Re: [CAD_CAM_EDM_DRO] Not-so-off-topic: rectifiers

In a message dated 12-Jul-01 19:11:11 Central Daylight Time,
zephyrus@... writes:

> I did notice that on the too-enthusiastic linear supply I had, they used a
> dual secondary and a single diode on each one, instead of a single
> secondary and a bridge. I'm assuming that beefy single diodes are easier
> to come by than beefy bridges...
>

Possibly, but there are advantages AND disadvantages in doing a rectifier
with a center-tapped transformer and "just two diodes" over the "bridge
rectifier" lashup: The former requires that center-tap, possibly making the
transformer 29¢ more expensive, right there. Too, "half the copper is unused
half the time", something which one could at least consider an "economic
disadvantage". But you have only "one diode-loss" (about 0.6 volt) across
the one diode in which current is flowing at a time, whereas in a bridge, the
current always flows through TWO (series-connected) diodes, a voltage-waste,
and usually a "current waste", as well. The bridges may cost more than a
pair of "same current rating" diodes, but often any difference is
insignificant. The transformer cost, all else being equal, may be a tiny tad
more for the CT version. However, as "all the copper is used all the time",
the "bridge rectified transformer" might have to be a tad larger to
"qualify". I'm talking about 100 VA or less. Anything more than that, and
you are getting into currents and dissipations where some engineering
discipline (and academic smarts!) come into play. Have fun! Jan Rowland,
Troll



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