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 fast-response sliding-mode controller for quadratic buck converter

Abstract: The switched-mode power supplies are widely used in very low voltage and high-power applications where large conversion ratios are required. In such cases, the quadratic buck converter is the suitable one compared to buck, cascaded buck and multi-phase choppers, because of their limitations in switching frequency and losses. This paper presents mathematical analysis, design and simulation of a quadratic buck converter using fixed frequency Pulse-Width Modulation (PWM)-based Sliding-Mode (SM) controller in order to obtain fast dynamic performance. The design aspects include choice of sliding surface, deriving existing and stability conditions, control parameter selection and their analysis. The performance of the proposed converter is compared with the conventional Average Current-Mode (ACM) controller. In average current mode, the tuning of the PI controller for the inner current loop and outer voltage loop is done using bode plots. The simulation results for the two types of controllers are represented for analysing dynamic performance, as well as line and load regulations.

Influence of (La, Cu) Doping on the Room Temperature Multiferroic Properties of BiFeO3 Ceramics

Abstract: A series of Bi1-x La x Fe0.98Cu0.02O3 (x = 0.01, 0.03 and 0.05) ceramics were synthesized by sol–gel method. The prepared ceramics were characterized by X-ray diffractometer (XRD), vibrating sample magnetometer (VSM) and dielectric measurement. XRD patterns reveal that Bi1-x La x Fe0.98Cu0.02O3 (x = 0.01, 0.03 and 0.05) ceramics crystallize in single-phase rhombohedral structure with R3c space group without distortion, and the average crystallite size was in the range of 31–92 nm. VSM exhibited a weak ferromagnetism for La- and Cu-co-doped BiFeO3 ceramics. The squareness ratio of the hysteresis loop decreases as La concentration increases in Bi1-x La x Fe0.98Cu0.02O3. However, these materials show improved dielectric properties compared to undoped BiFeO3 ceramic.

Dielectric analysis of polypropylene (PP) and polylactic acid (PLA) blends reinforced with halloysite nanotubes

Abstract: Polypropylene (PP) and polylactic acid were blended in the ratio 80:20 by weight and compatibilized with 3 wt% of maleic anhydride-grafted-PP. The compatibilized blend was chosen as the base matrix...