Mailinglist Archive: opensuse (1620 mails)

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Re: [opensuse] UPS : replacing battery with 12 volt Jelly Car Battery
On 11/25/2014 02:05 PM, Anton Aylward wrote:
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.

There is also a switching power supply within the computer. It's what
takes the adapter/battery voltage and converts it to what's needed.
Also, with switching supplies, the AC is not stepped down. It's
rectified to provide high voltage DC that's used to run a power
oscillator. The output of that oscillator is at a much higher frequency
than the power line. This permits the use of a much smaller and lighter
transformer than could be used at power line frequencies. The output of
the transformer is rectified. Then, there's a switching regulator,
controlled by the output voltage that takes the output of the rectifier
and converts it to the desired voltage. It does this by conducting only
long enough to maintain the desired voltage on a capacitor connected at
the output. It is possible that the rectifying and switching are done
in the same device.

Here's an article that provides a better explanation than I can here.
https://en.wikipedia.org/wiki/Switched-mode_power_supply
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.

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