(12) United States Patent
`Petter
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 7,692,938 B2
`Apr. 6, 2010
`
`US007692938B2
`
`(54) MULTIPHASE POWER CONVERTERS AND
`MULTIPHASE POWER CONVERTNG
`METHODS
`
`(75) Inventor: Jeffrey K. Petter, Williston, VT (US)
`
`(73) Assignee: Northern Power Systems, Inc., Barre,
`VT (US)
`
`(*) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 148 days.
`
`(21) Appl. No.: 11/850,103
`
`(22) Filed:
`
`Sep. 5, 2007
`
`(65)
`
`Prior Publication Data
`US 2008/OO74911A1
`Mar. 27, 2008
`Related U.S. Application Data
`(60) Provisional application No. 60/842,762, filed on Sep.
`6, 2006.
`(51) Int. Cl
`we
`(2006.01)
`HO2H 7/22
`363A56 363/131
`(52) U.S. Cl
`ir grgrrr.
`s
`(58) Field of Classification Search ................. 323/272,
`323/283, 361, 56, 132,131
`See application file for complete search history.
`References Cited
`
`(56)
`
`U.S. PATENT DOCUMENTS
`
`5,016, 158 A
`
`5, 1991 Matsui et al.
`
`5/1991 Bourgeault et al. ...... 363,21.12
`5,019,954. A *
`9/1993 Galloway et al.
`5,245,525 A
`5,253,155 A 10, 1993 Yamamoto
`5,657,217 A
`8, 1997 Watanabe et al.
`5,852,554. A 12/1998 Yamamoto
`6,023,154. A
`2/2000 Martinez .................... 323,272
`6,034,514 A * 3/2000 Sakai
`... 323,225
`6,084,790 A * 7/2000 Wong .......................... 363.71
`6,696,823 B2 * 2/2004 Ledenev et al. ............. 323,272
`6,850,045 B2 * 2/2005 Muratov et al. ............. 323/272
`7,449,867 B2 * 1 1/2008 Wu et al. .................... 323,247
`7.495.421 B2 *
`2/2009 Weng et al. ................. 323,272
`2005/0225.307 A1 10, 2005 Sato et al.
`2006, OO23476 A1
`2/2006 FOsler
`tal.
`2006, 0071649 A1
`4, 2006 Sch
`CO a
`
`* cited by examiner
`Primary Examiner Shawn Riley
`(74) Attorney, Agent, or Firm Downs Rachlin Martin PLLC
`(57)
`ABSTRACT
`
`A new class of multiphase converters having at least two
`switching cells driven by out-of-phase PWM reference sig
`9.
`:n by
`1-p
`1g
`nals and corresponding respective PWM control signal sig
`nals. In some embodiments, once of the Switching cells are
`driven as a function current-balancing feedback so as to bal
`ance the currents between the switching cells. Various
`embodiments of the multiphase converter include one or
`more unique transformers for averaging the output of the
`C
`glng
`p
`Switching cells.
`
`27 Claims, 10 Drawing Sheets
`
`920
`
`8 PASE
`Raga
`AW
`senterator
`
`94A
`
`
`
`
`
`--
`
`
`
`
`
`
`
`
`
`
`
`
`
`Petitioners
`Ex. 1050, p. 1
`
`

`

`U.S. Patent
`
`Apr. 6, 2010
`
`Sheet 1 of 10
`
`US 7.692,938 B2
`
`PRIORART
`104A
`
`120
`
`
`
`
`
`124
`
`112
`
`108A
`
`INPUT
`VOLTAGE
`
`100-N-1
`104B
`
`Ha
`CURRENT
`DIRECTION
`
`OUTPUT
`VOLTAGE
`
`116
`
`108B
`
`PRIORART
`
`204A
`
`
`
`
`
`INPUT
`VOLTAGE
`
`200 1
`2043
`
`CURRENT
`DIRECTION
`
`PRIOR ART
`
`
`
`312
`
`HIGH
`VOLTAGE
`PORT
`
`
`
`300 Nu-1
`
`208A
`
`OUTPUT
`VOLTAGE
`
`224
`
`208B
`
`CURRENT
`DIRECTION
`
`LOW
`VOLTAGE
`PORT
`
`Petitioners
`Ex. 1050, p. 2
`
`

`

`U.S. Patent
`
`Apr. 6, 2010
`
`Sheet 2 of 10
`
`US 7,692,938 B2
`
`FG4A
`PRIORART
`
`404
`
`408
`
`
`
`INPUT
`VOLTAGE
`
`400 - Nu-1
`
`
`
`cuRRENT
`DIRECTION
`
`OUTPUT
`VOLTAGE
`
`PRIORART
`
`
`
`1
`
`1
`
`INPUT
`VOLTAGE
`
`
`
`
`
`- -
`
`
`
`CURRENT
`DIRECTION
`
`OUTPUT
`VOLTAGE
`
`440 - Nu-1
`
`-
`
`5
`
`Petitioners
`Ex. 1050, p. 3
`
`

`

`U.S. Patent
`
`Apr. 6, 2010
`
`Sheet 3 of 10
`
`US 7,692,938 B2
`
`FIG.5A
`
`568
`
`500
`
`TRINE - 7 S.
`
`GENERATOR
`
`574A
`
`SIGNALS
`
`CH
`
`S1
`
`S2
`
`O
`B>
`512B
`512A N 522A A?
`522B
`
`574B
`508
`-1
`
`504
`S1
`y (582A) 1. V2 (582B) 1.
`536B
`532 2P
`548B
`C
`N
`556
`OUTPUT
`VOLTAGE
`
`MN
`(i.
`
`MY
`-1
`
`Va
`
`524A
`
`C
`
`O
`CURRENT
`DIRECTION
`536A2
`
`520B /
`
`516
`
`584
`
`INPUT
`VOLTAGE
`
`540
`
`C
`
`
`
`COMPARTOR 1
`INPUTS
`COMPAR TOR2
`INPUTS
`
`
`
`V
`0.
`
`VOLTAGE
`ATV1
`
`VOLTAGE
`ATV2
`
`VOLTAGE
`ATV a
`
`Petitioners
`Ex. 1050, p. 4
`
`

`

`U.S. Patent
`
`Apr. 6, 2010
`
`Sheet 4 of 10
`
`US 7,692,938 B2
`
`FIG.6A
`
`628A
`
`628B
`
`w1
`
`
`
`oN DELAY DELAY
`
`on DELAY
`
`640B-Sy
`
`A
`
`A
`
`620
`
`616B
`
`e
`
`s
`
`El
`
`608C
`RGas
`DiGidw
`
`WAGE
`
`680E
`
`600
`3 PHASE
`61.2
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`TNF 662A
`Jut1. 652A
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`672
`Y- 662B le?s - Efi?is54A 652B
`64.3E
`Jul.1:
`B> -?s glo- D-REAnn 654B
`662C
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`it is D-5Eyrus 654C
`S5
`? 64c -
`39
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`E-
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`s: y s: 1:4
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`620A
`642B
`i. CURRENT
`608 N-r
`620A1
`"Le 25, s
`620A2 N 682
`62OB2
`620 C1
`632A-1llf%2c2.
`608A
`636A-162B 62s
`
`s
`
`FIG.6B
`
`
`
`COMPARITOR 1
`INPUTS
`
`INPUTS
`COMPARITOR 3
`INPUTS
`VOLTAGE
`ATV1 674D-6
`VOLTAGE
`V
`ATV2 674D-6
`VOLTAGE
`V
`ATV3 674D
`voLTAGE
`Vi
`A Va.
`O
`
`
`
`:
`
`;
`N:
`--
`673A
`
`trirt
`-
`
`-
`
`678
`
`Petitioners
`Ex. 1050, p. 5
`
`

`

`U.S. Patent
`
`Apr. 6, 2010
`
`Sheet 5 of 10
`
`US 7,692,938 B2
`
`F.G.7A
`
`3 PHASE
`TRANGE
`WAVE
`GENERATOR
`
`736A
`
`ON DELAY
`
`736B
`BS-D
`4 SEA
`736C
`
`ON DELAY
`
`i> DocN5EAy-s:
`
`S1
`
`S3
`
`S4
`
`S5
`
`760B
`\,:
`
`Y
`
`760C
`
`A
`
`/N-748C
`v -708
`724B N700
`
`CURRENT
`RECTION
`
`C
`
`V
`
`752C
`
`724A
`
`752B
`
`720
`
`FIG.7B
`COMPARITOR 1
`INPUTS
`
`-
`
`
`
`COMPARITOR2
`INPUTS
`COMPARITOR 3
`INPUTS
`VOLTAGE
`ATV1
`
`VOLTAGE
`ATV2
`
`VOLTAGE
`ATV3
`
`VOLTAGE
`ATV a
`
`----------------
`
`Petitioners
`Ex. 1050, p. 6
`
`

`

`U.S. Patent
`
`Apr. 6, 2010
`
`Sheet 6 of 10
`
`US 7,692.938 B2
`
`FIG.8
`
`828A
`S
`
`WAVE
`
`812A
`
`812B
`
`ON DELAY
`
`800
`824
`,
`fit a2OA
`f
`oN DELAY
`820B
`820C Nis Dooney
`“Bs
`N
`812C
`"G> D-55A
`812D
`Bs Dooristy
`on DELAY
`s -Do-ONDEY
`812F oN DELAY
`
`V a2OD
`Y- 820E
`
`1
`
`4/
`
`812E
`
`Y 804A
`
`S1
`S.
`
`S4
`
`S7
`S8
`
`S9
`
`S10 8043
`
`S1
`Sf2
`
`area-e-,
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`S1)
`
`
`
`
`
`
`
`INPUT
`WOLAG
`
`C
`
`/. w ( A
`
`(
`
`840A
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`828F
`316B
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`20F so4A
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`
`A.
`
`erec'" -e, -sier
`(
`
`
`
`
`
`
`
`836B
`OUTPUT
`VOLAGE
`
`Petitioners
`Ex. 1050, p. 7
`
`

`

`U.S. Patent
`
`Apr. 6, 2010
`
`Sheet 7 of 10
`
`US 7,692.938 B2
`
`FIG.9
`
`920
`
`9 PHASE
`TRANGLE
`WAVE
`
`GENERATOR
`
`900
`
`924A
`
`Sf
`
`is Dociety - so
`is DiPi 904A
`HHSE-i
`is D-
`S6
`|||s D.E.Y.,
`924D
`IgEEE:
`HH ->conteay
`Sfo
`His Doonisty - si
`924G. on DELAY
`S13
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`D.E. x 904C
`225A
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`Do-oN DELAY
`S8
`
`904B
`
`DELAY
`
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`
`904C
`
`908A
`
`--
`
`B-g-b
`
`--O
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`INPUT
`
`WOLAGE ?
`
`d
`
`
`
`3 PHASE
`OUTPUT
`VOLTAGE
`
`Petitioners
`Ex. 1050, p. 8
`
`

`

`U.S. Patent
`
`Apr. 6, 2010
`
`Sheet 8 of 10
`
`US 7,692,938 B2
`
`1024D
`
`O
`
`is D-35E, 1000
`5
`TNF 1024A
`--
`GENERATOR
`
`FIG 10A
`
`MV
`
`1036
`)- O
`
`
`
`
`
`
`
`
`
`
`
`B>-is s
`
`O
`
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`
`
`
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`
`1040A
`WOLTAGE
`
`S7
`
`ON DELAY
`Sf
`-Dooniety -s2
`1024B
`S3
`|-
`S4
`s Do
`1024C
`S5
`ON DELAY
`B Do
`S6
`1020
`1008C
`Y-1
`1008D
`1004
`1040c An
`10 12A
`
`OUTPU
`WOLAGE
`
`101.23
`
`FIG 10B 1032A 1032B
`1032C
`
`1028A
`102.8B
`
`1028C
`
`
`
`INPUTS
`COMPAROR2
`INPUS
`COMPARITOR 3.
`INPUTS
`COMPARTOR4
`INPUS
`WOLAGE
`A V1
`
`
`
`WOLAGE
`ATV2
`WOLAGE
`A V3
`VOLTAGE
`AW4.
`
`WOAGE
`A War
`
`Petitioners
`Ex. 1050, p. 9
`
`

`

`U.S. Patent
`
`Apr. 6, 2010
`
`Sheet 9 of 10
`
`US 7,692,938 B2
`
`FIG 11A
`
`1112
`V1
`V2
`INPUT v3
`V4
`V5
`
`-100
`
`Wa
`OUTPUT
`
`1112
`
`NU
`1118A
`INPUT
`FIG. 11B ince U
`V4
`
`
`
`
`
`1104
`
`1.
`OUTPUT
`
`FIG.11C
`
`V2
`INPUT
`V3
`
`V4
`
`Wa
`
`OUTPUT
`
`1124
`
`FIG. 12A
`1228A1
`1228B2
`
`1216A
`V1
`1228B1
`V2
`INPUT
`
`1200
`
`122
`1208B
`
`V3
`1216C
`1228C2
`
`1208C
`Wa OUTPUT
`
`?
`
`FIG.12B 1248A
`
`
`
`
`
`24
`INPUT V3
`1240C
`
`40D
`
`
`
`1212A
`
`1248B
`1212B
`1243C
`1212C
`1248D
`1212D
`1248E
`1212E
`
`Petitioners
`Ex. 1050, p. 10
`
`

`

`U.S. Patent
`
`Apr. 6, 2010
`
`Sheet 10 of 10
`
`US 7,692,938 B2
`
`FIG.
`13
`COMPARITOR 1
`INPUTS
`COMPAR TOR2
`INPUTS
`COMPARITOR 3 -
`INPUTS
`
`VOLTAGE
`ATV2
`
`VOLTAGE
`ATV3
`
`VOLTAGE
`ATV a
`
`FIG. 14
`
`1412C
`
`1412D
`
`? 1412E
`
`1404A
`
`1404C
`
`1404E 1404G
`
`1404
`
`
`
`
`
`1408
`
`OUTPUT
`VOLAGE
`
`Petitioners
`Ex. 1050, p. 11
`
`

`

`1.
`MULTIPHASE POWER CONVERTERS AND
`MULTIPHASE POWER CONVERTNG
`METHODS
`
`RELATED APPLICATION DATA
`
`5
`
`This application claims the benefit of priority of U.S. Pro
`visional Patent Application Ser. No. 60/842,762, filed Sep. 6,
`2006, and titled “Multiphase Power Converter,” which is
`incorporated by reference herein in its entirety.
`
`10
`
`FIELD OF THE INVENTION
`
`The present invention generally relates to the field of power
`electronics. In particular, the present invention is directed to 15
`multiphase power converters and multiphase power convert
`ing methods.
`
`BACKGROUND
`
`2O
`
`Two of the most basic building blocks in power electronics
`are the buck and the boost converter circuits 100, 200 illus
`trated in FIGS. 1 and 2, respectively. Each of these converter
`circuits 100, 200 generally include input nodes 104A-B,
`204A-B, output nodes 108A-B, 208A-B, an inductor 112, 2s
`212, a diode 116, 216, a smoothing capacitor 120, 220 across
`the high Voltage nodes and a Switch 124, 224. The operation
`of buck and boost converter circuits 100, 200 is well-under
`stood by virtually all power electronics engineers. Typically
`the Switches 124, 224 in these circuits 100, 200 are turned on 30
`and off at a constant frequency and with an adjustable duty
`factor. The duty factor is used to control the input-to-output
`voltage ratio. Buck and boost circuits 100, 200 can be com
`bined to make the half-bridge circuit 300 shown in FIG.3 that
`includes two pairs each consisting of a diode 304,308 and a 35
`switch 312,316. Half-bridge circuit 300 is a buck converter
`when current and power are flowing left to right (relative to
`FIG. 3) and a boost converter in the opposite direction.
`Devices used for switches 124, 224, 312, 316 in these
`switching power converter circuits 100, 200, 300 have 40
`included MOSFETs, IGBTs, Bipolar Transistors, GTOs,
`MCTs, and other power switches that can be turned on and off
`quickly and relatively easily with minimal power loss and
`high reliability. All of these devices have some power losses.
`Because of this power loss, all of these devices cause a limit 45
`to the amount of power that can be converted in a specific
`application.
`For higher power applications, it is common for designers
`to use parallel Switching devices to spread the losses in the
`switches. FIG. 4A illustrates a buck converter circuit 400 50
`having parallel switches 404, 408. Of course, a greater num
`ber of switches can be implemented. Two are shown for
`simplicity. Paralleling the switches in this manner allows
`better cooling because the heat is spread out. Higher effi
`ciency is also possible. When parallel switches are used in this 55
`fashion, all the parallel switches are turned on and off at the
`same time, thereby acting as one larger Switch. There are a
`number of problems with parallel switching due to uneven
`sharing of the load current during conduction and during
`Switching.
`For higher performance, including better regulation,
`Smaller size, lower weight, faster response, and, up to a point,
`lower cost, a higher Switching frequency is used. A higher
`Switching frequency reduces the size of the magnetic compo
`nents of the converters. Also, the high frequency makes it 65
`possible to regulate the output more quickly. A problem with
`high Switching frequencies is that components get less effi
`
`60
`
`US 7,692,938 B2
`
`2
`cient, thereby limiting the practicality of raising the Switching
`frequency. A conventional approach to getting around this
`limitation is to use a resonate converter of Some type. Reso
`nate converters, in general, however, add to the complexity of
`the circuits. They tend to have more limited operating ranges
`and other performance limits, but in Some cases are very Small
`and efficient.
`Implementing multiphase converters is another approach
`to avoiding the limitations of losses due to increased Switch
`ing frequencies in simple pulse-width modulation (PWM),
`hard-switched converters. FIG. 4B shows a simple prior art
`multiphase converter circuit 440. The advantages of mul
`tiphase converter circuits, such as circuit 440, have been
`established in some applications, like the Voltage-regulation
`module (VRM) concepts of Dr. Fred C. Lee at the University
`of North Carolina. Circuit 440 of FIG. 4B is basically the
`circuit used by Dr. Lee in his VRM concepts. Advantages of
`circuit 440 include high bandwidth with lower effective
`switching frequency, lower ripple current in the DC bus
`capacitance, higher current capability and Smaller size. Cir
`cuit 440 is simply one of a whole class of multiphase con
`Verters. In general, all multiphase converters are made of
`either a number of basic buck/boost or half-bridge switching
`cells, for example, basic buck/boost cells 444A-B of FIG. 4B,
`arranged in parallel with one another. The Switching cells are
`Switched at differing Switching times relative to one another
`but with the same duty cycle and frequency at any instant in
`time. However, the Switching among the cells are phase
`shifted from each other in various ways.
`There are a number of shortcomings associated with con
`ventional multiphase converters. These shortcomings
`include: their magnetic components are needed to prevent
`circulating AC currents; their magnetic circuits are typically
`expensive and complex to design; current balance between
`the Switching cells at low frequency is a problem; control
`methods are not well established; and switch timing can be
`complex. The present invention includes features that address
`all these issues.
`
`SUMMARY OF THE DISCLOSURE
`
`In one embodiment, the present invention is directed to a
`multiphase power converter. The multiphase power converter
`includes a number N of switching cells having corresponding
`respective N Switched outputs and an averaging transformer.
`The averaging transformer includes a common output node
`and an output in electrical communication with the common
`output node. The averaging transformer further includes N
`double-winding segments each including a pair of reactor
`windings in series with one another. Each of the N double
`winding segments has a first end electrically connected to a
`corresponding respective one of the N Switched outputs. A
`second end of each of the N double-winding segments is
`electrically connected to the common output node. Ninter
`phase reactors are each formed by pairs of the reactor wind
`ings in differing ones of the N double-winding segments.
`In another embodiment, the present invention is also
`directed to a multiphase power converter. This multiphase
`power converter includes a number N of switching cells hav
`ing corresponding respective NSwitched outputs. Each of the
`N Switched outputs is controlled by a corresponding respec
`tive at least one Switching control signal. A control system is
`provided for controlling the N switching cells. The control
`system includes means for providing N pulse-width modula
`tion (PWM) reference signals respectively to the NSwitching
`cells. Each of the N PWM reference signals is based on a
`common waveform but has a differing phase relative to each
`
`Petitioners
`Ex. 1050, p. 12
`
`

`

`US 7,692,938 B2
`
`3
`other of the N PWM reference signals. The control system
`further includes means for providing N PWM control signals
`and means for generating each of the at least one Switching
`control signal as a function of ones of the N PWM reference
`signals and corresponding respective ones of the N PWM
`control signals.
`In a further embodiment, the present invention is directed
`to a method of converting electrical power. The method
`includes providing a multiphase power converter that
`includes a number N of switching cells having corresponding
`respective N switched outputs. N pulse-width modulation
`(PWM) reference signals having a common waveform but
`differing phases are provided. N PWM control signals are
`provided. At least N Switching control signals are generated
`as a function of the NPWM reference signals and the NPWM
`15
`control signals. The N switching cells are driven with corre
`sponding respective ones of the at least N Switching control
`signals so as to cause the NSwitching cells to provide the N
`Switched outputs.
`
`10
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`4
`timing diagram for the multiphase power converter of FIG.
`10A for a PWM reference signal having a triangular wave
`form and a PWM control signal having sinusoidal waveform:
`FIGS. 11A-C are each a schematic diagram illustrating a
`conventional magnetic current Summing circuit that may be
`used in a multiphase power converter of the present invention;
`FIGS. 12A-B are each a schematic diagram illustrating a
`magnetic current Summing circuit of the present invention
`that may be used in a multiphase power converter, Such as a
`multiphase power converter of the present invention;
`FIG. 13 is a timing and waveform diagram for a PWM
`timing scheme that utilizes a very Small delay between each
`Switching cell output; and
`FIG. 14 is a schematic diagram of a multiphase power
`inverter having five Switching cells for illustrating active cur
`rent balancing.
`
`DETAILED DESCRIPTION
`
`FIG.5A illustrates a multiphase power converter 500 made
`in accordance with the present invention. Generally, mul
`tiphase power converter 500 comprises converter circuitry
`504 and control circuitry 508 that controls the converter cir
`cuitry so as to achieve the desired result for a particular
`application. Converter circuitry 504 includes a plurality of
`“switching cells' 512A-B, i.e., components similar to the
`Switching portions of conventional converter circuits, such as
`basic buck/boost and half-bridge converter circuits 100, 200,
`300 of FIGS. 1-3. On the low voltage side 516 of converter
`circuit 504, Switching cells 512A-B drive a unique averaging
`transformer 520 coupled between the switching cells and
`output node 524A of output nodes 524A-B.
`Power converter 500, like power converters 600, 700, 800,
`900, 1000 of respectively, the following FIGS. 6A, 7A, 8,9.
`and 10A, form part of a new and unique class of multiphase
`power converters. When multiphase power converters 500,
`600, 700, 800,900, 1000 and other power converters made in
`accordance with the present invention are operated with the
`special timing described, these converters can outperform
`traditional converters. At a high level, the present invention
`includes paralleling Switching cells (such as Switching cells
`512A-B of FIG. 5A), using particular magnetic circuit con
`figurations (e.g., averaging transformer 520), on the low
`Voltage side (such as low-voltage side 516), and specific
`timing of the switches (e.g., switches 522A-B). The resulting
`performance improvements over traditional pulse-width
`modulation (PWM) converters include much less current in
`the Smoothing capacitors on the high Voltage side of Switch
`ing cells, higher control bandwidths, higher efficiency,
`Smaller size, and lower cost, among others. Embodiments of
`the present invention include defining an entire class of cir
`cuits that can provide these improvements, providing
`improved magnetic circuit configurations (interphase reac
`tors), PWM methods for reducing ripple currents and volt
`ages on various components, methods for balancing current
`in the new class of power converters and other power con
`Verters containing parallel Switching cells, and methods of
`controlling the new class of power converters. These and
`other embodiments of the present invention are described
`below in detail.
`Referring again to FIG. 5A, and also to FIG. 5B, in the
`present example, switching cells 512A-B are of the basic
`buck/boost type, but in other embodiments these switching
`cells could be of another type, such as the half-bridge type
`illustrated in FIGS. 6A, 7A, 8, 9, and 10A. In addition to
`switches 522A-B, each switching cell 512A-B may include a
`respective diode 528A-B for controlling the direction of cur
`
`For the purpose of illustrating the invention, the drawings
`show aspects of one or more embodiments of the invention.
`However, it should be understood that the present invention is
`not limited to the precise arrangements and instrumentalities
`shown in the drawings, wherein:
`FIG. 1 is a schematic diagram of a conventional buck
`converter circuit;
`FIG. 2 is a schematic diagram of a conventional boost
`converter circuit;
`FIG.3 is a schematic diagram of a conventional half-bridge
`converter circuit;
`FIG. 4A is a schematic diagram of a conventional buck
`converter circuit having a plurality of parallel switches: FIG.
`4B is a schematic diagram of a conventional multiphase buck
`converter circuit;
`FIG. 5A is a schematic diagram of a multiphase power
`converter of the present invention comprising two Switching
`cells providing a single phase output signal; FIG. 5B is a
`timing diagram for the multiphase power converter of FIG.
`5A for a PWM reference voltage signal having a triangular
`waveform and a PWM control signal having a linearly
`increasing Voltage;
`FIG. 6A is a schematic diagram of a multiphase power
`converter of the present invention comprising three Switching
`cells providing a single phase output signal; FIG. 6B is a
`timing diagram for the multiphase power converter of FIG.
`6A for a PWM reference voltage signal having a triangular
`waveform and a PWM control signal having a linearly
`increasing Voltage;
`FIG. 7A is a schematic diagram of an alternative mul
`tiphase power converter of the present invention comprising
`three Switching cells providing a single-phase output signal;
`FIG. 7B is a timing diagram for the multiphase power con
`verter of FIG. 7A for a PWM reference voltage signal having
`a triangular waveform and a PWM control signal having a
`linearly increasing Voltage;
`FIG. 8 is a schematic diagram of a multiphase power con
`Verter of the present invention comprising six Switching cells
`providing a single phase output signal;
`FIG. 9 is a schematic diagram of a multiphase power con
`Verter of the present invention comprising nine Switching
`cells providing a three-phase output signal;
`FIG. 10A is a schematic diagram of a multiphase power
`converter of the present invention comprising four Switching
`cells providing a single phase output signal; FIG. 10B is a
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`Petitioners
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`5
`rent flow in that cell between voltage node 532 and the output
`536A-B of that cell. The high-voltage side 540 of converter
`circuit 504 may include a smoothing capacitor 544 that per
`forms largely the same function as similarly situated Smooth
`ing capacitors of conventional power converters. Averaging
`transformer 520 includes first and second interphase reactors
`548A-B that each include a reactor winding 536A1, 536A2
`electrically coupled to output 536A of switching cell 512A
`and a reactor winding 536B1, 536B2 electrically coupled to
`output 536B of switching cell 512B. Averaging transformer
`520 may be coupled to output node 524A through a suitably
`sized output inductor 556.
`Control circuitry 508 provides switch control signals
`560A-B that drive, respectively, switches 522A-B of corre
`sponding Switching cells 512A-B. In general, control cir
`15
`cuitry 508 drives switches 522A-B as a function of a PWM
`reference signal 564, for example, a fixed frequency repeating
`waveform such as triangular waveform 564A of FIG. 5B, and
`a PWM control signal 568 that determines the overall char
`acter of the waveform of the output signal 572 (voltage) (FIG.
`5B) output on output nodes 524A-B. In the present case, the
`waveform 568A of PWM control signal 568 for the time
`period illustrated is a linearly increasing waveform. PWM
`reference signal 564 and PWM control signal 568 may be
`used to generate switch control signals 560A-B in any suit
`able manner, such as the analog comparators 574A-B shown.
`Control circuit 508 may include a reference signal genera
`tor 576 that generates PWM reference signal 564 having
`triangular waveform 564A. Since converter circuit 504 has
`two switching cells 512A-B and it is necessary to drive these
`cells out of phase with one another, control circuitry 508 may
`include a suitable means for providing a second triangular
`waveform 564B (FIG. 5B) that is essentially the same as
`triangular waveform 564A, but is out of phase with triangular
`waveform 564A. In the present example, the phase difference
`is provided by an inverter 578 that provides comparator 574B
`with a waveform 564B that is a full 180° out of phase with
`waveform 564A. Those skilled in the art will readily appre
`ciate that there are other ways to provide two different phases,
`Such as with a multiphase signal generator, utilizing various
`40
`delay elements, or locating inverter 578, for example, down
`stream of comparator 574B. Those skilled in the art will also
`readily understand that although control circuit 508 is shown
`as being an analog circuit, control circuit could readily be
`implemented in a digital circuit or modeled in Software.
`Comparator 574.A compares non-inverted PWM reference
`waveform 564A to PWM control waveform 568A and gen
`erates a pulse during the period that the magnitude of PWM
`reference waveform 564A falls below the magnitude of PWM
`control waveform 568A. This is illustrated with pulsed wave
`50
`form 580A (FIG.5B) that represents the voltage at node 582A
`of switching cellS12A (FIG.5A). Comparator 574B works in
`essentially the same way as comparator 574.A, except that
`instead of utilizing PWM control waveform 568A as is, com
`parator 574B utilizes a modified PWM control waveform
`55
`568B (FIG. 5B) obtained via a feedback loop 584. Modified
`PWM control waveform 568B is created from modifying
`PWM control waveform 568A using a feedback signal 586
`that is a function of a current differential signal 588 that
`represents the differential between the currents in outputs
`536A-B of respectively, switching cells 512A-B. Current
`differential signal 588 may be obtained in any of a number of
`ways, such as using a differential current sensor 590 in aver
`aging transformer 520 between interphase reactors 548A-B.
`Feedback loop 584 may include a gain amplifier 592 and an
`integrator 594 for conditioning current differential signal 588
`into feedback signal 586. Pulsed waveform 580B (FIG. 5B)
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`represents the voltage at node 582B that is controlled by
`switch control signal 560B. Pulsed waveform 572 of FIG.5B
`illustrates the voltage across output nodes 524A and 524B
`after outputs 536A-B have been combined by averaging
`transformer 520. It is clearly seen from FIG. 5B that pulsed
`waveform 572 provides a good representation of PWM con
`trol waveform 568A.
`Still referring to FIGS. 5A-B, it is noted that frequency of
`the output pulsed waveform 596 is twice the frequency of
`each switch control signal 560A-B (as represented by voltage
`waveforms 580A-B) and that the output voltage steps 572A
`are half the size of the corresponding steps 580C of voltage
`waveforms 580A-B. Each of these characteristics reduces the
`size of output inductor 556 required by one-half so that the
`output inductance required is one-quarter of what it would
`have been if switches 522A-B were switched at the same
`time. Also, due to the phase difference between PWM refer
`ence waveforms 564A-B, the pulse-width decisions are made
`four times, rather than two, for each Switching cycle, thereby
`improving response time by a factor of two. In addition, the
`response time of converter circuit 504 (FIG. 5A) is also
`improved by the lower inductance of output inductor 556. The
`currents in outputs 536A-B are balanced via feedback loop
`584 so that the devices used for Switches 522A-B do not
`require any special matching. Another benefit of multiphase
`power converter 500 is that the current ripple in the smoothing
`capacitor 544 is reduced, making it possible to reduce the size
`of the capacitor used or improve its efficiency and life. The
`reduction of capacitor current occurs due to the phase shifting
`of the DC current in the two switching cells 512A-B, causing
`the largest ripple current frequencies to have opposing phases
`so as to cancel each other.
`As can be readily seen in FIG. 5A, averaging transformer
`520 may be considered to include 1) an “outer loop' 520A
`electrically connected at one end to output node 582A of
`switching cell 512A and at the other end to output inductor
`556 and 2) an "inner loop'520B electrically connected at one
`end to output node 582B of switching cell 512B and at the
`other end to output inductor 556. This configuration allows
`inductor windings 536A1, 536B1 associated with respective
`switching cells 512A-B to form one reactor 548A and induc
`tor windings 536A2, 536B1 associated with respective
`switching cells 512A-B to form second reactor 548B. Differ
`ential current sensor 590 is also readily seen as being located
`between reactor windings 536A1,536A2 of outer loop 520A
`and between reactor windings 536B1, 536 B2 of inner loop
`520B. Other details of averaging transformer 520 may be
`discerned from the description of similar averaging trans
`formers 1200, 1204 of FIGS. 12A and 12B, respectively.
`Compared to conventional power converters, the cost of
`these improvements generally include the addition of a dif
`ferential current sensor (here, sensor 590), the addition of an
`averaging transformer (here, transformer 520), additional
`switch-driving circuitry (here, e.g., comparator 574B,
`inverter 578, and feedback loop 584), and more complex
`control. However, averaging transformer 520 is typically
`Smaller than the output inductor in a conventional design, so
`that the total size of all of the magnetic components in mul
`tiphase converter 500 is generally less than the total size of the
`magnetic components of a conventional simple buck con
`Verter. In most applications, a multiphase converter of the
`present invention, such as multiphase converter 500, will be
`lower in cost, more efficient, higher in speed, Smaller in size,
`and weigh less than a traditional hard-switched PWM con
`Verter.
`Multiphase power converter 500 of FIG. 5A is a simple
`form of the invention. However, the basic concepts behind
`
`Petitioners
`Ex. 1050, p. 14
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`multiphase power converter 500 can be used to make virtually
`any type of power converter. For example, FIG. 6A shows a
`bi-directional DC-to-DC multiphase converter 600 that
`employs three parallel switching cells 604A-C, which in this
`example are half-bridge cells similar to the half-bridge power 5
`converter 300 of FIG. 3. Other than switching cells 604A-C
`being of a different type relative to switching cells 512A-B of
`FIG.5A, multiphase converter 600 of FIG. 6A is an extension
`of multiphase converter 500 of FIG. 5A. That is, instead of
`multiphase converter 600 having just two switching cells
`604A-B, it has a third switching cell 604C and modifications
`and additional circuitry for accommodating the additional
`cell. The modifications of multiphase power converter 600
`relative to multiphase converter 500 include a different aver
`aging transformer 608 and a different reference waveform 15
`generator 612.
`Averaging transformer 608 includes three interphase reac
`tors 616A-C instead of the two interphase reactors 548A-B of
`FIG. 5A so as to account for all three phases. It is noted that
`the basic principles of averaging transformer 608 of FIG. 6A 20
`and averaging transformer 520 of FIG.5A are the same. That
`is, each output 620A-C of respective switching cells 604A-C
`is connected to a respective loop 608A-C, with loop 608A
`being considered an “outside loop' and each of loops 608B,
`608C being considered an “inside loop. Each loop 608A-C 25
`includes a corresponding respective pair of reactor windings
`620A1-2, 620B1-2, 620C1-2. In the present example, inter
`phase reactor 616A includes reactor windings 620A1 and
`620B2 of outputs 620A and 620B, respectively, interphase
`reactor 616B includes reactor winding 620B1 and 620C2 of 30
`outputs 620B and 620C, respectively, and interphase reactor
`616C includes reactor windings 620C1 and 620A2 of outputs
`620C and 620A, respectively. Other details of averaging
`transformer 608 may be discerned from the description of
`similar averaging transformers 1200, 1204 of FIGS. 12A and 35
`12B, respectively.
`Reference waveform generator 612, like reference wave
`form generator 576 of FIG. 5A, is a triangular waveform
`generator, however, it is a three-phase generator that gener
`ates the three out-of-phase reference waveforms 624A-C 40
`(FIG. 6B) corresponding respectively to the three switching
`cells 604A-C. Reference waveform generator 612 may be of
`any suitable design and may be analog, digital, or simulated in
`software. As those skilled in the art will appreciate, in alter
`native embodiments, three-phase reference waveform gen
`45
`erator 612 may be replaced with a single phase waveform
`generator and the differ