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`UNITED STATES PATENT AND TRADEMARK OFFICE
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`BEFORE THE PATENT TRIAL AND APPEAL BOARD
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`SEMICONDUCTOR COMPONENTS INDUSTRIES, LLC d/b/a
`ON SEMICONDUCTOR
`Petitioner
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`v.
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`POWER INTEGRATIONS, INC.
`Patent Owner
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`Case IPR2016-01600
`Patent No. 7,834,605
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`DECLARATION OF DR. ARTHUR W. KELLEY
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`PI 2010
`1
` ON Semiconductor v Power Integrations
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`IPR2016-01600
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`TABLE OF CONTENTS
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` 
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` 
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` 
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` 
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`Page
`INTRODUCTION AND SCOPE OF WORK ................................................ 5 
`SUMMARY OF OPINIONS ........................................................................... 6 
`  BACKGROUND AND QUALIFICATIONS ................................................. 8 
`  BASIS FOR OPINIONS ............................................................................... 10 
`FIELD OF ART ............................................................................................. 11 
`  PERSON OF ORDINARY SKILL IN THE ART ........................................ 11 
`  THE ‘605 Patent ............................................................................................ 12 
`A. 
`Technology Background: “Switch-mode” power supplies and the
`cycle-by-cycle current limit ................................................................ 12 
`The Invention of the ’605 Patent ......................................................... 21 
`B. 
`  Claim construction ......................................................................................... 29 
`  The proposed SUBSTITUTE claims 13-16 .................................................. 30 
`THE SUBSTITUTE CLAIMS NARROW THE SCOPE OF THE .............. 31 
`  THE ORIGINAL DISCLOSURE SUPPORTS THE SUBSTITUTE........... 33 
`B. 
`Independent Substitute Claim 13 Is Supported by the ’642 Application
` ............................................................................................................. 34 
`  “A power supply regulator, comprising” ....................................... 34 
`  “a comparator having a first input coupled to sense a voltage
`representative of a current flowing through a switch during an on
`time of the switch, the comparator having a second input coupled
`to receive a variable current limit threshold that increases during
`the on time of the switch” .............................................................. 34 
`  “a feedback circuit coupled to receive a feedback signal
`representative of an output voltage at an output of a power
`supply” ........................................................................................... 36 
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`2
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`TABLE OF CONTENTS (cont’d)
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`C. 
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`Page
`  “a control circuit coupled to generate a control signal in response
`to an output of the comparator and in response to an output of the
`feedback circuit, the control signal to be coupled to a control
`terminal of the switch to control switching of the switch.” ........... 36 
`  “wherein, for each of a plurality of consecutive control signal
`cycles each having a first state and a second state, the variable
`current limit threshold increases during at least a portion of the
`first state of each control signal cycle and decreases during at
`least a portion of the second state of each control signal cycle.” . 37 
`Dependent Substitute Claims 14-16 Are Supported by the ’642
`Application .......................................................................................... 40 
`
`  Claim 14: “The power supply regulator of claim [[1]] 13 further
`comprising an oscillator having a first output to generate a
`sawtooth waveform, wherein the variable current limit threshold is
`generated in response to the sawtooth waveform.” ....................... 40 
`  Claim 15: “The power supply regulator of claim [[2]] 14 wherein
`the control circuit includes a latch to provide the control signal,
`wherein the latch includes a reset input coupled to the output of the
`comparator.” .................................................................................. 41 
`  Claim 16: “The power supply regulator of claim [[1]] 13 wherein
`a duty cycle of the control signal is modulated in response to an
`output of the feedback circuit.” ...................................................... 42 
`  THE PROPOSED SUBSTITUTE CLAIMS ARE PATENTABLE ............. 42 
`B. 
`The de Sartre Patent Does Not Disclose the New Limitations Added
`to the Proposed Substitute Claims 13-16 and Therefore Does Not
`Anticipate the Substitute Claims ......................................................... 43 
`The Maige Patent Does Not Disclose the New Limitations Added to
`the Proposed Substitute Claims 13-16 and Therefore Does Not
`Anticipate the Substitute Claims ......................................................... 46 
`D.  No Known Prior Art Discloses the New Limitations Added to the
`Proposed Substitute Claims 13-16 and Therefore No Known Prior Art
`Anticipates the Substitute Claims ....................................................... 49 
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`C. 
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`3
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`TABLE OF CONTENTS (cont’d)
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`E. 
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`Page
`No Combination of Known Prior Art Renders Obvious The Proposed
`Substitute Claims ................................................................................. 51 
`Claim Interpretation ............................................................................ 53 
`A. 
`  CONCLUSION .............................................................................................. 58 
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`4
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`I, Arthur W. Kelley, of Cary, North Carolina, declare that:
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`Case IPR2016-01600
`Attorney Docket No: 10256-0021IPC
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`
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`INTRODUCTION AND SCOPE OF WORK
`1.
`I have been retained by Patent Owner Power Integrations, Inc.
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`(“Power Integrations” or “Patent Owner”) in the above-captioned Inter Partes
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`Review (IPR) as an independent expert in the relevant field.
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`2.
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`I have been asked to provide my independent analysis regarding the
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`inter partes review initiated by petitioner Semiconductor Components Industries,
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`LLC d/b/a ON Semiconductor (“ON Semiconductor” or “Petitioner”) related to
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`U.S. Patent No. 7,834,605 (“the ’605 patent”), which is assigned to Patent Owner.
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`I have been asked to consider what one of ordinary skill in the art as of the
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`effective filing date of the ’605 patent would have understood from the ’605
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`patent, including scientific and technical knowledge related to the ’605 patent. I
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`have also been asked to consider issues relating to the substitute claims proposed
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`by Patent Owner.
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`3.
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`I understand that Patent Owner is presently moving to amend U.S.
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`Patent No. 7,834,605 (“the ’605 patent”). I further understand that the motion
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`seeks to cancel claims 1, 2, 5, and 9 and substitute them with proposed substitute
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`claims 13, 14, 15, and 16, respectively. In particular, PI’s proposed amendment
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`adds a new limitation to original independent claim 1 (resulting in proposed
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`substitute independent claim 13) and modifies dependent claims 2, 5, and 9 such
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`Case IPR2016-01600
`Attorney Docket No: 10256-0021IPC
`that they depend from proposed substitute independent claim 13 (resulting in
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`proposed substitute dependent claims 14-16).
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`4.
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`I understand that proposed substitute claim 13 retains all of the
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`original elements of original claim 1 and further narrows the claim by additionally
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`requiring that: “for each of a plurality of consecutive control signal cycles each
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`having a first state and a second state, the variable current limit threshold
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`increases during at least a portion of the first state of each control signal cycle
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`and decreases during at least a portion of the second state of each control signal
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`cycle.”
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`5. My independent analysis here is guided by my understanding and
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`experience as a person of at least ordinary skill in the art as of the effective filing
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`date of the ’605 patent, which strictly for purposes of my analysis here is assumed
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`to be the filing date of the ’605 patent—September 27, 2001.
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`6.
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`I am being compensated for my work in connection with this IPR
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`proceeding. My compensation is not in any way contingent on the substance of my
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`opinions or the outcome of these proceedings.
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`
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`SUMMARY OF OPINIONS
`7.
`PI’s proposed substitute claims (1) do not enlarge the scope of the
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`original claims, (2) meet the requirements of 35 U.S.C. § 112, and in particular the
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`Case IPR2016-01600
`Attorney Docket No: 10256-0021IPC
`requirements for written description and enablement, and (3) are patentable over
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`all known prior art.
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`8.
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`In summary, each of the proposed substitute claims includes a new
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`narrowing claim limitation (either directly in proposed substitute independent
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`claim 13 or indirectly through dependent claim language) and thus it is my opinion
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`that the substitute claims do not enlarge the scope of the original claims.
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`9.
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`In addition, it is also my opinion that each and every claim element of
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`the proposed substitute claims is supported by the specification of Provisional
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`Application No. 60/325,642, to which the ’605 patent claims priority and thus
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`meets the requirements of 35 U.S.C. § 112.
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`10. Next, it is my opinion that the proposed substitute independent claim
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`13 distinguishes all of the proposed substitute claims over the de Sarte (Ex. 1005)
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`reference at issue in this proceeding, the Maige reference (Ex. 1008) cited in the
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`Federal Circuit’s holding Power Integrations, Inc. v. Fairchild Semiconductor Int'l,
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`Inc., 843 F.3d 1315, 1336 (Fed. Cir. 2016), which cites my own opinions from the
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`District Court litigation regarding the ’605 patent, and all other known prior art.
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`11. Further, it is my opinion that the language used in the proposed
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`substitute claims would be readily understood by a person of ordinary skill in the
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`art at the time of invention and does not require construction.
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`Case IPR2016-01600
`Attorney Docket No: 10256-0021IPC
` BACKGROUND AND QUALIFICATIONS
`12.
`I have extensive experience in the design of power electronics
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`spanning a career of over 30 years in the field. My most relevant expertise
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`includes the design and operation of power electronics, magnetics, power quality,
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`and power management integrated circuits, and dc-to-dc converter topologies
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`including forward, flyback, full-bridge, push-pull, boost, and buck. The following
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`paragraphs summarize some of my experience that is relevant to the technologies
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`described within the ’605 patent. My curriculum vitae is available in this matter as
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`Exhibit 2015 and gives a more full overview of my experience and expertise.
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`13. My industry experience includes work as a Senior Design Engineer
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`designing power electronics for aerospace applications requiring top secret security
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`clearance. I also worked as a Senior Design Engineer for Linear Technology
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`Corporation designing high performance analog integrated circuits for power
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`management. I have specific experience designing flyback power controllers,
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`including work done at Linear where I worked on the design of the LTC3805 and
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`LTC3805-5 in flyback applications. In addition, I designed the LTC3705/25 – a
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`portion of a highly innovative chipset in BiCMOS process – from scratch.
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`14.
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`In addition to my industry experience, I was on the faculty in the
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`department of Electrical and Computer Engineering at North Carolina State
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`University in Raleigh, North Carolina, from 1987 to 2001, first as an Assistant
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`Case IPR2016-01600
`Attorney Docket No: 10256-0021IPC
`Professor and then promoted to Associate Professor and awarded tenure in 1993.
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`My academic research focused on power electronics, power semiconductor
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`devices, magnetics, power quality, power systems, and motor drives. Since that
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`time, I have been an adjunct professor at N.C. State University, working with the
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`Future Renewable Electric Energy Delivery Management (FREEDM) Systems
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`Center, a National Science Foundation Engineering Research Center.
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`15.
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`I also have extensive consulting experience in the area of power
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`electronics. My consulting experience includes research and design for numerous
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`companies and products in the areas of LED lighting, intravascular implantable
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`defibrillators, grid-connected photovoltaics, magnetically coupled power for
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`portable devices and development of a hybrid electric propulsion system for a
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`powered parafoil.
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`16.
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`I have eight issued U.S. patents in the area of power converters, power
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`electronics, power systems, and related methods and devices. I’ve authored
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`numerous peer reviewed articles in the area of power electronics, and I served as
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`the Editor in Chief of the IEEE Transactions on Power Electronics from 2000 to
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`2002. From 2009 to 2012, I served as the Editor in Chief of the Newsletter for the
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`IEEE Power Electronics Society.
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`I earned my BS in Electrical Engineering from Duke University in
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`17.
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`1979, summa cum laude, and my M.S. and Ph. D. in Electrical Engineering, also
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`from Duke, in 1981 and 1984 respectively.
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`18. Based on my experience and education, I believe that I am qualified to
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`opine as to knowledge and level of skill of one of ordinary skill in the art at the
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`time of the invention of the ’605 patent (which I further describe below) and what
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`such a person would have understood at that time, and the state of the art during
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`that time. Indeed, I have worked with many such persons during my career.
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` BASIS FOR OPINIONS
`19. My opinions and analysis set forth in this Declaration are based on my
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`education, training, and experience as summarized above and detailed in my CV,
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`as well as my review of the ’605 patent, the file history, the prior art on which the
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`Board instituted these IPR proceedings, and all of the prior art that that has been
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`previously considered in connection with this patent. I have also carefully
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`reviewed the declaration from Douglas Holberg (Ex. 1003), which ON
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`Semiconductor submitted in support of its Petition in this IPR proceeding. I have
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`also reviewed the Petition and each of the accompanying documents that are cited
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`in the Petition in addition to those specifically mentioned below. I have also
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`considered the Board’s Decision (Paper 11) dated February 17, 2017, that
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`instituted this IPR proceeding.
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`Case IPR2016-01600
`Attorney Docket No: 10256-0021IPC
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`FIELD OF ART
`20. The ’605 patent generally relates to switched mode power supplies.
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`As such, it is my opinion that the ’605 patent is in the field of electrical
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`engineering, and a complete understanding of the ’605 patent requires experience
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`and appreciation of the challenges in design, development, and commercialization
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`of switched mode power supply systems.
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` PERSON OF ORDINARY SKILL IN THE ART
`21.
`I understand that the teaching of the prior art is viewed through the
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`eyes of a person of ordinary skill in the art at the time of the invention. To assess
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`the level of ordinary skill in the art, I understand that one can consider the types of
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`problems encountered in the art, the prior solutions to those problems found in
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`prior art references, the speed with which innovations were made at that time, the
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`sophistication of the technology, and the level of education of active workers in the
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`field.
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`22. Based upon my knowledge and experience in this field and my review
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`of the ’605 patent, I believe that a person of ordinary skill in the art at the time of
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`the invention (“POSITA” or “person of skill”) would have had a bachelor’s degree
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`in electrical engineering, physics, or a related discipline, and at least two to three
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`years of relevant experience in the field of power electronics or similar circuitry.
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`Additional education, such as an advanced degree in electrical engineering or a
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`related field, might substitute for some of the experience, and substantial
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`experience might substitute for some of the educational background. My analysis
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`is thus based on the perspective of a POSITA having at least this level of
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`knowledge and skill in the time leading up to the ’605 patent. I have been
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`informed that the filing date of the ’605 patent is September 21, 2001 and I have
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`applied this timeframe in my analysis as being the relevant time of the ’605 patent.
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` THE ’605 PATENT
`A. Technology Background: “Switch-mode” power supplies and the
`cycle-by-cycle current limit
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`23.
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`It is well known in the art that all electronic devices (i.e., electronic
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`
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`“loads”) use electrical power to operate and thus typically require the use of a
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`power supply to provide regulated electrical power. The ’605 patent relates to
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`“off-line” switch-mode power supplies, also known as switching power supplies,
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`such as would be typically used for charging a cell phone or a laptop computer.
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`24. Switching power supplies are used to achieve proper interfacing
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`between a power source, such as an A/C source or battery, and a load, such as a
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`portable computer. If the source is at a voltage that is too high or too low for the
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`load, a switching power supply can be used to draw power from the source and
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`provide it to the load at the proper voltage. This transfer of power is controlled by
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`controlling the turning on and off of an electrical switch (typically a transistor) to
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`provide a steady output voltage or output current. A graph depicting a constant-
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`Case IPR2016-01600
`Attorney Docket No: 10256-0021IPC
`current and constant-voltage regulator output is shown below and is found at FIG.
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`5 of the ’605 patent.
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`25.
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`In the manner shown above, the switching power supplies as disclosed
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`in the ’605 patent are intended to regulate the power delivered to their output. This
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`regulation may be of the output voltage or the output current. Together regulating
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`both of these values achieves output power regulation (where output power =
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`output voltage x output current). The technical tutorial discussion below focuses
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`on the basic operation and typical components of a power supply that regulates the
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`output voltage and output current to a load. This is provided as background to the
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`Case IPR2016-01600
`Attorney Docket No: 10256-0021IPC
`art as would be understood by a person of ordinary skill in the art reading the ’605
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`patent. Both the ’605 patent and the de Sarte reference referred to herein include
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`the same basic fundamental components of a power supply that are described
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`briefly below.
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`26. A capacitor is an electrical element that can store electrical charge.
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`Electrical current (the flow of electrical charge) drawn by the load is provided by
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`charge stored on the regulator output capacitor.
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`27. The regulator output voltage depends on the level of charge stored in
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`the output capacitor. As the load drains charge off the capacitor, the regulator
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`output voltage will decrease. To maintain a steady regulator output voltage, the
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`regulator must recharge the output capacitor as charge is drained off by the load.
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`As shown in the figure below, the current to recharge the output capacitor is
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`provided by a power source such as 110V wall socket.
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`28. Since the voltage across the output capacitor depends on the amount
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`of charge it stores, regulating that voltage requires that the charge put into the
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`capacitor by the regulator match the amount of charge taken out of the capacitor by
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`the load current. A switching voltage regulator recharges its output capacitor by
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`providing pulses of recharge current. In the example shown below, for an average
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`level of load current, the recharging current flows half the time. The average
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`recharge current, over time, matches the level of the load current, and the regulator
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`output voltage will remain steady.
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`29.
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`If the load current level changes, the average level of recharging
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`current must also change to maintain a steady level of charge in the capacitor. This
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`can be achieved by modulating the pulse width (“on-time”) of each recharge pulse.
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`For example, if the load current level increases (e.g., if the load is a laptop and its
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`screen brightness is turned up), then the recharge pulse width will be increased by
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`the regulator to provide the necessary discharge/recharge match. If the load
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`current level decreases (e.g., if the load is a laptop and its screen brightness is
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`turned down), then the recharge pulse width will be decreased by the regulator to
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`provide the necessary discharge/recharge match. The figure below shows recharge
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`pulse timing for three different levels of load current.
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`30. Note that the recharge pulse frequency remains fixed, but the amount
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`of time that the recharge current is flowing during each pulse cycle varies. This is
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`known as pulse width modulation. Switching voltage regulators can use a
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`transformer and a switch to provide the recharging current pulses.
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`31. A transformer is an energy transfer device and is formed by having
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`two or more coils of wire wound around the same core. As seen in the figure
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`below, in a switching regulator, an input voltage source can be connected to one
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`end of one of the transformer windings (the primary winding), and the switch can
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`be connected to the other end of that winding.
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`Attorney Docket No: 10256-0021IPC
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`32. When the switch is turned on, current starts to flow through both the
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`primary winding and the switch, and builds up (increases in value over time) as
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`long as the switch is ON. This also increases the magnetic field in the transformer.
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`33. When the switch turns off, current in the primary winding stops
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`flowing, and the collapsing magnetic field induces current flow in the other
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`(secondary) windings. Secondary current can be steered to the output capacitor to
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`recharge it.
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`Case IPR2016-01600
`Attorney Docket No: 10256-0021IPC
`34. The amount of energy transfer depends on the level of current
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`previously built up in the primary winding, and thus the percentage of time that the
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`switch was on during each on/off switching cycle. For a given level of load
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`current, if the duty cycle is too high, there is more recharging from energy transfer
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`than there is discharging by load current. This causes the regulator output voltage
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`to increase. If duty cycle is too low, there is less recharging from energy transfer
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`than discharging by load current, and the regulator output voltage will decrease.
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`Regulators typically use feedback to maintain a steady output voltage. As shown
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`below, the regulator monitors output voltage and uses a signal from the output to
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`adjust the switch timing (e.g., the pulse width) to be just right.
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`Case IPR2016-01600
`Attorney Docket No: 10256-0021IPC
`35. Switching regulators often use an oscillator to provide system timing.
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`The oscillator puts out a periodic series of pulses to turn on the switch at the
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`beginning of each switch cycle. In pulse width modulation, the switch duty cycle
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`is controlled by determining when to turn the switch off during each switching
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`cycle.
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`36.
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`Integrated circuit power supply controller chips often provide other
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`functions in addition to the basic regulation function. In the case of the ’605
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`patent, the additional function at issue is a current limit, which prevents excessive
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`and perhaps destructive current flow in a power switch on a cycle-by-cycle basis.
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`In particular, by regulating the maximum current output by the regulator and the
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`maximum voltage output by the regulator, a person of skill in the art can control
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`the maximum power output by the regulator. The maximum power output by the
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`regulator must be accurately known in order to ensure that the components of the
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`power supply are sufficient to handle all operating modes of the power supply.
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`The Invention of the ’605 Patent
`
`B.
`
`37. As explained above, and as expressly stated in the ’605 patent, one
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`exemplary form of power supply that is efficient and, at the same time, provides
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`acceptable output regulation to supply power to electronic devices is the “switch-
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`mode” power supply. Ex. 1001 at 1:28-32. In many electronics, especially low
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`power electronics that use wall outlet supplied power – i.e., “off line” power –
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`Case IPR2016-01600
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`during the normal operating load range of the power supply, an approximately
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`constant output voltage is required when the load current is below an output
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`current threshold (e.g., when the load current is not at the maximum). Id. at 1:32-
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`36. In addition to regulating the output voltage, the output current is generally
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`regulated to be approximately constant at or above that threshold, at which point,
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`the output voltage may drop its regulated voltage – in this context, this is referred
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`to as the output voltage threshold. Id. at 1:36-38.
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`38. For several reasons, it is desirable to limit the maximum output
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`current of a power supply because by controlling the maximum voltage and the
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`maximum current (which occurs at the output voltage threshold), you control the
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`maximum output power of the power supply. A load device, operating at its
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`regulated voltage, might draw more current from the power supply because it is
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`performing more functions at once. For example, a laptop computer that is playing
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`music and maintaining an internet connection would draw more current than one
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`sitting idle. A power supply should be designed to accommodate whatever current
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`the intended load device requires. But if the device attempts to draw too much
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`current, perhaps due to a fault condition, the power supply should also be capable
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`of preventing damage due to overload. Dangerous conditions, such as overheating,
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`may develop if a load is able to draw too much current.
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`39. The ’605 patent relates to current limit circuits used in switching
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`power supplies. The patent describes a switched mode power supply in which the
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`output current below the output voltage threshold, is regulated to be approximately
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`constant. Ex. 1001 at 3:1-3. As is explained, in known, prior art, power supplies
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`the output current level at the output voltage threshold is typically sensed at the
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`output of the power supply to provide feedback to a regulator circuit coupled to the
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`primary winding of the power supply. Id. at 3:5-13. But, if the approximately
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`constant current functionality is achieved without feedback from the secondary
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`winding side of the power supply, the output current at the output voltage threshold
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`is a function of a peak current limit of the power supply (i.e., the current limit of
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`the power supply’s power switch). Id. The patent describes how this peak current
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`limit is controlled to thereby control the maximum output current.
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`40.
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`In particular, the patent discloses a current limit circuit and method
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`that enable the power supply to maintain an approximately constant output current
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`below the output voltage threshold over varying input voltage (i.e., over variations
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`in supplied input voltage at one location or variations in input voltage levels
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`around the world.). Ex. 1001 at 1:50-2:18. Broadly speaking, the disclosed
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`invention achieves this by increasing the current limit threshold during the on-time
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`of the power switch. The patent explains in detail why this achieves the desired
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`result.
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`Case IPR2016-01600
`Attorney Docket No: 10256-0021IPC
`41. One design challenge related to providing an output current limit
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`relates to use of power supplies and chargers in international markets with different
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`input line voltages. It is desirable both to manufacturers and consumers that power
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`supplies should function identically whether in France (240V) or the United States
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`(120V). The ’605 patent’s claimed invention reduces the variation of the output
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`current at the output voltage threshold by reducing the peak current limit variation
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`with changing input voltage. Id. at 3: 15-17. In general, the intrinsic peak current
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`limit is set by internal circuitry in the regulator and is a fixed, constant current
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`limit. Id. at 3:17-18.
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`42. When implementing the current limit functionality, in an ideal power
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`supply, once the drain current through the switch of the switch-mode power supply
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`reaches a current limit threshold, the switching cycle should, in theory, terminate
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`immediately. Id. at 3:17-22. As explained by the ’605 patent, however, “a fixed
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`delay is inherent from the time the threshold is reached until the power metal oxide
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`semiconductor field effect transistor (MOSFET) is finally disabled.” Id. at 3:22-
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`24. And, “[d]uring this delay, the drain current continues to ramp up at a rate equal
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`to the direct current (DC) input voltage divided by the primary inductance of the
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`transformer (drain current ramp rate).” Id. at 3:25-27. Therefore, the actual (as
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`opposed to ideal) current limit “is the sum of the intrinsic current limit threshold
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`and a ramp-rate dependent component (the overshoot), which is the drain current
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`Case IPR2016-01600
`Attorney Docket No: 10256-0021IPC
`ramp rate multiplied by the fixed delay.” Id. at 3:27-31. Thus, at higher DC input
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`voltages, the actual current ramps to a higher level above the intrinsic current limit
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`level than at low DC input voltages. Id. at 3:31-33. This can result in variations in
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`the output current delivered to the load at the output voltage threshold over a range
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`of input line voltages. Id. at 3:33-35. The effect described above is illustrated
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`below:
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`43. Shown above, the slope of the primary current is related to the input
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`line voltage – i.e., if the input line voltage is higher, then the slope is steeper. But,
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`while the slope changes, the time it takes for the regulator to react to the current
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`limit being reached, i.e. the time delay, is not dependent on the slope of the
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`primary current. This is because the delay is largely due to the operation of the
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`digital logic and propagation delays associated with the various signals between
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`the output of the current limit comparator and the gate of the power switch
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`Case IPR2016-01600
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`transistor. Because there is a delay between when the current limit threshold is
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`reached and when the switch is turned off, additional current flows through the
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`switch during the delay time period; this additional current is proportional to the
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`input voltage because the input voltage determines the slope of the rise of the
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`switch current.
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`44. As explained by the patent, the time elapsed from the beginning of the
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`cycle can be used to gauge the input voltage. Id. at 3:50-51. As further explained
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`by the patent, in order to create an intrinsic current limit which decreases relative
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`to the DC input voltage, the time elapsed during which the switch is on can be
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`used. Id. at 3:52-55. The output of a ramping oscillator is described as one
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`method by which the time elapsed may be detected by the circuit. Id. at 3:63-65.
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`Thus, “one way to increase the intrinsic current limit linearly as a function of the
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`elapsed time would then be to derive a linearly increasing (with elapsed time)
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`current source and deliver this current to the resistor” and “[t]his linearly
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`increasing (with elapsed time) current source can thus be derived from the
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`oscillator. Id. at 4:1-12.
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`Case IPR2016-01600
`Attorney Docket No: 10256-0021IPC
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`45. FIG. 1 of the ’605 patent (above) shows an embodiment of the circuit
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`used to form the increasing current limit signal. The intrinsic current limit is, to
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`the first order proportional to the voltage on node 22. Id. at 4:29-30. As explained
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`above, the goal of the invention is to generate an intrinsic current limit proportional
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`to the time elapsed in the switching cycle. Id. at 4:30-32. The saw tooth waveform
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`20 can be used to accomplish this goal. As the base voltage of NPN transistor 30
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`rises, the emitter voltage also rises at the same rate and thus the current through
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`resistor