PPS (Programmable Power Supply), AVS (Adjustable Voltage Supply) 

What is PPS

PPS (Programmable Power Supply) - a USB PD mode in which the device requests the required voltage and current limit from the charger in small steps. The PPS protocol was introduced in USB PD 3.0.

PPS allows a device to dynamically request voltage and current limits according to the battery's current charging conditions. This can reduce voltage-conversion losses, lower heat generation, and improve charging efficiency.

With PPS, the source provides a programmable voltage range instead of only fixed PDOs. Voltage is adjusted in 20mV steps , and the current limit in 50mA steps . The range can extend up to 3.3-21V depending on the source capabilities. The parameters can be changed dynamically during charging.

The following charging modes are defined by the latest PD 3.2 PPS standard:

• 3.3-5.9V/3A

• 3.3-11V/3A

• 3.3-16V/3A

• 3.3-21V/3A

• 3.3-21V/5A (requires 5A cable)

Some charger manufacturers implement a limited PPS range up to 20V, which may be incompatible with devices that require a maximum PPS voltage of 21V.

With a wide PPS range, lower-power chargers can encounter a so-called power cliff: the maximum APDO current is limited by the source power at the upper voltage boundary, and that current limit then applies across the entire range. For example, if a charger advertises PPS 3.3-21V/2.1A, its maximum power at 9V within that range is about 18.9W.

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The PPS protocol is widely used by manufacturers of charging adapters and power banks, though there are some exceptions. Typically, these exceptions stem from specific use cases where PPS support is not required. For example, this applies to some PD chargers for laptops, as well as Apple adapters and accessories designed for Apple devices. Specifically, Anker produces a separate line of chargers for Apple devices that do not support PPS, although this protocol is present in the brand’s other models.

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What is AVS

AVS (Adjustable Voltage Supply) - a USB PD mode in which the device requests voltage in 100mV steps within a defined range; it has no programmable current limit like PPS. AVS was introduced in USB PD 3.1 for the EPR range. In PD 3.2, AVS was extended to the SPR range up to 100W, with a minimum voltage of 9V.

The Peak Current feature is defined for AVS and allows a power source to advertise its ability to provide increased current for short periods, for example, during brief load peaks in computer systems.

AVS charging modes defined by the latest PD 3.2 standard:

• SPR AVS 9-15V - up to 3A, for 27-45W sources

• SPR AVS 9-20V - up to 3A, for 45-60W sources

• SPR AVS 9-20V - up to 5A, for 60-100W sources; currents above 3A require a 5A cable with an e-marker chip

• EPR AVS 15-28V - up to 5A, up to 140W - requires a 5A EPR cable with an e-marker chip

• EPR AVS 15-36V - up to 5A, up to 180W - requires a 5A EPR cable with an e-marker chip

• EPR AVS 15-48V - up to 5A, up to 240W - requires a 5A EPR cable with an e-marker chip​​

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Known USB charging adapters with PD 3.2 SPR AVS support