Analysis of a ZVS DC-DC full-bridge converter with natural hold-up time

Two stage AC-DC converters consisting of front-end Power Factor Correction (PFC) AC-DC boost converter followed by isolated DC-DC converters are the industry workhorse for powering network servers, telecom and other DC loads. Such converters are powered from single phase AC utility mains. For proper operation of these loads, the AC-DC converters provide a regulated DC voltage that ranges from 12V to 48V depending on the type of load. For safe uninterrupted operation during sudden intermittences in power supplied from the AC mains, the AC-DC power converter should be able to supply such loads with constant DC output voltage for a certain duration in order to prevent them from unwanted resetting. The maximum duration for which the AC-DC converter can supply the load with regulated DC output voltage at its maximum output power after input AC mains failure, is known as “hold-up-time (HUT)” of the converter. This paper proposes a novel DC-DC non resonant full-bridge converter with extended hold up time capability with reduced input storage capacitance.