If recent rumors are to be believed, Apple’s wireless charging system may be making a come back. For answers, let’s examine Apple’s patent filings related to wireless charging devices.

AirPower was announced originally in 2017 along with the iPhone 8 and the iPhone X. It offered the freedom to simultaneously charge all of your Apple devices anywhere on the pad and the ability to monitor the charging state of any device. Its concept was meant to leapfrog well beyond the current state-of-the-art charging systems, such as those based on Qi charging technology. Unfortunately, AirPower was canceled before it hit the shelves.

Why did Apple pull the plug on AirPower? It’s promising features posed their own technical challenges. The complexity of simultaneously charging multiple devices, each with different power requirements, anywhere on a pad, all the while communicating charge levels and rates proved to be overwhelming. It would have required the positioning of multiple power transmitting coils over the surface of the mat along with sensors, processing, and logic circuitry to detect and provide optimal charging currents for different devices, all within close proximity to each other. Doing so would make managing the generated heat in such a small space very difficult. This thermal problem was one of the reasons for the eventual cancellation of the product in 2019 (Source: link).

After much effort, we’ve concluded AirPower will not achieve our high standards and we have canceled the project. We apologize to those customers who were looking forward to this launch. We continue to believe that the future is wireless and are committed to pushing the wireless experience forward” – Dan Riccio, Apple’s senior vice president of Hardware Engineering (Source: Tech Crunch)

To cut through the rumors, we examined Apple’s patent filings in this space for evidence of their continued research efforts towards a wireless charging solution. Apple already has a considerable number of patent filings in this area which peaked in 2017, the same year Apple first announced AirPower. The number of patent filings is projected to increase in 2020 suggesting continued internal efforts towards the same.

*forecasted applications count.

Apple’s Patents/Applications Related To Wireless Charging Devices

Recent patent publications from the shortlist are described below.

Overall Architecture

U.S. patent publication US20200059113A1 discloses a multi-device wireless charger with the total power capacity set to a specific limit. The charging device first generates an impedance image of any device placed on the charging pad and compares this impedance image to pre-stored impedance images of different wireless user devices, such as an iPhone, an Apple Watch, and the earbuds. Upon determining that the detected user device can be wirelessly charged, the charging device invokes an authentication mechanism to establish a wireless communication link and exchange device identifiers. Using the device identifier the charging device assigns priorities to the user devices. For example, if a user places a phone, watch, and earbuds on the charging device (in that order), the charging device may give priority to the phone, the watch, and the earbuds in the same order.

Further, the charging device can send a charging status indicator notification to the user devices being charged. If the charging device detects that there is insufficient power to charge a second or third device, it will disable the charging and send error notifications to the devices. Additionally, the charging device continuously monitors the user devices for position changes. In these instances, it will immediately halt charging, determine the impedance image(s) to reconfirm that the same device(s) are present, and then restart charging without changing the priority.

U.S. patent publication US20200059113A1 Titled “Wireless Power System With Device Priority”

Support for Multiple Wireless Charging Standards

While the above publication focuses on assigning priority orders to the devices being charged, recently granted U.S. patent US10601251B2 seems to be focusing on identifying user power specifications of the user devices locations on the multi-coil charging pad and selecting and controlling the appropriate power flow to the transmitter coils of the charging device.

Upon detection of a user device, the charger activates its transmitter coils to ping the receiver coil of the detected user device and measures the signal strength of a received response to identify the location of the device and the corresponding coils that are best suited for coupling for power transfer. The charger then establishes a communication link with the receiving device for authenticating and determining the user device’s onboard charging capabilities, including the wireless power standard to which the power receiving circuitry adheres. Next, upon determining the receiving circuit capabilities, the charging device selects the appropriate transmitter coils to drive for power transfer. Further, if it is determined that the receiver circuit does not have an onboard power flow controlling mechanism, the charger continues to maintain a communication link to exchange information required for flow control and implements the flow control on the transmitter side.

U.S. patent US10601251B2 Titled “Wireless Power System With Device PrioritySystem and method for power transfer”

Foreign Object Detection and Temperature Control

Both US20200059113A1 and US10601251B2 also disclose that the charging device performs foreign object detection before proceeding to establish a communication link and initiating a charge transfer. This foreign object detection protects the charger from falsely driving transmitter coils for energy transfer which could overheat the object, thus causing damage. The foreign object detection is disclosed in detail in U.S. patent US10658878B2.

The disclosed method utilizes an array of temperature sensors positioned on top of the plurality of charging coils and below the charging surface of the wireless charging pad. When an abnormal increase in temperature (usually due to the presence of a metallic foreign object) is detected, a control circuit halts wireless power transmission. Additionally, the temperature sensors also monitor the temperature at the charge receiving devices so that the control circuit can dynamically adjust the amount of power being transmitted. Thus, protecting both the charging device and the user devices being charged from excessive heat.

U.S. patent US10658878B2 Titled “Wireless charging system with temperature sensor array”

Device Authentication

The three patents and publications discussed above, all disclose that the wireless charger establishes a communication link with the power receiving device, performs authentication before initiating an exchange of information required for power transfer. U.S. publication US20200154275A1 takes authentication a step further and discloses a method of authentication for wireless power transfer using certificates.

This authentication method results in the establishment of trust between an initiator and a responder (i.e. the charger is the initiator and the charge receiving device is the responder). Upon establishing a communication link, the responder transmits a digitally signed certificate including a public key to the initiator. By validating the digital signature, the initiator can establish trust in the certificate provided by the responder. The initiator may then verify that the responder device owns the certificate by issuing a challenge nonce message. The responder can use a private key to produce a digital signature that proves it is in possession of a private key that corresponds to the public key contained within the trusted certificate.

U.S. publication US20200154275A1 Titled “Wireless power transfer device authentication”

In addition to the above examples, Apple’s portfolio has patent publications and granted patents disclosing almost many aspects of wireless power transfer. Examples include US10673541B2 which addresses interference to the cellular or WiFi connectivity of the user device while charging and US20180351373A1 which discloses a user interface to detect and display charging states of multiple devices being charged using a single wireless charging device.

The solutions disclosed in the above cases can be easily implemented with existing technologies. Thus it may be safe to presume that Apple might launch its own wireless charging solution in the very near future.

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