Analysis of output voltage of switching frequency modulated DC-DC converter operating in discontinuous conduction mode

In this paper analysis of output voltage ripples of a switching frequency modulated (SFM) buck converter operating in discontinuous conduction mode (DCM) is performed. The ripples are analyzed in both time and frequency domains by the use of theoretical derivations and computer simulations. Significant increase in output voltage ripples under DCM is observed after using periodic SFM. Low frequency variations at modulation frequency are considered as the most problematic. Cause of the problem is revealed. Influence of main nonidealities of the converter and modulation parameters on the output voltage ripples is analyzed. Experimental verification is also performed to confirm the theoretical evaluations and simulation results. The analysis can give useful information when designing a SFM power converter.