DCT

7:24-cv-00331

Supronics LLC v. Home Depot USA Inc

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I. Executive Summary and Procedural Information

  • Parties & Counsel:
  • Case Identification: 7:24-cv-00331, W.D. Tex., 12/16/2024
  • Venue Allegations: Plaintiff alleges venue is proper because Defendant maintains regular and established places of business within the Western District of Texas and has committed the alleged acts of patent infringement in the district.
  • Core Dispute: Plaintiff alleges that Defendant’s Lithonia Lighting brand LED fixtures infringe three patents related to LED driver circuitry and the physical structure of LED chips.
  • Technical Context: The patents concern methods for efficiently powering strings of LEDs from AC power sources and the physical design of LED electrodes to maximize light output and current spread.
  • Key Procedural History: The complaint alleges that Defendant was notified of infringement of the patents-in-suit by Plaintiff's predecessor-in-interest via letters dated February 2, 2021, May 26, 2021, and March 24, 2022. Additionally, U.S. Patent No. 7,081,722 was the subject of an Inter Partes Review (IPR2020-00836), which concluded with a certificate issued on February 4, 2022. The IPR resulted in the cancellation of several claims, including original independent claim 1, but confirmed the patentability of other claims, including asserted dependent claim 3.

Case Timeline

Date Event
2005-02-04 Priority Date for ’722 and ’944 Patents
2006-07-25 ’722 Patent Issued
2008-10-21 ’944 Patent Issued
2009-12-29 Priority Date for ’212 Patent (Korean Application)
2013-09-03 ’212 Patent Issued
2020-04-17 Inter Partes Review (IPR) filed against ’722 Patent
2021-02-02 First pre-suit notice letter alleged sent to Defendant
2021-05-26 Second pre-suit notice letter alleged sent to Defendant
2022-02-04 IPR Certificate issued for ’722 Patent
2022-03-24 Third pre-suit notice letter alleged sent to Defendant
2024-12-16 Complaint Filed

II. Technology and Patent(s)-in-Suit Analysis

U.S. Patent No. 7,081,722, "Light Emitting Diode Multiphase Driver Circuit and Method," Issued July 25, 2006

The Invention Explained

  • Problem Addressed: Driving light-emitting diodes (LEDs) from a periodic power source, such as a standard AC wall outlet, typically requires bulky and failure-prone components like magnetic transformers and electrolytic capacitors to convert the time-varying voltage into a steady DC current (’722 Patent, col. 1:16-29).
  • The Patented Solution: The patent describes a method to drive a string of LEDs more directly. The string is divided into multiple series-connected groups. Each group is connected to ground through its own "phase switch." As the input voltage from the power source rises through its cycle, the LED groups are turned on sequentially. To improve efficiency and reduce heat, the phase switch for an upstream group can be turned off once the subsequent downstream group is activated, preventing a large voltage drop across the switch (’722 Patent, Abstract; col. 2:36-55).
  • Technical Importance: This circuit topology allows for the creation of LED drivers that do not require large energy storage capacitors, which can lead to smaller, more reliable, and longer-lasting lighting products (’722 Patent, col. 5:36-39).

Key Claims at a Glance

  • The complaint asserts claims 3, 23, and 24 (Compl. ¶21). Claim 3, a method claim, is the focus of the complaint's narrative infringement allegations.
  • Independent claim 1, from which claim 3 originally depended, was cancelled during an Inter Partes Review. Claim 3 was subsequently found patentable. The essential elements of the asserted method (claims 1 and 3 combined) are:
    • Providing a string of LEDs divided into series-connected groups.
    • Providing a power source to the string.
    • Coupling each group to a ground through a separate conductive path containing a phase switch.
    • Increasing input voltage to turn on the LED groups sequentially downstream.
    • Monitoring a phase voltage of each group.
    • Turning off the phase switch of a group when its phase voltage reaches a predetermined value.
  • The complaint reserves the right to assert other claims (Compl. ¶21).

U.S. Patent No. 7,439,944, "Light Emitting Diode Multiphase Driver Circuit and Method," Issued October 21, 2008

The Invention Explained

  • Problem Addressed: Over-voltage protection circuits are necessary to prevent damage to electronic components. However, if the input voltage hovers near the protection circuit's trigger point, the circuit can rapidly switch on and off, a phenomenon known as 'chattering,' which can be unstable or damaging (’944 Patent, col. 13:28-35, 45-50).
  • The Patented Solution: The patent claims a driver circuit that includes an over-voltage protection circuit coupled with a 'hysteresis circuit.' The hysteresis circuit alters the voltage threshold required to deactivate the protection circuit, creating separate 'turn-on' and 'turn-off' voltage levels. This prevents the circuit from chattering when the input voltage fluctuates near a single trip point (’944 Patent, col. 14:59-66, Claim 1).
  • Technical Importance: Adding hysteresis is a well-known technique for making comparators and protection circuits more robust and stable in real-world applications with noisy or fluctuating signals.

Key Claims at a Glance

  • The complaint asserts claims 1, 2, 4, 5, and 6 (Compl. ¶30).
  • Independent Claim 1 is broken down into its essential elements:
    • A string of LEDs divided into 'n' series-connected groups.
    • A plurality of phase switches, each coupled to a corresponding group and to ground.
    • An over-voltage protection circuit.
    • A hysteresis circuit configured to alter a voltage threshold of the over-voltage protection circuit at the point when the protection circuit de-activates.
  • The complaint reserves the right to assert other claims (Compl. ¶30).

U.S. Patent No. 8,525,212, "Light Emitting Diode Having Electrode Extensions," Issued September 3, 2013

  • Technology Synopsis: This patent addresses the physical layout of electrodes on an LED chip. The invention seeks to solve the problem that while electrode extensions are needed to spread current uniformly for better light emission, they can also block light and reduce the overall light-emitting area (’212 Patent, col. 2:8-18). The claimed solution is a novel geometric arrangement of 'upper' and 'lower' electrode extensions, where curved upper extensions 'enclose' the lower extensions to maximize current spreading while minimizing the reduction in the active light-emitting region (’212 Patent, Abstract).
  • Asserted Claims: The complaint asserts independent claim 1 and dependent claims 2, 3, 13, and 19 (Compl. ¶38).
  • Accused Features: The complaint alleges that the LEDs contained within the Lithonia Lighting FMLSL 14 20840 fixture have the physical structure recited in the claims of the ’212 patent (Compl. ¶38).

III. The Accused Instrumentality

Product Identification

The Lithonia Lighting FMLSL 14 20840 lighting fixture, which is sold by Defendant Home Depot (Compl. ¶21).

Functionality and Market Context

The complaint alleges the accused fixture is an LED-based lighting product that includes an 'adjustable brightness functionality' (Compl. ¶22). The infringement allegations suggest this fixture contains sophisticated driver circuitry that manages power delivery to the LEDs in a multiphase manner, incorporates over-voltage protection with hysteresis, and utilizes LED chips with a specific electrode layout. Lithonia Lighting is a prominent brand in the lighting industry, and Home Depot is a major retailer, suggesting the accused product has significant commercial placement.

IV. Analysis of Infringement Allegations

The complaint references preliminary claim charts in Exhibits D, E, and F, which were not attached to the filed complaint. Therefore, a detailed element-by-element analysis is not possible. The infringement theories are summarized below based on the complaint's narrative allegations.

  • ’722 Patent Infringement Allegations: The complaint alleges that the accused fixture directly infringes at least claim 3 (Compl. ¶¶21-22). The theory of infringement appears to be that the fixture's 'adjustable brightness functionality' inherently performs the patented method. When a user operates this function, the internal circuitry allegedly turns LED groups on and off sequentially by monitoring the phase voltage of each group to achieve the desired brightness level, thereby practicing the steps of the claim (Compl. ¶22).
  • ’944 Patent Infringement Allegations: The complaint alleges the accused fixture directly infringes at least claim 1 (Compl. ¶30). The infringement theory is that the fixture’s power-supply circuitry contains an over-voltage protection circuit to prevent damage from voltage spikes. This circuit is alleged to further include a 'hysteresis circuit' that modifies the trip-point voltage, corresponding to the elements of claim 1 (Compl. ¶30, referencing Exhibit E).
  • No probative visual evidence provided in complaint.

V. Key Claim Terms for Construction

  • Term: "monitoring a phase voltage of each group" (’722 Patent, Claim 3)

    • Context and Importance: This term is central to the feedback mechanism of the asserted method claim. The case may turn on whether the accused product's control system performs this specific type of monitoring. Practitioners may focus on this term because the patent discloses alternative control schemes, such as monitoring the main rectified input voltage ('Vrect') instead of individual phase voltages (’722 Patent, col. 5:6-9). The defense may argue the accused product uses such an alternative, non-infringing method.
    • Intrinsic Evidence for a Broader Interpretation: The term itself is general. A plaintiff might argue that any method of sensing a voltage that is indicative of a specific group's operational state constitutes "monitoring a phase voltage."
    • Intrinsic Evidence for a Narrower Interpretation: The primary embodiment (FIG. 3) shows distinct op-amps (e.g., U1D, U1C) and feedback paths for each phase. A defendant could argue this disclosure limits the term to a direct, individual sensing of the voltage at the node of each LED group.

  • Term: "a hysteresis circuit" (’944 Patent, Claim 1)

    • Context and Importance: The presence of a 'hysteresis circuit' is a required element of the asserted apparatus claim. The dispute will likely focus on whether the accused product contains a structure that meets this definition.
    • Intrinsic Evidence for a Broader Interpretation: Plaintiff may argue that the term should be construed functionally to cover any components that collectively add hysteresis to the over-voltage protection threshold, regardless of whether they are explicitly labeled or designed as a single "circuit."
    • Intrinsic Evidence for a Narrower Interpretation: The patent explicitly illustrates a hysteresis circuit with a specific topology, including a feedback resistor ('Rhys') connected between the output and non-inverting input of a comparator (’944 Patent, FIG. 20). The defense could argue that the term should be limited to this disclosed structure or its clear equivalents, rather than any circuit that might exhibit inherent hysteretic properties as a byproduct of its design.

VI. Other Allegations

  • Indirect Infringement: The complaint alleges induced infringement for all three patents. The factual basis for this allegation is that Defendant provides 'instruction, marketing, and/or installation materials' that allegedly guide customers and end-users to operate the accused fixtures in a manner that directly infringes the patents (e.g., by using the adjustable brightness feature) (Compl. ¶¶23, 31, 39).
  • Willful Infringement: The complaint alleges that Defendant's infringement has been willful since it received notice of the patents. This allegation is supported by specific dates of alleged pre-suit notice letters sent by Plaintiff's predecessor-in-interest on February 2, 2021, May 26, 2021, and March 24, 2022 (Compl. ¶¶19, 24, 28, 32, 36, 40).

VII. Analyst’s Conclusion: Key Questions for the Case

  • A core issue will be one of technical mechanism: Without the benefit of the complaint's claim charts, a primary question is whether discovery will show that the accused fixture's circuitry operates in the specific manner required by the claims. For the ’722 patent, does the control system monitor individual phase voltages, or does it use a different, non-infringing feedback loop? For the ’944 patent, does the fixture contain a discrete or identifiable 'hysteresis circuit,' or is any operational stability achieved through other means?
  • A key legal question will concern the impact of the ’722 patent’s IPR history: While asserted claim 3 survived the IPR, the invalidation of its original parent claim 1 suggests potential weaknesses. The case will test the strength of the surviving claims and may involve disputes over whether claim 3 can be properly asserted in its current form and whether prior art that invalidated claim 1 is relevant to the surviving claims.
  • A central question for damages will be willfulness: The complaint provides specific dates for multiple pre-suit notice letters. A crucial factual dispute will be what actions, if any, Defendant took in response to these notices. The outcome will significantly influence the potential for enhanced damages.