- Joined Jun 1, 2021
Laptops need about 19v, desktops need 12v.
Only on the primary side of the mains transformer. 220 RMS gets you 311 volts peak. The only way there would be a 300+ volt DC rail is if the desktop used an offline supply, but there is no real reason for doing that.What??
Where the heck would it use such a high voltage?
Do you have one that runs on tubes?
No. Looking at it your way, Laptops need 19 Volts DC, Desktops 220 / 110 Volts AC.Laptops need about 19v, desktops need 12v.
I disagree. In both cases a higher voltage is used to generate the voltages actually used, and there is good reason for this, using buck converters instead of boost.Given the TS's obvious lack of knowledge about small computer power systems, this statement is intentionally misleading, serves no useful purpose, and creates an unnecessary distraction in the thread.
I disagree. In both cases a higher voltage is used to generate the voltages actually used, and there is good reason for this, using buck converters instead of boost.
My read of post #1 is that the TS is asking about motherboard voltages, as if the circuits in a laptop run off of the 19 V supply directly, without additional voltage conversion. He already knows that something converts 240 Vac powerline to +12 Vdc, the largest circuit board operating voltage that he knows of. In that context, throwing around numbers like 300 V with zero explanation about how they differ from what he is asking about is showboating.desktops need 12v.
Power supply Output rails - he specifically mentioned 19 and 12VDC. Stop justifying a 300v answer - read the OPs question - he never asked about "rails" in his original question or the internal workings of a mains to dc power supply - he only uses the word rails associated with a 12VDC output of a desktop supply when he tries to clarify to your ridiculous comment in post 2. And no, modern (less than 20 years) Mobile PCs don't use 12VDC anywhere as far as I've seen. All the dc input to charge batteries is 19 to 21v and internal modules use 5v, 3.3v or lower for some cpus.TS never mentioned anything about motherboards, in post #3 he talks about rails.
Not wrong at all. That's exactly why I say MORE than 300V in my post. Better than -ish.
Interesting... I learned something today!! Unfortunately I'll never have a use for it other than another tidbit of trivial knowledge. Maybe one day I'll learn and understand how they work, but for now I'm just happy to know what comes out and what I can do with it.Yes.
Yes.Just out of curiosity what happens if you are only on a 120V mains? Will you still get the 300V or better?
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