USB Power Delivery
Background
In July 2012 the USB Promoters Group announced the finalization of the USB
Power Delivery ("PD") specification, where USB evolves 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. "PD
aware" USB cables with standard USB type A/B connectors to deliver up
to 100W of power at 20V. For PD-aware cables with USB-micro B/AB connectors
the maximum power supported is up to 60W at 20V, 36W at 1V and 10W at 5V. The
intent is to permit uniformly charging laptops, tablets, USB-powered disks
and similarly higher power consumer electronics, as a natural extension of
existing European and Chinese mobile telephone charging standards.
Features
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.
Use Cases
Here are a few typical use-cases for Power Delivery:
- Enables new higher power use cases such as USB bus powered Hard Disk Drives
(HDDs) and printers. This eliminates the need for a separate power brick.
- A monitor with a supply from the wall can power, or charge, a laptop while
still displaying.
- USB power bricks or chargers are able to supply power through a laptop’s
USB ports.
- Laptops and USB power bricks can provide higher power to battery powered
devices (not currently defined by USB).
- Battery powered devices can get increased charging current from a hub and
then give it back temporarily when the user’s HDD requires to spin
up.
New challenges for developers
USB Power Delivery introduces a new side-band communication over the Vbus
wire. Similarly to the power-line technology, PD uses an FSK signal having
a carrier at 23.2MHz and delivering a throughput of 300kbps.
This new side-band communication has to be coordinated with the classic USB
2.0 and USB 3.1 communication, adding a level of complexity to developers taking
advantage of this increased power.
To enable adopters of this cutting-edge
technology, Ellisys creates the most technologically advanced protocol test
systems including protocol analysis, traffic generator and compliance verification.
The Ellisys USB Explorer 350 is latest and greatest protocol test system for
USB Power Delivery. Learn more »
Links
Here are a few links to pages containing a whole information range about USB
Power Delivery:
USB PD homepage
USB PD specification
USB PD DevCon presentations
Ellisys USB Explorer 350 Power Delivery
Analyzer and Generator
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