PORTLAND, Ore. — Vampire power—the standby milliwatts that device chargers continue to draw even when the device battery is fully charged or no device is connected to the charger—wastes resources and costs consumers billions annually worldwide. For its Watt Saver technology, Freescale combined a microcontroller with firmware to monitor power usage and a relay to cut power to the charger completely when it is not needed. AT&T already uses the technology in its Zero Charger for cell phones; now Freescale is pitching Watt Saver to a broader market.
“The average cell phone charger draws 30 milliwatts when not in use,” said Glen Burchers, marketing director for consumer segment at Freescale. Multiply that by “the 4 billion units in use worldwide, and you end up with roughly $1 billion in wasted vampire power per year, or about 1,200 megawatts—the same amount of power produced by a medium-sized nuclear power plant."
According to the European Union, standby power for electronic devices already accounts for more than 10 percent of worldwide electricity consumption and will rise to 49 terrawatt-hours by 2014, with more than 2 billion computers idling in sleep mode. Freescale says its hybrid hardware/firmware package lets OEMs cut vampire power to zero for next-generation green consumer electronics.
The Watt Saver is compatible with the International Telecommunication Union’s L.1000 standard for 0-W, no-load power consumption. An 8-bit processor monitors the direct-current output of the device during charging, and when it detects that the battery is fully charged, it disconnects the alternating current from the internal transformer with a small solid-state relay. A supercapacitor keeps the microprocessor running as it monitors the output line to see whether the battery need charging. Once a depleted battery is inserted into the charger, the processor switches the relay back on. (The supercap keeps the Watt Saver alive for a year, after which it automatically engages the power line for recharging; it then resets to 0-W, no-load power consumption.)
Besides cell phone rechargers, Freescale is aiming its Watt Saver technology at touchscreen tablets, e-readers, portable music players and, soon, higher-powered battery-operated devices such as laptops and netbooks.