Switched mode power supplies are significant generator of harmonics and electromagnetic noise .This has always been a serious concern, as it adversely affects the operation of the system. In this paper, the effectiveness of softswitching in reducing harmonic noise is first investigated. Then external chaos is added to the soft switching and the combined effect in suppressing the harmonic noise and EMI is investigated. DC-DC buck converter is taken as case study and the comparative evaluation has been made using spectral analysis. Simulations are carried out for hard switching and soft switching techniques, with external chaos generator included, using Matlab. Results confirm that, compared with the conventional hard switching method with chaos modulation, the soft switching technique with chaos modulation substantially reduces the EMI in the power converter. The simulated results are compared with the experimental counterparts to verify the validity of the approach.
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