A few articles have been written about Apple Watch overheating, like the one from iKream published earlier this month. Yesterday, the US Patent & Trademark Office published a patent application from Apple for systems and methods for accurately determining a temperature gradient between two or more discrete locations in a wearable electronic device case like the Apple Watch. This is a possible solution that could greatly improve the temperature maintenance of future cooler Apple devices.
In Apple’s patent background, they note that an electronic device such as the Apple Watch may include a temperature sensor. An output of the temperature sensor can be used to calibrate or adjust an output of another sensor or subsystem of the electronic device that is sensitive to temperature changes.
Many electronic devices include multiple temperature-sensitive sensors or subsystems. However, because conventional temperature sensors take up space in an electronic device package and can be expensive components, it is often not possible to include a dedicated temperature sensor with every temperature dependent sensor or subsystem. an electronic device. As a result, at least some sensors or subsystems of conventional electronic devices operate in a sub-optimal, temperature-dependent manner.
Overall, Apple’s patent covers an electronic device case (e.g. Apple Watch, Apple Pencil, AirPods Pro & Max, future smart armband and/or health monitoring devices, etc.) which includes a temperature sensing system comprising a temperature sensor and a differential temperature probe.
The differential temperature probe includes a flexible substrate defining two ends. A first end is thermally coupled to the temperature sensor and a second end is thermally coupled to a surface, volume or component of the electronic device.
The temperature probe is an in-plane thermopile comprising an array of series-coupled thermocouples extending from the first end to the second end. A temperature measured at the temperature sensor may be a first measured temperature and a voltage difference between the conductors of the differential temperature probe may be correlated to a temperature differential with respect to the first measured temperature. A sum of the differential temperature and the first measured temperature is a second measured temperature, quantifying a temperature of the second end of the differential temperature probe.
An internal probe location can be defined relative to a particular electronic component inside an electronic device package, such as a processor, memory, battery, display, or input sensor. In other cases, an external probe location may be defined relative to an external surface of an electronic device enclosure, such as a cover glass surface, an exterior button or input device, or a back surface such as a back crystal of a smart watch.
Apple’s patent FIG. 1 below illustrates an example of Apple Watch that can incorporate a temperature detection system; FIG. 2 shows a simplified system diagram of a temperature sensing system disposed inside the case of an Apple Watch; FIGS. 5C through 5F illustrate an example of a differential temperature probe that takes a low aspect ratio rectilinear shape. In particular, temperature probe 500a implemented as an in-plane thermopile may be supported by a substrate (#502) on which a continuous conductive path (#504) is attached.
As shown in Figs. 5E-5F above, a cross-shaped temperature probe may be suitable in some implementations. In particular, in Fig. 5E, a #500c temperature probe is shown.
For engineers who want to dig into the details, see Apple’s patent application number 20220026284.
Considering that this is a patent application, the timing of bringing such a product to market is unknown at this time.