Piromman 5 refuses to turn on with a 27W power supply

General
1

551

Hello,

sorry for my english, I’m French.

I was recently given a Pironman 5 case with a 16GB Raspberry Pi 5 to create a Home Assistant system, along with a 27W power supply from IRasptek and another 27W power supply from Raspberry Pi. Neither of these power supplies will start my case; nothing lights up. However, if I plug in a phone charger, the case powers on, but I get an undervoltage message. Home Assistant works, though. Can you help me understand why the official 27W Raspberry Pi power supplies don’t work with my case? Sincerely, Hijack

2

Bonjour hijack,

Si tu retires le Raspberry pi 5 du pironman5 et que tu branche l’alimentation directement sur le Raspberry est-ce que tout fonctionne normalement?

3

Bonjour. Merci de m’aider.

Je viens de démonter le rasberry du boîtier Pironman et effectivement en branchant en direct l’alimentation 27 Watts Rasberry, cela fonctionne.

C’est donc soit la carte additionnelle du boîtier Pironman soit autre chose

Qu’en pensez vous?

4

Au moins le rpi5 et PSU sont ok. Tu peux rebrancher la carte hdmi au rpi5, t’assurer qu’ils sont bien connectés puis brancher le PSU et voir si tout fonctionne. Ensuite tu y installe la prochaine composante et tu reteste jusqu’à ce qu’il soit tout assemblé.

5

Bon j’ai tout démonté et remonté dans l’ordre en testant à chaque fois l’alimentation et cela refonctionne avec les alimentations 27 W.

A ne rien comprendre.

Merci de votre aide, bonne soirée

1 Like
6

Ce sont des choses qui arrivent. S’il y a quoique ce soit, ne te gêne surtout pas!

Bonne soirée et bonne année!

7

Regarding your previous statement “hijack,” are you saying that after re-plugging the USB-HDMI adapter, the 27W power supply can now provide power to the Pi 5 through the USB-HDMI adapter?

If yes, this indicates that the USB-HDMI adapter was not making proper contact with the Pi 5’s interface earlier, which prevented the Pi 5 from receiving power via the adapter.

The reason lies in the interface protocol of the 27W power adapter.
The 27W power supply is the “standard PD power supply” for the Pi 5, designed to strictly follow the Power Delivery (PD) protocol logic. However, it has a particular requirement—it must complete a “protocol handshake” before outputting power.

Normal Process:
27W PD Power Supply → USB-HDMI Adapter → Pi 5 Type-C Port. When the adapter plug is fully inserted, the Pi 5’s CC1/CC2 pins make contact with the adapter. Both sides negotiate the “PD protocol” (confirming power, voltage, etc.). Only after a successful negotiation does the power supply output 27W of power.

Initial Failure Reason:
The adapter plug was not fully inserted, causing the protocol pins (CC1/CC2) to not make contact. As a result, the 27W power supply could not complete the “handshake” with the Pi 5. Even if the power pins (VBUS) might have been connected, the power supply would refuse to output power (a safety mechanism of the PD protocol to prevent accidental power supply).

Reason It Works After Re-plugging:
When re-plugging, the adapter plug and the Pi 5 interface fit together perfectly. Both the protocol pins and power pins make good contact, allowing the 27W power supply and the Pi 5 to successfully complete the PD protocol negotiation, thus enabling normal power supply.