DCT

1:24-cv-00166

Monolithic Power Systems Inc v. Nengda Microelectronics Shenzhen Co Ltd

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I. Executive Summary and Procedural Information

  • Parties & Counsel:
  • Case Identification: 1:24-cv-00166, D. Del., 03/15/2024
  • Venue Allegations: Venue is alleged to be proper because Defendants are foreign corporations subject to venue in any U.S. judicial district and have allegedly committed acts of infringement in Delaware, including through coordination with an affiliated Delaware corporation.
  • Core Dispute: Plaintiff alleges that Defendant’s step-down power converter products infringe patents related to power conversion control circuits.
  • Technical Context: The technology relates to semiconductor power management circuits, which are fundamental components for regulating power in a vast range of modern electronic devices.
  • Key Procedural History: The complaint alleges that Defendants are affiliated with Reed Semiconductor Corp., a company Plaintiff has previously sued for infringement of the same patents-in-suit. This alleged affiliation, which includes overlapping corporate leadership, is cited as a basis for Defendants' pre-suit knowledge of the patents.

Case Timeline

Date Event
2011-06-30 '377 Patent Priority Date
2014-08-11 '608 Patent Priority Date
2015-05-26 '377 Patent Issue Date
2017-03-07 '608 Patent Issue Date
2024-01-29 Plaintiff's counsel allegedly emailed Reed's counsel identifying the '377 Patent and providing a draft complaint
2024-03-14 Date of referenced product webpage comparisons between Defendant and Reed Semiconductor
2024-03-15 Complaint Filing Date

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

U.S. Patent No. 9,590,608 - Bootstrap Refresh Control Circuit, Voltage Converter and Associated Method

The Invention Explained

  • Problem Addressed: In certain operating conditions, such as light load or near 100% duty cycle, the "bootstrap capacitor" that supplies voltage to drive a key switch in a power converter may not be recharged in a timely manner. This can cause the bootstrap voltage to drop, leading to improper operation, inefficiency, or failure of the converter (Compl. ¶11; ’608 Patent, col. 2:56-col. 3:14).
  • The Patented Solution: The invention is a control circuit that continuously monitors the bootstrap voltage. If this voltage falls below a predetermined "bootstrap refresh threshold," the circuit intervenes by actively decreasing the converter's main output voltage. This action forces the converter's high-side and low-side switches to resume cycling, which in turn recharges the bootstrap capacitor and restores the necessary operating voltage, thereby ensuring stable operation ('608 Patent, Abstract; col. 4:6-15).
  • Technical Importance: This control method provides a proactive solution to a known failure mode in switch-mode power converters, enhancing their reliability and operational robustness without requiring significant architectural changes ('608 Patent, col. 3:15-20).

Key Claims at a Glance

  • The complaint asserts infringement of "at least one claim" of the '608 Patent (Compl. ¶50). Independent claims include 1, 6, 7, 8, 11, and 12.
  • Independent claim 1, an apparatus claim, includes the following essential elements:
    • A bootstrap refresh module comprising a first comparing module and a voltage difference module.
    • The bootstrap refresh module is configured to decrease the output voltage of the voltage converter when a first comparing signal indicates the bootstrap voltage is below a refresh threshold.
    • The bootstrap refresh control circuit is configured to control the high-side and low-side switches to charge the bootstrap capacitor when a feedback signal is smaller than a reference voltage.
  • The complaint does not explicitly reserve the right to assert dependent claims.

U.S. Patent No. 9,041,377 - Pseudo Constant On Time Control Circuit and Step Down Regulator

The Invention Explained

  • Problem Addressed: Conventional pseudo constant on-time (PCOT) step-down regulators often required dedicated external pins on the integrated circuit to sense the output voltage and set the operating frequency. These extra pins and associated external components increase the circuit's physical size and overall cost ('377 Patent, col. 2:11-20).
  • The Patented Solution: The patent describes a PCOT control circuit that eliminates the need for these dedicated pins. It achieves this with an "on-time generator" that derives the necessary timing information by sensing signals already available within the circuit, such as the main switching signal and a feedback signal. This allows for a more integrated, compact, and cost-effective regulator design ('377 Patent, Abstract; col. 7:51-64).
  • Technical Importance: By reducing pin count and the need for external components, this invention enables the creation of smaller and cheaper power management integrated circuits, a key factor in the design of compact consumer electronics ('377 Patent, col. 7:15-18).

Key Claims at a Glance

  • The complaint asserts infringement of "at least one claim" of the '377 Patent (Compl. ¶60). Independent claims include 1, 11, and 18.
  • Independent claim 1, an apparatus claim, includes the following essential elements:
    • A pseudo constant on time control circuit comprising an on-time generator, a feedback control circuit, a logic control circuit, and a power stage.
    • The on-time generator itself comprises an input voltage sensing circuit, an output voltage sensing circuit, and a comparator.
    • The input voltage sensing circuit generates a signal based on a switching signal and a control signal.
    • The output voltage sensing circuit generates a signal based on the switching signal.
  • The complaint does not explicitly reserve the right to assert dependent claims.

III. The Accused Instrumentality

  • Product Identification: The "Accused Products" are identified as step-down converter products designed and sold by Defendants, with the RS53317 and RS53319 sync step-down converters cited as exemplary products (Compl. ¶¶25, 44-45). The allegations also extend to evaluation boards containing these products (Compl. ¶25).
  • Functionality and Market Context: The Accused Products are power converters incorporated into end-user electronic devices (Compl. ¶25). The complaint alleges these products are part of a supply chain involving contract manufacturers like Accton and Foxconn, who build products for U.S. companies including Microsoft, Meta, and HPE Aruba Networking (Compl. ¶¶30, 34-35). Defendants are alleged to compete directly with Plaintiff and to actively assist customers with the "design in" process for these components (Compl. ¶¶3, 9). The complaint provides a visual comparison of Defendant's RS53317 product and a corresponding product from Reed Semiconductor, alleging they are identical apart from branding (Compl. p. 10).

IV. Analysis of Infringement Allegations

The complaint incorporates by reference Exhibits 3 and 4, which it describes as demonstrating how the Accused Products meet the claim limitations of the ’608 and ’377 Patents, respectively (Compl. ¶¶26-27). As these exhibits were not available for analysis, a claim chart cannot be constructed. The narrative infringement theories are summarized below.

'608 Patent Infringement Allegations

The complaint alleges that the Accused Products, including the exemplary RS53317 converter, directly infringe at least one claim of the ’608 Patent by containing circuitry that performs the claimed bootstrap refresh function (Compl. ¶50). The core of the infringement theory suggests that the accused converters monitor their internal bootstrap voltage and, when it drops too low, execute a refresh cycle consistent with the method described in the patent.

  • Identified Points of Contention:
    • Technical Questions: A central question will be whether the accused products' bootstrap protection mechanism operates by specifically decreasing the output voltage of the converter to force a switching cycle, as required by representative claims of the ’608 Patent. The dispute may turn on evidence of how the accused circuit technically achieves a bootstrap refresh, and whether that mechanism aligns with the claimed solution.

'377 Patent Infringement Allegations

The complaint alleges that the Accused Products, including the exemplary RS53319 converter, directly infringe at least one claim of the ’377 Patent by incorporating a PCOT control circuit that meets the claim limitations (Compl. ¶60). The infringement theory posits that the accused converters use an internal architecture, including an "on-time generator," that senses existing signals to control timing, thereby avoiding the need for the external pins that the patent identifies as a drawback of the prior art.

  • Identified Points of Contention:
    • Scope Questions: The dispute may focus on whether the internal blocks of the accused converters' control circuits correspond to the claimed elements. For example, does the accused circuit contain a distinct "input voltage sensing circuit" and "output voltage sensing circuit" that function in the manner described and claimed in the patent, or is its architecture functionally and structurally different?

V. Key Claim Terms for Construction

For the '608 Patent:

  • The Term: "bootstrap refresh module" (from claim 1)
  • Context and Importance: This term encapsulates the core of the invention. Its construction will be critical to the infringement analysis, as it will define the necessary components and functions a circuit must have to fall within the claim's scope.
  • Intrinsic Evidence for Interpretation:
    • Evidence for a Broader Interpretation: A party might argue the term should be defined functionally, covering any module that "is configured to decrease the output voltage of the voltage converter" when the bootstrap voltage is low to enable a refresh, as described in the patent’s summary ('608 Patent, col. 4:6-10).
    • Evidence for a Narrower Interpretation: The specification discloses specific embodiments of this module, such as the one in Figure 3 comprising a "first comparing module", a "voltage difference module", and a "logic circuit" (36). A party could argue the term should be limited to structures containing these or equivalent components ('608 Patent, col. 10:43-52; Fig. 3).

For the '377 Patent:

  • The Term: "input voltage sensing circuit" (from claim 1)
  • Context and Importance: The patent's advance over the prior art hinges on its method of sensing voltages without dedicated external pins. The definition of this circuit is therefore central to determining whether the accused products, which also lack such pins, practice the claimed invention.
  • Intrinsic Evidence for Interpretation:
    • Evidence for a Broader Interpretation: Claim 1 defines the circuit by its inputs ("receive a switching signal...and...a control signal") and its output ("generates an input voltage sensing signal"). An argument could be made that any circuit performing this transformation falls within the scope ('377 Patent, col. 10:40-49).
    • Evidence for a Narrower Interpretation: The patent describes a specific embodiment of this circuit comprising a resistor ("RTON"), a capacitor ("CTON"), and a switch ("K") ('377 Patent, col. 5:15-26; Fig. 4). A party may argue the term should be construed to require this RC-based structure or a close structural equivalent.

VI. Other Allegations

  • Indirect Infringement: The complaint alleges both induced and contributory infringement. The allegations are based on Defendants providing datasheets, technical materials, and direct customer support that allegedly instruct and encourage customers to incorporate the Accused Products into larger systems in an infringing manner (Compl. ¶¶53, 63). It is further alleged that the products are not staple articles of commerce suitable for substantial non-infringing use (Compl. ¶¶54, 64).
  • Willful Infringement: Willfulness is alleged based on both pre-suit and post-suit knowledge. Pre-suit knowledge is primarily based on Defendants' alleged status as an "active competitor" and, more specifically, on their alleged affiliation with Reed Semiconductor, a company previously sued by Plaintiff on the same patents. The complaint alleges overlapping leadership between the companies and points to a January 29, 2024 email to Reed's counsel as evidence of knowledge (Compl. ¶¶36-39). Post-suit knowledge is alleged from the filing of the complaint (Compl. ¶42). The complaint provides visual evidence comparing Defendant's and Reed's products to support the affiliation claim (Compl. p. 10-11).

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

  • A central threshold issue will be one of knowledge imputation: Can Plaintiff successfully establish that the alleged corporate affiliations and leadership overlap between Defendants and the previously sued entity, Reed Semiconductor, are sufficient to impute pre-suit knowledge of the patents, a key predicate for the willfulness claim?
  • A key technical question for the '608 Patent will be one of operational mechanism: Does the accused converters' bootstrap protection circuitry function by actively decreasing the main output voltage to force a refresh cycle, as required by the patent's claims, or does it employ a different, non-infringing technical method to maintain the bootstrap voltage?
  • For the '377 Patent, a primary dispute will be one of structural correspondence: Does the internal architecture of the accused converters map onto the specific combination of elements claimed, particularly the "on-time generator" with its distinct "input voltage sensing" and "output voltage sensing" sub-circuits, or is there a fundamental mismatch between the claimed structure and the accused design?