Mailinglist Archive: opensuse (1620 mails)

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Re: [opensuse] UPS : replacing battery with 12 volt Jelly Car Battery
On 11/25/2014 11:05 AM, Anton Aylward wrote:
On 11/25/2014 01:39 PM, Lew Wolfgang wrote:
On 11/25/2014 10:35 AM, Anton Aylward wrote:
On 11/25/2014 01:19 PM, Lew Wolfgang wrote:
The laptop will have small DC-to-DC converters and/or regulators to
develop the needed voltages. With 19-VDC from the wall-wart they've
got plenty of "headroom" to run their regulators. Note that there are
other voltages running around in there to power the CPU, which uses
something around 2.2-VDC I think.
19V to 2.2V is one hell of a drop!

Yup, that's why it's done with switching power supplies. Resistive
regulators would waste a lot of power.
Indeed, but it still leaves the question open.

The switcher for laptops is external, the power-brick or wall-wart.
I think that steps down with a transformer, then rectifies, then does
the capacitive filtering and stabilization so that the 19VDC is
delivered to the laptop. There is no switcher in the laptop that I can
see when I take mine apart, just regulator chips.

Are we getting confused between the needs of a laptop, specifically for
lightness, and the needs of a desktop/tower PC where the switcher is
inside the case?

I've been asking about the laptop use-case.

Right. But I don't think the laptop relies on the wall-wart for regulation.
They are
certainly switching power supplies because they can accept (usually) 120/240-VAC
at 50/60-Hz. You might not recognize a small switcher if its components were
connected directly to the motherboard. The transformers can be tiny because of
the relatively high (20-KHz?) frequencies. I remember some high-end desktop
motherboards where you could select CPU voltages in the Rom BIOS. This would
be for gaming over-clocking.


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