High efficiency amplification

1. A power supply stage, comprising:

a. reference means for providing a reference signal representing a desired power supply voltage;

b. selection means for selecting one of a plurality of power supply voltages in dependence on the reference signal, the selection means being adapted for selecting a power supply voltage above and below the reference signal, in dependence on the value of the reference signal;

c. adjusting means adapted to generate an adjusted selected power supply voltage tracking the reference signal in dependence on the selected power supply voltage and the reference signal.

2. A power supply stage according to claim 1 wherein the power supply stage is for an amplifier, the reference signal representing the envelope of an input signal of said amplifier.

3. A power supply stage according to claim 2 in which there is provided a delay element for compensating for differences in delays between the signal amplifier and power supply control input.

4. A power supply stage according to claim 1 wherein the adjusting means includes an AC amplifier.

5. A power supply according to claim 4 wherein the selected power supply voltage has a minimum absolute difference between said power supply voltage and the reference signal level.

6. A power supply stage according to claim 4 wherein the ac amplifier is connected to amplify the difference between the reference signal and a representation of the selected power supply voltage.

7. A power supply stage according to claim 6 wherein the adjusting means includes means for summing the amplified difference with the selected supply voltage.

8. A power supply stage according to claim 7 , wherein the representation of the selected power supply voltage is the power supply voltage itself.

9. A power supply stage according to claim 7 wherein the representation of the selected power supply voltage is the adjusted selected power supply voltage.

10. A power supply stage according to claim 4 wherein the adjusting means further includes a high frequency amplifier.

11. A power supply stage according to claim 10 wherein the high frequency amplifier is connected to amplify the difference between the reference signal and a representation of the adjusted power supply voltage.

12. A power supply stage according to claim 11 wherein the adjusting means includes means for summing the amplified difference with the adjusted supply voltage to generate a further adjusted supply voltage.

13. A power supply stage according to claim 12 wherein the representation of the adjusted supply voltage is the adjusted supply voltage itself.

14. A power supply stage according to claim 12 wherein the representation of the adjusted supply voltage is the further adjusted supply voltage.

15. A power supply stage according to claim 12 wherein the further adjusted supply voltage forms the output of the power supply stage.

16. A power supply stage according to claim 4 wherein there is further provided means for DC clamping the AC amplifier.

17. A power supply stage according to claim 16 wherein the means for DC clamping is responsive to detection of the reference signal being less than the adjusted supply voltage.

18. A power supply stage according to claim 4 wherein there is further provided slow DC adjustment means for removing a DC component from the AC amplifier.

19. A power supply stage according to claim 1 wherein the adjusted selected supply voltage is the output of the power supply stage.

20. A power supply stage according to claim 1 in which there is further provided an interpolation means at the input to the adjusting means such that the selected power supply voltage is interpolated.

21. A power supply stage according to claim 20 wherein the interpolation means comprises an inductor-capacitor arrangement.

22. A power supply stage according to claim 1 in which there is provided a delay element for delaying the reference signal.

23. A power supply stage according to claim 1 in which the adjusting means comprises a plurality of cascaded correction circuits.

24. A power supply according to claim 23 in which the adjusting means comprises two or more cascaded correction circuits.

25. A radio frequency amplification stage comprising:

a. an amplifier for receiving an input signal to be amplified and a power supply voltage; and

b. a power supply voltage stage for supplying said power supply voltage, comprising:

i. means for providing a reference signal representing a desired power supply voltage corresponding to the envelope of the input signal;

ii. means for selecting one of a plurality of supply voltage levels in dependence on the reference signal, the means for selecting being adapted for selecting the supply voltage level above and below the reference signal; and

iii. means for generating an adjusted selected power supply voltage, comprising an AC amplifier for amplifying a difference between the reference signal and one of the selected supply voltage level or the adjusted selected supply voltage level, and a summer for summing the amplified difference with the selected supply voltage to thereby generate the adjusted supply voltage.

26. A radio frequency amplification stage according to claim 25 in which the means for generating an adjusted selected supply voltage further generates a further adjusted supply voltage and further comprises an RF amplifier for amplifying a difference between the reference signal and one of the adjusted supply voltage or the further adjusted supply voltage, and a summer for summing such amplified difference with the adjusted supply voltage to thereby generate the further adjusted supply voltage.

27. A radio frequency amplification stage according to claim 25 wherein one of the adjusted supply voltage or further adjusted supply voltage forms the supply voltage to the amplifier.

28. A method of controlling a power supply stage, comprising:

a. providing a reference signal representing a desired power supply voltage;

b. selecting one of a plurality of power supply voltages in dependence on the reference signal, the selecting step being adapted for selecting a power supply voltage above and below the reference signal, in dependence on the value of the reference signal;

c. generating an adjusted selected power supply voltage tracking the reference signal in dependence on the selected power supply voltage and the reference signal.

29. A method according to claim 28 wherein the reference signal represents the envelope of an input signal to an amplifier, the power supply stage providing a power supply to said amplifier.

30. A method according to claim 28 wherein the difference between the reference signal and a representation of the selected power supply voltage is AC amplified.

31. A method according to claim 30 wherein the amplified difference is summed with the selected supply voltage to form the adjusted supply voltage.

32. A method according to claim 31 wherein the difference between the reference signal and a representation of the adjusted power supply voltage is RF amplified.

33. A method according to claim 32 wherein the amplified difference is summed with the adjusted supply voltage to form a further adjusted supply voltage.

34. A method according to claim 30 further comprising providing means for removing a dc component in the AC amplification step.

35. A method according to claim 28 further comprising an interpolating step prior to said step of generating an adjusted supply voltage.

36. A power supply stage, comprising:

a. an envelope detector for providing a reference signal representing a desired power supply voltage;

b. a supply voltage selection block for selecting one of a plurality of power supply voltages in dependence on the reference signal, the supply voltage selection block being adapted for selecting a power supply voltage above and below the reference signal in dependence on the value of the reference signal;

c. a supply voltage adjustment block adapted to generate an adjusted selected power supply voltage tracking the reference signal in dependence on the selected power supply voltage and the reference signal.

37. A radio frequency amplification stage comprising:

a. an amplifier for receiving an input signal to be amplified and a power supply voltage; and

b. a power supply voltage stage for supplying said power supply voltage, comprising:

i. an envelope detector for providing a reference signal representing a desired power supply voltage corresponding to the envelope of the input signal;

ii. a supply voltage selection block for selecting one of a plurality of supply voltage levels in dependence on the reference signal, the supply voltage selection block being adapted for selecting a supply voltage level above and below the reference signal; and

iii. a supply voltage adjustment block for generating an adjusted selected power supply voltage, comprising an AC amplifier for amplifying a difference between the reference signal and one of the selected supply voltage level or the adjusted selected supply voltage level, and a summer for summing the amplified difference with the selected supply voltage to thereby generate the adjusted supply voltage.

38. A power supply stage, comprising:

reference means for providing a reference signal representing a desired power supply voltage;

selection means for selecting one of a plurality of power supply voltages in dependence on the reference signal, the selection means being adapted for selecting a power supply voltage below the reference signal, in dependence on the value of the reference signal; and

adjusting means adapted to generate an adjusted selected power supply voltage tracking the reference signal in dependence on the selected power supply voltage and the reference signal.

39. A power supply stage according to claim 38 , the selection means being adapted for selecting a power supply voltage such that the power supply voltage tracks above and below the reference signal.

40. A method of controlling a power supply stage, comprising:

providing a reference signal representing a desired power supply voltage;

selecting one of a plurality of power supply voltages in dependence on the reference signal, the selecting step being adapted for selecting a power supply voltage below the reference signal, in dependence on the value of the reference signal; and

generating an adjusted selected power supply voltage tracking the reference signal in dependence on the selected power supply voltage and the reference signal.

41. A method according to claim 40 , the selecting step being adapted for selecting a power supply voltage such that the power supply voltage tracks above and below the reference signal.

42. A power supply stage, comprising:

an envelope detector for providing a reference signal representing a desired power supply voltage;

a supply voltage selection block for selecting one of a plurality of power supply voltages in dependence on the reference signal, the supply voltage selection block being adapted for selecting a power supply voltage below the reference signal in dependence on the value of the reference signal; and

a supply voltage adjustment block adapted to generate an adjusted selected power supply voltage tracking the reference signal in dependence on the selected power supply voltage and the reference signal.

43. A power supply stage according to claim 42 , the selection means being adapted for selecting a power supply voltage such that the power supply voltage tracks above and below the reference signal.