PTAB

IPR2022-00503

Samsung Electronics Co Ltd v. Bishop Display Tech LLC

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Key Events
Petition

1. Case Identification

2. Patent Overview

  • Title: Semiconductor Light Source Driving Apparatus and Semiconductor Light Source Driving Method
  • Brief Description: The ’830 patent discloses a driving apparatus for a semiconductor light source, such as an LED, designed to maintain constant control performance. The invention uses a feedback loop that adjusts the output voltage from a voltage source based on both the detected output current and the detected impedance of the light source.

3. Grounds for Unpatentability

Ground 1: Obviousness over Ghanem - Claims 1 and 5 are obvious over Ghanem in view of the knowledge of a POSITA.

  • Prior Art Relied Upon: Ghanem (Patent 6,285,139).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Ghanem discloses a "simple low-cost" LED driver circuit that teaches nearly every element of the challenged claims, including a voltage source, an output current detector, a current command section, and a current comparator. Ghanem addresses the known problem of changing LED impedance due to temperature by incorporating a thermistor, which serves as an indirect analog for detecting the LED's impedance to help regulate the current.
    • Motivation to Combine (with POSITA knowledge): Petitioner contended that a person of ordinary skill in the art (POSITA) would recognize Ghanem’s thermistor-based solution as an imprecise and indirect method for compensating for the LED's dynamic impedance. A POSITA would be motivated by fundamental engineering principles to improve Ghanem’s circuit by replacing the indirect thermistor measurement with a direct measurement of the LED’s impedance using the well-known Ohm’s Law (R=V/I).
    • Expectation of Success: A POSITA would have a high expectation of success in implementing this modification. Applying Ohm's Law requires only basic calculations and well-known components (like voltage and current sensors, which Ghanem already uses in part) to achieve a more accurate and reliable impedance value than that provided by the thermistor.

Ground 2: Obviousness over Ghanem in view of Nishimura - Claims 1, 2, and 5 are obvious over Ghanem in view of Nishimura.

  • Prior Art Relied Upon: Ghanem (Patent 6,285,139), Nishimura (Patent 7,332,699).

  • Core Argument for this Ground:

    • Prior Art Mapping: Petitioner asserted Ghanem provides the foundational closed-loop LED driver circuit, while Nishimura explicitly teaches the key missing element: a method for directly measuring the dynamic impedance of an LED. Nishimura discloses using voltage and current sensors to estimate dynamic impedance by dividing the measured voltage by the measured current (ΔV/ΔI=R). This teaching directly satisfies the "impedance detecting section" limitation of claim 1. Nishimura's division calculation also explicitly teaches the "divider" element required by dependent claim 2.
    • Motivation to Combine: A POSITA reviewing Ghanem’s circuit, with its stated goal of maintaining constant light intensity, would seek to improve its rudimentary thermistor-based impedance compensation. Nishimura addresses the exact same technical problem but provides a superior, explicit solution. A POSITA would combine Nishimura's direct measurement technique into Ghanem's driver architecture to create a more accurate and robust system, yielding predictable results.
    • Expectation of Success: The combination involved applying a known, superior technique (Nishimura's direct measurement) to an existing device (Ghanem's driver) to achieve a predictable improvement in performance. This straightforward substitution would have been readily achievable for a POSITA.

  • Additional Grounds: Petitioner asserted additional obviousness challenges based on Tripathi (Patent 7,262,559) alone and in combination with Nishimura. These grounds relied on similar theories, arguing Tripathi's disclosure of a short/open circuit detection system taught or suggested impedance detection, which a POSITA would have been motivated to combine with Nishimura's more precise, direct impedance measurement techniques.

4. Arguments Regarding Discretionary Denial

  • Petitioner argued against discretionary denial under Fintiv, asserting that the parallel district court litigation is complex and its schedule is uncertain. The litigation involves 13 patents asserted against over 1,000 products, making a trial delay for the ’830 patent likely. Petitioner noted that the court has not yet invested significant resources, as discovery is in its early stages and no Markman hearing has occurred. To prevent overlap, Petitioner offered a stipulation not to pursue in district court any invalidity ground raised or that could have been reasonably raised using the prior art asserted in the petition.

5. Relief Requested

  • Petitioner requests institution of an inter partes review and cancellation of claims 1, 2, and 5 of Patent 8,093,830 as unpatentable.