External Power Supply Standard

Consider the process of supplying power to the average computer. Mains voltage goes into a UPS where it is converted to 12V, then converted back to mains voltage before being converted to 12V, 5V, and 3.3V. Doesn't that seem like a total waste of at least one step? (Granted, that's a bit of a simplification of how most UPSes work, but it's close enough for most purposes.)

There's really no good reason for power supplies to be inside the computer case anymore. The UPS already converts mains voltage to 12V, so at the very least that output should simply be fed into the computer case, where it is converted to whatever voltages are necessary. The problem is quite simple technically, but the trouble is getting everyone to agree on a standard. So I'm proposing one.

Both computers and (external) power supplies would have a "power class" rating from 1 to 3:

Class 1 computers would accept mains voltage, and class 1 power supplies would basically be, well, an outlet. A standard UPS that supplies mains voltage would also be a class 1 power supply (but with battery backup). Class 1 is pretty much the way things are now.

Class 2 computers would accept 12V, and convert it internally to any other required voltages. Class 2 power supplies would supply 12V. Optionally, class 2 connectors can support (but are not required to have) a data connection such as USB, for communicating information such as battery status, power draw, temperature, and so forth. Class 2 would really be a transitional class, so that existing UPS and computer designs could be tweaked to simply eliminate a single step on each side. The key thing is that to meet the class 2 standard, any given device would have to use a standardized connector.

Class 3 computers would accept a connector that carries 12V, 5V, and 3.3V, along with a mandatory data connection. Class 3 power supplies would similarly provide these voltages plus the data line. The data connection would be required to be able to talk to multiple systems at once, as under the standard one power supply could be used to power multiple computers. Additionally, class 3 computers could be able to (but are not required to) accept multiple power supplies, for redundancy or load distribution purposes. Again, to meet the standard a standardized connector would have to be used on all equipment.

The various power classes would not be compatible with each other in any way, but any device could be certified for multiple power classes. For example, a UPS that provided both mains voltage and 12V with a data connection would be certified as power class 1/2. As long as the power supply and computer have at least one matching power class, you can be certain that they will work with each other.