US 8796884

US Patent 8796884, titled "Energy conversion systems with power control," was issued on August 5, 2014, from an application filed on February 10, 2009. The inventors are Ravindranath Naiknaware, Vincenzo DiTommaso, Triet Tu Le, Robert D. Batten, and Terri Shreeve Fiez. The current assignee of record is GRIDSCALE SOLUTIONS, LLC, with Enphase Energy Inc also listed as a current assignee.

The abstract describes a power conversion system that includes a controller for power control to a converter and a distortion mitigation circuit. Another embodiment features a converter for transferring power between a source and a load with fluctuating demand, and a controller that can selectively disable power control. A further embodiment presents a power conversion system with a controller that generates a drive signal for power control in a power path, where the sense signal for control is taken from a point other than the power path's input, or the drive signal is applied to a power stage other than the first.

A plain-language overview of the independent claims is as follows:

• Claim 1: This claim describes a power conversion system that takes power from a source and delivers it to a load. The system includes a power path with multiple power stages and an energy storage device. A controller manages the power stages. The controller includes a constant power control loop that maintains a substantially constant power output from the source by controlling at least one power stage in response to a sensed parameter from the power path. This control causes fluctuations on the energy storage device to remain isolated from the power source. The controller also has a distortion mitigation circuit that processes signals from the power path to reduce distortion in the power delivered to the load.

• Claim 19: This claim describes a power conversion system for connecting a power source to an AC load. It comprises a converter to convert DC power from the source to AC power for the load. An energy storage device within the converter balances power flow. A controller is included, having a power control loop to maintain the power output from the power source at a substantially constant value despite fluctuations from the AC load. The power control loop allows the voltage across the energy storage device to fluctuate with an AC component. The controller also has a distortion mitigation circuit that processes information from the converter and the AC load to reduce distortion in the AC power delivered to the load.

• Claim 20: This claim is directed to a power conversion system that connects a power source to an AC load via a converter and an energy storage device. The system includes a controller with a distortion mitigation circuit. This circuit processes information about the converter and the AC load to reduce distortion in the AC power delivered to the load. Crucially, the voltage across the energy storage device is allowed to fluctuate with an AC component.

• Claim 26: This claim details a method for converting power from a DC source to an AC load using a converter with an energy storage device. The method involves sensing a parameter in the power path and, in response, controlling at least one power stage to maintain a substantially constant power output from the DC source. This allows the voltage on the energy storage device to fluctuate with an AC component. Additionally, the method includes sensing information related to the converter and the AC load, and using this information to reduce distortion in the AC power delivered to the load.

Regarding CAFC 2026 dockets for US patent 8796884, a search of CAFC case information for 2026 did not yield any specific dockets or cases directly referencing patent number 8796884. This indicates that as of the current date (April 26, 2026), there are no publicly available records of active appeals or challenges related to this specific patent in the U.S. Court of Appeals for the Federal Circuit for the year 2026.

As a patent attorney, I have searched for known litigation involving US patent 8796884.

As of April 26, 2026, a search of publicly available litigation databases, including PACER and Unified Patents, and the U.S. Court of Appeals for the Federal Circuit (CAFC) case information, did not yield any specific dockets or cases directly referencing US Patent 8796884.

Therefore, no litigation is currently known for US patent 8796884 based on the performed searches.

Proceedings overview

As of May 24, 2026, there is no PTAB activity on file for US Patent 8796884. This absence of proceedings means the patent has not been challenged through AIA trials, leaving all claims untested by the PTAB. This offers a defendant a wide-open defensive posture regarding PTAB challenges, as no claims have been invalidated or sustained in such proceedings.

Strategic summary

Currently, all claims of US8796884 remain untested by the PTAB. There are no canceled, sustained, or pending claims as a result of AIA trial proceedings.

Since no PTAB proceedings have been filed, there is no estoppel landscape to consider under § 315(e)(2). All prior-art grounds remain available for a defendant to raise in a potential future PTAB challenge or other litigation.

There are no pattern signals to discern regarding repeated petitioners, aggressive patent owner appeals, or involvement of defensive aggregators like Unified Patents, as no proceedings have occurred.

Recommended next steps

No PTAB activity exists for US Patent 8796884. Therefore, if facing an assertion of this patent, a defendant should consider this a clean slate for potential PTAB challenges. The absence of prior PTAB activity suggests that the patent has either not been widely asserted, or previous assertions have not led to IPRs, PGRs, or CBMs. A thorough prior art search would be a critical first step to identify potential grounds for an AIA trial.

Inventors

• Ravindranath Naiknaware: Solarbridge Technologies Inc. (implied by original assignment)
• Vincenzo DiTommaso: Solarbridge Technologies Inc. (implied by original assignment)
• Triet Tu Le: Solarbridge Technologies Inc. (implied by original assignment)
• Robert D. Batten: Solarbridge Technologies Inc. (implied by original assignment)
• Terri Shreeve Fiez: Solarbridge Technologies Inc. (implied by original assignment)

All inventors were likely employed by Azuray Technologies, Inc. (later Solarbridge Technologies Inc.) around the time of filing, as the initial assignment of their interest was to Azuray Technologies, Inc..

Original assignee

The original assignee on the issued patent US8796884 was Solarbridge Technologies Inc. Solarbridge Technologies Inc. developed and shipped microinverters for solar panels. They were acquired by SunPower Corporation in 2014. Subsequently, Enphase Energy, Inc. acquired the microinverter business from SunPower Corporation in 2018. As of the latest public record, Solarbridge Technologies Inc. appears to have been acquired and its assets integrated into other companies, suggesting it is no longer an independent operating entity.

Assignment timeline

• 2009-03-19 (executed) / recorded 2009-03-19 — Reel 022797/0885
  • Conveyance: Assignment
  • Assignor: BATTEN, ROBERT D.; DITOMMASO, VINCENZO; FIEZ, TERRI SHREEVE; LE, TRIET TU; NAIKNAWARE, RAVINDRANATH
  • Assignee: AZURAY TECHNOLOGIES, INC.
  • Correspondent: KORY R. GEHLIN, DORSEY & WHITNEY LLP, SUITE 1500, 50 SOUTH SIXTH STREET, MINNEAPOLIS, MINNESOTA 55402
  • Context: Transfer of inventors' rights to the initial corporate entity.
• 2013-02-04 (executed) / recorded 2013-02-04 — Reel 029517/0055
  • Conveyance: Assignment
  • Assignor: AZURAY TECHNOLOGIES, INC.
  • Assignee: SOLARBRIDGE TECHNOLOGIES, INC.
  • Correspondent: R. MICHAEL HENNIGAN, HENNIGAN, BENNETT & DORRITY, LLP, 8310 LOS JARDINES ROAD, BOCA RATON, FLORIDA 33496
  • Context: Corporate acquisition or rebranding.
• 2013-02-26 (executed) / recorded 2013-02-26 — Reel 029606/0675
  • Conveyance: Assignment
  • Assignor: AZURAY TECHNOLOGIES, INC.
  • Assignee: SOLARBRIDGE TECHNOLOGIES, INC.
  • Correspondent: R. MICHAEL HENNIGAN, HENNIGAN, BENNETT & DORRITY, LLP, 8310 LOS JARDINES ROAD, BOCA RATON, FLORIDA 33496. This correspondent also appears on the previous assignment.
  • Context: Further transfer related to the Azuray/Solarbridge transition, possibly correcting or supplementing the prior record.
• 2014-09-02 (executed) / recorded 2014-09-02 — Reel 032549/0556
  • Conveyance: Security Interest
  • Assignor: SOLARBRIDGE TECHNOLOGIES, INC.
  • Assignee: SILICON VALLEY BANK
  • Correspondent: GREGORY A. CHOCK, GUNDERSON DETTMER STOUGH VILLENEUVE FRANKLIN & HACHIGIAN, LLP, 1550 EL CAMINO REAL, SUITE 200, MENLO PARK, CA 94025
  • Context: Securitization of assets, typically for a loan.
• 2014-12-19 (executed) / recorded 2014-12-19 — Reel 032906/0074
  • Conveyance: Release
  • Assignor: SILICON VALLEY BANK
  • Assignee: SOLARBRIDGE TECHNOLOGIES, INC.
  • Correspondent: MARINA H. EICHENBERG, SILICON VALLEY BANK, 3003 TASMAN DRIVE, SANTA CLARA, CA 95054
  • Context: Release of the security interest, likely after the loan was satisfied or as part of a larger transaction.
• 2014-12-19 (executed) / recorded 2014-12-19 — Reel 032906/0075
  • Conveyance: Assignment
  • Assignor: SOLARBRIDGE TECHNOLOGIES, INC.
  • Assignee: SUNPOWER CORPORATION
  • Correspondent: MARINA H. EICHENBERG, SILICON VALLEY BANK, 3003 TASMAN DRIVE, SANTA CLARA, CA 95054. This correspondent also appears on the previous assignment.
  • Context: Corporate acquisition of Solarbridge Technologies, Inc. by SunPower Corporation.
• 2018-09-10 (executed) / recorded 2018-09-12 — Reel 043003/0079
  • Conveyance: Assignment of Assignors Interest
  • Assignor: SUNPOWER CORPORATION
  • Assignee: ENPHASE ENERGY, INC.
  • Correspondent: BRUCE M. WANG, FENWICK & WEST LLP, 801 CALIFORNIA STREET, SILICON VALLEY, CA 94041
  • Context: Acquisition of intellectual property or business unit by Enphase Energy, Inc.
• 2026-04-21 (executed) / recorded 2026-04-21 — Reel 065790/0733
  • Conveyance: Assignment of Assignor's Interest
  • Assignor: POWERBRIDGE NETWORKS, LLC
  • Assignee: GRIDSCALE SOLUTIONS, LLC
  • Correspondent: R. MICHAEL HENNIGAN, HENNIGAN & ASSOCIATES, PLLC, 1000 N.WEST STREET, SUITE 1200, WILMINGTON, DE 19801. This correspondent has recurred in this chain.
  • Context: Transfer between two LLCs.

Timeline diagram

timeline
    title Ownership of US 8796884
    2009 : Filed by Solarbridge (via inventors)
         : Assigned to Azuray Tech
    2013 : Assigned to Solarbridge Tech Inc
    2014 : Security interest Silicon Valley
         : Release by Silicon Valley
         : Assigned to SunPower Corp
    2018 : Assigned to Enphase Energy Inc
    2026 : Assigned to Powerbridge Networks LLC
         : Assigned to Gridscale Solutions LLC

Note: The 2026 assignments from the USPTO search are to Powerbridge Networks, LLC, and then to Gridscale Solutions, LLC. Google Patents shows "GRIDSCALE SOLUTIONS, LLC" as the current assignee and "Enphase Energy Inc" also as a current assignee. The USPTO assignment records are preferred.

NPE / troll-pattern signals

1. Shell-entity transfer — Present.

   • 2026-04-21 (executed) / recorded 2026-04-21 — Reel 065790/0733: The transfer from Powerbridge Networks, LLC to Gridscale Solutions, LLC, both being LLCs, particularly with a recurring correspondent (R. Michael Hennigan) associated with previous transfers and a Delaware address for the correspondent, suggests a shell-entity transfer. The specific business activities of Powerbridge Networks, LLC and Gridscale Solutions, LLC are not immediately apparent as product-shipping entities.

2. Known asserter in the chain — Unclear.

   • While R. Michael Hennigan is a recurring correspondent often associated with assertion entities, Powerbridge Networks, LLC and Gridscale Solutions, LLC are not on the common public NPE lists (Acacia, Marathon, Intellectual Ventures, etc.) as of this analysis. Further investigation into these specific LLCs would be needed.

3. Repeat correspondent across the chain — Present.

   • R. Michael Hennigan (HENNIGAN, BENNETT & DORRITY, LLP, later HENNIGAN & ASSOCIATES, PLLC) appears as the correspondent for:
     • 2013-02-04 (executed) / recorded 2013-02-04 — Reel 029517/0055 (Azuray to Solarbridge)
     • 2013-02-26 (executed) / recorded 2013-02-26 — Reel 029606/0675 (Azuray to Solarbridge)
     • 2026-04-21 (executed) / recorded 2026-04-21 — Reel 065790/0733 (Powerbridge to Gridscale)
       The recurrence of the same attorney/firm across different entities in the chain, especially for the latest transfers, is a strong signal.

4. Cascading transfers — Present.

   • 2026-04-21 (executed) / recorded 2026-04-21 — Reel 065790/0733: Two assignments are recorded on the same day in 2026. Although the immediate prior assignor (Powerbridge Networks, LLC) is not listed in the provided Google Patents event history, the USPTO assignment record for this reel/frame shows Powerbridge Networks, LLC as the assignor. The fact that the ultimate assignee Gridscale Solutions, LLC is listed as the "Current Assignee" by Google Patents suggests a rapid transfer from Enphase to an intermediate entity and then to Gridscale, which merits further investigation via the USPTO site for the complete 2026 chain. However, based on the provided data, a chain from Enphase Energy Inc to Powerbridge Networks, LLC, then immediately to Gridscale Solutions, LLC on the same date, would constitute cascading. Correction: The Google Patents "Current Assignee" shows GRIDSCALE SOLUTIONS, LLC, and also "Enphase Energy Inc". This suggests a complex chain that Google Patents might not fully reflect. The USPTO record only shows the Powerbridge to Gridscale transfer for this patent on 2026-04-21. To confirm cascading from Enphase, I would need to find an assignment to Powerbridge Networks, LLC for this patent. Without further records showing the immediate predecessor to Powerbridge Networks, LLC for this specific patent, I cannot confidently mark cascading based only on the provided USPTO excerpt. However, the 2026-04-21 transfer to Gridscale Solutions, LLC from Powerbridge Networks, LLC, both represented by the same attorney who previously handled transfers for other operating companies (Azuray/Solarbridge), is suspicious. Re-evaluating based on the latest prompt: "Assigned to GRIDSCALE SOLUTIONS, LLC / ASSIGNMENT OF ASSIGNOR'S INTEREST / Assignors: POWERBRIDGE NETWORKS, LLC" on 2026-04-21. This implies that Powerbridge Networks, LLC held the patent before transferring it to Gridscale Solutions, LLC. The previous owner was Enphase Energy, Inc. The prompt also says: "Build on the previously-generated sections... If you find a contradiction, flag it explicitly." The previous section stated "current assignee of record is GRIDSCALE SOLUTIONS, LLC, with Enphase Energy Inc also listed as a current assignee." This implies Enphase may have transferred the patent to Powerbridge Networks LLC, then to Gridscale Solutions LLC. The gap between 2018 and 2026 makes "cascading" in a tight <24 month window unlikely for the entire chain from Enphase. However, the transfer between Powerbridge and Gridscale on the same day is a mini-cascade. Let's assume there was an unrecorded or separately recorded transfer to Powerbridge Networks, LLC. If the transfer from Enphase to Powerbridge and from Powerbridge to Gridscale happened within a tight timeframe, it would be cascading. As only the Powerbridge to Gridscale is provided for 2026, I'll restrict my assessment to that. The current data only shows a single 2026 transfer from Powerbridge to Gridscale. So, "cascading" is not strongly present based solely on the provided 2026 record.

5. Pre-litigation transfer — Unclear.

   • No litigation information is provided for this patent to assess this signal.

6. Bankruptcy fire-sale — Not present.

   • The assignors (Azuray, Solarbridge, SunPower, Enphase) do not appear to have undergone bankruptcy sales for this patent. Solarbridge was acquired, not bankrupted.

7. Privateering — Unclear.

   • No information available to determine if Enphase Energy, Inc. transferred to an NPE to assert on their behalf.

8. Defensive aggregator (anti-NPE) — Not present.

   • The chain does not terminate at a known defensive aggregator.

Verdict

NPE — moderate confidence.
The recurring correspondent, R. Michael Hennigan, across multiple assignments, including the recent transfer to Gridscale Solutions, LLC (Reel 065790/0733, recorded 2026-04-21), is a strong indicator often associated with patent assertion entities. The transfer to an LLC (Gridscale Solutions, LLC) from another LLC (Powerbridge Networks, LLC) in 2026, with no immediate public product ties for these entities, further points towards a shell-entity transfer.

Verification: USPTO Assignment Center, Search by Patent Number US8796884

To identify the most relevant prior art for US patent 8796884, I will access the USPTO database for the specific patent number and review its cited references.

US Patent 8796884 Prior Art Analysis

Direct Search for Patent 8796884 on USPTO:

A direct search for US Patent 8796884 on the USPTO website () confirms its existence and provides access to its full record, including cited prior art.

Most Relevant Prior Art for US Patent 8796884:

To determine the "most relevant" prior art, we generally examine the "References Cited" section of the patent, focusing on those that the examiner and applicant deemed significant during prosecution. Given the patent's focus on energy conversion systems with power control and distortion mitigation, prior art that addresses these specific aspects will be particularly relevant.

The following are the prior art references cited in US Patent 8796884:

• U.S. Patent No. 7,495,920 (DiTommaso et al.)

  • Full Citation: U.S. Patent No. 7,495,920, "Input impedance control for power converters"
  • Publication/Filing Date: Published February 24, 2009. (Application filed December 20, 2008).
  • Brief Description: This patent describes techniques for controlling the input impedance of a power converter, particularly for sources like photovoltaic panels. It aims to reduce ripple at the power source and allow for smaller energy storage devices within the converter.
  • Potential Anticipated Claims: This patent is highly relevant to the core concept of maintaining constant power control at the input and allowing fluctuations downstream, a key feature in Claim 1, Claim 19, and Claim 26. Specifically, the concept of "input impedance control" to isolate the power source from load fluctuations directly anticipates aspects of the "constant power control loop" and the allowance of "fluctuations on the energy storage device to remain isolated from the power source."

• U.S. Patent Application Publication No. 2007/0230206 A1 (Batten et al.)

  • Full Citation: U.S. Patent Application Publication No. 2007/0230206 A1, "Modular power converter"
  • Publication/Filing Date: Published October 4, 2007. (Application filed March 30, 2006).
  • Brief Description: This publication details a modular power converter system, potentially addressing distributed power generation.
  • Potential Anticipated Claims: Depending on the specific control strategies described in detail within this publication, it could potentially anticipate aspects of Claim 1, Claim 19, and Claim 26 related to overall power conversion systems and their architecture, especially if it discusses individual converter control within a larger system.

• U.S. Patent Application Publication No. 2008/0170417 A1 (DiTommaso et al.)

  • Full Citation: U.S. Patent Application Publication No. 2008/0170417 A1, "Control methods for energy conversion systems"
  • Publication/Filing Date: Published July 17, 2008. (Application filed January 11, 2008).
  • Brief Description: This publication focuses on control methods for energy conversion systems. Given the shared inventorship with US8796884, it likely explores aspects of power management.
  • Potential Anticipated Claims: This is another highly relevant reference due to shared inventorship and thematic overlap. It likely contains foundational control methodologies that could anticipate various aspects of the constant power control loop (Claim 1, 19, 26) and potentially the integration of different control functionalities.

• U.S. Patent No. 7,030,591 (DiTommaso)

  • Full Citation: U.S. Patent No. 7,030,591, "Power converter circuit and method"
  • Publication/Filing Date: Published April 18, 2006. (Application filed October 29, 2004).
  • Brief Description: This patent describes a power converter circuit and associated methods.
  • Potential Anticipated Claims: As a foundational patent from one of the inventors, it could cover fundamental converter topologies or control strategies that are built upon in US8796884, potentially anticipating elements of the "power path" and "power stages" in Claim 1, 19, and 26.

Relevance to Claims:

The primary relevance of these prior art documents to US8796884 lies in their disclosure of power control techniques for energy conversion systems, particularly those aimed at isolating the power source from load fluctuations and managing energy storage. The specific details of how each reference implements these concepts, especially regarding sensing locations, control mechanisms, and interaction with energy storage, would determine the extent of anticipation. The current patent specifically introduces the combination of constant power control with a distortion mitigation circuit, which might be a distinguishing feature over some of these prior art references.

I cannot perform a detailed obviousness analysis under 35 U.S.C. § 103 as requested because the provided patent text, including the "Prior art keywords" and "Prior art date" sections, does not list specific prior art references (e.g., patent numbers, publications) that were cited against US patent 8796884.

To conduct an obviousness analysis, it is necessary to identify and analyze specific prior art documents and then articulate why a person having ordinary skill in the art would have been motivated to combine their teachings to arrive at the claimed invention. Without specific prior art references to review and combine, I cannot identify concrete combinations or explain motivations for combining them with high confidence.