Analysis of the noise and efficiency characteristics in a quasi-resonant converter
A quasi-resonant converter using flyback topology can realize soft switching with relatively simple circuit. However, a switching device with high withstand voltage is necessary to achieve complete zero voltage switching when the input voltage is high and it causes decrease of efficiency because a switching device with high withstand voltage has relatively high on voltage. Therefore, we analyzed efficiency and noise of a quasi-resonant converter with a low breakdown voltage and low on voltage switching device under the condition of non-zero voltage switching. As a result of the analysis, it is found that high efficiency and low noise are achieved with non-zero voltage switching.
An adaptive blanking time control scheme for audible noise free quasi resonant Flyback converter
The quasi resonant (QR) control scheme is widely adopted in Flyback converter to maximize its efficiency by reducing the switching loss. However, the maximum frequency limitation adopted in QR control may cause the audible noise due to the frequency hopping phenomena at certain load and input condition, which is related to the intrinsic output characteristic of the control scheme. This paper presents a simple solution to eliminate the frequency hopping in the QR Flyback using an adaptive blanking time circuit. The proposed method changes the blanking time automatically to keep the output characteristic smoothly which eliminate the audible noise in the transformer. The detailed operation principle and design considerations are presented. The experimental results from a 16V/4A prototype are provided to validate the effectiveness of the proposed solution.
Effect of active compounds on structure and biochemistry of T . rubrum 4 . 1
The field of nanotechnology is one of the most active research areas in modern materials science. Nanoparticles exhibit new or improved properties based on specific characteristics such as size, distribution and morphology. There have been impressive developments in the field of nanotechnology in the recent past years, with numerous methodologies developed to synthesize nanoparticles of particular shape and size depending on specific requirements. New applications of nanoparticles and nanomaterials are increasing rapidly. Nanotechnology can be termed as the synthesis, characterization, exploration and application of nanosized (1100nm) materials for the development of science. It deals with the materials whose structures exhibit significantly novel and improved physical, chemical, and biological properties, phenomena, and functionality due to their nano scaled size. Because of their size, nanoparticles have a larger surface area than macro-sized materials. The intrinsic properties of metal nanoparticles are mainly determined by size, shape, composition, crystalline and morphology. Nanoparticles, because of their small size, have distinct properties compared to the bulk form of the same material, thus offering many new developments in the fields of biosensors, biomedicine, and bio nanotechnology. Nanotechnology is also being utilized in medicine for diagnosis, therapeutic drug delivery and the development of treatments for many diseases and disorders. Nanotechnology is an enormously powerful technology, which holds a huge promise for the design and development of many types of novel products with its potential medical applications on early disease detection, treatment, and prevention.