US Patent 11675407 Smartphone and add-on device power delivery system

A system incorporating a smartphone comprising a smartphone and add-on device coupled to each other via combined data/power interface, wherein the smartphone comprises a rechargeable battery connected to battery protection circuitry and the add-on device optionally comprises a rechargeable battery connected to battery protection circuitry as well, the combined data/power interface comprises: one or more data pins for transferring data between the smartphone and the add-on device; one or more regulated power delivery pins; and one or more protected-battery power delivery pins, wherein the regulated power delivery pins are used to charge the battery of the smartphone from an external charger coupled to the add-on device, the batteries are connected to the battery protection circuitries that is configured to protect the battery by cutoff or limit the current or voltage on the battery electrodes, the protected-battery power delivery pins are connected to the battery protection circuitries of the smartphone or add-on device. The following power delivery paths are enabled: (1) the add-on device is powered by the battery of the smartphone through the protected-battery power delivery pins that are connected to the output of the battery protection circuitry of the smartphone. (2) the smartphone is powered by the battery of the add-on device through the protected-battery power delivery pins that are connected to the output of the battery protection circuitry of the add-on device, and (3) the batteries charge each other through the protected-battery power delivery pins that are connected to the output of the battery protection circuitries of smartphone and add-on devices.