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Re: where can I find a universal *linear* laptop power supply?

From cameo <cameo@unreal.invalid>
Newsgroups comp.sys.laptops
Subject Re: where can I find a universal *linear* laptop power supply?
Date 2012-01-27 10:12 -0800
Organization A noiseless patient Spider
Message-ID <jfupc1$m3t$1@dont-email.me> (permalink)
References <jfs0hr$evo$1@dont-email.me> <jfsdpf$v6q$1@dont-email.me> <jftrov$ljc$1@dont-email.me>

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On 1/27/2012 1:44 AM, mike wrote:
> A linear power supply needs several things.
> A big/heavy transformer that runs at 50/60 Hz. line frequency.
> A big heat sink and or fan to dissipate the heat.
> You have to adjust the voltage so that at low line and maximum
> load, the trough voltage is higher than the output voltage by the
> headroom required by the regulator transistor. That means at high line
> you dissipate significant power in the pass transistor.
>
> The switcher uses high frequency, so the transformer and output filter
> can be MUCH smaller/lighter. The loss in the switching transistor is
> way less than in a linear circuit, so you don't need the big heatsink/fan.
>
> And since you can easily build a supply that runs from 90VAC to 260VAC,
> you need only one part number for worldwide application.

Thanks for that thorough explanation. Just one more thing: were 
switching transformers used for PC-s from the very beginning or they 
came some time later?

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Thread

where can I find a universal *linear* laptop power supply? "Harry Brown" <harrybrown@harrybrown.net> - 2012-01-26 11:55 -0500
  Re: where can I find a universal *linear* laptop power supply? mike <spamme9@gmail.com> - 2012-01-26 10:05 -0800
    Re: where can I find a universal *linear* laptop power supply? "Harry Brown" <harrybrown@harrybrown.net> - 2012-01-27 00:54 -0500
      Re: where can I find a universal *linear* laptop power supply? AaronJ <12465no-mail@no-mail.com> - 2012-01-27 00:55 -0700
      Re: where can I find a universal *linear* laptop power supply? mike <spamme9@gmail.com> - 2012-01-27 02:00 -0800
      Re: where can I find a universal *linear* laptop power supply? Salvador Freemanson <no@spam.com> - 2012-01-29 14:13 +0100
  Re: where can I find a universal *linear* laptop power supply? cameo <cameo@unreal.invalid> - 2012-01-26 12:42 -0800
    Re: where can I find a universal *linear* laptop power supply? mike <spamme9@gmail.com> - 2012-01-27 01:44 -0800
      Re: where can I find a universal *linear* laptop power supply? cameo <cameo@unreal.invalid> - 2012-01-27 10:12 -0800
        Re: where can I find a universal *linear* laptop power supply? mike <spamme9@gmail.com> - 2012-01-27 23:00 -0800
          Re: where can I find a universal *linear* laptop power supply? "BillW50" <BillW50@aol.kom> - 2012-01-28 08:01 -0600
          Re: where can I find a universal *linear* laptop power supply? Sjouke Burry <s@b> - 2012-01-28 17:19 +0000
            Re: where can I find a universal *linear* laptop power supply? Bob_Villa <pheeh.zero@gmail.com> - 2012-01-28 10:26 -0800
          Re: where can I find a universal *linear* laptop power supply? cameo <cameo@unreal.invalid> - 2012-01-28 19:28 -0800
        Re: where can I find a universal *linear* laptop power supply? Michael Black <et472@ncf.ca> - 2012-01-28 21:13 -0500
          Re: where can I find a universal *linear* laptop power supply? AaronJ <12333465no-mail@no-mail.com> - 2012-01-28 20:40 -0700
            Re: where can I find a universal *linear* laptop power supply? Bob_Villa <pheeh.zero@gmail.com> - 2012-01-28 20:34 -0800
              Re: where can I find a universal *linear* laptop power supply? mike <spamme9@gmail.com> - 2012-01-29 00:36 -0800
              Re: where can I find a universal *linear* laptop power supply? AaronJ <12333465no-mail@no-mail.com> - 2012-01-29 10:25 -0700
            Re: where can I find a universal *linear* laptop power supply? Michael Black <et472@ncf.ca> - 2012-01-29 10:25 -0500
              Re: where can I find a universal *linear* laptop power supply? AaronJ <12333465no-mail@no-mail.com> - 2012-01-29 10:03 -0700
        Re: where can I find a universal *linear* laptop power supply? davy <davy.573q95@no.email.invalid> - 2012-01-28 04:34 -0600

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