PTAB

IPR2018-01813

Semiconductor Components Industries LLC v. Power Integrations Inc

Log In
Key Events
Petition
petition Intelligence

1. Case Identification

2. Patent Overview

  • Title: Switching Power Supplies with Fault Protection
  • Brief Description: The ’475 patent discloses a protection circuit for switching power supplies that use an "on/off" control architecture. The circuit is designed to detect fault conditions, such as an output overload or short circuit, by using a timer (e.g., a capacitor) that measures the duration of a feedback signal state, and subsequently disable the power supply to prevent damage, with an auto-restart capability.

3. Grounds for Unpatentability

Ground 1: Claims 1-6, 10, and 16 are obvious over Barbehenn in view of King and Grebene.

  • Prior Art Relied Upon: Barbehenn (Patent 5,914,865), King (Patent 5,694,305), and Grebene (a 1984 textbook on analog circuit design).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Barbehenn disclosed the foundational elements of a switching power supply with a "bang-bang" on/off control architecture, including a switching device (FET), a feedback input (pin 4 of a 555 timer), and a feedback signal that cycles during normal operation but remains static during a fault. However, Barbehenn only addressed input fault protection. King was cited for its teaching of a dedicated output fault protection circuit that uses a timer (a capacitor) to detect a fault condition (e.g., a short circuit) by monitoring a feedback signal for a predetermined period. Upon fault detection, King's circuit disables switching for a second period and then attempts to restart, creating an auto-restart cycle. Grebene was used as a standard reference to illustrate the well-known internal circuitry of the 555 timer used in both Barbehenn and King.
    • Motivation to Combine: A POSITA would combine King's output fault protection circuit with Barbehenn's switching converter to improve it. It was well-known that power supplies required protection from output faults like short circuits to prevent component damage. King expressly taught that its protection circuit was flexible and could be incorporated into a variety of switching converters. A POSITA would therefore have been motivated to apply this known technique to a known device (Barbehenn) to achieve the predictable result of enhanced protection against output faults.
    • Expectation of Success: The combination was asserted to be predictable. Integrating King's fault detection, which monitors a feedback signal, into Barbehenn's system, which provides such a signal, would have been straightforward for a POSITA, yielding a converter with robust protection against both input (from Barbehenn) and output (from King) fault conditions.

Ground 2: Claims 1-6, 10, and 16 are obvious over Krupka in view of Kent.

  • Prior Art Relied Upon: Krupka (Patent 4,413,224) and Kent (Patent 4,447,841).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner asserted that Krupka disclosed a DC/DC conversion system with on/off control, where a feedback signal (based on output voltage) controls an AND-gate to either pass or inhibit pulses from a pulse generator to a switching device. This establishes the claimed switching device, feedback input, and cycling feedback/switching signals. Kent was cited for its disclosure of a separate protection circuit designed to guard against short-circuit and overload faults. Kent's circuit included a detector and timing circuitry (using a timing capacitor) to distinguish faults from normal start-up. When a fault is detected, the circuit disables switching and initiates an auto-restart cycle that repeats until the fault is removed.
    • Motivation to Combine: A POSITA would combine Kent's fault protection with Krupka's converter for the known benefit of adding short-circuit protection. While Krupka acknowledged overvoltage protection, the need to protect against other faults like short circuits was a well-known problem. Kent provided a flexible, cost-effective solution that could be added to various power converters by monitoring an input indicative of an overload. A POSITA would have recognized that Krupka's digital feedback signal, which remains high during a fault, could serve as the input to Kent's detector, thereby motivating the combination to improve the reliability of Krupka's circuit.
    • Expectation of Success: There would have been a high expectation of success. A POSITA would have understood how to couple the output of Kent's protection circuit to an input of Krupka's AND-gate to override the normal feedback signal and disable switching during a fault. This combination of known circuit blocks to achieve their intended functions would yield the predictable result of a power supply with both on/off regulation and auto-restarting fault protection.

4. Key Claim Construction Positions

  • "a timer": Petitioner argued this term should be construed simply as "a circuit element such as a capacitor or digital counter that provides a signal representative of a measurement of time," consistent with the patent’s specification. Petitioner contended that Patent Owner’s proposed construction in related litigation ("a circuit that measures time") was improperly broad and sought to include other circuit elements beyond the core timing component.
  • "the feedback signal cycling between a first state and a second state": Petitioner argued against Patent Owner's proposed litigation construction that would have limited the term to only discrete logic states and excluded signals that vary in an analog fashion. Petitioner contended this improperly imported limitations and replaced the generic term "cycling" with the narrower, un-claimed term "pulsing."

5. Relief Requested

  • Petitioner requested the institution of an inter partes review and the cancellation of claims 1-6, 10, and 16 of the ’475 patent as unpatentable under 35 U.S.C. §103.