PTAB

IPR2018-01814

Semiconductor Components Industries LLC v. Power Integrations Inc

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1. Case Identification

2. Patent Overview

  • Title: Fault Protection for a Power Supply
  • Brief Description: The ’788 patent discloses a fault protection circuit for switching power supplies using on/off feedback control. The circuit uses a timer to detect a fault condition based on the state of a feedback signal and, in response, disables a switching device to prevent damage, with an auto-restart feature to resume operation once the fault is cleared.

3. Grounds for Unpatentability

Ground 1: Claims 1-4, 7, and 13 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 integrated circuit design).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Barbehenn disclosed a basic "bang-bang" AC-DC switching converter that uses a 555 timer and an optocoupler-based feedback loop to provide on/off control. This combination was alleged to teach the switching device, feedback loop, and the feedback signal cycling between two states during normal operation, as required by claim 1. However, Barbehenn lacked robust output fault protection. King was argued to remedy this deficiency by teaching a flexible fault protection circuit that uses timers to detect short-circuit output faults. King’s circuit monitors a feedback signal and, if the signal indicates a fault for a first period, disables switching for a second period before attempting to restart. Grebene was cited as a standard technical reference illustrating the well-known internal circuitry of the 555 timer used in both Barbehenn and King, providing a POSITA with the necessary background knowledge for implementation.
    • Motivation to Combine: A POSITA would combine King's fault protection circuit with Barbehenn's power converter to address the well-known problem of output faults like short circuits. Petitioner asserted this was a simple application of a known technique (King's circuit) to a known device (Barbehenn's converter) to improve its safety and reliability, yielding predictable results. King itself was cited on the face of Barbehenn, suggesting its relevance. A POSITA would consult Grebene to understand the standard operation of the 555 timer common to both primary references.
    • Expectation of Success: Petitioner contended that since King’s protection circuit was designed for broad applicability with various switching converters and relied on a generic feedback signal, a POSITA would have a high expectation of success in integrating it with Barbehenn’s standard architecture.

Ground 2: Claims 1-4, 7, and 13 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 argued that Krupka disclosed a DC/DC conversion system with an "on/off" switching control scheme. Krupka’s circuit used a pulse generator, a switching device, and a feedback loop with a comparator that generates a digital high/low feedback signal to either permit or inhibit switching pulses. This was asserted to teach the core power supply architecture of claim 1. Kent was argued to supply the claimed fault protection, disclosing a circuit that protects against short-circuit and overload conditions. Kent’s circuit uses a detector and timing circuitry (including a timing capacitor) to monitor a signal indicative of an overload. Upon detecting a fault that persists for a set duration, the circuit disables switching and initiates an auto-restart cycle.
    • Motivation to Combine: A POSITA would be motivated to add Kent's known output fault protection to Krupka's power supply to protect components from damage during a short circuit, a known industry problem. Kent's circuit was described as a flexible, separate module compatible with various converters. Given that Krupka’s circuit produced a digital feedback signal that would remain high during a fault, a POSITA would have recognized it as a suitable input for Kent's detector, making the combination straightforward.
    • Expectation of Success: Petitioner argued success would be expected because both references operate in the same field of switching power converters. The combination involved applying a known solution (Kent's fault protection) to address a known problem (output faults) in a similar, known system (Krupka's power supply), which would yield the predictable result of enhanced circuit protection.

4. Key Claim Construction Positions

  • Petitioner argued that no formal claim constructions were necessary, but highlighted several terms disputed in co-pending litigation to show the prior art met the claim limitations under either party's proposed construction.
  • "a timer": Petitioner proposed a straightforward construction of "a circuit element such as a capacitor or digital counter that provides a signal representative of a measurement of time." This was contrasted with the Patent Owner's allegedly improper construction that sought to include other, external circuit elements.
  • "the feedback signal cycling periodically...": Petitioner argued against the Patent Owner's proposed narrow construction that would require the signal to cycle between "discrete first and second logic states" and exclude analog variations. Petitioner contended its broader construction, "repeatedly varying between two states," was correct.
  • "cycling separately": Petitioner asserted the plain meaning was sufficient, or alternatively "the switching signal cycling is not based [on] the cycling of the feedback signal," countering the Patent Owner's allegedly complex and unsupported proposed definition.

5. Relief Requested

  • Petitioner requested institution of an inter partes review and cancellation of claims 1-4, 7, and 13 of the ’788 patent as unpatentable under 35 U.S.C. §103.