation (SSO) of ferrite inductors in switching power supplies design. SSO is achieved when an inductor operates in partial saturation, with ripple current, power losses and temperature rise fulfilling reliability and efficiency requirements. Achieving inductors SSO permits to reduce the size of power supplies. The method presented in this paper allows the SSO validation of inductors complying with the power supply specifications. A buck converter with Vin= 36V, Vout = 12 V, fs = 450kHz, Iout = [4, 5]A is adopted as reference case study to provide validation to the proposed approach.

A generalized numerical method for ferrite inductors analysis in high current ripple operation

Abstract Ferrite Core Power Inductors (FCPIs) operation in partial saturation offers unexplored opportunities in reducing the size of magnetic parts and the power losses in Switching Mode Power Supplies (SMPSs). This paper presents an enhanced numerical method to achieve a reliable prediction of the current ripple of FCPIs, also in partial saturation, for different conversion topologies and in whatever operating conditions. The proposed analysis includes High-Current Ripple (HCR) operations, for synchronous configurations in Continuous Conduction Mode (CCM) and for diode rectification configurations in Discontinues Conduction Mode (DCM). Relevant numerical algorithms for the reliable FCPIs current wave-shape prediction are given. Experimental verifications are performed on two boost converters in CCM and DCM to provide the validation of the proposed method.

Power vs efficiency analysis in high-frequency wireless power transfer systems — Part II: Applications

This paper presents examples of application of the model for High-Frequency Wireless Power Transfer Systems (WPTSs) introduced and discussed in the companion paper Part I. The impact of MOSFETs losses and mismatches of resonant elements and coupling factor is discussed in this paper. Results of the analysis realized on a 2W@6.78MHz WPTS are presented and valldated by means of experimental measurements.

Differential evolution algorithm-based identification of Ferrite Core Inductors saturation curves

Identification of saturation curves of Ferrite Core Inductors (FCIs) based on Differential Evolution Algorithms Processing of Experimental Measurements (DE-EMP) is discussed in this paper. It is shown that the DE-EMP approach provides more realistic data for the prediction of the peak-to-peak ripple current of FCIs compared with the information provided by manufacturers. An experimental validation of the proposed method is presented in the paper, relevant to a step-down dc-dc power converter application.

An improved algorithm for the analysis of partially saturated ferrite inductors in switching power supplies

Ferrite inductors operation in partial saturation offers unexplored opportunities in reducing the size of magnetic parts and the power losses in High-Current-Ripple Switching Mode Power Supplies (HCR SMPSs) using SiC and GaN devices. A reliable prediction of the inductor current ripple is required to exploit such opportunities. A new method for ripple analysis of saturated inductors has been recently proposed, allowing the investigation of effective SMPS design solutions with minimum size inductors. An extension of such method is herein presented, allowing design investigations for the reliable use of partially saturated ferrite inductors in HCR SMPS applications. Simulation results and experimental tests fully validate the proposed method.