Laptop connectors and universal chargers (tips M3, M4, etc.)

Question

I am interested in having more information about connectors and identifiers (M3, M4, ... M31) used by laptop universal chargers.

• Is there any "official" list or convention for laptop connectors (pinout+voltage+current)?

• What about the M-x names in the picture? Who has made this list? is it recognized as "standard"?

• How the charger knows how much voltage has to supply?

• Is the 3rd pin used to inform the charger about which connector is plugged?

On the other hand,

• What type of connector is the common and placed on the other side*?

• male 10mm internal diameter, and with 3 symmetric pins
• female 10mm external diameter, 3 holes (2mm diameter)

• Can it be a mini XLR?

Answer 1

These are freely invented by whoever sells your specific universal power supply (not technically a charger, by the way).

There's no overarching standard for these namings (if there were, they'd rather have standardized the plugs, and that did not happen up until USB-C).

Answer 2

Is there any "official" list or convention for laptop connectors (pinout+voltage+current)?

No. The only "official" lists are international standards. There's no standard covering this, ergo no official list.

What about the M-x names in the picture? is it recognized as "standard"?

Not really, although in some markets it may be a de-facto "standard". Meaning: some manufacturer came up with this list. It took some effort. Now everyone copies the list because that takes least effort. That's how de-facto standards come into being :)

On the other hand, what connector is the common and 3 pins?

Not a standard either. Pin assignments are also arbitrary and specific to an application, although some contacts of the barrel connector may have higher current ratings than others, so it's not completely arbitrary if you need a high current DC connection.