Fpga based electromagnetic interference reduction using various randomization techniques

Abstract

The DC-DC switched-mode converters are the power electronics newlinecircuits most widely used due to its high output voltage and conversion newlineefficiency. These devices are designed in such a way to regulate the output newlinevoltage according to the change in input voltage and load current so that it gives newlinebest performance under any operating conditions. Basically the switched mode newlinepower converters generate differential and common mode conduction noise, in newlineaddition to radiated noise. This noise produces serious troubles by generating newlinesuch switching noise. As this converter already produces a considerable amount newlineof switching noise, these make more essential to operate this converters inside newlineElectromagnetic Interference (EMI) perceptive applications. To overcome such newlineproblems it is very essential to discover various noise reduction techniques. newlineThe pulse width modulation is the common technique most familiarly used for newlinecontrolling the output voltage. It maintains variable duty cycle with a constant newlineswitching frequency. But the disadvantage is PWM causes specious amount of newlineharmonic noise results in EMI. newlineTo overcome this issue a randomly switched controllers is newlinedesigned for varying the switching frequency there by reducing the noise. newlineThis spread-spectrum techniques change the switching noise from a train of newlinelarge spikes and its harmonics to a smoother continuous spectrum. In this newlinetechnique the broadband noise is been reduced, but still the low frequency noise newlineincreased due to raise in randomized switching frequency beyond a certain limit. newlineThis low frequency noise will overlaps the neighbouring frequency spectrum; to newlineavoid this randomization range should be taken less than ± one-third of the newlinecentral switching frequency. Sigma Delta modulation proposes another newlinemodulation scheme of reducing conducted EMI within FCC limits. This method newlineis similar to the programmed/randomized PWM schemes in that it attempts to newlinedisperse the spectrum over a continuous range of frequencies. Sigma delta newlinemodulations are a used in high-resolution applications.