Optimizing dual half bridge converter for full range soft switching and high efficiency

This paper is concerned with finding the optimum operating points of a soft-switched dual half bridge bidirectional dc-dc converter. Phase shift modulation (θ) with a fixed duty cycle is used to control the converter [1] but the soft switching range is limited. In this paper the soft switching range and efficiency of the converter are highly improved by recruiting duty cycle (d) as the second control parameter. It is shown that for a wide voltage range on both dc buses, soft switching can be achieved for any power level including zero to full load in both directions. The regions of soft switching on the (θ,d) plane are analyzed and the trajectories of the optimal (θ,d) values for highest efficiencies are extracted. A precise simulated model of the converter is developed to verify and fine tune the analytic results. Finally a 250 KHz, 1.5Kw prototype is designed and implemented to verify the results in practice.