Transformer based voltage supply
There is disclosed a voltage summer including a transformer having a primary side and a secondary side, wherein a first voltage to be summed is connected to the primary side and a second voltage to be summed is connected to the secondary side. There is further disclosed a transformer comprising a primary winding and a secondary winding and having a turns ratio of primary winding to secondary winding of x:y, providing x turns in series in the primary winding and providing y turns in series in the secondary winding; providing an equal number of turns in the primary and secondary windings; and closely coupling each primary winding turn with a secondary winding turn.
1. A modulated power supply including a voltage summer, a first voltage source, and a second voltage source, for providing a modulated power supply voltage, the voltage summer including a transformer having a primary side and a secondary side, wherein the first voltage source is connected to provide a first voltage to one side of the transformer, and the second voltage source is connected to provide a second voltage to another side of the transformer, wherein the transformer provides a modulated output voltage representing the first voltage adjusted by the second voltage.
2. A modulated power supply according to claim 1 , wherein the first voltage is connected between the first tap of the primary side and the second tap of the primary side, and the second voltage is connected to a first tap of the secondary side, the modulated output voltage being provided on a second tap of the primary or secondary side.
3. A modulated power supply according to claim 2 , wherein the first voltage is greater than the second voltage and the modulated output voltage is provided on the second tap of the primary side of the transformer.
4. A modulated power supply according to claim 1 wherein the first voltage is a variable voltage.
5. A modulated power supply according to claim 4 wherein the first voltage is provided by a first switchable voltage source.
6. A modulated power supply according to claim 4 wherein the second voltage is a variable voltage.
7. A modulated power supply according to claim 6 wherein the second voltage is provided by a second switchable voltage source.
8. A modulated power supply according to claim 6 wherein the first voltage is variable between n levels and the second voltage is variable between m levels, wherein the summed voltage is variable between n*m levels.
9. A modulated cower supply according to claim 6 wherein the second voltage is provided by a continuously variable voltage source.
10. A modulated power supply according to claim 6 wherein the second voltage is provided by a fixed voltage source.
11. A modulated cower supply according to claim 1 wherein the first voltage is a coarse voltage signal and the second voltage is a fine voltage signal.
12. A modulated cower supply according to claim 11 wherein the fine voltage signal is representative of an error in the coarse voltage signal.
13. A modulated power supply according to claim 12 , further including a reference voltage source, and a difference means for removing the reference voltage from the summed voltage to generate the second voltage.
14. A modulated cower supply according to claim 12 , further including a reference current source, a means for sensing the current in the primary side of the transformer, a difference means for removing the reference current from the sensed current to generate a difference current, and a driver for supplying the second voltage in dependence on the difference current.
15. A method of providing a modulated power supply including applying a first voltage to one side of a transformer and applying a second voltage to another side of the transformer, wherein a sum of the first and second voltages provides a modulated output voltage on one of the first or second sides of the transformer representing the first voltage adjusted by the second voltage.
16. A method of providing a modulated power supply according to claim 15 , wherein the first voltage is applied between a first tap of a primary side and a second tap of the primary side, and the second voltage is applied to a first tap of a secondary side, wherein the modulated output voltage is provided on a second tap of the primary or secondary side.
17. A method of providing a modulated power supply according to claim 16 , wherein the first voltage is greater than the second voltage and the modulated output voltage is provided on the second tap of the primary side of the transformer.
18. A method of providing a modulated power supply according to claim 15 further comprising the step of varying the first voltage.
19. A method of providing a modulated power supply according to claim 15 further comprising the step of varying the second voltage.
20. A method of providing a modulated power supply according to claim 18 comprising varying the first voltage between n levels and varying the second voltage between m levels, wherein the modulated output voltage is thereby variable between n*m levels.
21. A method of providing a modulated power supply according to claim 15 wherein the first voltage is a coarse voltage signal and the second voltage is a fine voltage signal.
22. A method of providing a modulated power supply according to claim 21 wherein the fine voltage signal is representative of an error in the coarse voltage signal.
23. A method of providing a modulated power supply according to claim 15 , further including the step of generating a reference voltage, and removing the reference voltage from the summed voltage to thereby generate the second voltage.
24. A method of providing a modulated power supply according to claim 15 , further including the step of generating a reference current, sensing the current in the primary side of the transformer, removing the reference current from the sensed current to generate a difference current, and supplying the second voltage in dependence on the difference current.
25. A modulated power supply according to claim 1 wherein the first voltage source is independent of the second voltage source.
26. A modulated power supply according to claim 1 wherein the first voltage is directly connected to the one side of the transformer and the second voltage is directly connected to the other side of the transformer.
27. A method according to claim 15 wherein the first voltage is independent of the second voltage.
28. A method according to claim 15 comprising directly connecting the main voltage to the one side of the transformer and directly connecting the correction voltage to the other side of the transformer.