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- Newsgroups: sci.electronics
- Path: sparky!uunet!infonode!ingr!b30news!catbyte!medin
- From: medin@catbyte.b30.ingr.com (Dave Medin)
- Subject: Re: 12 V -> 3V, 0.6 A
- Message-ID: <1992Nov11.175614.14676@b30.ingr.com>
- Sender: medin@catbyte (Dave Medin)
- Reply-To: medin@catbyte.b30.ingr.com
- Organization: Intergraph Corporation, Huntsville AL
- References: <1992Nov9.231617.28042@b30.ingr.com> <1992Nov10.161358.5509@ms.uky.edu> <d1temp.721464879@dtek.chalmers.se>
- Date: Wed, 11 Nov 1992 17:56:14 GMT
- Lines: 37
-
- In article <d1temp.721464879@dtek.chalmers.se>, d1temp@dtek.chalmers.se (Michael Tempsch) writes:
- |> msunde01@mik.uky.edu (Mark Underwood) writes:
- |>
- |> Ever looked inside one of the original converters?
- |> I have one, it has 7 1N4001 diodes i series... (the CD wants 5-7 V in)
-
- The poster's player needed 3 volts, though, and the rules are different
- because the battery voltage is so low. Accuracy becomes much more important
-
- |> Most batteryoperated devices aren't that touchy about input voltage,
- |> there is a small ;-} difference in battery voltage between fresh batteries
- |> at standby and almost dead at full output...
-
- When the operating voltage gets lower, the device gets much more touchy
- as there is little voltage headroom, thus internal regulators are usually
- omitted or have very little gain and the device relies upon the relatively
- stable battery output voltage over its life. The non-regulated diode
- voltage dropper becomes a hit and miss proposition as the voltage
- drops of the diodes over the current range of the adapter are hard
- to predict. They are not a rock-steady 0.7 volts. Another problem, noted
- by another poster, was that the car battery voltage varies quite a bit
- (engine on, high RPM, engine off, load dump spikes). With a diode
- dropper, these differences are passed on DIRECTLY rather than proportionally
- or not at all. A regulator, for the the additional $1 US, is thus worth
- it...
-
- --
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