Digital control strategy for multi-phase interleaved boundary mode and DCM boost PFC converters

A digital control strategy which provides optimal interleaving of multi-phase boost power factor correction (PFC) rectifiers operating at DCM/CCM boundary (BCM) or in DCM is presented in this paper. In this method two feedforward algorithms are used. The first provides the turn-on time to attain the desired input current and the second computes the switching period time to achieve BCM operation. An extension to operate in DCM is proposed to avoid CCM under all conditions. Regulated DCM is used to realize a new continuous phase shedding method, which is used to limit the switching frequency. The proposed control structure was implemented on a microcontroller. Experimental results show the effectiveness of the control strategy on a boost PFC prototype with 3 parallel rails.