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RE: Power Supplies
- To: <ukha_d@xxxxxxx>
- Subject: RE: Power Supplies
- From: "Steve Morgan" <steve@xxxxxxx>
- Date: Mon, 7 Jul 2003 22:14:53 +0100
- Mailing-list: list ukha_d@xxxxxxx; contact
ukha_d-owner@xxxxxxx
- Reply-to: ukha_d@xxxxxxx
-----Original Message-----
From: Phil Harris [mailto:phil@xxxxxxx]
>... it is always OK to use a *REGULATED* PSU in place of an unregulated
Is that strictly speaking true?
Someone knowing the theory better than I remember it may be able to
correct the bollox I'm about to come out with here, but...
IIRC, the voltage output from an unregulated supply is actually higher
than it's rating and varies with load. A device requiring, for example,
a 12V regulated supply could use an onboard 12V regulator and an
external 12V unregulated PSU. The onboard regulator (particularly a
linear regulator) has a voltage drop of it's own - that's why they get
hot, so to provide a 12V regulated output, you need at least 12V + the
regulator drop. With an unregulated supply, that's usually OK because
the actual voltage is higher. With a regulated supply, the output from
the device's regulator could well be too low - potentially causing
problems.
Steve
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