Acquisition efficiency of Flavescence dorée phytoplasma by Scaphoideus titanus Ball from infected tolerant or susceptible grapevine cultivars or experimental host plants

The rate of Flavescence dorée phytoplasma (FDP) acquisition by the leafhopper vector Scaphoideus titanus Ball was tested under field and glass house conditions confining healthy reared nymphs on canes of FDP-infected grapevines or on FDP-infected cuttings collected in the field during the dormant season. Acquisition tests were performed using FD-tolerant (Merlot) or highly susceptible (Pinot blanc) grapevine cultivars, or alternatively using experimentally infected broadbean plants. Frequency of FDP acquisition by leafhoppers was evaluated using a polymerase chain reaction (PCR) assay. Different batches of insects were confined on the same infected source plants in the vineyard for acquisition access periods (AAP) of 7 d at a time at intervals of 15-20 d during spring and summer. When diseased Pinot blanc grapevines were used as source plants, acquisition by leafhoppers and transmission to healthy grapevines increased over summer, while almost no acquisition or transmission was observed when diseased Merlot grapevines were used as source plants. Tests conducted under controlled conditions confirmed that Merlot is a poorer source of FDP than Pinot blanc; the optimum FDP source for S. titanus was broadbean although this plant is not a natural host of the leafhopper. It is assumed that grapevine cultivars play an important role in influencing the proportion of FDP-infected leafhoppers in the vineyards and therefore influencing the rate of disease progress.

The Asymmetrical Half-Bridge Flyback Converter: A Reexamination

Isolated Zero-Voltage-Switching (ZVS) dc-dc converter topologies are attractive solutions in the continuous ride toward higher switching frequencies, allowing more compact power supplies. Among them, the Asymmetrical Half-Bridge Flyback Converter (AHBFC) represents an interesting solution, featuring a simple duty-cycle control at a constant switching frequency, as opposed to the popular LLC converter. The majority of the papers dealing with this topology, present an approximated voltage gain which is similar to an isolated Buck converter, i.e. proportional to the duty-cycle. However, when the converter is designed for a resonant operation, so as to eliminate any reverse recovery problem of the rectifier diode, its voltage gain can be quite different, becoming non monotonic and a function of the switching frequency. This paper investigates this aspect, deriving a theoretical framework capable of capturing its real voltage gain behavior. The proposed analytical model has been verified through simulations as well as experimental measurements taken on a 160W prototype working at 400kHz

Line-frequency commutated rectifier complying with IEC 1000-3-2 standards

Consumer and household appliances require cheap ac/dc power supplies complying with EMC standards. The commonly employed passive solutions are bulky and do not provide output voltage stabilization. Active solutions, based on PFC's with high-frequency switching, provide compactness and regulation capability, but are generally expensive due to the need for fast-recovery diodes and complex EMI filters. This paper presents a high power factor rectifier, based on a modified conventional rectifier with passive L-C filter, which improves both the harmonic content of the input current and the power factor, by means of a low frequency commutated switch and a small line-frequency transformer, and allows to comply with IEC 1000-3-2 standard with reduced overall inductive components' volume

Conducted EMI issues in a Boost PFC design

The paper presents the results of an experimental activity concerned with the development of a 600 W Boost Power Factor Corrector (PFC) complying with the EMC standards for conducted EMI in the 150 kHz-30 MHz range. In order to accomplish this task, different circuit design and layout solutions are taken into account and their effect on the conducted EMI behavior of the converter is experimentally evaluated. Common-mode and differential-mode switching noise, together with input filters' design and topology and with the PCB layout (in terms of track length and spacing, ground and shielding planes etc.) are the key aspects which have been analyzed. In particular, the paper reports the conducted EMI measurements for different filter capacitor placements and values, for different power switch drive circuits together with several other provisions which have turned out to be decisive in the reduction of the generated EMI

Low-loss high-power-factor flyback rectifier suitable for smart power integration

A low-loss, high-power-factor flyback rectifier is presented, which is designed as a possible application for a new type of smart power integrated circuit. This is going to be manufactured by ST Microelectronics using the VIPower M3 technology and will include on the same silicon chip both control circuitry and an emitter switching power device. In order to avoid dangerous interactions between power and control part of the integrated circuit, it is necessary to control the rate of change of the power device voltage at turn-off. Accordingly, a lossless passive snubber was added to the conventional converter topology. The snubber also limits the voltage spikes across the power device, due to the transformer leakage inductance, and reduces the electromagnetic noise generation. A modified non-linear carrier control is considered which, thanks to the integration of the switch current signal, ensures high power factor and inherent noise immunity together with a simple control implementation (no need of input voltage sensing, multiplier and current error amplifier). A 200 W converter prototype was tested in order to evaluate the achievable performance

Modeling and Control Design of the Six-Phase Interleaved Double Dual Boost Converter

This paper presents the small-signal modeling and the control design of the six-phase Interleaved Double Dual Boost, which is a non-insulated, step-up DC-DC converter that can be operated with high voltage gain and can be scaled to high-power applications. The applications of this converter include electrical vehicles and renewable energy conversion. Experimental results obtained with a prototype operating with input voltage of 60V and output voltage of 360V and with nominal output power of 2.2kW are presented