G. Di Capua

Transformer Design for Isolated Switching Converters Based on Geometric Form Factors of Magnetic Cores

This paper discusses issues related to the transformer design for switch-mode power supplies based on the use of geometric form factors (GFFs) of magnetic cores. It is shown that GFFs allow a straightforward and reliable transformer design complying with loss and size constraints. It is also proved that inherent assumptions underlying the application of previous design methods based on some geometric constants can be penalizing if the effects of specific combinations of GFFs of magnetic cores are not properly considered. Examples regarding the design of transformers for forward converters are presented and discussed.

A losses-based analysis for electric vehicle wireless chargers

Contactless charging systems are becoming the most convenient and safest way to refill Electric Vehicles (EVs) batteries. Wireless Power Transfer (WPT) has been successfully adopted in EVs high power applications to efficiently deliver energy over a relatively large air gap. In order to predict the realistic performance of an EV wireless charger, the impact of real components tolerances and semiconductor devices losses must be considered. In this paper, a model for the analysis of the influence of semiconductor devices losses and of resonant devices parameters uncertainty is discussed. The model is validated through PSIM simulations of a 3.7kW/85kHz WPT system.

Models and methods for energy productivity analysis of PV systems

This paper discusses models and methods for the analysis of PV systems with Distributed Maximum Power Point Tracking (DMPPT). An Energy Productivity Analysis Algorithm (EPAA) is discussed, integrating models and algorithms from component level to system level, allowing the analysis of PV systems operating in partial shading and electrical mismatched conditions. The EPAA provides realistic assessment of the energy productivity including the effects of PV panels characteristics, of shadows and of the MPPT converters. A comparative evaluation of boost-based vs buck-boost-based DMPPT solutions is presented in the paper, highlighting how the energy productivity of DMPPT PV systems is influenced by the parameters of real components.

Geometric-constants-based design of transformers for isolated switching converters

This paper discusses issues related to the design method of transformers for switching converters based on the use of the geometric constant Kgfe of magnetic cores. It is shown that some inherent assumptions in the application of the method can be misleading if the effects of specific combinations of geometric measures and thermal properties of the magnetic cores are not properly considered. An example regarding the design of the transformer for a low-power multi-output isolated dc-dc forward converter is presented and discussed.

A Numerical method for ZVS investigation in isolated converters

The effect of the parasitic paramete transformer and MOSFETs and their impa behavior and efficiency in ZVS isolated co effectively investigated by using the numerical m in this paper. This method helps in the valid achievement of the ZVS operation. A Low-Side Clamp converter is discussed as a case stud results prove the effectiveness of the proposed n in commutations analysis.

Ferrite inductor models for switch-mode power supplies analysis and design

This paper discusses some models useful to analyze ferrite inductors operating in partial saturation in Switch-Mode Power Supplies (SMPSs). Inductance vs current curves are needed to assess if the level of saturation is sustainable for the inductor, in order to achieve SMPS volume reduction. The models discussed in the paper are generated from experimental voltage and current waveforms of the inductor in SMPSs. Two dual approaches are presented, based on the local and global characterization of the inductor under small- and large-amplitude current ripple conditions. The resulting curves provide inductor current prediction in agreement with experimental data.

Photocatalytic reactor with multiphase digital control of luminous radiation

This paper investigates the effect of controlled periodic illumination by visible LEDs on the performances of a visible-light-active N-doped TiO2 photocatalyst (N — TiO2) immobilized on glass spheres for wastewater treatment, using Methylene Blue (MB) dye as a model pollutant. Different LED dimming techniques are investigated and compared, including a classical Pulse Width Modulation (PWM) technique and a novel proposed Variable-Peak PWM technique. A modulation of dimming duty-cycle is adopted as well, which allows to control the light irradiation in a new way with respect to previously used methods. Experimental results highlight the improvement in MB photocatalytic degradation process obtained by using the proposed modulation techniques.

Enhanced performances of a photocatalytic reactor for wastewater treatment using controlled modulation of LEDs light

One of the main limitations related to the industrial utilization of a photocatalytic process is the use of UV lamps that have several disadvantages such as the low quantum efficiency (QE). One of the approaches to increase the QE consists in the use of controlled periodic illumination (CPI). In this regard, Light Emitting Diodes (LEDs) are the best choice as light sources, since they can be electronically controlled by using LED dimming techniques, allowing variable turn-on and turn-off times on a microsecond time-scale. The aim of this work is to investigate the influence of controlled modulation of LEDs light on the performances of a photocatalytic reactor for wastewater treatment using TiO2 immobilized on glass spheres (TiO2/GS). The experiments were realized with a pyrex cylindrical batch photoreactor irradiated by three power UV-LEDs and placed surrounding the external body of the cylindrical photoreactor. The system adopted for the controlled modulation of LEDs light is composed by a photovoltaic panel (PV), a dc–dc converter dedicated to the maximum power point tracking of the PV panel and a dc–dc converter dedicated to drive the UV LEDs. A system controller is also included, whose goal is to ensure matching between the maximum available PV power, the LED power and the resulting low-frequency LEDs dimming modulation. The experimental results showed that the use of certain types of duty-cycle dimming modulation waveforms, including periodic and non-periodic waveforms and combinations of them, have been discovered to improve the photo-catalytic reactor performances. In particular, the use of a modulation of LEDs dimming like sinusoidal and pseudo-sinusoidal waveforms is more effective than the fixed dimming. The best results in terms of methylene blue degradation (about 25% in less than 1 h) have been achieved with a pseudo- sinusoidal waveform.

Analysis and characterization of power MOSFETs for power converters energy&reliability-aware-design

This paper discusses the impact of Power MOSFETs (PMs) Capacitance-Voltage (C-V) characteristics on switching losses in power converters. A fast and robustly convergent numerical technique is adopted to analyze the sensitivity of PMs power losses with respect to their C-V shapes. Such technique helps both in identifying desirable specifications for PMs design, and in achieving appropriate selection of PMs for power converters energy&reliability aware design. The results presented in this paper, concerning loss analysis and experimental verification for a 85V to 170V@0.5A dc-dc boost converter, highlight the PMs C-V curves impact and the valuable support of the proposed technique in PMs design.

Stability limit analysis for peak-current-controlled Ćuk converter

The goal of this paper is to derive the analytical stability boundaries for Ćuk converter and to highlight the joint impact of power stage passive components and current controller characteristics on the converter stability. Stability conditions are determined by means of a novel dynamic model of the Peak Current Controlled (PCC) Ćuk converter, taking into account the difference between the small signal ac components of the voltage across coupling capacitor and of the sum of input and output voltage. A reduced-order small model of PCC Ćuk converter is proposed.