PTAB

IPR2018-01811

Semiconductor Components Industries LLC v. Power Integrations Inc

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Petition
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1. Case Identification

2. Patent Overview

  • Title: Fault Protection for a Power Supply
  • Brief Description: The ’475 patent discloses a fault protection method for switching power supplies that use "on/off" control. The method involves monitoring a feedback signal to detect a fault condition and, upon detection, disabling power delivery to protect the circuit.

3. Grounds for Unpatentability

Ground 1: Obviousness over Barbehenn, King, and Grebene - Claims 17-22 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 titled "Bipolar and MOS Analog Integrated Circuit Design").
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Barbehenn taught a "bang-bang" switching power converter using a common 555 timer for on-off control via an opto-coupler feedback loop. While Barbehenn addressed input faults, it lacked robust output fault protection. King allegedly disclosed the missing element: a flexible protection circuit for switching converters that detects short-circuit output faults by monitoring a feedback signal. King’s circuit uses a first timer (e.g., a charging capacitor) to measure the duration of a fault signal; if the fault persists for a predetermined period, a second timer is triggered to disable switching. The combination of Barbehenn's base converter with King's protection circuit allegedly taught every limitation of the challenged claims, including timing a feedback signal to detect a fault and preventing power delivery in response.
    • Motivation to Combine: A POSITA would combine King's known output fault protection technique with Barbehenn's converter to improve it against the known problem of output short-circuits. Both patents relate to switching power converters, and King was cited on the face of Barbehenn, making the combination logical. A POSITA would consult Grebene, an industry-standard textbook, to understand the detailed internal circuitry of the 555 timer used in both Barbehenn and King, facilitating the integration.
    • Expectation of Success: Petitioner asserted that combining these elements would yield predictable results, as it involved applying a known technique (King) to a known device (Barbehenn) to achieve a known improvement.

Ground 2: Obviousness over Krupka and Kent - Claims 17-22 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 taught an on/off control switching power supply where a digital feedback signal (high or low) from a comparator either enabled or inhibited pulses to the switching device. While Krupka addressed overvoltage protection, it did not provide for short-circuit protection. Kent allegedly disclosed a compatible protection circuit designed to protect against short-circuit and overload conditions. Kent's circuit uses a detector and timing circuitry (including a timing capacitor) to measure the duration of a high feedback signal indicative of a fault. Once a fault is confirmed, Kent’s circuit outputs a disable signal. The combination allegedly taught timing Krupka's feedback signal with Kent's circuit to detect a fault and then using Kent’s disable signal to override Krupka's AND-gate, thereby preventing power delivery.
    • Motivation to Combine: A POSITA would combine Kent's fault protection circuit with Krupka's power supply to protect Krupka's components from damage caused by short-circuit conditions, a known problem. Kent's circuit was described as a flexible, separate module compatible with various converters, and Krupka's digital feedback signal (toggling high/low) provided a suitable input for Kent's detector. This combination would predictably improve the robustness of Krupka's design.
    • Expectation of Success: The combination involved integrating well-understood circuit blocks to achieve a predictable improvement in fault protection, giving a POSITA a reasonable expectation of success.

4. Key Claim Construction Positions

  • Petitioner argued that while no formal constructions were necessary because the prior art disclosed the claimed elements under any reasonable interpretation, it highlighted disagreements from co-pending litigation.
  • "timing the feedback signal": Petitioner contended this means "measuring the duration of the feedback signal." This contrasts with the Patent Owner's alleged position focusing on the time between cycles. Petitioner argued the combination of King or Kent taught timing the duration of the signal while it was in a fault state (e.g., high) using a timing capacitor.
  • "feedback signal cycling": Petitioner argued against the Patent Owner's allegedly narrow construction that would exclude analog signals and require discrete logic states. Petitioner asserted that Barbehenn's comparator-based opto-coupler and Krupka's digital output both met this limitation, as they produced feedback that was interpreted as being in one of two states (e.g., on/off or high/low).
  • "cycling separately": Petitioner contended this meant the switching signal and feedback signal were distinct and not based on one another. It argued that in both Barbehenn and Krupka, the high-frequency switching signal (from an oscillator) cycled many times during a single cycle of the lower-frequency feedback signal, thus meeting the limitation.

5. Relief Requested

  • Petitioner requests institution of an inter partes review and cancellation of claims 17-22 of the ’475 patent as unpatentable under 35 U.S.C. §103.