- Definition
- Programmable Power Supply (PPS) is the USB Power Delivery mode in which the source produces a continuously adjustable voltage within a declared range, allowing the device to step the voltage in small increments as it charges.
This page defines the term. For what it means in practice, see USB Power Delivery and PPS: how to read a charger specification.
Why adjustable voltage exists
A battery does not want a constant voltage. It wants a controlled current while it is empty and a controlled voltage as it fills. A charger that can only offer 5 V, 9 V, 15 V or 20 V has to approximate that curve in coarse jumps, and each jump wastes energy as heat inside the device.
PPS lets the device ask for a specific voltage within a range, in steps small enough that the charging curve can be followed closely. Less energy is dissipated inside the phone, and less heat means the charging rate can be sustained for longer before thermal protection intervenes.
PPS and AVS are not the same mode
PPS sits in the Standard Power Range and adjusts in small steps around a low voltage. AVS is the adjustable mode introduced with the Extended Power Range, above 100 W. A charger may support one without the other, and the PDO list is where the difference shows.