About laptops voltage - why not 5V ?

[tempt6]

Hi all,

I see most laptops running with about 9v - 12v, while every phone needs a 5v charger. So i was just wondering if it's a matter of old habits and noone cares about making PCs that need 5v (in order to reduce the amount of chargers), or if the overall components can't make it below 9v

Have a nice day

 

[kawininjazx]

Most laptops run off of 19V, 5V is not enough to power it. Phones have low voltage SoC systems, they are much simpler than a full PC.

 

[rusabus]

It comes down to power delivery. Most laptop chargers are 19 to 20 volts, not 9 to 12. The higher voltage allows them to deliver more power using thinner cables and smaller connectors than would be required at lower voltage. For example, I've got a high-end laptop that has a 170-watt power supply. At 19 volts, that power supply puts out about 9 amps of current. In order to handle 9 amps, the cables need to be a certain thickness and the connectors need to have a certain amount of contact area. If it were running at 5 volts, to supply 170 watts, it'd need cables and connectors that could handle 34 amps. Those cables and connectors would have to be really thick to handle that, and it would be difficult to produce a connector that was thin enough to fit nicely in a laptop that could handle that much current.

Phones typically charge over USB cables, which prior to USB 3 were limited to 5 volts and roughly 2 amps, for a maximum of about 10 watts of charging power. USB 3 increases that to 3 amps, but at 5 volts, that still only gives you 15 watts of charging power. USB type C introduces a new "power delivery" standard that can deliver up to 100 watts of power, but to do this, it increases the voltage from 5 volts to 20. For most laptops, 100 watts is plenty for charging, so USB type C truly could become a universal standard between phone and laptop chargers for most laptops.

 

[tempt6]

Oops yeah i meant 19V instead of 9V, brainfart sorry, so as for the 12v i must've thought there's higher than 9v...
The cables thickness makes sense (now remembering P=RI²), thanks