An embodiment hybrid dc/dc converter comprises a first power source and a low power converter coupled to the first power source. The low power converter generates an output connected in series with the first power source. The hybrid dc/dc converter further comprises a selection network coupled to the first power source and the output of the low power converter and a main unregulated power converter coupled to the selection network. By controlling the voltage across the output of the low power converter, the hybrid dc/dc converter can achieve high efficiency through the unregulated power converter.