PTAB

IPR2019-01227

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 an inverter. The design separates heat-generating electronic components based on their sensitivity to dust and moisture, with sensitive components placed in a sealed first chamber and less-sensitive components in a second chamber that is open to ambient air for cooling.

3. Grounds for Unpatentability

Ground 1: Obviousness of Claims 1, 3-5, 7, and 8 over Liu in view of Birger and/or Meinhardt

  • Prior Art Relied Upon: Liu (Chinese Utility Model Patent No. 99216549.0), Birger (European Patent Publication No. 0900621), and Meinhardt (a 2001 journal article).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Liu taught the core invention: a two-chamber inverter housing with a sealed chamber for sensitive electronics (e.g., inverter bridge) and a second, fan-cooled chamber open to ambient air for less-sensitive components (e.g., transformer, inductors). The chambers are separated by a wall that is part of the heat sink. To the extent Liu did not explicitly teach a heat exchange structure extending through the wall, Petitioner contended Birger supplied this limitation. Birger disclosed a power supply with a sealed circuit chamber and an open cooling chamber, where the heat sink extends through an aperture in the partition wall to cool the electronics. For dependent claim 5, requiring an IP65 rating, Petitioner argued this was a well-known standard, explicitly taught by Meinhardt for inverter housings.
    • Motivation to Combine (for §103 grounds): A POSITA would combine Birger’s heat sink design with Liu’s inverter housing to improve cooling efficiency while maintaining protection for sensitive electronics. This combination represented the use of a known technique (a pass-through heat sink) to improve a similar device (a partitioned inverter housing). The motivation included enhanced manufacturing flexibility (e.g., using a non-thermally conductive wall) and achieving the predictable result of effective cooling with environmental protection.
    • Expectation of Success (for §103 grounds): A POSITA would have a reasonable expectation of success as both Liu and Birger relate to cooling power-supply electronics using partitioned housings, making the integration a simple mechanical modification with predictable outcomes.

Ground 2: Obviousness of Claims 9-13 and 16-18 over Liu in view of Birger

  • Prior Art Relied Upon: Liu (Chinese Utility Model Patent No. 99216549.0) and Birger (European Patent Publication No. 0900621).

  • Core Argument for this Ground:

    • Prior Art Mapping: This ground challenged independent claim 9, which Petitioner argued was largely taught by Liu for the same reasons as claim 1. Liu disclosed the claimed inverter with a two-chamber housing, a cooling unit (fan) forcing air through the second chamber, and heat-generating components arranged in both chambers. The first chamber in Liu was described as a "sealed cavity," meeting the "dust and moisture tight" limitation. The combination with Birger was asserted for the limitation requiring the heat sink to extend from the first chamber through the wall into the second chamber, a feature Petitioner argued was explicitly shown in Birger.
    • Motivation to Combine (for §103 grounds): The motivation was identical to that in Ground 1: to apply Birger's advantageous heat sink design to Liu’s system. A POSITA would be motivated to protect electronics in a sealed chamber while cooling them effectively with an external heat sink, a benefit taught by Birger. This would allow the electronics to be placed directly on the heat sink, improving thermal transfer.
    • Expectation of Success (for §103 grounds): Success was expected because both references address the same technical problem, and applying Birger’s heat sink structure to Liu’s housing involved no technical hurdles and would predictably improve performance.

  • Additional Grounds: Petitioner asserted additional obviousness challenges, including combining Liu with Shinohara (Japanese Patent Application Publication No. 11234963) to teach vent slots (for claims 2 and 14) and a dedicated heat sink (for claim 15), and combining Liu with Kramer (European Patent Publication No. 1283589) to teach placing a transformer on the side of the separating wall (for claim 6).

4. Key Claim Construction Positions

  • "first chamber ... which has a higher IP grade rating for protection to humidity and dust than the electrical components mounted in said second chamber" (Claim 1): Petitioner argued this term should be construed to mean the first chamber has a higher protection rating than the second chamber itself, not higher than the components within the second chamber. This construction was based on the patent's specification, which repeatedly contrasted the protection levels of the two chambers to explain why different types of components were placed in each.
  • "at least one of a choke and a transformer" (Claim 1): Petitioner contended this phrase should be construed disjunctively as "at least one choke or transformer." The argument relied on the prosecution history, where an earlier version of the claim recited "at least one of a choke or one of a transformer," and the Patent Owner later distinguished prior art for lacking "a choke or transformer," indicating a disjunctive understanding.

5. Relief Requested

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