PSEUDO-ENVELOPE FOLLOWER POWER MANAGEMENT SYSTEM WITH HIGH FREQUENCY RIPPLE CURRENT COMPENSATION

• US 20120313701A1
• Filed: 12/09/2011
• Published: 12/13/2012
• Est. Priority Date: 04/19/2010
• Status: Active Grant

• Current Assignee: Qorvo US, Inc. (Qorvo, Inc.)
• Original Assignee: RF Micro Devices Incorporated (Qorvo, Inc.)
• Inventors: Khlat, Nadim, Kay, Michael R., Gorisse, Philippe
• Granted Patent: US 8,633,766 B2
• Time in Patent Office: Days
• US Class Current: 330/127
• CPC Class Codes: H02M 3/07 using capacitors charged and discharged alternately by semiconductor devices with control electrode , e.g. charge pumps
• CPC Class Codes: H03F 1/0244 Stepped control
• CPC Class Codes: H03F 1/025 by using a signal derived from the input signal
• CPC Class Codes: H03F 1/0277 Selecting one or more amplifiers from a plurality of amplifiers
• CPC Class Codes: H03F 1/42 Modifications of amplifiers to extend the bandwidth
• CPC Class Codes: H03F 2200/102 A non-specified detector of a signal envelope being used in an amplifying circuit
• CPC Class Codes: H03F 2200/204 A hybrid coupler being used at the output of an amplifier circuit
• CPC Class Codes: H03F 2200/36 the amplifier comprising means for increasing the bandwidth
• CPC Class Codes: H03F 2200/375 Circuitry to compensate the offset being present in an amplifier
• CPC Class Codes: H03F 2200/451 the amplifier being a radio frequency amplifier
• CPC Class Codes: H03F 2200/555 A voltage generating circuit being realised for biasing different circuit elements
• CPC Class Codes: H03F 2200/78 A comparator being used in a controlling circuit of an amplifier
• CPC Class Codes: H03F 2203/45526 the FBC comprising a resistor-capacitor combination and being coupled between the LC and the IC
• CPC Class Codes: H03F 2203/45544 the IC comprising one or more capacitors, e.g. coupling capacitors
• CPC Class Codes: H03F 2203/45594 the IC comprising one or more resistors, which are not biasing resistor
• CPC Class Codes: H03F 2203/45694 the LC comprising more than one shunting resistor
• CPC Class Codes: H03F 2203/45712 the LC comprising a capacitor as shunt
• CPC Class Codes: H03F 2203/45718 the LC comprising a resistor as shunt
• CPC Class Codes: H03F 2203/7221 the gated amplifier being switched on or off by a switch at the output of the amplifier
• CPC Class Codes: H03F 3/195 in integrated circuits
• CPC Class Codes: H03F 3/245 : with semiconductor devices only
• CPC Class Codes: H03F 3/3022 : CMOS common source output SEPP amplifiers H03F3/3008 takes precedence
• CPC Class Codes: H03F 3/45475 : using IC blocks as the active amplifying circuit
• CPC Class Codes: H03F 3/505 : with field-effect devices
• CPC Class Codes: H03F 3/72 : Gated amplifiers, i.e. amplifiers which are rendered operative or inoperative by means of a control signal

Abstract

Embodiments disclosed in the detailed description relate to a pseudo-envelope follower power management system including a parallel amplifier and a switch mode power supply converter cooperatively coupled to generate a power supply voltage at a power supply output coupled to a linear RF power amplifier. The parallel amplifier output is in communication with the power amplifier supply output. The parallel amplifier governs operation of the switch mode power supply converter and regulates the power amplifier supply voltage base on a V_RAMP signal. The parallel amplifier circuit includes an open loop high frequency compensation assist circuit that generates a high frequency ripple compensation current based on an estimate of the high frequency ripple currents contained in a ripple current of the power inductor. The high frequency ripple compensation current is injected into the parallel amplifier circuit output to cancel out high frequency ripple currents at the power amplifier supply output.

Claims

1. A pseudo-envelope follower power management system with high frequency ripple compensation comprising:

a switch mode power supply converter configured to;

generate a switching output voltage; and

generate a switching voltage output estimate which provides an early indication of a future voltage level of the switching output voltage;

an open loop high frequency ripple compensation assist circuit configured to;

receive the switching voltage output estimate and a V_RAMP signal;

generate a high frequency ripple compensation current based on the switching voltage output estimate and the V_RAMP signal; and

apply the high frequency ripple compensation current to a power amplifier supply output to reduce a high frequency ripple current at the power amplifier supply output.

2. The pseudo-envelope follower power management system with high frequency ripple compensation of claim 1 wherein the high frequency ripple compensation current is generated in a frequency band located substantially near a transmit to receive duplex offset for a band of operation in a communication network.

3. The pseudo-envelope follower power management system with high frequency ripple compensation of claim 2 wherein the frequency band of the high frequency ripple compensation current has a bandwidth substantially equal to a bandwidth of a receiver channel frequency band for the band of operation.

4. The pseudo-envelope follower power management system with high frequency ripple compensation of claim 2 wherein the switch mode power supply converter includes programmable delay circuitry configured to delay generation of the switching voltage output estimate by a programmable delay period.

5. The pseudo-envelope follower power management system with high frequency ripple compensation of claim 4 wherein the programmable delay period is configured to temporally align the switching voltage output estimate and the V_RAMP signal to position a notch in a ripple rejection response of the power amplifier supply output near the transmit to receive duplex offset for the band of operation.

6. The pseudo-envelope follower power management system with high frequency ripple compensation of claim 1 wherein the open loop high frequency ripple compensation assist circuit is further configured to generate a scaled high frequency ripple compensation current estimate based on the high frequency ripple compensation current.

7. The pseudo-envelope follower power management system with high frequency ripple compensation of claim 6 wherein the switch mode power supply converter is further configured to receive a feedback signal, wherein the feedback signal is based on the scaled high frequency ripple compensation current estimate.

8. The pseudo-envelope follower power management system with high frequency ripple compensation of claim 7 wherein the switch mode power supply converter is further configured to adjust the switching output voltage based on the feedback signal.

9. The pseudo-envelope follower power management system with high frequency ripple compensation of claim 8 further comprising a parallel amplifier configured to;

receive the V_RAMP signal and a power amplifier supply voltage from the power amplifier supply output, wherein the parallel amplifier is configured to generate a parallel amplifier output current based on a difference between the V_RAMP signal and the power amplifier supply voltage; and

apply the parallel amplifier output current to the power amplifier supply output.

10. The pseudo-envelope follower power management system with high frequency ripple compensation of claim 9 wherein the parallel amplifier is further configured to generate a scaled parallel amplifier output current estimate based on the parallel amplifier output current;

and

wherein the feedback signal is further based on the scaled parallel amplifier output current estimate.

11. The pseudo-envelope follower power management system with high frequency ripple compensation of claim 1 wherein the open loop high frequency ripple compensation assist circuit further comprises:

a filter network having a first node configured to receive the switching voltage output estimate and a second node;

a feedback network including a first node in communication with the second node of the filter network and a second node;

an operational amplifier including a non-inverting input configured to receive the V_RAMP signal, an inverting input in communication with the second node of the filter network and the first node of the feedback network, an operational amplifier output in communication with the second node of the feedback network, wherein the operational amplifier is configured to generate the high frequency ripple compensation current.

12. The pseudo-envelope follower power management system with high frequency ripple compensation of claim 11 wherein the operational amplifier includes a first push-pull output stage in communication with the operational amplifier output, wherein the first push-pull output stage is configured to generate an operational amplifier output current.

13. The pseudo-envelope follower power management system with high frequency ripple compensation of claim 12 wherein the open loop high frequency ripple compensation assist circuit further comprises:

a bias capacitor having a bias capacitance and a bias resistor arranged in series between the operational amplifier output and a reference voltage;

wherein the first push-pull output stage has a first stage transconductance; and

wherein the bias capacitance is configured such that the first stage transconductance of the first push-pull output stage is substantially equal to a transconductance of the bias resistor in a frequency band located substantially near a transmit to receive duplex offset for a band of operation in a communication network.

14. The pseudo-envelope follower power management system with high frequency ripple compensation of claim 12 wherein the open loop high frequency ripple compensation assist circuit further comprises:

an operational amplifier output isolation circuit including a high impedance input in communication with the operational amplifier output and an isolated feedback node in communication with the second node of the feedback network.

15. The pseudo-envelope follower power management system with high frequency ripple compensation of claim 11 wherein the operational amplifier is further configured to generate a scaled high frequency ripple compensation current estimate as a function of the high frequency ripple compensation current.

16. The pseudo-envelope follower power management system with high frequency ripple compensation of claim 12 wherein the operational amplifier further includes a second push-pull output stage configured to generate the high frequency ripple compensation current, wherein the high frequency ripple compensation current is mirrored to the operational amplifier output current.

17. The pseudo-envelope follower power management system with high frequency ripple compensation of claim 16 wherein the operational amplifier further includes a third push-pull output stage configured to generate a scaled high frequency ripple compensation current estimate as a function of the high frequency ripple compensation current based on a sense scaling factor.

18. The pseudo-envelope follower power management system with high frequency ripple compensation of claim 16 wherein the second push-pull output stage includes a programmable second output stage transconductance.

19. The pseudo-envelope follower power management system with high frequency ripple compensation of claim 18 wherein the open loop high frequency ripple compensation assist circuit is configured to adjust a magnitude of the high frequency ripple compensation current based on the programmable second output stage transconductance.

20. The pseudo-envelope follower power management system with high frequency ripple compensation of claim 19 wherein the programmable second output stage transconductance is a substantially linear function of a programmable transconductance parameter.

21. The pseudo-envelope follower power management system with high frequency ripple compensation of claim 11 wherein the filter network is associated with a first corner frequency and the feedback network is associated with a second corner frequency;

and

wherein the first corner frequency has a programmable range between 3 MHz and 11.5 MHz and the second corner frequency has a programmable range between 3 MHz and 11.5 MHz.

22. The pseudo-envelope follower power management system with high frequency ripple compensation of claim 21 wherein the first corner frequency is substantially equal to 6 MHz, and the second corner frequency is substantially equal to 6 MHz.

23. The pseudo-envelope follower power management system with high frequency ripple compensation of claim 1, wherein the switch mode power supply converter is configured to operate as a buck converter.

24. The pseudo-envelope follower power management system with high frequency ripple compensation of claim 1, wherein the switch mode power supply converter is configured to operate as a multi-level charge pump buck converter.

25. The pseudo-envelope follower power management system with high frequency ripple compensation of claim 1 wherein the switch mode power supply converter further includes programmable delay circuitry, a switcher control circuit, and a buffer scalar;

wherein the switcher control circuit is configured to generate a digital switching voltage output signal that represents a state of the switcher control circuit used to control generation of the switching output voltage by the switch mode power supply converter;

wherein the programmable delay circuitry is configured to receive the digital switching voltage output signal, and delay the digital switching voltage output signal by a programmable delay period to generate a delayed digital switching voltage output signal; and

wherein the buffer scalar is configured to receive the delayed digital switching voltage output signal, and generate the switching voltage output estimate based on the delayed digital switching voltage output signal and the buffer scalar.

26. A method for reducing high frequency ripple currents at a power amplifier supply output comprising:

generating a switching output voltage and a switching voltage output estimate with a switch mode power supply converter, wherein the switching voltage output estimate provides an early indication of a future voltage level of the switching output voltage;

receiving the switching voltage output estimate and a V_RAMP signal at an open loop high frequency ripple compensation assist circuit;

generating a high frequency ripple compensation current based on the switching voltage output estimate and the V_RAMP signal; and

applying the high frequency ripple compensation current to the power amplifier supply output to reduce a high frequency ripple current at the power amplifier supply output.

27. The method for reducing high frequency ripple currents at the power amplifier supply output of claim 26 wherein generating the high frequency ripple compensation current based on the switching voltage output estimate and the V_RAMP signal comprises:

generating the high frequency ripple compensation current within a frequency band located substantially near a transmit to receive duplex offset for a band of operation in a communication network.

28. The method for reducing high frequency ripple currents at the power amplifier supply output of claim 27 wherein the frequency band of the high frequency ripple compensation current has a bandwidth substantially equal to a bandwidth of a receiver channel frequency band for the band of operation.

29. The method for reducing high frequency ripple currents at the power amplifier supply output of claim 28 wherein generating the switching voltage output estimate further comprises:

delaying generation of the switching voltage output estimate by a programmable delay period to temporally align the switching voltage output estimate and the V_RAMP signal to position a notch in a ripple rejection response of the power amplifier supply output near the transmit to receive duplex offset for the band of operation.

30. The method for reducing high frequency ripple currents at the power amplifier supply output of claim 29 further comprising:

generating a scaled high frequency ripple compensation current estimate based on the high frequency ripple compensation current.

31. The method for reducing high frequency ripple currents at the power amplifier supply output of claim 30 further comprising:

forming a feedback signal based on the scaled high frequency ripple compensation current estimate;

providing the feedback signal to the switch mode power supply converter; and

adjusting the switching output voltage based on the feedback signal.

32. The method for reducing high frequency ripple currents at the power amplifier supply output of claim 26, wherein the switch mode power supply converter is configured to be a buck converter.

33. The method for reducing high frequency ripple currents at the power amplifier supply output of claim 26, wherein the switch mode power supply converter is configured to be a multi-level charge pump buck converter.