North Star Home LLC v. Ningbo Bainiao Shangmao Youxian Gongsi

I. Executive Summary and Procedural Information

• Parties & Counsel:
  • Plaintiff: North Star Home LLC (Illinois)
  • Defendant: Ningbo Bainiao Shangmao Youxian Gongsi d/b/a Phoenix Home US (People's Republic of China)
  • Plaintiff’s Counsel: Glacier Law LLP
• Case Identification: 1:25-cv-12793, N.D. Ill., 10/20/2025
• Venue Allegations: Plaintiff alleges venue is proper because Defendant, a foreign entity, has committed acts of infringement and has significant contacts within the district by directly targeting, offering to sell, selling, and shipping accused products to consumers in the Northern District of Illinois via an interactive Amazon storefront.
• Core Dispute: Plaintiff alleges that Defendant’s electric-blanket products infringe a patent related to safe heating circuit technology.
• Technical Context: The technology concerns safety circuits for electric blankets, which are designed to provide precise temperature regulation and detect fault conditions like short circuits or open circuits to prevent overheating and fire hazards.
• Key Procedural History: The complaint does not mention any prior litigation, Inter Partes Review (IPR) proceedings, or licensing history related to the patent-in-suit.

Case Timeline

Date	Event
2021-08-18	’672 Patent Priority Date
2025-02-04	’672 Patent Issue Date
2025-10-20	Complaint Filing Date

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

U.S. Patent No. 12,219,672 - "Safe Heating Circuit and Electric Blanket Provided with Safe Heating Circuit"

• Patent Identification: U.S. Patent No. 12,219,672, “Safe Heating Circuit and Electric Blanket Provided with Safe Heating Circuit,” issued February 4, 2025 (the "’672 Patent").

The Invention Explained

• Problem Addressed: The patent’s background section describes the safety risks associated with conventional electric blankets, such as electric leakage or fire. These hazards can arise from inaccurate temperature control or the aging of key components, which can lead to short circuits or open circuits that cause dangerous local overheating (’672 Patent, col. 1:20-33).
• The Patented Solution: The invention is a safety circuit that employs a dual-mode temperature control and fault detection system. It uses both a Positive Temperature Coefficient (PTC) heating element, which inherently increases resistance as it gets hotter, and a separate Negative Temperature Coefficient (NTC) element to sense temperature changes (’672 Patent, col. 1:36-46). As illustrated in Figure 1, a controller monitors two distinct signals: a "first temperature voltage" derived from the ground current of the main PTC heating element, and a "second temperature voltage" derived from a "leakage current" transmitted through the NTC element to a separate "sensing element." By comparing these voltages to set thresholds, the controller can precisely regulate temperature and detect faults in different parts of the circuit, switching off power via a "first switching element" when necessary (’672 Patent, Abstract; col. 1:47-62).
• Technical Importance: The use of two different temperature-sensing mechanisms (PTC self-regulation and NTC leakage current sensing) provides a redundant safety system designed for more precise temperature control and more robust fault detection than single-sensor systems (’672 Patent, col. 4:61-65).

Key Claims at a Glance

• The complaint asserts independent claim 1 and dependent claims 2, 5, 6, 13, 14, 16, and 17 (Compl. ¶10).
• Independent Claim 1:
  • a PTC electric heating element, generating heat when being electrified;
  • a first switching element, coupled into a ground loop of the PTC electric heating element and configured to switch on or off a power loop of the PTC electric heating element based on an on-off control signal;
  • a first voltage acquisition circuit, configured to sample a first temperature voltage based on a ground current of the PTC electric heating element;
  • an NTC element, disposed between the PTC electric heating element and a sensing element;
  • the sensing element, configured to receive a leakage current from the PTC electric heating element transmitted by the NTC element;
  • a second voltage acquisition circuit, configured to sample a second temperature voltage based on the leakage current; and
  • a controller, configured to compare the first temperature voltage or the second temperature voltage to a set temperature voltage and output the on-off control signal based on a comparison result.
• The complaint does not explicitly reserve the right to assert additional claims.

III. The Accused Instrumentality

Product Identification

• The complaint identifies "electric-blanket products" sold by Defendant through its Amazon storefront "Phoenix Home US" as the "Accused Products" (Compl. ¶4, ¶9). Specific product models are not named in the body of the complaint but are referenced as being listed in Exhibit C, which was not publicly available with the complaint.

Functionality and Market Context

• The complaint alleges the Accused Products "incorporate a heating-circuit design that infringes" the ’672 Patent (Compl. ¶20). It further alleges that these products "embody the patented safe-heating circuit technology" (Compl. ¶8). No specific technical details about the circuitry or operation of the Accused Products are provided in the complaint itself.
• The complaint alleges Defendant targets U.S. consumers through a "fully interactive online retail store" on Amazon, where it offers for sale, sells, and ships the Accused Products (Compl. ¶4, ¶22).
• No probative visual evidence provided in complaint.

IV. Analysis of Infringement Allegations

The complaint alleges that the Accused Products infringe at least Claim 1 of the ’672 Patent, but it does not provide a claim chart or sufficient technical detail in the body of the complaint to construct one, instead referencing an external Exhibit D (Compl. ¶10, ¶20). The narrative infringement theory is that Defendant has "made, used, offered to sell, sold, and/or imported...Accused Products that embody the inventions claimed in the ’672 Patent" (Compl. ¶27).

• Identified Points of Contention:
  • Evidentiary Question: A primary issue will be establishing the precise design and functionality of the circuitry within the Accused Products. The complaint's allegations are conclusory, and the case will depend on evidence produced during discovery that details the accused circuit's components and operation.
  • Technical Questions: The infringement analysis will raise the question of whether the Accused Products' circuitry contains all elements of Claim 1. Specifically, it will require determining if the products employ both a PTC heating element and a distinct NTC element with an associated "sensing element" that generates a "leakage current," as required by the claim. A further question is whether the accused controller monitors two separate voltage signals corresponding to the claimed "first temperature voltage" and "second temperature voltage."

V. Key Claim Terms for Construction

• The Term: "a first temperature voltage based on a ground current" and "a second temperature voltage based on the leakage current" (Claim 1)
• Context and Importance: The invention's novelty appears to derive from its dual-mode sensing capability, which relies on two distinct electrical phenomena: the main "ground current" of the heating element and a separate "leakage current" through a sensor. The definitions of these terms and the relationship between them are central to the claim scope and will be critical for determining infringement. Practitioners may focus on whether the accused device uses two functionally distinct signals for temperature control and fault detection that map onto these claimed elements.
• Intrinsic Evidence for Interpretation:
  • Evidence for a Broader Interpretation: The parties may argue that "ground current" and "leakage current" should be interpreted functionally to cover any two distinct electrical signals that provide information about the PTC element's operational state and the NTC element's temperature reading, respectively, regardless of the precise circuit topology.
  • Evidence for a Narrower Interpretation: The specification distinguishes between the two signals by tying them to specific components. The "first temperature voltage" is sampled from the circuit path including the PTC element 10 and the first switching element 11 (’672 Patent, col. 5:17-19). The "second temperature voltage" is explicitly derived from the NTC element 13 and sensing element 14, which creates a separate path for the "leakage current" (’672 Patent, col. 7:41-47). This detailed description could support a narrower construction requiring two physically and functionally distinct measurement circuits as depicted in the patent's figures.

VI. Other Allegations

• Indirect Infringement: The complaint makes a conclusory allegation that Defendant's activities "may also constitute indirect infringement" (Compl. ¶28). However, it does not plead specific facts to support the required elements of knowledge and intent, such as referencing user manuals, product instructions, or advertisements that would encourage an infringing use.
• Willful Infringement: The complaint alleges infringement is "willful and deliberate" (Compl. ¶30). The basis for this allegation is Defendant's "anonymity and continued sales of the Accused Products despite Plaintiff's patent rights" (Compl. ¶30). This suggests a theory based on alleged efforts to conceal identity rather than pre-suit knowledge of the patent.

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

This case appears to be in its earliest stages, with the complaint providing a high-level notice of infringement. The litigation will likely center on the following core questions:

• An Evidentiary Question of Circuit Design: The central factual dispute will be the actual circuit architecture of the Accused Products. The case hinges on whether discovery reveals a design that incorporates the specific dual-sensing system of the ’672 Patent, including distinct PTC and NTC elements whose states are monitored via two separate voltage acquisition circuits.
• A Definitional Question of Claim Scope: A key legal issue will be the construction of the claim terms distinguishing the "first temperature voltage based on a ground current" from the "second temperature voltage based on the leakage current." The outcome of this construction will determine whether a broad functional interpretation is permissible or if infringement requires a circuit that closely mirrors the specific embodiments and dual-path topology described in the patent.