High efficient 3kW three-stage power supply

Today's power supplies for the IT sector and telecommunication field show typically a two-stage setup consisting of PFC rectifier and DC/DC stage. The DC/DC stage is designed according to hold-up time requirements, thus it does not work optimally at nominal conditions. The insertion of an additional stage between PFC rectifier and DC/DC converter yields an increase of total efficiency and minimization of the volume and weight of the power supply. In this contribution several topology candidates for high power three-stage power supplies are compared with state-of-the-art two-stage candidates in terms of efficiency, complexity and durability. Accordingly, the best candidate is pre-selected, simulated, developed and is built as prototype. The system modeling of the complete power supply is required for design of the control circuit. A built-up prototype of the three-stage power supply is evaluated and tuning measures are termed. Concluding measurements are discussed and supplemented by final conclusions. The keys of the proposed three-stage solution are particularly the synchronous rectification at an output voltage of 12 V, interleaving of four parallel-connected output stages for best distribution of 3 kW output power, and small volume resulting in a height of 1.75"=44 mm, which is only one unit within the rack.