Wes Stewart wrote:
On Fri, 18 Nov 2005 23:06:03 -0500, John Popelish
wrote:


Ken Scharf wrote:

I was looking at some power supply circuits for
tube linears and was thinking about the full wave
voltage doubler. This is basicly two half wave
rectifiers in series. Now I could build this
circuit with a choke input filter for each half
wave rectifier of the voltage doubler, and I could
put the chokes in the lead without the rectifier.
In this case I could use one choke for both halfs
of the voltage doubler. The output should then
be about .9 * rms input voltage * 2
or 1.8 times the rms voltage of the transformer.

Has anybody ever tried this?

------|--------
) | |
) | ---
) | ---
)-----^^^^^^----|
| |
| ---
| ---
|--|--------|

Crude schematic showing transformer secondary
diodes filter choke and capacitors.

If the choke is directly in series with the transformer, it will have
to pass AC, and that won't provide normal choke input filtering (which
steadies the DC current after the rectifier), but just puts an
impedance between the transformer and the doubler.


All chokes are in series with the transformer and pass some AC
component. If they only passed DC we would need them.

I was using DC in the "unidirectional current" sense, not the "having
no AC components" sense.

Without giving this too much (likely enought) thought I think this
will fail because without loads across -each- filter cap, the critical
inductance will not be obtained.

Regardless of the loads across the caps, this inductor cannot ever
achieve critical inductance, since that is the inductance that keeps
the current reaching zero, each half cycle. In this circuit, the
inductor precedes the rectifiers, so its current must pass through
zero twice per cycle, regardless of the capacitor load.

You could also put it in series with the primary, instead, and achieve
the same effect (with the proper scaling to account for the turns ratio).

There may be a way to incorporate an inductor into a doubler, but I
don't think this is it.