There is disclosed a core structure with a very low profile, high power density and lower losses. The disclosed design allows for a larger core area where the DC fluxes are added, thereby reducing the air-gap requirements in the cores derived from low saturation density materials such as ferrites. The cellular nature of the design can be effectively employed in vertically packaged power converters and modules. Also disclosed is a DC-DC converter topology which preferably employs the disclosed core. N AC drive voltages drive N current doubler rectifiers (CDRs) in accordance with the symmetric modulation scheme; each CDR provides two rectified output currents to an output node. Each AC drive voltage has a switching period Ts. The drive voltages are phase-shifted by Ts/(2*N), such that the rectified output currents of the CDRs are interleaved, thereby reducing output voltage ripple.