A switched inductor DC-DC power converter chiplet includes a CMOS power switch, an LC filter, regulation circuitry, feedback control circuitry, and interface control circuitry integrated on a common substrate. The inductor for the LC filter can be formed on the same surface or on opposing surfaces of the substrate as the electrical terminations for the substrate. Another embodiment includes a switched inductor DC-DC power converter chiplet having a first powertrain phase and multiple second powertrain phases. When the load current is less than or equal to a threshold load current, the power conversion efficiency can be improved by only operating the first powertrain phase. When the load current is greater than the threshold load current, the power conversion efficiency can be improved by operating one or more second powertrain phases.