USB Power Delivery 2.0 introduced some changes to the way that power ratings between devices are handled, making the standard more flexible than before. The old set of Power Profiles were removed in PD 2.0 and replaced by Power Rules that allow for a wider range of current negotiations. The USB 3.1 specification adopted Power Profiles instead, but is only rated up to 15W rather than 100W.
PD 3.0 made some tweaks to enhance power delivery, but the Power Rules are the same as PD 2.0 products. Rules are split into four target power categories; 7.5W, >15W, >27W, and >45W; each of which offers a range of voltage and current configurations. Sources supplying more than 15 watts offer voltages of 5 and 9 volts, those supplying more than 27 watts offer 5, 9 and 15 volts, and those supplying more than 45 watts offer 5, 9, 15 and 20 volts. The maximum 100W power supply is achieved with 20V and up to 5A, although all of the other modes cap out at 3A, depending on the required power.
• Increased power levels from existing USB standards up to 100W.
• The 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.
• It allows low power cases such as headsets to negotiate for only the power they require.