A comparison of nondeterministic and deterministic switchingmethods for DC-DC power converters

摘要

An analysis and experimental results of the random pulsewidthnmodulation (RPWM) and random pulse-position modulation (RPPM) methodsnfor DC-DC converters are presented. The characteristics and performancenof power converters under two randomized modulations are evaluated. Thentheoretical relationships of discrete harmonics, continuous noise, andnoutput-voltage ripple of the RPWM and RPPM schemes are established andncompared with those of a standard deterministic pulsewidth modulationn(PWM) scheme in a buck converter. Limitations in the randomly switchednDC-DC converters, which have not been addressed before, are highlighted.nRandomized schemes generally have inherent problems in achievingnlow-output-voltage ripple due to the low-frequency continuous noisenwithin the passband of the converter filter. The inherent low-frequencynnoise-induced voltage ripple problems of nondeterministic switchingnmethods for DC converters are confirmed experimentally. The performancenof the RPPM method is found to be closer to the standard PWM method thannthat of the RPWM method. For DC-DC power conversion, the RPPM methodnoffers much better output-voltage performance than the RPWM method