Apparatus and methods for envelope tracking systems with automatic mode selection

• US 10,110,169 B2
• Filed: 09/07/2017
• Issued: 10/23/2018
• Est. Priority Date: 09/14/2016
• Status: Active Grant

• Current Assignee: Skyworks Solutions Incorporated
• Original Assignee: Skyworks Solutions Incorporated
• Inventors: Khesbak, Sabah, Drogi, Serge Francois, Balteanu, Florinel G.
• Primary Examiner(s): Patel, Dhaval
• Application Number:
  US15/697,789
• Publication Number:
  US 20180076772A1
• Time in Patent Office: 411 Days
• Field of Search: 375297, 375226, 375227, 330136, 330199, 330296, 330291, 330297, 4551273, 4551275
• CPC Class Codes: H03F 1/0227 using supply converters
• CPC Class Codes: H03F 1/025 by using a signal derived from the input signal
• CPC Class Codes: H03F 1/0261 with control of the polarisation voltage or current, e.g. gliding Class A
• CPC Class Codes: H03F 1/0277 Selecting one or more amplifiers from a plurality of amplifiers
• CPC Class Codes: H03F 1/3247 using feedback acting on predistortion circuits H03F1/3264 takes precedence
• CPC Class Codes: H03F 2200/102 A non-specified detector of a signal envelope being used in an amplifying circuit
• CPC Class Codes: H03F 2200/171 A filter circuit coupled to the output of an amplifier
• CPC Class Codes: H03F 2200/336 A I/Q, i.e. phase quadrature, modulator or demodulator being used in an amplifying circuit
• CPC Class Codes: H03F 2200/414 A switch being coupled in the output circuit of an amplifier to switch the output on/off
• CPC Class Codes: H03F 2200/417 A switch coupled in the output circuit of an amplifier being controlled by a circuit
• CPC Class Codes: H03F 2200/511 Many discrete supply voltages or currents or voltage levels can be chosen by a control signal in an IC-block amplifier circuit
• CPC Class Codes: H03F 2200/555 A voltage generating circuit being realised for biasing different circuit elements
• CPC Class Codes: H03F 3/195 in integrated circuits
• CPC Class Codes: H03F 3/245 with semiconductor devices only
• CPC Class Codes: H03F 3/45183 Long tailed pairs H03F3/4521, H03F3/45237 take precedence
• CPC Class Codes: H03G 1/0029 using FETs
• CPC Class Codes: H03G 1/0088 using discontinuously variable devices, e.g. switch-operated
• CPC Class Codes: H03G 3/001 Digital control of analog signals
• CPC Class Codes: H03G 3/3042 in modulators, frequency-changers, transmitters or power amplifiers transmission power control in bidirectional transmission systems H04W52/04

Abstract

Apparatus and methods for envelope tracking systems with automatic mode selection are provided herein. In certain configurations, a power amplifier system includes a power amplifier that amplifies a radio frequency signal and that receives power from a power amplifier supply voltage. The power amplifier system further includes an envelope tracker that generates the power amplifier supply voltage based on an envelope signal corresponding to an envelope of the radio frequency signal. The envelope tracker includes a signal bandwidth detection circuit that processes the envelope signal to generate a detected bandwidth signal, and a mode control circuit that controls a mode of the error amplifier based on the detected signal bandwidth.

Claims

1. A power amplifier system comprising:

a power amplifier configured to provide amplification to a radio frequency signal and to receive power from a power amplifier supply voltage; and

an envelope tracker configured to generate the power amplifier supply voltage based on an envelope signal corresponding to an envelope of the radio frequency signal, the envelope tracker including a DC-to-DC converter, an error amplifier, a signal bandwidth detection circuit configured to generate a detected bandwidth signal, and a mode control circuit configured to control a mode of the envelope tracker based on the detected bandwidth signal, the mode control circuit further configured to disable the error amplifier when the detected bandwidth signal indicates that a bandwidth of the radio frequency signal is less than a first threshold.

2. The power amplifier system of claim 1 wherein the signal bandwidth detection circuit includes a root mean square detector configured to generate a detection signal indicative of a root mean square value of the envelope signal.

3. The power amplifier system of claim 2 wherein the signal bandwidth detection circuit further includes an envelope bandwidth to voltage converter configured to generate the detected bandwidth signal based on the detection signal.

4. The power amplifier system of claim 3 wherein the envelope bandwidth to voltage converter includes a cascade of a plurality of converter cells, the detected bandwidth signal based on a sum of a plurality of currents generated by the plurality of converter cells.

5. The power amplifier system of claim 1 wherein the envelope tracker and the DC-to-DC converter operate in parallel with one another to generate the power amplifier supply voltage when the detected bandwidth signal indicates that the bandwidth of the radio frequency signal is greater than a second threshold.

6. The power amplifier system of claim 5 wherein the mode control circuit is further configured to decrease a bias current of the error amplifier when the detected bandwidth signal indicates that the bandwidth of the radio frequency signal is greater than the first threshold but less than the second threshold.

7. The power amplifier system of claim 1 wherein the mode control circuit is further configured to process the detected bandwidth signal to determine a number of resource blocks used by the radio frequency signal.

8. A wireless device comprising:

a transceiver configured to generate a radio frequency signal and an envelope signal corresponding to an envelope of the radio frequency signal;

a power amplifier configured to provide amplification to the radio frequency signal and to receive power from a power amplifier supply voltage; and

an envelope tracker configured to generate the power amplifier supply voltage based on the envelope signal, the envelope tracker including a DC-to-DC converter, an error amplifier, a signal bandwidth detection circuit configured to generate a detected bandwidth signal, and a mode control circuit configured to control a mode of the envelope tracker based on the detected bandwidth signal, the mode control circuit further configured to disable the error amplifier when the detected bandwidth signal indicates that a bandwidth of the radio frequency signal is less than a first threshold.

9. The wireless device of claim 8 wherein the signal bandwidth detection circuit includes a root mean square detector configured to generate a detection signal indicative of a root mean square value of the envelope signal.

10. The wireless device of claim 9 wherein the signal bandwidth detection circuit further includes an envelope bandwidth to voltage converter configured to generate the detected bandwidth signal based on the detection signal.

11. The wireless device of claim 10 wherein the envelope bandwidth to voltage converter includes a cascade of a plurality of converter cells, the detected bandwidth signal based on a sum of a plurality of currents generated by the plurality of converter cells.

12. The wireless device of claim 8 further comprising an antenna configured to receive an amplified radio frequency signal from the power amplifier.

13. The wireless device of claim 8 wherein the envelope tracker and the DC-to-DC converter operate in parallel with one another to generate the power amplifier supply voltage when the detected bandwidth signal indicates that the bandwidth of the radio frequency signal is greater than a second threshold.

14. The wireless device of claim 13 wherein the mode control circuit is further configured to decrease a bias current of the error amplifier when the detected bandwidth signal indicates that the bandwidth of the radio frequency signal is greater than the first threshold but less than the second threshold.

15. The wireless device of claim 8 wherein the mode control circuit is further configured to process the detected bandwidth signal to determine a number of resource blocks used by the radio frequency signal.

16. A method of automatic mode control in an envelope tracking system, the method comprising:

amplifying a radio frequency signal using a power amplifier;

powering the power amplifier with a power amplifier supply voltage from an envelope tracker;

detecting a signal bandwidth of the radio frequency signal based on processing an envelope signal using a signal bandwidth detection circuit of the envelope tracker, the envelope signal corresponding to an envelope of the radio frequency signal;

controlling a mode of the envelope tracker based on the detected signal bandwidth using a mode control circuit of the envelope tracker; and

disabling an error amplifier when the detected signal bandwidth is less than a first threshold, and operating a DC-to-DC converter and the error amplifier in parallel with one another to generate the power amplifier supply voltage when the detected signal bandwidth is greater than a second threshold.

17. The method of claim 16 further comprising generating a detection signal indicative of a root mean square value of the envelope signal, and converting the detection signal to voltage indicative of a number of resource blocks of the radio frequency signal.

18. The method of claim 16 further comprising controlling a filtering characteristic of a filter of the envelope tracker based on the detected bandwidth signal.

19. The method of claim 16 further comprising decreasing a bias current of the error amplifier when the detected signal bandwidth indicates that the bandwidth of the radio frequency signal is greater than the first threshold but less than the second threshold.

20. The method of claim 16 wherein detecting the signal bandwidth includes generating a detection signal indicative of a root mean square value of the envelope signal, processing the detection signal using a plurality of converter cells arranged in a cascade, and summing a plurality of currents from the plurality of converter cells.