GB2535178A - Switcher noise reduction - Google Patents

Switcher noise reduction Download PDF

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Publication number
GB2535178A
GB2535178A GB1502246.0A GB201502246A GB2535178A GB 2535178 A GB2535178 A GB 2535178A GB 201502246 A GB201502246 A GB 201502246A GB 2535178 A GB2535178 A GB 2535178A
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GB
United Kingdom
Prior art keywords
inductor
stage
terminal
circuit
switching
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
GB1502246.0A
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GB201502246D0 (en
Inventor
Cobley Kevin
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
SnapTrack Inc
Original Assignee
SnapTrack Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by SnapTrack Inc filed Critical SnapTrack Inc
Priority to GB1502246.0A priority Critical patent/GB2535178A/en
Publication of GB201502246D0 publication Critical patent/GB201502246D0/en
Priority to PCT/US2016/017520 priority patent/WO2016130785A1/en
Publication of GB2535178A publication Critical patent/GB2535178A/en
Withdrawn legal-status Critical Current

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Classifications

    • HELECTRICITY
    • H03ELECTRONIC CIRCUITRY
    • H03FAMPLIFIERS
    • H03F1/00Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
    • H03F1/02Modifications of amplifiers to raise the efficiency, e.g. gliding Class A stages, use of an auxiliary oscillation
    • H03F1/0205Modifications of amplifiers to raise the efficiency, e.g. gliding Class A stages, use of an auxiliary oscillation in transistor amplifiers
    • H03F1/0211Modifications 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
    • H03F1/0216Continuous control
    • H03F1/0222Continuous control by using a signal derived from the input signal

Abstract

A power supply for an RF PA stage 2 includes a switch-mode stage 10 and a correction stage 16 which both receive an input signal 32. The outputs of the switch-mode stage 10 and the correction stage 16 are combined in a combiner circuit 30, in which current from the switch mode stage 10 passes through an inductor 14. According to the invention, a shunt impedance 42 is connected to the output of the switching stage. The shunt impedance may be connected to either terminal of the combining inductor. The shunt impedance 42 substantially reduces high frequency components of the ripple current (figures 2 & 4). The shunt circuit 42 may be switched in and out of circuit to reduce noise when required.

Description

SWITCHER NOISE REDUCTION
BACKGROUND TO THE INVENTION:
S Field of the invion:
The present invention relates to power supplies incorporating switching stages, and particularly but not ezelusively to envelope traekinc: of supplies for radio frequency power amplifiers,
Description of Related ',Art:
An envelope tracking power suopiy for a radio frequency power amplifier is an example of a power supply. incorporating switches. The switches in a switching stage of such a onwer supply switch between different sup levels in order to generate an output power supply.
For efficient power supplies it is advantageous in at least some scenario5,, to minimise any noise associated with such switching: in order to avoid such noise being 20 present on the power supply itself, It is an aim of the present invention to reduce the switchinn not caused by switching in a swl.t.ched power supply.
SUMMARY OF THE INVENTION:
There is provided a power supply including a switching stage and a shunt network, the shunt network being connected to the output of the switching stage and config,,Eed to reduce the noise signal associated with the switching stage.
The shunt network may be configured to tej,,,ct high frequency signals in the output signal of the switching stage, The shunt. network may be a shunt impedance_ The power supply may further comprise a switch for connecting the shunt network to electrical ground The swiLcll may be controlled, to be closed when noise reduction is required, and. open when noise reduction not regulired, The power supply may further include a correction stage and a combiner, the combiner for combining the putouts of the switching stage and the correction stage to generate a supply voltage, the combiner comprising a combining inductor my-inn a fl-et tc,rmihal for receiving 15 the output of the switching stage and a second terminal providing the power supply output, the shunt network. being connected. to either the first or the second terminal, of the combining:inductor.
The power supply may further comprise an isPlatind inductor, the first terminal of the combining inductor being connected to the output of the switching stage, and the second terminal of the combining inductor being connectect to the power supply nutput via the isolating inductor.
The power supply may further comprise an isolating inductor, the second terminal of the combining inductor oroviding the combiner output, and the iFolafinci innuctor being connected between the first terminal of the combining inductor and the switching stage output.
CL
The shunt network may comprise a series connected capacitor and resistor arrangement, the arrangement having a first terminal connected to the second terminal of the combining inductor and a. second terminal connected to electrieal uround.
The combiner Mc-1y lurthe, comprise a. capacitor connected between an output of the correction stage and the output of the power. supply, BRIEF DSCRIPTION OF THE FIGURES: The invention is described by way of reference to the accompanying figures, in which: rin., I i).1Cqi-r;ftea: an exemplary envelope tracking IS power supply for an. RE FIG, 2 illustrates the niople current cue to switching. noise in the exemplary envelooe tr;L:ckima modulator of FIG, 1; FTG, 3 illustrates an improvement to the exemplary 20 envelope tracking modulator power supply of FIG, 1; FIG. 4 illustrates the ripple current due to switching noise in the improved envelcoe tracking modulator of FIG, 3; FIG, 5 illustrates a modification to the improved exemplary envelope tracking modulator power supply of FIG 3: and FIG. 6 illustrates an alternative improvomenr to the exemplary tracking modulator of FIG. I.
DESCRIPTION OF PREFERRED EMBODIMENTS:
The invention is now described with reference to particular examples and with reference in particular to an exam).)le of a switch.ed power supply stage of an envelope tracking modulated power supply for a radio frequency amplifier. The invention is nbt limdted to such an example implementation, With reference to FIG, 1 a. power supply stage 28 D provides a modulated supply voltage online 8 to a power amplifier (PA) 2. The PA. 2 receives a radio frequency RE) input signal on -ing, 4 and generates an RE output bignal on line 6. The power supply stage 28 tracks the envelope of anR,,Z input signal on line 4 to be amplified 10 in order to provide an efficient modulated power supply on line 8 to the PA 2.
The power supply at ape 28 includes a switching stage 10, a correction stage 16, and a combiner 30 including an inductor 14 and a capacitor 26, The switching stage 1.0 generates a switched voltage output signal on line 12, Line 12 is connected to a first terminal of the inductor 14, The second terminal of the inductor 14 is connected to the output. line 8, The correction stage 16, which includes a correction amplifier 18, generates a correction voltage on line 24. Line 24 is connected CO a. first terminal of the capacitor 26. The second terminal of the capacitor 26 is connected to the output line 8. The inductor 14 and capacitor 26 together.. form the combiner 30 which combines the output voltages from the switching stage and the correction stage to produce the modulated supply voltage on line 8, The correction amplifier 18 has a feedback connection line 34 connecting. its output to a first illpuL. The correction stage has a second input connected to receive as reference signal on line 32. The correction amplifier compares the feedback signal on 'Line 34 to the reference signal in order to generate the correction. signal, The reference signal on line 32 represents a desired output signal, The reference signal is additionally provided to the switching stage 10.
The switching star 10 produces an output switching current, or ripple current, at the switching frequencies of the switches in the switching stage 10, This current is converted to switching voltage noise by the combiner 33 when dLivinu a resistive load such as a PA 2. This noise is undesirable, particularly in the amplification of low level signals_ FIG-2 illustrates a plot of the switching noise signal, being a plot of the ripple current against. time. The plot 3 is a plot of riv.T1P current versus time, the ripple current. being the current due to switching which flows in the inductor 14. The ripple current is undesirable, The ripple current has distortions at each maxima and minima, as illustrated by reference numerals, FIG, 2 illustrates a plot of only the unwanted noise signaU in addition there is a wanted signal.
FIG. 3 illustrates a modified modulated power supply 20 stage 40. Where elements shown correspond. to elements shown in the previous figure like reference numerals are used, A circuit 42 Is connected at the second terminal of the inductor 14. The circuit 42 includes a. capacitor. 44 having a first terminal connected to the second terminal of the inductor 14, A resistor $6 has a. first terminal connected to the second terminal ofthe capacitor 44. A. switch 48 is connected between the second. terminal of the resistor 46 and electrical ground.
Thr circuit. 42 is an anti-ricnie circuit which acts to reduce the ripple current in the current flowing through the inductor 14, An inductor 40 is connected between the second terminal, of the inductor 14 and the output on line 29, having a first terminal connected to the second terminal of the inductor 14 and a second terminal connected to the 5 output on line 2. The second terminal of the inductor 40 is connected to the second terminal of the-capacitor 26. The inductor 40 isolates the output of. the Qower supply on Un,, circuit 42.
The provision impedance provided by the of the anti-rioDie circuit 42 allows a from the shunt the rlonle current to be reduced before it gets to the output on line 8, The anti-ripple circuit preferably reduces the undesirable ripple current due to switohini by significant' reducing, -,n4r.-,Y=h-:', by substantially. eliminating, the high frequency portions of the rinple current.
FIG, 4 illustrates a plot of the switching noise signal for the circuit of FIG. 3. The plot 7 is a plot of 1: ripple current vex sus time, the ripple current being the current due to switching flowing in the inductor 40. The ripple current. does not have distortions at each maxima and minima, as illustrated by reference numeral 7, due to the hich freouencv eflrtions of the switching noise signal being minima substantially distortions eliminated, illustrated Thus the in martins and have been substantially eliminated.
The anti-ripple circuit is connected to electrical. ground by the switch 48 such that the anti-ripple circuit can be disconnected when low noise is not required or noise associated with switching is not an issue, m control signal is provided to control the switch.
in an alternative the switch. 48 may riot be required, with the second terminal of the resistor being connected permanently to electrical ground,. FIG. $ illustrates an alternative implementation. to FIG. 3 in which the switch is not provided, the second terminal of the resistor 46 being connected to electrical ground.
The inductor 14 is the combining inductor, and the inductor 40 is an isolation or isolating inductor, to isolate the anti-ripple circuit from the power supply cutout so that the short circuit effect of the anti ripple circuit 42 is isolated from the power supply output. The inductor 40 is much smaller than the inductor 14. ratio of the inductor 14 to the inductor 40 is 10.1.
In an alternative, the positions of the isolating inductor 40 and the combining inductor 14 may be switched. Suh an arrangement is shown in FIG. 6. FIG, 6 corresponds to the arrangement of FIG. 3, but the isolatinn' inductor is connected to the output of the switching stage 30, and the combining inductor 14;of the combiner 30) is connected between the isolating inductor and the combiner output. The anti-rpple circuit is connected at the connection between the combing circuit and the isolating. inductor.
in the arrangement of FIG. 6, the isolating inductor isolates the switching stage from the anti -ripple circuit In general: therefore r it may be considered. that the anti-ripple circuit can be connected to either terminal.
of the combining inductor of the combiner, and then the isolai-ing inductor is connected between to isolate either the combiner from the anti-ripoe circuit or to isolate the switching stage from the ripple circuit, depending on where the anti-ripple circuit is connected, Aithouqh the arrangement of. FIG, 6 is shown as a moriitication to the arrangement of FIG. 3, the 5 modification of FIG S 'av also be applied in FIG, 6, The anti -ripple circuit 42 be any shunt network that provides rejection at high frequency. The anti -ripple circuit 42 may contain elements other than the resistor 46 and capacitor 44. In general the anti-ripple circuit is a shunt network or shunt impedance to shunt only high frequency components, and not low frequency ripple noise, or the actual signal, In embodiments the combiner 30 may comprise only the inductor 14, The invention has been described by way of reference to examples. The invention is not limited to the detail of any example and any aspect described may he implemented alone or in combination. The scope of the invention is defined by the appended claims, 1.c
GB1502246.0A 2015-02-11 2015-02-11 Switcher noise reduction Withdrawn GB2535178A (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
GB1502246.0A GB2535178A (en) 2015-02-11 2015-02-11 Switcher noise reduction
PCT/US2016/017520 WO2016130785A1 (en) 2015-02-11 2016-02-11 Switcher noise reduction

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB1502246.0A GB2535178A (en) 2015-02-11 2015-02-11 Switcher noise reduction

Publications (2)

Publication Number Publication Date
GB201502246D0 GB201502246D0 (en) 2015-03-25
GB2535178A true GB2535178A (en) 2016-08-17

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Family Applications (1)

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Country Status (2)

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GB (1) GB2535178A (en)
WO (1) WO2016130785A1 (en)

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20140028368A1 (en) * 2012-07-26 2014-01-30 Rf Micro Devices, Inc. Programmable rf notch filter for envelope tracking
GB2510397A (en) * 2013-02-01 2014-08-06 Nujira Ltd Envelope tracking power supply with feedback
US20140218109A1 (en) * 2013-02-01 2014-08-07 Nujira Limited 2g support for 2g and 3g/4g envelope tracking modulator

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP5003134B2 (en) * 2006-01-10 2012-08-15 日本電気株式会社 Amplifier
US9298198B2 (en) * 2011-12-28 2016-03-29 Rf Micro Devices, Inc. Noise reduction for envelope tracking
WO2013119587A1 (en) * 2012-02-09 2013-08-15 Skyworks Solutions, Inc. Apparatus and methods for envelope tracking
JP6149452B2 (en) * 2013-03-22 2017-06-21 富士通株式会社 Power supply device and semiconductor integrated circuit device

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20140028368A1 (en) * 2012-07-26 2014-01-30 Rf Micro Devices, Inc. Programmable rf notch filter for envelope tracking
GB2510397A (en) * 2013-02-01 2014-08-06 Nujira Ltd Envelope tracking power supply with feedback
US20140218109A1 (en) * 2013-02-01 2014-08-07 Nujira Limited 2g support for 2g and 3g/4g envelope tracking modulator

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Publication number Publication date
WO2016130785A1 (en) 2016-08-18
GB201502246D0 (en) 2015-03-25

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COOA Change in applicant's name or ownership of the application

Owner name: SNAPTRACK, INC.

Free format text: FORMER OWNER: NUJIRA LIMITED

WAP Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1)