PTAB

IPR2016-00736

Silver Star Capital LLC v. Power Integrations Inc

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Petition
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1. Case Identification

2. Patent Overview

  • Title: Method and Apparatus for Improving Efficiency in a Switching Regulator at Light Loads
  • Brief Description: The ’079 patent discloses a switching regulator for switched-mode power supplies designed to improve efficiency at light loads. The regulator's control circuit operates at a fixed switching frequency for a first range of feedback signals and varies the switching frequency for a second, lighter-load range of feedback signals, purportedly without skipping cycles.

3. Grounds for Unpatentability

Ground 1: Anticipation of Claims 31, 34, 38, and 42 by Semmler

  • Prior Art Relied Upon: Semmler (Patent 5,757,631).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Semmler, which discloses a dual-mode switching power converter, teaches every element of the challenged claims. Semmler’s converter operates with a constant frequency during normal operating conditions and a frequency-modulating drive signal during light load conditions. Petitioner asserted that Semmler’s transition to variable frequency mode requires varying the on-time of the drive signal below a minimum threshold, thereby teaching the claimed ranges of on-time values corresponding to the different operating modes. For claims 34 and 42, which require on-time and off-time to vary simultaneously, Petitioner contended that Semmler's use of a voltage-controlled oscillator (VCO) to reduce frequency necessarily increases the off-time as the on-time is reduced, thus disclosing simultaneous variation.

Ground 2: Obviousness of Claims 31, 34, 38, and 42 over Semmler in view of Nguyen

  • Prior Art Relied Upon: Semmler (Patent 5,757,631), Nguyen (Patent 5,982,161).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that to the extent Semmler might not explicitly teach the simultaneous variation of both on-time and off-time in the variable frequency mode, Nguyen supplies this teaching. Nguyen is directed to a voltage regulator that expressly discloses that both the on-time (TON) and off-time (TOFF) of its switching regulator are variable to quickly accommodate changing load conditions and improve efficiency.
    • Motivation to Combine: A Person of Ordinary Skill in the Art (POSITA) would combine the teachings because both Semmler and Nguyen are analogous art addressing the same well-known problems of power conversion efficiency and slow transient response times in switching regulators. A POSITA seeking to improve the performance of Semmler's dual-mode system would have been motivated to incorporate Nguyen’s explicit control scheme for varying both on-time and off-time.
    • Expectation of Success: The references rely on nearly identical and well-understood circuit structures and control principles. A POSITA would have a reasonable expectation of success in combining them to create a more efficient and responsive dual-mode regulator with predictable results.

Ground 3: Obviousness of Claims 31, 34, 38, and 42 over Semmler in view of Dell and Rilly

  • Prior Art Relied Upon: Semmler (Patent 5,757,631), Dell (Patent 5,916,313), and Rilly (Patent 4,975,823).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner asserted that Dell and Rilly provide additional, well-known solutions for improving dual-mode regulators like Semmler’s, rendering the claimed combination obvious. Dell was cited for expressly teaching a regulator that is not limited to a fixed frequency mode but rather varies both frequency and pulse width (on-time and off-time) to quickly respond to load changes. Rilly was cited for teaching a dual-mode system (constant frequency in normal operation, variable in abnormal) that specifically varies on-time to avoid cycle skipping, a problem the ’079 patent purports to solve.
    • Motivation to Combine: A POSITA would combine these analogous art references to solve common industry problems. The need for a dual-mode frequency regulator taught by Semmler would lead a POSITA to consider known solutions from Rilly (for avoiding cycle skipping) and Dell (for varying both on-time and off-time to improve response). This combination would yield a predictably more efficient and robust design.
    • Expectation of Success: The combination involved applying known techniques to a known system to achieve predictable results, as all references are based on similar, well-understood circuit principles for power converters.

4. Key Claim Construction Positions

Petitioner adopted claim constructions from a related district court litigation, asserting they were consistent with the broadest reasonable interpretation standard.

  • “To vary a switching frequency of the power switch without skipping cycles...”: Construed as “changing the number of switching cycles per second of the power switch in response to the feedback signal while continuing to turn the switch on in each cycle.” This construction was central to arguments that prior art which varies on-time without ceasing operation meets the "without skipping cycles" limitation.
  • “on-time and off-time values of a drive signal... vary simultaneously”: Construed as “both the on-time and the off-time values... of the drive signal are changed.” This construction was critical for the obviousness grounds, where Petitioner argued secondary references explicitly taught changing both values to improve performance.

5. Relief Requested

  • Petitioner requests institution of inter partes review and cancellation of claims 31, 34, 38, and 42 of the ’079 patent as unpatentable.