DCT
1:19-cv-02240
Volterra Semiconductor LLC v. Monolithic Power Systems Inc
Key Events
Amended Complaint
I. Executive Summary and Procedural Information
- Parties & Counsel:
- Plaintiff: Volterra Semiconductor LLC (Delaware)
- Defendant: Monolithic Power Systems, Inc. (Delaware)
- Plaintiff’s Counsel: Fish & Richardson P.C.
- Case Identification: 1:19-cv-02240, D. Del., 02/12/2020
- Venue Allegations: Venue is alleged to be proper in the District of Delaware because the Defendant is a Delaware corporation and therefore resides in the district.
- Core Dispute: Plaintiff alleges that Defendant’s DC-to-DC power converters infringe three patents related to the structure and operation of voltage converters with coupled inductive windings.
- Technical Context: The technology concerns high-performance, multi-phase DC-to-DC power converters, which are critical components for powering modern high-current electronics such as CPUs and SoCs in the enterprise, cloud computing, and networking markets.
- Key Procedural History: The complaint is a First Amended Complaint. It alleges that the Defendant gained knowledge of the asserted patents at least by the filing of the original complaint on December 9, 2019, which forms the basis for allegations of ongoing willful infringement.
Case Timeline
| Date | Event |
|---|---|
| 2001-03-22 | ’986 Patent Priority Date (Filing Date) |
| 2002-03-26 | ’986 Patent Issue Date |
| 2002-12-13 | ’408 and ’955 Patents Priority Date (Filing Date of Parent) |
| 2009-04-28 | ’408 Patent Issue Date |
| 2010-08-10 | ’955 Patent Issue Date |
| 2019-03-17 | Accused Product demonstrated at APEC 2019 |
| 2019-12-09 | Original Complaint Filing Date |
| 2020-02-12 | First Amended Complaint Filing Date |
II. Technology and Patent(s)-in-Suit Analysis
U.S. Patent No. 6,362,986 - “Voltage converter with coupled inductive windings, and associated methods,” issued March 26, 2002
The Invention Explained
- Problem Addressed: The patent’s background section describes a conflict in designing prior art DC-to-DC converters: small inductance is needed for fast transient response to load changes, but large inductance is needed for reducing AC current ripple and improving efficiency (’986 Patent, col. 1:44-48).
- The Patented Solution: The invention proposes using two or more inductive windings on a single, common magnetic core. By winding them in the same orientation to maximize magnetic coupling and switching them approximately 180 degrees out of phase, the converter can achieve ripple current cancellation within the windings themselves, not just at the output capacitor (’986 Patent, Abstract; col. 2:19-34). This allows for the use of smaller inductors, improving transient response without the penalty of increased ripple current.
- Technical Importance: This approach enabled the development of smaller, more efficient, and higher-performance power converters required by modern microprocessors that demand high currents and have fast-changing loads (Compl. ¶13).
Key Claims at a Glance
- The complaint asserts independent method claim 17 and dependent claims 18, 20, 21, and 23 (Compl. ¶22).
- Independent Claim 17 requires:
- A method for reducing ripple in a DC-to-DC converter of the type producing an output voltage from an input voltage, comprising the steps of:
- orienting, in like direction, first and second windings about a common core to increase coupling between the windings; and
- alternatively activating the first winding about 180 degrees out of phase with the second winding, to regulate magnitude of the output voltage.
U.S. Patent No. 7,525,408 - “Method for making magnetic components with N-phase coupling, and related inductor structures,” issued April 28, 2009
The Invention Explained
- Problem Addressed: The patent addresses the need for practical, scalable, and manufacturable physical structures for the coupled inductors described in the ’986 Patent, particularly for converters with more than two phases (N>2) (’408 Patent, col. 2:12-16).
- The Patented Solution: The patent discloses a physical structure for an N-phase coupled inductor. The core concept is a magnetic core constructed from a first and second parallel magnetic element, which are bridged by N "connecting magnetic elements." This arrangement forms N-1 "passageways." N corresponding windings are wound around the connecting elements and through these passageways, creating an integrated, scalable magnetic component (’408 Patent, Abstract; Fig. 6).
- Technical Importance: The invention provides a modular and scalable physical architecture for coupled inductors, facilitating their implementation in high-phase-count power converters for high-performance computing applications (Compl. ¶13).
Key Claims at a Glance
- The complaint asserts independent apparatus claim 14 and dependent claim 20 (Compl. ¶44).
- Independent Claim 14 requires:
- An N-phase coupled inductor for magnetically coupling N phases of a power converter, comprising:
- a magnetic core including a first and a second magnetic element and N connecting magnetic elements, N being an integer greater than one;
- the first and second magnetic elements being disposed parallel to each other and separated by a linear separation distance;
- the N connecting elements cooperatively forming N-1 passageways; and
- N windings, each wound about a respective connecting element and at least partially through at least one passageway, where each passageway has two of the N windings wound at least partially therethrough.
Multi-Patent Capsule: U.S. Patent No. 7,772,955
- Patent Identification: U.S. Patent No. 7,772,955, “Method for making magnetic components with N-phase coupling, and related inductor structures,” issued August 10, 2010.
- Technology Synopsis: The ’955 Patent, which shares a specification with the ’408 Patent, further details the physical construction of coupled inductors. It claims specific geometric and material properties, such as requiring the separation distance between windings to be greater than the height of the passageway they traverse, and ensuring the cross-sectional area of the passageway between the windings is at least 50% free of magnetic material, which helps to control the inductor's magnetic properties (’955 Patent, Claim 12).
- Asserted Claims: The complaint asserts independent claims 12, 16, and 23, as well as numerous dependent claims (Compl. ¶62).
- Accused Features: The allegations target the same "Modular Dual-phase Buck with Coupled Inductor" stage of the accused power converter, focusing on its physical dimensions and construction (Compl. ¶¶68-70, 78-82, 94-100).
III. The Accused Instrumentality
- Product Identification: The accused products are Defendant’s DC-to-DC power converters, with a non-exhaustive example being the "48V-1V Power Solution for CPU, SoC or ASIC Controller" that was demonstrated at the 2019 IEEE Applied Power Electronics Conference and Exposition (“APEC 2019”) (Compl. ¶18).
- Functionality and Market Context: The accused product is alleged to be a two-stage power converter that transforms a 48V input to a ~1V output suitable for powering high-performance processors (Compl. ¶28, Fig. at p. 8). The complaint's allegations focus on the second stage, described as a "Modular Dual-phase Buck with Coupled Inductor" (Compl. ¶30). This stage allegedly uses multiple 2-phase coupled inductors to form a higher phase-count converter (e.g., 8 or 10 phases) capable of delivering high current (e.g., 600A) to a load (Compl. ¶¶30, 50). The complaint includes a diagram from a marketing presentation illustrating this two-stage structure (Compl., Fig. at p. 8). These products are positioned for high-performance markets such as enterprise computing, communications, and networking (Compl. ¶13).
IV. Analysis of Infringement Allegations
U.S. Patent No. 6,362,986 Infringement Allegations
| Claim Element (from Independent Claim 17) | Alleged Infringing Functionality | Complaint Citation | Patent Citation |
|---|---|---|---|
| orienting, in like direction, first and second windings about a common core to increase coupling between the windings; | The Accused Products allegedly include coupled inductors, where each inductor contains first and second inductive windings oriented in a like direction around a shared magnetic core. | ¶29 | col. 2:19-24 |
| and alternatively activating the first winding about 180 degrees out of phase with the second winding... | The Accused Products allegedly use a pair of control circuits for each inductor. The complaint asserts that the physical orientation of these circuits relative to each other indicates that the first winding is switched about 180 degrees out of phase with the second winding. The complaint includes an annotated diagram illustrating the "first control circuit" and "second control circuit" (Compl., Fig. at p. 10). | ¶30 | col. 2:5-9 |
U.S. Patent No. 7,525,408 Infringement Allegations
| Claim Element (from Independent Claim 14) | Alleged Infringing Functionality | Complaint Citation | Patent Citation |
|---|---|---|---|
| a magnetic core including a first and a second magnetic element and N connecting magnetic elements, N being an integer greater than one | Each 2-phase coupled inductor in the accused product allegedly includes a magnetic core with a first magnetic element, a second magnetic element, and two (N=2) connecting magnetic elements. An annotated diagram is provided to identify these elements (Compl., Fig. at p. 26). | ¶51 | col. 4:47-51 |
| the first and second magnetic elements being disposed parallel to each other...the N connecting elements cooperatively forming N-1 passageways | The first and second magnetic elements are allegedly parallel, and with the two connecting elements, they form a single (N-1 = 1) passageway. | ¶51 | col. 4:51-57 |
| and N windings, each of the N windings...each winding being wound about a respective connecting element and at least partially through at least one passageway | The accused 2-phase inductors allegedly have two windings. The first winding is wound around the first connecting magnetic element and through the passageway, and the second winding is wound around the second connecting magnetic element and through the passageway. | ¶53 | col. 4:59-64 |
| and each passageway having two of the N windings wound at least partially therethrough. | The single passageway in each accused 2-phase inductor allegedly has both the first and second windings wound through it. A visual from the complaint shows the first and second windings passing through this common channel (Compl., Fig. at p. 31). | ¶54 | col. 4:64-67 |
- Identified Points of Contention:
- Evidentiary Question (’986 Patent): The complaint primarily relies on the physical layout of control circuits, as shown in marketing materials, to support the functional limitation of "alternatively activating the first winding about 180 degrees out of phase with the second winding" (Compl. ¶30). The analysis may raise the question of whether this physical arrangement is sufficient evidence of the specific electrical switching method required by the claim.
- Scope Question (’408 Patent): Claim 14 recites "An N-phase coupled inductor" with "N connecting magnetic elements." The complaint alleges infringement by a system that achieves N>2 phases (e.g., 8 or 10) by combining multiple discrete 2-phase (N=2) inductors (Compl. ¶50). This raises the question of whether the claim term "An N-phase coupled inductor" can be construed to cover an assembly of multiple, separate inductors with a lower phase count, or if it is limited to a single, monolithic magnetic structure with N phases.
V. Key Claim Terms for Construction
- The Term: "An N-phase coupled inductor" (’408 Patent, Claim 14)
- Context and Importance: The construction of this term is central to the infringement analysis for the ’408 patent. The accused instrumentality is an 8- or 10-phase converter allegedly built from multiple 2-phase inductor components. Whether this system constitutes "An N-phase coupled inductor" will be a critical point of dispute.
- Intrinsic Evidence for Interpretation:
- Evidence for a Broader Interpretation: The specification emphasizes the scalability of the invention, stating that a goal is to provide a "scalable and cost effective DC-to-DC converter" (’408 Patent, col. 3:6-7). Practitioners may argue that building a higher-phase system from modular, lower-phase components is a form of scalability consistent with the patent's teachings.
- Evidence for a Narrower Interpretation: The claim language recites a single "magnetic core" that includes "N connecting magnetic elements" and forms "N-1 passageways." This suggests a unitary, monolithic structure. Figures such as Fig. 6 and Fig. 7 depict single, integrated magnetic cores with N>2 phases, which could be used to argue that the claim is limited to such a singular structure and does not cover an assembly of separate components.
VI. Other Allegations
- Indirect Infringement: The complaint alleges both induced and contributory infringement. Inducement allegations are based on Defendant's alleged promotion of the Accused Products through marketing materials, its YouTube channel, trade shows, and customer support activities that allegedly encourage infringing uses (Compl. ¶¶24, 46, 64). Contributory infringement is alleged on the basis that Defendant supplies a component (the converter) that is a material part of the patented invention and is especially adapted for an infringing use (Compl. ¶¶25, 47, 65).
- Willful Infringement: Willfulness allegations are based on Defendant's alleged knowledge of the patents as of at least December 9, 2019, the filing date of the original complaint (Compl. ¶¶23, 45, 63). The complaint does not allege pre-suit knowledge of the patents.
VII. Analyst’s Conclusion: Key Questions for the Case
- A core issue will be one of structural scope: can the term "An N-phase coupled inductor" from the ’408 patent, which is described in the patent as a unitary structure, be construed to read on a system that achieves N-phase operation by assembling multiple, discrete 2-phase inductor components?
- A key evidentiary question will be one of functional proof: does the physical orientation of control circuits, as depicted in marketing materials, provide sufficient factual support to establish the specific electrical method of "alternatively activating" the windings "about 180 degrees out of phase" as required by the ’986 patent?