Seeman, Michael D.

Patent Trials and Appeals Board

Jan 27, 2020

15073964 - (D) (P.T.A.B. Jan. 27, 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.
15/073,964 03/18/2016 Michael D. Seeman TI-76165 1008
23494 7590 01/27/2020
TEXAS INSTRUMENTS INCORPORATED
P O BOX 655474, M/S 3999
DALLAS, TX 75265
EXAMINER
AHMED, YUSEF A
ART UNIT PAPER NUMBER
2838
NOTIFICATION DATE DELIVERY MODE
01/27/2020 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 MICHAEL D. SEEMAN
____________________

Appeal 2019-001975
Application 15/073,964
Technology Center 2800
____________________

Before MICHELLE N. ANKENBRAND, MERRELL C. CASHION, JR.,
and SHELDON M. McGEE, Administrative Patent Judges.

CASHION, Administrative Patent Judge.

DECISION ON APPEAL

STATEMENT OF CASE

Appellant1 appeals under 35 U.S.C. § 134(a) from the Examiner’s
Final Rejection of claims 1–20. We have jurisdiction under 35 U.S.C.
§ 6(b).
We REVERSE.

1 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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Application 15/073,964

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The invention is generally directed to a hysteretic control mechanism
for power converters. Spec. ¶ 1. More specifically, the invention is directed
to an apparatus comprising a hysteretic control mechanism for power
converters that has a hysteretic comparator for use in a distributed power
architecture (DPA). Id. ¶ 3. In general, DPAs allow a primary system
power supply to receive an input voltage and reduce it to one or more
intermediate system voltages to be bussed to a number of printed circuit
board (PCB) sub-assemblies. Id. ¶ 4. The Specification explains that
“[e]ach PCB sub-assembly typically includes a DC-DC converter that will
convert the system supply voltage to one (or more) well regulated supply
voltages for the sub-assembly PCB.” Id. The invention seeks to improve
the efficiency of the power convertors compared to prior art converters by
using a hysteretic controller in the power converter, where the hysteretic
controller has a hysteretic comparator. Id. ¶¶ 10–12, 50. The Specification
discloses that hysteretic controllers are known in the art as suitable for
regulating voltages by “inherently provid[ing] lower quiescent current and
excel[ling] in extreme down conversion applications common in PoL [or
points of load] converters today.” Id. ¶¶ 8–9. Claim 1 illustrates the subject
matter on appeal and is reproduced below:
1. An apparatus, comprising:
a power converter including:
a transformer having a primary side interfacing an input
voltage terminal, and a secondary side interfacing an output
voltage terminal;
a primary side switch coupled between the input voltage
terminal and the primary side of the transformer;

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an inductor having a first terminal coupled to the
secondary side of the transformer, and a second terminal
coupled [to] the output voltage terminal;
a secondary side switch coupled between the first
terminal of the inductor and a ground terminal; and
a hysteretic controller having:
a hysteretic comparator including a first input, a
second input, and an output, the first input configured to
receive a sensed current from the inductor, the second
input configured to receive a differential voltage
representing a potential difference between an output
voltage at the output voltage terminal and a reference
voltage;
a pulse sequencer coupled to the output of the
hysteretic comparator; and
a dead-time generation circuit configured to
provide a first on-time signal to the primary side switch
and a second on-time signal to the secondary side switch
based on a pulse signal received from the pulse
sequencer.
Independent claim 14 is essentially directed to the converter
used in claim 1.
Appellant (see generally Appeal Br.) requests review of the
Examiner’s rejection of claims 1–20 under 35 U.S.C. § 103(a) as
unpatentable over Fahlenkamp (US 2009/0086512 A1, published April 2,
2009) and Dearborn (US 2012/0013322 A1, published January 19, 2012).
Appeal Br. 7; Final Act. 3, 8.2

2 For brevity, we consolidated the two rejections statements the Examiner
presents in the Non-Final Action into a single rejection statement because
both rely on the same evidentiary references.
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OPINION
After review of the respective positions the Appellant presents in the
Appeal and Reply Briefs and the Examiner presents in the Final Action and
the Answer, we REVERSE for the reasons the Appellant provides. We add
the following for emphasis.
Claim 1
Independent claim 1 recites a power converter comprising a hysteretic
comparator including a first input configured to receive a sensed current
from the inductor.3
The Examiner finds that Fahlenkamp teaches an apparatus having a
power converter comprising a controller and comparator that includes a first
input, but that differs from the subject matter of claim 1 in that Fahlenkamp
does not disclose the controller and comparator as being a hysteretic
controller and a hysteretic comparator, or a hysteretic comparator including
a first input configured to receive a sensed current from the inductor. Final
Act. 3–4. The Examiner turns to Dearborn for the noted missing features.
Id. at 4. The Examiner finds that Dearborn teaches a hysteretic controller as
a known means to achieve an optimum response to a disturbance in any
negative feedback control system. Final Act. 4; see Dearborn ¶ 2, Figures
3–5. The Examiner also finds that Dearborn teaches the hysteretic controller
as comprising a hysteretic comparator. Final Act. 4 (citing Dearborn Figures
3, 4); see Dearborn claims 5, 6. In the Answer, the Examiner asserts that

3 Independent claim 14 also recites a power converter comprising a
hysteretic comparator including a first input configured to receive a sensed
current from inductors. Accordingly, we limit our discussion to independent
claim 1, with the understanding that our discussion applies equally to
independent claim 14.
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control circuit 208 is a hysteretic controller because it comprises hysteretic
comparators 430 and 432 inside 310 and hysteretic comparator 434 inside
312. Ans. 5 (citing Dearborn Figures 3, 4); see Dearborn claims 5, 6. The
Examiner further finds that Dearborn teaches providing a first input to
hysteretic comparator 434 that is configured to receive a sensed current from
an inductor as claimed. Final Act 4 (citing Dearborn Figures 3–5). The
Examiner determines that having a hysteretic controller and hysteretic
comparator, as claimed, is a mere arrangement of old elements with each
performing their known function, the combination yielding no more than one
would expect from such an arrangement. Final Act. 4. The Examiner
concludes that it would have been obvious to one having ordinary skill in the
art to replace Fahlenkamp’s controller and comparator with Dearborn’s
hysteretic controller and hysteretic comparator to enhance the power
efficiency of the power converter via better control of the power converter
by optimizing the response to disturbances in the power converter. Id.
Appellant argues that the combination of Dearborn’s pulse width
modulation (PWM) comparator 434,4 summer 440, and current sense signal
328 does not amount to the claimed hysteretic comparator because
Dearborn’s PWM comparator 434 is not a part of the hysteretic controller
310. Appeal Br. 6 (citing Dearborn ¶ 28). Instead, Appellant contends that
Dearborn’s PWM comparator 434 is a part of the PWM error generator 334,

4 Contrary to Appellant’s argument (Appeal Br. 6), Dearborn does disclose
that the comparator of the PWM error generator can be a hysteretic
comparator (Dearborn claim 6). Therefore, we interpret this argument as
Appellant explaining that hysteretic comparator 434 associated with the
PWM generator/controller does not amount to the recited hysteretic
comparator.
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which operates separately from the hysteretic controller 310. Appeal Br. 6.
Appellant further argues that Dearborn’s comparator 434 is not configured
to receive a sensed current from the inductor because the current sense
signal 328, as shown in Figure 5, is generated by sensing a current from an
unregulated supply voltage 540, which is interposed from an inductor 542 by
a series pass switch 544. Id. (citing Dearborn ¶ 30). Thus, Appellant asserts
that Dearborn does not specify that current sense signal 328 is generated by
sensing any current from an inductor and that current sense signal 328 is not
representative of a current conducted by inductor 542. Id. Appellant also
argues neither of hysteretic comparators 430 and 432 is configured to
receive current sense signal 328, and hysteretic controller 310 does not
include any other hysteretic comparator besides hysteretic comparators 430
and 432. Id.
We agree with Appellant that there is reversible error in the
Examiner’s determination of obviousness.
The Examiner bears the initial burden of presenting a prima facie case
of obviousness. In re Oetiker, 977 F.2d 1443, 1445 (Fed. Cir. 1992).
“[R]ejections on obviousness grounds cannot be sustained by mere
conclusory statements; instead, there must be some articulated reasoning
with some rational underpinning to support the legal conclusion of
obviousness.” In re Kahn, 441 F.3d 977, 988 (Fed. Cir. 2006), quoted with
approval in KSR Int’l Co. v. Teleflex Inc., 550 U.S. 398, 418 (2007).
The Examiner’s assertion that Dearborn’s component 208 is a
hysteretic controller (Ans. 5) is unsupported by evidence and adequate
explanation. First, Dearborn specifically recites the use of two distinct
control means, a hysteretic control in combination with a fixed frequency,
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pulse-width modulated (PWM) control, to improve the response to
disturbances in buck or buck derived SMPS system topologies. Dearborn
¶ 3. This disclosure of two types of controllers is consistent with
Appellant’s Specification disclosure that there exists two types of
controllers, the PWM type and the hysteretic type. Spec. ¶¶ 8–9. Second,
Dearborn describes that it is control circuit 208 that is optimized to respond
to a disturbance in power system 102. Dearborn ¶ 26. Third, Dearborn
describes component 208 as a control circuit that is distinct from the
hysteretic control circuit. Id. ¶¶ 4, 27. Although component 208 is a control
circuit that responds to a disturbance in a power system, the Examiner
directs us to no portion of Dearborn that describes control circuit 208 as a
hysteretic controller. Nor does the Examiner explain adequately why one
skilled in the art would have inferred that control circuit 208 is a hysteretic
controller, particularly when Dearborn discloses two different types of
controllers associated with control circuit 208.
With respect to hysteretic comparator 434, which forms part of the
PWM error generator (control), the Examiner contends that the first input of
this comparator is configured to receive a sensed current from an inductor.
Final Act. 4. In support of this contention, the Examiner points to
Dearborn’s Figure 5 showing a circuit with inductor 542. Ans. 4–5.
However, we agree with Appellant that Dearborn’s Figure 5 shows that
current sense signal 328 is generated by sensing a current from unregulated
supply voltage 540. Appeal Br. 6. The Examiner has not addressed this
argument adequately. See Ans. 5. Dearborn does disclose that power
converters employ a restricted set of components that include inductors,
capacitors, transformers, switches and resistors that are connected based on
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the desired power translation. Dearborn ¶ 23. However, the Examiner
points to no portion of Dearborn that teaches or suggests a first input
configured to receive a sensed current from an inductor where this first input
is included in a hysteretic comparator, much less an hysteretic comparator
that is part of a hysteretic controller. Nor does the Examiner explain why
one skilled in the art would have found the combination of this input with a
hysteretic controller and hysteretic comparator suitable for Fahlenkamp’s
apparatus and controller.
The Examiner has not provided an adequate technical explanation
with the requisite rational underpinning of why or how one skilled in the art
would have arrived at the claimed hysteretic controller and hysteretic
comparator including a first input configured to receive a sensed current
from the inductor. Thus, the Examiner has not made a prima facie case of
obviousness.
Accordingly, we reverse the Examiner’s prior art rejections of claims
1–20 under 35 U.S.C. § 103(a) for the reasons the Appellant presents and
those provided above.

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CONCLUSION
In summary:

Claims
Rejected
35
U.S.C. §
Reference(s)/Basis Affirmed Reversed
1–20 103(a) Fahlenkamp,
Dearborn
1–20

REVERSED