Electronic – Why do many laptops run on 19 volts

mobilepower supplyvoltage

Typically mobile devices that have a mains-powered supply will accept voltage that is multiple of some single battery voltage. For example, 4.5 volts is 1.5 volts (AA primary battery) 3 times and 36 volts is 3.6 volts (Li-Ion battery) 10 times.

Now there're laptops that use external power supplies rated at exactly 19 volts. That isn't a multiple of anything suitable. Puzzles me a lot.

Where does this voltage originate from?

Best Answer

The choice of 19 volts is because is it comfortably below 20 volts which is the maximum output voltage of power supplies that can be certified as LPS (Limited Power Source) with non-inherent power delivery limits.

If you can keep at or below 20 volts, the whole safety certification thing becomes easier and cheaper.

To make sure you're within the limit accounting for manufacturing tolerances, go 5% lower, which is 19 volts. There you are. It has nothing to do with battery pack organization or LCD screens.