PTAB

IPR2020-00964

SolarEdge Technologies Ltd v. SMA Solar Technology AG

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Key Events
Petition

1. Case Identification

2. Patent Overview

  • Title: Power Generation System and Inverter for Feeding Power into a Three-Phase Grid
  • Brief Description: The ’630 patent discloses a power generation system, such as a photovoltaic system, with a specific relay arrangement for safely disconnecting the system from a three-phase electrical grid. The arrangement uses at least three two-pole relays to provide two serially connected, independently activated switches for each of the three grid conductors, fulfilling safety standards designed to prevent dangerous "islanding" conditions.

3. Grounds for Unpatentability

Ground 1: Obviousness over Kunimoto, Burke, and Finder - Claims 1-6 and 11-19 are obvious over Kunimoto in view of Burke and Finder.

  • Prior Art Relied Upon: Kunimoto (Japanese Patent Application Publication No. H11-69661), Burke (a 1994 textbook on power distribution engineering), and Finder (a 2006 technical datasheet for power relays).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Kunimoto taught the core invention: a photovoltaic power system with a relay arrangement using multiple two-pole relays to provide redundant, series-connected switches for disconnecting from a power supply. Specifically, Kunimoto’s third embodiment disclosed at least three two-pole relays where each of the three AC lines passes through switching contacts located on two different relays. To the extent Kunimoto did not explicitly describe a "three-phase grid," Burke taught that such power systems commonly connect to three-phase grids. Furthermore, to the extent Kunimoto did not explicitly disclose a "control coil" for each relay, Finder’s datasheet for a commercially available two-pole relay (DPST-NO) explicitly taught that such relays contain a control coil that operates its two switching contacts.
    • Motivation to Combine: A POSITA would combine Kunimoto with Burke to apply Kunimoto’s system to the common three-phase grids prevalent in the U.S. and other countries, a predictable and necessary adaptation for commercial use. A POSITA would have used an off-the-shelf, two-pole relay as described in Finder to implement Kunimoto’s relay arrangement, as it was a well-known, reliable, and cost-effective component for such applications.
    • Expectation of Success: The combination involved applying known components (Finder relays) to a known system (Kunimoto) for a known purpose (connection to a Burke-style grid), which would have yielded predictable results.

Ground 2: Obviousness over Kunimoto, Burke, Finder, and Nitsche - Claims 6-9 and 19-22 are obvious over Kunimoto in view of Burke, Finder, and further in view of Nitsche.

  • Prior Art Relied Upon: Kunimoto, Burke, Finder, and Nitsche (Application # 2008/0067877).
  • Core Argument for this Ground:
    • Prior Art Mapping: This ground built upon the base combination of Kunimoto, Burke, and Finder to address dependent claims reciting specific control features. Petitioner asserted that Nitsche taught the limitations of claims 6-9, including separately operating each relay with a "corresponding relay driver" (claim 6), operating the relay only upon receiving signals from both a "control unit" and a "watchdog arrangement" via AND gates (claim 7), having the watchdog monitor the control unit (claim 8), and monitoring each relay driver with a test signal (claim 9).
    • Motivation to Combine: A POSITA would add Nitsche's safety and control architecture to the base Kunimoto system to improve its robustness and reliability. The use of separate relay drivers, microcontrollers, and watchdog circuits was a well-known technique to avoid single points of failure in safety-critical systems like grid-tied inverters, which must reliably disconnect to prevent islanding.
    • Expectation of Success: A POSITA would have had a reasonable expectation of success in integrating Nitsche’s standard control and monitoring circuits with the relay system of Kunimoto, as both references dealt with driving and controlling electromagnetic relays.

Ground 3: Obviousness over Kunimoto, Burke, Finder, Nitsche, and Spreitzer - Claims 9, 10, 22, and 23 are obvious over Kunimoto in view of Burke, Finder, Nitsche, and further in view of Spreitzer.

  • Prior Art Relied Upon: Kunimoto, Burke, Finder, Nitsche, and Spreitzer (German Patent No. DE 100 29 828 C1).

  • Core Argument for this Ground:

    • Prior Art Mapping: This ground augmented the previous combination to address the specific relay testing method recited in claims 10 and 23. While Nitsche taught testing relays, Petitioner argued that Spreitzer explicitly taught the claimed method: using a test pulse (an electrical test pulse 11) to monitor the relays. Spreitzer taught that the test pulse's duration is intentionally selected to be insufficient to actually switch the relay, thereby allowing testing without disconnecting the system from the grid. The control unit then evaluates the response of the control coils to this test pulse.
    • Motivation to Combine: A POSITA would combine Spreitzer's non-disruptive testing technique with the safety system of Nitsche to further enhance the reliability of the Kunimoto power system. The ability to test relay coil integrity without interrupting power flow is a clear advantage. Spreitzer’s objective of providing a low-cost, low-complexity method for querying a relay's state directly motivated its application in a system where safety and uptime are important.
    • Expectation of Success: Applying Spreitzer’s known technique of using a short-duration pulse to test the similar electromagnetic relays in the Kunimoto/Nitsche system was a predictable application of a known testing method to improve a known device.

  • Additional Grounds: Petitioner asserted additional obviousness challenges, including grounds based on Kunimoto alone. Other grounds substituted Goto (Japanese Patent Publication No. 2000-23368) to teach a transformerless inverter for claim 5. The core unpatentability arguments for the independent claims relied on the same design modification theories presented above.

4. Key Claim Construction Positions

  • "photovoltaic inverter": For dependent claims 3 and 15, Petitioner argued this term should be construed as "an inverter that converts the DC output of a photovoltaic solar panel into an AC source for a power grid," consistent with the Applicant's position during prosecution.
  • "the relay arrangement is integrated into a housing": For dependent claims 12 and 16, Petitioner argued this phrase should be construed as "the relay arrangement is located inside a housing," clarifying that it does not require the components to be merged or fused.

5. Arguments Regarding Discretionary Denial

  • Petitioner argued that the grounds presented were not cumulative to those considered during prosecution. Although Kunimoto was cited in an Information Disclosure Statement (IDS), it was submitted after allowance, and the examiner was never provided with a translation and never applied the reference. The examiner’s rejections were based on a different combination of prior art that, unlike Kunimoto, did not teach the key three two-pole relay arrangement.

6. Relief Requested

  • Petitioner requested the institution of an inter partes review (IPR) and the cancellation of claims 1-23 of the ’630 patent as unpatentable.