Imagine a cell phone that doesn’t require an AC charger. Sound like a bright idea? It’s not that far away!
Apple has been granted a patent for an “integrated touch sensor and solar assembly” - a touchscreen combined with a photovoltaic (PV) panel. Besides the obvious application, a solar powered smartphone, we could see a new generation of PV powered devices that have touchscreens: tablet computers, kiosks, point-of-sale terminals, and smart appliances. The invention could also lead to smaller devices with lower-capacity batteries, since the battery can be recharged using ambient light and the device itself is powered in part by solar energy.
The patent application describes a typical capacitive-sensor touchscreen with embedded optical sensors. To reduce power consumption, the capacitive network remains unpowered until an object is detected. The optical sensors - essentially photovoltaic cells - are used to detect an approaching object. As the object shades parts of the PV panel the generated voltage and current are reduced. When the circuitry detects a reduction in PV-generated power, it enables the capacitive sensor network which takes over for precision pointing control. The capacitive sensors only use power when necessary. The optical sensors have the dual benefit of detecting an object and providing power to the device itself.
A system based on this invention would include a control circuit that sends the PV-generated power to the device and directs excess energy to the battery.
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