PTAB

IPR2015-01294

Wangs Alliance Corp v. Philips Lighting North America Corp

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Key Events
Petition

1. Case Identification

2. Patent Overview

  • Title: LED Power Control Circuitry
  • Brief Description: The ’399 patent discloses circuit arrangements and methods for powering and controlling LED-based light sources. The invention specifically addresses using conventional AC dimmer circuits, which produce signals "other than standard line voltages," to control the intensity of LEDs by interpreting variations in the AC signal.

3. Grounds for Unpatentability

Ground 1: Anticipation of Claims 7, 8, 17, 28, and 34 by Hochstein

  • Prior Art Relied Upon: Hochstein (Patent 5,661,645).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Hochstein disclosed every element of the challenged independent and dependent claims. Hochstein teaches a power supply for an LED array, such as for a traffic signal, that is configured to receive a power-related signal from an AC source other than a standard AC line voltage. Specifically, Hochstein describes using a half-wave rectified signal from a traffic signal controller as a "dimming command." The power supply's controller detects this dimming signal and variably controls the light intensity of the LEDs. This control is achieved by adjusting the output voltage of a switchmode power supply or by using an optional pulse width modulation (PWM) modulator, which inherently controls the light based on the variable duty cycle of the power-related signal. The apparatus is controlled by a user interface that issues the dimming command, thus variably controlling a parameter of light (intensity).

Ground 2: Obviousness of Claims 7, 8, 17, 28, and 34 over Bogdan in view of Hochstein

  • Prior Art Relied Upon: Bogdan (Patent 6,225,759) and Hochstein (Patent 5,661,645).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner asserted Bogdan teaches a "universal dimmer" circuit for controlling various light sources, including gas discharge lamps. Bogdan's circuit uses a switch encoder operated by a user to generate a "chopped" AC waveform (a power-related signal with a variable duty cycle). A decoder and load controller then interpret this signal to control the light's intensity. While Bogdan does not explicitly mention LEDs, Hochstein teaches applying similar dimming control principles specifically to LED arrays, which were known to be replacing the types of lamps Bogdan addresses.
    • Motivation to Combine: Petitioner contended that a person of ordinary skill in the art (POSITA) would have been motivated to combine the references because they operate in the same technical field and address the common problem of dimming non-traditional light sources. A POSITA would have found it obvious to adapt Bogdan’s versatile dimmer system to control LEDs, a prevalent and energy-efficient lighting technology, by incorporating the LED-specific driver and control teachings of Hochstein.
    • Expectation of Success: Petitioner argued the combination would have been a predictable and straightforward integration. Modifying Bogdan’s load controller to drive the LED array from Hochstein, instead of a gas discharge lamp, represented a simple substitution of one known type of lighting load for another, with a high expectation of success.

Ground 3: Obviousness of Claims 7, 8, 17, 18, 28, and 34 over Hochstein in view of Faulk

  • Prior Art Relied Upon: Hochstein (Patent 5,661,645) and Faulk (Patent 5,818,705).
  • Core Argument for this Ground:
    • Prior Art Mapping: This ground focused primarily on the limitations of dependent claim 18, which requires power circuitry comprising a rectifier that provides a rectified signal to a low-pass filter. Hochstein discloses a power supply with both a rectifier and an EMI filter (which functions as a low-pass filter), but it places the filter before the rectifier. Faulk, in the context of creating compact and space-efficient AC power adapters, explicitly teaches a design where an EMI filter is placed after the bridge rectifier.
    • Motivation to Combine: Petitioner argued that a POSITA implementing Hochstein’s design would encounter problems with bulky and heat-producing components, as a pre-rectifier filter requires large X-type capacitors. Hochstein itself warns against generating excess heat near thermally sensitive LEDs. A POSITA would thus be motivated to find a solution to reduce the size and heat of the power supply. Faulk provides this solution, teaching that a post-rectifier filter configuration allows for the use of smaller, more efficient components. Therefore, a POSITA would combine Faulk's filter placement with Hochstein's LED control circuit to create a more compact and thermally stable device.
    • Expectation of Success: The relative placement of a filter and rectifier was a known design choice with predictable trade-offs. A POSITA would have a clear expectation that modifying Hochstein according to Faulk’s teaching would successfully result in a smaller, more efficient power supply suitable for use with LEDs.

4. Key Claim Construction Positions

  • The term "Duty Cycle" was construed according to its plain and ordinary meaning, defined as "the ratio of pulse duration to pulse period, expressed as a percentage." This construction was central to Petitioner's arguments, as it allowed them to assert that the half-wave rectified signals (in Hochstein) and "chopped-out" AC waveforms (in Bogdan) inherently possess a variable duty cycle of 50% or otherwise, thereby satisfying this key limitation in the challenged claims.

5. Relief Requested

  • Petitioner requested institution of an inter partes review and cancellation of claims 7, 8, 17, 18, 28, and 34 of Patent 7,038,399 as unpatentable.