SolarEdge Technologies Ltd v. SMA Solar Technology AG

1. Case Identification

• Case #: IPR2019-01226
• Patent #: 7,816,631
• Filed: July 9, 2019
• Petitioner(s): SolarEdge Technologies Ltd.
• Patent Owner(s): SMA Solar Technology, AG.
• Challenged Claims: 1-18

2. Patent Overview

• Title: Inverter with a Housing Having a Cooling Unit
• Brief Description: The ’631 patent describes a cooling system for an inverter that uses a two-chambered housing. One chamber is sealed to protect sensitive electronic components from dust and moisture, while a second, separate chamber is open to ambient air to cool less-sensitive components (e.g., transformers, chokes) and a heat sink via a fan.

3. Grounds for Unpatentability

Ground 1: Claims 1-18 are obvious over Katooka in view of Brinkmann.

• Prior Art Relied Upon: Katooka (Patent 5,831,240) and Brinkmann (German Patent Publication 29607354).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner asserted that Katooka discloses nearly all elements of the challenged claims. Katooka teaches an inverter with a two-chamber housing separated by a wall (chassis 300). A first, closed chamber (region 606) houses sensitive power semiconductor modules, while a second, open chamber (region 608) contains a cooling fan, a transformer, and a choke (smoothing reactor). The fan cools the components in the second chamber and a heat sink thermally coupled to the sensitive electronics in the first chamber. Petitioner argued the only element arguably not explicitly disclosed by Katooka is a heat sink that physically "extends through" the wall separating the chambers. Brinkmann was introduced to supply this teaching, as it discloses an inverter with a sealed chamber where a heat sink includes a projection that extends through the chamber wall to cool the internal electronics.
  • Motivation to Combine: A person of ordinary skill in the art (POSITA) would have been motivated to combine the teachings of Brinkmann with the inverter design of Katooka. The combination represents the application of a known technique (Brinkmann's through-wall heat sink) to a similar device (Katooka's two-chamber inverter) to achieve a predictable improvement. Specifically, using a through-wall heat sink would improve the seal between the chambers, thereby better protecting the sensitive electronics in the first chamber from contaminants, which is a stated goal of both the ’631 patent and the prior art.
  • Expectation of Success: A POSITA would have had a reasonable expectation of success. The combination is a simple mechanical modification, substituting one known method of heat sink coupling for another to achieve the predictable result of efficient cooling while maintaining environmental isolation.

Ground 2: Claims 1-8, 13, and 17-18 are obvious over Katooka and Brinkmann in view of Rodi.

• Prior Art Relied Upon: Katooka (Patent 5,831,240), Brinkmann (German Patent Publication 29607354), and Rodi (European Patent Publication No. 0297308).
• Core Argument for this Ground:
  • Prior Art Mapping: This ground reinforces Ground 1 and specifically addresses claim limitations requiring multiple less-sensitive components (e.g., a transformer, a choke, and a cast winding) in the second, air-cooled chamber. While Petitioner argued Katooka teaches this, Rodi was presented as an additional reference explicitly disclosing this design choice. Rodi teaches a power supply with a two-chambered housing where components with high heat loss that are less sensitive to environmental influences, such as "transformers, chokes, heat sinks or the like," are deliberately placed together in a region cooled by outside air.
  • Motivation to Combine: A POSITA implementing the design of Katooka/Brinkmann would be motivated by Rodi's teachings to place multiple less-sensitive components, such as transformers and chokes, together in the air-cooled second chamber. This arrangement is a logical and efficient design choice for cooling such components, which are known to be relatively insensitive to the dust and moisture present in an ambient airflow. The combination is an example of using a known technique (placing less-sensitive components in an air-cooled chamber) to improve a similar device.
  • Expectation of Success: A POSITA would have expected success in applying Rodi’s teachings, as it involves the conventional arrangement of standard, well-understood inverter components to achieve efficient cooling.

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 term should be construed to mean the first chamber protects against dust and moisture to a greater degree than the second chamber itself, not the components within the second chamber. This construction is allegedly supported by the specification, which consistently contrasts the protection levels of the two chambers.
• "at least one of a choke and a transformer": Petitioner contended this phrase should be construed disjunctively as "at least one choke or transformer." This position was based on the prosecution history, where an amendment changed the language from "a choke or one of a transformer," and the Patent Owner subsequently argued against prior art for not teaching a "choke or transformer," indicating a disjunctive understanding.
• "Component of a high protection grade": Petitioner proposed this term means a component with a protection grade sufficient to be insensitive to contamination from exposure to ambient air. The specification links this term to components, like transformers, that can be placed directly in the cooling air stream without performance degradation.

5. Arguments Regarding Discretionary Denial

• Petitioner argued that discretionary denial under §325(d) would be inappropriate because this petition is one of five concurrently filed petitions that are not redundant. The petitions were asserted to be materially different because they rely on different primary and secondary prior art references not considered by the Examiner during prosecution (e.g., Katooka, Brinkmann, Rodi). Furthermore, Petitioner contended that the different prior art combinations teach the claim limitations in distinct ways, constituting different approaches to the invalidity challenge.

6. Relief Requested

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