Vignan University

About: Vignan University is a education organization based out in Guntur, Andhra Pradesh, India. It is known for research contribution in the topics: Control theory & CMOS. The organization has 1138 authors who have published 1381 publications receiving 7798 citations.

A computational approach on engineering short spacer for carbazole-based dyes for dye-sensitized solar cells

Abstract: Donor-π-linker-acceptor (D-π-A) push–pull dye molecules are most common in dye-sensitized solar cells (DSSCs) applications. Selection of dye molecules for DSSCs is based on their ability to absorb light in the visible spectrum. This can be done more efficiently by positioning the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) with respect to the conduction band of the semiconductor and the redox potential of the electrolyte, respectively. The photocurrent is manipulated by the extent of light absorption, planarity of the π-linker for efficient intramolecular charge transfer (ICT), oxidized dye reorganization energy (Λ) and dye regeneration driving force (ΔGreg). In a quest of achieving panchromatic absorption up to near-IR region, mostly electron-rich chromophores and their oligo form were used in the π-segment, but this approach led to poor ICT. In this computational analysis, we have explored the effect of electron-withdrawing (cyano (–CN)) and donating groups (methoxy (-OMe)) in three different π-segment length to understand the carbazole dyes’ suitability for DSSCs using onset wavelength (λonset), Λ, ICT and ΔGreg as the figure-of-merits.

Analysis and design of non-isolated single phase AC/DC PFC topologies to drive LEDs

Abstract: This paper presents a detailed analysis of several topologies of single stage AC/DC non isolated converters used as a power supplies for driving LEDs High power factor and regulated voltage is achieved with these topologies These converters are designed with 230V AC input, 48V DC output for 200W load at switching frequency of 20KHZ Implementation and comparison of topologies are done on MATLAB/SIMULINK software

Transformer design to achieve soft switching in low power Flyback converters

Abstract: Soft switching in DC-DC converters is a well accepted technique and its advantages are widely discussed. Undoubtedly, the soft switching reduces the power loss in the Main switch while improving the overall EMI in the converters. This facilitates the increase of switching frequency of converters. This paper highlights a design methodology for the transformer in a fly back converter, which automatically accomplishes the complete soft switching of the main switch. No extra circuit or the control scheme is needed to attain Zero Current Turn On and total Zero Voltage Switching (both during turn ON and Turn OFF) of the Main MOSFET switch. Also, it eliminates the Dissipative snubber which is an essential component in fly back converter. However, this scheme is wholly applicable to fixed Input and constant load applications. Nevertheless, most of the Industry scenarios are similar at low power range of about 50 to 100 watts, because invariably the DC-DC converters are operated from a Power factor correction module (Whose output is fairly regulated to around 400V DC) and the output load is constant. The design concept is demonstrated on a 60 watt fly back converter operating from a 400V DC bus and operated at 100 KHz.