High-Efficiency Envelope Tracking Systems and Methods for Radio Frequency Power Amplifiers

• US 20090191826A1
• Filed: 01/29/2008
• Published: 07/30/2009
• Est. Priority Date: 01/29/2008
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Liang, Paul Cheng-Po, Takinami, Koji
• Granted Patent: US 7,949,316 B2
• Time in Patent Office: Days
• US Class Current: 455/110
• CPC Class Codes: H02M 1/0045 Converters combining the concepts of switch-mode regulation and linear regulation, e.g. linear pre-regulator to switching converter, linear and switching converter in parallel, same converter or same transistor operating either in linear or switching mode
• CPC Class Codes: H03F 1/0227 using supply converters
• CPC Class Codes: H03G 3/004 Control by varying the supply voltage

Abstract

Envelope tracking (ET) methods and systems for controlling the delivery of power to radio frequency power amplifiers (RFPAs). An exemplary ET system includes an RFPA and a wide bandwidth capable and power efficient envelope modulator that includes a first power supplying apparatus and a second power supplying apparatus. The first power supplying apparatus includes a switch-mode converter and a regulator. The first mode converter is operable to dynamically step down a fixed power supply voltage according to amplitude variations in an envelope signal received by the regulator, and use the resulting dynamic power supply signal to power the regulator. The second power supplying apparatus is connected in parallel with the first power supplying apparatus. Depending on a power of an output signal to be generated at an output of the power amplifier, power is supplied to the power amplifier from either or both of the first and second power supplying apparatuses.

Claims

1. An envelope modulator apparatus for generating a dynamic power supply signal, comprising:

a first switch-mode converter having a power supply input configured to receive a direct current (DC) power supply voltage, a switch control input configured to receive a first switch control signal, and an output configured to provide a dynamic power supply signal;

a regulator having an envelope signal input configured to receive an envelope signal, a power supply input configured to receive the dynamic power supply signal from said first switch-mode converter, and an output configured to supply current to a load; and

a second switch-mode converter having a power supply input configured to receive said DC power supply voltage, a switch control input configured to receive a second switch control signal, and an output configured to provide current to said load.

2. The envelope modulator apparatus of claim 1 wherein said first switch control signal includes signal characteristics relating to amplitude variations in said envelope signal, and the first switch-mode converter is configured to generate said dynamic power supply signal so that it generally tracks amplitude variations in said envelope signal.

3. The envelope modulator apparatus of claim 2 wherein said regulator comprises a linear regulator and said first switch-mode converter is configured to generate said dynamic power supply signal so that at any given time the dynamic power supply signal has a magnitude no higher than necessary to keep the linear regulator operating in its active region.

4. The envelope modulator apparatus of claim 1 wherein the first switch-mode converter and regulator are configured such that when the DC power supply voltage is coupled to the power supply input of said first switch-mode converter an amount of the DC voltage that is dropped across the first switch-mode converter compared to an amount of the DC voltage that is dropped across the regulator is dependent on signal characteristics contained in said first switch control signal.

5. The envelope modulator apparatus of claim 4 wherein the signal characteristics of said first switch control signal include signal characteristics relating to amplitude variations in said envelope signal.

6. A method of controlling the supply of current to a power supply input of a power amplifier, comprising:

receiving an envelope signal at a signal input of a first power supplying apparatus;

generating a dynamic power supply signal based on amplitude variations in said envelope signal;

coupling said dynamic power supply signal to a power supply input of said first power supplying apparatus;

coupling a fixed power supply voltage to power a second power supplying apparatus coupled in parallel with said first power supplying apparatus; and

depending on a power of an output signal to be generated at an output of a power amplifier supplying current from either or both of said first and second power supplying apparatuses to a power supply input of said power amplifier.

7. The method of claim 6 wherein generating the dynamic power supply signal for the power supply input of the first power supplying apparatus comprises dynamically stepping down said fixed power supply voltage so that said dynamic power supply signal generally tracks amplitude variations of said envelope signal.

8. The method of claim 6 wherein said first power supplying apparatus comprises:

a first switch-mode converter configured to generate said dynamic power supply signal; and

a regulator having a power supply input configured to receive the dynamic power supply signal from the switch-mode converter.

9. An envelope tracking (ET) system, comprising:

an envelope modulator configured to generate an envelope modulated power supply signal that generally tracks amplitude variations of an input envelope signal, said envelope modulator including;

first power supplying means configured to be powered by a dynamic power supply signal that generally tracks amplitude variations in said input envelope signal, and

second power supplying means connected in parallel with said first power supply means and configured to be powered by a direct current (DC) power supply voltage; and

a power amplifier having a power supply input configured to receive the envelope modulated power supply signal from the envelope modulator and current from one or both of said first and second power supplying means of the envelope modulator.

10. The ET system of claim 9 wherein said first power supplying means comprises a switching means coupled in series with a regulating means, said switching means having a switch control input configured to receive a switch control signal, a power supply input configured to receive said DC power supply voltage, and an output configured to provide a dynamic power supply signal to said regulating means.

11. The ET system of claim 10 wherein said switch control signal comprises a switch control signal having signal characteristics relating to amplitude variations in said input envelope signal.

12. A power control circuit, comprising:

a first power supply apparatus configured to supply a first current to a load; and

a second power supply apparatus coupled in parallel with said first power supply apparatus including a switch-mode converter coupled in series with a regulator configured to source current to said load or sink current supplied by said first power supply apparatus depending on whether an instantaneous current required of said load is less than or greater than said first current.

13. The power control circuit of claim 12 wherein said switch-mode converter is configured to generate a dynamic power supply for said regulator, said dynamic power supply having signal levels determined by amplitude variations in an envelope signal received by the power control circuit.

14. The power control circuit of claim 13 wherein said regulator is configured to source current to said load when the instantaneous current required of the load is greater than the first current supplied from said first power supply apparatus.

15. The power control circuit of claim 14 wherein said regulator is configured to sink current from said first power supply apparatus when the instantaneous current required of the load is less than the first current supplied from said first power supply apparatus.

16. The power control circuit of claim 13 wherein the load comprises a linear radio frequency power amplifier (RFPA) configured to amplify said envelope signal.

17. The power control circuit of claim 16 wherein said envelope signal comprises a non-constant envelope signal.

18. The power control circuit of claim 13 wherein said load comprises a nonlinear radio frequency amplifier (RFPA).

19. The power control signal of claim 18 wherein said envelope signal includes envelope information of a communications signal and a constant envelope angle modulated RF signal applied to an RF input of said RFPA includes angle information of said communications signal.

20. A polar transmitter, comprising:

a phase modulator configured to generate a phase modulated radio frequency (RF) signal;

an envelope modulator configured to modulate a DC power supply voltage according to an envelope modulation signal to generate an envelope modulated power supply signal, said envelope modulator including a first power supplying apparatus configured to be powered by said DC power supply voltage, and a second power supplying apparatus configured to be powered by a dynamic power supply signal; and

a power amplifier having an RF input configured to receive said phase modulated RF signal from said phase modulator and a power supply input configured to receive said envelope modulated power supply signal from said envelope modulator.

21. The polar transmitter of claim 20 wherein said second power supplying device comprises:

a first switch-mode converter configured to dynamically step down said DC power supply voltage to generate said dynamic power supply signal; and

a regulator having a first input configured to receive said envelope modulation signal and a second input configured to receive the dynamic power supply signal from said first switch-mode converter.

22. The polar transmitter of claim 21 wherein said first switch-mode converter includes a switch control input configured to receive a switch control signal that causes the first switch-mode converter to generate the dynamic power supply signal so that it generally tracks amplitude variations of the envelope modulated power supply signal.