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In Reply to: RE: Dual B+ froma a CT tranny? posted by jorisdallaire on October 17, 2014 at 14:21:52
This has been known as an "economy" supply going back more than 40 years. If you need two voltages with a common ground from one CT transformer, the circuit above is what you want. The voltage at E1 will be the same as that of a full wave rectifier; the voltage at E2 will be that of a full wave bridge. Total DC power available from the transformer is of course the same as when it's used in a normal manner.
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Buy Chinese. Bury freedom.
Edits: 10/18/14 10/18/14Follow Ups:
Example of the Ecconomy Supply.
An Aussie Guitar Amp, the 1/2 B+ used for output tube screens:
http://www.ozvalveamps.org/goldentone/goldentone1746-40wbm1963rdw.gif
Note the use of TV Line Output Tubes and hence the need for the 2nd B+ at 1/2 voltage. This amps says 40W but a pair of 6DQ6A will give 60 Watts easily.
Cheers,
Ian
Did a search with "Economy supply" and found this interesting site that you may already know of.
That's a nice link. I've never seen the version with the doubler. I have a use for that exact thing in an upcoming project!EDIT: I just ran this through SPICE, and the six-diode doubler really works well. The output capacitor receives a recharge pulse twice as frequently as in a standard full wave doubler, and each pulse is half the usual current (for a given load). Very nice!
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Buy Chinese. Bury freedom.
Edits: 10/20/14 10/20/14 10/20/14
... let us know how it turns out if you build it. I think such a topology can serve the community if it sounds good. The current requirements on the tranny and bridge are severe...
Regards,
Joris
"The current requirements on the tranny and bridge are severe..."
That's what the author of the article said too, but my SPICE model didn't agree. Peak secondary current in the six-diode doubler was almost identical to that in a two-diode (full wave) doubler. Maybe the author was referring to the dual output version ("4x8"). I'll look at it again when I get home from work today.
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Buy Chinese. Bury freedom.
Yes I was referring to the requirements the "4x8" imposes on the tranny and bridge. In that configuration, D7 and D8 of the doubler are replaced by D3 and D4 of the bridge rectifier, which loads them hard since they must supply current for the other voltage rail as well.
I dodn't realize you wanted to use the doubler independently - my apologies.
Here's a second means that I designed myself about 15 years ago. It outputs two voltages by attaching a choke-input filter and cap-input filter to the same rectifier. Note that the choke must be critical value, otherwise the low voltage section will charge up to the same peak value as the high voltage.
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Buy Chinese. Bury freedom.
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