A personal computer or other electronic device may be powered by an external power supply and may have a legacy ambient temperature sensor e.g. because a fan whose speed is controlled by a controller, uses as an input, inter alia, ambient air temperature received from the legacy temperature sensor which may be disposed adjacent the fan. A controller may be provided which limits the current based on ambient air temperature reading/s flowing out of the sensor thereby to optimize power consumption relative to conventional “worst-case-assumption based” control of the current, in which current supplied is limited, mindful of a pre-set worst-case temperature assessment, to an un-necessarily low level of current.