Highly-Efficient and Cost-Effective Ripple-Free Resonant NPC DC-DC Converter

This article presents highly-efficient and inexpensive ripple-free resonant neutral-point-clamped (NPC) dc-dc converter that does not use extra inductors. By using the push-pull transformer itself, with the primary-side switching modulation fixed at 0.5, the proposed converter accomplishes theoretically zero input current ripple. Because of the resonant NPC cell, the circuit does not experience instantaneous reactive current flow regardless of wide input voltage variation. The resonant NPC structure much reduces the voltage stress at the turn- off instant; this aspect enables use of inexpensive low-voltage-rated active power components. Therefore, the proposed converter is inexpensive, highly efficient, and has high power density. A 1-kW experimental prototype was implemented and it was tested to validate the superior properties of the proposed converter.