DCT
2:21-cv-05756
Chengdu Monolithic Power Systems Co Ltd v. Baseus Accessories LLC
Key Events
Complaint
I. Executive Summary and Procedural Information
- Parties & Counsel:
- Plaintiff: Monolithic Power Systems, Inc. (Delaware) and Chengdu Monolithic Power Systems Co., Ltd. (China)
- Defendant: Baseus Accessories LLC (Ohio)
- Plaintiff’s Counsel: Perkins Coie LLP
- Case Identification: 2:21-cv-05756, S.D. Ohio, 12/13/2021
- Venue Allegations: Venue is alleged to be proper in the Southern District of Ohio because Defendant is an Ohio limited liability company with its principal place of business in Hilliard, Ohio, which is located within the district.
- Core Dispute: Plaintiff alleges that Defendant’s USB chargers, which incorporate synchronous rectifier components, infringe two patents related to control circuits that improve the efficiency and reliability of power conversion.
- Technical Context: The technology at issue involves synchronous rectifiers, a type of semiconductor component used in modern AC/DC power converters (such as chargers and power adapters) to increase energy efficiency compared to traditional diodes.
- Key Procedural History: The complaint notes a parallel lawsuit in the Western District of Texas against the component manufacturer, Meraki Integrated Circuit, founded by former employees of the Plaintiff. Defendant Baseus Accessories was previously named in that Texas action but was voluntarily dismissed, leading to the filing of this separate complaint in Defendant’s home district. The complaint alleges Defendant was on notice of the asserted patents at least as of August 30, 2021, due to a subpoena served in the Texas litigation.
Case Timeline
| Date | Event |
|---|---|
| 2009-06-25 | ’790 Patent Priority Date |
| 2013-03-19 | ’790 Patent Issue Date |
| 2017-04-20 | Meraki (component supplier) allegedly founded |
| 2017-07-11 | ’104 Patent Priority Date |
| 2019-10-01 | ’104 Patent Issue Date |
| 2021-04-01 | Approx. date of alleged infringing sale by Defendant |
| 2021-08-30 | Defendant allegedly received notice of patents via subpoena |
| 2021-12-13 | Complaint Filing Date |
II. Technology and Patent(s)-in-Suit Analysis
U.S. Patent No. 8,400,790 - "Latch-Off of Real Time Synchronous Rectification for Light Load Control," issued March 19, 2013
The Invention Explained
- Problem Addressed: The patent describes that while synchronous rectifiers are more efficient than diodes, the power saved can be less than the power consumed by the rectifier's own driver circuit, especially under light load conditions. Furthermore, conventional methods for switching between rectification modes can be unreliable or slow, reducing overall efficiency. (’790 Patent, col. 1:36-40; col. 2:1-14).
- The Patented Solution: The invention proposes a control circuit that monitors the gate voltage of the synchronous rectifier in real time. After a set blanking period, if the gate voltage falls below a reference level (indicating a light load), the circuit "latches off" the synchronous rectification function for subsequent cycles, causing the system to revert to a more efficient mode for that condition. (’790 Patent, Abstract; col. 3:9-24).
- Technical Importance: This approach provides a more intelligent and adaptive method for managing power converter modes, improving efficiency by disabling power-consuming control circuitry when it is not beneficial. (’790 Patent, col. 1:28-36).
Key Claims at a Glance
- The complaint asserts independent Claim 1 (Compl. ¶95).
- The essential elements of Claim 1 include:
- An apparatus comprising a synchronous rectification circuit and a light load control circuit.
- The light load control circuit receives an input voltage to the synchronous rectifier.
- The circuit selectively latches off synchronous rectification based on that input voltage.
- The input voltage used for this determination is specified as "the gate voltage of the synchronous rectifier."
- The complaint does not explicitly reserve the right to assert dependent claims.
U.S. Patent No. 10,432,104 - "Control Circuit for Synchronous Rectifier and The Method Thereof," issued October 1, 2019
The Invention Explained
- Problem Addressed: The patent identifies a problem in synchronous rectifiers where voltage "ringing" (an oscillation that occurs after the rectifier is turned off) can cause the control circuit to "mis-trigger," turning the rectifier back on at the wrong time. This unintended operation reduces efficiency and can compromise reliability. (’104 Patent, col. 1:43-47).
- The Patented Solution: The invention discloses a control circuit that addresses this by detecting the slew rate (the rate of change) of the voltage across the rectifier, rather than just its absolute level. If the slew rate is below a predetermined threshold—as it would be during a ringing event—the circuit maintains the rectifier in the "off" state, thereby ignoring the ringing and preventing a mis-trigger. (’104 Patent, Abstract; col. 2:27-33). This is implemented using a structure of comparators and a pulse-generating circuit (col. 5:1-20; Fig. 5).
- Technical Importance: This technique improves the robustness of synchronous rectifier controllers, preventing erroneous operation caused by inherent electrical phenomena in switching converters. (’104 Patent, col. 2:27-33).
Key Claims at a Glance
- The complaint asserts independent Claim 3 (Compl. ¶105).
- The essential elements of Claim 3 include:
- A controller for a synchronous rectifier.
- A first comparator comparing the rectifier voltage to a first threshold.
- A second comparator comparing the rectifier voltage to a second threshold.
- A pulse circuit that receives the output from the first comparator and generates a pulse of a preset duration.
- A logic gate that receives the pulse signal and the output from the second comparator to generate an "on control signal."
- The complaint does not explicitly reserve the right to assert dependent claims.
III. The Accused Instrumentality
- Product Identification: The complaint identifies "Baseus-branded products that incorporate the accused Meraki Synchronous Rectifier Products" (Compl. ¶13). A specific example provided is the "Baseus USB-C 100W GaN II Fast Charger," which is alleged to contain the Meraki MK91808 synchronous rectifier controller (Compl. ¶68, 92).
- Functionality and Market Context: The accused products are AC/DC power adapters, specifically USB chargers, designed to power or charge consumer electronic devices (Compl. ¶3). The complaint alleges these products are sold and offered for sale in the United States from Ohio and are designed with prongs that fit U.S. outlets (Compl. ¶14, 96). The internal Meraki MK91808 component is the synchronous rectifier controller alleged to perform the infringing functions (Compl. ¶92-95, 105-109). No probative visual evidence provided in complaint.
IV. Analysis of Infringement Allegations
’790 Patent Infringement Allegations
| Claim Element (from Independent Claim 1) | Alleged Infringing Functionality | Complaint Citation | Patent Citation |
|---|---|---|---|
| a light load control circuit that receives an input voltage | The MK91808 has a light load circuit that receives an input voltage. | ¶94 | col. 6:55-62 |
| selectively latches off synchronous rectification based upon at least said input voltage wherein said input voltage is the gate voltage... | The MK91808 selectively latches off synchronous rectification based on the input voltage being the same as the gate voltage, with a turn-off blanking time applied. | ¶95 | col. 4:9-19 |
- Identified Points of Contention:
- Technical Question: The core of the infringement allegation for the ’790 Patent rests on the assertion that the accused MK91808 chip uses the "gate voltage" to decide when to latch off synchronous rectification (Compl. ¶95). A central question will be whether discovery produces evidence that the accused circuit directly measures or relies on the gate voltage ("VGS"), as specified in the claim, or if it uses a different parameter (e.g., current sensing, drain-source voltage) as a proxy for determining a light-load condition.
’104 Patent Infringement Allegations
| Claim Element (from Independent Claim 3) | Alleged Infringing Functionality | Complaint Citation | Patent Citation |
|---|---|---|---|
| a controller for a synchronous rectifier | The MK91808 is a controller for a synchronous rectifier. | ¶106 | col. 4:1-4 |
| a first comparator having... a second input terminal configured to receive a voltage across the synchronous rectifier...; a second comparator having a first input terminal configured to receive the voltage across the synchronous rectifier... | The MK91808 has at least two comparators, with the first comparing a voltage threshold to the voltage across the rectifier and the second comparing a different threshold to that same voltage. | ¶107 | col. 5:55-67 |
| a pulse circuit having an input terminal configured to receive the first comparison signal... wherein when the first comparison signal flips... the pulse signal has a pulse maintaining a preset time period | The MK91808 has a pulse circuit that receives the output from the first comparator and outputs a pulse signal for a pre-set time period when the first comparator’s output changes. | ¶108 | col. 5:1-12 |
| a first logic gate circuit having a first input terminal configured to receive the pulse signal, a second input terminal configured to receive the second comparison signal, and an output terminal configured to provide an on control signal... | The MK91808 has a logic gate circuit receiving the pulse signal and the output from the second comparator, which provides an on-control signal based on a logic operation between the two signals. | ¶109 | col. 5:12-20 |
- Identified Points of Contention:
- Scope Question: The complaint alleges that the accused MK1808 (a related part) "uses slew rate detection" (Compl. ¶74), which is the problem the ’104 Patent aims to solve. However, the asserted claim (Claim 3) recites a specific circuit structure (two comparators, a pulse circuit, a logic gate) to achieve this result. A key question is whether the accused MK91808's internal circuitry contains this specific claimed structure and operates as claimed, or if it achieves a similar anti-ringing function through a different, non-infringing technical implementation.
V. Key Claim Terms for Construction
The Term: "gate voltage" (’790 Patent, Claim 1)
- Context and Importance: Claim 1 requires the decision to "latch off" synchronous rectification to be based on the "gate voltage." The infringement case depends on proving the accused device uses this specific electrical parameter for its control logic. Practitioners may focus on this term to determine if the claim is limited to direct measurement or allows for proxies.
- Intrinsic Evidence for a Broader Interpretation: The specification consistently uses the term "VGS" (gate-source voltage), which is a standard term of art. A party could argue this encompasses any signal that is directly representative of the gate's state, not just a literal measurement at the pin.
- Intrinsic Evidence for a Narrower Interpretation: The figures and description show a direct connection to the gate terminal (e.g., FIG. 6, terminal VG) for the sensing circuit (U3) that makes the load determination (’790 Patent, col. 6:55-62). A party could argue the claim requires this direct sensing of the gate potential, and that any other method, even if correlated, falls outside the claim's scope.
The Term: "pulse circuit... provid[ing] a pulse signal... maintaining a preset time period" (’104 Patent, Claim 3)
- Context and Importance: This element is central to the claimed invention's method for implementing slew rate detection. The interaction between this timed pulse and the output of the second comparator determines whether the rectifier turns on. The definition of how this circuit must function is critical to the infringement analysis.
- Intrinsic Evidence for a Broader Interpretation: A party could argue that "preset time period" simply means any fixed-duration pulse generated in response to the comparator's output changing state, covering a wide range of timer implementations.
- Intrinsic Evidence for a Narrower Interpretation: The specification describes a specific embodiment where the time period "T1" of the pulse is adjustable via an external component connected to a dedicated terminal ("WD") (’104 Patent, col. 6:40-52, Fig. 7). A party could argue that the term, in the context of the patent, implies an adjustable or specifically configured timer circuit, not just any generic, fixed-duration pulse generator.
VI. Other Allegations
- Indirect Infringement: The complaint alleges induced infringement under 35 U.S.C. § 271(b). It asserts that Defendant encourages infringement by its distributors, resellers, and end-customers through the marketing and sale of the accused chargers in the U.S. market, noting that the products are adapted with U.S. plugs and for U.S. voltages (Compl. ¶96, 110-111).
- Willful Infringement: The complaint alleges willful infringement based on Defendant's knowledge of the asserted patents since "at least the service of subpoenas in the Texas action on Baseus Accessories on August 30, 2021" (Compl. ¶98, 112). It further alleges that Defendant continued to sell the accused products after being named as a defendant in the prior Texas action and after receiving notice of this action, allegedly demonstrating reckless disregard for Plaintiff's patent rights (Compl. ¶99-100, 113-114).
VII. Analyst’s Conclusion: Key Questions for the Case
- A central issue will be one of evidentiary proof: What technical evidence, likely from circuit analysis or discovery from the non-party component supplier (Meraki), will Plaintiff present to demonstrate that the accused MK91808 controller operates in the specific manner required by the asserted claims—namely, using "gate voltage" for light-load detection (’790 patent) and employing the precise structural combination of comparators and timers to implement slew rate detection (’104 patent)?
- The case may also turn on a question of claim construction: How narrowly will the court define "gate voltage" in the ’790 patent? Will the term be limited to a direct electrical measurement, or can it be construed to cover other correlated signals used as a proxy? The answer will determine the scope of infringement.
- Finally, a key theme will be the imputation of intent: To what degree can the complaint's extensive narrative about trade secret theft by the component manufacturer, Meraki, be used to establish that Defendant Baseus Accessories acted with the knowledge and intent required for willful infringement, potentially exposing it to enhanced damages? The link between the supplier's alleged misconduct and the seller's state of mind will be a significant point of contention.