PTAB

IPR2015-01292

Wangs Alliance Corp v. Philips Lighting Holding BV

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Key Events
Petition

1. Case Identification

2. Patent Overview

  • Title: System, Method, and Circuit for Supplying Power to an LED Array
  • Brief Description: The ’890 patent discloses driver circuits for light-emitting diode (LED) arrays that use pulse width modulation (PWM) to supply a constant current. The technology aims to overcome inefficiencies and power loss associated with prior art methods, such as using current-limiting resistors, by employing a feedback loop to control the LED current.

3. Grounds for Unpatentability

Ground 1: Anticipation of Claims 7, 15, and 23 by Biebl

  • Prior Art Relied Upon: Biebl (Patent 6,400,101).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Biebl discloses every element of independent claims 7, 15, and 23. Biebl describes a drive circuit for an LED array that uses PWM to deliver a constant mean current value. Petitioner mapped Biebl’s components to the means-plus-function limitations of claim 7: the "means for sensing current" is Biebl’s measurement resistor (Rshunt) combined with an integrator or differential amplifier; the "means for generating a reference signal" is a voltage divider; the "means for comparing" is a regulator that compares the sensed and reference signals to generate a feedback signal; the "means for modulating pulse width" is a comparator that receives the feedback signal; and the "means for supplying power" is the power supply (UBatt) and transistor switch (T). The arguments for method claim 15 and circuit claim 23 mirror this mapping.

Ground 2: Obviousness of Claims 23 and 31 over Biebl in view of Hochstein

  • Prior Art Relied Upon: Biebl (Patent 6,400,101) and Hochstein (Patent 5,661,645).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner contended that since Biebl anticipates base claim 23, the only remaining issue is dependent claim 31, which recites specific power supply types (buck-boost, boost, buck, or flyback converter). Hochstein explicitly discloses an efficient "power factor correcting and voltage regulating buck/boost switchmode converter" for supplying power to an LED array.
    • Motivation to Combine: A POSITA would combine these references because they are in the same technical field and address the identical problem of minimizing power loss and heat dissipation in LED driver circuits. Biebl discloses voltage fluctuation issues with its simple battery power supply. A POSITA would have been motivated to replace Biebl’s basic power supply with Hochstein’s more stable and efficient switch-mode buck-boost converter to improve performance, reduce heat, and mitigate voltage fluctuations.
    • Expectation of Success: Success would have been expected, as this involves substituting a well-known, efficient power supply topology into a standard LED driver circuit to achieve predictable benefits of improved stability and efficiency.

Ground 3: Obviousness of Claims 7, 15, 23, and 31 over ST Micro Datasheet in view of Biebl

  • Prior Art Relied Upon: ST Microelectronics UCC2842/3842 Current Mode PWM Controller datasheet ("ST Micro Datasheet") and Biebl (Patent 6,400,101).
  • Core Argument for this Ground:
    • Prior Art Mapping: The ST Micro Datasheet discloses the UC2842, a commercially available PWM controller IC that contains all the functional blocks required by the challenged claims, including an error amplifier, a current sense comparator, and a PWM latch. The ’890 patent itself explicitly references this type of IC. Biebl provides the specific application context of using such a control circuit to drive an LED array load. Petitioner argued that the datasheet's error amplifier and current sense pin perform the sensing function, its internal 2.5V source serves as the reference signal, its current sense comparator performs the comparison, and its PWM latch and output stage perform the modulation and power supply functions.
    • Motivation to Combine: A POSITA would combine the teachings because Biebl discloses the overall LED driver circuit architecture, while the ST Micro Datasheet provides a well-known, off-the-shelf component (the UC2842 IC) for implementing the core control logic. A POSITA seeking to build the circuit in Biebl would naturally turn to a commercially available IC like the UC2842. Biebl provides the motivation to connect the general-purpose controller from the datasheet to an LED array load.
    • Expectation of Success: A POSITA would have had a high expectation of success, as it involved using a standard PWM controller IC for its intended purpose in a known application (driving an LED array) to achieve predictable current control.

4. Key Claim Construction Positions

Petitioner argued for constructions of the five means-plus-function limitations in independent claim 7 based on the corresponding structures disclosed in the ’890 patent’s specification. These constructions were central to all invalidity grounds.

  • “means for sensing current...”: The corresponding structure is one or more resistors and an operational amplifier (e.g., differential amplifier) for scaling the current.
  • “means for generating a reference signal”: The corresponding structure is an internal reference, such as the internal voltage reference of a PWM control IC.
  • “means for comparing the sensed current signal...”: The corresponding structure is a comparator or an operational amplifier that compares the sensed signal to the reference signal.
  • “means for modulating pulse width...”: The corresponding structure is a pulse width modulation (PWM) control circuit.
  • “means for supplying power...”: The corresponding structure is a power supply with at least one transistor or switch that receives a drive signal.

5. Relief Requested

  • Petitioner requests institution of an inter partes review and cancellation of claims 7, 15, 23, and 31 of the ’890 patent as unpatentable.