Editing AC adapter (section)

==Use of USB==
{{See also|USB hardware#Power}}
[[File:USB AC Adapters (cropped).JPG|thumb|Common sizes of USB AC adapters]]

The [[Universal Serial Bus|USB]] connector (and voltage) has emerged as a de facto standard in low-power AC adapters for many portable devices. In addition to serial [[digital data]] exchange, the USB standard also provides {{nowrap|5 VDC power}}, up to {{nowrap|500 mA}} ({{nowrap|900 mA}} over USB 3.0). Numerous accessory gadgets ("[[USB decoration]]s") were designed to connect to USB only for DC power and not for data interchange. The [[USB Implementers Forum]] in March, 2007 released the USB Battery Charging Specification which defines, "...limits as well as detection, control and reporting mechanisms to permit devices to draw current in excess of the USB 2.0 specification for charging ...".<ref>{{cite web|url=http://www.usb.org/press/pressroom/2007_04_17_usbif3.pdf|title=USB-IF Enhances Battery Charging Capabilities with New Spec.|date=2007-04-17|access-date=2011-02-21|archive-url=https://web.archive.org/web/20110728150023/http://www.usb.org/press/pressroom/2007_04_17_usbif3.pdf|archive-date=2011-07-28|url-status=dead}}</ref>   Electric fans, lamps, alarms, coffee warmers, battery chargers, and even toys have been designed to tap power from a USB connector. Plug-in adapters equipped with USB receptacles are widely available to convert {{nowrap|120 VAC}} or {{nowrap|240 VAC}} power or {{nowrap|12 VDC}} automotive power to {{nowrap|5 VDC}} USB power (see photo at right).

The trend towards more-compact electronic devices has driven a shift towards the [[micro-USB]] and [[mini-USB]] connectors, which are electrically compatible in function to the original USB connector but physically smaller.

In 2012, a [[USB Power Delivery Specification]] was proposed to standardize delivery of up to 100 watts, suitable for devices such as [[laptop computer]]s that usually depend on proprietary adapters.