Output ripple reduction of an automotive multi-phase bi-directional dc-dc converter

Abstract

Bi-directional dc-dc converters for automotive applications typically are limited to generate only a small voltage ripple, especially when a ultra-capacitor with a limited ripple current capability is interfaced by the converter. Thus, to minimize the ripple quantities and the converter volume at the same time, interleaved multi-phase dc-dc converters are utilized. However, tolerances of the buck+boost inductors of the interleaved phases generate sub-harmonics in the ripple spectrum that are counterproductive to the advantage of ripple reduction. A method to cancel the fundamental frequency of the voltage ripple is proposed that is applicable to a converter consisting of three or more phases. It is shown that even for a low phase count the overall ripple amplitude is greatly reduced, only by adjustment of the phase shift angles. Experimental results carried out with a three-phase interleaved bi-directional dc-dc converter proof the concept functionality.