PTAB

IPR2016-01592

Semiconductor Components Industries LLC doing Business As On Semiconductor v. Power Integrations Inc

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Key Events
Petition
petition

1. Case Identification

2. Patent Overview

  • Title: Switch Mode Power Supply
  • Brief Description: The ’079 patent discloses switch mode power supply circuits designed to improve efficiency under light load conditions. The invention purports to overcome the disadvantages of prior art "cycle skipping" techniques by instead increasing the switching period (reducing frequency) for each cycle in a variable frequency mode as the load decreases.

3. Grounds for Unpatentability

Ground 1: Obviousness over Oda and Nakamura - Claims 10-12, 14-16, 36, and 44 are obvious over Oda in view of Nakamura.

  • Prior Art Relied Upon: Oda (Japanese Unexamined Patent Application Publication No. H10-323028) and Nakamura (Japanese Unexamined Patent Application Publication No. S59-144366).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Oda disclosed a switch mode power supply with a control circuit that operates at a fixed frequency for a first range of feedback signals (heavier loads) and varies the switching frequency for a second range of feedback signals (lighter loads) without skipping cycles. Oda's circuit uses a buck-type topology with an inductor as the energy transfer element. Nakamura taught that a switching regulator could be implemented with either a buck-type power stage (using an inductor) or a flyback-type power stage (using a transformer). Petitioner asserted that substituting Oda's buck-type stage with a flyback-type stage as taught by Nakamura would result in a power supply meeting the limitations of the challenged claims, particularly if the Board construes "energy transfer element" to require a transformer.
    • Motivation to Combine: A POSITA would combine Oda and Nakamura by replacing the buck-type power stage in Oda with a flyback-type power stage from Nakamura. The motivation was to achieve the well-known benefits of using a transformer, such as DC isolation between the input and output and better optimization for large step-up or step-down voltage conversion ratios.
    • Expectation of Success: The structures and functions of both buck and flyback power stages were well known. A POSITA would have had a high expectation of success in this simple substitution of one known power-stage topology for another to obtain a predictable result.

Ground 2: Obviousness over Oda and Gautherin - Claims 10, 36, and 44 are obvious over Oda in view of Gautherin.

  • Prior Art Relied Upon: Oda (Japanese Unexamined Patent Application Publication No. H10-323028) and Gautherin (Patent 4,772,995).

  • Core Argument for this Ground:

    • Prior Art Mapping: This ground was presented as an alternative should the Board disagree with Petitioner's proposed construction for claims 10, 36, and 44. Petitioner argued Oda taught a circuit where control of switching frequency is separate from control of the switch's on-time. Gautherin, in contrast, taught a variable-frequency control technique where the switching frequency is a direct function of the switch's on-time, such that as the on-time decreases, the switching frequency also decreases. Petitioner contended that Gautherin’s technique, where the frequency approaches a minimum value at the same time the on-time (and duty cycle) approaches zero, disclosed the key limitations of claims 10, 36, and 44.
    • Motivation to Combine: A POSITA would have been motivated to incorporate Gautherin's simplified variable-frequency control technique into Oda's light-load control scheme. This represents a simple substitution of one known method for reducing frequency at light loads for another, in order to obtain a predictable result: a switching regulator with a simplified variable-frequency mode that provides a wide control range.
    • Expectation of Success: Petitioner asserted that substituting Gautherin's known simplified scheme for frequency reduction into Oda's existing light-load control architecture was a straightforward modification that a POSITA could implement with a reasonable expectation of success.

  • Additional Grounds: Petitioner also asserted Ground 2, arguing that claims 10-12, 14-16, 36, and 44 are anticipated by Oda under §102, contingent upon the Board construing the term "energy transfer element" to include an inductor. A fourth ground, Ground 4, argued that claim 13 is obvious over Oda in view of the LM2575 datasheet, which taught incorporating a resistor divider in the feedback path to create an adjustable output voltage.

4. Key Claim Construction Positions

  • "Energy Transfer Element": Petitioner proposed construing this term as "an inductive element such as a transformer or an inductor." This construction was central to the petition, as it would mean that Oda's buck converter, which uses an inductor ("choke coil"), discloses this element, making Oda a stronger primary reference and potentially anticipatory.
  • "the switching frequency of the power switch is reduced...to a minimum frequency when a duty cycle percentage value...is substantially equal to zero percent" (claims 10, 36, 44): Petitioner argued this phrase describes a state of the apparatus, not an action. The proposed construction was "the switching frequency of the power switch is in a minimum frequency state with no cycle skipping at a time that a duty cycle percentage value...is substantially equal to zero percent." This construction was critical for the argument that Oda met the limitation, as Oda's switching frequency is already at its minimum value when the feedback signal causes the duty cycle to approach zero.

5. Relief Requested

  • Petitioner requested institution of an inter partes review and cancellation of claims 10-16, 36, and 44 of the ’079 patent as unpatentable under 35 U.S.C. §§ 102 and 103.