Harmonic analysis of nondeterministic switching methods for DC-DC power converters

The authors present a rigorous theoretical harmonic analysis of random puls e width modulation (RPWM) method and random pulse position modulation (RPPM ) method for de-de converters. The theoretical relationships of discrete ha rmonics, continuous noise and output voltage ripple of the RPWM and RPPM sc hemes are established and compared with those of a standard deterministic P WM scheme in a buck converter. Limitations in the randomly switched de-de c onverters are highlighted. The theoretical predictions indicate that the ra ndomized schemes generally have an inherent problem in achieving low output voltage ripple due to the low-frequency continuous noise within the pass-b and of the converter filter. For dc-dc power conversion, the RPPM method of fers much better output voltage performance than the RPWM method.