Texas Instruments Incorporated

Patent Trials and Appeals Board

Oct 29, 2020

2019006291 (P.T.A.B. Oct. 29, 2020)

UNITED STATES PATENT AND TRADEMARK OFFICE
UNITED STATES DEPARTMENT OF COMMERCE
United States Patent and Trademark Office
Address: COMMISSIONER FOR PATENTS
P.O. Box 1450
Alexandria, Virginia 22313-1450
www.uspto.gov
APPLICATION NO. FILING DATE FIRST NAMED INVENTOR ATTORNEY DOCKET NO. CONFIRMATION NO.
14/494,982 09/24/2014 Andrew Bernard Keogh TI-74420 6831
23494 7590 10/29/2020
TEXAS INSTRUMENTS INCORPORATED
P O BOX 655474, MS 3999
DALLAS, TX 75265
EXAMINER
LABOY ANDINO, IVAN A
ART UNIT PAPER NUMBER
2839
NOTIFICATION DATE DELIVERY MODE
10/29/2020 ELECTRONIC
Please find below and/or attached an Office communication concerning this application or proceeding.
The time period for reply, if any, is set in the attached communication.
Notice of the Office communication was sent electronically on above-indicated "Notification Date" to the
following e-mail address(es):
uspto@ti.com
PTOL-90A (Rev. 04/07)
UNITED STATES PATENT AND TRADEMARK OFFICE
BEFORE THE PATENT TRIAL AND APPEAL BOARD
Ex parte ANDREW BERNARD KEOGH, JOSEPH MICHAEL LEISTEN,
and WILLIAM JAMES LONG

Appeal 2019-006291
Application 14/494,982
Technology Center 2800
Before JEFFREY B. ROBERTSON, DEBRA L. DENNETT, and
MERRELL C. CASHION, JR., Administrative Patent Judges.
DENNETT, Administrative Patent Judge.
DECISION ON APPEAL1
Pursuant to 35 U.S.C. § 134(a), Appellant2 appeals from the
Examiner’s decision to reject claims 1–20, which constitute all the claims

1 In our Decision, we refer to the Specification (“Spec.”) of Application No.
14/494,982 filed September 24, 2014 (“the ’982 App.”); the Final Office
Action dated September 27, 2018 (“Final Act.”); the Supplemental Appeal
Brief filed March 27, 2019 (“Appeal Br.”); the Examiner’s Answer dated
June 28, 2019 (“Ans.”); and the Reply Brief filed August 26, 2019 (“Reply
Br.”).
2 We use the word “Appellant” to refer to “applicant” as defined in 37
C.F.R. § 1.42. Appellant identifies the real party in interest as Texas
Instruments Incorporated. Appeal Br. 2.
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pending in this application. See Final Act. 1. We have jurisdiction under
35 U.S.C. § 6(b).
We REVERSE.
STATEMENT OF THE CASE
The ’982 Application relates to flyback switching power supplies.
Spec. ¶ 2. The Specification describes a flyback converter as shown in FIG.
1, reproduced below from the ’982 Application:

FIG. 1 is a circuit diagram of a prior art embodiment of a flyback
voltage converter. Id. ¶ 12. According to the Specification, flyback
converter 100 comprises transformer 140 with at least three windings
typically: primary winding 150, secondary winding 160, and bias winding
(auxiliary winding) 140. Id. ¶ 3. Flyback converter 100 operates by turning
on main primary switch 145, thereby applying the input voltage from storage
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capacitor 135 across primary winding 150 for a period of time referred to as
“on-time.” Id. The input voltage appears across both secondary winding
160 and bias winding 170 during this interval, but with a negative polarity
due to the winding polarities. Id. The negative voltage on secondary
winding 160 and bias winding 170 keeps diode rectifiers 132 and 133 on
those winding reverse-biased. Id.
When primary switch 145 is turned off, the current in primary
winding 150 continues to flow in the primary inductance, charging the total
capacitance on the primary switch. Id. ¶ 4. The switch voltage rises until
the scaled reflected secondary voltage becomes sufficiently positive that
secondary diode rectifier 132 becomes forward-biased and turns on. Id. The
current that was flowing in the primary transfers to secondary winding 160,
transferring the energy that was stored during the on-time into output
capacitor 180 and the output load. Id. The secondary current decays over
time at a rate proportional to the secondary-reflected inductance and the
output voltage.
The ’982 Application relates that if bias winding is sampled (feedback
voltage is sensed) while the secondary current is still flowing, there will be a
sensing error due to voltage drops resulting from secondary resistance,
making the feedback voltage inaccurate. Id. ¶ 29. If bias winding is
sampled after the current has decayed to zero, there will be a gross sensing
error, since the winding voltage is no longer related to Vout at all. Id.
According to Appellant, to mitigate or compensate these types of
sensing inaccuracies, the invention provides a scheme in which a controller
in the primary side is configured to sample a feedback voltage before the
secondary current has fully decayed to zero, and determine an output voltage
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based on the feedback voltage offset by an offset voltage that is attributable
by the error sources from the secondary side of the power system. Appeal
Br. 3.
Claim 1 is representative of the ’982 Application’s claims and is
reproduced below from the Claims Appendix of the Appeal Brief.
1. A system comprising:
a transformer having a primary winding, a secondary
winding and an auxiliary winding;
a primary side switch coupled to the primary winding; and
a controller coupled between the auxiliary winding and the
primary side switch, the controller configured to:
sample a feedback voltage during a secondary decay
period and before a secondary current of the secondary winding
decayed to zero;
determine an offset voltage based on an estimated
secondary resistance and a current of the auxiliary winding when
the feedback voltage is sampled;
determine an output voltage based on a difference between
the feedback voltage and the offset voltage; and
modulate the primary switch based on the output voltage.
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Application 14/494,982

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REFERENCES
The Examiner relies on the following prior art:
Name Reference Date
Lopez-Santillana et al.
(“Lopez-Santillana”)
US 2004/0047166 A1 Mar. 11, 2004
Muegge et al.
(“Muegge”)
US 2004/0052095 A1 Mar. 18, 2004
McDonald et al.
(“McDonald”)
US 2006/0083032 A1 Apr. 20, 2006
Huynh et al.
(“Huynh ’000”)
US 2010/0054000 A1 Mar. 4, 2010

REJECTIONS
The Examiner rejects claims under 35 U.S.C. § 1033 as follows: (1)
claims 1–12 and 15–19 as unpatentable over McDonald in view of Muegge;
(2) claims 13 and 20 as unpatentable over McDonald in view of Muegge and
Lopez-Santillana; and (3) claim 14 as unpatentable over McDonald in view
of Muegge and Huynh ’000. Final Act. 4–18.
OPINION
We review the appealed rejections for error based upon the issues
identified by Appellant and in light of the arguments and evidence produced
thereon. Ex parte Frye, 94 USPQ2d 1072, 1075 (BPAI 2010) (precedential),
(cited with approval in In re Jung, 637 F.3d 1356, 1365 (Fed. Cir. 2011))
(“[I]t has long been the Board’s practice to require an applicant to identify

3 Because this application was filed after the 16 March 2013, effective date
of the America Invents Act, we refer to the AIA version of the statute.

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the alleged error in the [E]xaminer’s rejections.”). After considering the
evidence presented in this Appeal and each of Appellant’s arguments,
Appellant persuades us of reversible error in the Examiner’s rejection of
claims 1–20.
Claims 1, 8, and 15 are independent claims, and each requires
sampling a feedback voltage during a secondary decay period and before a
secondary current of the secondary winding decayed to zero in similar
language. See Appeal Br. 12–14.
Appellant argues that claim 1 is representative of the claims for the
purpose of demonstrating the deficiencies of McDonald in view of Muegge
under all three grounds of rejection. Appeal Br. 5. Appellant makes no
other arguments for patentability of any claim. See generally id. Therefore,
we limit our review to consideration of claim 1.
The Examiner finds that McDonald teaches most of the limitations of
claim 1, including teaching the controller is configured to “sample a
feedback voltage during a secondary decay period and before a secondary
current of the secondary winding decayed to zero.” Final Act. 4. The
Examiner finds that McDonald “fails to expressly disclose the transformer
comprising an auxiliary winding, wherein the controller is coupled between
the auxiliary winding and the primary side switch, and wherein the offset
voltage is determined based on the current of the auxiliary winding when the
feedback is sampled.” Id. at 5. The Examiner finds that Muegge teaches a
transformer comprising an auxiliary winding for sampling the feedback
voltage. Id.
The Examiner determines that it would have been obvious to one of
ordinary skill in the art before the effective filing date of the invention to
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incorporate Muegge’s auxiliary winding to McDonald’s transformer for
sampling the feedback voltage, since it is a well-known monitoring
technique alternative used in isolated flyback converters with primary side
regulation operating in continuous conduction mode. Id. at 6.
Appellant argues that McDonald teaches a controller that computes
the secondary voltage as a predefined function so that the controller is
operable to control the secondary voltage without utilizing feedback input
received from the secondary side. Appeal Br. 6. Thus, Appellant argues
McDonald does not teach a controller configured to “sample a feedback
voltage,” as the reference explains the benefit of not receiving feedback
from the secondary side. Id. According to Appellant, even if one of
ordinary skill in the art were to view the primary side voltage as a feedback
voltage, McDonald still fails to teach or suggest the timing required by claim
1, i.e., sample a feedback voltage “during a secondary decay period and
before a secondary current of the secondary winding decayed to zero.” Id. at
6–7. Appellant argues that Muegge does not cure McDonald’s deficiencies.
Id. at 7.
In the Answer, the Examiner suggests that feedback that is sampled
need not come from the secondary side, and could be obtained from the
primary side. Ans. 4 (citing Appellant’s Specification and claims). The
Examiner finds that McDonald “is merely stating that the secondary voltage
can be control [sic] by sensing the feedback voltage from the primary side
without the need of receiving inputs directly from the secondary side.” Id.
However, this finding lacks support in McDonald. See Reply Br. 2. The
only instances in which McDonald mentions “feedback” are those discussing
regulation by the controller of secondary voltage output without receiving
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feedback input from a secondary side of a transformer. See, e.g., McDonald
Abst., ¶¶ 8, 10, 18, 19, and 26. McDonald does not mention a need for or
use of feedback from the primary side. See generally id. Thus, “sampl[ing]
a feedback voltage,” as claim 1 recites, does not appear to be taught by
McDonald. The Examiner does not rely on Muegge for teaching sampling a
feedback voltage.
Responding to Appellant’s argument that McDonald fails to teach the
required timing for sampling a feedback voltage (see Appeal Br. 6), the
Examiner cites to McDonald paragraph 26 and FIG. 3A. Ans. 5. Paragraph
26 as quoted by the Examiner states:
[T]he controller 130 computes the secondary voltage 171 as a
predefined function of the plurality of the inputs 134 when the
primary switch 140 is open.
The Examiner then relies on McDonald FIG. 3A as evidence that the
secondary current does not decay to zero. Ans. 5. FIG. 3A illustrates
waveforms associated with McDonald’s flyback converter. McDonald ¶ 13.
The Examiner concludes that McDonald paragraph 26 and FIG. 3A make it
“clear that the sampling voltage is being performed during a secondary
decay and before the secondary current of the secondary winding decayed to
zero.” Id. at 6 (emphasis added).
However, neither paragraph 26 nor any other portion of McDonald
discloses sampling or when sampling should occur. See generally
McDonald. Therefore, the Examiner’s conclusion is not supported by facts
in the record.
“The PTO has the burden under section 103 to establish a prima facie
case of obviousness.” In re Fine, 837 F.2d 1071, 1074 (Fed. Cir. 1988)
(citing In re Piasecki, 745 F.2d 1468, 1471–72 (Fed. Cir. 1984)). The
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burden is satisfied only by showing some objective teaching in the prior art
or that knowledge generally available to one of ordinary skill in the art
would lead that individual to combine the relevant teachings of the
references. Id. (citing In re Lalu, 747 F.2d 703, 705 (Fed. Cir. 1984)). Here,
the Examiner fails to show that McDonald in view of Muegge teach or
suggest the claimed invention. The “structural similarity” needed for a
prima facie case is lacking, as McDonald teaches neither the sampling nor
timing recitations in the claims. See In re Dillon, 919 F.2d 688, 692
(Fed.Cir.1990) (en banc) (“[S]tructural similarity between claimed and prior
art subject matter, proved by combining references or otherwise, where the
prior art gives reason or motivation to make the claimed compositions,
creates a prima facie case of obviousness.”). When the references cited by
the Examiner fail to establish a prima facie case of obviousness, the rejection
is improper and will be overturned. Fine, 837 F.2d at 1074.
We do not sustain the rejection of claim 1 as obvious over
McDonald in view of Muegge. For the same reasons, we do not
sustain the rejections of claims 2–20 over these references, with or
without the additional cited references.
CONCLUSION
The Examiner’s decision to reject claims 1–20 is REVERSED.
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DECISION SUMMARY
Claim(s)
Rejected
35 U.S.C. § Reference(s)/Basis Affirmed Reversed
1–12, 15–
19
103 McDonald, Muegge 1–12, 15–
19
13, 20 103 McDonald, Muegge,
Lopez-Santillana
13, 20
14 103 McDonald, Muegge,
Huynh ’000
14
Overall
Outcome
1–20
REVERSED