PTAB

IPR2023-00879

SMA Solar Technology AmERICa LLC v. Tigo Energy Inc

Log In

1. Case Identification

2. Patent Overview

  • Title: Systems and Methods for Enhanced Efficiency Auxiliary Power Supply Module
  • Brief Description: The ’021 patent discloses a power supply for a solar system having a two-stage power converter. The system includes a control circuit designed to prevent false starts when the solar panel provides insufficient power by using a switchable preload resistor and a "break before make" delay mechanism.

3. Grounds for Unpatentability

Ground 1: Anticipation of Claims 1-7 and 9 under §102

  • Prior Art Relied Upon: Mieth (DE3725476)
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Mieth discloses every limitation of independent claim 1. Mieth teaches a two-state circuit for supplying power from a variable source like a solar generator. In a first state (low input voltage), a preliminary load (element 11) is switched "in" by a transistor (12) to load the first stage, while an auxiliary power supply (19, the second stage) is disabled. In a second state (sufficient input voltage), a comparator (9) detects the voltage threshold, turns the transistor "off" to disconnect the preliminary load, and a second comparator (13) enables the auxiliary power supply. Petitioner contended this directly maps to the claimed method of connecting a switchable load while disabling the second stage, and subsequently disconnecting the load and enabling the second stage.
    • Key Aspects: Petitioner asserted that the generic "load 20" in Mieth would be understood by a Person of Ordinary Skill in the Art (POSA) to include a microcontroller, and that Mieth's cascaded comparators inherently provide the claimed "break before make" timing delay between disconnecting the load and enabling the second stage.

Ground 2: Obviousness of Claims 1, 8, 10-12, 15-18, and 20 under §103

  • Prior Art Relied Upon: Mieth (DE3725476) and Balogh (Patent 6,246,592)
  • Core Argument for this Ground:
    • Prior Art Mapping: This ground asserted that to the extent Mieth's simple stages do not fully teach the "first stage" and "second stage" of the claims (specifically for claims requiring step-down converters), it would have been obvious to implement Mieth's startup control logic using the cascaded power converter architecture taught by Balogh. Balogh discloses using cascaded DC-DC converters, such as first and second buck converter stages, specifically for applications like solar power that require large input-to-output voltage conversion ratios.
    • Motivation to Combine: A POSA would combine Mieth's startup control method with Balogh's cascaded converter topology to create a robust power supply for solar applications. Mieth addresses the problem of variable input voltage at startup, while Balogh provides an efficient and well-known architecture for stepping down the high DC voltages typical of solar panels. Combining the two would leverage Balogh's efficient power conversion with Mieth's reliable startup sequence.
    • Expectation of Success: The combination involved applying a known control strategy (Mieth) to a standard power converter architecture (Balogh) to achieve the predictable benefit of a reliable, high-efficiency power supply for a solar system. Petitioner argued there were no technical hurdles to this combination.

Ground 3: Obviousness of Claims 13 and 14 under §103

  • Prior Art Relied Upon: Mieth (DE3725476), Balogh (Patent 6,246,592), and Nishi (Application # 2005/105224)

  • Core Argument for this Ground:

    • Prior Art Mapping: This ground challenged dependent claims 13 and 14, which add the limitation that the "micro-controller is configured to maximize power generated by the power source." Petitioner argued that after combining Mieth and Balogh to create the basic two-stage power supply, it would have been obvious to add the functionality taught by Nishi. Nishi explicitly discloses a photovoltaic power generation system where a microcomputer implements maximum power point tracking (MPPT) by controlling inverter circuitry to maximize the power output from solar cells.
    • Motivation to Combine: A POSA designing a power supply for a solar system (the context of Mieth and Balogh) would be highly motivated to incorporate MPPT, a standard and crucial feature for maximizing energy harvest and overall system efficiency. Nishi provided an express teaching of using a microcontroller for this exact purpose. The motivation was to improve the fundamental performance of the solar power system.
    • Expectation of Success: Integrating a known MPPT algorithm, as taught by Nishi, into the microcontroller of the power supply from Mieth and Balogh would have been a routine design choice for a POSA with a reasonable expectation of success.

  • Additional Grounds: Petitioner asserted an additional obviousness challenge against claim 19 based on the combination of Mieth, Balogh, and Liu (Patent 6,798,177), where Liu was cited for its teaching of using a storage capacitor between converter stages to provide backup power.

4. Key Claim Construction Positions

  • Petitioner argued for a broad construction of the term "a first stage and a second stage" to mean simply "a first group of one or more circuit elements and a second group of one or more circuit elements." This construction was central to Petitioner's anticipation argument, as it allowed for mapping Mieth's components (e.g., a capacitor and a preliminary load) to the claimed "first stage" and its auxiliary power supply circuit to the "second stage," even if they were not conventional power converter blocks. Petitioner contended this broad meaning was consistent with the patent's own usage and the common understanding of a POSA.

5. Relief Requested

  • Petitioner requests that the Board institute an inter partes review of claims 1-20 of the ’021 patent and cancel those claims as unpatentable.