Analysis and design of a series resonant converter with constant current input and regulated output current

Constant current dc distribution to series connected loads has been preferred for long distance high reliability systems such as undersea cabling for telecommunications and observation networks. In addition, some loads require constant current output, creating a need for high efficiency power supplies that provide a regulated current gain from input current to output current. Series resonant converters (SRCs) are a good candidate with the potential for high output impedance current source output behavior. However, SRCs behave differently with constant current input compared to traditional constant voltage input, a behavior that has not been well studied in the literature. This work presents detailed analysis and design considerations for SRCs operated with constant current input and regulated to provide a constant current output. The converter control method, zero-voltage-switching (ZVS) realization, and approaches to maintain SRC operation at resonance are discussed. The current source property of the SRC offers many advantages such as independence of load voltage, parallel operation and short circuit output protection. Hardware results are presented for a 380 kHz, 450 W prototype SRC with 1 A input current and 0.33 A regulated output current.