AC to DC power supply systems and methods

1. An AC to DC power supply system comprising:

a transformer having a primary side and a secondary side;

a passive rectifier coupled to the secondary side of the transformer, the passive rectifier configured to rectify AC power at the secondary side to DC power at an output of the passive rectifier;

an active rectifier coupled to the primary side of the transformer, the active rectifier configured to control voltages applied to the primary side of the transformer to induce a non-sinusoidal voltage at the secondary side of the transformer and a sinusoidal current drawn by the passive rectifier; and

an isolating DC-to-DC converter coupled between the active rectifier and the output of the passive rectifier to magnetically couple power from the active rectifier to the output of the passive rectifier while galvanically isolating the active rectifier from the output of the passive rectifier.

2. The AC to DC power supply system of claim 1 , wherein the active rectifier is configured to impart harmonics on the primary side of the transformer to induce non-sinusoidal voltages on the secondary side of the transformer.

3. The AC to DC power supply system of claim 1 , wherein the passive rectifier draws the sinusoidal current during rectification of the non-sinusoidal voltage.

4. The AC to DC power supply system of claim 1 , wherein the DC-to-DC converter is configured to feed power from the active rectifier to the output of the passive rectifier while galvanically isolating the active rectifier from the output of the passive rectifier.

5. The AC to DC power supply system of claim 1 , further comprising a DC load connected to the output of the passive rectifier and to an output of the DC-to-DC converter, and where in each of the passive rectifier and the DC-to-DC converter supplies a portion of DC power drawn by the DC load.

6. The AC to DC power supply system of claim 5 , wherein the passive rectifier supplies a majority of power applied to the DC load and the DC-to-DC converter supplies a minority of power applied to the DC load.

7. The AC to DC power supply system of claim 6 , wherein the passive rectifier supplies at least 70% of power applied to the DC load and the DC-to-DC converter supplies a remainder of power applied to the DC load.

8. The AC to DC power supply system of claim 1 , wherein the passive rectifier comprises passively switched devices configured to operate at current levels exceeding 800 Amps.

9. An AC to DC power supply system comprising:

a three-phase transformer including a grid-connectable primary side with three windings and a secondary side;

an active rectifier coupled to the primary side of the transformer, the active rectifier switchably connecting each of the three windings in series between a positive bus and a negative bus to alter a magnetic flux in a core of the transformer;

a passive rectifier coupled to the secondary side of the transformer to rectify AC power to DC power at an output of the passive rectifier; and

an isolating DC-to-DC converter coupled between the positive bus and the negative bus and the output of the passive rectifier, wherein the DC-to-DC converter is configured to feed power from the active rectifier to the output of the passive rectifier while galvanically isolating the active rectifier from the output of the passive rectifier.

10. The AC to DC power supply system of claim 9 , wherein the altered magnetic flux induces non-sinusoidal voltages on the secondary side of the transformer.

11. The AC to DC power supply system of claim 10 , wherein rectification of the non-sinusoidal voltages draws sinusoidal current.

12. The AC to DC power supply system of claim 9 , further comprising a DC load connected to the output of the passive rectifier and to an output of the DC-to-DC converter, and where in each of the passive rectifier and the DC-to-DC converter supplies a portion of DC power drawn by the DC load.

13. The AC to DC power supply system of claim 12 , wherein the passive rectifier supplies a majority of power applied to the DC load and the DC-to-DC converter supplies a minority of power applied to the DC load.

14. The AC to DC power supply system of claim 13 , wherein the passive rectifier supplies at least 70% of power applied to the DC load and the DC-to-DC converter supplies a remainder of power applied to the DC load.

15. A method for providing power to a load, the method comprising:

coupling a transformer to a source of sinusoidal AC power and transforming voltage and current of the AC power with the transformer to produce transformed AC power on a secondary side of the transformer;

switchably drawing power, simultaneously with the transforming, from each winding of the transformer to add a non-sinusoidal voltage to each primary winding of a primary side of the transformer, thereby inducing a non-sinusoidal voltage in the transformed AC power in each secondary winding of the secondary side of the transformer;

rectifying the non-sinusoidal voltage in the transformed AC power to produce rectified DC power;

applying the rectified DC power to a DC load; and

feeding the drawn power from each primary winding to the DC load via a galvanically isolated coupling.

16. The method for providing power to a load of claim 15 , wherein the rectifying draws a sinusoidal AC current through the transformer.