Sigma-delta modulation of multi-phase high frequency converters

A power conversion control architecture is proposed that merges advanced digital modulation techniques, high frequency resonant converters, and multi-phase converters. If a converter´s switching frequency is high enough, the converter may be turned on and off quickly to modulate power flow. The proposed system is composed of several high frequency converters connected in parallel, only a few of which are active at a given time to regulate the output voltage. The number of active converters is determined through a sigma-delta modulation process. The specific converter enable signals are generated by a balancing algorithm that ensures approximately equal effective duty ratio and switching frequency for all phases. An output voltage regulator, here implemented as a PI loop, completes the system. The method has been simulated for an eight-phase closed-loop system. Experimental results are shown for a four-phase open-loop system with an external command that corresponds to the effective duty ratio of the power converters.