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22

"A system power supply has absolutely no intelligent electronics." – I don't think that's true. It wouldn't surprise me if a system power supply had more processing power than the Apollo 11 computer system(s). It does however have no way to communicate with the devices.
– Jörg W Mittag
Commented Apr 22, 2017 at 2:10
31

The reason why USB is even able to negotiate power is that it is, at its core, a communications protocol, not a power delivery protocol. It works because additional power may or may not be available. A switch-mode or linear power supply will have some safe limit above which it cannot provide more power, and this amount of power corresponds to some particular current at a particular voltage. Your power company is more similar to the computer power supply than to USB; your appliances don't negotitate for additional power, but the power company detects the additional draw and compensates.
– user
Commented Apr 22, 2017 at 13:15
20

Actually, even a modern ATX psu has little to no digital parts inside, let alone a microprocessor. It would be of no use, so there's none. Fault conditions are so fast that they must be handled in the analog world. And the Apollo definitely had more computing power than your average PSU.
– Vladimir Cravero
Commented Apr 24, 2017 at 7:38
5

@whatsisname I am sorry, but what you say either isn't true or does not make sense. uC are cheap, but fast ADC and DACs are not. High efficiency is not achieved via digital control at all, power factor correction can be done with one capacitor. If you do not believe me, just open an ATX psu. And yeah, I just happen to work in the semiconductor industry, on... power chips. Please, do not spread inaccurate information.
– Vladimir Cravero
Commented Apr 25, 2017 at 4:57
2

@whatsisname microcontrollers might be cheap, but in a highly competitive market every penny counts and if you don't have to use it you don't. Newer SMPS units might have fancy FET based overcurrent protection, but there is no way a microcontroller is necessary when a much simpler (cheaper) and more dedicated piece of silicon can be used. Using dedicated silicon is also cheaper than using a controller that needs someone to write software for it, and SMPS unit simply don't need an intelligent controller.
– Mokubai ♦
Commented Apr 25, 2017 at 6:13

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