The effectiveness of random-switching control, by which the switching-noise spectrum is spread and its level is reduced, is briefly described through experimental results. The noise spectrum by random switching is analyzed in general approach including a noise-generation model and a switching function with random process. Taking the normal distribution as an instance, the discussion on the amount of random perturbation is made quantitatively. The validity of the analysis is confirmed experimentally by a series of pulse serving as ideal switching-noise.

The low-frequency output noise that is caused by introducing random-switching control into DC-to-DC converters with output regulation, is discussed quantitatively. A modified converter model involving the unintended effect of random switching is derived from the consideration of noise-generation mechanism. After the theoretical analysis based on the model, it is clarified that the magnitude of output noise is in proportion to the variance of switching interval. The experimental results of a buck-type converter are compared with those obtained theoretically, so that the validity of the theoretical results is confirmed experimentally.