PROTECTION CIRCUIT FOR POWER AMPLIFIER

• US 20110043956A1
• Filed: 03/01/2010
• Published: 02/24/2011
• Est. Priority Date: 08/19/2009
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Su, Wenjun, Hadjichristos, Aristotele, Cassia, Marco, Sahota, Gurkanwal S.
• Granted Patent: US 9,559,639 B2
• Time in Patent Office: Days
• US Class Current: 361/86
• CPC Class Codes: H03F 1/52 Circuit arrangements for protecting such amplifiers monitoring arrangements G01R31/28; increasing reliability in communication systems, e.g. using redundancy H04B1/74
• CPC Class Codes: H03F 2200/435 A peak detection being used in a signal measuring circuit in a controlling circuit of an amplifier
• CPC Class Codes: H03F 2200/78 A comparator being used in a controlling circuit of an amplifier
• CPC Class Codes: H03F 3/24 of transmitter output stages
• CPC Class Codes: H03G 3/3042 in modulators, frequency-changers, transmitters or power amplifiers transmission power control in bidirectional transmission systems H04W52/04
• CPC Class Codes: H04B 2001/0408 with power amplifiers

Abstract

Techniques for protecting a power amplifier (PA) are described. In an exemplary design, an apparatus includes (i) a PA module to amplify an input RF signal and provide an output RF signal and (ii) a protection circuit to control a transmitter gain to protect the PA module against high peak voltage. In an exemplary design, the protection circuit includes a set of comparators to quantize an analog input signal and provide digital comparator output signals used to adjust the transmitter gain. In another exemplary design, the protection circuit reduces and increases the transmitter gain with hysteresis. In yet another exemplary design, the protection circuit has faster response to rising amplitude than falling amplitude of the output RF signal. The hysteresis and/or the different rise and fall responses may allow the protection circuit to avoid toggling the transmitter gain under severe load mismatch and to handle time-varying envelope due to amplitude modulation.

Claims

1. An apparatus comprising:

a power amplifier (PA) module to receive an input radio frequency (RFin) signal and provide an output RF (RFout) signal; and

a protection circuit coupled to the PA module and to control a transmitter gain to protect the PA module against high peak voltage of the RFout signal, the protection circuit comprises a plurality of comparators to receive an analog input signal obtained based on the RFout signal, to quantize the analog input signal, and to provide a plurality of digital comparator output signals used to adjust the transmitter gain.

2. The apparatus of claim 1, each of the plurality of comparators receives the analog input signal at a first input, receives one of a plurality of reference voltages at a second input, and provides one of the plurality of comparator output signals.

3. The apparatus of claim 1, the protection circuit further comprises a control circuit to generate at least one control signal with hysteresis based on the plurality of comparator output signals, the at least one control signal is used to adjust the transmitter gain.

4. The apparatus of claim 3, the plurality of comparator output signals comprise at least one comparator output signal and a designated comparator output signal, the at least one control signal has leading edges determined by the at least one comparator output signal and falling edges determined by the designated comparator output signal.

5. The apparatus of claim 1, the protection circuit further comprises a thermal-to-binary encoder to generate at least one gain control signal, used to adjust the transmitter gain, based on the plurality of comparator output signals.

6. The apparatus of claim 5, the at least one gain control signal is associated with at least one discrete gain value for the transmitter gain, and at most one of the at least one gain control signal is asserted to select at most one of the at least one discrete gain value.

7. The apparatus of claim 1, the protection circuit further comprises

a peak detector to receive a peak detector input signal obtained based on the RFout signal, to detect for peak voltage of the RFout signal based on the peak detector input signal, and to provide the analog input signal to the plurality of comparators.

8. The apparatus of claim 7, the analog input signal tracks rising amplitude of the RFout signal and lags falling amplitude of the RFout signal.

9. The apparatus of claim 1, the PA module comprises a driver amplifier coupled in series with a power amplifier, the transmitter gain comprises a gain of the driver amplifier, and the protection circuit controls the gain of the driver amplifier to protect the power amplifier against high peak voltage of the RFout signal.

10. An apparatus comprising:

a power amplifier (PA) module to receive an input radio frequency (RFin) signal and provide an output RF (RFout) signal; and

a protection circuit coupled to the PA module and to control a transmitter gain to protect the PA module against high peak voltage of the RFout signal, the protection circuit reduces the transmitter gain when amplitude of the RFout signal exceeds a high threshold and increases the transmitter gain when the amplitude of the RFout signal falls below a low threshold, the low threshold is below the high threshold to provide hysteresis.

11. The apparatus of claim 10, the protection circuit reduces the transmitter gain from a first gain value to a second gain value when the amplitude of the RFout signal exceeds the high threshold and further reduces the transmitter gain to a third gain value when the amplitude of the RFout signal exceeds a higher threshold, the higher threshold is above the high threshold.

12. The apparatus of claim 11, the protection circuit increases the transmitter gain from the second gain value or the third gain value to the first gain value when the amplitude of the RFout signal falls below the low threshold.

13. The apparatus of claim 10, the protection circuit comprises

a peak detector to detect for peak voltage of the RFout signal and to provide an output signal tracking rising amplitude of the RFout signal and lagging falling amplitude of the RFout signal, and the transmitter gain is increased or decreased based on the output signal from the peak detector.

14. The apparatus of claim 10, the protection circuit comprises

a plurality of comparators to receive an analog input signal obtained based on the RFout signal, to quantize the analog input signal based on a plurality of reference voltages, and to provide a plurality of comparator output signals, the plurality of reference voltages correspond to a plurality of thresholds including the high and low thresholds, and

a control circuit to generate at least one control signal with hysteresis based on the plurality of comparator output signals, the at least one control signal is used to adjust the transmitter gain.

15. The apparatus of claim 14, the plurality of comparator output signals comprise at least one comparator output signal and a designated comparator output signal generated based on the low threshold, the at least one control signal has leading edges determined by the at least one comparator output signal and falling edges determined by the designated comparator output signal.

16. The apparatus of claim 10, the RFout signal is amplitude modulated and has a time-varying envelope.

17. The apparatus of claim 10, the hysteresis avoids toggling of the transmitter gain between two gain values due to load mismatch at an output of the PA module.

18. An apparatus comprising:

a power amplifier (PA) module to receive an input radio frequency (RFin) signal and provide an output RF (RFout) signal; and

a protection circuit coupled to the PA module and to control a transmitter gain to protect the PA module against high peak voltage of the RFout signal, the protection circuit has faster response to rising amplitude than falling amplitude of the RFout signal.

19. The apparatus of claim 18, the protection circuit comprises

a peak detector to receive an input signal obtained based on the RFout signal, to detect for peak voltage of the RFout signal based on the input signal, and to provide an output signal tracking the rising amplitude of the RFout signal and lagging the falling amplitude of the RFout signal.

20. The apparatus of claim 19, the peak detector comprises

a first peak detector to receive the input signal and provide an intermediate signal tracking the rising and falling amplitude of the RFout signal, and

a second peak detector coupled to the first peak detector and to receive the intermediate signal and provide the output signal.

21. The apparatus of claim 20, the second peak detector has a charging current for detecting the rising amplitude of the RFout signal and a discharging current for detecting the falling amplitude of the RFout signal, the discharging current is at least one order of magnitude smaller than the charging current.

22. The apparatus of claim 18, the RFout signal is amplitude modulated, and the protection circuit tracks the rising amplitude of the RFout signal due to amplitude modulation and lags the falling amplitude of the RFout signal due to amplitude modulation.

23. A method of protecting a power amplifier (PA) module, comprising:

amplifying an input radio frequency (RFin) signal with the PA module to obtain an output RF (RFout) signal; and

controlling a transmitter gain to protect the PA module against high peak voltage of the RFout signal, the transmitter gain is adjusted based on a plurality of comparator output signals from a plurality of comparators, or is decreased and increased with hysteresis, or is adjusted based on faster response to rising amplitude than falling amplitude of the RFout signal, or a combination thereof.

24. The method of claim 23, the controlling the transmitter gain comprises

detecting for peak voltage of the RFout signal and providing a peak detector output signal tracking the rising amplitude of the RFout signal and lagging the falling amplitude of the RFout signal.

25. The method of claim 24, the detecting for peak voltage of the RFout signal comprises

detecting for the peak voltage of the RFout signal with a first peak detector to obtain an intermediate signal tracking the rising and falling amplitude of the RFout signal, and

detecting for peak voltage of the intermediate signal with a second peak detector to obtain the peak detector output signal.

26. The method of claim 23, the controlling the transmitter gain comprises

reducing the transmitter gain when the amplitude of the RFout signal exceeds a high threshold, and

increasing the transmitter gain when the amplitude of the RFout signal falls below a low threshold, the low threshold is below the high threshold to provide hysteresis.

27. The method of claim 23, the controlling the transmitter gain comprises

generating at least one control signal, used to adjust the transmitter gain, based on the plurality of comparator output signals, the plurality of comparator output signals comprise at least one comparator output signal and a designated comparator output signal, the at least one control signal has leading edges determined by the at least one comparator output signal and falling edges determined by the designated comparator output signal.

28. An apparatus comprising:

means for amplifying an input radio frequency (RFin) signal to obtain an output RF (RFout) signal; and

means for controlling a transmitter gain to protect the means for amplifying against high peak voltage of the RFout signal, the transmitter gain is adjusted based on a plurality of comparator output signals from a plurality of comparators, or is decreased and increased with hysteresis, or is adjusted based on faster response to rising amplitude than falling amplitude of the RFout signal, or a combination thereof.