PTAB

IPR2023-00879

SMA Solar Technology America LLC v. Tigo Energy Inc

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1. Case Identification

2. Patent Overview

  • Title: Systems and Methods for Enhanced Efficiency Auxiliary Power Supply Module
  • Brief Description: The ’021 patent describes a power supply for a solar system that uses a two-stage architecture. The system includes a control circuit to manage the transition between a deactivated state (at low input power) and an enabled state, preventing false starts and ensuring stable power delivery to a microcontroller.

3. Grounds for Unpatentability

Ground 1: Anticipation of Claims 1-7 and 9 - Claims 1-7 and 9 are anticipated by Mieth.

  • Prior Art Relied Upon: Mieth (DE 3725476).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Mieth discloses every limitation of independent claim 1. Mieth describes a two-state circuit for a solar generator that supplies power to a load. Petitioner asserted Mieth's capacitor (2) and associated components function as the claimed "first stage," while its auxiliary power supply (19) functions as the "second stage" powering a load (20), which a POSITA would understand could be a microcontroller. Mieth’s circuit operates in a first state where a preliminary load (11) is switched on to consume power from the first output while the second stage is disabled. When the voltage from the first output exceeds a threshold, determined by a comparator (9), the circuit enters a second state where the preliminary load is disconnected and the second stage is enabled.
    • Key Aspects: Petitioner contended that Mieth's cascaded comparator arrangement (9 and 13) inherently creates a "break before make" condition, teaching the claimed limitation of disconnecting the load prior to enabling the second stage (claim 9).

Ground 2: Obviousness of Claims 1, 8, 10-12, 15-18, and 20 - Claims are obvious over Mieth in view of Balogh.

  • Prior Art Relied Upon: Mieth (DE 3725476) and Balogh (Patent 6,246,592).
  • Core Argument for this Ground:
    • Prior Art Mapping: While Mieth teaches the core control logic, Balogh was cited to teach the specific power converter architecture claimed. Balogh discloses cascaded power converter arrangements, including first and second buck converters (step-down converters), which are well-known for applications requiring large input-to-output voltage conversion ratios, such as solar power systems. Petitioner argued it would have been obvious to replace Mieth’s simpler first stage (a capacitor) and second stage (a generic power supply) with the more robust and well-known cascaded step-down converters taught by Balogh to better handle the high and variable voltages typical of solar panels. This combination, Petitioner asserted, explicitly meets the limitations of claim 8 (first and second step-down converters) and provides a more detailed teaching of the "first stage power converter" and "second stage power converter" of independent claims 10 and 18.
    • Motivation to Combine: A POSITA would combine the references to improve the performance and robustness of Mieth's startup circuit. Mieth addresses the problem of varying input voltage, while Balogh provides an effective architecture (cascaded converters) for handling the high DC voltages common in solar applications. The combination would adapt Mieth's reliable startup control to a more efficient, high-voltage power conversion system.
    • Expectation of Success: The combination involved applying a known power conversion architecture (Balogh) to a known control circuit (Mieth) to achieve the predictable result of a reliable, high-efficiency power supply for a solar application.

Ground 3: Obviousness of Claims 13 and 14 - Claims are obvious over Mieth and Balogh, and further in view of Nishi.

  • Prior Art Relied Upon: Mieth (DE 3725476), Balogh (Patent 6,246,592), and Nishi (Application # 2005/0105224).

  • Core Argument for this Ground:

    • Prior Art Mapping: This ground builds on the Mieth/Balogh combination to address claim 13, which requires the microcontroller to be "configured to maximize power generated by the power source." Nishi was cited for its disclosure of a microcomputer in a photovoltaic system that controls inverter circuitry to perform maximum power point tracking (MPPT), a standard technique for maximizing energy harvest from solar panels. Petitioner argued that Nishi's microcomputer and control units directly teach the claimed functionality.
    • Motivation to Combine: A POSITA would be motivated to add the MPPT functionality taught by Nishi to the power supply of Mieth/Balogh for the simple and compelling reason of improving the overall efficiency of the solar power system. MPPT was a well-known and desirable feature for any solar power system at the time of the invention.
    • Expectation of Success: Integrating a known MPPT control strategy (Nishi) with a known power converter architecture (Mieth/Balogh) was a straightforward design choice for a POSITA seeking to create an optimized solar power system, with a high expectation of achieving predictable improvements in power output.

  • Additional Grounds: Petitioner asserted an additional obviousness challenge for claim 19 over Mieth, Balogh, and Liu (Patent 6,798,177). Liu was cited for its teaching of using a storage capacitor between converter stages to absorb power and provide backup energy, allegedly rendering obvious the claim limitation of a "power absorption circuit" that "includes a capacitor."

4. Key Claim Construction Positions

  • "a first stage and a second stage": Petitioner argued that this term should be construed according to its plain and ordinary meaning to a POSITA, which is "one or more circuit components that operate alone or together to provide a specified function set forth in the claim." The petition asserted that the term is not explicitly defined in the ’021 patent but is used consistently with its common meaning in the art of electronics to refer to functional blocks of a larger circuit. This construction is central to Petitioner's argument that the functional blocks disclosed in the prior art, such as Mieth's capacitor and auxiliary power supply, constitute the claimed "stages."

5. Relief Requested

  • Petitioner requests institution of an inter partes review and cancellation of claims 1-20 of the ’021 patent as unpatentable.