Technology · Power
AVS — Adjustable Voltage Supply
The Power Delivery mode iPhone uses for its fastest charge.
AVS, Adjustable Voltage Supply, is a mode of USB Power Delivery 3.2 in which the phone asks the charger for exactly the voltage it wants at each moment, in fine steps, instead of choosing from a few fixed levels. iPhone 17 and iPhone 18 use it for their fastest charge, and it needs a charger that can supply 40 W or more.
The phone steers the charger
With fixed Power Delivery levels, the phone receives a voltage it did not choose and converts it inside its own body, where the conversion becomes heat next to the battery. With AVS the charger supplies the voltage the battery wants, so the phone converts less and stays cooler. Cooler charging holds its speed for longer.
Why 40 W is the threshold
A phone only takes its fastest charge if the adapter can offer the AVS profile at the power it needs. Below 40 W the negotiation falls back to ordinary Power Delivery and the charge is slower. This is the line between a charger that is compatible with iPhone and one that charges it at its own speed.
On the ERONIX range
Fermi45 supplies AVS at 40 W: iPhone 17 Series to about 50% in 20 minutes. Entropy67 supplies it at 60 W: iPhone 18 Series to about 50% in 15 minutes. Both figures rest on the factory's PD 3.2 AVS certification, and both vary with battery state, temperature, the cable and the software on the phone.
Honest limits
- AVS helps only a phone that asks for it; an older iPhone on an AVS charger simply charges over ordinary Power Delivery at its own maximum.
- The cable is part of the negotiation: a cable rated below the adapter's output caps the result.
- Time-to-50% is a stated figure under stated conditions, not a promise for every charge.
Published 28 September 2026 · Reviewed by 28 March 2027 · All technology
