Patent ID: 7688048

Claim:
A circuit for use with four-level DC power including first, second, third, and fourth voltages, the circuit comprising: first, second, third, and fourth nodes configured to receive the four-level DC power; first, second, third, fourth, fifth, and sixth switches coupled in series between the first and fourth nodes, wherein the second node is coupled to a junction of the second and third switches and the third node is coupled to a junction of the fourth and fifth switches; a first diode coupled in parallel with the first switch; a second diode coupled in parallel with the second switch; a third diode coupled in parallel with the third switch; a fourth diode coupled in parallel with the fourth switch; a fifth diode coupled in parallel with the fifth switch; a sixth diode coupled in parallel with the sixth switch; a first resonant tank coupled to a junction of the first and second switches and to the junction of the third and fourth switches; and a second resonant tank coupled to the junction of the third and fourth switches and to the junction of the fifth and sixth switches; wherein the first and second resonant tanks are configured to shift energy between at least two of the first, second, third, and fourth nodes if an absolute value of the first voltage differs from an absolute value of the fourth voltage; and wherein the first and second resonant tanks are configured to shift energy between at least two of the first, second, third, and fourth nodes if an absolute value of the second voltage differs from an absolute value of the third voltage.