USB Power Delivery is a new spec adaptation from the USB Implementers Forum:
USB has evolved from a data interface capable of supplying limited power to a primary provider of power with a data interface. Today many devices charge or get their power from USB ports contained in laptops, cars, aircraft or even wall sockets. USB has become a ubiquitous power socket for many small devices such as cell phones, MP3 players and other hand-held devices. Users need USB to fulfil their requirements not only in terms of data but also to provide power to, or charge, their devices simply, often without the need to load a driver, in order to carry out “traditional” USB functions.
The USB Power Delivery specification enables the maximum functionality of USB by providing more flexible power delivery along with data over a single cable. Its aim is to operate with and build on the existing USB ecosystem.
USB Power Delivery offers the following features:
- Increased power levels from existing USB standards up to 100W.
- Power direction is no longer fixed. This enables the product with the power (Host or Peripheral) to provide the power.
- Optimize power management across multiple peripherals by allowing each device to take only the power it requires, and to get more power when required for a given application.
- Intelligent and flexible system level management of power via optional hub communication with the PC.
- Allows low power cases such as headsets to negotiate for only the power they require.
Of course USB Power Delivery will be fully backwards compatible with existing USB cables and solutions. But USB PD-compliant phones and devices in 2014 and beyond will negotiate how best to transfer power along with genuine data traffic.
Note that there's an official introduction to the technology here, in PDF format: PD Introduction (664KB)
According to SlashGear, "USB PD (Power Delivery) is set to be the new standard for the next generation, working with standard specifications set to start taking effect as early as 2014. "
We've been used to charging smartphones over USB and current being limited to 500mA typically (for a USB 2.0 port on a laptop or desktop, for example), but it seems as if 2014's and 2015's smartphones will be USB PD compliant and, from new computers and other peripherals at least, will be able to charge at full current capacity and rate, equivalent to plugging into a manufacturer-supplied/optimised mains charger.