- Definition
- Adjustable Voltage Supply (AVS) is the adjustable-voltage mode in the extended power range of USB Power Delivery, allowing a source to produce a continuously variable voltage at levels above those PPS covers.
This page defines the term. For what it means in practice, see USB Power Delivery and PPS: how to read a charger specification.
PPS and AVS are not the same thing
Both let a device request a voltage rather than pick from a fixed list. They operate in different parts of the specification, and they are not interchangeable.
PPS works in the standard power range, at the voltages used by phones, tablets and small accessories. AVS was introduced alongside the extended power range, where the voltages are higher and the application is typically a notebook or a docking station.
Why it was needed
The extended power range pushed USB charging up to 240 W by raising the voltage rather than the current. Higher voltage is more efficient to transmit, but a fixed set of high voltages is a poor fit for a notebook, which wants a smooth voltage curve as its battery fills.
AVS provides that curve at the higher voltage levels, in fine steps, so a notebook can be charged from a USB-C source with the same control it would get from a dedicated power adapter.
Support for one adjustable mode does not imply support for the other: a device that requests AVS will not be served by a source that offers only PPS.