PoE & DC power supply for Raspberry Pi and BeagleY-AI

Glossary

SBC - Single Board Computer

DPS - Dual Power Supply

PoE - Power over Ethernet

PSE - Power Sourcing Equipment

PD - Powered Device

Idea

For certain applications, it is more convenient to have a PoE power supply as a module that can be placed alongside the Raspberry Pi board rather than on top of it as a HAT, for example, when the space above the Raspberry Pi is already occupied by another HAT or a fan.

Motivation

One might suggest using a standard PoE HAT and placing it externally, then connecting it to the Raspberry Pi with wires. While this is a reasonable ad-hoc solution, it has several drawbacks, such as 1) a non-optimal form factor and 2) the lack of an alternative DC input.

Therefore, I decided to design a new module built from the ground up to function as a standalone board.

Design

The PCB essentially serves as a housing for two main components: a Silvertel PoE module and a Cincon DC/DC converter.

Schottky diodes (D3 and D7) are used to protect the modules from each other.

Silvertel offers free support to users of their products. I therefore sent them my design, and they responded with a few minor comments, which I addressed.

Raspberry Pi PoE connector

I tested it with Raspberry Pi 4, Raspberry Pi 5, and BeagleY-AI boards. They all feature the same 4-pin PoE connector.

DPS board connectors

The module has two internal 4-pin connectors (PoE and PWR) and an external DC connector.

Connecting DPS and SBC

PoE <---> PoE;

PWR <---> 5 V pins (2, 4) and GND (6, 9) pins of RPi GPIO header.

Powering

To power the device, do one of the following:

• Plug an Ethernet cable into the SBC's Ethernet port. The cable must be connected to a PSE (PoE switch/router or injector).
• Connect an external DC power supply (12 - 24 V) to the DPS power jack connector (2.0 x 6.5 mm).

In general, they both can be connected simultaneously. In this case, the Silvertel PoE module will most likely be active, since it outputs approximately 0.3 V higher voltage than the Cincon DC/DC converter.

Components

I purchased all components from DigiKey. The attached KiCad schematic file includes all the values required to identify each component.