Improving effectiveness of the use of frequency modulation in power converters

In the research the examination of the methods possible to improve the implementation of spread spectrum technique for EMI reduction in switch mode power supplies are searched. The analysis of effects of switching frequency modulation in open loop boost converter reveals that there is additional undesirable amplitude modulation of the input current of the converter. This effect distorted the spectrum of the input current, thus worsening the EMI reduction, achieved by the use of the frequency modulation. Experimental results, using sinusoidal and sawtooth modulating signals, proved the theoretical assumption, asserting that the effectiveness of EMI attenuation and the reduction of spectral asymmetry could be achieved choosing as high as possible operating frequencies and proper modulating profiles.