Danjel McGougan (danjel.delete@this.mcgougan.se) on May 13, 2020 6:52 am wrote:
> David Kanter (dkanter.delete@this.realworldtech.com) on May 11, 2020 7:37 am wrote:
> > Friends, posters, and lurkers,
> >
> > Power delivery is one of the most significant challenges in modern processors. The power
> > delivery network (PDN) must meet the demanding requirements of modern CMOS technology,
> > supply power with excellent efficiency, and swiftly respond to changes in power draw.
> >
> > I just published a new post that goes into detail on power
> > delivery: https://www.realworldtech.com/power-delivery/
> >
> > It includes a brief discussion of system level power delivery, Intel's FIVR, and decoupling capacitors.
> >
> > As always, please take a look and comments/feedback/questions welcome here!
> >
> > David
> >
>
> Thank you for a great article!
>
> Just a minor nitpick:
>
> You mention lithium-ion batteries in laptops on page 2 and say that they output 3.7V DC.
> While it is true that an individual cell nominally outputs 3.7V, the battery pack of a
> typical laptop have multiple cells in series delivering a higher voltage. Typically there
> are 3 or 4 cells in series delivering ~11V or ~15V nominally from the battery pack.
>

Yup, and I guess that's why power bricks for laptops usually output 15V - 20V: so they can use the same step-down DC-DC converter for both wall and battery input. The similar voltage range means that you could efficiently use a single converter optimized for that range.

Or maybe 15-20V is just a convenient voltage on the safety vs power-loss tradeoff curve.