EMI Reduction in Switching Power Converter by Using Chaotic Frequency Modulation Technique

Abstract In Conventional power converters electromagnetic interference (EMI) emissions comes from the switching of a DC voltage in pulse width modulation (PWM) process. The effective way to reduce EMI in power converter is to use frequency modulation technique which modulates the originally constant switching frequency by following a certain modulation profile (i.e. sinusoidal, sawtooth, triangular, exponential, random, chaotic).This paper is dedicated to chaotic switching frequency modulation technique which is the modified form of simple frequency modulation technique and also focusing on the effectiveness of simple frequency modulation in EMI reduction as a function of the different switching modulation profiles. The simulation results show that the EMI spectrum is decided completely by the peak amplitude of PWM spectrum. Chaotic frequency modulation technique is effectively reduce it by using a variable switching frequency (modulating a base value (carrier frequency, fc)) obtained by logistic map(bifurcation technique). And also compare chaotic frequency modulation with all other different modulating profile and finally conclude that chaotic frequency-spreading gives better spectral performances and results

A Facile Synthesis and Studies of Some New Chalcones and Their Derivatives Based on Heterocyclic Ring

Chalcones (6a-f) have been prepared by the condensation of ketone (5) and different aromatic and heterocyclic aldehydes. These chalcones (6a-f) on treatment with guanidine hydrochloride and phenyl hydrazine hydrochloride in presence of alkali give aminopyrimidines (7a-f) and phenylpyrazolines (8a-f) respectively. All the newly synthesized compounds have been characterized on the basis of IR, 1HNMR spectral data as well as physical data. Antibacterial activity (minimum inhibitory concentration MIC) against Gram-positive S. aureus MTCC 96 and S. pyogeneus MTCC 442 and Gram-negative P. aeruginosa MTCC 1688 and E. coli MTCC 443 bacteria, as well as antifungal acivities (MIC) against C. albicans MTCC 227, A. niger MTCC 282 and A. clavatus MTCC 1323 were determined by broth dilution method