Bi-directional buck/boost dc-dc converter with ultra high efficiency based on improved SAZZ topology

An improved bi-directional buck/boost SAZZ topology is proposed in this paper. The improvements are aimed at increasing the total conversion efficiency as well as at enlarging the soft switching operating area and hence improving the overall converter performance. The modifications with respect to the conventional SAZZ topology are: configuration of snubber circuits enhanced by saturable inductors and use of synchronous rectification. The proposed topology is implemented in a 60 kW, 50 kHz converter design. The improved topology reaches conversion efficiencies in the 99 % region in a broad range of operating conditions and output power. In the same time, the improved topology together with an advance structural and thermal converter design result in the power density higher than 40 kW/l.