PTAB

IPR2019-01223

SolarEdge Technologies Ltd v. SMA Solar Technology AG

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Petition
petition

1. Case Identification

2. Patent Overview

  • Title: Inverter with a Housing Having a Cooling Unit
  • Brief Description: The ’631 patent discloses a two-chambered housing for a power inverter. The design separates heat-sensitive electronic components, which are housed in a sealed first chamber, from less-sensitive electrical components (e.g., transformers, chokes) and a heat sink, which are housed in a second chamber open to ambient air for cooling.

3. Grounds for Unpatentability

Ground 1: Obviousness of Claims 1-5 and 7-18 over Shinohara, optionally in view of Brinkmann

  • Prior Art Relied Upon: Shinohara (Japanese Patent Publication No. 11234963), Brinkmann (German Patent Publication 29607354).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Shinohara discloses nearly all limitations of the independent claims. Shinohara teaches an inverter with a two-chambered housing separated by a partition wall. A "hermetically sealed" first chamber contains sensitive electronics (the inverter and control circuitry), while a second, open chamber contains a heat sink, a transformer, and cooling fans that draw in ambient air. This arrangement inherently provides a higher IP grade for the sealed chamber and places less-sensitive components in the directly cooled chamber. To the extent Shinohara does not explicitly teach a heat sink structure extending through the dividing wall, Brinkmann was argued to supply this element. Brinkmann teaches a sealed chamber for inverter electronics (IP grade 65) where a "cooling element projection" extends through the housing wall to thermally couple the internal electronics to external cooling fins.
    • Motivation to Combine: Petitioner contended that a person of ordinary skill in the art (POSITA) would combine Brinkmann’s heat sink design with Shinohara's housing to improve a similar device in a predictable way. Both references address the same problem of cooling sensitive electronics in a sealed chamber. A POSITA would have recognized the benefit of Brinkmann’s through-wall heat sink for direct thermal coupling and would have been motivated to apply this known technique to Shinohara to improve its cooling efficiency while maintaining environmental protection.
    • Expectation of Success: A POSITA would have had a high expectation of success, as the combination involved a simple mechanical modification—substituting one known heat sink configuration for another to achieve the predictable result of efficient cooling.

Ground 2: Obviousness of Claim 6 over Shinohara and Brinkmann, in view of Kramer

  • Prior Art Relied Upon: Shinohara, Brinkmann, and Kramer (European Patent Publication No. 1283589).
  • Core Argument for this Ground:
    • Prior Art Mapping: This ground specifically addressed claim 6, which requires "at least one of the choke and the transformer is located on a side of the wall in said second chamber." Petitioner argued that while Shinohara shows a transformer on the floor of the housing, Kramer explicitly teaches mounting a transformer on the dividing wall, adjacent to the heat sink and cooling fins.
    • Motivation to Combine: A POSITA would have been motivated to modify the Shinohara/Brinkmann combination by adopting Kramer’s wall-mounted transformer placement. Petitioner asserted this was a trivial design choice that improved cooling by positioning the transformer to be cooled by both direct airflow from the fan and conduction through the wall to the heat sink.
    • Expectation of Success: The modification was presented as a simple application of a known design technique (wall mounting) to achieve the predictable benefit of enhanced and more compact thermal management.

Ground 3: Obviousness of Claims 1-5, 7-8, 13, and 17-18 over Shinohara and Brinkmann, in view of Rodi

  • Prior Art Relied Upon: Shinohara, Brinkmann, and Rodi (European Patent Publication No. 0297308).
  • Core Argument for this Ground:
    • Prior Art Mapping: This ground addressed claim limitations requiring the presence of both a choke and a transformer. While Shinohara teaches a transformer, Rodi explicitly discloses placing components with high heat loss, such as "transformers, chokes, heat sinks or the like," in an air-cooled region of a power supply cabinet.
    • Motivation to Combine: Petitioner argued that a POSITA, knowing that inverters commonly use both chokes and transformers, would have been motivated by Rodi's teaching to place both components in the air-cooled second chamber of the Shinohara/Brinkmann design. This would be a logical step to efficiently cool all heat-generating, non-sensitive components.
    • Expectation of Success: Combining the teachings was argued to be a straightforward application of a known design principle—grouping less-sensitive, heat-producing components in an area with active cooling.
  • Additional Grounds: Petitioner asserted an additional obviousness challenge for claim 6 (Ground D), arguing that if the claims require both a choke and a transformer mounted on the wall, the combination of Shinohara, Brinkmann, Kramer, and Rodi would render the claim obvious.

4. Key Claim Construction Positions

  • "first chamber ... which has a higher IP grade rating for protection ... than the electrical components mounted in said second chamber": Petitioner argued this phrase should be construed to mean the first chamber protects against ingress of moisture and dust to a greater degree than the second chamber itself. This construction focuses on the relative protection of the two enclosures, not a comparison between the first chamber and the components in the second chamber.
  • "at least one of a choke and a transformer": Petitioner proposed this be construed disjunctively as "at least one choke or transformer." This construction, supported by the prosecution history, would mean prior art disclosing only one of the two components would meet the limitation.
  • "component of a high protection grade": Petitioner argued this should be construed as a component with a protection grade sufficient to be insensitive to contamination from exposure to ambient air, allowing it to function properly in the open second chamber.

5. Relief Requested

  • Petitioner requested institution of an inter partes review and cancellation of claims 1-18 of the ’631 patent as unpatentable.