A rectifier unit using series resonant converter with voltage resonant control for light load

The authors describe a rectifier unit using a series resonant power converter designed for rack-mounted DC power systems. For a light load, this converter is controlled by voltage resonance formed with a parallel resonant circuit. An averaged circuit model is proposed. It approximates the parallel and series resonant circuit as a simple series resonant circuit with the capacitor which has frequency-dependency capacitance. The averaged model was verified with detailed model simulation and experimental results. Characteristics of a rectifier unit using the resonant converter with AC three-phase 200 V input and DC 56 V 50 A output are presented. A weight of 11.5 kg for the unit has been achieved with natural air cooling. The efficiency was 90% or higher at output currents from 10 A to 50 A and 92.8% at 50 A