A power converter includes a DC port and an AC port. A set of controllable “DC” switches couples the DC port to a central series-resonant circuit, and a set of “AC switches couples the central circuit through a filter to the AC port. A switch control circuit responds to secondary-to-tertiary and inversion time percentages, and a modulator is responsive to the AC filter voltage and to the current at the AC port, for generating the inversion (inv) and secondary-to-tertiary (s2t) time percentages.