The topic of inductive charging in patent filings has surfaced a number of times in the last month. We covered a granted patent on February 24 relating to magnetic connectors integrated into an inductive charging dock for a MacBook. Apple already uses a MagSafe connector for its new Apple Watch inductive charging system, and so Apple's methodology is similar – and for a reason that's noted in today's patent report. Apple also revisited a patent application recently that supports inductive charging within a possible future iPad Smart Cover. Today we discovered a new European patent filing that Apple made earlier this week that was about inductive charging. While Apple's patent filing lists home appliances and wearable devices as categories that could take advantage of inductive charging, like the Apple Watch, it was interesting to see that they also listed "electric vehicles" as another category which was timely.
While inductive charging is interesting, especially due to the Apple Watch, it's Apple's Near Field Magnetic Resonance Power Supply invention that is the one we'd like to see come to market in the not-too-distant future. Intel's Skylake processor is going to support such technology later this year – so Apple's solution may not be too far behind.
Apple's Patent Background
Many electronic devices include one or more rechargeable batteries that require external power to recharge from time to time. Often, these devices may be charged using the same or similar connection type, for example via universal serial bus ("USB"). However, despite having common connection types, multiple devices often require separate power supplies with different power outputs. These separate power supplies are burdensome to use, store, and transport from place to place. As a result, the benefits of device portability are substantially limited.
Furthermore, charging cords may be unsafe to use in certain circumstances. For example, a driver of a vehicle may become distracted attempting to plug an electronic device into a vehicle charger. In another example, a charging cord may present a tripping hazard if left unattended.
To account for these and other shortcomings of portable electronic devices, some devices include an inductive recharging system. The user may simply place the device on an inductive charging surface in order for the battery to be recharged. However, due to extra circuitry within the portable electronic device required to support the inductive charging system, battery life of the device may be undesirably reduced. For example, to maintain or reduce the form factor of the device, the battery may be reduced in size or capacity. In another example, the inductive charging system may present a load to the battery when the system is not in use, reducing battery life. Accordingly, although inductively charged devices may be more convenient for the user, they may need to be recharged more often.
Therefore, there may be a present need for a method of delivering useful power to a portable device that does not require a separate power supply and does not itself deplete the battery of the portable electronic device.
Apple Invents Power Management for Inductive Charging Systems
Apple's invention relates to techniques for delivering useful power to a portable electronic device that does not deplete the battery of the portable electronic device. More specifically, the patent covers electromagnetic inductive power transfer, and in particular to adaptive power control systems for maximizing the efficiency of power transfer.
An inductive charging system may include an inductive charging station to transmit power and a portable electronic device to receive power. Portable electronic devices may include media players, media storage devices, personal digital assistants, tablet computers, cellular telephones, laptop computers, smart phones, styluses, global positioning sensor units, remote control devices, health monitoring devices, wearable devices like a watch, sports accessory devices, electric vehicles, home appliances, medical devices and the like. Of course Apple will be introducing inductive charging with the new Apple Watch as noted below.
Apple notes that in certain embodiments, the power output from the inductive charging station may be at least partially controlled or influenced by periodic reports from the portable electronic device itself. For example, a portable electronic device may include a wireless transmitter configured to transmit information to an inductive charging station. Such information may include identifying information, authentication information, or power state information.
Power state information may include current or future power requirements, time estimations until a battery is fully charged, the current charge of the battery, or other power related information. The portable electronic device may send periodic updates, once or more per second. The wireless transmitter may be of any suitable technology such as, for example, Wi-Fi, RF, Bluetooth, near field communication ("NFC"), or infrared. In certain embodiments, the wireless transmitter may be an existing component of the portable electronic device, such as a camera flash or a display.
A Surge Protector: In certain embodiments, the portable electronic may include a surge protection circuit, such as a capacitor, operative to prevent damage to the portable electronic device as a result of an increase in power transmitted by the transmit coil. For example, if the transmit coil increases the power it transmits, there may be a power surge in the power-receiving circuitry of the portable electronic device. Including a capacitor or other surge protection circuitry may prevent damage to the portable electronic device as a result of an unexpected increase in the power by the portable electronic device.
Apple also notes that the quality of the mutual inductance or inductive coupling may be substantially affected by many factors including the relative alignment of the transmit coil and the receive coil and the distance between the two. One may appreciate that for increased power transfer between the transmit and the receive coils, they should be close together and aligned along a mutual axis. In the case of the Apple Watch Apple is using MagSafe to ensure precise alignment.
One may further appreciate that electromagnetic induction requires the current supplied to the transmit coil to change as a function of time. Often, alternating current is supplied at a frequency selected based upon the geometry and number of turns of the transmit coil and receive coil. In certain embodiments, the frequency selected for the alternating current supplied to the transmit coil may be approximately 150 kHz. In other embodiments, the frequency selected may be greater than or less than 150 kHz.
Apple's patent FIG. 2 is a signal flow diagram in accordance with an embodiment of the present disclosure showing a ground connection controller in an off state.
Apple's patent FIG. 3 is a process flow diagram showing method of controlling an inductive charging system within a portable electronic device having a battery.
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