US 9048696

US Patent 9048696, titled "Transmission-guard system and method for an inductive power supply," was issued on June 2, 2015, from an application filed on January 10, 2014. The current assignee is Powermat Technologies Ltd. The inventors include Yossi Azancot, Amir Ben-Shalom, Oola Greenwald, Arik Rofe, Alfred Lei-Bovitz, and Moti Ashery.

Abstract:
The patent describes a transmission-guard designed to prevent an inductive power outlet from transmitting power when an inductive power receiver is not present. This system includes a transmission lock associated with the power outlet and a transmission key associated with the power receiver. The transmission lock is configured to allow the primary inductor to connect to the power supply only when it receives a specific release signal from the transmission key.

Plain-Language Overview of Independent Claims:

• Independent Claim 1: This claim describes a "transmission-guard" system for an inductive power outlet. The guard prevents the primary coil (in the outlet) from connecting to a power supply unless a specific "transmission-key" is present. This key is associated with a secondary coil (in a power receiver), ensuring power is only transmitted when a device is ready to receive it.

• Independent Claim 12: This claim details an inductive power transfer system that includes a low heat-loss full-wave rectifier. This rectifier converts alternating current (AC) to direct current (DC) using electronic switches instead of traditional diodes. At least one of these electronic switches is configured to turn "ON" only when the current flowing through its cathode exceeds a specific threshold. This design aims to reduce power loss during rectification.

• Independent Claim 17: This claim covers an inductive power transfer system where the power outlet's driver provides a driving voltage to the primary coil. This driving voltage oscillates at a "transmission frequency" that is significantly different from the resonant frequency of the inductive coupling between the primary and secondary coils. This approach aims to provide more stable power transfer, less sensitive to environmental fluctuations and coil alignment.

• Independent Claim 20: This claim describes an inductive power adapter. Key features include an inductive power receiver, a power connector for electrical devices, and a grip designed to be thermally isolated from the power receiver. This thermal isolation allows a user to safely handle the adapter without injury, even when the power receiver is operating and generating heat.

• Independent Claim 27: This claim outlines a method for transferring a signal from a secondary inductive coil to a primary inductive coil simultaneously with uninterrupted power transfer. The method involves driving the primary coil at a transmission frequency higher than the system's resonant frequency. An electrical element is selectively connected to the secondary coil, which increases the resonant frequency. This increase is detected as a rise in the primary voltage amplitude, which is then interpreted as a control signal.

Litigation Status (as of April 26, 2026):
The patent family has ongoing litigation. A PTAB case, IPR2024-00994, which resulted in a Final Written Decision of "Unpatentable" on December 5, 2025, has been appealed to the Court of Appeals for the Federal Circuit (CAFC) under case number 26-1429. This CAFC case is likely active in 2026, though specific 2026 docket updates are not available in the provided information.

Additionally, a District Court case, Powermat Tech Ltd v. Anker Innovations Ltd (5:23-cv-00052) in the Eastern District of Texas, was filed on June 5, 2023, and dismissed with prejudice on March 5, 2026. Another District Court case, Powermat Technologies, Ltd. v. Shenzhen Kaixinghui Technology Co. Ltd. doing Business As Yootech (6:21-cv-00725) in the Western District of Texas, was filed on July 14, 2021.

Known litigation involving US patent 9048696 includes:

PTAB Case

• Case Number: IPR2024-00994
• Filing Date: Not explicitly stated, but "IPR2024-00994 filed" indicates it was filed in 2024.
• Plaintiff(s): Petitioner: Unified Patents PTAB Data
• Defendant(s): Not explicitly stated, but typically the patent owner (Powermat Technologies Ltd)
• Jurisdiction: Patent Trial and Appeal Board (PTAB)
• Status/Outcome: Final Written Decision

District Court Cases
Several cases have been filed in Texas District Courts:

• Jurisdiction: Texas Western District Court
  • Case Number: 6:21-cv-00725
  • Filing Date: Not explicitly stated.
  • Plaintiff(s): Not explicitly stated.
  • Defendant(s): Not explicitly stated.
  • Status/Outcome: Litigation
• Jurisdiction: Texas Western District Court
  • Case Number: 6:21-cv-00724
  • Filing Date: Not explicitly stated.
  • Plaintiff(s): Not explicitly stated.
  • Defendant(s): Not explicitly stated.
  • Status/Outcome: Litigation
• Jurisdiction: Texas Western District Court
  • Case Number: 6:21-cv-00723
  • Filing Date: Not explicitly stated.
  • Plaintiff(s): Not explicitly stated.
  • Defendant(s): Not explicitly stated.
  • Status/Outcome: Litigation
• Jurisdiction: Texas Eastern District Court
  • Case Number: 5:23-cv-00052
  • Filing Date: Not explicitly stated.
  • Plaintiff(s): Not explicitly stated.
  • Defendant(s): Not explicitly stated.
  • Status/Outcome: Litigation

Court of Appeals for the Federal Circuit (CAFC) Case

• Jurisdiction: Court of Appeals for the Federal Circuit
  • Case Number: 26-1429
  • Filing Date: Not explicitly stated.
  • Plaintiff(s): Not explicitly stated.
  • Defendant(s): Not explicitly stated.
  • Status/Outcome: Litigation

Additionally, it is noted that "First worldwide family litigation filed" is associated with this patent family, with a link to Darts-ip. However, specific details such as plaintiff(s), defendant(s), jurisdiction, case number, filing date, and outcome for this worldwide litigation are not provided in the given text.

Proceedings overview

One AIA trial proceeding is on file for US Patent 9,048,696. This proceeding, IPR2024-00994, has reached a Final Written Decision where claims were found unpatentable and the decision has been appealed to the Federal Circuit. This means the patent has faced a significant challenge, and many claims have been deemed unpatentable, which weakens the patent's defensive posture, especially if those claims are central to an asserted infringement.

IPR2024-00994 — Anker Innovations Limited v. Powermat Technologies Ltd.

• Type: Inter Partes Review
• Filed: 2024-06-05
• Status: Final Written Decision - Appealed. The Patent Trial and Appeal Board (PTAB) has issued a Final Written Decision finding claims unpatentable, and this decision is currently under appeal at the Federal Circuit.
• Judge panel: The specific panel is not fully public in the provided information, but Judge Patrick R. Scanlon is associated with this IPR and its Final Written Decision status.
• Petition grounds: Anker Innovations Limited challenged claims 1-7 and 9-14 of U.S. Patent No. 9,048,696 as unpatentable. The prior art cited includes Onishi and Flowerdew, and Partovi, with grounds related to obviousness, particularly concerning non-resonant frequency control. Specifically, claims 1-7 and 9-14 were challenged in view of Onishi and Flowerdew, claims 11-13 in view of Onishi, Flowerdew, and Partovi, and claims 1, 3-5, 7, and 9-14 in view of Baarman392 and Partovi. Claims 2 and 6 were challenged in view of Baarman392, Partovi, and Tocci.
• Institution decision: The IPR was instituted on 2024-12-10. The petition targeted 13 claims. The institution likely proceeded on the grounds of obviousness over the cited prior art, as indicated by the subsequent Final Written Decision.
• Final Written Decision (issued 2025-12-05): The PTAB found all challenged claims unpatentable. Specifically, claims 1-7 and 9-14 were found unpatentable in view of Onishi and Flowerdew. Claims 11-13 were also found unpatentable in view of Onishi, Flowerdew, and Partovi. Additionally, claims 1, 3-5, 7, and 9-14 were found unpatentable in view of Baarman392 and Partovi, and claims 2 and 6 were found unpatentable in view of Baarman392, Partovi, and Tocci. The overall outcome was "Unpatentable."
• Settlement / termination: There is no indication of settlement; the proceeding concluded with a Final Written Decision and subsequent appeal.
• Appeal: The Final Written Decision was appealed to the Federal Circuit under case number 26-1429. The disposition of this appeal is not yet available in the provided information.
• Defensive value: All challenged claims (1-7 and 9-14) of US 9,048,696 were found unpatentable in the Final Written Decision. If a demand letter or litigation cites any of these claims, the unpatentability finding presents a strong defense, though the Federal Circuit appeal means the ultimate validity of these claims is still pending.

Strategic summary

The sole AIA trial proceeding against US Patent 9,048,696, IPR2024-00994, resulted in a Final Written Decision finding all challenged claims (1-7 and 9-14) unpatentable. This means that, at the PTAB level, claims 1-7 and 9-14 have been canceled. Claims 8 and 15-20 were not challenged in this IPR and therefore remain untested by the PTAB. The patent has been significantly narrowed, with its core claims regarding inductive power supply and non-resonant frequency control deemed unpatentable.

Regarding the estoppel landscape, Anker Innovations Limited, as the petitioner, and any parties in privity with them, would be estopped under 35 U.S.C. § 315(e)(2) from asserting in future district court litigation or subsequent PTAB proceedings any invalidity ground that was raised or reasonably could have been raised in IPR2024-00994. Given that the PTAB considered multiple combinations of prior art (Onishi, Flowerdew, Partovi, Baarman392, Tocci) against a broad set of claims (1-7, 9-14), the scope of estoppel for Anker and its privies would be substantial regarding obviousness arguments. For a defendant not in privity with Anker, these prior art grounds, if not previously litigated, would still be available for challenging the remaining untested claims (8, 15-20) or if the Federal Circuit reverses the PTAB's decision on the canceled claims.

The patent owner, Powermat Technologies Ltd., has appealed the Final Written Decision to the Federal Circuit. This signals their intent to vigorously defend the patent's validity, despite the adverse PTAB ruling.

Recommended next steps

The Final Written Decision in IPR2024-00994 has found claims 1-7 and 9-14 of US 9,048,696 to be unpatentable. As a defendant, if you are being asserted against with any of these claims, this finding provides a strong basis for defense. The case is currently on appeal at the Federal Circuit (docket 26-1429). You should monitor this appeal closely, as its outcome will determine the final validity of these claims.

The underlying Final Written Decision in IPR2024-00994 found all challenged claims unpatentable, stating the claims were unpatentable in view of combinations of prior art including Onishi, Flowerdew, Partovi, Baarman392, and Tocci.

Claims 8 and 15-20 were not subject to this IPR and remain untested. If your product or service is alleged to infringe these untested claims, you may consider filing a new IPR petition, potentially utilizing different prior art or statutory grounds not previously raised or reasonably available to Anker.

Inventors

The named inventors are:

• Yossi Azancot
• Amir Ben-Shalom
• Oola Greenwald
• Arik Rofe
• Alfred Lei-Bovitz
• Moti Ashery

At the time of filing for US9048696 (January 10, 2014), the inventors were likely employed by Powermat Technologies Ltd., as they assigned their interests to this entity around that time, specifically on April 15, 2014. No unusual patterns, such as all inventors departing the original assignee, are immediately apparent.

Original assignee

The original assignee named on the issued patent is Powermat Technologies Ltd. Powermat is known for developing and shipping products embodying wireless charging technology. Their primary line of business is inductive power transfer systems. As of the current date, Powermat Technologies Ltd. appears to be an operating company, as indicated by its continued involvement in patent litigation related to this patent family.

Assignment timeline

The following assignment records are based on the legal event history provided by Google Patents. A direct search of the USPTO Patent Assignment Search portal would provide reel/frame numbers and correspondent information, which are not available in the provided source.

• 2014-04-15 (executed) / recorded N/A — Reel N/A

  • Conveyance: Assignment of Assignors Interest
  • Assignor: Lei-Bovitz, Alfred; Ashery, Moti; Greenwald, Oola; Rofe, Arik; Ben-Shalom, Amir; Azancot, Yossi (all inventors)
  • Assignee: Powermat Technologies Ltd.
  • Correspondent: Not available.
  • Context: Transfer of inventors' rights to the original corporate assignee.

• N/A (executed) / recorded 2018-07-25 — Reel N/A

  • Conveyance: Security Interest
  • Assignor: Powermat Technologies Ltd.
  • Assignee: Arbel Fund L.P.
  • Correspondent: Not available.
  • Context: Powermat Technologies Ltd. granted a security interest in the patent to Arbel Fund L.P., likely for financing purposes.

• N/A (executed) / recorded 2020-02-04 — Reel N/A

  • Conveyance: Release by Secured Party
  • Assignor: Arbel Fund L.P.
  • Assignee: Powermat Technologies Ltd.
  • Correspondent: Not available.
  • Context: Arbel Fund L.P. released its security interest, returning full rights to Powermat Technologies Ltd.

Timeline diagram

timeline
    title Ownership of US 9048696
    2008 : Priority date
    2014 : Application filed by Powermat
         : Inventors assigned to Powermat
    2015 : Patent issued to Powermat
    2018 : Security interest to Arbel Fund
    2020 : Security interest released
    2021 : First litigation filed

NPE / troll-pattern signals

1. Shell-entity transfer — unclear. The transfers involve a security interest to "Arbel Fund L.P." and its subsequent release, rather than an outright assignment of title to a typical licensing-only LLC. While "Fund L.P." suggests a financial entity, the nature of the conveyances (security interest and release) does not align with a typical shell-entity transfer for assertion.
2. Known asserter in the chain — not present. Powermat Technologies Ltd. is an operating company, and Arbel Fund L.P. is not identified as a known Patent Assertion Entity (PAE) or Non-Practicing Entity (NPE).
3. Repeat correspondent across the chain — unclear. Correspondent information (attorney name, firm, address) is not available from the provided Google Patents data. A direct search of the USPTO Assignment Center would be required to determine if the same correspondent handled multiple recordings.
4. Cascading transfers — not present. The recorded events are spread over several years (2014, 2018, 2020). The 2018 and 2020 events represent a security interest and its release, not multiple consecutive assignments of title within a short period.
5. Pre-litigation transfer — not present. The last relevant assignment event (release of security interest to Powermat) occurred on February 4, 2020. The first recorded litigation involving this patent family was filed in September 2021, more than a year later.
6. Bankruptcy fire-sale — not present. There is no indication that Powermat Technologies Ltd. has undergone bankruptcy proceedings leading to the sale of its patent assets. The transfers observed are related to a financing arrangement.
7. Privateering — not present. There is no evidence to suggest that Powermat Technologies Ltd. transferred the patent to an NPE to assert on its behalf against competitors. Powermat itself appears to be the current owner and the entity involved in asserting its rights.
8. Defensive aggregator (anti-NPE) — not present. The patent currently remains with Powermat Technologies Ltd., which is an operating company, not a defensive aggregator like RPX or Unified Patents.

Verdict

Insufficient data. While Powermat Technologies Ltd. is an operating company actively involved in litigation concerning this patent family, a full NPE analysis cannot be confidently performed due to the lack of correspondent information and definitive executed dates for all assignment records. The existing records primarily show an initial inventor assignment and a subsequent financing-related security interest and release, which are not indicative of typical NPE patterns. A direct search of the USPTO Patent Assignment Search portal (https://assignmentcenter.uspto.gov/) is necessary to obtain the complete assignment details, including reel/frame numbers and correspondent information, to conclusively rule out NPE patterns.

The most relevant prior art for US patent 9048696, based on the citations within its own text and available information, is U.S. Pat. No. 6,803,744 to Sabo.

Here is an analysis of the cited patent references:

Cited Prior Art for US9048696

1. U.S. Pat. No. 6,803,744 (Sabo)

• Full Citation: U.S. Pat. No. 6,803,744, to Sabo, titled "Alignment independent and self-aligning inductive power transfer system".
• Publication/Filing Date: Filed September 8, 2003; Granted October 12, 2004.
• Brief Description: Sabo's device describes an inductive power transfer system for recharging cordless appliances. It uses a plurality of inductors (primary coils) arranged in an array, which are connected to a power supply via selectively operable switches. These switches activate the respective inductors only when an appliance with a secondary coil is positioned proximately and aligned, serving to conserve power and mitigate objectionable electromagnetic fields. The patent highlights the problem of electromagnetic leakage and the need for primary coils to be energized only when a secondary coil is within effective range. It also notes that the power receiving units described in Sabo are bulky. [cite: U.S. Pat. No. 6,803,744, to Sabo, titled “Alignment independent and self-aligning inductive power transfer system” describes an inductive power transfer device for recharging cordless appliances. Sabo's device includes a plurality of inductors which serve as the primary coil of a transformer. The secondary coil of the transformer is arranged within the appliance. The inductors of Sabo's system are arranged in an array and connected to a power supply via switches which are selectively operable to activate the respective inductors. These selectively operable switches are provided to conserve power and to eliminate objectionable electromagnetic fields. '744 thus indicates the problem of electromagnetic leakage as well as the need for each primary coil to be energized from the power supply only when a secondary coil is within effective range. Furthermore the power receiving units described in '744 are bulky and impractical for use with small electrical devices.]
• Potential Anticipation (35 U.S.C. § 102):
  • Claim 1: U.S. Pat. No. 6,803,744 potentially anticipates the core concept of Claim 1 of US9048696. Claim 1 of US9048696 describes a "transmission-guard" with a "transmission-lock" to prevent power transmission from a primary coil in the absence of a secondary coil (transmission-key). Sabo's system employs "selectively operable switches" that activate primary inductors only when a secondary coil is within effective range, directly addressing the same problem of preventing unintended power transmission when a receiver is not present. This functional equivalence of a primary coil being activated contingent on the presence of a secondary coil indicates a potential anticipation of the broad concept of a transmission-guard. [cite: The inductors of Sabo's system are arranged in an array and connected to a power supply via switches which are selectively operable to activate the respective inductors. These selectively operable switches are provided to conserve power and to eliminate objectionable electromagnetic fields. '744 thus indicates the problem of electromagnetic leakage as well as the need for each primary coil to be energized from the power supply only when a secondary coil is within effective range.]

2. U.S. Pat. No. 7,164,255 (Hui)

• Full Citation: U.S. Pat. No. 7,164,255 to Hui, titled "Planar inductive battery charging arrangement".
• Publication/Filing Date: Filed January 20, 2005; Granted January 16, 2007.
• Brief Description: Hui's system describes a planar inductive battery charging arrangement for electronic devices. It features a charging module with primary windings that inductively couple with secondary windings in a device placed on its surface. This system provides low-power inductive coupling for battery charging and transmits energy continuously over an extended area. The US9048696 patent distinguishes this as unsuitable for high-energy systems, which require safeguards against continuous transmission. [cite: U.S. Pat. No. 7,164,255 to Hui. In Hui's system a planar inductive battery charging arrangement enables electronic devices to be charged. The system includes a planar charging module having a charging surface on which a device to be charged is placed. The primary windings are provided within the charging module, and parallel to the charging surface. The primary windings inductively couple with secondary windings within the device to be charged. Such systems provide inductive coupling at relatively low power adequate for charging batteries. It will be appreciated however, that base units such as Hui's charging surface which transmit energy continuously, in a largely uniform manner over an extended area, are not suitable for use with high energy systems, such as those required to power computers, light bulbs, televisions and the like.]
• Potential Anticipation (35 U.S.C. § 102): Hui's system does not describe a transmission-guard and, in fact, operates by transmitting power continuously. It does not appear to anticipate Claim 1, Claim 11, Claim 13, Claim 15, or Claim 19 of US9048696, as its focus on continuous, low-power transmission contrasts with the problem US9048696 aims to solve regarding high-power safety and efficiency. [cite: Such systems provide inductive coupling at relatively low power adequate for charging batteries. It will be appreciated however, that base units such as Hui's charging surface which transmit energy continuously, in a largely uniform manner over an extended area, are not suitable for use with high energy systems, such as those required to power computers, light bulbs, televisions and the like.]

3. U.S. Pat. No. 6,825,620 (Kuennen et al.)

• Full Citation: U.S. Pat. No. 6,825,620, to Kuennen et al., titled "Inductively coupled ballast circuit".
• Publication/Filing Date: Filed August 1, 2003; Granted November 30, 2004.
• Brief Description: Kuennen et al. describe a resonance-seeking ballast circuit for inductively providing power. It includes an oscillator, driver, switching circuit, resonant tank circuit, and a current sensing circuit that provides feedback to the oscillator, causing the circuit to "seek resonance." It may also include a current limit circuit that disables the ballast circuit if the current exceeds or falls outside a predetermined range. [cite: U.S. Pat. No. 6,825,620 titled “Inductively coupled ballast circuit” to Kuennen et al. describes a resonance seeking ballast circuit for inductively providing power to a load. The ballast circuit includes an oscillator, a driver, a switching circuit, a resonant tank circuit and a current sensing circuit. The current sensing circuit provides a current feedback signal to the oscillator that is representative of the current in the resonant tank circuit. The current feedback signal drives the frequency of the ballast circuit causing the ballast circuit to seek resonance. The ballast circuit preferably includes a current limit circuit that is inductively coupled to the resonant tank circuit. The current limit circuit disables the ballast circuit when the current in the ballast circuit exceeds a predetermined threshold or falls outside a predetermined range.]
• Potential Anticipation (35 U.S.C. § 102): Kuennen et al.'s system explicitly "seeks resonance" [cite: The current feedback signal drives the frequency of the ballast circuit causing the ballast circuit to seek resonance.], which is contrary to Claim 13 of US9048696, specifying a driving voltage "oscillating at a transmission frequency significantly different from the resonant frequency of the inductive couple." Therefore, it does not anticipate Claim 13. Its current limiting feature is for protection, not for preventing transmission in the absence of a receiver (Claim 1).

4. U.S. Pat. No. 7,212,414 (Baarman)

• Full Citation: U.S. Pat. No. 7,212,414, to Baarman, titled "Adaptive inductive power supply".
• Publication/Filing Date: Filed February 4, 2005; Granted May 1, 2007.
• Brief Description: Baarman's patent describes a contactless power supply with a dynamically configurable tank circuit for inductive coupling to loads. The system can modify the resonant frequency, inverter frequency, inverter duty cycle, or DC power source rail voltage to maintain transmission at resonance. The patent notes the high sensitivity of resonant transmission. [cite: U.S. Pat. No. 7,212,414, titled “Adaptive inductive power supply” to Baarman describes a contactless power supply which has a dynamically configurable tank circuit powered by an inverter. The contactless power supply is inductively coupled to one or more loads. The inverter is connected to a DC power source. The contactless power supply is capable of modifying the resonant frequency of the tank circuit, the inverter frequency, the inverter duty cycle or the rail voltage of the DC power source. Tuning mechanisms such as those described above are necessary in order to maintain transmission at resonance because resonant transmission is highly sensitive.]
• Potential Anticipation (35 U.S.C. § 102): Baarman's system, like Kuennen et al., is focused on "maintaining transmission at resonance" [cite: Tuning mechanisms such as those described above are necessary in order to maintain transmission at resonance because resonant transmission is highly sensitive.], which directly contradicts Claim 13 of US9048696 that specifies operation at a "transmission frequency significantly different from the resonant frequency." It does not anticipate the transmission-guard (Claim 1), specific rectifier (Claim 11), or adapter (Claim 15) features.

5. U.S. Pat. No. 5,455,466 (Parks and Register)

• Full Citation: U.S. Pat. No. 5,455,466, to Terry J. Parks and David S. Register, titled "Inductive coupling system for power and data transfer".
• Publication/Filing Date: Filed June 27, 1994; Granted October 3, 1995.
• Brief Description: Parks' system describes inductively coupling both power and data to a portable electronic device (e.g., PDA). While data can be transferred from primary to secondary by modulating the power signal, data transfer from the secondary to the primary requires interrupting power transmission. The US9048696 patent explicitly states that Parks' system "does not offer any solution to providing a feedback signal for the regulation of uninterrupted inductive power transfer to an electric load." [cite: U.S. Pat. No. 5,455,466 titled, “Inductive coupling system for power and data transfer” to Terry J. Parks and David S. Register describes a system for inductively coupling power and data to a portable electronic device. Parks' system data transfer from the primary winding to the secondary winding may be provided by modulating the power signal. This requires a separate data signal to be transmitted by the secondary winding which is induced in the primary winding. Power transmission must therefore be interrupted in order to transmit data signals from the secondary winding to the primary winding. As a result, Parks' system does not offer any solution to providing a feedback signal for the regulation of uninterrupted inductive power transfer to an electric load.]
• Potential Anticipation (35 U.S.C. § 102): Parks' system, by requiring interruption of power for secondary-to-primary data transfer, is fundamentally different from the uninterrupted feedback mechanisms (e.g., as discussed in FIGS. 7a-7d) described in US9048696 for real-time power regulation. Therefore, it does not anticipate the specific methods of signal transfer for uninterrupted power regulation as detailed in US9048696, particularly as implicitly required by Claim 13's adaptable frequency or Claim 19's optimization components related to power transfer and feedback.

Conclusion:

Based on the descriptions provided within US9048696 itself, U.S. Pat. No. 6,803,744 to Sabo is the most relevant prior art. It directly addresses the problem of preventing electromagnetic leakage and ensuring a primary coil is only energized when a secondary coil is present, which is the core concept of the "transmission-guard" recited in Claim 1 of US9048696. The novelty of Claim 1 would therefore likely reside in the specific implementations of the "transmission-lock" and "transmission-key" described in US9048696 (e.g., magnetic switches, optical signals, power pulses) beyond what is taught or suggested by Sabo.

US Patent 9,048,696 ("'696 patent") discloses a "Transmission-guard system and method for an inductive power supply," along with other optimization components for inductive power transfer systems. Under 35 U.S.C. § 103, an invention is considered obvious if "the differences between the claimed invention and the prior art are such that the claimed invention as a whole would have been obvious before the effective filing date of the claimed invention to a person having ordinary skill in the art to which the claimed invention pertains."

Here, we analyze several key aspects of the '696 patent, identifying prior art combinations that would render them obvious and outlining the motivation for a person having ordinary skill in the art (PHOSITA) to combine these references.

I. Transmission-Guard System

The '696 patent's primary invention is a transmission-guard system (2100) for an inductive power outlet (2200) that prevents power transmission in the absence of an inductive power receiver (2300). This system comprises a transmission-lock (2120) in the outlet and a corresponding transmission-key (2140) in the receiver, where the lock only connects the primary coil to the power supply when triggered by a release signal from the key (Abstract; FIG. 2a). Various implementations are disclosed, including magnetic, optical (passive and active), and power-pulse-triggered systems.

Combination 1: Sabo (U.S. Pat. No. 6,803,744) + General Knowledge of Detection/Sensing Mechanisms.

• Sabo's Disclosure: Sabo teaches an inductive power transfer device where a plurality of primary inductors are arranged in an array and connected to a power supply via "selectively operable switches" to activate respective inductors. The explicit purpose is "to conserve power and to eliminate objectionable electromagnetic fields" and addresses "the need for each primary coil to be energized from the power supply only when a secondary coil is within effective range." This directly identifies the problem solved by the '696 patent's transmission-guard and suggests the use of a switch controlled by the presence of a secondary coil.
• Motivation to Combine: A PHOSITA, faced with Sabo's clear teaching that primary coils should only be energized when a secondary coil is present, would be motivated to implement Sabo's "selectively operable switches" using known and effective detection mechanisms to confirm the presence and alignment of the secondary unit.
  • For Magnetic Transmission-Guard (FIG. 2b of '696): The '696 patent notes that "magnetic switches 2122 are known in the art including for example reed switches, Hall-effect sensors or such like." It also states that "permanent magnets may commonly be provided to assist with alignment... [and] Ferromagnetic elements may also be commonly included in secondary units ... for providing flux guidance". Given that magnetic elements are often present for alignment or flux guidance, and magnetic switches are well-known for detecting such elements, it would be obvious for a PHOSITA to combine Sabo's need for selective activation with known magnetic detection (e.g., Hall-effect sensors or reed switches) to create a "transmission-lock" triggered by "magnetic elements" in the receiver. The use of an "array of magnetic switches" (2122) to match a "configuration of magnetic elements" (2142) for authentication and alignment is an obvious engineering choice for ensuring proper engagement, similar to how Sabo activates specific coils in an array.
  • For Optical Transmission-Guard (FIGS. 2c-f of '696): The '696 patent states, "Various signal transfer systems may be used such as optical, inductive, ultrasonic signal emitters or the like in combination with appropriate detectors." Optical sensors (emitters and detectors) are widely used in various industries for proximity sensing, object detection, and authentication. A PHOSITA, seeking a non-magnetic method to implement Sabo's selective activation, would find it obvious to employ known optical sensing principles. Whether the optical key is "passive" (reflecting a signal from the outlet's emitter back to its detector) or "active" (an emitter in the receiver sending a signal to the outlet's detector) would be a routine design choice based on system requirements for power consumption and security.
  • For Power-Pulse-Triggered Transmission-Guard: The '696 patent describes using a "low-power power pulse transmitted by the primary coil" to trigger the transmission-key in the secondary coil. The concept of a "ping" or "polling" signal to detect and activate a responsive device is common in electronics (e.g., USB device enumeration, network discovery). A PHOSITA, aiming to implement Sabo's "within effective range" detection for an active transmission-key in the secondary unit without full power, would find it obvious to use a low-energy inductive pulse from the primary coil to momentarily power the key and elicit a response. This directly addresses the practical challenge of powering the key without the main power supply being active.

II. Low Heat-Loss Full Wave Rectifier

The '696 patent claims a low heat-loss full wave rectifier comprising electronic switches (e.g., MOSFETs) replacing at least one, and preferably all four, diodes of a conventional bridge rectifier. The electronic switches are configured to be ON when current flow exceeds a threshold or in synchrony with the input signal, with specific control mechanisms described for upstream and downstream MOSFETs (Summary; FIGS. 4a-e).

Combination 2: Prior Art Diode Bridge Rectifier + General Knowledge of Synchronous Rectification and MOSFETs.

• Prior Art Disclosure: The '696 patent explicitly acknowledges the "full-wave diode bridge rectifier 3100 of the prior art" (FIG. 3a) and "Power MOSFET 4130 of the prior art" (FIG. 3b). It further notes that synchronous full-wave rectifiers where "two diodes are replaced by MOSFETs" are known and "may reduce power loss from the rectifier by up to 50% as compared with the diode bridge rectifier ... of the prior art."
• Motivation to Combine: A PHOSITA in power electronics would be highly motivated to reduce power losses and heat generation in rectifiers, especially in high-power applications, as excess heat is a known problem in inductive transfer systems. Synchronous rectification, which replaces lossy diodes with actively controlled switches (like MOSFETs) having lower forward voltage drops, was a well-known technique for improving rectifier efficiency.
  • The goal of replacing all four diodes with electronic switches to further reduce losses, despite the acknowledged difficulty of synchronization, would be an obvious engineering challenge. The various control schemes, such as using input terminal voltages for downstream MOSFETs and current-triggered gate signals for upstream MOSFETs (as depicted in FIGS. 4b-e of '696), represent common design approaches for synchronous rectifiers. Sensing current via current transformers to control MOSFET gates to emulate diode behavior (preventing reverse current) is a known technique in power electronics for optimizing synchronous rectification efficiency.

III. Inductive Power Transfer at Non-Resonant Frequency

The '696 patent claims an inductive power transfer system where the driving voltage oscillates at a transmission frequency "significantly different from the resonant frequency" of the inductive couple. This transmission frequency is selected to lie in a "near-linear region" where induced voltage varies approximately linearly with frequency, allowing the driver to adjust frequency for power regulation. The system also includes a voltage monitor (peak detector) to detect significant increases in primary voltage indicative of hazards (Summary; FIGS. 6a-e).

Combination 3: Kuennen et al. (U.S. Pat. No. 6,825,620) OR Baarman (U.S. Pat. No. 7,212,414) + General Knowledge of Resonant Circuit Behavior and Safety Monitoring.

• Prior Art Disclosure: The '696 patent itself identifies problems with resonant operation: "At resonance small variations to the system result in large changes to the power transferred. A further problem associated with resonant transmission is the high transmission voltages involved."
  • Kuennen et al. describe a ballast circuit that adjusts driving frequency to seek resonance and includes a "current limit circuit that is inductively coupled to the resonant tank circuit. The current limit circuit disables the ballast circuit when the current in the ballast circuit exceeds a predetermined threshold or falls outside a predetermined range."
  • Baarman describes a contactless power supply capable of modifying the resonant frequency of the tank circuit, the inverter frequency, the inverter duty cycle or the rail voltage of the DC power source.
• Motivation to Combine: A PHOSITA, aware of the inherent problems of high sensitivity and high voltages associated with operating inductive power transfer systems at resonance (as explicitly stated in the '696 background), would be motivated to explore alternative operating frequencies.
  • Knowing the typical frequency-amplitude response curve of resonant circuits (like FIG. 6b of '696), it would be an obvious engineering choice to operate the system in the "near-linear regions" (6, 8) off-resonance where the induced voltage changes more predictably and less drastically with frequency variations. This directly addresses the sensitivity issue.
  • Both Kuennen and Baarman teach the concept of adjusting frequency for power control or system adaptation. Applying this known technique to regulate power within the chosen non-resonant, linear operating region would be an obvious application for a PHOSITA.
  • Kuennen describes a "current limit circuit" for safety. A PHOSITA would recognize the need for similar safety monitoring (e.g., voltage or current) in any inductive power system, especially when operating off-resonance where unexpected load changes (e.g., removal of secondary unit, introduction of conductive objects causing power drains) could lead to undesirable voltage or current spikes. The use of a "voltage monitor" or a "peak detector" to detect such increases and implement protective actions (e.g., shutdown, warning) is a standard safety measure in electrical engineering.

IV. Inductive Power Adaptor with Heat Dissipation

The '696 patent claims an inductive power adapter with a grip thermally isolated from the power receiver, a cooling system (air outlets above, inlets below for convection, and a heat sink), and features like a heat sink smaller than the casing diameter to allow air circulation, and a dust-guard (grip overhangs outlets) (Summary; FIGS. 5a-d).

Combination 4: General Inductive Power Receiver + General Knowledge of Thermal Management and Mechanical Design.

• Prior Art Disclosure: The '696 patent's background notes the issue of heat in high-power inductive systems: "Energy losses associated with high power inductive transfer systems are typically larger than those in low power systems ... an uncoupled high power primary coil or its surroundings may become dangerously hot." The problem of heat is known for such systems.
• Motivation to Combine: A PHOSITA designing a high-power inductive receiver or adapter, especially one intended for user handling, would be motivated to incorporate known thermal management and ergonomic design principles to ensure user safety and device longevity.
  • Thermal Isolation of Grip: Designing a handheld device to keep user-contact surfaces cool is a fundamental ergonomic and safety consideration. Thermally isolating the grip from heat-generating components (secondary coil, PCB with rectifiers, etc.) is an obvious design choice for any device that generates heat.
  • Cooling System (Heat Sinks, Convection): The use of heat sinks (e.g., metallic disks of aluminum or copper) to spread and dissipate heat, and natural convection cooling (with air inlets below and outlets above to facilitate airflow) are long-established, fundamental principles of thermal management in electronics. Designing the heat sink to be smaller than the casing to allow air circulation is a common technique to enhance convection.
  • Dust Guard: Incorporating a dust-guard, such as the grip overhanging the air outlets, is a basic mechanical design consideration for protecting internal electronics from environmental ingress, particularly in devices with cooling vents.

V. Inductive Communication Channel for Uninterrupted Power Transfer

The '696 patent claims an inductive communication channel (7120) that transfers signals from the secondary inductive coil (7320) to the primary inductive coil (7220) concurrently with uninterrupted inductive power transfer. This is achieved by a transmission circuit in the secondary unit momentarily connecting an electrical element (e.g., a low resistance) to the secondary coil to increase the resonant frequency, which is then detected by a receiving circuit (e.g., a voltage peak detector) in the primary unit as an increase in primary voltage (Summary; FIGS. 7a-d).

Combination 5: Parks & Register (U.S. Pat. No. 5,455,466) + Baarman (U.S. Pat. No. 7,212,414) + General Knowledge of Resonant Circuits and Sensing.

• Parks & Register Disclosure: Parks & Register teach using the "same inductive link" for transferring both power and data between a portable device and a support unit. However, the '696 patent critically notes that in Parks' system, "Power transmission must therefore be interrupted in order to transmit data signals from the secondary winding to the primary winding. As a result, Parks' system does not offer any solution to providing a feedback signal for the regulation of uninterrupted inductive power transfer to an electric load." This explicitly identifies a known problem in the prior art that the '696 patent aims to solve.
• Baarman's Disclosure: Baarman discloses a contactless power supply capable of modifying the resonant frequency of the tank circuit, among other parameters.
• Motivation to Combine: A PHOSITA, aware of Parks' system and its limitation of requiring power interruption for secondary-to-primary data transfer, would be motivated to find a way to transmit data concurrently with uninterrupted power. Recognizing from Baarman and general electrical engineering principles that altering circuit parameters can change resonant frequency, and that such changes can be detected, would lead to an obvious solution.
  • Modifying Resonant Frequency for Signaling: Given Baarman's teaching of modifying resonant frequency, and the fundamental principle that adding an electrical element (like a resistor) to a resonant circuit changes its characteristics, it would be obvious to a PHOSITA to momentarily connect a small electrical element (e.g., a low resistance) to the secondary coil to cause a detectable shift in the system's resonant frequency.
  • Detecting Resonant Frequency Change in Primary: When operating an inductive power transfer system (especially in a non-resonant region as discussed in the '696 patent's non-resonant section), a shift in the system's resonant frequency will cause a measurable change in the primary coil's voltage or current. Using a voltage monitor or peak detector (as already discussed for safety in Kuennen and the '696 patent itself) in the primary circuit to detect these changes and interpret them as signals would be an obvious application of known monitoring techniques.
  • Uninterrupted Transfer: By inducing a change in resonant frequency rather than a separate modulated signal that requires interruption (as in Parks), this method allows power to continue flowing while data is transmitted. The specific wiring configuration of the electrical element to one input and one output of the rectifier to only draw power during "one half of the AC cycle" is an obvious optimization for minimizing power loss of the signaling mechanism.
  • Modulation/Demodulation: Once a reliable mechanism for creating and detecting changes (e.g., voltage spikes) is established, using standard modulation and demodulation techniques to encode and decode bit-rate signals is a well-known method in communications for transmitting information.

In summary, the key aspects of US 9,048,696, including the transmission-guard, low heat-loss rectifier, non-resonant frequency operation, heat-dissipating adapter, and inductive communication channel, appear to be obvious combinations or adaptations of known prior art principles and techniques, driven by clear motivations to solve known problems (e.g., safety, efficiency, uninterrupted data transfer) in inductive power transfer systems.