PTAB

IPR2018-01812

Semiconductor Components Industries LLC v. Power Integrations Inc

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1. Case Identification

2. Patent Overview

  • Title: Controller with Sensor Coupled to a Single Terminal
  • Brief Description: The ’871 patent discloses switching power converters, such as flyback converters, that utilize a controller with a sensor coupled to a single terminal. This single terminal receives a signal from an auxiliary winding of a transformer, which represents both the output voltage during the power switch’s off-time and the input line voltage during the switch’s on-time.

3. Grounds for Unpatentability

Ground 1: Claims 9, 10, and 13 are obvious over Reinhard in view of Kent.

  • Prior Art Relied Upon: Reinhard (Application # 2005/0254268) and Kent (Patent 4,447,841).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Reinhard disclosed the core controller architecture claimed in the ’871 patent. Reinhard’s controller used a single terminal (“U”) to receive a signal from an auxiliary winding that reflected the output voltage (positive pulse) during switch off-time and the input voltage (negative pulse) during switch on-time. Reinhard used this signal for output voltage regulation and over-voltage protection. However, Reinhard lacked robust short-circuit protection. Kent taught a well-known technique for adding such protection to a similar power converter. Kent’s circuit used the signal from an auxiliary winding to detect an undervoltage condition indicative of a short circuit or overload (meeting claims 9 and 10). Upon detection, Kent’s circuit outputted a fault signal to a low-frequency oscillator, which periodically disabled and re-enabled switching to implement an “auto-restart mode” (meeting claim 13).
    • Motivation to Combine: A Person of Ordinary Skill in the Art (POSITA) would have been motivated to combine Kent’s known overcurrent protection scheme with Reinhard’s similar power converter to improve it with the predictable benefit of short-circuit protection. This combination represented the application of a known technique (Kent’s protection circuit) to a similar device (Reinhard’s converter) to yield predictable results.
    • Expectation of Success: Because Reinhard already detected output voltage via an auxiliary winding, a POSITA would expect to be able to implement Kent’s protection scheme, which relies on the same principle, with predictable results.

Ground 2: Claims 9, 10, and 13 are obvious over Spampinato.

  • Prior Art Relied Upon: Spampinato (Patent 6,061,257).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner asserted that Spampinato, as a single reference, disclosed all limitations of the challenged claims. Spampinato described a flyback converter with a controller that received a signal from an auxiliary winding via a single terminal (the “DEM” pin). This signal inherently represented the output voltage during the switch’s off-time and the input voltage during its on-time. Spampinato’s controller included an output fault detector (comparator COMP1, an AND gate, and flip-flop FF2) that was coupled to the DEM pin. This detector was specifically designed to detect an output short circuit condition (meeting claims 9 and 10) by monitoring the auxiliary winding voltage during the switch off-time. Upon detecting a fault, the detector disabled the power switch. Spampinato further taught that its circuitry provided an "automatic start-up" once the short circuit condition ceased. It achieved this by having an undervoltage circuit reset the fault-detection flip-flop when the supply voltage dropped (due to the disabled switching), allowing switching to resume, thereby implementing an auto-restart mode (meeting claim 13).

4. Key Claim Construction Positions

  • "to represent" (Claim 8): Petitioner argued this term requires no formal construction and should be given its plain and ordinary meaning. The phrase defines characteristics of the signal itself—that it must contain information corresponding to both input and output voltages at different times. Petitioner contended it does not impose a requirement that the separately recited sensor must detect or act upon both pieces of information. This construction was central to arguing that prior art sensors, like Reinhard's, met the claim even if they only explicitly used one part of the signal (e.g., the output voltage portion) for a primary function.
  • "auto-restart signal" (Claim 13): Petitioner argued this term should be construed as a further definition of the "fault signal" recited in parent claim 8, not as a requirement for a second, distinct signal. The specification of the ’871 patent only disclosed a single signal from the "auto-restart detector" to the switching control. Therefore, the "fault signal" of claim 8 and the "auto-restart signal" of claim 13 were argued to be one and the same signal, which both indicates a fault and causes the controller to enter an auto-restart mode.

5. Relief Requested

  • Petitioner requested institution of an inter partes review and cancellation of claims 9, 10, and 13 of Patent 8,773,871 as unpatentable under 35 U.S.C. §103.