2,369 research outputs found
An integrated single-stage quasi-resonant power factor correction converter with active clamp circuit
No full textA new integrated single-stage zero current switched (ZCS) quasi-resonant converter (QRC) for the power factor correction (PFC) converter is introduced in this paper. The power factor correction can be achieved by the discontinuous conduction mode(DCM) operation of an input current. The proposed converter has the characteristics of the good power factor, low line current harmonics, and tight output regulation. Furthermore, the ringing effect due to the output capacitance of the main switch can be eliminated by use of active clamp circuit. A prototype converter has been designed and experimented based on design equations. The line current waveform of the prototype shows about 15% of total harmonic distortion at rated condition. Also, the efficiency and the power factor can be obtained about 87% and 0.985, respectively, at rated condition. The proposed converter is suitable for a low power level applications with a tightly regulated output voltage and a high switching frequency
Design of a power-factor-correction converter based on half-bridge topology
No full textA single-stage ac/dc converter based on a half-bridge topology suitable for low-power-level applications is proposed. The proposed converter has high power factor, low harmonic distortion, and tight output regulations. An asymmetrical control and synchronous rectification are employed to reduce the switching and rectification losses, respectively. The modeling and detailed analysis are performed to derive the design equations. Based on these design equations, a prototype converter has been designed and tested by experiment. This prototype meets the IEC 61000-3-2 regulations with near-unity power factor and high efficiency
Design of High Quality AC/DC Converter with High Efficiency Based on Half Bridge Topology
No full textpH shock induces overexpression of regulatory and biosynthetic genes for actinorhodin production and enhances central metabolixm in Streptomyces coelicolor A3(2)
No full textMicrostructure control in two-phase Al-21Ti-23Cr alloy
No full textTo improve the mechanical properties of the Al-21Ti-23Cr two-phase alloy consisting of L1(2) matrix and 20 vol% Cr2Al as a second phase, microstructure control was conducted through the aging treatment as a thermal process and the addition of V and Zr as conventional alloying. It was found that TiAlCr was precipitated as a third phase in the L1(2) matrix by the aging treatment at 800 and 1000 degrees C, and its size was smaller at 800 degrees C than at 1000 degrees C. The yield strength of the aged alloy increased rapidly only at 800 degrees C although the third phase was precipitated at both 800 and 1000 degrees C. In the V-added two-phase alloys, the yield strength and the strain increased simultaneously when V was added up to 3 at%, which is attributable to the improvement in the ductility of Cr2Al. Microstructure control conducted in this study suggests the possibility of improving the mechanical properties of Lit (Al,Cr)(3)Ti-based two-phase alloy by precipitating the fine third phase in the Lit matrix and enhancing the ductility of the second phase. (C) 2000 Elsevier Science Ltd. All rights reserved
IGBT-based cost-effective energy-recovery circuit for plasma display panel
No full textA new insulated-gate-bipolar-transistor (IGBT)based cost-effective energy-recovery circuit (ERC) for a plasma display panel (PDP) is proposed. Since it is composed of two small resonant inductors and four power diodes instead of the conventional large auxiliary circuit, it features a simpler structure, less mass, fewer power devices, higher efficiency, and lower cost. Since all its power switches are turned off under the zero-current switching operation, IGBTs can be employed as power switches. Moreover, the very stable,and uniform light emitted from a PDP proves the high quality of screen. Therefore, it is well suitable for the consumer-affordable hang-on-the-wall TVs which have the desirable features such as thinness, lightness, high efficiency, low price, etc. To confirm the validity of the proposed ERC, a comparative analysis and experimental results based on a whole ac PDP driver equipped with the proposed circuit for the 42-in PDP are presented
Integrated ZCS quasi-resonant single-stage high power factor converter
No full textA new single phase zero-current-switched (ZCS) single stage quasi-resonant converter (QRC) for power factor correction (PFC) is proposed. The converter provides a good power factor, has tight output regulation, and low line current harmonic distortion. The proposed converter is suitable for low power level power supplies with high efficiency and tightly regulated output voltage
Pyrolytic conversion of spherical organo-silica powder to silicon nitride under nitrogen
No full textMonodisperse, spherical Si3N4 powder composed of fine particulates was synthesized by pyrolyzing spherical organo-silica powder under nitrogen. The organo-silica powder was prepared by hydrolyzing a mixture of phenyltrimethoxysilane (PTMS) and tetraethoxysilane (TEOS) in a methanol solution of mater and ammonia, The organo-silica powder consisted of 81.3 at.% silicon units derived from PTMS and 18.7 at.% silicon units derived from TEOS, During the pyrolysis under nitrogen, the organo-silica powder decomposed to a mixture of free carbon and silica, with an increase of the surface area, at 500 degrees-600 degrees C, followed by the formation of alpha-Si3N4, with beta-Si3N4 as a minor phase, ai: 1450 degrees and 1500 degrees C and beta-SiC at 1550 degrees C. The pyrolyzed powders, which retained the spherical shape and monodispersity of the organo-silica powders, with a reduction in mean particle diameter, were composed of fine particulates that were similar to 40 mm in size
- …
