The new USB Power Delivery standard, used in electronic devices and cables, promises to reduce clutter,
provide unprecedented inter-operability, simplify docking, and provide much faster charging.
USB has gained international adoption for battery charging, especially for mobile electronic devices.
Standardization on USB for charging devices was driven primarily as a means to reduce electronic waste
by
eliminating the need for a separate proprietary charger for each electronic device. The USB Power
Delivery
(USB-PD) specification was written to further reduce cable clutter through power sharing and can
accommodate powering devices up to 100 watts, yet is designed to co-exist with standard USB Battery
Charging implementations.
USB-PD provides directional control in powering devices and power level management. In conjunction with
the other USB standards, consumers will only notice that interoperability is greatly enhanced with a
single cable that can both provide power and data. Even better, if two USB-PD compatible devices are
connected and one loses power, the other device will pick up the duty of powering its USB-mates
automatically. For example, if a battery-powered Chromebook and a monitor (both USB-PD devices) are
connected and the Chromebook battery goes dead, the monitor (if powered) will notice the Chromebook’s
flagging power and swap roles to become the provider of power. The monitor will pick up on powering the
Chromebook, automatically, within milliseconds.
USB-PD is compatible with existing USB 2.0 and USB 3.0/3.1, coexists with existing USB On-the-Go and
battery charging set-ups, and can sense and limit power delivery on cables to deliver higher voltages
only via USB-PD compliant cabling. Thus, USB-PD aware cables are able to deliver up to 100W, as
compared
to older USB cables that can deliver only 7.5W at the very most. (The USB-BC 1.2 (Battery Charging)
specification is for 5V @ up to 1.5A = 7.5W.)
USB-PD icons will identify PD ports and cables:
Figure 1: Concept icons; may not be final. Source, Intel IDF 2012.
The operation of USB-PD starts with a legacy-level 5V VBUS connection. Current and voltage are
adjusted
after negotiation takes place over VBUS; no USB data lines are used, and all of this takes place
within
milliseconds. Negotiation for power requirements are listed in the USB-PD spec as "Profiles." There
are
currently 5 profiles for power:
| 0 |
Reserved |
|
|
| 1 |
5V @ 2A |
10W |
Default start-up profile. Tablets. |
| 2 |
5V @ 2A, 12V @ 1.5A |
18W |
Netbooks |
| 3 |
5V @ 2A, 12V @ 3A |
36W |
Ultrabooks |
| 4 |
5V @ 2A, 12V, 20 V @ 3A |
60W |
Fast charging of mobile devices |
| 5 |
5V @ 2A, 12V, 20 V @ 5A |
100W |
Laptops, Monitors, TVs |
Devices that comply with the USB-PD standard can also switch the source of power delivery without
changing the cable’s direction. For example, if a laptop, monitor, and cabling are both USB-PD
compliant
and the laptop loses power, the USB portion of the monitor will sense this and negotiate to have the
monitor deliver power.
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