Spectral Analysis of Randomized Switching Frequency Modulation Scheme with a Triangular Distribution for DC-DC Converters

Randomized modulation schemes are often employed in DC-DC converters to reduce the magnitude of discrete harmonics in the output spectrum. One of these schemes is Randomized Switching Frequency modulation (RSFM) that completely eliminates the discrete harmonics by randomizing its switching period (switching frequency) to follow a uniform distribution. In this paper, we investigate RSFM with its switching period following a triangular distribution. We show that RSFM with a triangular distribution is as effective as RSFM with a uniform distribution in eliminating the discrete harmonics, and has a slightly better (1 dB) reduction in the peak spectral power of a standard modulation scheme and a better (~2.5 dB) ripple noise voltage (at 12 V to 5 V conversion and 10 microseconds average switching period).