Analysis of zero voltage switching requirements and passive auxiliary circuit design for DC-DC series resonant converters with constant input current

Constant current distribution systems such as under-sea power distribution systems use power converters with a constant input current as a source of input power. This paper analyzes minimum requirements for passive zero-voltage-switching (ZVS) components of dc-dc series resonant converters (SRCs) in dc distribution systems. A steady state analysis of the technique shows that the input voltage varies with the output power of the converter when using a constant input current source. Thus, ZVS requirements deviate from traditional solutions as commonly used for SRCs with a constant input voltage. Design guidelines for selecting the ZVS assisting inductor are presented to achieve ZVS for all active switches over a wide load range without significantly increasing the overall conduction losses. The approach is validated using experimental results for a 400 kHz 450 W SRC with 1 A constant input current and 0.33 A output current.