Design Considerations for Current-Regulated Series-Resonant Converters With a Constant Input Current

Power converters used for undersea applications utilize dc current distribution instead of dc voltage distribution due to the long distance from the shore and cable series impedance. Power converter modules employed in such scenarios use a constant current as a source of input power with several modules connected in series. Series-resonant converters (SRCs), which are used in each module, behave differently when driven by a constant-current input in comparison to the conventional case with a constant-voltage input. The differences in the behavior and design of such SRCs have not been thoroughly studied in the literature. In this paper, detailed steady-state analysis is presented to show the findings, and a design procedure is proposed for regulating the output current of an SRC topology with its input connected to a constant-current source. Constraints on the selection of resonant tank components and operating frequency are satisfied, while regulating the output current over the desired load range. The proposed design also considers variations of the component values accounting for the changes due to tolerances as well as aging. A design example for supplying power to an undersea observation system and hardware validation results are provided for a 400 kHz 450 W SRC with a constant input current of 1 A and an output current of 330 mA.