Tech Corner by George Hrischenko VE3DXG

A genuine full wave voltage doubler.
Forget what the ARRL says about full wave voltage doubling circuits. They have yet to publish a circuit for one! I wrote them 20 years ago and got a letter back saying In essence "yes, the circuits are two stacked half way rectifiers" but they have never changed their terminology. I think this is due to the fact that much of their theory was taken from Terman or Ghirardhi and they didn't want to offend these pundits.

This circuit came to my attention In an Issue of TCA at least four years ago, attributed to a Yugoslav HAM and I have never seen it since.

This circuit corrects the failings of the usual 'full wave doubler" rectifier circuits as to efficiency and ease of rectification. The output of this circuit is 120 Hz ripple instead of 60 Hz and the transformer utilization factor is double which means less transformer I²R losses or the use of a smaller transformer.

This circuit is more complex as you can see ---- it took me 2 years to unravel the original, uses one or two more capacitors and two more diodes. All components are very Inexpensive today so don't skimp on your ratings.

For an example - suppose you need 2600-2800 V @ 1 amp for a linear (2600 W pep input) you will need a transformer rated at 1000 Volts RMS secondary @ 2 A continuous service (2 KW in). The diodes should each have a rating of 2X input for PIV and 1A min current or 2 kV PIV @ 1A minimum. The cap's marked Cl should be rated at least 1.4X input or 1500V working (2000V would be better). Each Cl should have twice the capacity of cout for a linear 35-50 uF @ 2kV would suffice. Cout will then be rated at 20-25 uF @4 KV minimum.

This circuit can be operated off the AC line 120 or 230 V). BUT the negative ground must be left floating since one side of the line Is grounded and YOU CANNOT ground both the Input and the NEG (or POS) DC or else B O O M!

Enjoy!  George VE3DGX

originally printed in the York Region ARC newsletter SPLATTER