PTAB

IPR2016-01595

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: Switched Mode Power Converter with X-Capacitor Discharge
  • Brief Description: The ’457 patent relates to switched mode power converters designed to convert an AC input voltage to a DC output. The invention addresses the electric shock hazard posed by energy-storing X-capacitors in EMI filters by disclosing a circuit with a switchable discharge path that activates only upon disconnection from the AC source, thereby minimizing power loss during normal operation.

3. Grounds for Unpatentability

Ground 1: Obviousness over Leman and Skatulla - Claims 3, 6, 8, 13, 25, 27, 29, 30, and 34 are obvious over Leman in view of Skatulla

  • Prior Art Relied Upon: Leman (Patent 5,461,303) and Skatulla (International Publication No. WO 2008/086891).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Leman taught a conventional boost-type switched mode power converter that operates from an AC line voltage. Skatulla addressed the well-known problem of discharging X-capacitors in such converters by teaching a circuit that uses the converter’s own power switch as a load to dissipate the stored energy only after the AC power is disconnected. The combination of Leman’s standard converter architecture with Skatulla’s efficient discharge technique allegedly disclosed all limitations of the challenged claims.
    • Motivation to Combine: A person of ordinary skill in the art (POSITA) would combine Skatulla’s X-capacitor discharge functionality with Leman’s power converter to improve it with a known technique that solved a known problem. The motivation was driven by the dual goals of meeting industry safety standards for capacitor discharge and avoiding the constant power dissipation caused by conventional, always-on discharge resistors.
    • Expectation of Success: Because both Leman and Skatulla disclosed boost converter topologies, a POSITA would have a high expectation of success in incorporating Skatulla's discharge control scheme into the existing control circuitry (PWM device 20) of Leman's converter with predictable results.

Ground 2: Obviousness over Leman, Skatulla, and Ichisa - Claim 35 is obvious over Leman and Skatulla in view of Ichisa

  • Prior Art Relied Upon: Leman (Patent 5,461,303), Skatulla (WO 2008/086891), and Ichisa (Japanese Application # H10-185965).
  • Core Argument for this Ground:
    • Prior Art Mapping: This ground built upon the Leman/Skatulla combination to specifically address claim 35, which required a timer circuit that is reset in response to the AC voltage source reversing polarity. Petitioner contended that Ichisa explicitly taught such a circuit: a zero-cross detection circuit that monitors the AC input and resets a counter each time the voltage polarity reverses. The absence of zero-crossings for a predetermined period indicates a loss of AC power.
    • Motivation to Combine: Skatulla itself suggested that directly detecting the presence of the AC power source, rather than relying on capacitor charge decay, would offer a faster and more reliable method for triggering the discharge sequence. A POSITA seeking to implement this superior detection method in the Leman/Skatulla converter would be motivated to use a known, reliable technique like the zero-cross detection timer taught by Ichisa. The Japanese Examiner in a related application had already identified this technique as well-known art.
    • Expectation of Success: Petitioner asserted that applying Ichisa's well-known AC voltage detection circuit to the combined Leman/Skatulla converter was a predictable application of a known technique to improve the device's reliability and performance.

Ground 3: Obviousness over Skatulla and the ’369 Patent - Claims 3, 13, 25, 27, 29, 30, and 34 are obvious over Skatulla in view of the ’369 Patent

  • Prior Art Relied Upon: Skatulla (WO 2008/086891) and the ’369 Patent (Patent 5,285,369).
  • Core Argument for this Ground:
    • Prior Art Mapping: This ground addressed claim limitations related to integrated circuits and providing a start-up current. Skatulla taught the core capacitor discharge functionality using discrete components. The ’369 patent taught a monolithic switched mode power supply chip where the power MOSFET and control circuitry are integrated onto a single die. Critically, the ’369 patent also taught using the MOSFET structure itself to provide a start-up current to the control circuit, eliminating the need for external components and a dedicated pin.
    • Motivation to Combine: A POSITA would be motivated to replace Skatulla's discrete power switch and controller with the integrated solution taught by the ’369 patent to achieve the well-understood benefits of reduced component count, smaller physical size, and lower manufacturing cost. The ’369 patent’s technique for providing an integrated start-up current provided a further known advantage that a POSITA would seek to incorporate into Skatulla's design.
    • Expectation of Success: Integrating Skatulla's control logic into a monolithic chip that included the power switch, as taught by the ’369 patent, was a predictable design choice for product miniaturization and cost reduction, with a high expectation of success.
  • Additional Grounds: Petitioner asserted additional obviousness challenges based on Skatulla alone (claims 6-8); adding Liaw (Patent 6,259,618) to combinations to teach a multi-die integrated circuit (claim 31); and other permutations of the primary references that relied on similar design modification theories.

4. Key Claim Construction Positions

  • Petitioner proposed that the term "coupled" be construed as "coupled, either directly or indirectly."
  • This construction was argued to be necessary because claim elements in the ’457 patent require a single switch to be coupled to multiple points in the circuit that are not directly connected. For example, dependent claim 14 requires the switch to be coupled both "to the input of the power converter" and "across an output of a rectification circuit," which are necessarily separated by other components, thus mandating an interpretation that includes indirect coupling.

5. Relief Requested

  • Petitioner requested institution of an inter partes review and cancellation of claims 3, 6-8, 13, 25, 27, 29-31, and 34-35 of the ’457 patent as unpatentable under 35 U.S.C. §103.