Sunspec Alliance v. Tigo Energy, Inc.

NOTE: This disposition is nonprecedential.
United States Court of Appeals
for the Federal Circuit
______________________
SUNSPEC ALLIANCE,
Appellant
v.
TIGO ENERGY, INC.,
Appellee
______________________
2023-1741, 2023-1742
______________________
Appeals from the United States Patent and Trademark
Office, Patent Trial and Appeal Board in Nos. IPR2021-
01286, IPR2021-01287.
______________________
Decided: August 5, 2025
______________________
PHILIP WILLIAM MARSH, Arnold & Porter Kaye Scholer
LLP, Palo Alto, CA, argued for appellant. Also represented
by JOHN R. SABACINSKI, Chicago, IL; EVI LI, Merchant &
Gould, Alexandria, VA.
NICHOLAS A. BROWN, Greenberg Traurig LLP, San
Francisco, CA, argued for appellee. Also represented by
HEATH BRIGGS, Denver, CO; STEPHEN ULLMER, Portland,
OR.
______________________
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SUNSPEC ALLIANCE v. TIGO ENERGY, INC. 2
Before MOORE, Chief Judge, DYK and CUNNINGHAM,
Circuit Judges.
PER CURIAM.
SunSpec Alliance (SunSpec) appeals from two final
written decisions (FWD) of the Patent Trial and Appeal
Board (Board) holding SunSpec failed to show certain chal-
lenged claims of U.S. Patent Nos. 8,933,321 and 10,256,770
are unpatentable. For the following reasons, we affirm-in-
part, vacate-in-part, and remand-in-part.
BACKGROUND
Tigo Energy, Inc. (Tigo) owns the related ’321 and ’770
patents, which are directed to electrical safeguards in solar
arrays that shut down or reduce power to a solar module
when communication with the module is interrupted. ’321
patent at 1:46–2:30; ’770 patent at 2:40–61. SunSpec filed
petitions for inter partes review challenging claims 1, 5–7,
and 12–13 of the ’321 patent based on three unpatentabil-
ity grounds and claims 12–16 of the ’770 patent based on
four unpatentability grounds. J.A. 140–200; J.A. 1990–
2068. SunSpec argued Kronberg1, in combination with
other references, renders certain challenged claims obvious
under ground two for the ’321 patent and grounds two and
four for the ’770 patent. J.A. 7; J.A. 35. The Board held
SunSpec showed by a preponderance of the evidence claims
12–13 of the ’770 patent are unpatentable, but failed to
show the remaining challenged claims of the ’770 patent
and all challenged claims of the ’321 patent are unpatent-
able. J.A. 1–29; J.A. 30–83.
Except for claim 16 of the ’770 patent, the claims at is-
sue require a “predetermined number” of skips. For the
’321 patent, independent claim 1 is illustrative.
1 U.S. Patent No. 5,054,023. J.A. 900–12.
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SUNSPEC ALLIANCE v. TIGO ENERGY, INC. 3
1. A system comprising:
a watchdog unit coupled between a solar module
and a power bus, the power bus configured to con-
nect a plurality of solar modules to an inverter, the
watchdog unit having:
a local controller configured to monitor a com-
munication from a central controller remote
from the solar module and determine whether
the communication has been interrupted for a
time period longer than a predetermined num-
ber of allowed skips; and
at least one switch configured to disconnect the
solar module from the power bus in response to
a determination by the location controller that
the communication from the central controller
has been interrupted for a time period longer
than the predetermined number of allowed
skips;
wherein the watchdog unit is configured to connect
the solar module to the power bus when the com-
munication is not interrupted.
For the ’770 patent, claims 14 and 15, which depend from
claims 12 and 13, are illustrative.
12. A photovoltaic panel, comprising:
at least one photovoltaic cell;
a local unit configured on the photovoltaic panel,
the local unit having:
a voltage regulator coupled to the at least one
photovoltaic cell to receive electric power gen-
erated by the at least one photovoltaic cell; and
a controller coupled to the voltage regulator;
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SUNSPEC ALLIANCE v. TIGO ENERGY, INC. 4
wherein the voltage regulator provides a power
output of the photovoltaic panel using the electric
power generated by the at least one photovoltaic
cell;
wherein the controller communicates with a re-
mote unit, disposed at a location remote from the
local unit, to control operations of the voltage regu-
lator;
wherein the controller detects an anomaly in heart-
beat signals from the remote unit; and
wherein in response to the anomaly, the controller
causes the voltage regulator to reduce the power
output of the photovoltaic panel.
13. The photovoltaic panel of claim 12, wherein the
anomaly includes skips of heartbeat signals.
14. The photovoltaic panel of claim 13, wherein the
controller causes the voltage regulator to reduce
the power output of the photovoltaic panel when
the anomaly includes a predetermined number of
skips of the heartbeat signals.
15. The photovoltaic panel of claim 14, wherein
when skips of the heartbeat signals are less than
the predetermined number, the controller does not
cause the voltage regulator to reduce the power
output of the photovoltaic panel.
The Board held SunSpec’s prior art references failed to
disclose or teach a “predetermined number” of skips.
J.A. 9; J.A. 56, 67, 79, 81. SunSpec appeals. We have ju-
risdiction under 28 U.S.C. § 1295(a)(4)(A).
DISCUSSION
SunSpec argues the Board erred by (1) failing to ex-
pressly construe “predetermined number” of skips; (2) mis-
interpreting “predetermined number” of skips; and
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SUNSPEC ALLIANCE v. TIGO ENERGY, INC. 5
(3) failing to address SunSpec’s argument that Kronberg,
in combination with other references, teaches a “predeter-
mined number” of skips. SunSpec Br. 34–48, 50–60. We
review the Board’s claim construction de novo except for
subsidiary fact findings based on extrinsic evidence, which
we review for substantial evidence. Acceleration Bay, LLC
v. Activision Blizzard Inc., 908 F.3d 765, 769 (Fed. Cir.
2018). We review the Board’s ultimate obviousness conclu-
sion de novo and underlying fact findings for substantial
evidence. In re Sullivan, 498 F.3d 1345, 1350 (Fed. Cir.
2007).
I
SunSpec argues the Board erred by failing to expressly
construe “predetermined number” of skips because it was
an important limitation in the Board’s decisions, and the
parties disputed the term’s scope. SunSpec Br. 34–37. Be-
fore the Board, the parties disputed the meaning of “skips,”
which the Board construed in SunSpec’s favor, but neither
party raised a claim construction dispute regarding a “pre-
determined number” of skips. J.A. 8–11; J.A. 38–43. There
is therefore no error in the Board’s failure to formally in-
terpret this term. Homeland Housewares, LLC v. Whirl-
pool Corp., 865 F.3d 1372, 1375 (Fed. Cir. 2017) (holding
the Board must resolve “actual” disputes regarding claim
construction).
II
SunSpec argues the Board erred in interpreting “pre-
determined number” of skips. SunSpec Br. 37–48. An im-
plicit claim construction occurs, despite no express
construction, when the Board’s findings establish the scope
of a claim term. Google LLC v. EcoFactor, Inc., 92 F.4th
1049, 1056 (Fed. Cir. 2024).
A
In its FWD for the ’321 patent, the Board interpreted
“predetermined number” of skips as requiring at least one
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SUNSPEC ALLIANCE v. TIGO ENERGY, INC. 6
skip, excluding zero skips, and not being satisfied by
merely detecting an interruption. J.A. 15–16, 18, 20, 27.
SunSpec argues this was erroneous because the claim lan-
guage does not require “the time period to actually pass,
the skips to actually happen, or the device to actually count
the skips.” SunSpec Br. 39; see also id. at 38–45. We see
no error in the Board’s interpretation or application of “pre-
determined number” of skips.
The claim language requires “a local controller” that
can “determine whether the communication has been in-
terrupted for a time period longer than a predetermined
number of allowed skips.” ’321 patent at claim 1. Sun-
Spec’s interpretation makes the language after “inter-
rupted” superfluous. See Bicon, Inc. v. Straumann Co., 441
F.3d 945, 950 (Fed. Cir. 2006) (“[C]laims are interpreted
with an eye toward giving effect to all terms in the claim”).
Moreover, SunSpec’s interpretation is at odds with the
specification which teaches that the number of skips is
measured. ’321 patent at 8:21–27, Fig. 4. The prosecution
history also supports the Board’s construction. The pa-
tentee amended the claims changing “whether the commu-
nication is interrupted” to “whether the communication
has been interrupted for a time period longer than a prede-
termined number of allowed skips” to overcome prior art.
J.A. 332–36; J.A. 289. SunSpec’s interpretation would
read out the very amendment it made to overcome prior
art. The plain language of the claim, the specification, and
the prosecution history are all consistent with the Board’s
interpretation.
B
In its FWD for the ’770 patent, the Board concluded
that a “predetermined number of skips of the heartbeat sig-
nals” in claims 14 and 15 is different from “anomaly in
heartbeat signals” in claim 12 and “anomaly includes skips
of heartbeat signals” in claim 13. J.A. 56. SunSpec argues
this was erroneous as each should have the same meaning.
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SUNSPEC ALLIANCE v. TIGO ENERGY, INC. 7
SunSpec Br. 45–48. We see no error in the Board’s inter-
pretation, and to the extent the Board implicitly construed
“predetermined number of skips of the heartbeat signals,”
SunSpec fails to show the Board erred.
SunSpec’s interpretation conflicts with the intrinsic
record and violates the principle of claim differentiation.
Unlike independent claim 12 and dependent claim 13, de-
pendent claims 14 and 15 recite the additional limitation
that “the anomaly includes a predetermined number of
skips of the heartbeat signals.” ’770 patent at claims 12–
15 (emphasis added). SunSpec’s interpretation, that the
scope of claims 14 and 15 is the same as that of claims 12
and 13, would render “predetermined number of skips” su-
perfluous. Bicon, 441 F.3d at 950. SunSpec’s interpreta-
tion also violates the principle of claim differentiation by
equating dependent claims having additional limitations
with the claims from which they depend. Hill-Rom Servs.,
Inc. v. Stryker Corp., 755 F.3d 1367, 1377 (Fed. Cir. 2014)
(“Under principles of claim differentiation, we presume
that the claims without this limitation do not require it.”).
SunSpec’s interpretation is therefore inconsistent with the
plain language of the claims and unsupported by general
claim construction principles.
SunSpec argues the Board erred by interpreting “pre-
determined number” of skips in the ’770 patent as requir-
ing more than one skip because it contradicts the Board’s
prior interpretation in the FWD for the ’321 patent that at
least one skip is sufficient. SunSpec Br. 47 (citing J.A. 20).
We do not agree. The Board did not interpret this term as
requiring more than one skip. Rather, the Board held it
did not agree with SunSpec’s argument that a prior art ref-
erence disclosed a “predetermined number” of skips, where
SunSpec argued the reference “necessarily” requires a
threshold of at least one skip to be set. J.A. 57. The Board
explained the open-ended nature of the possible number of
skips did not meet the “predetermined number” require-
ment. Id. The Board therefore did not conclude one skip
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could never satisfy this requirement, and its interpretation
between patents was consistent. Id.
III
SunSpec argues the Board erred by failing to address
its argument that Kronberg, in combination with other ref-
erences, discloses a “predetermined number” of skips. Sun-
Spec Br. 50–60. Under its second unpatentability ground
for the ’321 patent, SunSpec argued certain challenged
claims are obvious based on the combination of Moine2 and
Kronberg. J.A. 146. In its FWD, the Board determined the
Moine-Kronberg combination did not render these claims
unpatentable because the combination did not teach a “pre-
determined number” of skips. J.A. 23. The Board found
SunSpec only relied on Moine to disclose this limitation,
and Moine does not disclose it. Id. Accordingly, the Board
never analyzed whether Kronberg, in combination with
Moine, teaches this limitation.
The Board’s finding that SunSpec only relied on Moine
is not supported by substantial evidence. The Board relied
on a single sentence from SunSpec’s Reply. J.A. 23 (citing
J.A. 1292). But SunSpec clearly argued that, to the extent
Moine does not disclose a “predetermined number” of skips,
Kronberg in combination with Moine does. Under the
heading “The Combined Teachings of Moine and Kronberg
Disclose the ‘Predetermined Number of Allowed Skips,’”
SunSpec stated:
Contrary to Patent Owner’s argument, Petitioner
does not rely on Kronberg to remedy any failure of
Moine to disclose the “skips” limitations. As ex-
plained above and as outlined in the Petition, Peti-
tioner believes that Moine discloses this limitation.
(See Section IV.B, supra.) But to the extent that a
2 French Patent Application Publication No.
2894401. J.A. 866–99.
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SUNSPEC ALLIANCE v. TIGO ENERGY, INC. 9
traditional watchdog of the type described in Kron-
berg is required, Petitioner with the support of its
expert’s testimony has shown that the combination
of Moine and Kronberg disclose and render this lim-
itation obvious.
J.A. 1292 (emphases added). This mirrors the language
from SunSpec’s petition. J.A. 173 (“Moine teaches this fea-
ture . . . . To the extent Patent Owner and/or the Board
disagrees that Moine alone does not suggest this limitation,
Moine in combination with Kronberg discloses or suggests
this feature.”). We therefore vacate and remand for the
Board to consider this argument in the first instance.
SunSpec also argues the Board made this same error
when addressing SunSpec’s second and fourth unpatenta-
bility grounds for the ’770 patent. SunSpec Br. 54–60. We
do not agree. Under both grounds, the Board specifically
addressed Kronberg and found Kronberg, in combination
with other references, does not teach a “predetermined
number” of skips. J.A. 67 (ground two); J.A. 81 (ground
four). Because the Board addressed SunSpec’s arguments
regarding Kronberg under these grounds, we see no error.
CONCLUSION
We have considered SunSpec’s remaining arguments
and find them unpersuasive. For the foregoing reasons, we
affirm the Board’s FWD for the ’321 patent as to grounds
one and three and the Board’s FWD for the ’770 patent as
to all grounds. We vacate the Board’s FWD for the ’321
patent as to ground two and remand for the Board to ad-
dress whether Kronberg, in combination with Moine,
teaches a “predetermined number” of skips.
AFFIRMED-IN-PART, VACATED-IN-PART, AND
REMANDED-IN-PART
COSTS
No costs.
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