Classifications

• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03F—AMPLIFIERS
  • H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
  • H03F1/02—Modifications of amplifiers to raise the efficiency, e.g. gliding Class A stages, use of an auxiliary oscillation
  • H03F1/0205—Modifications of amplifiers to raise the efficiency, e.g. gliding Class A stages, use of an auxiliary oscillation in transistor amplifiers
  • H03F1/0211—Modifications of amplifiers to raise the efficiency, e.g. gliding Class A stages, use of an auxiliary oscillation in transistor amplifiers with control of the supply voltage or current
  • H03F1/0216—Continuous control
  • H03F1/0233—Continuous control by using a signal derived from the output signal, e.g. bootstrapping the voltage supply
  • H03F1/0238—Continuous control by using a signal derived from the output signal, e.g. bootstrapping the voltage supply using supply converters
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03F—AMPLIFIERS
  • H03F2200/00—Indexing scheme relating to amplifiers
  • H03F2200/102—A non-specified detector of a signal envelope being used in an amplifying circuit
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03F—AMPLIFIERS
  • H03F2200/00—Indexing scheme relating to amplifiers
  • H03F2200/435—A peak detection being used in a signal measuring circuit in a controlling circuit of an amplifier

Definitions

• the disclosure relates to envelope tracking for power amplifiers.
• Envelope tracking is a technique for increasing the efficiency of power amplifiers.
• the supply voltage of a power amplifier is dynamically adjusted to keep the power amplifier operating with sufficient headroom to maintain linearity, while nevertheless minimizing DC power consumption.
• the supply voltage of the power amplifier may be generated using a separate linear amplifier that tracks the envelope of the power amplifier output.
• the linear amplifier is itself coupled to an amplifier supply voltage generated by a boost converter, which is capable of generating a boosted supply voltage for the linear amplifier that exceeds the maximum supply voltage otherwise available to the system, e.g., a battery voltage. In this manner, the power amplifier output can reach and even exceed the battery voltage when necessary.
• the boost converter may generate a boosted supply voltage for the linear amplifier only when necessary to provide sufficient headroom to the power amplifier.
• a bypass mode may be provided in which the battery voltage is directly coupled to the amplifier as the amplifier supply voltage.
• FIG 1 illustrates an implementation of an envelope tracking (ET) system.
• ET envelope tracking
• FIG 2 illustrates an implementation of an ET system wherein Ven and Vtarget are generated using Vamp as an input.
• FIG 3 illustrates an exemplary embodiment of the enable generation block according to the present disclosure.
• FIG 4 illustrates an exemplary embodiment of a timer logic block which generates the enable voltage Ven from the voltage Pk_detect.
• FIG 5 illustrates exemplary signal timing diagrams corresponding to the timer logic block implementing the method shown in FIG 4.
• FIG 6 illustrates an exemplary embodiment of a target generation block according to the present disclosure.
• FIG 7 illustrates an exemplary embodiment of a method according to the present disclosure.
• FIG 8 illustrates an alternative exemplary embodiment of the present disclosure, wherein a buck converter is further coupled to Vamp.
• TRUE e.g., 1
• FALSE e.g., 0
• FIG 1 illustrates an implementation of an envelope tracking (ET) system 100.
• ET envelope tracking
• FIG 1 is shown for illustrative purposes only, and is not meant to limit the scope of the present disclosure to any particular implementation of an ET system.
• the techniques described hereinbelow may readily be applied to systems incorporating alternative or additional modules not shown in FIG 1, such as a buck converter coupling Vbatt to Vamp for generating a stepped-down voltage supply for the power amplifier.
• a power amplifier (PA) 130 receives an input voltage IN and generates an amplified output voltage OUT.
• a voltage Vamp also denoted a “tracking supply voltage”
• Vamp is generated at least in part by an amplifier 140.
• the amplifier 140 is supplied by a voltage VDD_Amp, also denoted an "amplifier supply voltage.”
• VDD_Amp also denoted an "amplifier supply voltage.”
• the amplifier 140 may amplify a voltage Env which tracks the envelope of the PA output voltage OUT.
• Note amplifier 140 may generally be any type of amplifier known in the art, e.g., class A, class B, class AB, etc. Such exemplary embodiments are contemplated to be within the scope of the present disclosure.
• the tracking supply voltage Vamp provided to the PA 130 may be maintained at a level sufficient to ensure linear operation of the PA 130, i.e., provided with sufficient "headroom," while reducing unnecessary DC power consumption.
• a buck converter (not shown) may be concurrently provided to supply the PA 130, e.g., coupled to the PA 130 at Vamp to increase the power driving capability of the PA 130.
• Vbatt may also be denoted herein as a "boost supply voltage.”
• boost converter 110 may be provided to generate VDD_Amp.
• the boost converter 110 may boost VDD_Amp to a higher level than Vbatt according to principles of operation not shown in FIG 1 but known in the art, e.g., using a plurality of switches alternately configured to charge and discharge an inductor to generate a boosted output voltage.
• the boost converter 110 may be turned on or enabled only when necessary, e.g., when it is determined that VDD_Amp needs to rise above Vbatt to maintain sufficient headroom for the PA 130.
• the boost converter 110 may receive as input an "enable" signal voltage Ven indicating when VDD_Amp should be boosted to a level higher than VBatt, i.e., when the boost converter 110 should be enabled or turned on.
• the event corresponding to Ven signaling that the boost converter 110 should be enabled may also be denoted the event of an "enable signal" being "turned on.”
• the boost converter 110 may also be provided with a target voltage Vtarget indicating the level to which VDD_Amp should be boosted when the boost converter 110 is enabled. It will be appreciated that when it is not necessary to provide VDD_Amp higher than Vbatt, the boost converter 110 may be turned off or disabled, or otherwise provided in a "bypass" mode that directly couples Vbatt to VDD_Amp.
• FIG 2 illustrates an implementation of an ET system 200 wherein Ven and Vtarget are generated using Vamp as an input. Note FIG 2 is shown for illustrative purposes only, and is not meant to limit the scope of the present disclosure to any particular techniques for generating Ven and/or Vtarget.
• an enable generation block 210 is coupled to Vamp to generate the enable voltage Ven.
• a target generation block 220 is coupled to Vamp to generate the target voltage Vtarget.
• FIG 2 is shown for illustrative purposes only, and is not meant to limit the scope of the present disclosure to ET systems wherein Ven and Vtarget are necessarily generated as shown.
• Vtarget may be generated from Vamp as shown in FIG 2, while Ven may be generated using other techniques known in the art (e.g., independently of Vamp, and/or using software-based event-driven techniques); similarly Ven may be generated from Vamp, and Vtarget generated using other techniques.
• Such alternative implementations are contemplated to be within the scope of the present disclosure.
• FIG 3 illustrates an exemplary embodiment 210.1 of the enable generation block 210 according to the present disclosure. Note FIG 3 is shown for illustrative purposes only, and is not meant to limit the scope of the present disclosure to exemplary embodiments incorporating the techniques shown.
• Vamp is coupled to a peak detector 320 configured to detect the peak value in Vamp over a first predetermined time window, e.g., TWIN1.
• the detected peak value in Vamp is output as a voltage Pk_Vampl, also denoted herein as an "enable peak.”
• a programmable headroom block 310 generates a predetermined headroom voltage HR_1, or a "first headroom voltage.”
• HR_1 may be a static value, or it may correspond to the contents of a register (not shown) that may be dynamically written to using, e.g., a microprocessor, etc. (not shown in FIG 3).
• An adder 330 adds Pk_Vampl to HR_1 to generate a signal 330a, which is coupled to the positive (+) input of a comparator 340.
• a negative (-) input of the comparator 340 is coupled to Vbatt.
• the comparator 340 generates an output voltage Pk_detect.
• Pk_detect provides an indication of whether the peak value Pk_Vampl of Vamp plus a headroom voltage HR_1 exceeds the voltage Vbatt. If Pk_detect is high, then, to provide sufficient headroom to the PA 130, the boost converter 110 should be enabled to generate a VDD_Amp higher than Vbatt.
• timer logic block 350 which generates the enable voltage Ven from the voltage Pk_detect.
• the operation of the timer logic block 350 is described with reference to the method 400 of FIG 4. Note the method 400 is shown for illustrative purposes only, and is not meant to limit the scope of the present disclosure to exemplary embodiments of timer logic blocks necessarily incorporating the method shown.
• Ven is initially set to 0, corresponding to the boost converter 110 being disabled, or being configured in a bypass mode.
• Ven is set to 1.
• the boost converter 110 may be enabled when Ven is set to 1, e.g., to boost VDD_Amp to a level higher than Vbatt.
• TON is denoted an "enable on duration,” and may be a preprogrammed duration, e.g., corresponding to the contents of a register (not shown) that may be written to using, e.g., a microprocessor, etc. (not shown in FIG 4).
• TON may proceed back to block 410, wherein Ven may again be set to 0.
• the duration of TON may be measured out using a counter (not shown) driven by a clock having a predetermined frequency.
• a counter not shown
• a clock having a predetermined frequency
• FIG 5 illustrates exemplary signal timing diagrams corresponding to the timer logic block 350 implementing the method 400. Note FIG 5 is shown for illustrative purposes only, and is not meant to restrict the scope of the present disclosure to signals having the specific timing relationships shown.
• Pk_detect is seen to transition from low to high. This may correspond to, e.g., the voltage 330a in FIG 3 transitioning from being less than Vbatt prior to tO to being greater than Vbatt at tO.
• Ven is seen to transition from low to high, in response to Pk_detect transitioning high.
• Ven is seen to remain high until a time t2, when Ven transitions from high to low.
• the duration between tO and t2 may correspond to the enable on duration TON previously described hereinabove with reference to block 440 of FIG 4.
• Ven transitions from low to high at tO in response to detecting Pk_detect being high, and Ven stays high for a duration TON before returning to low.
• Ven stays high following the rising edge of Pk_detect regardless of any transitioning in Pk_detect between tO and t2, e.g., Ven stays high when a falling edge of Pk_detect occurs at tl.
• adder 330 may function continuously to assess whether Ven needs to be asserted high, regardless of the on-off state of the boost converter 110.
• the enable on duration TON is a parameter that may be re-programmed by writing into the contents of an "enable on duration" register (not shown).
• the enable on interval may be chosen to start or stop based on other events.
• the enable on interval may commence on a rising edge of Pk_detect, and persist until a duration TON' after a falling edge in Pk_detect, i.e., the enable on interval may last for a duration of tl - tO + TON'.
• FIG 6 illustrates an exemplary embodiment 220.1 of a target generation block 220 according to the present disclosure. Note FIG 6 is shown for illustrative purposes only, and is not meant to limit the scope of the present disclosure to exemplary embodiments incorporating the techniques shown.
• Vamp is coupled to a peak detector 620 configured to detect the peak value in Vamp over a second predetermined time window, e.g., TWIN2.
• TWIN2 employed by peak detector 620 of the target generation block 220.1 may generally be independent of the time window TWIN1 employed by peak detector 320 of the enable generation block 210.1, i.e., the peak detection time windows used for enable and target generation may be different from each other. In certain alternative exemplary embodiments, however, the time windows may be the same. All such alternative exemplary embodiments are contemplated to be within the scope of the present disclosure.
• the output Pk_Vamp2, also denoted herein as a "target peak,” of peak detector 620 is coupled to an adder 630, which adds Pk_Vamp2 with a headroom voltage HR_2, or "second headroom voltage,” generated by a programmable headroom block 610, to generate Vtarget.
• HR_2 generated by block 610 may be independent of HR_1 generated by programmable headroom block 310 of the enable generation block 210.1, i.e., the headroom voltages used for enable and target generation may generally be independent from each other. In certain alternative exemplary embodiments, however, the headroom voltages may be the same. All such alternative exemplary embodiments are contemplated to be within the scope of the present disclosure.
• the output of adder 630 may be provided as the target voltage Vtarget for the boost converter 110.
• FIG 7 illustrates an exemplary embodiment of a method 700 according to the present disclosure. Note FIG 7 is shown for illustrative purposes only and is not meant to limit the scope of the present disclosure to any particular exemplary embodiment of a method described.
• an amplifier supply voltage configurable to be higher than a boost supply voltage is generated.
• an enable signal is turned on in response to detecting that a sum of a first headroom voltage and an enable peak of a tracking supply voltage is greater than the amplifier supply voltage.
• a target voltage comprising the sum of a second headroom voltage and a target peak of the tracking supply voltage is generated.
• the amplifier supply voltage is driven to the target voltage in response to the enable signal being turned on.
• FIG 8 illustrates an alternative exemplary embodiment 800 of the present disclosure, wherein a buck converter is further coupled to Vamp. Note FIG 8 is shown for illustrative purposes only, and is not meant to limit the scope of the present disclosure to exemplary embodiments incorporating a buck converter. Further note that similarly labeled elements in FIGs 2 and 8 may correspond to elements performing similar functionality, unless otherwise noted.
• a buck converter 810 is coupled to the tracking supply voltage Vamp of PA 130.
• the buck converter 810 may convert Vbatt to a level of Vamp lower than Vbatt when necessary.
• the buck converter 810 may generate a level of Vamp less than Vbatt according to principles of operation not shown in FIG 1 but known in the art, e.g., using a plurality of switches alternately configured to charge and discharge an inductor to generate a stepped-down output voltage.
• the buck converter 810 may supply, e.g., the low-frequency content of the power supply to the PA 130, while the amplifier 140 may supply higher- frequency content of the power supply to the PA 130 arising from, e.g., fluctuations in the envelope of the PA output voltage.
• DSP Digital Signal Processor
• ASIC Application Specific Integrated Circuit
• FPGA Field Programmable Gate Array
• a general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine.
• a processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.
• a software module may reside in Random Access Memory (RAM), flash memory, Read Only Memory (ROM), Electrically Programmable ROM (EPROM), Electrically Erasable Programmable ROM (EEPROM), registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.
• An exemplary storage medium is coupled to the processor such that the processor can read information from, and write information to, the storage medium.
• the storage medium may be integral to the processor.
• the processor and the storage medium may reside in an ASIC.
• the ASIC may reside in a user terminal.
• the processor and the storage medium may reside as discrete components in a user terminal.
• the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium.
• Computer-readable media includes both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another.
• a storage media may be any available media that can be accessed by a computer.
• such computer- readable media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer.
• any connection is properly termed a computer-readable medium.
• the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave
• the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium.
• Disk and disc includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and Blu-Ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.

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• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Dc-Dc Converters (AREA)
• Amplifiers (AREA)
• Elevator Control (AREA)

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• 2012
  • 2012-10-24 US US13/659,667 patent/US8754707B2/en active Active
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