Beginners • Re: raspberry pi 5 power supply

Power delivery is by negotiation, similar to Ethernet speeds and WiFi bands. The power supply detects PD if the cable has a working PD chip and the attached device has a working PD chip, then publishes a list of options. The device looks at the published list and decides if it can use any of the options. The device then requests one of the offered selections. The power supply can accept the request or reject the request, something it might do if it is heating up or has multiple ports and the usage on other ports is increasing.

Devices like notebooks mostly used 19 volts direct from their original power supplies so the updated USB ones look for 20 volts. And they used at least 60 watts, making a 27 watt power supply almost useless. I looked at the specs for a number of devices and PD cables. They jumped from 5 volts to 20 volts, ignoring the other options.

12 volts is going away. 9 volts is good for charging 6 volt batteries or 2 * 3.3 volt lithium up to 45 watts. 15 volts is good for charging 12 volt batteries or 4 * 3.3 volt lithium up to 60 watts or a small notebook. 20 volts can give you 100 watts for a big fast games oriented notebook.

The main advantage of the Pi 5 27 watt supply is running an NVMe SSD plus two * 2.5" disks.

The latest PD standard allows up to 48 volts which, at 5 amps, would be 240 watts, enough to run a tiny macchiato machine.

Statistics: Posted by peterlite — Tue Nov 19, 2024 5:13 am

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