PTAB

IPR2018-01818

Semiconductor Components Industries, LLC d/b/a ON Semiconductor v. Power Integrations, Inc.

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1. Case Identification

2. Patent Overview

  • Title: Controller for power converter and method of controlling a power converter
  • Brief Description: The ’483 patent describes controllers for switching power converters, specifically flyback-type converters. The purported invention involves using a single terminal coupled to a transformer’s auxiliary winding to receive a signal that is representative of both the converter’s output voltage (during the power switch off-time) and its input line voltage (during the power switch on-time).

3. Grounds for Unpatentability

Ground 1: Obviousness over Spampinato and Mobers - Claims 6, 8, 9, 12, and 13 are obvious over Spampinato in view of Mobers

  • Prior Art Relied Upon: Spampinato (Patent 6,061,257) and Mobers (Patent 6,542,386).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner asserted that Spampinato discloses a flyback power converter with a controller that uses an auxiliary winding to sense a voltage signal representative of the converter’s output. This signal is monitored at a single terminal (the "DEM" pin) to detect output short-circuit conditions. Mobers was argued to disclose a similar flyback converter that uses its auxiliary winding to sense information about both the output voltage and the input line voltage to implement protection schemes. Critically, Mobers teaches using the input line voltage information, sensed as a current signal during the switch on-time, for an over-power protection circuit. Petitioner contended that combining these references results in a controller with a sensor at a single terminal that receives a signal representing both output voltage (as a voltage, per Spampinato) and input voltage (as a current, per Mobers), thereby meeting the limitations of the challenged claims. The dependent claims requiring an integrated circuit controller (claims 8, 12) and an integrated power switch (claim 13) were alleged to be disclosed or suggested by both references.
    • Motivation to Combine: A person of ordinary skill in the art (POSITA) would combine Mobers’s over-power protection system with Spampinato’s similar converter to gain the known benefit of input-voltage-based protection. Petitioner argued this is a predictable application of a known technique (Mobers’s protection circuit) to a similar device (Spampinato’s converter). Both references describe compatible current-mode control architectures, facilitating the combination.
    • Expectation of Success: A POSITA would have a high expectation of success because the underlying circuit topologies are similar. Furthermore, Petitioner argued that Mobers’s method for sensing the input line voltage (via a negative-swinging current signal) would not interfere with Spampinato’s method for sensing the output voltage (via a positive-swinging voltage signal), making the combination technically straightforward and its results predictable.

Ground 2: Obviousness over Spampinato - Claim 8 is obvious over Spampinato

  • Prior Art Relied Upon: Spampinato (Patent 6,061,257).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Spampinato, by itself, renders claim 8 obvious. The core of this argument rests on the inherent properties of a flyback converter. Petitioner asserted that the magnetic coupling in Spampinato’s transformer inherently causes the signal at the auxiliary winding to represent both the output voltage (during switch off-time) and the input voltage (during switch on-time), even if Spampinato’s control logic only explicitly uses the output voltage information for its short-circuit protection. Because the challenged claims only require the signal to represent both voltages—not that the sensor must use or act upon both—Spampinato’s disclosure was alleged to meet this limitation. Spampinato was also argued to expressly disclose an integrated circuit controller and contemplate the integration of the power switch, thereby meeting all limitations of claim 8.
    • Motivation to Combine (Rationale for Obviousness): The obviousness rationale is based on the knowledge of a POSITA. A POSITA would understand the fundamental physics of a flyback converter and recognize that the signal at Spampinato’s "DEM" terminal naturally contains information about both the input and output voltages. Therefore, it would have been obvious that Spampinato’s sensor, coupled to this terminal, receives a signal meeting the claim limitations.

4. Key Claim Construction Positions

  • "to represent" (Claim 1): Petitioner argued this term requires no construction and should be given its plain and ordinary meaning. The central contention was that this phrase defines a characteristic of the signal itself, not a required function of the sensor. In other words, the claim requires the signal received at the single terminal to contain information representative of both input and output voltages, but does not require the sensor to be configured to detect, process, or otherwise respond to both pieces of information. This interpretation is critical to the argument that Spampinato alone renders claims obvious, as Spampinato’s sensor only acts on the output voltage information, even though the input voltage information is inherently present in the signal it receives.

5. Key Technical Contentions (Beyond Claim Construction)

  • Inherent Nature of Auxiliary Winding Signal: The petition’s central technical premise, which underpins multiple grounds, is that the dual-voltage representation on an auxiliary winding is an inherent and well-known characteristic of flyback converter topology. Petitioner asserted that any such converter will naturally produce a positive voltage swing reflecting the output voltage during the switch off-time and a negative voltage swing reflecting the input voltage during the switch on-time. The patent’s "purported advancement" was characterized as nothing more than the recognition of this fundamental and unavoidable electrical behavior, not a patentable invention.

6. Arguments Regarding Discretionary Denial

  • Petitioner argued against potential discretionary denial by highlighting that the specific claims challenged in this IPR (6, 8, 9, 12, and 13) were not at issue in the co-pending Delaware litigation between the parties. This was presented to demonstrate that the IPR would not be an inefficient duplication of efforts being undertaken in the district court, a key factor in avoiding discretionary denial.

7. Relief Requested

  • Petitioner requested the institution of an inter partes review and the cancellation of claims 6, 8, 9, 12, and 13 of the ’483 patent as unpatentable.