PTAB

IPR2022-00009

SolarEdge Technologies Ltd v. Koolbridge Solar Inc

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Petition
petition

1. Case Identification

2. Patent Overview

  • Title: Solar Energy Conversion and Utilization System
  • Brief Description: The 8,937,822 patent relates to systems for converting direct current (DC) power from a source, such as a solar panel, into alternating current (AC) power suitable for a utility grid. The disclosed technology focuses on various configurations of DC-to-AC inverters that use reversing switches, including single-phase H-bridge and three-phase half-bridge arrangements.

3. Grounds for Unpatentability

Ground 1: Anticipation and Obviousness over Schmidt - Claims 1-3 and 8-10 are anticipated by or obvious over Schmidt.

  • Prior Art Relied Upon: Schmidt (Patent 7,046,534).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Schmidt discloses every limitation of independent claims 1 and 8. Schmidt teaches a single-phase, transformerless DC/AC converter with an H-bridge switch that converts power from a floating solar generator (DC source) to a 50 or 60 Hz AC output connected to a grid. Petitioner asserted this structure is identical or equivalent to the claimed "DC to AC converter." Furthermore, Schmidt’s H-bridge topology inherently generates a common-mode voltage waveform on its DC inputs that has the same frequency as the AC output, thereby teaching the key functional limitation of claim 1 where the first and second repetition frequencies are equal (N=1).
    • Motivation to Combine (for §103 grounds): For the obviousness assertion, Petitioner argued that any minor structural differences between Schmidt’s converter and the structure described in the ’822 patent would have been trivial design choices for a person of ordinary skill in the art (POSITA).

Ground 2: Obviousness over Schmidt, Iwata, and Nishimura - Claims 5, 12, and 13 are obvious over Schmidt in view of Iwata and Nishimura.

  • Prior Art Relied Upon: Schmidt (Patent 7,046,534), Iwata (Application # 2008/0192519), and Nishimura (Application # 2009/0086520).
  • Core Argument for this Ground:
    • Prior Art Mapping: This ground asserted that the base single-phase H-bridge inverter is taught by Schmidt. The additional limitations of claim 5—a bidirectional DC-to-DC converter creating multiple floating voltage supplies with ratios of successive powers of three, multiple series-connected H-bridge switches, and a controller using a ternary number system—were taught by Iwata. Iwata discloses a multi-level inverter using this exact architecture to produce a smoother, stepped sine-wave output. Nishimura was cited for disclosing a specific bidirectional DC-to-DC converter structure with center-tapped windings that is structurally identical to an embodiment shown in the ’822 patent.
    • Motivation to Combine: A POSITA would combine Iwata's multi-level, series-connected inverter architecture with Schmidt's base inverter to achieve the known benefits taught by Iwata, such as improved efficiency, reduced power loss, and a better sine-wave approximation requiring less output filtering. A POSITA would have been further motivated to use the specific converter circuit from Nishimura in this combination as a simple substitution to improve efficiency and reduce component size, cost, and weight.
    • Expectation of Success: Petitioner argued success was predictable because the combination involved integrating known components (multi-level converters and specific DC-DC converter topologies) into a standard inverter circuit to achieve well-understood improvements in power conversion.

Ground 3: Obviousness over Schmidt, Koyama, and Ahmed - Claims 6 and 20 are obvious over Schmidt in view of Koyama and Ahmed.

  • Prior Art Relied Upon: Schmidt (Patent 7,046,534), Koyama (WO 2010/055713), and Ahmed (a 2007 IEEE article).

  • Core Argument for this Ground:

    • Prior Art Mapping: Schmidt again provided the foundational DC/AC inverter. Koyama was cited for teaching the addition of a common-mode filter between the DC power source and the inverter’s DC input terminals. The filter, comprising a choke coil and capacitors, serves the claimed function of preventing high-frequency components from being exported to the DC source. Ahmed was cited for teaching damping circuits, including an LC filter with a parallel resistor-inductor pair, to address the known problem of voltage overshoot and ringing in LC filters like the one taught by Koyama.
    • Motivation to Combine: A POSITA would be motivated to add Koyama's common-mode filter to Schmidt’s inverter to solve the well-known problem of common-mode noise and leakage current in transformerless inverters, thereby improving safety and electromagnetic compatibility. To further improve the performance of Koyama's filter, a POSITA would incorporate a damping circuit as taught by Ahmed to suppress resonance and minimize the voltage overshoot that the filter itself could cause, which is a standard design consideration.
    • Expectation of Success: The combination involved applying known filtering and damping techniques to a standard inverter circuit to solve known problems, which would have yielded predictable results for a POSITA.

  • Additional Grounds: Petitioner asserted additional obviousness challenges, including combining Schmidt with Suzui (Patent 6,927,955) for an AC ground leak detector (claims 4, 11); combining Schmidt with Becker (Patent 7,576,449) and Russell (’436 application) for a three-phase grid-interactive configuration (claim 7); and an alternative obviousness theory for claim 2 over Schmidt in view of Mohan (a power electronics textbook).

4. Key Claim Construction Positions

  • Petitioner argued that several claim terms, if not given their plain and ordinary meaning, should be construed as means-plus-function limitations under 35 U.S.C. § 112.
  • "bidirectional DC-to-DC converter" (Claims 5 and 13): Petitioner proposed this term recites the function of "converting the input voltage from said DC power source to a number of floating supplies of voltages equal to the input voltage divided or multiplied by successive powers of 3." The corresponding structure disclosed in the ’822 patent was identified as one or more transformers with center-tapped windings. Petitioner contended this construction was critical, as the Nishimura reference discloses an identical or equivalent structure for performing the same function.

5. Arguments Regarding Discretionary Denial

  • Petitioner noted that the prior art references relied upon in the petition were not cited or considered during the original prosecution of the ’822 patent.
  • The petition also stated that a related district court case, previously asserted by the Patent Owner, was voluntarily dismissed without prejudice after the Patent Owner was notified of Petitioner's intent to file IPRs, suggesting that factors related to co-pending litigation weigh against discretionary denial.

6. Relief Requested

  • Petitioner requests institution of an inter partes review and cancellation of claims 1-13 and 20 of Patent 8,937,822 as unpatentable.